WO2019189670A1 - 非水系電解液及び非水系電解液電池 - Google Patents
非水系電解液及び非水系電解液電池 Download PDFInfo
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- WO2019189670A1 WO2019189670A1 PCT/JP2019/013815 JP2019013815W WO2019189670A1 WO 2019189670 A1 WO2019189670 A1 WO 2019189670A1 JP 2019013815 W JP2019013815 W JP 2019013815W WO 2019189670 A1 WO2019189670 A1 WO 2019189670A1
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- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
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- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte battery, and more particularly to a non-aqueous electrolyte containing a specific amount of a specific compound and a non-aqueous electrolyte battery using the non-aqueous electrolyte.
- non-aqueous electrolyte batteries such as lithium secondary batteries have been put to practical use in applications for driving on-vehicle power supplies such as electric vehicles.
- Patent Document 1 discloses a study for improving the capacity maintenance rate in a cycle test by incorporating a sulfonate compound and a compound having two or more unsaturated bonds at the terminal into a non-aqueous electrolyte solution.
- Patent Document 2 discloses that a non-aqueous electrolyte contains a specific phosphite compound and a compound having one polymerizable functional group in the molecule, thereby improving the capacity retention rate in the cycle test and the electrolyte solution.
- a study for improving flame retardancy is disclosed.
- Patent Document 3 by combining a positive electrode containing a certain amount of moisture with a non-aqueous electrolyte containing an isocyanate compound and an imide salt, the isocyanate compound reduces the moisture in the positive electrode, and isocyanate. Studies have been made to improve the capacity retention rate and battery swell in a cycle test by forming a film suitable for a negative electrode with a narate compound and an imide salt. Patent Document 4 discloses a study for improving battery swelling in an 85 ° C. storage test by including a specific isocyanate compound in a non-aqueous electrolyte solution.
- the present inventor contains a compound represented by the general formula (A) and a cyclic carbonate having a carbon-carbon unsaturated bond, and further includes the general formula (B) and the general formula.
- a non-aqueous electrolyte containing at least one compound selected from the group consisting of the compounds represented by (C) and suitably adjusting the amount of addition of these compounds suppression of gas generation during high-temperature storage
- the present inventors have found that an increase in battery resistance can be suppressed, and have reached the present invention.
- the present invention provides specific embodiments shown in [1] to [8] below.
- [1] Selected from the group consisting of a compound represented by the following general formula (A), a cyclic carbonate having a carbon-carbon unsaturated bond, and a compound represented by the following general formula (B) and the following general formula (C)
- a non-aqueous electrolyte solution containing at least one kind of compound The content of the cyclic carbonate having a carbon-carbon unsaturated bond with respect to the whole non-aqueous electrolyte is 0.01% by mass or more and 1.5% by mass or less, When only one of the compounds represented by the general formula (B) and the general formula (C) is contained, the non-aqueous system of the compound represented by the general formula (B) or the general formula (C) The content with respect to the entire electrolytic solution is 0.01 mass% or more and 0.49 mass% or less, When both of the compound represented by the general formula (B) and the general formula (C) are contained, the non-aque
- R 1 to R 3 may be the same as or different from each other, and are optionally substituted hydrocarbon groups having 1 to 10 carbon atoms, provided that R 1 At least one of 1 to R 3 is a hydrocarbon group having a carbon-carbon unsaturated bond.
- Q is a hydrocarbon group having 3 to 20 carbon atoms, and the hydrocarbon group has a cycloalkylene group.
- a non-aqueous electrolyte battery comprising a positive electrode and a negative electrode capable of inserting and extracting metal ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is any one of [1] to [6] A non-aqueous electrolyte battery which is a non-aqueous electrolyte solution.
- M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.
- the metal particles that can be alloyed with Li are metal particles containing at least one metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn, and W.
- Non-aqueous electrolyte battery are Si or Si metal oxide.
- the negative electrode active material containing metal particles that can be alloyed with Li and graphite is a composite and / or mixture of metal particles and graphite particles.
- the non-aqueous electrolyte battery described in 1. [13] The content of the metal particles that can be alloyed with Li with respect to the total of the negative electrode active material containing the metal particles that can be alloyed with Li and graphite is 0.1% by mass or more and 25% by mass or less.
- the nonaqueous electrolyte battery according to any one of [9] to [12].
- non-aqueous electrolyte of the present invention not only suppression of gas generation during high-temperature storage but also non-aqueous electrolyte that can suppress an increase in battery resistance of the non-aqueous electrolyte battery (hereinafter simply referred to as battery resistance). A battery can be obtained.
- Non-aqueous electrolyte ⁇ 1-1.
- Compound represented by formula (A)> The non-aqueous electrolyte solution of the present invention contains a compound represented by the following general formula (A).
- n each independently represents an integer of 1 to 3.
- (M, n) (1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3 2), (3, 3).
- the compounds represented by the general formula (A) may be used singly or in combination of two or more in any combination and ratio. Further, the content of the compound represented by the general formula (A) with respect to the entire non-aqueous electrolyte of the present invention is not particularly limited, and may be arbitrary as long as the effects of the present invention are not significantly impaired. In mass%, it is usually 0.001 mass% or more, preferably 0.01 mass% or more, more preferably 0.1 mass% or more, and usually 5 mass% or less, preferably 4 mass% or less, more preferably Is 3% by mass or less, particularly preferably 2% by mass or less. Within this range, an increase in battery resistance can be suitably suppressed during high temperature storage. When two or more compounds represented by the general formula (A) are used in combination, the total amount of the compounds represented by the general formula (A) may be set to satisfy the above range.
- Cyclic carbonate compound having carbon-carbon unsaturated bond The cyclic carbonate having a carbon-carbon unsaturated bond (hereinafter sometimes referred to as “unsaturated cyclic carbonate”) contained in the nonaqueous electrolytic solution of the present invention includes a carbon-carbon double bond or carbon-carbon. Any cyclic carbonate having a triple bond is not particularly limited, and any unsaturated carbonate can be used. The cyclic carbonate having an aromatic ring is also included in the unsaturated cyclic carbonate.
- unsaturated cyclic carbonates include vinylene carbonates; ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond; cyclic carbonates having a phenyl group; having a vinyl group Cyclic carbonates; cyclic carbonates having an allyl group; cyclic carbonates having a catechol group.
- vinylene carbonates ethylene carbonates having a vinyl group, ethylene carbonates having an allyl group, and ethylene carbonates having a phenyl group.
- vinylene carbonates Vinylene carbonate, methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, 4,5-divinyl vinylene carbonate, allyl vinylene carbonate, 4,5-diallyl vinylene carbonate 4-fluoro vinylene carbonate, 4-fluoro-5-methyl vinylene carbonate, 4-fluoro-5-phenyl vinylene carbonate, 4-fluoro-5-vinyl vinylene carbonate, 4-allyl-5-fluoro vinylene carbonate, etc. .
- ethylene carbonates substituted with a substituent having an aromatic ring, a carbon-carbon double bond or a carbon-carbon triple bond include: Vinylethylene carbonate, 4,5-divinylethylene carbonate, 4-methyl-5-vinylethylene carbonate, 4-allyl-5-vinylethylene carbonate, ethynylethylene carbonate, 4,5-diethynylethylene carbonate, 4-methyl-5 -Ethynylethylene carbonate, 4-vinyl-5-ethynylethylene carbonate, 4-allyl-5-ethynylethylene carbonate, phenylethylene carbonate, 4,5-diphenylethylene carbonate, 4-phenyl-5-vinylethylene carbonate, 4-allyl -5-phenylethylene carbonate, allylethylene carbonate, 4,5-diallylethylene carbonate, 4-methyl-5-allylethylene carbonate and the like.
- the molecular weight of the unsaturated cyclic carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the molecular weight is preferably 80 or more and 250 or less. If it is this range, it will be easy to ensure the solubility of the unsaturated cyclic carbonate with respect to a non-aqueous electrolyte solution, and the effect of this invention will fully be expressed easily.
- the molecular weight of the unsaturated cyclic carbonate is more preferably 85 or more, and more preferably 150 or less.
- the production method of the unsaturated cyclic carbonate is not particularly limited, and can be produced by arbitrarily selecting a known method. Moreover, you may obtain and use a commercial item.
- Unsaturated cyclic carbonates may be used alone or in combination of two or more in any combination and ratio. Further, the content of the unsaturated cyclic carbonate with respect to the whole non-aqueous electrolyte solution of the present invention is 0.01% by mass or more, more preferably 0.1% by mass or more, in 100% by mass of the non-aqueous electrolyte solution. It is 1.5% by mass or less, preferably 1.4% by mass or less, more preferably 1.3% by mass or less, and particularly preferably 1.25% by mass or less. Within this range, it is easy to avoid a situation in which battery resistance increases during high temperature storage. When two or more unsaturated cyclic carbonates are used in combination, the total amount of unsaturated cyclic carbonates may be set to satisfy the above range.
- the non-aqueous electrolyte solution of the present invention contains at least one compound selected from the group consisting of compounds represented by the following general formula (B) and a general formula (C) described later.
- R 1 to R 3 may be the same or different from each other, and may be a hydrocarbon group having 1 to 10 carbon atoms which may have a substituent. However, at least one of R 1 to R 3 is a hydrocarbon group having a carbon-carbon unsaturated bond.
- examples of the substituent include a cyano group, an isocyanato group, an acyl group (— (C ⁇ O) —Ra), an acyloxy group (—O (C ⁇ O) —Ra), an alkoxycarbonyl group (— (C ⁇ O) O—Ra), sulfonyl group (—SO 2 —Ra), sulfonyloxy group (—O (SO 2 ) —Ra), alkoxysulfonyl group (— (SO 2 ) —O—Ra), alkoxycarbonyloxy group (—O— (C ⁇ O) —O—Ra), ether group (—O—Ra), acrylic group, methacryl group, halogen (preferably fluorine), trifluoromethyl group and the like can be mentioned.
- Ra represents an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms.
- a cyano group, an isocyanato group, an acyloxy group (—O (C ⁇ O) —Ra), an alkoxycarbonyl group (— (C ⁇ O) O—Ra), a sulfonyl group (—SO 2 ) are preferable.
- hydrocarbon group examples include an aryl group optionally via an alkyl group, a cycloalkyl group, an alkenyl group, an alkynyl group, or an alkylene group.
- an alkyl group, an alkenyl group or an alkynyl group is preferable, an alkenyl group or an alkynyl group is more preferable, and an alkenyl group is particularly preferable.
- alkyl group examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-pentyl group, Examples thereof include t-amyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and the like.
- an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, or a hexyl group is preferable, and an ethyl group, an n-propyl group, or an n-butyl group is more preferable.
- cycloalkyl group examples include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantyl group, and the like, and a cyclohexyl group or an adamantyl group is preferable.
- alkenyl group examples include a vinyl group, an allyl group, a methallyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, a 3-butenyl group, and a 4-pentenyl group.
- a vinyl group, an allyl group, a methallyl group, or a 2-butenyl group is preferable, a vinyl group, an allyl group, or a methallyl group is more preferable, and an allyl group or a methallyl group is most preferable.
- An allyl group is preferred.
- the hydrocarbon group is such an alkenyl group, the steric hindrance is appropriate, and it can be adjusted to a suitable extent that the compound of the general formula (B) reacts on the electrode to increase the electrode resistance. is there.
- alkynyl group examples include ethynyl group, 2-propynyl group, 2-butynyl group, 3-butynyl group, 4-pentynyl group, 5-hexynyl group and the like.
- preferred is an ethynyl group, 2-propynyl group, 2-butynyl group or 3-butynyl group, more preferred is a 2-propynyl group or 3-butynyl group, and particularly preferred is a 2-propynyl group.
- the hydrocarbon group is such an alkynyl group, the steric hindrance is appropriate, and it can be adjusted to a suitable extent that the compound of the general formula (B) reacts on the electrode to increase the electrode resistance. is there.
- R 1 to R 3 are preferably an alkyl group, an allyl group or a methallyl group which may have a substituent, and an allyl group is most preferable from the viewpoint of film forming ability.
- the hydrocarbon group having a carbon-carbon unsaturated bond may have a carbon-carbon unsaturated bond as a substituent, and preferably includes a group having a carbon-carbon unsaturated bond at the terminal, more preferably It contains at least one selected from the group consisting of an allyl group, a methallyl group and a butenyl group, more preferably an allyl group or a methallyl group.
- Specific examples of the compound represented by the general formula (B) used in the present invention include compounds having the following structure.
- a compound having the following structure is preferable.
- the content of the compound represented by the general formula (B) with respect to the entire non-aqueous electrolyte solution of the present invention is such that the non-aqueous electrolyte solution does not contain the compound represented by the general formula (C) described later.
- 100% by mass 0.01% by mass or more, preferably 0.05% by mass or more, and 0.49% by mass or less, preferably 0.40% by mass or less, more preferably 0.30% by mass or less. More preferably, it is 0.25% by mass or less, particularly preferably 0.20% by mass or less.
- the non-aqueous electrolyte solution of the present invention contains at least one compound selected from the group consisting of compounds represented by the general formula (B) and the following general formula (C).
- Q is a hydrocarbon group having 3 to 20 carbon atoms, and the hydrocarbon group has a cycloalkylene group.
- cycloalkylene group examples include a cyclopropylene group, a cyclobutylene group, a cyclopentine group, a cyclohexylene group, and the like. Of these, a cyclohexylene group is preferable.
- a part of hydrogen atoms of the hydrocarbon group having 3 to 20 carbon atoms may be substituted with a halogen atom.
- a fluorine atom is preferable from the viewpoint of increasing the reactivity on the negative electrode surface.
- Specific examples of the compound represented by the general formula (C) used in the present invention include compounds having the following structure.
- the content of the compound represented by the general formula (C) with respect to the entire non-aqueous electrolyte solution of the present invention is 100 masses when the non-aqueous electrolyte solution does not include the compound represented by the general formula (B). %, 0.01 mass% or more, preferably 0.05 mass% or more, and 0.49 mass% or less, preferably 0.40 mass% or less, more preferably 0.30 mass% or less, Preferably it is 0.25 mass% or less, Most preferably, it is 0.20 mass% or less.
- the non-aqueous electrolyte of the present invention contains both the compound represented by the general formula (B) and the compound represented by the general formula (C), the general formula (B) for the entire non-aqueous electrolyte of the present invention
- the content of the compound represented by the general formula (C) and the compound represented is 0.01% by mass or more, preferably 0.05% by mass or more, more preferably in 100% by mass of the nonaqueous electrolytic solution.
- the compound represented by the general formula (A) and the cyclic carbonate having a carbon-carbon unsaturated bond electrochemically react with the negative electrode during the initial charge, and the decomposition reaction proceeds. Since the compound represented by the general formula (B) and / or (C) has two or more sites that react with these reduction decomposition products in the structure, the compound represented by the general formula (A) on the negative electrode, A composite film comprising a cyclic carbonate having a carbon-carbon unsaturated bond and a compound represented by the general formula (B) and / or (C) is formed. Since this film has high insulation at high temperatures, side reactions at the negative electrode during high temperature storage are suppressed, and gas generation is suppressed.
- the reaction between the reductive decomposition product of the cyclic carbonate having a carbon-carbon unsaturated bond and the compound represented by the general formula (B) and / or (C) does not proceed sufficiently at the initial charge, it is stored at a high temperature. In some cases, the reaction between the reductive decomposition product and the compound represented by the general formula (B) and / or (C) proceeds excessively, resulting in an increase in battery resistance.
- the present invention suitably adjusts the addition amount of the cyclic carbonate having a carbon-carbon unsaturated bond and the compound represented by the general formula (B) and / or (C).
- part which the compound represented by general formula (B) and (C) has has a different reactive species, respectively.
- the compound represented by the general formula (B) reacts with a radical species generated by reductive decomposition of a cyclic carbonate having a carbon-carbon unsaturated bond
- the compound represented by the general formula (C) reacts with an anionic species.
- the nonaqueous electrolytic solution of the present invention preferably further contains a cyclic carbonate having a fluorine atom.
- the cyclic carbonate having a fluorine atom include a fluorinated product of a cyclic carbonate having an alkylene group having 2 to 6 carbon atoms and derivatives thereof, and examples thereof include a fluorinated product of ethylene carbonate and derivatives thereof.
- the derivatives of fluorinated ethylene carbonate include fluorinated ethylene carbonate substituted with an alkyl group (for example, an alkyl group having 1 to 4 carbon atoms). Of these, ethylene carbonate having 1 to 8 fluorine atoms and derivatives thereof are preferred.
- At least one selected from the group consisting of monofluoroethylene carbonate, 4,4-difluoroethylene carbonate, and 4,5-difluoroethylene carbonate provides high ionic conductivity and forms a suitable interface protective film. And more preferable.
- One cyclic carbonate compound having a fluorine atom may be used alone, or two or more cyclic carbonate compounds may be used in any combination and ratio.
- cyclic carbonate compound having a fluorine atom one kind may be used alone, or two kinds or more may be used in optional combination and ratio.
- % Or less preferably 30.0% by mass or less, more preferably 20.0% by mass or less, and still more preferably 10.0% by mass or less.
- the total amount of cyclic carbonate compounds having fluorine atoms may be set to satisfy the above range.
- the nonaqueous electrolytic solution of the present invention preferably further contains at least one salt selected from the group consisting of fluorinated salts and oxalate salts.
- the fluorinated salt that can be used in the non-aqueous electrolyte of the present invention is not particularly limited, but has a highly detachable fluorine atom in the structure. For example, it is represented by the general formula (A).
- the compound to be reacted with an anion (nucleophilic species) generated by a reduction reaction can form a composite film, it has difluorophosphate, fluorosulfonate, and bisfluorosulfonylimide structures. Salts are preferred. Difluorophosphates and fluorosulfonates are more preferred because of their particularly high fluorine atom releasability and favorable reaction with nucleophilic species.
