WO2017047554A1 - Nonaqueous electrolyte solution for electricity storage devices and electricity storage device using same - Google Patents

Abstract

The present invention is: a nonaqueous electrolyte solution for electricity storage devices, which allows improvement in electrochemical characteristics in a wide temperature range, the nonaqueous electrolyte solution including an electrolyte salt dissolved in a nonaqueous solvent and being characterized by containing, in the nonaqueous electrolyte solution, 0.01-10 mass% of a compound expressed by general formula (I); and an electricity storage device using the nonaqueous electrolyte solution. (In the formula, X represents an S(=O)₂ group or an S=O group, and R¹-R⁸ each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1-4 carbon atoms in which some of hydrogen atoms may be substituted by halogen atoms.)

Description

Nonaqueous electrolyte for power storage device and power storage device using the same

The present invention relates to a nonaqueous electrolytic solution for an electricity storage device capable of improving electrochemical characteristics over a wide temperature range and an electricity storage device using the same.

In recent years, power storage devices, particularly lithium secondary batteries, have been widely used as power sources for small electronic devices such as mobile phones and laptop computers, electric vehicles, and power storage sources. Since these electronic devices and automobiles may be used in a wide temperature range such as a high temperature in midsummer or a low temperature in extremely cold, it is required to improve electrochemical characteristics in a wide range of temperatures. .
In particular, in order to prevent global warming, there is an urgent need to reduce CO ₂ emissions. Among environmentally friendly vehicles equipped with power storage devices consisting of power storage devices such as lithium secondary batteries and lithium ion capacitors, hybrid electricity Early spread of automobiles (HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV) is required. Due to the long travel distance of automobiles, automobiles may be used in areas with a wide temperature range from extremely hot areas in the tropics to extremely cold areas. Therefore, in particular, these in-vehicle power storage devices are required not to deteriorate in electrochemical characteristics even when used in a wide temperature range from high temperature to low temperature.
Note that in this specification, the term lithium secondary battery is used as a concept including a so-called lithium ion secondary battery.

A lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of occluding and releasing lithium ions, a lithium salt, and a non-aqueous electrolyte composed of a non-aqueous solvent. As the non-aqueous solvent, ethylene carbonate (EC ), Carbonates such as propylene carbonate (PC) are used.
As negative electrodes of lithium secondary batteries, metal lithium, metal compounds capable of inserting and extracting lithium ions (metal simple substance, metal oxide, alloy with lithium, etc.) and carbon materials are known. In particular, lithium secondary batteries using carbon materials such as coke, artificial graphite, and natural graphite capable of inserting and extracting lithium ions have been widely put into practical use.

For example, a lithium secondary battery using a highly crystallized carbon material such as natural graphite or artificial graphite as a negative electrode material is a decomposition product generated by reductive decomposition of a solvent in a non-aqueous electrolyte on the negative electrode surface during charging. It has been found that the gas interferes with the desired electrochemical reaction of the battery, resulting in poor cycle characteristics. Further, when a decomposition product of a nonaqueous solvent accumulates on the electrode surface, lithium cannot be smoothly occluded and released from the negative electrode, and the electrochemical characteristics when used in a wide temperature range are liable to deteriorate.
In addition, lithium secondary batteries using lithium metal, alloys thereof, simple metals such as tin or silicon, and metal oxides as negative electrode materials have high initial capacities, but fine powders progress during the cycle. It is known that reductive decomposition of a nonaqueous solvent occurs at an accelerated rate as compared with a negative electrode, and battery performance such as battery capacity and cycle characteristics is greatly reduced. In addition, due to the pulverization of these negative electrode materials and the accumulation of decomposition products of nonaqueous solvents, the insertion and extraction of lithium into the negative electrode cannot be performed smoothly, and the electrochemical characteristics when used over a wide temperature range are likely to deteriorate. .

On the other hand, as a positive electrode material, for example, a lithium secondary battery using LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO _4, etc., the non-aqueous solvent in the non-aqueous electrolyte is charged and the positive electrode material and the non-aqueous electrolyte are used. The degradation products and gas generated by partial oxidative decomposition locally at the interface with the hinders the desired electrochemical reaction of the battery, which also causes degradation of electrochemical characteristics when used in a wide temperature range I know that.

As described above, the battery performance has been deteriorated due to the movement of lithium ions or the expansion of the battery due to the decomposition product or gas when the non-aqueous electrolyte is decomposed on the positive electrode or the negative electrode. In spite of such a situation, electronic devices equipped with lithium secondary batteries are becoming more and more multifunctional and power consumption is increasing. As a result, the capacity of lithium secondary batteries has been increasing, and the density of the electrodes has been increased and the useless space in the battery has been reduced. The volume occupied by the nonaqueous electrolyte in the battery has been reduced. It has become. Therefore, there is a situation in which the electrochemical characteristics when used in a wide temperature range are likely to deteriorate with a slight decomposition of the non-aqueous electrolyte.
Patent Document 1 describes that a nonaqueous electrolytic solution containing a cyclic sulfate such as ethylene glycol sulfate can suppress capacity deterioration associated with a charge / discharge cycle.
In Patent Document 2, hexahydro 1,3,2-benzodioxathiol 2,2-dioxide (6-membered cyclic sulfate), 1,2-cyclohexanediol cyclic sulfite (6-membered cyclic sulfite) and the like 1 , 2-cyclohexanediol derivatives (6-membered ring compounds) are described as being excellent in long-term cycle characteristics and capable of suppressing gas generation.
Patent Document 3 discloses that a non-aqueous electrolyte containing a cyclic (5-membered ring) carbonate ester compound such as 1,2-cyclopentanediol cyclic carbonate is a normal temperature cycle characteristic, storage characteristic and low temperature of a secondary battery. It is described to improve cycle characteristics.

JP-A-10-189042 International Publication No. 2007/020876 JP 2011-124008 A

An object of the present invention is to provide a nonaqueous electrolytic solution for an electricity storage device that can improve electrochemical characteristics in a wide temperature range and an electricity storage device using the same.

As a result of detailed studies on the performance of the above-described conventional non-aqueous electrolytes, the present inventors have found that the secondary batteries using the non-aqueous electrolytes of Patent Documents 1 and 3 have low-temperature discharge characteristics after high-temperature storage and the like. The actual situation is that a sufficient effect is not obtained for the problem of improving the electrochemical characteristics in a wide temperature range. Moreover, there was room for improvement in the nonaqueous electrolytic solution of Patent Document 2.
Accordingly, the present inventors have made extensive studies to solve the above problems, and in a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, a cyclopentane structure represented by the following general formula (I): It has been found that the inclusion of one or more compounds selected from sulfuric acid esters and sulfites containing hydrogen can improve the electrochemical characteristics of the electricity storage device, particularly the electrochemical characteristics of the lithium battery, over a wide temperature range. Such an effect is not suggested at all in Patent Documents 1 to 3.

That is, the present invention provides the following (1) and (2).
(1) A nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, and the compound represented by the following general formula (I) is contained in the nonaqueous electrolytic solution in an amount of 0.01 to 10% by mass. A nonaqueous electrolytic solution for an electricity storage device.

（式中、ＸはＳ（＝Ｏ）_２基又はＳ＝Ｏ基を示し、Ｒ^１～Ｒ^８は、それぞれ独立して水素原子、ハロゲン原子、又は水素原子の一部がハロゲン原子で置換されていてもよい炭素数１～４のアルキル基を示す。）

(In the formula, X represents an S (═O) ₂ group or an S═O group, and R ¹ to R ⁸ each independently represents a hydrogen atom, a halogen atom, or a part of the hydrogen atom is substituted with a halogen atom. And an optionally substituted alkyl group having 1 to 4 carbon atoms.)