- these various salts will be described.
- Difluorophosphate is not particularly limited, but lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, barium, and NR 13 R 14 R 15 R 16 (wherein R 13 to R 16 Each independently represents a hydrogen atom or an organic group having 1 to 12 carbon atoms).
- the organic group having 1 to 12 carbon atoms represented by R 13 to R 16 of ammonium is not particularly limited. Examples thereof include an cycloalkyl group which may be substituted, an aryl group which may be substituted with a halogen atom or an alkyl group, and a nitrogen atom-containing heterocyclic group which may have a substituent.
- R 13 to R 16 are preferably each independently a hydrogen atom, an alkyl group, a cycloalkyl group, or a nitrogen atom-containing heterocyclic group.
- difluorophosphate examples include lithium difluorophosphate, sodium difluorophosphate, and potassium difluorophosphate, and lithium difluorophosphate is preferred.
- Difluorophosphate may be used alone or in combination of two or more in any combination and ratio. Moreover, the compounding quantity of a difluorophosphate is not restrict
- the content of difluorophosphate with respect to the entire non-aqueous electrolyte solution of the present invention is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% in 100% by mass of the non-aqueous electrolyte solution. It is usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and most preferably 1% by mass or less.
- the total amount of difluorophosphate may be set to satisfy the above range.
- Fluorosulfonate The counter cation of the fluorosulfonate is the same as that of the difluorophosphate.
- fluorosulfonate examples thereof include lithium fluorosulfonate, sodium fluorosulfonate, potassium fluorosulfonate, rubidium fluorosulfonate, cesium fluorosulfonate, and the like, and lithium fluorosulfonate is preferable.
- a fluorosulfonate may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Further, the content of the fluorosulfonate with respect to the whole non-aqueous electrolyte solution of the present invention is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0 in 100% by mass of the non-aqueous electrolyte solution. 0.1% by mass or more, usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and most preferably 1% by mass or less.
- the total amount of fluorosulfonate may be set to satisfy the above range. If it is in this range, the swelling of the non-aqueous electrolyte battery accompanying charging / discharging can be suppressed suitably.
- Salt having bisfluorosulfonylimide structure >> The counter cation of the salt having a bisfluorosulfonylimide structure is the same as that of the difluorophosphate.
- a salt having a bisfluorosulfonylimide structure examples thereof include lithium bisfluorosulfonylimide, sodium bisfluorosulfonylimide, and potassium bisfluorosulfonylimide, and lithium bisfluorosulfonylimide is preferable.
- the content of the salt having a bisfluorosulfonylimide structure with respect to the whole non-aqueous electrolyte solution of the present invention is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably in 100% by mass of the non-aqueous electrolyte solution. Is 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.
- the total amount of salts having a bisfluorosulfonylimide structure may be set to satisfy the above range. If it is in this range, the swelling of the non-aqueous electrolyte battery accompanying charging / discharging can be suppressed suitably.
- Oxalato salt > The counter cation of the oxalate salt is the same as that of the difluorophosphate.
- oxalate salts include Lithium difluorooxalatoborate, lithium bis (oxalato) borate, lithium tetrafluorooxalatophosphate, lithium difluorobis (oxalato) phosphate, lithium tris (oxalato) phosphate, etc. Lithium bis (oxalato) borate and lithium difluorobis (oxalato) phosphate are preferred.
- the oxalate salt may be used alone or in combination of two or more in any combination and ratio.
- the content of the oxalate salt with respect to the whole non-aqueous electrolyte solution of the present invention is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.1% in 100% by mass of the non-aqueous electrolyte solution. Further, it is usually less than 8% by mass, preferably 5% by mass or less, more preferably 3% by mass or less, further preferably 2% by mass or less, and most preferably 1.5% by mass or less.
- the total amount of the oxalate salts may be set to satisfy the above range.
- the non-aqueous electrolyte battery tends to exhibit a sufficient cycle characteristics improvement effect, and the high temperature storage characteristics deteriorate, the amount of gas generated increases, and the discharge capacity maintenance ratio decreases. Easy to avoid.
- the non-aqueous electrolyte solution of the present invention usually contains an electrolyte as its component, as is the case with general non-aqueous electrolyte solutions.
- An electrolyte used for the non-aqueous electrolyte solution of this invention, A well-known electrolyte can be used.
- specific examples of the electrolyte will be described in detail.
- ⁇ Lithium salt> As the electrolyte in the nonaqueous electrolytic solution of the present invention, a lithium salt is usually used.
- the lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples include the following.
- inorganic lithium salts such as LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiTaF 6 , LiWF 7 ; Lithium fluorophosphates such as LiPF 6 ; Lithium tungstate salts such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 Carboxylic acid lithium salts such as CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li; Sulfonic acid lithium salts such as CH 3 SO 3 Li; LiN (FCO 2 ) 2 , LiN (FCO) (FSO 2 ), LiN (FSO 2 ) 2 , LiN (FSO 2 ) (CF 3 SO 2 ), LiN (CF 3 SO 2 ) 2 , LiN (C 2 F
- inorganic lithium salts lithium fluorophosphate salts, lithium sulfonate salts, lithium imide Those selected from salts and lithium oxalate salts are preferred.
- the said electrolyte salt may be used independently, or may use 2 or more types together.
- the total concentration of these electrolytes in the non-aqueous electrolyte solution is not particularly limited, but is usually 8% by mass or more, preferably 8.5% by mass or more, more preferably 9% by mass with respect to the total amount of the non-aqueous electrolyte solution. % Or more. Moreover, the upper limit is 18 mass% or less normally, Preferably it is 17 mass% or less, More preferably, it is 16 mass% or less. When the total concentration of the electrolyte is within the above range, the electric conductivity is appropriate for battery operation, and thus sufficient output characteristics tend to be obtained.
- Nonaqueous solvent The non-aqueous electrolyte solution of the present invention usually contains a non-aqueous solvent that dissolves the above-described electrolyte as a main component, as with a general non-aqueous electrolyte solution.
- a well-known organic solvent can be used. Examples of organic solvents include, but are not limited to, saturated cyclic carbonates, chain carbonates, ether compounds, sulfone compounds, and the like. These can be used alone or in combination of two or more.
- saturated cyclic carbonate usually include those having an alkylene group having 2 to 4 carbon atoms, and a saturated cyclic carbonate having 2 to 3 carbon atoms is preferably used from the viewpoint of improving battery characteristics resulting from an improvement in the degree of lithium ion dissociation. .
- saturated cyclic carbonate examples include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Among these, ethylene carbonate and propylene carbonate are preferable, and ethylene carbonate that is difficult to be oxidized and reduced is more preferable.
- a saturated cyclic carbonate may be used individually by 1 type, and may have 2 or more types together by arbitrary combinations and ratios.
- the content of the saturated cyclic carbonate is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the lower limit of the content when one type is used alone is based on the total amount of the solvent of the nonaqueous electrolytic solution. In general, it is 3% by volume or more, preferably 5% by volume or more.
- an upper limit is 90 volume% or less normally, Preferably it is 85 volume% or less, More preferably, it is 80 volume% or less. By setting it within this range, the oxidation / reduction resistance of the nonaqueous electrolytic solution is improved, and the stability during high-temperature storage tends to be improved.
- the volume% in this invention means the volume in 25 degreeC and 1 atmosphere.
- Chain carbonate As the chain carbonate, one having 3 to 7 carbon atoms is usually used, and a chain carbonate having 3 to 5 carbon atoms is preferably used in order to adjust the viscosity of the electrolytic solution to an appropriate range.
- chain carbonate dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, n-butyl methyl carbonate
- examples thereof include isobutyl methyl carbonate, t-butyl methyl carbonate, ethyl-n-propyl carbonate, n-butyl ethyl carbonate, isobutyl ethyl carbonate, t-butyl ethyl carbonate and the like.
- dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, n-propyl isopropyl carbonate, ethyl methyl carbonate, and methyl-n-propyl carbonate are preferable, and dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are particularly preferable. is there.
- chain carbonates having a fluorine atom can also be suitably used.
- the number of fluorine atoms contained in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less.
- the fluorinated chain carbonate has a plurality of fluorine atoms, they may be bonded to the same carbon or may be bonded to different carbons.
- the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.
- fluorinated dimethyl carbonate derivative examples include fluoromethyl methyl carbonate, difluoromethyl methyl carbonate, trifluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, bis (difluoro) methyl carbonate, bis (trifluoromethyl) carbonate, and the like.
- Fluorinated ethyl methyl carbonate derivatives include 2-fluoroethyl methyl carbonate, ethyl fluoromethyl carbonate, 2,2-difluoroethyl methyl carbonate, 2-fluoroethyl fluoromethyl carbonate, ethyl difluoromethyl carbonate, 2,2,2-trimethyl Examples include fluoroethyl methyl carbonate, 2,2-difluoroethyl fluoromethyl carbonate, 2-fluoroethyl difluoromethyl carbonate, and ethyl trifluoromethyl carbonate.
- Fluorinated diethyl carbonate derivatives include ethyl- (2-fluoroethyl) carbonate, ethyl- (2,2-difluoroethyl) carbonate, bis (2-fluoroethyl) carbonate, ethyl- (2,2,2-trifluoro).
- Ethyl) carbonate 2,2-difluoroethyl-2′-fluoroethyl carbonate, bis (2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl-2′-fluoroethyl carbonate, 2,2, Examples include 2-trifluoroethyl-2 ′, 2′-difluoroethyl carbonate, bis (2,2,2-trifluoroethyl) carbonate, and the like.
- chain carbonate one kind may be used alone, and two kinds or more may be used in optional combination and ratio.
- the content of the chain carbonate is not particularly limited, but is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more based on the total amount of the solvent of the non-aqueous electrolyte solution. Moreover, it is 90 volume% or less normally, Preferably it is 85 volume% or less, More preferably, it is 80 volume% or less.
- battery performance can be remarkably improved by combining ethylene carbonate with a specific content with respect to a specific chain carbonate.
- the content of ethylene carbonate is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired. It is usually 15% by volume or more, preferably 20% by volume, and usually 45% by volume or less, preferably 40% by volume or less based on the total amount of the solvent.
- the content of dimethyl carbonate is based on the total amount of the solvent of the non-aqueous electrolyte. In general, it is 20% by volume or more, preferably 30% by volume or more, and usually 50% by volume or less, preferably 45% by volume or less, and the content of ethyl methyl carbonate is usually 20% by volume or more, preferably 30% by volume or more. Further, it is usually 50% by volume or less, preferably 45% by volume or less.
- Ether compounds As the ether compound, a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms are preferable. Examples of the chain ether having 3 to 10 carbon atoms include diethyl ether, di (2-fluoroethyl) ether, di (2,2-difluoroethyl) ether, di (2,2,2-trifluoroethyl) ether, ethyl (2-fluoroethyl) ether, ethyl (2,2,2-trifluoroethyl) ether, ethyl (1,1,2,2-tetrafluoroethyl) ether, (2-fluoroethyl) (2,2,2 -Trifluoroethyl) ether, (2-fluoroethyl) (1,1,2,2-tetrafluoroethyl) ether, (2,2,2-trifluoroethyl) (1,1,2,2-tetraflu
- Examples of the cyclic ether having 3 to 6 carbon atoms include tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 1,3-dioxane, 2-methyl-1,3-dioxane, 4-methyl-1,3-dioxane, 1 , 4-dioxane and the like, and fluorinated compounds thereof.
- dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether have a high solvating ability to lithium ions and ion dissociation properties. It is preferable in terms of improvement.
- Particularly preferred are dimethoxymethane, diethoxymethane, and ethoxymethoxymethane because they have low viscosity and give high ionic conductivity.
- An ether type compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the content of the ether compound is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.
- 100% by volume of the nonaqueous solvent usually 1% by volume or more, preferably 2% by volume or more, more preferably.
- the total amount of the ether compounds may satisfy the above range.
- the content of the ether compound is within the above preferred range, it is easy to ensure the effect of improving the ionic conductivity resulting from the improvement of the lithium ion dissociation degree and the viscosity reduction of the chain ether.
- the negative electrode active material is a carbonaceous material, the phenomenon that the chain ether is co-inserted with the lithium ions can be suppressed, so that the input / output characteristics and the charge / discharge rate characteristics can be within an appropriate range.
- the sulfone compound is not particularly limited even if it is a cyclic sulfone or a chain sulfone, but in the case of a cyclic sulfone, it usually has 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms. In general, compounds having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms are preferred.
- the number of sulfonyl groups in one molecule of the sulfone compound is not particularly limited, but is usually 1 or 2.
- cyclic sulfone examples include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones that are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds.
- trimethylene sulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds examples include trimethylene sulfones, tetramethylene sulfones, and hexamethylene sulfones that are monosulfone compounds; trimethylene disulfones, tetramethylene disulfones, and hexamethylene disulfones that are disulfone compounds.
- the sulfolane is preferably sulfolane and / or a sulfolane derivative (hereinafter sometimes abbreviated as “sulfolane” including sulfolane).
- sulfolane derivative one in which one or more hydrogen atoms bonded to the carbon atom constituting the sulfolane ring are substituted with a fluorine atom or an alkyl group is preferable.
- chain sulfone dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, n-propyl methyl sulfone, n-propyl ethyl sulfone, di-n-propyl sulfone, isopropyl methyl sulfone, isopropyl ethyl sulfone, diisopropyl sulfone, n- Butyl methyl sulfone, n-butyl ethyl sulfone, t-butyl methyl sulfone, t-butyl ethyl sulfone, monofluoromethyl methyl sulfone, difluoromethyl methyl sulfone, trifluoromethyl methyl sulfone, monofluoroethyl methyl sulfone, difluoroethyl methyl sulfone
- a sulfone compound may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the content of the sulfone compound is not particularly limited and may be arbitrary as long as the effects of the present invention are not significantly impaired.
- the content of the sulfone compound is usually 0.3% by volume or more, preferably 0. It is 5% by volume or more, more preferably 1% by volume or more, and is usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less.
- the total amount of the sulfone compounds may satisfy the above range.
- an electrolytic solution excellent in high-temperature storage stability tends to be obtained.
- auxiliary agents may be contained within the range where the effects of the present invention are exhibited.
- Carbonate compounds such as erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl-methyl carbonate; Methyl-2-propynyl oxalate, ethyl-2-propynyl oxalate, bis (2-propynyl) oxalate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, di (2-propynyl) glutarate, Methyl-2-propynyl carbonate, ethyl-2-propynyl carbonate, bis (2-propynyl) carbonate, 2-butyne-1,4-diyl-dimethanesulfonate, 2-butyne-1,4-d
- the content of other auxiliaries is not particularly limited and is arbitrary as long as the effects of the present invention are not significantly impaired.
- the content of other auxiliaries is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, based on the total amount of the non-aqueous electrolyte solution. Usually, it is 5 mass% or less, Preferably it is 3 mass% or less, More preferably, it is 1 mass% or less. Within this range, the effects of other auxiliaries can be sufficiently exhibited and the high-temperature storage stability tends to be improved. When two or more kinds of other auxiliaries are used in combination, the total amount of the other auxiliaries may be set to satisfy the above range.
- Non-aqueous electrolyte battery of the present invention comprises a current collector and a positive electrode having a positive electrode active material layer provided on the current collector, and a current collector and a negative electrode active material layer provided on the current collector.
- the negative electrode which has and can occlude and discharge
- the non-aqueous electrolyte battery of the present invention is the same as the conventionally known non-aqueous electrolyte battery except for the above-described non-aqueous electrolyte solution of the present invention.
- a positive electrode and a negative electrode are laminated via a porous film (separator) impregnated with the non-aqueous electrolyte solution of the present invention, and these are housed in a case (exterior body). Therefore, the shape of the non-aqueous electrolyte battery of the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
- Non-aqueous electrolyte As the non-aqueous electrolyte, the above-described non-aqueous electrolyte of the present invention is used. In addition, in the range which does not deviate from the meaning of this invention, it is also possible to mix
- Negative electrode> The negative electrode active material used for the negative electrode is described below.
- the negative electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions. Specific examples include those having carbon as a constituent element such as a carbonaceous material, alloy materials, and the like. These may be used individually by 1 type, and may be used together combining 2 or more types arbitrarily.
- Negative electrode active material examples include carbonaceous materials and alloy-based materials as described above.
- Examples of the carbonaceous material include (1) natural graphite, (2) artificial graphite, (3) amorphous carbon, (4) carbon-coated graphite, (5) graphite-coated graphite, and (6) resin-coated graphite. It is done.
- Examples of natural graphite include scaly graphite, scaly graphite, soil graphite, and / or graphite particles obtained by subjecting these graphites as raw materials to spheroidization and densification.
- spherical or ellipsoidal graphite subjected to spheroidizing treatment is particularly preferable from the viewpoints of particle filling properties and charge / discharge rate characteristics.
- an apparatus used for the spheronization treatment for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used.
- the apparatus which has a mechanism which gives a mechanical action repeatedly by circulating a raw material is preferable.
- the peripheral speed of the rotating rotor is preferably set to 30 to 100 m / sec, more preferably set to 40 to 100 m / sec, and more preferably 50 to 100 m / sec. More preferably, it is set to seconds.
- the spheronization treatment can be performed by simply passing the raw material, but it is preferable to circulate or stay in the apparatus for 30 seconds or more, and to circulate or stay in the apparatus for 1 minute or more. Is more preferable.
- Artificial graphite includes coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride,
- An organic compound such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin is usually in a range of 2500 ° C. or higher and usually 3200 ° C. or lower. Examples thereof include those produced by graphitization at a temperature and, if necessary, pulverized and / or classified.
- a silicon-containing compound, a boron-containing compound, or the like can also be used as a graphitization catalyst.
- artificial graphite obtained by graphitizing mesocarbon microbeads separated in the heat treatment process of pitch can be mentioned.
- the artificial graphite of the granulated particle which consists of primary particles is also mentioned.
- a graphitizable carbonaceous material powder such as mesocarbon microbeads or coke and a graphitizable binder such as tar or pitch and a graphitization catalyst are mixed, graphitized, and pulverized as necessary.
- graphite particles obtained by gathering or bonding a plurality of flat particles obtained such that their orientation planes are non-parallel are listed.
- amorphous carbon an amorphous carbon that has been heat-treated at least once in a temperature range (400 to 2200 ° C.) in which no graphitizable carbon precursor such as tar or pitch is used as a raw material.
- amorphous carbon particles obtained by heat treatment using particles or a non-graphitizable carbon precursor such as a resin as a raw material.
- Examples of the carbon-coated graphite include those obtained as follows. Natural graphite and / or artificial graphite is mixed with a carbon precursor which is an organic compound such as tar, pitch or resin, and heat-treated at least once in the range of 400 to 2300 ° C. The obtained natural graphite and / or artificial graphite is used as nuclear graphite, which is coated with amorphous carbon to obtain a carbon graphite composite. This carbon graphite composite is exemplified as carbon-coated graphite (4).
- the composite form is a form in which a plurality of primary particles are combined with carbon originating from the carbon precursor as a binder, even if the entire or part of the surface of the nuclear graphite is coated with amorphous carbon. May be.
- hydrocarbon gases such as benzene, toluene, methane, propane, aromatic volatiles at a high temperature, and depositing carbon on the graphite surface (CVD)
- the carbon graphite composite can be obtained.
- Examples of the graphite-coated graphite include those obtained as follows. Natural graphite and / or artificial graphite and a carbon precursor of an easily graphitizable organic compound such as tar, pitch or resin are mixed and heat-treated at least in the range of about 2400 to 3200 ° C. The obtained natural graphite and / or artificial graphite is used as nuclear graphite, and the whole or part of the surface of the nuclear graphite is coated with a graphitized product to obtain graphite-coated graphite (5).
- Resin-coated graphite is, for example, natural graphite and / or artificial graphite mixed with resin and dried at a temperature of less than 400 ° C. It is obtained by coating the nuclear graphite with.
- carbonaceous materials (1) to (6) described above may be used alone or in combination of two or more in any combination and ratio.
- Examples of organic compounds such as tar, pitch and resin used in the carbonaceous materials (2) to (5) above include heavy coal-based oils, direct-current heavy oils, cracked heavy petroleum oils, and aromatic hydrocarbons. , N ring compounds, S ring compounds, polyphenylene, organic synthetic polymers, natural polymers, organic compounds capable of carbonization selected from the group consisting of thermoplastic resins and thermosetting resins.
- the raw material organic compound may be used after being dissolved in a low molecular organic solvent in order to adjust the viscosity at the time of mixing.
- natural graphite and / or artificial graphite used as a raw material for nuclear graphite is preferably natural graphite that has been spheroidized.
- the alloy material used as the negative electrode active material is lithium simple substance, single metal and alloy forming lithium alloy, or oxides, carbides, nitrides, silicas thereof as long as lithium can be occluded / released. Any of compounds such as fluoride, sulfide or phosphide may be used, and it is not particularly limited.
- the single metal and the alloy forming the lithium alloy are preferably materials containing a group 13 and group 14 metal / metalloid element (that is, excluding carbon), More preferably, single metals of aluminum, silicon and tin and alloys or compounds containing these atoms, More preferably, it has silicon or tin as a constituent element, such as a simple metal of silicon and tin and an alloy or compound containing these atoms. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- Metal particles that can be alloyed with Li When a single metal and an alloy forming a lithium alloy, or a compound thereof, such as an oxide, carbide, nitride, silicide, sulfide or phosphide, is used as the negative electrode active material, the metal that can be alloyed with Li is: It is in particle form.
- the metal particles are metal particles that can be alloyed with Li, identification of the metal particle phase by X-ray diffraction, observation of the particle structure by electron microscope and elemental analysis, element by fluorescent X-rays Analysis and the like.
- the metal particles that can be alloyed with Li any conventionally known metal particles can be used.
- the metal particles are, for example, Fe, Co, Sb. Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, As, Nb, Mo, Cu, Zn, Ge, In, Ti, and W A metal or a compound thereof is preferable.
- an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed of two or more kinds of metal elements.
- a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn, and W or a metal compound thereof is preferable.
- metal compound examples include metal oxides, metal nitrides, and metal carbides.
- alloy which consists of 2 or more types of metals.
- Si or Si metal compounds are preferable.
- the Si metal compound is preferably a Si metal oxide.
- Si or Si metal compound is preferable in terms of increasing the capacity of the battery.
- Si or Si metal compounds are collectively referred to as Si compounds.
- Specific examples of the Si compound include SiO x , SiN x , SiC x , and SiZ x O y (Z ⁇ C, N).
- the Si compound is preferably a Si metal oxide, and the Si metal oxide is SiO x in a general formula.
- the general formula SiO x is obtained using Si dioxide (SiO 2 ) and metal Si (Si) as raw materials, and the value of x is usually 0 ⁇ x ⁇ 2.
- SiO x has a larger theoretical capacity than graphite, and amorphous Si or nano-sized Si crystals easily allow alkali ions such as lithium ions to enter and exit, so that a high capacity can be obtained.
- the Si metal oxide is specifically expressed as SiO x , where x is 0 ⁇ x ⁇ 2, more preferably 0.2 or more and 1.8 or less, and still more preferably 0.8. It is 4 or more and 1.6 or less, and particularly preferably 0.6 or more and 1.4 or less. If it is this range, it becomes possible to reduce the irreversible capacity
- the oxygen content of metal particles that can be alloyed with Li is not particularly limited, but is usually 0.01% by mass or more and 8% by mass or less, and 0.05 It is preferable that they are mass% or more and 5 mass% or less.
- the oxygen distribution state in the particles may be present near the surface, present inside the particle, or uniformly present within the particle, but is preferably present near the surface.
- the amount of oxygen contained in the metal particles that can be alloyed with Li is within the above range, the volume expansion associated with the secondary charge / discharge of the non-aqueous electrolyte is suppressed by the strong bond between the metal particles and O (oxygen atoms), It is preferable because of excellent cycle characteristics.
- the negative electrode active material may contain metal particles that can be alloyed with Li and graphite particles.
- the negative electrode active material may be a mixture in which Li and alloyable metal particles and graphite particles are mixed in the form of independent particles, or Li and alloyable metal particles are formed on the surface of the graphite particles and It may also be a complex present inside.
- the composite of metal particles that can be alloyed with Li and graphite particles is particularly limited as long as the particles include metal particles that can be alloyed with Li and graphite particles. However, it is preferably a particle in which metal particles capable of being alloyed with Li and graphite particles are integrated by physical and / or chemical bonding. As a more preferable form, the solid particles are dispersed in the particles so that the metal particles and graphite particles that can be alloyed with Li are present at least on the surface of the composite particles and in the bulk. In order to integrate them by physical and / or chemical bonding, graphite particles are present.
- a preferable form is a composite material composed of at least metal particles capable of being alloyed with Li and graphite particles, and the graphite particles, preferably, natural graphite has a folded structure with a curved structure.
- the composite material (negative electrode active material) is characterized in that metal particles capable of being alloyed with Li are present in the gaps in the structure.
- the gap may be a gap, or a substance that buffers expansion and contraction of metal particles that can be alloyed with Li, such as amorphous carbon, graphite, and resin, is present in the gap. May be.
- the content ratio of metal particles that can be alloyed with Li with respect to the sum of metal particles that can be alloyed with Li and graphite particles is usually 0.1% by mass or more, preferably 0 0.5% by mass or more, more preferably 1.0% by mass or more, and still more preferably 2.0% by mass or more. Also, it is usually 99% by mass or less, preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, still more preferably 25% by mass or less, still more preferably 20% by mass or less, particularly Preferably it is 15 mass% or less, Most preferably, it is 10 mass% or less. Within this range, side reactions on the Si surface can be controlled, which is preferable in that a sufficient capacity can be obtained in a non-aqueous electrolyte battery.
- the negative electrode active material of the present invention may be coated with a carbonaceous material or a graphite material.
- coating with an amorphous carbonaceous material is preferable from the viewpoint of lithium ion acceptability.
- This coverage is usually 0.5% or more and 30% or less, preferably 1% or more and 25% or less, and more preferably 2% or more and 20% or less.
- the upper limit of the coverage is from the viewpoint of reversible capacity when assembling the battery, and the lower limit of the coverage is a viewpoint that the carbonaceous material as a core is uniformly coated with amorphous carbon and is strongly granulated, When pulverized after firing, the above range is preferable from the viewpoint of the particle size of the obtained particles.
- the coverage (content rate) of the carbide derived from the organic compound of the negative electrode active material finally obtained is the amount of the negative electrode active material, the amount of the organic compound, and the residue measured by a micro method in accordance with JIS K 2270. It can be calculated by the following formula based on the charcoal rate.
- the internal porosity of the negative electrode active material is usually 1% or more, preferably 3% or more, more preferably 5% or more, and further preferably 7% or more. Further, it is usually less than 50%, preferably 40% or less, more preferably 30% or less, and still more preferably 20% or less. If the internal porosity is too small, the amount of liquid in the negative electrode active material particles tends to decrease in the non-aqueous electrolyte battery. On the other hand, when the internal porosity is too large, there is a tendency that the inter-particle gap is reduced when an electrode is used.
- the lower limit of the internal porosity is preferably in the above range from the viewpoint of charge / discharge characteristics, and the upper limit is preferably in the above range from the viewpoint of diffusion of the non-aqueous electrolyte.
- this gap may be a void, or a substance that buffers expansion and contraction of metal particles that can be alloyed with Li, such as amorphous carbon, graphite, resin, etc. These may be present or filled in the gap.
- a negative electrode active material is formed by adding a binder, a solvent, and, if necessary, a thickener, a conductive material, a filler, etc. to form a slurry, which is applied to a current collector, dried and then pressed. can do.
- the alloy-based material negative electrode can be manufactured using any known method.
- a manufacturing method of the negative electrode for example, a method in which a negative electrode active material added with a binder or a conductive material is roll-formed as it is to form a sheet electrode, or a compression-molded pellet electrode and The above negative electrode is usually applied to a negative electrode current collector (hereinafter also referred to as “negative electrode current collector”) by a method such as a coating method, a vapor deposition method, a sputtering method, or a plating method.
- a method of forming a thin film layer (negative electrode active material layer) containing an active material is used.
- Examples of the material of the negative electrode current collector include steel, copper, copper alloy, nickel, nickel alloy, and stainless steel. Of these, copper foil is preferred from the viewpoint of easy processing into a thin film and cost.
- the thickness of the negative electrode current collector is usually 1 ⁇ m or more, preferably 5 ⁇ m or more, and is usually 100 ⁇ m or less, preferably 50 ⁇ m or less. If the thickness of the negative electrode current collector is too thick, the capacity of the entire non-aqueous electrolyte battery may be too low, and conversely, if it is too thin, handling may be difficult.
- the surface of these negative electrode current collectors is preferably roughened in advance.
- Surface roughening methods include blasting, rolling with a rough surface roll, abrasive cloth paper with abrasive particles fixed, grinding wheel, emery buff, machine that polishes the current collector surface with a wire brush equipped with steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.
- a perforated negative electrode current collector such as an expanded metal or a punching metal can be used.
- This type of negative electrode current collector can be freely changed in mass by changing its aperture ratio. Further, when a negative electrode active material layer is formed on both surfaces of this type of negative electrode current collector, the negative electrode active material layer is further less likely to peel due to the rivet effect through the hole. However, when the aperture ratio becomes too high, the contact area between the negative electrode active material layer and the negative electrode current collector becomes small, and thus the adhesive strength may be lowered.
- the slurry for forming the negative electrode active material layer is usually prepared by adding a binder, a thickener and the like to the negative electrode material.
- the “negative electrode material” in this specification refers to a material in which a negative electrode active material and a conductive material are combined.
- the content of the negative electrode active material in the negative electrode material is usually 70% by mass or more, particularly 75% by mass or more, and usually 97% by mass or less, and particularly preferably 95% by mass or less.
- the content of the negative electrode active material is too small, the capacity of the secondary battery using the obtained negative electrode tends to be insufficient.
- the content is too large, the content of the conductive material is relatively insufficient, so that It tends to be difficult to ensure conductivity.
- the total amount of the negative electrode active materials may be set to satisfy the above range.
- the conductive material used for the negative electrode examples include metal materials such as copper and nickel; carbon materials such as graphite and carbon black. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio. In particular, it is preferable to use a carbon material as the conductive material because the carbon material acts as an active material.
- the content of the conductive material in the negative electrode material is usually 3% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, and preferably 25% by mass or less. When the content of the conductive material is too small, the conductivity tends to be insufficient. When the content is too large, the content of the negative electrode active material and the like is relatively insufficient, and thus the battery capacity and strength tend to decrease. Note that when two or more conductive materials are used in combination, the total amount of the conductive materials may satisfy the above range.
- any material can be used as long as it is a material that is safe with respect to the solvent and electrolyte used in the production of the electrode.
- examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber / isoprene rubber, butadiene rubber, ethylene / acrylic acid copolymer, and ethylene / methacrylic acid copolymer. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- the content of the binder is usually 0.5 parts by mass or more, preferably 1 part by mass or more, and usually 10 parts by mass or less, preferably 8 parts by mass or less, with respect to 100 parts by mass of the negative electrode material. .
- the content of the binder is too small, the strength of the obtained negative electrode tends to be insufficient.
- the content of the negative electrode active material and the like is relatively insufficient, and thus the battery capacity and conductivity tend to be insufficient. It becomes.
- thickener used for the negative electrode examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- the thickener may be used as necessary, but when used, the thickener content in the negative electrode active material layer is usually in the range of 0.5% by mass or more and 5% by mass or less. Is preferred.
- the slurry for forming the negative electrode active material layer is prepared by mixing a conductive material, a binder, and a thickener as necessary with the negative electrode active material, and using an aqueous solvent or an organic solvent as a dispersion medium.
- aqueous solvent water is usually used, and an organic solvent such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone is used in combination within a range of 30% by mass or less based on water. You can also.
- organic solvent examples include cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and aromatic hydrocarbons such as anisole, toluene and xylene. And alcohols such as butanol and cyclohexanol.
- cyclic amides such as N-methylpyrrolidone
- linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. Any one of these may be used alone, or two or more may be used in any combination and ratio.
- the obtained slurry is applied onto the above-described negative electrode current collector, dried, and pressed to form a negative electrode active material layer, thereby obtaining a negative electrode.
- the method of application is not particularly limited, and a method known per se can be used.
- the drying method is not particularly limited, and a known method such as natural drying, heat drying, or reduced pressure drying can be used.
- the electrode structure when the negative electrode active material is made into an electrode is not particularly limited, but the density of the negative electrode active material present on the current collector is preferably 1 g ⁇ cm ⁇ 3 or more, and 1.2 g ⁇ cm ⁇ 3 or more. but more preferably, particularly preferably 1.3 g ⁇ cm -3 or more, preferably 2.2 g ⁇ cm -3 or less, more preferably 2.1 g ⁇ cm -3 or less, 2.0 g ⁇ cm -3 or less More preferred is 1.9 g ⁇ cm ⁇ 3 or less.
- the density of the negative electrode active material present on the current collector exceeds the above range, the negative electrode active material particles are destroyed, increasing the initial irreversible capacity of the non-aqueous electrolyte battery, and the current collector / negative electrode active material There is a case where high current density charge / discharge characteristics are deteriorated due to a decrease in permeability of the non-aqueous electrolyte to the vicinity of the interface.
- the amount is less than the above range, the conductivity between the negative electrode active materials decreases, the battery resistance increases, and the capacity per unit volume may decrease.
- Positive electrode> The positive electrode used for the non-aqueous electrolyte battery of the present invention will be described below.
- lithium cobaltate or a transition metal oxide containing at least Ni and Co and 50 mol% or more of the transition metals is Ni and Co.
- transition metal oxides in which at least% is Ni and Co are preferred. This is because Ni and Co are suitable for use as a positive electrode material of a secondary battery because of the oxidation-reduction potential, and are suitable for high capacity applications.
- the transition metal component of the lithium transition metal oxide includes Ni and Co as essential elements, but other metals include Mn, V, Ti, Cr, Fe, Cu, Al, Mg, Zr, Er, and the like. Mn, Ti, Fe, Al, Mg, Zr and the like are preferable. Specific examples of the lithium transition metal oxide include, for example, LiCoO 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.80 Co 0.15 Al 0.05 O 2 , LiNi 0.33.
- a transition metal oxide represented by the following composition formula (1) is preferable.
- Li a1 Ni b1 Co c1 M d1 O 2 (1) (In the formula (1), 0.90 ⁇ a1 ⁇ 1.10, 0.50 ⁇ b1 ⁇ 0.98, 0.01 ⁇ c1 ⁇ 0.50, 0.01 ⁇ d1 ⁇ 0.50 are shown.
- B1 + c1 + d1 1.
- M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti, and Er.
- the transition metal is difficult to elute from the positive electrode, and even if it elutes, Ni and Co are not contained in the non-aqueous secondary battery. This is because the adverse effect of is small.
- a transition metal oxide represented by the following composition formula (2) is more preferable.
- Li a2 Ni b2 Co c2 M d2 O 2 (2) (In the formula (2), 0.90 ⁇ a2 ⁇ 1.10, 0.50 ⁇ b2 ⁇ 0.96, 0.03 ⁇ c2 ⁇ 0.50, 0.01 ⁇ d2 ⁇ 0.40 are shown.
- B2 + c2 + d2 1.
- M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
- Ni and Co are the main components and the composition ratio of Ni is larger than the composition ratio of Co, when used as a positive electrode of a non-aqueous electrolyte battery, it is stable and can take out a high capacity. Because it becomes.