(2) A power storage device including a positive electrode, a negative electrode, and a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte is the non-aqueous electrolyte described in (1). An electricity storage device characterized by the above.

According to the present invention, there are provided a nonaqueous electrolytic solution for an electricity storage device capable of improving the electrochemical characteristics of the electricity storage device in a wide temperature range, particularly a low temperature discharge property after high temperature storage, and an electricity storage device such as a lithium battery using the same. be able to.

[Nonaqueous electrolyte for power storage devices]
The non-aqueous electrolyte for an electricity storage device of the present invention (hereinafter also simply referred to as “non-aqueous electrolyte”) is a non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, and the general formula (I) The compound represented by the formula is characterized by containing 0.01 to 10% by mass in the non-aqueous electrolyte.

The reason why the nonaqueous electrolytic solution of the present invention can greatly improve the electrochemical characteristics of the electricity storage device in a wide temperature range is not necessarily clear, but is considered as follows.
The compound used by this invention is a compound chosen from the sulfate ester and sulfite ester containing a cyclopentane structure as described in the said general formula (I). This cyclopentane ring (five-membered ring) has a larger strain energy than the cyclohexane ring (six-membered ring). Therefore, the hexahydro 1,3 described in Patent Document 2 is a sulfate or sulfite containing a cyclopentane structure represented by the general formula (I), which is a sulfate or sulfite containing a cyclohexane (six-membered ring) structure. , 2-benzodioxathiol 2,2-dioxide and 1,2-cyclohexanediol cyclic sulfite are more susceptible to electrochemical decomposition, and a dense and highly heat-resistant film is formed on the positive and negative electrodes. Similarly, it is more susceptible to electrochemical decomposition than the ethylene glycol sulfate described in Patent Document 1, which is a sulfate that does not contain a cycloalkane structure, and a dense and highly heat-resistant film is formed on the positive electrode and the negative electrode. . Therefore, the nonaqueous electrolytic solution of the present invention can improve electrochemical characteristics in a wide temperature range such as low temperature discharge characteristics after high temperature storage, compared with the nonaqueous electrolytic solutions of Patent Documents 1 and 2. Conceivable.
Further, like 1,2-cyclopentanediol cyclic carbonate described in Patent Document 3, even a compound having a cyclopentane structure as in the case of the compound according to the present invention may be functionalized like sulfate ester or sulfite ester. In the case of carbonates having> C = O groups rather than groups (> S (= O) ₂ groups or> S = O groups), the properties of the film formed are greatly different, so that the low temperature after high temperature storage It is impossible to improve electrochemical characteristics in a wide temperature range such as discharge characteristics.

The compound selected from sulfate and sulfite contained in the non-aqueous electrolyte of the present invention is represented by the following general formula (I).

（式中、ＸはＳ（＝Ｏ）_２基又はＳ＝Ｏ基を示し、Ｒ^１～Ｒ^８は、それぞれ独立して水素原子、ハロゲン原子、又は水素原子の一部がハロゲン原子で置換されていてもよい炭素数１～４のアルキル基を示す。）

(In the formula, X represents an S (═O) ₂ group or an S═O group, and R ¹ to R ⁸ each independently represents a hydrogen atom, a halogen atom, or a part of the hydrogen atom is substituted with a halogen atom. And an optionally substituted alkyl group having 1 to 4 carbon atoms.)

In the general formula (I), R ¹ to R ⁸ are each independently a hydrogen atom, a halogen atom such as a fluorine atom, or a part of the hydrogen atom which may be substituted with a halogen atom. 3, preferably an alkyl group having 1 or 2 carbon atoms, more preferably a hydrogen atom or a fluorine atom, and still more preferably a hydrogen atom.
The number of substituents of the alkyl group which may be partially substituted with a halogen atom or a hydrogen atom is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.
The substitution position of the alkyl group in which a halogen atom or a part of the hydrogen atom may be substituted with a halogen atom is the 4-position, as viewed from X (S (═O) ₂ group or S═O group), that is, R ^2. Or it is preferable that it is a position of R < ³ > or R < ⁶ > or R < ⁷ >.

Specific examples of the case where R ¹ to R ⁸ are an alkyl group in which a part of hydrogen atoms may be substituted with a halogen atom include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. A linear alkyl group; branched alkyl groups such as isopropyl group, sec-butyl group, and tert-butyl group; fluoromethyl group, difluoromethyl group, trifluoromethyl group, 2-chloroethyl group, 2-fluoro group Ethyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, 3-fluoropropyl group, 3-chloropropyl group, 3,3-difluoropropyl group, 3,3,3-trifluoro Some hydrogen atoms such as propyl group, 2,2,3,3-tetrafluoropropyl group, and 2,2,3,3,3-pentafluoropropyl group are substituted with halogen atoms. Alkyl group is preferably exemplified. Among these, a methyl group, an ethyl group, an n-propyl group, a trifluoromethyl group, or a 2,2,2-trifluoroethyl group is preferable, a methyl group, an ethyl group, or a trifluoromethyl group is more preferable. Further preferred are groups or ethyl groups.

The sulfate ester or sulfite ester having a cyclopentane structure represented by the general formula (I) is a cis-type compound represented by the following general formula (II) and a trans-type compound represented by the following general formula (III). Include.

（式中、Ｘ及びＲ^１～Ｒ^８は、一般式（I）と同義である。）

(In the formula, X and R ¹ to R ⁸ have the same meaning as in formula (I).)

The compound represented by the general formula (I) may be a mixture of a cis-type compound represented by the general formula (II) and a trans-type compound represented by the general formula (III). The cis-type compound / trans-type compound (mass ratio) is preferably 50/50 to 100/0, more preferably 60/40 to 100/0, still more preferably 70/30 to 100/0, and still more preferably 80 / 20 to 100/0, more preferably 90/10 to 100/0, and particularly preferably a cis-type compound alone.

Specific examples of the sulfate represented by the general formula (I) include the following compounds 1 to 22.

Specific examples of the sulfite ester represented by the general formula (I) include the following compounds 23 to 44.

Among the above preferred examples, tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2-dioxide (Compound 1), 4-fluorotetrahydro-4H-cyclopenta [d] [ 1,3,2] dioxathiol-2,2-dioxide (compound 3), 4-methyltetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2-dioxide (compound 8) ), Tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2-oxide (compound 23), 4-fluorotetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol -2-oxide (compound 25), and 4-methyltetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2-oxide (compound 3) ) Is chosen one or more kinds from.
More preferably, tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2-dioxide (Compound 1), 4-fluorotetrahydro-4H-cyclopenta [d] [1,3,2 ] One or more selected from dioxathiol-2,2-dioxide (compound 3) and tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2-oxide (compound 23) Particularly preferred is tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2-dioxide (Compound 1).

In the non-aqueous electrolyte of the present invention, the total content of the compound represented by the general formula (I) (sulfuric ester and sulfite) contained in the non-aqueous electrolytic solution is 0.01 in the non-aqueous electrolytic solution. ~ 10% by mass. When the content is 10% by mass or less, there is little possibility that a coating film is excessively formed on the electrode and the low-temperature characteristics are deteriorated. Since the improvement effect of electrochemical characteristics increases in the range, the above range is preferable. The content is more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more in the non-aqueous electrolyte. Moreover, the upper limit is preferably 5% by mass or less, and more preferably 3% by mass or less.

In the non-aqueous electrolyte solution of the present invention, the compound represented by the general formula (I) can be combined with a non-aqueous solvent, an electrolyte salt, and other additives described below to have electrochemical characteristics over a wide temperature range. It produces a unique effect of synergistic improvement.

[Nonaqueous solvent]
As the non-aqueous solvent used in the non-aqueous electrolyte solution of the present invention, one or more selected from cyclic carbonates, chain esters, lactones, ethers and amides are preferably mentioned. In order to synergistically improve electrochemical properties over a wide temperature range, it is preferable that a chain ester is included, more preferably a chain carbonate is included, and both a cyclic carbonate and a chain ester are further included. It is particularly preferable that both cyclic carbonate and chain carbonate are included.
The term “chain ester” is used as a concept including a chain carbonate and a chain carboxylic acid ester.

Cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one (FEC), trans or Cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter collectively referred to as “DFEC”), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and 4-ethynyl-1 , 3-dioxolan-2-one (EEC), or two or more kinds selected from ethylene carbonate (EC), propylene carbonate (PC), 4-fluoro-1,3-dioxolan-2-one (FEC) ), Vinylene carbonate (VC), and 4-ethynyl-1,3-dioxo One or two or more selected from the emission-2-one (EEC) is more preferable.

In addition, use of at least one of unsaturated bonds such as carbon-carbon double bonds or carbon-carbon triple bonds, or cyclic carbonates having a fluorine atom is preferable because the electrochemical properties in a high temperature environment are further improved. More preferably, both a cyclic carbonate containing an unsaturated bond such as a carbon double bond or a carbon-carbon triple bond and a cyclic carbonate having a fluorine atom are included. As the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or carbon-carbon triple bond, VC, VEC, or EEC is more preferable, and as the cyclic carbonate having a fluorine atom, FEC or DFEC is more preferable.

The content of the cyclic carbonate having an unsaturated bond such as a carbon-carbon double bond or a carbon-carbon triple bond is preferably 0.07% by volume or more, more preferably 0.8%, based on the total volume of the nonaqueous solvent. The upper limit is preferably 7% by volume or less, more preferably 4% by volume or less, and still more preferably 2.5% by volume or less. It is preferable for the content to be in the above-mentioned range since the electrochemical characteristics can be increased in a wider temperature range without impairing Li ion permeability.

The content of the cyclic carbonate having a fluorine atom is preferably 0.07% by volume or more, more preferably 0.7% by volume or more, still more preferably 4% by volume or more, and most preferably based on the total volume of the nonaqueous solvent. The upper limit is preferably 35% by volume or less, more preferably 25% by volume or less, and further 15% by volume or less. It is preferable for the content to be in the above range since the electrochemical characteristics in a wider temperature range can be improved without impairing the Li ion permeability.

When the non-aqueous solvent contains both the cyclic carbonate having an unsaturated bond and the cyclic carbonate having a fluorine atom, the content of the cyclic carbonate having an unsaturated bond with respect to the content of the cyclic carbonate having a fluorine atom is preferably 0.2% by volume or more, more preferably 3% by volume or more, further preferably 7% by volume or more, and the upper limit thereof is preferably 40% by volume or less, more preferably 30% by volume or less, and further 15% by volume or less. is there. The content within the above range is particularly preferable because electrochemical characteristics in a wider temperature range can be improved without impairing Li ion permeability.

In addition, it is preferable that the non-aqueous solvent contains both the cyclic carbonate having the unsaturated bond, since the electrochemical characteristics in a wide temperature range of the film formed on the electrode can be improved. The content of the cyclic carbonate having a bond is preferably 3% by volume or more, more preferably 5% by volume or more, and still more preferably 7% by volume or more with respect to the total volume of the non-aqueous solvent. Preferably it is 45 volume% or less, More preferably, it is 35 volume% or less, More preferably, it is 25 volume% or less.

These solvents may be used singly, and when two or more types are used in combination, it is preferable because the effect of improving electrochemical properties under a high temperature environment is further improved, and three or more types are used in combination. It is particularly preferable to do this.
Preferred combinations of these cyclic carbonates include EC and PC, EC and VC, PC and VC, VC and FEC, EC and FEC, PC and FEC, FEC and DFEC, EC and DFEC, PC and DFEC, VC and DFEC , VEC and DFEC, VC and EEC, EC and EEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and VEC, EC and VC and EEC, EC and EEC and FEC, PC And VC and FEC, EC and VC and DFEC, PC and VC and DFEC, EC and PC and VC and FEC, or EC and PC, VC and DFEC are preferable. Of the above combinations, EC and VC, EC and FEC, PC and FEC, EC and PC and VC, EC and PC and FEC, EC and VC and FEC, EC and VC and EEC, EC and EEC and FEC, PC and A combination of VC and FEC, or EC, PC, VC and FEC is more preferable.

As the chain ester, one or more asymmetric chain carbonates selected from methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, and ethyl propyl carbonate; dimethyl One or more symmetrical linear carbonates selected from carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, and dibutyl carbonate; pivalate esters such as methyl pivalate, ethyl pivalate, and propyl pivalate, propion Preferable examples include one or more chain carboxylic acid esters selected from methyl acid, ethyl propionate (EP), propyl propionate, methyl acetate, and ethyl acetate (EA).
Among the chain esters, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), methyl propyl carbonate (MPC), methyl isopropyl carbonate (MIPC), methyl butyl carbonate, methyl propionate, methyl acetate and ethyl acetate (EA) A chain ester having a methyl group selected from is preferable, and a chain carbonate having a methyl group is particularly preferable.
Moreover, when using chain carbonate, it is preferable to use 2 or more types. Further, it is more preferable that both a symmetric chain carbonate and an asymmetric chain carbonate are contained, and it is further more preferable that more symmetric chain carbonate is contained than the asymmetric chain carbonate.

The content of the chain ester is not particularly limited, but it is preferably used in the range of 60 to 90% by volume with respect to the total volume of the nonaqueous solvent. If the content is 60% by volume or more, the viscosity of the non-aqueous electrolyte does not become too high, and if it is 90% by volume or less, the electrical conductivity of the non-aqueous electrolyte is lowered and the electrochemistry in a wide temperature range is achieved. Since there is little possibility that a characteristic will fall, it is preferable that it is the said range.

The proportion of the volume occupied by the symmetrical linear carbonate in the linear carbonate is preferably 51% by volume or more, and more preferably 55% by volume or more. The upper limit is more preferably 95% by volume or less, and still more preferably 85% by volume or less. It is particularly preferred that dimethyl carbonate (DMC) is contained in the symmetric chain carbonate. The asymmetric chain carbonate preferably has a methyl group, and methyl ethyl carbonate (MEC) is particularly preferable. The above case is preferable because electrochemical characteristics in a wider temperature range are improved.

The ratio between the cyclic carbonate and the chain ester is preferably 10/90 to 45/55, and preferably 15/85 to 40/60, from the viewpoint of improving electrochemical properties at high temperatures. Is more preferable, and 20/80 to 35/65 is particularly preferable.