- a transition metal oxide represented by the following composition formula (3) is more preferable.
- Li a3 Ni b3 Co c3 M d3 O 2 (3) (In the formula (3), 0.90 ⁇ a3 ⁇ 1.10, 0.60 ⁇ b3 ⁇ 0.94, 0.05 ⁇ c3 ⁇ 0.2, 0.01 ⁇ d3 ⁇ 0.3 are shown.
- B3 + c3 + d3 1.
- M represents at least one element selected from the group consisting of Mn, Al, Mg, Zr, Fe, Ti and Er.)
- two or more of the positive electrode active materials may be mixed and used. Similarly, at least one of the positive electrode active materials may be mixed with another positive electrode active material.
- positive electrode active materials include transition metal oxides, transition metal phosphate compounds, transition metal silicate compounds, and transition metal borate compounds not listed above.
- lithium manganese composite oxide having a spinel structure and a lithium-containing transition metal phosphate compound having an olivine structure are preferable.
- Specific examples of the lithium manganese composite oxide having a spinel structure include LiMn 2 O 4 , LiMn 1.8 Al 0.2 O 4 , and LiMn 1.5 Ni 0.5 O 4 .
- transition metal of the lithium-containing transition metal phosphate compound V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples include, for example, LiFePO 4 , Li 3 Fe 2 (PO 4 3 , Iron phosphates such as LiFeP 2 O 7 , Cobalt phosphates such as LiCoPO 4 , Manganese phosphates such as LiMnPO 4 , Al, Ti , V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W and the like substituted with other metals.
- LiFePO 4 can be given as a more preferable specific example.
- surface adhering substance A material having a composition different from that of the main constituent of the positive electrode active material (hereinafter referred to as “surface adhering substance” as appropriate) may be used on the surface of the positive electrode active material.
- surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, Examples thereof include sulfates such as calcium sulfate and aluminum sulfate, carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate, and carbon.
- These surface adhering substances are, for example, a method in which they are dissolved or suspended in a solvent and impregnated and added to the positive electrode active material and then dried, or a surface adhering substance precursor is dissolved or suspended in a solvent and impregnated and added to the positive electrode active material. Then, it can be made to adhere to the surface of the positive electrode active material by a method of reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing simultaneously.
- the method of attaching carbonaceous material mechanically later for example in the form of activated carbon etc. can also be used.
- the mass of the surface adhering substance adhering to the surface of the positive electrode active material is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more with respect to the mass of the positive electrode active material. Further, it is preferably 20% or less, more preferably 10% or less, still more preferably 5% or less.
- the surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte on the surface of the positive electrode active material, and can improve the battery life. Moreover, when the adhesion amount is within the above range, the effect can be sufficiently exhibited, and resistance is hardly increased without inhibiting the entry and exit of lithium ions.
- Shape of the positive electrode active material particles a lump shape, a polyhedron shape, a spherical shape, an elliptical spherical shape, a plate shape, a needle shape, a columnar shape, and the like, which are conventionally used, are used.
- the primary particles may be aggregated to form secondary particles, and the shape of the secondary particles may be spherical or elliptical.
- the method for producing the positive electrode active material is not particularly limited as long as it does not exceed the gist of the present invention, but there are several methods, which are common as methods for producing inorganic compounds. The method is used. In particular, various methods are conceivable for producing a spherical or elliptical active material. For example, transition metal source materials such as transition metal nitrates and sulfates, and source materials of other elements as necessary.
- transition metal raw materials such as transition metal nitrates, sulfates, hydroxides, oxides and the like, and if necessary, raw materials of other elements are dissolved or pulverized and dispersed in a solvent such as water. Then, it is dry-molded with a spray dryer or the like to obtain a spherical or oval spherical precursor, and a Li source such as LiOH, Li 2 CO 3 , LiNO 3 is added to the precursor and calcined at a high temperature to obtain an active material Is mentioned.
- a Li source such as LiOH, Li 2 CO 3 , LiNO 3
- transition metal source materials such as transition metal nitrates, sulfates, hydroxides, oxides, Li sources such as LiOH, Li 2 CO 3 , LiNO 3 , and other elements as necessary.
- the raw material is dissolved or pulverized and dispersed in a solvent such as water, and then dried and molded with a spray drier or the like to obtain a spherical or elliptical precursor, which is fired at a high temperature to obtain an active material.
- a solvent such as water
- the positive electrode is produced by forming a positive electrode active material layer containing positive electrode active material particles and a binder on a current collector.
- the production of the positive electrode using the positive electrode active material can be produced by any known method.
- a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these materials are liquid media
- a positive electrode can be obtained by forming a positive electrode active material layer on the current collector by applying it to a positive electrode current collector and drying it as a slurry by dissolving or dispersing in a slurry.
- the content of the positive electrode active material in the positive electrode active material layer is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and preferably 99.9% by mass or less. Yes, 99 mass% or less is more preferable.
- the positive electrode active material powder in this invention may be used individually by 1 type, and may use together 2 or more types of a different composition or different powder physical properties by arbitrary combinations and ratios. When two or more active materials are used in combination, the composite oxide containing lithium and manganese is preferably used as a powder component.
- Cobalt or nickel is an expensive metal with a small amount of resources, and it is not preferable in terms of cost because it uses a large amount of active material in large batteries that require high capacity, such as for automobiles. This is because it is desirable to use manganese as a main transition metal.
- a known conductive material can be arbitrarily used as the conductive material.
- Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke.
- metal materials such as copper and nickel
- graphite such as natural graphite and artificial graphite (graphite)
- carbon black such as acetylene black
- carbonaceous materials such as amorphous carbon such as needle coke.
- these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- the content of the conductive material in the positive electrode active material layer is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, still more preferably 1% by mass or more, and preferably 50% by mass or less. 30 mass% or less is more preferable, and 15 mass% or less is still more preferable. When the content is within the above range, sufficient conductivity can be secured. Furthermore, it is easy to prevent a decrease in battery capacity.
- the binder used for manufacturing the positive electrode active material layer is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used during electrode manufacturing.
- the coating method it is not particularly limited as long as it is a material that is dissolved or dispersed in a liquid medium used at the time of electrode production.
- Specific examples include polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, and cellulose.
- Resin polymers such as nitrocellulose; rubbery polymers such as SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, ethylene propylene rubber; styrene butadiene Styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated product thereof etc.
- Thermoplastic elastomeric polymer soft resinous polymer such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / ⁇ -olefin copolymer; polyvinylidene flu
- the content of the binder in the positive electrode active material layer is preferably 0.1% by mass or more, more preferably 1% by mass or more, further preferably 3% by mass or more, and preferably 80% by mass or less. Yes, 60 mass% or less is more preferable, 40 mass% or less is further more preferable, and 10 mass% or less is especially preferable.
- the ratio of the binder is within the above range, the positive electrode active material can be sufficiently retained and the mechanical strength of the positive electrode can be secured, so that battery performance such as cycle characteristics is improved. Furthermore, it also leads to avoiding a decrease in battery capacity and conductivity.
- Liquid medium As a liquid medium used for preparing a slurry for forming a positive electrode active material layer, a positive electrode active material, a conductive material, a binder, and a thickener used as necessary can be dissolved or dispersed. If it is a solvent, there is no restriction
- organic media examples include aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone.
- Esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N, N-dimethylaminopropylamine; ethers such as diethyl ether and tetrahydrofuran (THF); N-methylpyrrolidone (NMP) and dimethylformamide And amides such as dimethylacetamide; aprotic polar solvents such as hexamethylphosphalamide and dimethyl sulfoxide. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
- Thickener When an aqueous medium is used as the liquid medium for forming the slurry, it is preferable to make a slurry using a thickener and a latex such as styrene butadiene rubber (SBR).
- a thickener is usually used to adjust the viscosity of the slurry.
- the thickener is not limited as long as the effect of the present invention is not significantly limited. Specifically, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and salts thereof Etc. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios.
- the ratio of the thickener to the positive electrode active material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further 0.6% by mass or more. It is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less.
- the content is within the above range, the coating property is improved, and further, the ratio of the active material in the positive electrode active material layer becomes sufficient, so that the problem that the battery capacity decreases and the resistance between the positive electrode active materials increases. It is easier to avoid problems.
- the positive electrode active material layer obtained by applying the slurry to the current collector and drying is preferably consolidated by a hand press, a roller press or the like.
- the density of the positive electrode active material layer is preferably 1 g ⁇ cm ⁇ 3 or more, more preferably 1.5 g ⁇ cm ⁇ 3 or more, particularly preferably 2 g ⁇ cm ⁇ 3 or more, and preferably 4 g ⁇ cm ⁇ 3 or less. 3.5 g ⁇ cm ⁇ 3 or less is more preferable, and 3 g ⁇ cm ⁇ 3 or less is particularly preferable.
- the density of the positive electrode active material layer is within the above range, the non-aqueous electrolyte solution permeation into the vicinity of the current collector / active material interface does not decrease, and the charge / discharge characteristics particularly at a high current density are good. Become. Furthermore, the electrical conductivity between the active materials is difficult to decrease, and the battery resistance is difficult to increase.
- the shape of the current collector examples include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, foam metal, etc.
- a carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred.
- the thickness of the current collector is arbitrary, but is preferably 1 ⁇ m or more, more preferably 3 ⁇ m or more, further preferably 5 ⁇ m or more, and preferably 1 mm or less, more preferably 100 ⁇ m or less, and further preferably 50 ⁇ m or less. preferable. When the thickness of the current collector is within the above range, sufficient strength required for the current collector can be ensured. Furthermore, the handleability is also improved.
- the thickness ratio between the current collector and the positive electrode active material layer is not particularly limited, but (active material layer thickness on one side immediately before non-aqueous electrolyte injection) / (current collector thickness) is preferably 150 or less, more preferably 20 or less, particularly preferably 10 or less, preferably 0.1 or more, more preferably 0.4 or more, and particularly preferably 1 or more.
- the ratio of the thickness of the current collector to the positive electrode active material layer is within the above range, the current collector hardly generates heat due to Joule heat during high current density charge / discharge. Furthermore, it becomes difficult for the volume ratio of the current collector to the positive electrode active material to increase, and a decrease in battery capacity can be prevented.
- the area of the positive electrode active material layer is preferably larger than the outer surface area of the battery outer case.
- the total electrode area of the positive electrode with respect to the surface area of the exterior of the non-aqueous electrolyte battery is preferably 20 times or more, and more preferably 40 times or more.
- the outer surface area of the outer case is the total area obtained by calculation from the vertical, horizontal, and thickness dimensions of the case part filled with the power generation element excluding the protruding part of the terminal in the case of a bottomed square shape. .
- the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder.
- the total electrode area of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and in the structure in which the positive electrode mixture layer is formed on both sides via the current collector foil. , The sum of the areas where each surface is calculated separately.
- the electric capacity (electric capacity when the battery is discharged from a fully charged state to a discharged state) of a battery element housed in one battery exterior of the non-aqueous electrolyte battery is It is preferable that it is 1 ampere hour (Ah) or more because the effect of improving the low-temperature discharge characteristics is increased. Therefore, the positive electrode plate has a fully discharged capacity, preferably 3 Ah (ampere hour) or more, more preferably 4 Ah or more, preferably 100 Ah or less, more preferably 70 Ah or less, and particularly preferably. Design to be 50 Ah or less.
- the voltage drop due to the electrode reaction resistance does not become excessive when a large current is taken out, and the deterioration of the power efficiency can be prevented. Furthermore, the temperature distribution due to the internal heat generation of the battery during pulse charge / discharge does not become too large, the durability of repeated charge / discharge is inferior, and the heat dissipation efficiency is poor against sudden heat generation during abnormalities such as overcharge and internal short circuit. The phenomenon of becoming can be avoided.
- the thickness of the positive electrode plate is not particularly limited, but from the viewpoint of high capacity, high output, and high rate characteristics, the thickness of the positive electrode active material layer minus the thickness of the current collector is relative to one side of the current collector. 10 ⁇ m or more is preferable, 20 ⁇ m or more is more preferable, 200 ⁇ m or less is preferable, and 100 ⁇ m or less is more preferable.
- a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit.
- the nonaqueous electrolytic solution of the present invention is usually used by impregnating the separator.
- the material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired.
- a resin, glass fiber, inorganic material, etc. formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a nonwoven fabric-like material having excellent liquid retention properties is used. Is preferred.
- polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
- the thickness of the separator is arbitrary, but is usually 1 ⁇ m or more, preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, and usually 50 ⁇ m or less, preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only battery performance such as rate characteristics may be lowered, but also the energy density of the entire non-aqueous electrolyte battery may be lowered.
- the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Moreover, it is 90% or less normally, 85% or less is preferable and 75% or less is more preferable. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.
- the average pore diameter of the separator is also arbitrary, but is usually 0.5 ⁇ m or less, preferably 0.2 ⁇ m or less, and usually 0.05 ⁇ m or more. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.
- oxides such as alumina and silicon dioxide
- nitrides such as aluminum nitride and silicon nitride
- sulfates such as barium sulfate and calcium sulfate are used. Things are used.
- a thin film shape such as a nonwoven fabric, a woven fabric, or a microporous film is used.
- the thin film shape those having a pore diameter of 0.01 to 1 ⁇ m and a thickness of 5 to 50 ⁇ m are preferably used.
- a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used.
- a porous layer may be formed by using alumina particles having a 90% particle size of less than 1 ⁇ m on both surfaces of the positive electrode and using a fluororesin as a binder.
- the electrode group has a laminated structure in which the positive electrode plate and the negative electrode plate are interposed via the separator, and a structure in which the positive electrode plate and the negative electrode plate are wound in a spiral shape via the separator. Either may be used.
- the ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, and 80% or less. preferable.
- the lower limit of the electrode group occupancy is preferably in the above range from the viewpoint of battery capacity.
- the upper limit of the electrode group occupancy is to secure a gap space from the viewpoint of various characteristics such as charge / discharge repetition performance as a battery and high temperature storage, and from the viewpoint of avoiding the operation of the gas release valve that releases the internal pressure to the outside.
- the above range is preferable. If there is too little gap space, the battery will become hot and the member will expand, or the vapor pressure of the electrolyte liquid component will increase and the internal pressure will rise. There are cases where a gas release valve that lowers various characteristics or further releases internal pressure to the outside is activated.
- the current collecting structure is not particularly limited, but in order to more effectively realize the improvement of the discharge characteristics by the non-aqueous electrolyte solution of the present invention, it is necessary to make the structure to reduce the resistance of the wiring part and the joint part preferable. Thus, when internal resistance is reduced, the effect of using the non-aqueous electrolyte solution of this invention is exhibited especially favorable.
- the electrode group has the above-described laminated structure
- a structure formed by bundling the metal core portions of the electrode layers and welding them to the terminals is preferably used.
- the area of one electrode increases, the internal resistance increases. Therefore, it is also preferable to reduce the resistance by providing a plurality of terminals in the electrode.
- the electrode group has the winding structure described above, the internal resistance can be lowered by providing a plurality of lead structures for the positive electrode and the negative electrode, respectively, and bundling the terminals.
- Protection elements such as PTC (Positive Temperature Coefficient), thermal fuse, thermistor, which increases resistance when abnormal heat is generated or excessive current flows, shuts off current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation And the like (current cutoff valve). It is preferable to select a protective element that does not operate under normal use at a high current. From the viewpoint of high output, it is more preferable to design the protective element so as not to cause abnormal heat generation or thermal runaway even without the protective element.
- the non-aqueous electrolyte battery of the present invention is usually configured by housing the non-aqueous electrolyte, the negative electrode, the positive electrode, the separator, and the like in an exterior body (exterior case).
- an exterior body exterior body
- limiting in this exterior body A well-known thing can be arbitrarily employ
- the material of the outer case is not particularly limited as long as it is a material that is stable to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum or an aluminum alloy, a magnesium alloy, nickel, titanium, or a metal, or a laminated film (laminated film) of a resin and an aluminum foil is preferably used.
- the metal is welded to each other by laser welding, resistance welding, ultrasonic welding, or a sealed sealing structure, or a caulking structure using the above metals through a resin gasket To do.
- the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers.
- a resin different from the resin used for the laminate film may be interposed between the resin layers.
- a metal and a resin are joined, so that a resin having a polar group or a modified group having a polar group introduced as an intervening resin is used.
- Resins are preferably used.
- the shape of the exterior body is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.
- the compound 1 corresponds to a cyclic carbonate having a carbon-carbon unsaturated bond in the present specification
- the compound 2 corresponds to a compound represented by the general formula (A) in the present specification
- the compound 3 and the compound 6 are described in the present specification.
- the compound 4 corresponds to the compound represented by the general formula (B) in the description
- the compound 4 corresponds to the compound represented by the general formula (C) in the present specification
- the compound 5 corresponds to the fluorinated salt in the present specification. Equivalent to.
- Examples 1-1 to 1-12, Comparative Examples 1-1 to 1-9> [Production of positive electrode]
- a positive electrode active material 90 parts by mass of lithium / nickel / cobalt / manganese composite oxide (Li 1.0 Ni 0.5 Co 0.2 Mn 0.3 O 2 ) and 7 parts by mass of acetylene black as a conductive material were combined.
- 3 parts by mass of polyvinylidene fluoride (PVdF) as an adhesive was mixed with a disperser in an N-methylpyrrolidone solvent to form a slurry. This was uniformly applied on both sides of a 15 ⁇ m thick aluminum foil, dried, and then pressed to obtain a positive electrode.
- PVdF polyvinylidene fluoride
- EC ethylene carbonate
- DEC diethyl carbonate
- EMC ethyl methyl carbonate
- a non-aqueous electrolyte was prepared by adding compounds 1 to 6 as additives to the reference electrolyte 1 at the contents shown in Table 1 below.
- content (mass%) in a table
- surface is content when each non-aqueous electrolyte solution is 100 mass%.
- the positive electrode, the negative electrode, and a polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element.
- the battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 ⁇ m) were coated with a resin layer while projecting positive and negative terminals, and then the non-aqueous electrolyte solution prepared above was placed in the bag. And vacuum-sealing to prepare a laminate-type non-aqueous electrolyte battery.
- the battery was discharged at 0.2 C to 2.5 V, and initial conditioning was performed.
- the battery after the initial conditioning was subjected to CC-CV charging so that the capacity of the battery was 0.2 C and half the initial discharge capacity. This was discharged at 1.0 C, 2.0 C, and 3.0 C at 25 ° C., and the voltage at 5 seconds was measured.
- the average value of the slopes of the obtained current-voltage straight lines at 1.0 C, 2.0 C, and 3.0 C was defined as the battery internal resistance.
- Examples 1-1 and 1-8 in which only Compound 1 and Compound 2 were added Examples 1-1 to 1-5, 1-7 in which Compound 3 or Compound 4 was further added at 0.49% by mass or less And 1-10 were able to greatly reduce the amount of stored charge gas, and the internal resistance could be lowered.
- Examples 1-6 and 1-12 including both Compound 3 and Compound 4 the battery characteristics could be further improved as compared with the case including either one.
- Examples 1-8 and 1-11 in which Compound 6 was added in an amount of 0.49% by mass or less instead of Compound 3 the battery characteristics could be improved as in the case of Compound 3.
- Comparative Examples 1-2 and 1-3 in which all of Compounds 1 to 3 are contained but the content of Compound 1 exceeds 1.5 mass%, the charge storage gas is different from Comparative Examples 1-1 and 1-8. Although the amount could be reduced, the improvement range of Examples 1-1 to 1-4 was not obtained, and the internal resistance increased instead. Further, in Comparative Examples 1-4, 1-5, and 1-9 that contain all of Compounds 1 to 3 but the content of Compound 3 or Compound 4 exceeds 0.49% by mass, the charge storage gas amount is that of Example 1. Although the improvement range equivalent to -1 to 1-4 and 1-7 was obtained, the internal resistance was the same or increased compared to Comparative Examples 1-1 and 1-8.
- Comparative Examples 1-6 and 1-7 containing Compound 3 at 0.49% by mass or less but containing only Compound 1 or Compound 2 the charge storage gas amount was as in Example 1. Although an improvement range equivalent to -1 to 1-4 was obtained, the internal resistance was rather increased compared to Comparative Examples 1-1 and 1-8.
- Example 2-1 [Production of positive electrode] Lithium / nickel / cobalt / manganese composite oxide (Li 1.0 Ni 0.6 Co 0.2 Mn 0.2 O 2 ) 94 parts by mass as a positive electrode active material and 3 parts by mass of acetylene black as a conductive material 3 parts by mass of polyvinylidene fluoride (PVdF) as an adhesive was mixed with a disperser in an N-methylpyrrolidone solvent to form a slurry. This was uniformly applied on both sides of a 15 ⁇ m thick aluminum foil, dried, and then pressed to obtain a positive electrode.
- PVdF polyvinylidene fluoride
- a negative electrode was prepared and used in the same manner as in Example 1-1.
- a non-aqueous electrolyte was prepared by adding compounds 1 to 4 as additives to the reference electrolyte 1 at the contents shown in Table 2 below.
- content (mass%) in a table
- surface is content when each non-aqueous electrolyte solution is 100 mass%.
- the positive electrode, the negative electrode, and a polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element.
- the battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 ⁇ m) were coated with a resin layer while projecting positive and negative terminals, and then the non-aqueous electrolyte solution prepared above was placed in the bag. And vacuum-sealing to prepare a laminate-type non-aqueous electrolyte battery.
- Example 3-1 Lithium / nickel / manganese / cobalt composite oxide (Li 1.0 Ni 0.33 Co 0.33 Mn 0.33 O 2 ) 85% by mass as a positive electrode active material and 10% by mass of acetylene black as a conductive material
- PVDF polyvinylidene fluoride
- the fired product obtained was further pulverized with a hammer mill and then sieved (45 ⁇ m) to prepare a negative electrode active material.
- the content of Si element, the average particle diameter d50, the tap density, and the specific surface area of this negative electrode active material measured by the above measurement methods were 2.0 mass%, 20 ⁇ m, 1.0 g / cm 3 , and 7.2 m 2, respectively. / G.
- a non-aqueous electrolyte solution was prepared by adding compounds 1 to 4 as additives to the reference electrolyte solution 1 at the contents shown in Table 3 below.
- content (mass%) in a table
- surface is content when each non-aqueous electrolyte solution is 100 mass%.
- the positive electrode, the negative electrode, and a polyethylene separator were laminated in the order of the negative electrode, the separator, and the positive electrode to prepare a battery element.
- the battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 ⁇ m) were coated with a resin layer while projecting positive and negative terminals, and then the non-aqueous electrolyte solution prepared above was placed in the bag. And vacuum-sealing to prepare a laminate-type non-aqueous electrolyte battery.
- the non-aqueous electrolyte solution of the present invention the amount of gas generated during high-temperature storage of a non-aqueous electrolyte battery can be improved and the battery resistance can be reduced.
- the non-aqueous electrolyte solution of the present invention and the non-aqueous electrolyte battery using the non-aqueous electrolyte solution can be used for various known applications using the non-aqueous electrolyte battery. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, etc.
- Walkie Talkie Electronic Notebook, Calculator, Memory Card, Portable Tape Recorder, Radio, Backup Power Supply, Motor, Bike, Motorbike, Bicycle, Lighting Equipment, Toy, Game Equipment, Clock, Electric Tool, Strobe, Camera, Home Backup Examples include power supplies, business-use backup power supplies, load leveling power supplies, natural energy storage power supplies, and lithium ion capacitors.
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Abstract
Description
特許文献2には、非水系電解液に特定の亜リン酸エステル化合物と重合性官能基を分子内に1個有する化合物を含有させることにより、サイクル試験における容量維持率の改善、及び電解液の難燃性を向上させる検討が開示されている。
特許文献3には、一定量の水分を含んだ正極と、イソシアナート化合物、及びイミド塩を含有する非水系電解液を組み合わせることにより、イソシアナート化合物が正極中の水分を低下させ、且つ、イソシアナート化合物と、イミド塩が負極に好適な被膜を形成することでサイクル試験における容量維持率と、電池膨れを改善する検討が開示されている。
特許文献4には、非水系電解液に特定のイソシアナート化合物を含有させることにより、85℃保存試験における電池膨れを改善する検討が開示されている。
[1] 下記一般式(A)で表される化合物、炭素‐炭素不飽和結合を有する環状カーボネート、並びに下記一般式(B)及び下記一般式(C)で表される化合物からなる群より選ばれる少なくとも一種の化合物を含有する非水系電解液であって、
該炭素‐炭素不飽和結合を有する環状カーボネートの該非水系電解液全体に対する含有量が0.01質量%以上1.5質量%以下であり、
該一般式(B)及び該一般式(C)で表される化合物のいずれか一方のみを含有する場合は、該一般式(B)又は該一般式(C)で表される化合物の該非水系電解液全体に対する含有量が0.01質量%以上0.49質量%以下であり、
該一般式(B)及び該一般式(C)で表される化合物の両方を含有する場合は、該一般式(B)及び該一般式(C)で表される化合物全体の該非水系電解液全体に対する含有量が0.01質量%以上0.80質量%以下である、非水系電解液。
(式(A)中、m、nは、それぞれ独立に、1~3の整数を示す。)
(式(B)中、R1~R3は、互いに同一であっても異なっていてもよく、置換基を有していてもよい炭素数1~10の炭化水素基である。但し、R1~R3のうち少なくとも1つは炭素-炭素不飽和結合を有する炭化水素基である。)
(式(C)中、Qは、炭素数3~20の炭化水素基であり、該炭化水素基はシクロアルキレン基を有する。)
[2] 前記一般式(B)中、炭素-炭素不飽和結合を有する炭化水素基がアリル基又はメタリル基である、[1]に記載の非水系電解液。
[3] 前記非水系電解液が、さらにフッ素原子を有する環状カーボネートを含有する、[1]又は[2]に記載の非水系電解液。
[4] 前記フッ素原子を有する環状カーボネートの含有量が、非水系電解液の全量に対して0.01質量%以上5質量%以下である、[3]に記載の非水系電解液。
[5] 前記非水系電解液が、さらにフッ素化された塩及びオキサラート塩からなる群より選ばれる少なくとも1種の塩を含有する、[1]乃至[4]のいずれかに記載の非水系電解液。
[6] 前記フッ素化された塩及び/又は前記オキサラート塩の含有量が、非水系電解液の全量に対して0.01質量%以上5質量%以下である、[5]に記載の非水系電解液。
[7] 金属イオンを吸蔵及び放出可能な正極及び負極と、非水系電解液とを備えた非水系電解液電池であって、該非水系電解液が[1]乃至[6]のいずれかに記載の非水系電解液である、非水系電解液電池。
[8] 前記正極に含まれる正極活物質が、下記組成式(1)で表される金属酸化物である、[7]に記載の非水系電解液電池。
Lia1Nib1Coc1Md1O2・・・(1)
(上記式(1)中、a1、b1、c1及びd1は、0.90≦a1≦1.10、0.50≦b1≦0.98、0.01≦c1<0.50、0.01≦d1<0.50の数値を示し、b1+c1+d1=1を満たす。MはMn、Al、Mg、Zr、Fe、Ti及びErからなる群より選ばれる少なくとも1種の元素を表す。)
[9] 前記負極が、Liと合金化可能な金属粒子と、黒鉛とを含有する負極活物質を含む、[7]又は[8]に記載の非水系電解液電池。
[10] 前記Liと合金化可能な金属粒子が、Si、Sn、As、Sb、Al、Zn及びWからなる群より選ばれる少なくとも1種の金属を含む金属粒子である、[9]に記載の非水系電解液電池。
[11] 前記Liと合金化可能な金属粒子が、Si又はSi金属酸化物である、[9]に記載の非水系電解液電池。
[12] 前記Liと合金化可能な金属粒子と、黒鉛とを含有する負極活物質が、金属粒子と黒鉛粒子との複合体及び/又は混合物である、[9]~[11]のいずれかに記載の非水系電解液電池。
[13] 前記Liと合金化可能な金属粒子と、黒鉛とを含有する負極活物質の合計に対する、前記Liと合金化可能な金属粒子の含有量が、0.1質量%以上25質量%以下である、[9]~[12]のいずれかに記載の非水系電解液電池。
<1-1.一般式(A)で表される化合物>
本発明の非水系電解液は下記一般式(A)で表される化合物を含有する。
(m、n)=(1、1)、(1、2)、(1、3)、(2、1)、(2、2)、(2、3)、(3、1)、(3、2)、(3、3)が挙げられる。
中でも好ましくは、(m、n)=(1、1)、(1、2)、(1、3)、(2、1)、(2、2)、(3、1)が挙げられ、より好ましくは、(m、n)=(1、1)、(1、2)、(2、1)、(2、2)が挙げられ、さらに好ましくは、(m、n)=(1、1)、(1、2)が挙げられる。