In the present invention, in addition to the above non-aqueous solvent, other non-aqueous solvents can be added. Other nonaqueous solvents include cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and 1,4-dioxane, chains such as 1,2-dimethoxyethane, 1,2-diethoxyethane and 1,2-dibutoxyethane. Preferable examples include one or two or more selected from amides such as cyclic ethers, amides such as dimethylformamide, sulfones such as sulfolane, and lactones such as γ-butyrolactone (GBL), γ-valerolactone, and α-angelicalactone.
The content of the other nonaqueous solvent is usually 1% or more, preferably 2% or more, and usually 40% or less, preferably 30% or less, more preferably 20%, based on the total volume of the nonaqueous solvent. It is as follows.

The above non-aqueous solvents are usually used as a mixture in order to achieve appropriate physical properties. The combination includes, for example, a combination of a cyclic carbonate and a chain carbonate, a combination of a cyclic carbonate and a chain carboxylic acid ester, a combination of a cyclic carbonate, a chain ester (particularly a chain carbonate) and a lactone, and a cyclic carbonate and a chain. Preferred examples include a combination of a chain ester (particularly a chain carbonate) and an ether, a combination of a cyclic carbonate, a chain carbonate and a chain carboxylic acid ester, etc., and a combination of a cyclic carbonate, a chain ester and a lactone is more preferable. Of these lactones, γ-butyrolactone (GBL) is more preferred.

For the purpose of improving electrochemical characteristics over a wider temperature range, other additives can be added to the non-aqueous electrolyte.
Specific examples of other additives include the following compounds (A) to (I).

(A) One or more nitriles selected from acetonitrile, propionitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, suberonitrile, and sebacononitrile.
(B) cyclohexylbenzene, fluorocyclohexylbenzene compound (1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-amylbenzene, 1 Aromatic compounds having a branched alkyl group such as -fluoro-4-tert-butylbenzene, biphenyl, terphenyl (o-, m-, p-isomer), diphenyl ether, fluorobenzene, difluorobenzene (o-, m -, P-form), anisole, 2,4-difluoroanisole, terphenyl hydrides (1,2-dicyclohexylbenzene, 2-phenylbicyclohexyl, 1,2-diphenylcyclohexane, o-cyclohexylbiphenyl), etc. Aroma Compound.
(C) selected from methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate One or more isocyanate compounds.

(D) 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2- (methanesulfonyloxy) propionate 2- Propynyl, di (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, di (2-propynyl) glutarate, 2-butyne-1,4-diyl dimethanesulfonate, 2-butyne- A compound containing one or more triple bonds selected from 1,4-diyl diformate and 2,4-hexadiyne-1,6-diyl dimethanesulfonate.
(E) 1,3-propane sultone, 1,3-butane sultone, 2,4-butane sultone, 1,4-butane sultone, 1,3-propene sultone, 2,2-dioxide-1,2-oxathiolan-4-yl Acetate, or sultone such as 5,5-dimethyl-1,2-oxathiolane-4-one 2,2-dioxide, ethylene sulfite, hexahydrobenzo [1,3,2] dioxathiolane-2-oxide (1,2 -Cyclohexanediol cyclic sulfite), or cyclic sulfites such as 5-vinyl-hexahydro-1,3,2-benzodioxathiol-2-oxide, butane-2,3-diyl dimethanesulfonate, butane Sulfone such as -1,4-diyl dimethane sulfonate or methylene methane disulfonate One or two or more cyclic or chain S═O groups selected from vinyl sulfone compounds such as acid esters, divinyl sulfone, 1,2-bis (vinylsulfonyl) ethane, or bis (2-vinylsulfonylethyl) ether Containing compound.
(F) Cyclic acetal compounds such as 1,3-dioxolane, 1,3-dioxane and 1,3,5-trioxane.

(G) Trimethyl phosphate, tributyl phosphate, trioctyl phosphate, tris (2,2,2-trifluoroethyl phosphate), bis (2,2,2-trifluoroethyl) methyl phosphate, bis phosphate (2,2,2-trifluoroethyl) ethyl, bis (2,2,2-trifluoroethyl) phosphate 2,2-difluoroethyl, bis (2,2,2-trifluoroethyl) phosphate 2, 2,3,3-tetrafluoropropyl, bis (2,2-difluoroethyl) phosphate 2,2,2-trifluoroethyl, bis (2,2,3,3-tetrafluoropropyl) phosphate 2,2 , 2-trifluoroethyl and phosphoric acid (2,2,2-trifluoroethyl) (2,2,3,3-tetrafluoropropyl) methyl, phosphoric acid tris (1,1,1,3,3,3 -Hexafull Lopropan-2-yl), methyl methylene bisphosphonate, ethyl methylene bisphosphonate, methyl ethylene bisphosphonate, ethyl ethylene bisphosphonate, methyl butylene bisphosphonate, ethyl butylene bisphosphonate, methyl 2- (dimethylphosphoryl) acetate, ethyl 2- ( Dimethylphosphoryl) acetate, methyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, methyl 2- (dimethoxy) Phosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) Tate, 2-propynyl 2- (dimethoxyphosphoryl) acetate, 2-propynyl 2- (diethoxyphosphoryl) acetate, and methyl pyrophosphate, one or two or more phosphorus-containing compound selected from ethyl pyrophosphate.
(H) Chain carboxylic anhydrides such as acetic anhydride and propionic anhydride, succinic anhydride, maleic anhydride, 3-allyl succinic anhydride, glutaric anhydride, itaconic anhydride, or 3-sulfo-propionic anhydride Cyclic acid anhydrides such as products.
(I) Cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, or ethoxyheptafluorocyclotetraphosphazene.

Among these, it is preferable to include at least one selected from (A) nitrile, (B) aromatic compound, and (C) isocyanate compound, since the electrochemical characteristics in a wider temperature range are further improved.

Among (A) nitriles, one or more selected from succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile are more preferable.
(B) Among aromatic compounds, one or more selected from biphenyl, terphenyl (o-, m-, p-isomer), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene Are more preferable, and one or more selected from biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene are particularly preferable.
Among the isocyanate compounds (C), one or more selected from hexamethylene diisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate are more preferable.

The content of each of the compounds (A) to (C) is preferably 0.01 to 7% by mass in the non-aqueous electrolyte. In this range, the film is sufficiently formed without becoming too thick, and the electrochemical characteristics in a wider temperature range are enhanced. The content is more preferably 0.05% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 5% by mass or less, further preferably 3% by mass or less. .

(D) Triple bond-containing compound, (E) Sultone, cyclic sulfite, sulfonic acid ester, cyclic S = O group-containing compound selected from vinyl sulfone, (F) cyclic acetal compound, (G) It is preferable to include a phosphorus-containing compound, (H) a cyclic acid anhydride, and (I) a cyclic phosphazene compound because the electrochemical properties in a wider temperature range are further improved.
(D) Triple bond-containing compounds include 2-propynyl methyl carbonate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinylsulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di Preferably, one or more selected from (2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, and 2-butyne-1,4-diyl dimethanesulfonate, 2-propynyl methanesulfonate, One or more selected from 2-propynyl vinyl sulfonate, 2-propynyl 2- (methanesulfonyloxy) propionate, di (2-propynyl) oxalate, and 2-butyne-1,4-diyl dimethanesulfonate More preferred .
(E) Cyclic or chain-containing S═O group-containing compound selected from sultone, cyclic sulfite, sulfonic acid ester, and vinyl sulfone (provided that the compound is a triple bond-containing compound and the specific formula (I)) It is preferable to use the above compound.