本発明の非水系電解液に含有される炭素-炭素不飽和結合を有する環状カーボネート(以下、「不飽和環状カーボネート」と記載する場合がある)としては、炭素-炭素二重結合または炭素-炭素三重結合を有する環状カーボネートであれば、特に制限はなく、任意の不飽和カーボネートを用いることができる。なお、芳香環を有する環状カーボネートも、不飽和環状カーボネートに包含されることとする。
ビニレンカーボネート類としては、
ビニレンカーボネート、メチルビニレンカーボネート、4,5-ジメチルビニレンカーボネート、フェニルビニレンカーボネート、4,5-ジフェニルビニレンカーボネート、ビニルビニレンカーボネート、4,5-ジビニルビニレンカーボネート、アリルビニレンカーボネート、4,5-ジアリルビニレンカーボネート、4-フルオロビニレンカーボネート、4-フルオロ-5-メチルビニレンカーボネート、4-フルオロ-5-フェニルビニレンカーボネート、4-フルオロ-5-ビニルビニレンカーボネート、4-アリル-5-フルオロビニレンカーボネート等が挙げられる。
ビニルエチレンカーボネート、4,5-ジビニルエチレンカーボネート、4-メチル-5-ビニルエチレンカーボネート、4-アリル-5-ビニルエチレンカーボネート、エチニルエチレンカーボネート、4,5-ジエチニルエチレンカーボネート、4-メチル-5-エチニルエチレンカーボネート、4-ビニル-5-エチニルエチレンカーボネート、4-アリル-5-エチニルエチレンカーボネート、フェニルエチレンカーボネート、4,5-ジフェニルエチレンカーボネート、4-フェニル-5-ビニルエチレンカーボネート、4-アリル-5-フェニルエチレンカーボネート、アリルエチレンカーボネート、4,5-ジアリルエチレンカーボネート、4-メチル-5-アリルエチレンカーボネート等が挙げられる。
ビニレンカーボネート、メチルビニレンカーボネート、4,5-ジメチルビニレンカーボネート、ビニルビニレンカーボネート、4,5-ビニルビニレンカーボネート、アリルビニレンカーボネート、4,5-ジアリルビニレンカーボネート、ビニルエチレンカーボネート、4,5-ジビニルエチレンカーボネート、4-メチル-5-ビニルエチレンカーボネート、アリルエチレンカーボネート、4,5-ジアリルエチレンカーボネート、4-メチル-5-アリルエチレンカーボネート、4-アリル-5-ビニルエチレンカーボネート、エチニルエチレンカーボネート、4,5-ジエチニルエチレンカーボネート、4-メチル-5-エチニルエチレンカーボネート、4-ビニル-5-エチニルエチレンカーボネートが挙げられる。
不飽和環状カーボネートの分子量は、特に制限されず、本発明の効果を著しく損なわない限り任意である。分子量は、好ましくは、80以上、250以下である。この範囲であれば、非水系電解液に対する不飽和環状カーボネートの溶解性を確保しやすく、本発明の効果が十分に発現されやすい。不飽和環状カーボネートの分子量は、より好ましくは85以上であり、また、より好ましくは150以下である。不飽和環状カーボネートの製造方法は、特に制限されず、公知の方法を任意に選択して製造することが可能である。また、市販品を入手して使用してもよい。
本発明の非水系電解液は前記一般式(B)及び下記一般式(C)で表される化合物からなる群より選ばれる少なくとも一種の化合物を含有する。
本発明の非水系電解液が一般式(B)で表される化合物及び一般式(C)で表される化合物の両方を含む場合、本発明の非水系電解液全体に対する一般式(B)で表される化合物及び一般式(C)で表される化合物全体の含有量は、非水系電解液100質量%中、0.01質量%以上、、好ましくは0.05質量%以上、さらに好ましくは0.10質量%以上、特に好ましくは0.20質量%以上であり、また、0.80質量%以下、好ましくは0.70質量%以下、より好ましくは0.60質量%以下、さらに好ましくは0.50質量%以下、特に好ましくは0.40質量%以下である。
この問題に対し、本発明では炭素‐炭素不飽和結合を有する環状カーボネートと一般式(B)及び/又は(C)で表される化合物の添加量を好適に調節することで、初期充電時に上述の反応を十分に進行させ、高温保存時に還元分解物と一般式(B)及び/又は(C)で表される化合物の過剰反応の制御に成功した。また、一般式(B)及び(C)で表される化合物が有する反応部位はそれぞれ反応種が異なる。例えば、一般式(B)で表される化合物は炭素‐炭素不飽和結合を有する環状カーボネートが還元分解し生成するラジカル種と、一般式(C)で表される化合物はアニオン種と反応すると想定する。そのため、一般式(B)、(C)で表される化合物を併用すると還元分解物のラジカル種、アニオン種の両方が被膜形成反応に関与するため、一般式(B)、(C)で表される化合物を単独で添加した場合よりも、さらに好適な被膜が形成される。これにより、高温保存におけるガス発生の抑制だけでなく、電池抵抗の増加抑制の両方を改善することを見出した。
本発明の非水系電解液は、さらに、フッ素原子を有する環状カーボネートを含有することが好ましい。
フッ素原子を有する環状カーボネートとしては、炭素原子数2~6のアルキレン基を有する環状カーボネートのフッ素化物、及びその誘導体が挙げられ、例えばエチレンカーボネートのフッ素化物、及びその誘導体が挙げられる。エチレンカーボネートのフッ素化物の誘導体としては、例えば、アルキル基(例えば、炭素原子数1~4個のアルキル基)で置換されたエチレンカーボネートのフッ素化物が挙げられる。中でもフッ素原子を1~8個有するエチレンカーボネート、及びその誘導体が好ましい。
モノフルオロエチレンカーボネート、4,4-ジフルオロエチレンカーボネート、4,5-ジフルオロエチレンカーボネート、4-フルオロ-4-メチルエチレンカーボネート、4,5-ジフルオロ-4-メチルエチレンカーボネート、4-フルオロ-5-メチルエチレンカーボネート、4,4-ジフルオロ-5-メチルエチレンカーボネート、4-(フルオロメチル)-エチレンカーボネート、4-(ジフルオロメチル)-エチレンカーボネート、4-(トリフルオロメチル)-エチレンカーボネート、4-(フルオロメチル)-4-フルオロエチレンカーボネート、4-(フルオロメチル)-5-フルオロエチレンカーボネート、4-フルオロ-4,5-ジメチルエチレンカーボネート、4,5-ジフルオロ-4,5-ジメチルエチレンカーボネート、4,4-ジフルオロ-5,5-ジメチルエチレンカーボネート等が挙げられる。
フッ素原子を有する環状カーボネート化合物は、1種を単独で用いてもよく、2種以上を任意の組み合わせ及び比率で併用してもよい。
本発明の非水系電解液は、さらに、フッ素化された塩及びオキサラート塩からなる群より選ばれる少なくとも1種の塩を含有することが好ましい。
<1-6-1.フッ素化された塩>
本発明の非水系電解液に用いることができるフッ素化された塩に特に制限はないが、構造内に脱離性の高いフッ素原子を有しているため、例えば、一般式(A)で表される化合物が還元反応を受け生成するアニオン(求核種)と好適に反応し、複合的被膜を形成することができることから、ジフルオロリン酸塩、フルオロスルホン酸塩、及びビスフルオロスルホニルイミド構造を有する塩が好ましい。フッ素原子の脱離性が特に高いこと、求核種との反応が好適に進行することから、ジフルオロリン酸塩、フルオロスルホン酸塩がより好ましい。以下、これらの各種塩について説明する。
ジフルオロリン酸塩のカウンターカチオンとしては特に限定はないが、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、マグネシウム、カルシウム、バリウム、及び、NR13R14R15R16(式中、R13~R16は、各々独立に、水素原子又は炭素数1~12の有機基を表わす。)で表されるアンモニウム等がその例として挙げられる。
ジフルオロリン酸リチウム、ジフルオロリン酸ナトリウム、ジフルオロリン酸カリウム等が挙げられ、ジフルオロリン酸リチウムが好ましい。
フルオロスルホン酸塩のカウンターカチオンとしては前記ジフルオロリン酸塩の場合と同様である。
フルオロスルホン酸リチウム、フルオロスルホン酸ナトリウム、フルオロスルホン酸カリウム、フルオロスルホン酸ルビジウム、フルオロスルホン酸セシウム等が挙げられ、フルオロスルホン酸リチウムが好ましい。
この範囲内であれば、充放電に伴う非水系電解液電池の膨れを好適に抑制できる。
ビスフルオロスルホニルイミド構造を有する塩のカウンターカチオンとしては前記ジフルオロリン酸塩の場合と同様である。
リチウムビスフルオロスルホニルイミド、ナトリウムビスフルオロスルホニルイミド、カリウムビスフルオロスルホニルイミド等が挙げられ、リチウムビスフルオロスルホニルイミドが好ましい。
この範囲内であれば、充放電に伴う非水系電解液電池の膨れを好適に抑制できる。
オキサラート塩のカウンターカチオンとしては前記ジフルオロリン酸塩の場合と同様である。
リチウムジフルオロオキサラトボレート、リチウムビス(オキサラト)ボレート、リチウムテトラフルオロオキサラトフォスフェート、リチウムジフルオロビス(オキサラト)フォスフェート、リチウムトリス(オキサラト)フォスフェート等が挙げられ、
リチウムビス(オキサラト)ボレート、リチウムジフルオロビス(オキサラト)フォスフェートが好ましい。
本発明の非水系電解液は、一般的な非水系電解液と同様、通常はその成分として、電解質を含有する。本発明の非水系電解液に用いられる電解質について特に制限は無く、公知の電解質を用いることができる。以下、電解質の具体例について詳述する。
<リチウム塩>
本発明の非水系電解液における電解質としては、通常、リチウム塩が用いられる。リチウム塩としては、この用途に用いることが知られているものであれば特に制限がなく、任意のものを用いることができ、具体的には以下のものが挙げられる。
LiPF6等のフルオロリン酸リチウム塩類;
LiWOF5等のタングステン酸リチウム塩類;
HCO2Li、CH3CO2Li、CH2FCO2Li、CHF2CO2Li、CF3CO2Li、CF3CH2CO2Li、CF3CF2CO2Li、CF3CF2CF2CO2Li、CF3CF2CF2CF2CO2Li等のカルボン酸リチウム塩類;
CH3SO3Li等のスルホン酸リチウム塩類;
LiN(FCO2)2、LiN(FCO)(FSO2)、LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2、リチウム環状1,2-パーフルオロエタンジスルホニルイミド、リチウム環状1,3-パーフルオロプロパンジスルホニルイミド、LiN(CF3SO2)(C4F9SO2)等のリチウムイミド塩類;
LiC(FSO2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3等のリチウムメチド塩類;
リチウムジフルオロオキサラトボレート、リチウムビス(オキサラト)ボレート、リチウムテトラフルオロオキサラトフォスフェート、リチウムジフルオロビス(オキサラト)フォスフェート、リチウムトリス(オキサラト)フォスフェート等のリチウムオキサラート塩類;
その他、LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF3CF3、LiBF3C2F5、LiBF3C3F7、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2等の含フッ素有機リチウム塩類;
等が挙げられる。
本発明の非水系電解液は、一般的な非水系電解液と同様、通常はその主成分として、上述した電解質を溶解する非水溶媒を含有する。ここで用いる非水溶媒について特に制限はなく、公知の有機溶媒を用いることができる。有機溶媒としては、飽和環状カーボネート、鎖状カーボネート、エーテル系化合物、スルホン系化合物等が挙げられるが、これらに特に限定されない。これらは、1種を単独で又は2種以上を組み合わせて用いることができる。
飽和環状カーボネートとしては、通常炭素数2~4のアルキレン基を有するものが挙げられ、リチウムイオン解離度の向上に由来する電池特性向上の点から炭素数2~3の飽和環状カーボネートが好ましく用いられる。
尚、本発明における体積%とは25℃、1気圧における体積を意味する。
鎖状カーボネートとしては、通常炭素数3~7のものが用いられ、電解液の粘度を適切な範囲に調整するために、炭素数3~5の鎖状カーボネートが好ましく用いられる。
エーテル系化合物としては、炭素数3~10の鎖状エーテル、及び炭素数3~6の環状エーテルが好ましい。
炭素数3~10の鎖状エーテルとしては、ジエチルエーテル、ジ(2-フルオロエチル)エーテル、ジ(2,2-ジフルオロエチル)エーテル、ジ(2,2,2-トリフルオロエチル)エーテル、エチル(2-フルオロエチル)エーテル、エチル(2,2,2-トリフルオロエチル)エーテル、エチル(1,1,2,2-テトラフルオロエチル)エーテル、(2-フルオロエチル)(2,2,2-トリフルオロエチル)エーテル、(2-フルオロエチル)(1,1,2,2-テトラフルオロエチル)エーテル、(2,2,2-トリフルオロエチル)(1,1,2,2-テトラフルオロエチル)エーテル、エチル-n-プロピルエーテル、エチル(3-フルオロ-n-プロピル)エーテル、エチル(3,3,3-トリフルオロ-n-プロピル)エーテル、エチル(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、エチル(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、2-フルオロエチル-n-プロピルエーテル、(2-フルオロエチル)(3-フルオロ-n-プロピル)エーテル、(2-フルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(2-フルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2-フルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、2,2,2-トリフルオロエチル-n-プロピルエーテル、(2,2,2-トリフルオロエチル)(3-フルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2,2,2-トリフルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、1,1,2,2-テトラフルオロエチル-n-プロピルエーテル、(1,1,2,2-テトラフルオロエチル)(3-フルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(1,1,2,2-テトラフルオロエチル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ-n-プロピルエーテル、(n-プロピル)(3-フルオロ-n-プロピル)エーテル、(n-プロピル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(3-フルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(3,3,3-トリフルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(3-フルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(3,3,3-トリフルオロ-n-プロピル)エーテル、(3,3,3-トリフルオロ-n-プロピル)(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(3,3,3-トリフルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(2,2,3,3-テトラフルオロ-n-プロピル)エーテル、(2,2,3,3-テトラフルオロ-n-プロピル)(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ(2,2,3,3,3-ペンタフルオロ-n-プロピル)エーテル、ジ-n-ブチルエーテル、ジメトキシメタン、エトキシメトキシメタン、メトキシ(2-フルオロエトキシ)メタン、メトキシ(2,2,2-トリフルオロエトキシ)メタン、メトキシ(1,1,2,2-テトラフルオロエトキシ)メタン、ジエトキシメタン、エトキシ(2-フルオロエトキシ)メタン、エトキシ(2,2,2-トリフルオロエトキシ)メタン、エトキシ(1,1,2,2-テトラフルオロエトキシ)メタン、ジ(2-フルオロエトキシ)メタン、(2-フルオロエトキシ)(2,2,2-トリフルオロエトキシ)メタン、(2-フルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)メタン、ジ(2,2,2-トリフルオロエトキシ)メタン、(2,2,2-トリフルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)メタン、ジ(1,1,2,2-テトラフルオロエトキシ)メタン、ジメトキシエタン、メトキシエトキシエタン、メトキシ(2-フルオロエトキシ)エタン、メトキシ(2,2,2-トリフルオロエトキシ)エタン、メトキシ(1,1,2,2-テトラフルオロエトキシ)エタン、ジエトキシエタン、エトキシ(2-フルオロエトキシ)エタン、エトキシ(2,2,2-トリフルオロエトキシ)エタン、エトキシ(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(2-フルオロエトキシ)エタン、(2-フルオロエトキシ)(2,2,2-トリフルオロエトキシ)エタン、(2-フルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(2,2,2-トリフルオロエトキシ)エタン、(2,2,2-トリフルオロエトキシ)(1,1,2,2-テトラフルオロエトキシ)エタン、ジ(1,1,2,2-テトラフルオロエトキシ)エタン、エチレングリコールジ-n-プロピルエーテル、エチレングリコールジ-n-ブチルエーテル、ジエチレングリコールジメチルエーテル等が挙げられる。
これらの中でも、ジメトキシメタン、ジエトキシメタン、エトキシメトキシメタン、エチレングリコールジ-n-プロピルエーテル、エチレングリコールジ-n-ブチルエーテル、ジエチレングリコールジメチルエーテルが、リチウムイオンへの溶媒和能力が高く、イオン解離性を向上させる点で好ましい。特に好ましくは、粘性が低く、高いイオン伝導度を与えることから、ジメトキシメタン、ジエトキシメタン、エトキシメトキシメタンである。
エーテル系化合物の含有量は、特に制限されず、本発明の効果を著しく損なわない限り任意であるが、非水溶媒100体積%中、通常1体積%以上、好ましくは2体積%以上、より好ましくは3体積%以上、また、通常30体積%以下、好ましくは25体積%以下、より好ましくは20体積%以下である。エーテル系化合物を2種以上併用する場合には、エーテル系化合物の合計量が上記範囲を満たすようにすればよい。エーテル系化合物の含有量が前記好ましい範囲内であれば、鎖状エーテルのリチウムイオン解離度の向上と粘度低下に由来するイオン伝導度の向上効果を確保しやすい。また、負極活物質が炭素質材料の場合、鎖状エーテルがリチウムイオンと共に共挿入される現象を抑制できることから、入出力特性や充放電レート特性を適正な範囲とすることができる。
スルホン系化合物としては、環状スルホン、鎖状スルホンであっても特に制限されないが、環状スルホンの場合、通常炭素数が3~6、好ましくは炭素数が3~5であり、鎖状スルホンの場合、通常炭素数が2~6、好ましくは炭素数が2~5である化合物が好ましい。また、スルホン系化合物1分子中のスルホニル基の数は、特に制限されないが、通常1又は2である。
スルホン系化合物の含有量は、特に制限されず、本発明の効果を著しく損なわない限り任意であるが、非水系電解液の溶媒全量に対して、通常0.3体積%以上、好ましくは0.5体積%以上、より好ましくは1体積%以上であり、また、通常40体積%以下、好ましくは35体積%以下、より好ましくは30体積%以下である。スルホン系化合物を2種以上併用する場合には、スルホン系化合物の合計量が上記範囲を満たすようにすればよい。スルホン系化合物の含有量が前記範囲内であれば、高温保存安定性に優れた電解液が得られる傾向にある。
本発明の非水系電解液において、本発明の効果を奏する範囲で以下の助剤を含有してもよい。
エリスリタンカーボネート、スピロ-ビス-ジメチレンカーボネート、メトキシエチル-メチルカーボネート等のカーボネート化合物;
メチル-2-プロピニルオギザレート、エチル-2-プロピニルオギザレート、ビス(2-プロピニル)オギザレート、2-プロピニルアセテート、2-プロピニルホルメート、2-プロピニルメタクリレート、ジ(2-プロピニル)グルタレート、メチル-2-プロピニルカーボネート、エチル-2-プロピニルカーボネート、ビス(2-プロピニル)カーボネート、2-ブチン-1,4-ジイル-ジメタンスルホネート、2-ブチン-1,4-ジイル-ジエタンスルホネート、2-ブチン-1,4-ジイル-ジホルメート、2-ブチン-1,4-ジイル-ジアセテート、2-ブチン-1,4-ジイル-ジプロピオネート、4-ヘキサジイン-1,6-ジイル-ジメタンスルホネート、2-プロピニル-メタンスルホネート、1-メチル-2-プロピニル-メタンスルホネート、1,1-ジメチル-2-プロピニル-メタンスルホネート、2-プロピニル-エタンスルホネート、2-プロピニル-ビニルスルホネート、2-プロピニル-2-(ジエトキシホスホリル)アセテート、1-メチル-2-プロピニル-2-(ジエトキシホスホリル)アセテート、1,1-ジメチル-2-プロピニル-2-(ジエトキシホスホリル)アセテート等の三重結合含有化合物;
2,4,8,10-テトラオキサスピロ[5.5]ウンデカン、3,9-ジビニル-2,4,8,10-テトラオキサスピロ[5.5]ウンデカン等のスピロ化合物;
エチレンサルファイト、フルオロスルホン酸メチル、フルオロスルホン酸エチル、メタンスルホン酸メチル、メタンスルホン酸エチル、ブスルファン、スルホレン、硫酸エチレン、硫酸ビニレン、ジフェニルスルホン、N,N-ジメチルメタンスルホンアミド、N,N-ジエチルメタンスルホンアミド、メチル硫酸トリメチルシリル、エチル硫酸トリメチルシリル、2-プロピニル-トリメチルシリルスルフェート等の含硫黄化合物;
2-イソシアナトエチルアクリレート、2-イソシアナトエチルメタクリレート、2-イソシアナトエチルクロトネート、2-(2-イソシアナトエトキシ)エチルアクリレート、2-(2-イソシアナトエトキシ)エチルメタクリレート、2-(2-イソシアナトエトキシ)エチルクロトネート等のイソシアネート化合物;
1-メチル-2-ピロリジノン、1-メチル-2-ピペリドン、3-メチル-2-オキサゾリジノン、1,3-ジメチル-2-イミダゾリジノン及びN-メチルスクシンイミド等の含窒素化合物;
ヘプタン、オクタン、ノナン、デカン、シクロヘプタン等の炭化水素化合物;
フルオロベンゼン、ジフルオロベンゼン、ヘキサフルオロベンゼン、ベンゾトリフルオライド、オルトフルオロトルエン、メタフルオロトルエン、パラフルオロトルエン、1,2-ビス(トリフルオロメチル)ベンゼン、1-トリフルオロメチル-2-ジフルオロメチルベンゼン、1,3-ビス(トリフルオロメチル)ベンゼン、1-トリフルオロメチル-3-ジフルオロメチルベンゼン、1,4-ビス(トリフルオロメチル)ベンゼン、1-トリフルオロメチル-4-ジフルオロメチルベンゼン、1,3,5-トリス(トリフルオロメチル)ベンゼン、ペンタフルオロフェニルメタンスルホネート、ペンタフルオロフェニルトリフルオロメタンスルホネート、酢酸ペンタフルオロフェニル、トリフルオロ酢酸ペンタフルオロフェニル、メチルペンタフルオロフェニルカーボネート等の含フッ素芳香族化合物;
ホウ酸トリス(トリメチルシリル)、ホウ酸トリス(トリメトキシシリル)、リン酸トリス(トリメチルシリル)、リン酸トリス(トリメトキシシリル)、ジメトキシアルミノキシトリメトキシシラン、ジエトキシアルミノキシトリエトキシシラン、ジプロポキシアルミノキシトリエトキシシラン、ジブトキシアルミノキシトリメトキシシラン、ジブトキシアルミノキシトリエトキシシラン、チタンテトラキス(トリメチルシロキシド)、チタンテトラキス(トリエチルシロキシド)、
等のシラン化合物;
2-(メタンスルホニルオキシ)プロピオン酸2-プロピニル、2-(メタンスルホニルオキシ)プロピオン酸2-メチル、2-(メタンスルホニルオキシ)プロピオン酸2-エチル、メタンスルホニルオキシ酢酸2-プロピニル、メタンスルホニルオキシ酢酸2-メチル、メタンスルホニルオキシ酢酸2-エチル等のエステル化合物;
リチウムエチルメチルオキシカルボニルホスホネート、リチウムエチルエチルオキシカルボニルホスホネート、リチウムエチル-2-プロピニルオキシカルボニルホスホネート、リチウムエチル-1-メチル-2-プロピニルオキシカルボニルホスホネート、リチウムエチル-1,1-ジメチル-2-プロピニルオキシカルボニルホスホネート等のリチウム塩;
等が挙げられる。これらは1種を単独で用いても、2種以上を併用してもよい。これらの助剤を添加することにより、高温保存後の容量維持特性やサイクル特性を向上させることができる。
本発明の非水系電解液電池は、集電体及び該集電体上に設けられた正極活物質層を有する正極と、集電体及び該集電体上に設けられた負極活物質層を有しかつ金属イオンを吸蔵及び放出し得る負極と、上述した本発明の非水系電解液とを備えるものである。
本発明の非水系電解液電池は、上述した本発明の非水系電解液以外の構成については、従来公知の非水系電解液電池と同様である。通常は、本発明の非水系電解液が含浸されている多孔膜(セパレータ)を介して正極と負極とが積層され、これらがケース(外装体)に収納された形態を有する。従って、本発明の非水系電解液電池の形状は特に制限されるものではなく、円筒型、角形、ラミネート型、コイン型、大型等の何れであってもよい。
非水系電解液としては、上述の本発明の非水系電解液を用いる。なお、本発明の趣旨を逸脱しない範囲において、本発明の非水系電解液に対し、その他の非水系電解液を配合して用いることも可能である。
以下に負極に使用される負極活物質について述べる。負極活物質としては、電気化学的に金属イオンを吸蔵・放出可能なものであれば、特に制限はない。具体例としては、炭素質材料などの構成元素として炭素を有するもの、合金系材料等が挙げられる。これらは1種を単独で用いてもよく、また2種以上を任意に組み合わせて併用してもよい。
負極活物質としては、前記の通り炭素質材料、合金系材料等が挙げられる。
より好ましくはアルミニウム、ケイ素及びスズの単体金属及びこれら原子を含む合金又は化合物であり、
更に好ましくはケイ素及びスズの単体金属及びこれら原子を含む合金又は化合物などの、ケイ素又はスズを構成元素として有るものである。
これらは、1種を単独で用いてもよく、2種以上を任意の組み合わせ及び比率で併用してもよい。
リチウム合金を形成する単体金属及び合金、又はそれらの酸化物、炭化物、窒化物、ケイ化物、硫化物若しくはリン化物等の化合物を負極活物質として使用する場合、Liと合金化可能な金属は、粒子形態である。金属粒子が、Liと合金化可能な金属粒子であることを確認するための手法としては、X線回折による金属粒子相の同定、電子顕微鏡による粒子構造の観察及び元素分析、蛍光X線による元素分析等が挙げられる。
Liと合金化可能な金属粒子の含有酸素量は、特に制限はないが、通常0.01質量%以上8質量%以下であり、0.05質量%以上5質量%以下であることが好ましい。粒子内の酸素分布状態は、表面近傍に存在、粒子内部に存在、粒子内一様に存在のいずれでもかまわないが、特に表面近傍に存在していることが好ましい。Liと合金化可能な金属粒子の含有酸素量が前記範囲内であると、金属粒子とO(酸素原子)との強い結合により、非水系電解液二次充放電に伴う体積膨張が抑制され、サイクル特性に優れるので好ましい。
負極活物質は、Liと合金化可能な金属粒子と黒鉛粒子とを含有するものであってもよい。その負極活物質とは、Liと合金化可能な金属粒子と黒鉛粒子とが互いに独立した粒子の状態で混合されている混合物でもよいし、Liと合金化可能な金属粒子が黒鉛粒子の表面及び/又は内部に存在している複合体でもよい。
Liと合金化可能な金属粒子と黒鉛粒子の合計に対するLiと合金化可能な金属粒子の含有割合は、通常0.1質量%以上、好ましくは0.5質量%以上、より好ましくは、1.0質量%以上、更に好ましくは2.0質量%以上である。また、通常99質量%以下、好ましくは50質量%以下、より好ましくは40質量%以下、更に好ましくは30質量%以下、より更に好ましくは25質量%以下、より更に好ましくは20質量%以下、特に好ましくは15質量%以下、最も好ましくは10質量%以下である。この範囲であると、Si表面での副反応の制御が可能であり、非水系電解液電池において十分な容量を得ることが可能となる点で好ましい。
本発明の負極活物質は、炭素質物又は黒鉛質物で被覆されていてもよい。この中でも非晶質炭素質物で被覆されていることが、リチウムイオンの受入性の点から好ましい。この被覆率は、通常0.5%以上30%以下、好ましくは1%以上25%以下、より好ましくは、2%以上20%以下である。被覆率の上限は、電池を組んだ際の可逆容量の観点から、被覆率の下限は、核となる炭素質材料が非晶質炭素によって均一にコートされ強固な造粒がされるという観点、焼成後に粉砕した際、得られる粒子の粒径の観点から、上記範囲とすることが好ましい。
負極活物質の内部間隙率は通常1%以上、好ましくは3%以上、より好ましく5%以上、更に好ましくは7%以上である。また通常50%未満、好ましくは40%以下、より好ましくは30%以下、更に好ましくは20%以下である。この内部間隙率が小さすぎると、非水系電解液電池において負極活物質の粒子内の液量が少なくなる傾向がある。一方、内部間隙率が大きすぎると、電極にした場合に粒子間間隙が少なくなる傾向にある。内部間隙率の下限は充放電特性の観点から、上限は非水系電解液の拡散の観点から上記範囲とすることが好ましい。また、上述したように、この間隙は空隙であってもよいし、、非晶質炭素や黒鉛質物、樹脂等、Liと合金化可能な金属粒子の膨張、収縮を緩衝するような物質が、間隙中に存在又は間隙がこれらにより満たされていてもよい。
負極の製造は、本発明の効果を著しく損なわない限り、公知のいずれの方法をも用いることができる。例えば、負極活物質に、結着剤、溶媒、必要に応じて、増粘剤、導電材、充填材等を加えてスラリーとし、これを集電体に塗布、乾燥した後にプレスすることによって形成することができる。
負極活物質を電極化した際の電極構造は特に制限されないが、集電体上に存在している負極活物質の密度は、1g・cm-3以上が好ましく、1.2g・cm-3以上がさらに好ましく、1.3g・cm-3以上が特に好ましく、また、2.2g・cm-3以下が好ましく、2.1g・cm-3以下がより好ましく、2.0g・cm-3以下がさらに好ましく、1.9g・cm-3以下が特に好ましい。集電体上に存在している負極活物質の密度が、上記範囲を上回ると、負極活物質粒子が破壊され、非水系電解液電池の初期不可逆容量の増加や、集電体/負極活物質界面付近への非水系電解液の浸透性低下による高電流密度充放電特性悪化を招く場合がある。また、上記範囲を下回ると、負極活物質間の導電性が低下し、電池抵抗が増大し、単位容積当たりの容量が低下する場合がある。
以下に本発明の非水系電解液電池に使用される正極について説明する。
<2-4-1.正極活物質>
以下に正極に使用される正極活物質について説明する。
正極活物質としては、コバルト酸リチウムや、少なくともNiとCoを含有し、遷移金属のうち50モル%以上がNiとCoである遷移金属酸化物であり、電気化学的に金属イオンを吸蔵・放出可能なものであれば特に制限はないが、例えば、電気化学的にリチウムイオンを吸蔵・放出可能なものが好ましく、リチウムと少なくともNiとCoを含有し、遷移金属のうち50モル%以上がNiとCoである遷移金属酸化物が好ましい。Ni及びCoは、酸化還元の電位が二次電池の正極材として用いるのに好適であり、高容量用途に適しているためである。
Lia1Nib1Coc1Md1O2・・・(1)
(式(1)中、0.90≦a1≦1.10、0.50≦b1≦0.98、0.01≦c1<0.50、0.01≦d1<0.50の数値を示し、b1+c1+d1=1を満たす。MはMn、Al、Mg、Zr、Fe、Ti及びErからなる群より選ばれる少なくとも1種の元素を表す。)
組成式(1)中、0.1≦d1<0.5の数値を示すことが好ましい。
NiやCoの組成比およびその他の金属種の組成比が所定の通りであることで、正極から遷移金属が溶出しにくく、かつ、たとえ溶出したとしてもNiやCoは非水系二次電池内での悪影響が小さいためである。
Lia2Nib2Coc2Md2O2・・・(2)
(式(2)中、0.90≦a2≦1.10、0.50≦b2≦0.96、0.03≦c2<0.50、0.01≦d2<0.40の数値を示し、b2+c2+d2=1を満たす。MはMn、Al、Mg、Zr、Fe、Ti及びErからなる群より選ばれる少なくとも1種の元素を表す。)
組成式(2)中、0.10≦d2<0.40の数値を示すことが好ましい。
NiおよびCoが主成分であり、かつNiの組成比がCoの組成比より大きいことで、非水系電解液電池の正極として用いた際に、安定であり、かつ高容量を取り出すことが可能となるからである。
Lia3Nib3Coc3Md3O2・・・(3)
(式(3)中、0.90≦a3≦1.10、0.60≦b3≦0.94、0.05≦c3≦0.2、0.01≦d3≦0.3の数値を示し、b3+c3+d3=1を満たす。MはMn、Al、Mg、Zr、Fe、Ti及びErからなる群より選ばれる少なくとも1種の元素を表す。)
組成式(3)中、0.10≦d3≦0.3の数値を示すことが好ましい。
上記の組成であることで、非水系二次電池正極として用いた際に、特に高容量を取り出すことが可能となるからである。
中でも、スピネル型構造を有するリチウムマンガン複合酸化物やオリビン型構造を有するリチウム含有遷移金属燐酸化合物が好ましい。具体的にはスピネル型構造を有するリチウムマンガン複合酸化物として、LiMn2O4、LiMn1.8Al0.2O4、LiMn1.5Ni0.5O4等が挙げられる。中でも最も構造が安定であり、非水系電解液電池の異常時にも酸素放出しにくく、安全性に優れるためである。
また、リチウム含有遷移金属燐酸化合物の遷移金属としては、V、Ti、Cr、Mn、Fe、Co、Ni、Cu等が好ましく、具体例としては、例えば、LiFePO4、Li3Fe2(PO4)3、LiFeP2O7等の燐酸鉄類、LiCoPO4等の燐酸コバルト類、LiMnPO4等の燐酸マンガン類、これらのリチウム遷移金属燐酸化合物の主体となる遷移金属原子の一部をAl、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Si、Nb、Mo、Sn、W等の他の金属で置換したもの等が挙げられる。
上記の正極活物質の表面に、主体となる正極活物質を構成する物質とは異なる組成の物質(以後、適宜「表面付着物質」という)が付着したものを用いることもできる。表面付着物質の例としては酸化アルミニウム、酸化ケイ素、酸化チタン、酸化ジルコニウム、酸化マグネシウム、酸化カルシウム、酸化ホウ素、酸化アンチモン、酸化ビスマス等の酸化物、硫酸リチウム、硫酸ナトリウム、硫酸カリウム、硫酸マグネシウム、硫酸カルシウム、硫酸アルミニウム等の硫酸塩、炭酸リチウム、炭酸カルシウム、炭酸マグネシウム等の炭酸塩、炭素等が挙げられる。
表面付着物質により、正極活物質表面での非水系電解液の酸化反応を抑制することができ、電池寿命を向上させることができる。また、付着量が上記範囲内にあると、その効果を十分に発現することができ、リチウムイオンの出入りを阻害することなく抵抗も増加し難くなる。
正極活物質粒子の形状は、従来用いられるような、塊状、多面体状、球状、楕円球状、板状、針状、柱状等が用いられる。また、一次粒子が凝集して、二次粒子を形成して成り、その二次粒子の形状が球状又は楕円球状であってもよい。
正極活物質の製造法としては、本発明の要旨を超えない範囲で特には制限されないが、いくつかの方法が挙げられ、無機化合物の製造法として一般的な方法が用いられる。
特に球状ないし楕円球状の活物質を作製するには種々の方法が考えられるが、例えばその1例として、遷移金属硝酸塩、硫酸塩等の遷移金属原料物質と、必要に応じ他の元素の原料物質を水等の溶媒中に溶解ないし粉砕分散して、攪拌をしながらpHを調節して球状の前駆体を作製回収し、これを必要に応じて乾燥した後、LiOH、Li2CO3、LiNO3等のLi源を加えて高温で焼成して活物質を得る方法が挙げられる。
以下に、本発明に使用される正極の構成及びその作製法について説明する。
(正極の作製法)
正極は、正極活物質粒子と結着剤とを含有する正極活物質層を、集電体上に形成して作製される。正極活物質を用いる正極の製造は、公知のいずれの方法でも作製することができる。例えば、正極活物質と結着剤、並びに必要に応じて導電材及び増粘剤等を乾式で混合してシート状にしたものを正極集電体に圧着するか、又はこれらの材料を液体媒体に溶解又は分散させてスラリーとして、これを正極集電体に塗布し、乾燥することにより、正極活物質層を集電体上に形成させることにより正極を得ることができる。
導電材としては、公知の導電材を任意に用いることができる。具体例としては、銅、ニッケル等の金属材料;天然黒鉛、人造黒鉛等の黒鉛(グラファイト);アセチレンブラック等のカーボンブラック;ニードルコークス等の無定形炭素等の炭素質材料等が挙げられる。なお、これらは、1種を単独で用いてもよく、2種以上を任意の組み合わせ及び比率で併用してもよい。
正極活物質層の製造に用いる結着剤は、非水系電解液や電極製造時用いる溶媒に対して安定な材料であれば、特に限定されない。
塗布法の場合は、電極製造時に用いる液体媒体に対して溶解又は分散される材料であれば特に限定されないが、具体例としては、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、ポリメチルメタクリレート、芳香族ポリアミド、セルロース、ニトロセルロース等の樹脂系高分子;SBR(スチレン・ブタジエンゴム)、NBR(アクリロニトリル・ブタジエンゴム)、フッ素ゴム、イソプレンゴム、ブタジエンゴム、エチレン・プロピレンゴム等のゴム状高分子;スチレン・ブタジエン・スチレンブロック共重合体又はその水素添加物、EPDM(エチレン・プロピレン・ジエン三元共重合体)、スチレン・エチレン・ブタジエン・エチレン共重合体、スチレン・イソプレン・スチレンブロック共重合体又はその水素添加物等の熱可塑性エラストマー状高分子;シンジオタクチック-1,2-ポリブタジエン、ポリ酢酸ビニル、エチレン・酢酸ビニル共重合体、プロピレン・α-オレフィン共重合体等の軟質樹脂状高分子;ポリフッ化ビニリデン(PVdF)、ポリテトラフルオロエチレン、フッ素化ポリフッ化ビニリデン、ポリテトラフルオロエチレン・エチレン共重合体等のフッ素系高分子;アルカリ金属イオン(特にリチウムイオン)のイオン伝導性を有する高分子組成物等が挙げられる。なお、これらの物質は、1種を単独で用いてもよく、2種以上を任意の組み合わせ及び比率で併用してもよい。
正極活物質層を形成するためのスラリーの調製に用いる液体媒体としては、正極活物質、導電材、結着剤、並びに必要に応じて使用される増粘剤を溶解又は分散することが可能な溶媒であれば、その種類に特に制限はなく、水系溶媒と有機系溶媒のどちらを用いてもよい。
水系媒体の例としては、例えば、水、アルコールと水との混合媒等が挙げられる。有機系媒体の例としては、ヘキサン等の脂肪族炭化水素類;ベンゼン、トルエン、キシレン、メチルナフタレン等の芳香族炭化水素類;キノリン、ピリジン等の複素環化合物;アセトン、メチルエチルケトン、シクロヘキサノン等のケトン類;酢酸メチル、アクリル酸メチル等のエステル類;ジエチレントリアミン、N,N-ジメチルアミノプロピルアミン等のアミン類;ジエチルエーテル、テトラヒドロフラン(THF)等のエーテル類;N-メチルピロリドン(NMP)、ジメチルホルムアミド、ジメチルアセトアミド等のアミド類;ヘキサメチルホスファルアミド、ジメチルスルフォキシド等の非プロトン性極性溶媒等を挙げることができる。なお、これらは、1種を単独で用いてもよく、また2種以上を任意の組み合わせ及び比率で併用してもよい。