Examples of the cyclic S═O group-containing compound include 1,3-propane sultone, 1,3-butane sultone, 1,4-butane sultone, 2,4-butane sultone, 1,3-propene sultone, 2,2-dioxide- 1,2-oxathiolan-4-yl acetate, 5,5-dimethyl-1,2-oxathiolan-4-one 2,2-dioxide, methylene methane disulfonate, ethylene sulfite, ethylene sulfate, and 4- (methylsulfonyl) Preferable examples include one or more selected from methyl) -1,3,2-dioxathiolane 2-oxide.
The chain-like S═O group-containing compounds include butane-2,3-diyl dimethanesulfonate, butane-1,4-diyl dimethanesulfonate, dimethyl methane disulfonate, pentafluorophenyl methanesulfonate, divinylsulfone, And one or more selected from bis (2-vinylsulfonylethyl) ether are preferred.
Among the cyclic or chain-containing S═O group-containing compounds, 1,3-propane sultone, 1,4-butane sultone, 2,4-butane sultone, 2,2-dioxide-1,2-oxathiolan-4-yl acetate , Ethylene sulfate, pentafluorophenyl methanesulfonate, and one or more selected from divinylsulfone are more preferable.

(F) As the cyclic acetal compound, 1,3-dioxolane or 1,3-dioxane is preferable, and 1,3-dioxane is more preferable.
(G) Phosphorus-containing compounds include tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3-hexafluoropropan-2-yl), methyl 2- (dimethylphosphoryl) acetate, ethyl 2- (dimethylphosphoryl) acetate, methyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2 -(Diethylphosphoryl) acetate, methyl 2- (dimethoxyphosphoryl) acetate, ethyl 2- (dimethoxyphosphoryl) acetate, methyl 2- (diethoxyphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2-propynyl 2- (Dimethoxyphosphoryl) Cetate or 2-propynyl 2- (diethoxyphosphoryl) acetate is preferred, and tris phosphate (2,2,2-trifluoroethyl), tris phosphate (1,1,1,3,3,3-hexafluoro) Propan-2-yl), ethyl 2- (diethylphosphoryl) acetate, 2-propynyl 2- (dimethylphosphoryl) acetate, 2-propynyl 2- (diethylphosphoryl) acetate, ethyl 2- (diethoxyphosphoryl) acetate, 2- More preferred is propynyl 2- (dimethoxyphosphoryl) acetate or 2-propynyl 2- (diethoxyphosphoryl) acetate.
(H) The cyclic acid anhydride is preferably succinic anhydride, maleic anhydride, or 3-allyl succinic anhydride, more preferably succinic anhydride or 3-allyl succinic anhydride.
(I) As the cyclic phosphazene compound, a cyclic phosphazene compound such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, or phenoxypentafluorocyclotriphosphazene is preferable, and methoxypentafluorocyclotriphosphazene or ethoxypentafluorocyclo Triphosphazene is more preferred.

The content of each of the compounds (D) to (I) is preferably 0.001 to 5% by mass in the non-aqueous electrolyte. In this range, the film is sufficiently formed without becoming too thick, and the electrochemical characteristics in a wider temperature range are enhanced. The content is more preferably 0.01% by mass or more, more preferably 0.1% by mass or more in the non-aqueous electrolyte, and the upper limit thereof is more preferably 3% by mass or less, and further preferably 2% by mass or less. .

In addition, for the purpose of improving electrochemical characteristics in a wider temperature range, a lithium salt having an oxalic acid skeleton, a lithium salt having a phosphoric acid skeleton, and a lithium salt having an S═O group are further included in the non-aqueous electrolyte. It is preferable to include one or more lithium salts selected from the inside.
Specific examples of lithium salts include lithium bis (oxalato) borate [LiBOB], lithium difluoro (oxalato) borate [LiDFOB], lithium tetrafluoro (oxalato) phosphate [LiTFOP], and lithium difluorobis (oxalato) phosphate [LiDFOP]. at least one lithium salt with oxalic acid skeleton, LiPO ₂ F ₂ and _Li 2 PO ₃ lithium salt having a phosphate backbone such as F, lithium trifluoromethane selected from ((methanesulfonyl) oxy) borate [LiTFMSB], lithium Pentafluoro ((methanesulfonyl) oxy) phosphate [LiPFMSP], lithium methyl sulfate [LMS], lithium ethyl sulfate [LES], lithium 2,2,2-tri Le Oro ethylsulfate [LFES], and lithium salts suitably having one or more S = O group selected from _FSO 3 Li. Among these, it is more preferable to include a lithium salt selected from LiBOB, LiDFOB, LiTFOP, LiDFOP, LiPO ₂ F ₂ , LiTFMSB, LMS, LES, LFES, and FSO ₃ Li.

The proportion of the lithium salt in the non-aqueous solvent is preferably 0.001M or more and 0.5M or less. Within this range, the effect of improving electrochemical characteristics over a wide temperature range is further exhibited. Preferably it is 0.01M or more, More preferably, it is 0.03M or more, More preferably, it is 0.04M or more. The upper limit is preferably 0.4M or less, more preferably 0.2M or less. (However, M represents mol / L.)

(Electrolyte salt)
Preferred examples of the electrolyte salt used in the present invention include the following lithium salts.
Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ F) ₂ [LiFSI], LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , lithium salt containing a chain-like fluorinated alkyl group such as LiPF ₅ (iso-C ₃ F ₇ ), (CF ₂ ) ₂ (SO ₂ ) ₂ NLi, (CF ₂ ) ₃ (SO ₂ ) ₂ NLi Preferred examples include at least one lithium salt selected from lithium salts having a cyclic fluorinated alkylene chain, and the like, and these can be used alone or in combination. That.
Among these, one or more selected from LiPF ₆ , LiBF ₄ , LiN (SO ₂ F) ₂ [LiFSI], LiN (SO ₂ CF ₃ ) ₂ , and LiN (SO ₂ C ₂ F ₅ ) ₂ are included. Preferably, LiPF ₆ is most preferably used.

The concentration of the electrolyte salt is usually preferably 0.3 M or more, more preferably 0.7 M or more, and further preferably 1.1 M or more with respect to the non-aqueous solvent. Moreover, the upper limit is preferably 2.5M or less, more preferably 2.0M or less, and still more preferably 1.6M or less.
As the preferred combination of these electrolyte salts include LiPF _6, further _{LiBF 4, LiN (SO 2 CF} 3) 2, and at least one lithium salt selected from LiN _(SO 2 _{F) 2} [LiFSI] Is preferably contained in the non-aqueous electrolyte.
When the proportion of the lithium salt other than LiPF _{6 in the} non-aqueous solvent is 0.001M or more, the effect of improving the electrochemical characteristics in a wide temperature range is easily exhibited, and if it is 1.0M or less, the wide temperature range. This is preferable because there is little concern that the effect of improving the electrochemical characteristics of the material will decrease. Preferably it is 0.01M or more, More preferably, it is 0.03M or more, More preferably, it is 0.04M or more. The upper limit is preferably 0.8M or less, more preferably 0.6M or less, and still more preferably 0.4M or less.

[Production of non-aqueous electrolyte]
The non-aqueous electrolyte of the present invention is, for example, a compound containing the cyclopentane structure represented by the general formula (I) with respect to the electrolyte salt and the non-aqueous electrolyte mixed with the non-aqueous solvent. Can be obtained.
At this time, the compound represented by the general formula (I) to be added to the nonaqueous solvent and the nonaqueous electrolytic solution to be used should be purified in advance within a range that does not significantly reduce the productivity, and should have a minimum amount of impurities. preferable.

The nonaqueous electrolytic solution of the present invention can be used in the following first to fourth electric storage devices, and as the nonaqueous electrolyte, not only a liquid but also a gelled one can be used. Furthermore, the non-aqueous electrolyte of the present invention can be used for a solid polymer electrolyte. In particular, it is preferably used for the first electricity storage device (that is, for a lithium battery) or the fourth electricity storage device (that is, for a lithium ion capacitor) that uses a lithium salt as an electrolyte salt, and is used for a lithium battery. More preferably, it is more preferably used for a lithium secondary battery.

[First power storage device (lithium battery)]
The lithium battery as the first power storage device is a general term for a lithium primary battery and a lithium secondary battery, and the lithium secondary battery is used as a concept including a so-called lithium ion secondary battery.
The lithium battery of the present invention comprises the nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a positive electrode, a negative electrode, and a nonaqueous solvent. Components other than the non-aqueous electrolyte, such as a positive electrode and a negative electrode, can be used without particular limitation.
For example, as the positive electrode active material for a lithium secondary battery, a composite metal oxide with lithium containing one or more selected from the group consisting of cobalt, manganese, and nickel is used. These positive electrode active materials can be used alone or in combination of two or more.
Examples of such a lithium composite metal oxide include LiCoO ₂ , LiCo _1-x M _x O ₂ (where M is Sn, Mg, Fe, Ti, Al, Zr, Cr, V, Ga, Zn, and One or more elements selected from Cu, 0.001 ≦ x ≦ 0.05), LiMn ₂ O ₄ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01 <x <1), LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O ₂ , LiNi _0.8 Mn _{0 .1} Co _0.1 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , Li ₂ MnO ₃ and LiMO ₂ (M is a transition metal such as Co, Ni, Mn, Fe) , and _LiNi 1/2 _{Mn 3/2} O _One or two or more selected from ₄ are more preferable. Moreover, LiCoO ₂ and LiMn ₂ O _4, LiCoO ₂ and LiNiO _2, may be used in combination as LiMn ₂ O ₄ and LiNiO _2.

When a lithium composite metal oxide that operates at a high charging voltage is used, the electrochemical characteristics are generally likely to deteriorate in a high temperature environment due to a reaction with the electrolyte during charging. However, in the lithium secondary battery according to the present invention, The deterioration of these electrochemical characteristics can be suppressed.
In particular, when a positive electrode active material containing Ni is used, the nonaqueous solvent is generally decomposed on the surface of the positive electrode due to the catalytic action of Ni, and the resistance of the battery tends to increase. In particular, the electrochemical characteristics in a high temperature environment tend to be deteriorated. However, the lithium secondary battery according to the present invention is preferable because it can suppress the deterioration of these electrochemical characteristics. In particular, the positive electrode active material having a ratio of the atomic concentration of Ni to the atomic concentration of all transition metal elements in the positive electrode active material exceeding 10 atomic% is preferable because the above-described effect becomes remarkable, and the positive electrode active of 20 atomic% or more is preferable. It is more preferable to use a substance, and it is more preferable to use a positive electrode active material of 30 atomic% or more. Specifically, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _0.5 Mn _0.3 Co _0.2 O ₂ , LiNi _0.6 Mn _0.2 Co _0.2 O ₂ , One type or two or more types selected from LiNi _0.8 Mn _0.1 Co _0.1 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ are preferable.

Furthermore, lithium-containing olivine-type phosphate can also be used as the positive electrode active material. In particular, lithium-containing olivine-type phosphate containing one or more selected from iron, cobalt, nickel and manganese is preferable. Specific examples thereof include _one or more selected from LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMnPO ₄ , and LiFe _1-x Mn _x PO ₄ (0.1 <x <0.9).
Some of these lithium-containing olivine-type phosphates may be substituted with other elements, and some of iron, cobalt, nickel, and manganese are replaced with Co, Mn, Ni, Mg, Al, B, Ti, V, and Nb. , Cu, Zn, Mo, Ca, Sr, W, and Zr may be substituted with one or more elements selected from these, or may be coated with a compound or carbon material containing these other elements. Among these, LiFePO ₄ or LiMnPO ₄ is preferable.
Moreover, lithium containing olivine type | mold phosphate can also be mixed with the said positive electrode active material, for example, and can be used.
Lithium-containing olivine-type phosphate forms a stable phosphoric acid skeleton (PO ₄ ) structure and is excellent in thermal stability during charging, and therefore can improve electrochemical characteristics in a wide temperature range.

As the positive electrode for lithium primary _{battery, CuO, Cu 2 O, Ag} 2 O, Ag 2 CrO 4, CuS, CuSO 4, TiO 2, TiS 2, SiO 2, SnO, V 2 O 5, V 6 O 12 , VO _x , Nb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ Pb ₂ O ₅ , Sb ₂ O ₃ , CrO ₃ , Cr ₂ O ₃ , MoO ₃ , WO ₃ , SeO ₂ , MnO ₂ , Mn ₂ O ₃ , Fe ₂ O ₃ , FeO, Fe ₃ O ₄ , Ni ₂ O ₃ , NiO, CoO ₃ , CoO and other oxides or chalcogen compounds of one or more metal elements, sulfur such as SO ₂ and SOCl ₂ Examples thereof include a compound and fluorocarbon (fluorinated graphite) represented by the general formula (CF _x ) _n . Among _{these, MnO 2, V 2 O 5} , fluorinated graphite and the like are preferable.

The positive electrode conductive agent is not particularly limited as long as it is an electron conductive material that does not cause a chemical change. Examples thereof include graphite such as natural graphite (such as flake graphite) and artificial graphite, carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Further, graphite and carbon black may be appropriately mixed and used. The addition amount of the conductive agent to the positive electrode mixture is preferably 1 to 10% by mass, and more preferably 2 to 5% by mass.

The positive electrode is composed of a conductive agent such as acetylene black and carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), a copolymer of styrene and butadiene (SBR), acrylonitrile and butadiene. Mixture with binder such as copolymer (NBR), carboxymethyl cellulose (CMC), ethylene propylene diene terpolymer, etc., and knead by adding high boiling point solvent such as 1-methyl-2-pyrrolidone. After that, this positive electrode mixture was applied to a current collector aluminum foil, a stainless steel lath plate, etc., dried and pressure-molded, and then subjected to vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours. It can be manufactured by heat treatment.
The density of the portion excluding the current collector of the positive electrode is usually 1.5 g / cm ³ or more, and in order to further increase the capacity of the battery, preferably 2 g / cm ³ or more, more preferably 3 g / cm ³ or more, More preferably, it is 3.6 g / cm ³ or more. Moreover, the upper limit is preferably 4 g / cm ³ or less.

Examples of the negative electrode active material for a lithium secondary battery include lithium metal, lithium alloy, and carbon material capable of occluding and releasing lithium [easily graphitized carbon and difficult to have a (002) plane spacing of 0.37 nm or more. Graphitized carbon, graphite with (002) plane spacing of 0.34 nm or less, etc.], tin (single), tin compound, silicon (single), silicon compound, lithium titanate compound such as Li ₄ Ti ₅ O ₁₂ 1 type or 2 types or more chosen from etc. are mentioned.
Among these, it is more preferable to use a highly crystalline carbon material such as artificial graphite or natural graphite in terms of the ability to occlude and release lithium ions, and the lattice spacing ( ₀₀₂ ) has an interplanar spacing (d ₀₀₂ ) of 0.1. It is more preferable to use a carbon material having a graphite type crystal structure of 340 nm (nanometer) or less, particularly 0.335 to 0.337 nm.
In particular, artificial graphite particles having a massive structure in which a plurality of flat graphite fine particles are assembled or bonded non-parallel to each other, and mechanical actions such as compressive force, frictional force, shearing force, etc. are repeatedly applied, and scaly natural graphite is spherical. It is preferable to use particles that have been treated.