スラリーを形成するための液体媒体として水系媒体を用いる場合、増粘剤と、スチレンブタジエンゴム(SBR)等のラテックスを用いてスラリー化するのが好ましい。増粘剤は、通常、スラリーの粘度を調製するために使用される。
増粘剤としては、本発明の効果を著しく制限しない限り制限はないが、具体的には、カルボキシメチルセルロース、メチルセルロース、ヒドロキシメチルセルロース、エチルセルロース、ポリビニルアルコール、酸化スターチ、燐酸化スターチ、カゼイン及びこれらの塩等が挙げられる。これらは、1種を単独で用いても、2種以上を任意の組み合わせ及び比率で併用してもよい。
集電体への上記スラリーの塗布、乾燥によって得られた正極活物質層は、正極活物質の充填密度を上げるために、ハンドプレス、ローラープレス等により圧密化することが好ましい。正極活物質層の密度は、1g・cm-3以上が好ましく、1.5g・cm-3以上が更に好ましく、2g・cm-3以上が特に好ましく、また、4g・cm-3以下が好ましく、3.5g・cm-3以下が更に好ましく、3g・cm-3以下が特に好ましい。
正極活物質層の密度が、上記範囲内であると、集電体/活物質界面付近への非水系電解液の浸透性が低下することなく、特に高電流密度での充放電特性が良好となる。さらに、活物質間の導電性が低下し難くなり、電池抵抗が増大し難くなる。
正極集電体の材質としては特に制限は無く、公知のものを任意に用いることができる。具体例としては、アルミニウム、ステンレス鋼、ニッケルメッキ、チタン、タンタル等の金属材料;カーボンクロス、カーボンペーパー等の炭素質材料が挙げられる。中でも金属材料、特にアルミニウムが好ましい。
集電体の厚さは任意であるが、好ましくは1μm以上であり、3μm以上がより好ましく、5μm以上が更に好ましく、また、好ましくは1mm以下であり、100μm以下がより好ましく、50μm以下が更に好ましい。集電体の厚さが、上記範囲内であると、集電体として必要な強度を十分確保することができる。さらに、取り扱い性も良好となる。
集電体と正極活物質層の厚さの比が、上記範囲内であると、高電流密度充放電時に集電体がジュール熱による発熱を生じ難くなる。さらに、正極活物質に対する集電体の体積比が増加し難くなり、電池容量の低下を防ぐことができる。
高出力かつ高温時の安定性を高める観点から、正極活物質層の面積は、電池外装ケースの外表面積に対して大きくすることが好ましい。具体的には、非水系電解液電池の外装の表面積に対する前記正極の電極面積の総和を、面積比で20倍以上とすることが好ましく、更に40倍以上とすることがより好ましい。外装ケースの外表面積とは、有底角型形状の場合には、端子の突起部分を除いた発電要素が充填されたケース部分の縦と横と厚さの寸法から計算で求める総面積をいう。有底円筒形状の場合には、端子の突起部分を除いた発電要素が充填されたケース部分を円筒として近似する幾何表面積である。正極の電極面積の総和とは、負極活物質を含む合材層に対向する正極合材層の幾何表面積であり、集電体箔を介して両面に正極合材層を形成してなる構造では、それぞれの面を別々に算出する面積の総和をいう。
本発明の非水系電解液を用いる場合、非水系電解液電池の1個の電池外装に収納される電池要素のもつ電気容量(電池を満充電状態から放電状態まで放電したときの電気容量)が、1アンペアーアワー(Ah)以上であると、低温放電特性の向上効果が大きくなるため好ましい。そのため、正極板は、放電容量が満充電で、好ましくは3Ah(アンペアアワー)以上であり、より好ましくは4Ah以上、また、好ましくは100Ah以下であり、より好ましくは70Ah以下であり、特に好ましくは50Ah以下になるように設計する。
正極板の厚さは、特に限定されないが、高容量かつ高出力、高レート特性の観点から、集電体の厚さを差し引いた正極活物質層の厚さは、集電体の片面に対して、10μm以上が好ましく、20μm以上がより好ましく、また、200μm以下が好ましく、100μm以下がより好ましい。
正極と負極との間には、短絡を防止するために、通常はセパレータを介在させる。この場合、本発明の非水系電解液は、通常はこのセパレータに含浸させて用いる。
[電極群]
電極群は、前述の正極板と負極板とを前述のセパレータを介してなる積層構造のもの、及び前述の正極板と負極板とを前述のセパレータを介して渦巻き状に捲回した構造のものの何れでもよい。電極群の体積が電池内容積に占める割合(以下、電極群占有率と称する。)は、通常40%以上であり、50%以上が好ましく、また、通常90%以下であり、80%以下が好ましい。電極群占有率の下限は、電池容量の観点から、上記範囲とすることが好ましい。また、電極群占有率の上限は、電池としての充放電繰り返し性能や高温保存等の諸特性の観点、内部圧力を外に逃がすガス放出弁の作動回避の観点から、間隙スペースを確保するために上記範囲とすることが好ましい。間隙スペースが少な過ぎると、電池が高温になることによって部材が膨張したり電解質の液成分の蒸気圧が高くなったりして内部圧力が上昇し、電池としての充放電繰り返し性能や高温保存等の諸特性を低下させたり、さらには、内部圧力を外に逃がすガス放出弁が作動する場合がある。
集電構造は特に限定されるものではないが、本発明の非水系電解液による放電特性の向上をより効果的に実現するには、配線部分や接合部分の抵抗を低減する構造にすることが好ましい。この様に内部抵抗を低減させた場合、本発明の非水系電解液を使用した効果は特に良好に発揮される。
保護素子として、異常発熱や過大電流が流れた時に抵抗が増大するPTC(Positive Temperature Coefficient)、温度ヒューズ、サーミスター、異常発熱時に電池内部圧力や内部温度の急激な上昇により回路に流れる電流を遮断する弁(電流遮断弁)等が挙げられる。前記保護素子は高電流の通常使用で作動しない条件のものを選択することが好ましく、高出力の観点から、保護素子がなくても異常発熱や熱暴走に至らない設計にすることがより好ましい。
本発明の非水系電解液電池は、通常、上記の非水系電解液、負極、正極、セパレータ等を外装体(外装ケース)内に収納して構成される。この外装体に制限は無く、本発明の効果を著しく損なわない限り公知のものを任意に採用することができる。
[正極の作製]
正極活物質としてリチウム・ニッケル・コバルト・マンガン複合酸化物(Li1.0Ni0.5Co0.2Mn0.3O2)90質量部と、導電材としてアセチレンブラック7質量部と、結着剤としてポリフッ化ビニリデン(PVdF)3質量部とを、N-メチルピロリドン溶媒中で、ディスパーザーで混合してスラリー化した。これを厚さ15μmのアルミニウム箔の両面に均一に塗布、乾燥した後、プレスして正極とした。
天然黒鉛98質量部に、増粘剤及び結着剤として、カルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)1質量部及びスチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)1質量部を加え、ディスパーザーで混合してスラリー化した。得られたスラリーを厚さ10μmの銅箔の片面に塗布して乾燥した後、プレスして負極とした。
乾燥アルゴン雰囲気下、エチレンカーボネート(EC)、ジエチルカーボネート(DEC)、エチルメチルカーボネート(EMC)の混合物(体積比EC:DEC:EMC=3:6:1)に、電解質として十分に乾燥させたLiPF6を1.15mol/L(非水系電解液中の濃度として)溶解させ、さらに、フルオロエチレンカーボネート(FEC)を1.15質量%(非水系電解液中の濃度として)添加した(以下、これを基準電解液1と呼ぶ)。基準電解液1に対して、下記表1に記載の含有量で化合物1~6を添加剤として加えて非水系電解液を調製した。なお、表中の「含有量(質量%)」は、各非水系電解液全体を100質量%とした時の含有量である。
上記の正極、負極及びポリエチレン製のセパレータを、負極、セパレータ、正極の順に積層して電池要素を作製した。この電池要素をアルミニウム(厚さ40μm)の両面を樹脂層で被覆したラミネートフィルムからなる袋内に正極と負極の端子を突設させながら挿入した後、上記調製後の非水系電解液を袋内に注入し、真空封止を行い、ラミネート型の非水系電解液電池を作製した。
[初期コンディショニング]
25℃の恒温槽中、上記の方法で作製した非水系電解液電池を、0.1C(1Cとは、充電または放電に1時間かかる電流値のことを示す。以下同様。)に相当する電流で3.2Vまで定電流充電した後、0.2Cで4.2Vまで定電流-定電圧充電(以下、CC-CV充電と記載)を行った。その後、45℃に120時間保持しエージングを実施した。その後、0.2Cで2.5Vまで放電し、非水系電解液電池を安定させた。さらに、0.2Cで4.2VまでCC-CV充電を行った後、0.2Cで2.5Vまで放電し、初期コンディショニングを行った。
初期コンディショニング後の電池を0.2Cで初期放電容量の半分の容量となるようCC-CV充電を行った。これを25℃において各々1.0C、2.0C、3.0Cで放電させ、その5秒時の電圧を測定した。得られた1.0C、2.0C、3.0Cにおける電流-電圧直線の傾きの平均値を電池内部抵抗とした。
[充電保存試験]
初期コンディショニング後のラミネート型の非水系電解液電池を再度、0.2Cで4.2VまでCC-CV充電を行った後、60℃、168時間の条件で高温保存を行った。電池を十分に冷却させた後、エタノール浴中に浸して体積を測定し、保存試験前後の体積変化から発生ガス量を求め、これを「充電保存ガス量」とした。
また、保存試験後の非水系電解液電池を0.2Cで2.5Vまで放電し、0.2Cで初期放電容量の半分の容量となるようCC-CV充電を行い、保存試験後の電池内部抵抗を求めた。下記式(4)から「内部抵抗増加率」を算出した。
内部抵抗増加率=[(保存試験後内部抵抗)/(初期コンディショニング後内部抵抗)]×100%(4)
下記表1に、比較例1‐1の充電保存ガス量、内部抵抗増加率を、それぞれ100とした際の充電保存ガス量の比、及び内部抵抗増加率の比を示した。
一方、化合物1~3を全て含むが、化合物1の含有量が1.5質量%を超える比較例1-2、1-3では、比較例1-1及び1-8に対し、充電保存ガス量は低減できているものの、実施例1-1~1-4ほどの改善幅は得られておらず、内部抵抗はかえって増加してしまう結果となった。
また、化合物1~3を全て含むが、化合物3又は化合物4の含有量が0.49質量%を超える比較例1-4、1-5及び1-9では、充電保存ガス量は実施例1-1~1-4及び1-7と同等の改善幅が得られているものの、比較例1-1及び1-8に対し、内部抵抗は同等もしくはかえって増加してしまう結果となった。
また、化合物3を0.49質量%以下で含有するものの、化合物1もしくは化合物2のいずれか一方しか含有していない比較例1-6、1-7においても、充電保存ガス量は実施例1-1~1-4と同等の改善幅が得られているものの、比較例1-1及び1-8に対し、内部抵抗はかえって増加してしまう結果となった。
[正極の作製]
正極活物質としてリチウム・ニッケル・コバルト・マンガン複合酸化物(Li1.0Ni0.6Co0.2Mn0.2O2)94質量部と、導電材としてアセチレンブラック3質量部と、結着剤としてポリフッ化ビニリデン(PVdF)3質量部とを、N-メチルピロリドン溶媒中で、ディスパーザーで混合してスラリー化した。これを厚さ15μmのアルミニウム箔の両面に均一に塗布、乾燥した後、プレスして正極とした。
実施例1-1と同じ方法で負極を作製し、使用した。
基準電解液1に対して、下記表2に記載の含有量で化合物1~4を添加剤として加えて非水系電解液を調製した。なお、表中の「含有量(質量%)」は、各非水系電解液全体を100質量%とした時の含有量である。
上記の正極、負極及びポリエチレン製のセパレータを、負極、セパレータ、正極の順に積層して電池要素を作製した。この電池要素をアルミニウム(厚さ40μm)の両面を樹脂層で被覆したラミネートフィルムからなる袋内に正極と負極の端子を突設させながら挿入した後、上記調製後の非水系電解液を袋内に注入し、真空封止を行い、ラミネート型の非水系電解液電池を作製した。
作製した非水系電解液電池に対し、実施例1-1と同様の方法で充電保存ガス量、内部抵抗増加率を測定し、下記表2に、比較例2-1の充電保存ガス量、内部抵抗増加率を、それぞれ100とした際の充電保存ガス量の比、及び内部抵抗増加率の比を示した。
[正極の作製]
正極活物質としてリチウム・ニッケル・マンガン・コバルト複合酸化物(Li1.0Ni0.33Co0.33Mn0.33O2)85質量%と、導電材としてアセチレンブラック10質量%と、結着剤としてポリフッ化ビニリデン(PVDF)5質量%とを、N-メチルピロリドン溶媒中で、ディスパーザーで混合してスラリー化した。これを厚さ21μmのアルミニウム箔の両面に均一に塗布、乾燥した後、プレスして正極とした。
平均粒子径0.2μmのSi微粒子50gを平均粒子径35μmの鱗片状黒鉛2000g中に分散させ、ハイブリダイゼーションシステム(奈良機械製作所製)に投入し、ローター回転数7000rpm、180秒間、装置内を循環又は滞留させて処理し、Siと黒鉛粒子との複合体を得た。得られた複合体を、焼成後の被覆率が、7.5%になるように炭素質物となる有機化合物としてコールタールピッチを混合し、2軸混練機により混練・分散させた。得られた分散物を、焼成炉に導入し、窒素雰囲気下で1000℃、3時間、焼成した。得られた焼成物は、更にハンマーミルで粉砕後、篩(45μm)を実施し、負極活物質を作製した。この負極活物質を、前記測定法で測定したSi元素の含有量、平均粒子径d50、タップ密度、比表面積はそれぞれ、2.0質量%、20μm、1.0g/cm3、7.2m2/gであった。
上記負極活物質に対して、増粘剤、バインダーとしてそれぞれ、カルボキシメチルセルロースナトリウムの水性ディスパージョン(カルボキシメチルセルロースナトリウムの濃度1質量%)、及び、スチレン-ブタジエンゴムの水性ディスパージョン(スチレン-ブタジエンゴムの濃度50質量%)を加え、ディスパーザーで混合してスラリー化した。このスラリーを厚さ10μmの銅箔の片面に均一に塗布、乾燥した後、プレスして負極とした。なお、乾燥後の負極において、負極活物質:カルボキシメチルセルロースナトリウム:スチレン-ブタジエンゴム=97.5:1.5:1の質量比となるように作製した。
基準電解液1に対して、下記表3に記載の含有量で化合物1~4を添加剤として加えて非水系電解液を調製した。なお、表中の「含有量(質量%)」は、各非水系電解液全体を100質量%とした時の含有量である。
上記の正極、負極及びポリエチレン製のセパレータを、負極、セパレータ、正極の順に積層して電池要素を作製した。この電池要素をアルミニウム(厚さ40μm)の両面を樹脂層で被覆したラミネートフィルムからなる袋内に正極と負極の端子を突設させながら挿入した後、上記調製後の非水系電解液を袋内に注入し、真空封止を行い、ラミネート型の非水系電解液電池を作製した。
作製した非水系電解液電池に対し、実施例1-1と同様の方法で充電保存ガス量、内部抵抗増加率を測定し、下記表3に、比較例3-1の充電保存ガス量、内部抵抗増加率を、それぞれ100とした際の充電保存ガス量の比、及び内部抵抗増加率の比を示した。
また、本発明の非水系電解液及びこれを用いた非水系電解液電池は、非水系電解液電池を用いる公知の各種用途に用いることが可能である。具体例としては、例えば、ノートパソコン、ペン入力パソコン、モバイルパソコン、電子ブックプレーヤー、携帯電話、携帯ファックス、携帯コピー、携帯プリンター、ヘッドフォンステレオ、ビデオムービー、液晶テレビ、ハンディークリーナー、ポータブルCD、ミニディスク、トランシーバー、電子手帳、電卓、メモリーカード、携帯テープレコーダー、ラジオ、バックアップ電源、モーター、バイク、原動機付自転車、自転車、照明器具、玩具、ゲーム機器、時計、電動工具、ストロボ、カメラ、家庭用バックアップ電源、事業所用バックアップ電源、負荷平準化用電源、自然エネルギー貯蔵電源、リチウムイオンキャパシタ等が挙げられる。
Claims (13)
- 下記一般式(A)で表される化合物、炭素‐炭素不飽和結合を有する環状カーボネート、並びに下記一般式(B)及び下記一般式(C)で表される化合物からなる群より選ばれる少なくとも一種の化合物を含有する非水系電解液であって、
該炭素‐炭素不飽和結合を有する環状カーボネートの該非水系電解液全体に対する含有量が0.01質量%以上1.5質量%以下であり、
該一般式(B)及び該一般式(C)で表される化合物のいずれか一方のみを含有する場合は、該一般式(B)又は該一般式(C)で表される化合物の該非水系電解液全体に対する含有量が0.01質量%以上0.49質量%以下であり、
該一般式(B)及び該一般式(C)で表される化合物の両方を含有する場合は、該一般式(B)及び該一般式(C)で表される化合物全体の該非水系電解液全体に対する含有量が0.01質量%以上0.80質量%以下である、非水系電解液。
(式(A)中、m、nは、それぞれ独立に、1~3の整数を示す。)
(式(B)中、R1~R3は、互いに同一であっても異なっていてもよく、置換基を有していてもよい炭素数1~10の炭化水素基である。但し、R1~R3のうち少なくとも1つは炭素-炭素不飽和結合を有する炭化水素基である。)
(式(C)中、Qは、炭素数3~20の炭化水素基であり、該炭化水素基はシクロアルキレン基を有する。) - 前記一般式(B)中、炭素-炭素不飽和結合を有する炭化水素基がアリル基又はメタリル基である、請求項1に記載の非水系電解液。
- 前記非水系電解液が、さらにフッ素原子を有する環状カーボネートを含有する、請求項1又は2に記載の非水系電解液。
- 前記フッ素原子を有する環状カーボネートの含有量が、非水系電解液の全量に対して0.01質量%以上5質量%以下である、請求項3に記載の非水系電解液。
- 前記非水系電解液が、さらにフッ素化された塩及びオキサラート塩からなる群より選ばれる少なくとも1種の塩を含有する、請求項1乃至4のいずれか1項に記載の非水系電解液。
- 前記フッ素化された塩及び/又は前記オキサラート塩の含有量が、非水系電解液の全量に対して0.01質量%以上5質量%以下である、請求項5に記載の非水系電解液。
- 金属イオンを吸蔵及び放出可能な正極及び負極と、非水系電解液とを備えた非水系電解液電池であって、該非水系電解液が請求項1乃至6のいずれか1項に記載の非水系電解液である、非水系電解液電池。
- 前記正極に含まれる正極活物質が、下記組成式(1)で表される金属酸化物である、請求項7に記載の非水系電解液電池。
Lia1Nib1Coc1Md1O2・・・(1)
(上記式(1)中、a1、b1、c1及びd1は、0.90≦a1≦1.10、0.50≦b1≦0.98、0.01≦c1<0.50、0.01≦d1<0.50の数値を示し、b1+c1+d1=1を満たす。MはMn、Al、Mg、Zr、Fe、Ti及びErからなる群より選ばれる少なくとも1種の元素を表す。) - 前記負極が、Liと合金化可能な金属粒子と、黒鉛とを含有する負極活物質を含む、請求項7又は8に記載の非水系電解液電池。
- 前記Liと合金化可能な金属粒子が、Si、Sn、As、Sb、Al、Zn及びWからなる群より選ばれる少なくとも1種の金属を含む金属粒子である、請求項9に記載の非水系電解液電池。
- 前記Liと合金化可能な金属粒子が、Si又はSi金属酸化物である、請求項9に記載の非水系電解液電池。
- 前記Liと合金化可能な金属粒子と、黒鉛とを含有する負極活物質が、金属粒子と黒鉛粒子との複合体及び/又は混合物である、請求項9~11のいずれか1項に記載の非水系電解液電池。
- 前記Liと合金化可能な金属粒子と、黒鉛とを含有する負極活物質の合計に対する、前記Liと合金化可能な金属粒子の含有量が、0.1質量%以上25質量%以下である、請求項9~12のいずれか1項に記載の非水系電解液電池。
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| EP3780226A4 (en) | 2021-06-02 |
| JPWO2019189670A1 (ja) | 2021-04-01 |
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