The peak intensity I (110) of the (110) plane of the graphite crystal obtained from the X-ray diffraction measurement of the negative electrode sheet when the density of the portion excluding the current collector of the negative electrode is pressed to a density of 1.5 g / cm ³ or more. ) And (004) plane peak intensity I (004) ratio I (110) / I (004) is preferably 0.01 or more, because the electrochemical characteristics in a wider temperature range are further improved. More preferably, it is more preferably 0.1 or more. In addition, since the crystallinity may be lowered due to excessive treatment and the discharge capacity of the battery may be lowered, the upper limit of the peak intensity ratio I (110) / I (004) is preferably 0.5 or less. 3 or less is more preferable.
In addition, it is preferable that the highly crystalline carbon material (core material) is coated with a carbon material having lower crystallinity than the core material because electrochemical characteristics in a wide temperature range are further improved. The crystallinity of the carbon material of the coating can be confirmed by TEM.
When a highly crystalline carbon material is used, it reacts with the non-aqueous electrolyte during charging and tends to lower the electrochemical characteristics at low or high temperatures due to an increase in interface resistance. However, in the lithium secondary battery according to the present invention, Excellent electrochemical characteristics over a wide temperature range.

Examples of the metal compound capable of inserting and extracting lithium as the negative electrode active material include Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, and Cu. , Zn, Ag, Mg, Sr, or a compound containing at least one metal element such as Ba. These metal compounds may be used in any form such as a simple substance, an alloy, an oxide, a nitride, a sulfide, a boride, and an alloy with lithium, but any of a simple substance, an alloy, an oxide, and an alloy with lithium. Is preferable because the capacity can be increased. Among these, those containing at least one element selected from Si, Ge and Sn are preferable, and those containing at least one element selected from Si and Sn are particularly preferable because the capacity of the battery can be increased.

The negative electrode is kneaded using the same conductive agent, binder, and high-boiling solvent as in the production of the positive electrode, and then the negative electrode mixture is applied to the copper foil of the current collector. After being dried and pressure-molded, it can be produced by heat treatment under vacuum at a temperature of about 50 ° C. to 250 ° C. for about 2 hours.
The density of the portion excluding the current collector of the negative electrode is usually 1.1 g / cm ³ or more, and is preferably 1.5 g / cm ³ or more, more preferably 1.7 g in order to further increase the battery capacity. / Cm ³ or more. The upper limit is preferably 2 g / cm ³ or less.

Also, examples of the negative electrode active material for a lithium primary battery include lithium metal and lithium alloy.

The structure of the lithium battery is not particularly limited, and a coin-type battery, a cylindrical battery, a square battery, a laminated battery, or the like having a single-layer or multi-layer separator can be applied.
The battery separator is not particularly limited, and a single layered or laminated microporous film of polypropylene, polyethylene, ethylene-propylene copolymer or the like, a woven fabric, a nonwoven fabric, or the like can be used.
The polyolefin laminate is preferably a laminate of polyethylene and polypropylene, more preferably a three-layer structure of polypropylene / polyethylene / polypropylene.
The thickness of a separator becomes like this. Preferably it is 2 micrometers or more, More preferably, it is 3 micrometers or more, More preferably, it is 4 micrometers or more, and the upper limit is 30 micrometers or less, Preferably it is 20 micrometers or less, More preferably, it is 15 micrometers or less.

The lithium secondary battery according to the present invention has excellent electrochemical characteristics in a wide temperature range even when the end-of-charge voltage is 4.2 V or more, particularly 4.3 V or more, and the characteristics are also good at 4.4 V or more. is there. The end-of-discharge voltage is usually 2.8 V or more, and further 2.5 V or more, but the lithium secondary battery in the present invention can be 2.0 V or more. The current value is not particularly limited, but is usually used in the range of 0.1 to 30C. Further, the lithium battery in the present invention can be charged / discharged at −40 to 100 ° C., preferably −10 to 80 ° C.

In the present invention, as a countermeasure against an increase in internal pressure of the lithium battery, a method of providing a safety valve on the battery lid or cutting a member such as a battery can or a gasket can be employed. Further, as a safety measure for preventing overcharge, the battery lid can be provided with a current interruption mechanism that senses the internal pressure of the battery and interrupts the current.

[Second power storage device (electric double layer capacitor)]
The 2nd electrical storage device of this invention is an electrical storage device which stores the energy using the electric double layer capacity | capacitance of electrolyte solution and an electrode interface including the non-aqueous electrolyte of this invention. An example of the present invention is an electric double layer capacitor. The most typical electrode active material used for this electricity storage device is activated carbon. Double layer capacity increases roughly in proportion to surface area.

[Third power storage device]
The 3rd electrical storage device of this invention is an electrical storage device which stores the energy using the dope / dedope reaction of an electrode including the non-aqueous electrolyte of this invention. Examples of the electrode active material used in this power storage device include metal oxides such as ruthenium oxide, iridium oxide, tungsten oxide, molybdenum oxide, and copper oxide, and π-conjugated polymers such as polyacene and polythiophene derivatives. Capacitors using these electrode active materials can store energy associated with electrode doping / dedoping reactions.

[Fourth storage device (lithium ion capacitor)]
The 4th electrical storage device of this invention is an electrical storage device which stores the energy using the intercalation of lithium ion to carbon materials, such as a graphite which is a negative electrode, containing the non-aqueous electrolyte of this invention. It is called a lithium ion capacitor (LIC). Examples of the positive electrode include those using an electric double layer between an activated carbon electrode and an electrolytic solution, and those using a π-conjugated polymer electrode doping / dedoping reaction. The electrolytic solution contains at least a lithium salt such as LiPF ₆ .

Examples of the electrolytic solution using the compound of the present invention are shown below, but the present invention is not limited to these examples.

Examples 1 to 16, Comparative Examples 1 to 4
[Production of lithium ion secondary battery]
LiNi _0.6 Mn _0.2 Co _0.2 O ₂ 93% by mass and acetylene black (conductive agent) 4% by mass are mixed, and 3% by mass of polyvinylidene fluoride (binder) is preliminarily added to 1-methyl-2- A positive electrode mixture paste was prepared by adding to and mixing with the solution dissolved in pyrrolidone. This positive electrode mixture paste was applied to one side of an aluminum foil (current collector), dried and pressurized, and cut into a predetermined size to produce a positive electrode sheet. The density of the portion excluding the current collector of the positive electrode was 3.6 g / cm ³ .
Further, 5% by mass of silicon (single substance), artificial graphite (d ₀₀₂ = 0.335 nm, negative electrode active material) 85% by mass, and 5% by mass of acetylene black (conductive agent) are mixed, and polyvinylidene fluoride (binder) in advance. 5% by mass was added to a solution dissolved in 1-methyl-2-pyrrolidone and mixed to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied to one side of a copper foil (current collector), dried and pressurized, and cut into a predetermined size to produce a negative electrode sheet. The density of the portion excluding the current collector of the negative electrode was 1.6 g / cm ³ . As a result of X-ray diffraction measurement using this electrode sheet, the ratio of the peak intensity I (110) of the (110) plane of the graphite crystal to the peak intensity I (004) of the (004) plane [I (110) / I (004)] was 0.1.
Then, a positive electrode sheet, a separator made of a microporous polyethylene film, and a negative electrode sheet were laminated in this order, and a non-aqueous electrolyte solution having the composition shown in Tables 1 and 2 was added to produce a laminated battery.

[Evaluation of low temperature characteristics after high temperature charge storage]
<Initial discharge capacity>
Using the laminated battery produced by the above method, in a constant temperature bath at 25 ° C., charge at a constant current of 1 C and a constant voltage for 3 hours to a final voltage of 4.3 V, and reduce the temperature of the constant temperature bath to −10 ° C. The battery was discharged to a final voltage of 2.7 V under a constant current of 1 C, and an initial discharge capacity of −10 ° C. was determined.
<High-temperature charge storage test>
Next, this coin battery was charged in a constant temperature bath of 70 ° C. with a constant current and a constant voltage of 1 C for 3 hours to a final voltage of 4.3 V, and stored for 10 days while being maintained at 4.3 V. Then, it put into the thermostat of 25 degreeC, and discharged once to the final voltage 2.7V under the constant current of 1C.
<Low-temperature discharge capacity maintenance rate after high-temperature charge storage>
Thereafter, similarly to the measurement of the initial discharge capacity, the discharge capacity retention rate at −10 ° C. after storage at high temperature was obtained by the following formula.
−10 ° C. discharge capacity retention ratio after storage at 70 ° C. (%) = (− 10 ° C. discharge capacity after 70 ° C. charge storage / initial discharge capacity at −10 ° C.) × 100
The results are shown in Tables 1-2.
In addition, EP used in Example 8 in Table 1 is an abbreviation for ethyl propionate.

 

 

 

 

Examples 17 to 18 and Comparative Example 5
In place of the negative electrode active material used in Example 1, a negative electrode sheet was prepared using lithium titanate Li ₄ Ti ₅ O ₁₂ (negative electrode active material). 85% by mass of lithium titanate and 10% by mass of acetylene black (conductive agent) are mixed and added to a solution in which 5% by mass of polyvinylidene fluoride (binder) is previously dissolved in 1-methyl-2-pyrrolidone. The mixture was mixed to prepare a negative electrode mixture paste. This negative electrode mixture paste was applied onto a copper foil (current collector), dried, pressurized and cut into a predetermined size to produce a negative electrode sheet, and the end-of-charge voltage during battery evaluation was 2 A laminated battery was prepared and evaluated in the same manner as in Example 1 except that the voltage was .75 V, the discharge end voltage was 1.1 V, and the composition of the nonaqueous electrolyte was changed to a predetermined value. The results are shown in Table 3.

 

 

In any of the lithium secondary batteries of Examples 1 to 16, Comparative Example 1 and ethylene glycol in which the sulfate or sulfite represented by the general formula (I) was not added to the non-aqueous electrolyte of the present invention Comparative Example 2 when sulfate ester was added, Comparative Example 3 when hexahydro 1,3,2-benzodioxathiol 2,2-dioxide was added, and 1,2-cyclopentanediol cyclic carbonate were added In comparison with the lithium secondary battery of Comparative Example 4, the electrochemical characteristics in a wide temperature range are remarkably improved. From the above, the effect of the present invention is a unique effect when the sulfate or sulfite represented by the general formula (I) is contained in the non-aqueous electrolyte in which the electrolyte salt is dissolved in the non-aqueous solvent. It turned out to be.
Further, from the comparison between Examples 17 to 18 and Comparative Example 5, it is clear that the same effect is observed when lithium titanate is used for the negative electrode, and therefore it is not an effect dependent on the specific positive electrode or the negative electrode. .

Furthermore, the non-aqueous electrolyte of the present invention has an effect of improving the discharge characteristics in a wide temperature range of the lithium primary battery.

If the nonaqueous electrolytic solution for an electricity storage device of the present invention is used, an electricity storage device having excellent electrochemical characteristics in a wide temperature range can be obtained. Especially when used as a non-aqueous electrolyte for electricity storage devices such as lithium secondary batteries mounted on hybrid electric vehicles, plug-in hybrid electric vehicles, battery electric vehicles, etc., the electricity storage devices are unlikely to deteriorate in electrochemical characteristics over a wide temperature range. Can be obtained.

Claims (10)

A non-aqueous electrolyte in which an electrolyte salt is dissolved in a non-aqueous solvent, wherein the non-aqueous electrolyte contains 0.01 to 10% by mass of a compound represented by the following general formula (I) A non-aqueous electrolyte for an electricity storage device.

(In the formula, X represents an S (═O) ₂ group or an S═O group, and R ¹ to R ⁸ each independently represents a hydrogen atom, a halogen atom, or a part of the hydrogen atom is substituted with a halogen atom. And an optionally substituted alkyl group having 1 to 4 carbon atoms.) R ^{1 -} R ⁸ in the general formula (I) are each independently a hydrogen atom, is a fluorine atom, or partially alkyl group having 1 carbon atoms which may be 3-substituted by fluorine atoms of the hydrogen atom The non-aqueous electrolyte for electrical storage devices of Claim 1. The compound represented by the general formula (I) is tetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2-dioxide, 4-fluorotetrahydro-4H-cyclopenta [d] [1] , 3,2] dioxathiol-2,2-dioxide, 4-methyltetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2,2-dioxide, tetrahydro-4H-cyclopenta [d ] [1,3,2] dioxathiol-2-oxide, 4-fluorotetrahydro-4H-cyclopenta [d] [1,3,2] dioxathiol-2-oxide, and 4-methyltetrahydro-4H- 3. The electricity storage device according to claim 1, which is one or more selected from cyclopenta [d] [1,3,2] dioxathiol-2-oxide. Aqueous electrolyte. The nonaqueous electrolytic solution for an electricity storage device according to any one of claims 1 to 3, wherein the nonaqueous solvent contains a cyclic carbonate and a chain ester. The cyclic carbonate is one or more selected from ethylene carbonate, propylene carbonate, 4-fluoro-1,3-dioxolan-2-one, vinylene carbonate, and 4-ethynyl-1,3-dioxolan-2-one. The nonaqueous electrolyte solution for electrical storage devices of Claim 4 containing. 6. The nonaqueous electrolytic solution for an electricity storage device according to claim 4, wherein the chain ester includes both a symmetric chain carbonate and an asymmetric chain carbonate, and the symmetric chain carbonate is more contained than the asymmetric chain carbonate. An electricity storage device comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte solution in which an electrolyte salt is dissolved in a nonaqueous solvent, wherein the nonaqueous electrolyte solution is the nonaqueous electrolyte solution according to any one of claims 1 to 6. An electricity storage device characterized by being. As the negative electrode active material, the negative electrode is one or more selected from lithium metal, lithium alloy, carbon material capable of inserting and extracting lithium, tin, tin compound, silicon, silicon compound, and lithium titanate compound The electrical storage device of Claim 7 containing. The positive electrode contains a composite metal oxide with lithium containing one or more selected from cobalt, manganese, and nickel, or a lithium-containing olivine-type phosphate as a positive electrode active material. Power storage device. The electricity storage device according to any one of claims 7 to 9, wherein the electricity storage device is a lithium secondary battery or a lithium ion capacitor.