JP2003338317A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery having high capacity and excellent storage characteristics, load characteristics and cycle characteristics while ensuring safety during overcharge. The non-aqueous electrolyte secondary battery includes at least a negative electrode capable of inserting and extracting lithium, a positive electrode, and an electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent. A compound that reacts at a voltage equal to or higher than the maximum operating voltage of the battery when overcharged in a solvent, at least one compound selected from the group consisting of cyclic carbonates having an unsaturated bond and acid anhydrides, and a sulfur-containing organic compound; A non-aqueous electrolyte secondary battery containing:

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous liquid electrolyte secondary battery that ensures safety during overcharge, has high capacity, and is excellent in storage characteristics, load characteristics, and cycle characteristics.

[0002]

2. Description of the Related Art In recent years, as electronic devices have been reduced in size and weight, a negative electrode capable of inserting and extracting lithium, a positive electrode, and an electrolytic solution prepared by dissolving a lithium salt in a non-aqueous solvent. The non-aqueous electrolyte secondary battery using is, has a high voltage and high energy density, and is excellent in storability,
It has come to be widely used as a power source for consumer electronic devices such as handy video cameras and portable personal computers. A non-aqueous electrolyte secondary battery that exhibits a battery function by inserting and extracting lithium ions is called a lithium ion secondary battery, and its development and competition for commercialization are intensifying. Further, due to environmental problems, attention has been focused on a sealed, maintenance-free lithium-ion secondary battery with a large capacity and a high energy density, such as for electric vehicles and for load leveling of electric power.

Since the positive electrode active material of a lithium ion secondary battery has a large capacity per weight, it is mainly composed of a lithium transition metal composite such as layered lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ). Oxides are used, but they have major problems. This is because these lithium-transition metal composite oxides become very unstable in an overcharged state (a state in which most of the lithium ions are desorbed), causing a rapid exothermic reaction with the electrolyte solution, or depositing lithium metal on the negative electrode. This causes the battery to burst or ignite in the worst case.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. 9-106835 discloses that the inside of the battery is mixed by mixing an additive that is polymerized at a battery voltage higher than the maximum operating voltage of the battery into the electrolytic solution. It has been proposed to increase the resistance to protect the battery, and Japanese Patent Application Laid-Open No. 9-171840 discloses generating gas and pressure by polymerizing in an electrolytic solution at a battery voltage higher than the maximum operating voltage of the battery. It has been proposed that the internal electric disconnecting device provided for overcharge protection be surely operated by mixing the additives, and aromatic compounds such as biphenyl, thiophene, and furan are disclosed as the additives. .

Further, various aromatic compounds have been proposed to improve safety during overcharge. However, when these compounds are added, there is a problem in that the discharge characteristics of the battery during normal use, particularly the discharge characteristics after high temperature storage, are significantly deteriorated while having an effect on safety during overcharge. In order to solve such a problem, Japanese Patent Laid-Open No. 2001-12
Japanese Patent No. 6765 proposes to contain biphenyl and propane sultone in an electrolytic solution as a battery capable of suppressing burst damage to the battery during overcharge and suppressing a decrease in recovery capacity after high temperature storage. Although some effects were observed, the load characteristics and cycle characteristics were not sufficient.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and assures safety during overcharge, has a high capacity, and is excellent in storage characteristics, load characteristics, and cycle characteristics. An object is to provide an aqueous electrolyte secondary battery.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has confirmed the safety at the time of overcharging by using an electrolytic solution of a specific composition, The inventors have found that the characteristics and cycle characteristics can be improved, and completed the present invention.

[0008] That is, the gist of the present invention is a non-aqueous electrolyte solution comprising at least a negative electrode capable of inserting and extracting lithium, a positive electrode, and an electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent. In the next battery, a compound that reacts in the non-aqueous solvent at a voltage equal to or higher than the maximum operating voltage of the battery when overcharged, and at least one compound selected from the group consisting of a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride. , A non-aqueous electrolyte secondary battery containing a sulfur-containing organic compound.

Another object of the present invention is a non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery, which comprises a negative electrode capable of inserting and extracting at least lithium and a positive electrode.
The non-aqueous electrolytic solution is composed of at least a non-aqueous solvent and a lithium salt, a compound that reacts in the non-aqueous solvent at a voltage higher than the maximum operating voltage of the battery during overcharge, a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride A non-aqueous electrolyte solution for a secondary battery, which comprises at least one compound selected from the group consisting of a substance and a sulfur-containing organic compound.

The reason why the storage characteristics are improved by using the above electrolytic solution is not clear enough. Conventionally, a compound (overcharge inhibitor) that reacts at a voltage higher than the maximum operating voltage of the battery during overcharging is more likely to react on the positive electrode and the negative electrode than the solvent component of the electrolytic solution. If they react at a highly active site, and these compounds react, the internal resistance of the battery increases greatly, and gas generation causes a significant reduction in the discharge characteristics after high temperature storage. In the present invention, an electrolytic solution containing at least one compound selected from the group consisting of a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride and a sulfur-containing organic compound is used. The cyclic carbonic acid ester or acid anhydride having a bond efficiently forms a film of a reduction reaction product derived from the cyclic carbonic acid ester on the surface of the negative electrode from the time of initial charging, and the film is stable even in a high temperature environment. Suppresses the reaction between the charge inhibitor and the negative electrode, and
Sulfur-containing organic compounds suppress the reactivity of the positive electrode by adsorption or reaction on the active site of the positive electrode, and suppress the reaction between the overcharge inhibitor and the positive electrode, which significantly reduces the discharge characteristics after high temperature storage. Is thought to be suppressed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The non-aqueous electrolyte solution for a secondary battery of the present invention is composed of at least a non-aqueous solvent and a lithium salt,
A compound that reacts in the non-aqueous solvent at a voltage higher than the maximum operating voltage of the battery when overcharged, at least one compound selected from the group consisting of cyclic ester carbonates and acid anhydrides having an unsaturated bond, and a sulfur-containing organic compound And a compound.

The non-aqueous solvent used in the present invention contains a compound (overcharge inhibitor) which reacts at a voltage higher than the maximum operating voltage of the battery during overcharge. The compound that reacts at a voltage higher than the maximum operating voltage of the battery during overcharge (overcharge inhibitor) is not particularly limited, but when a lithium-containing transition metal oxide is used as the positive electrode active material, it does not react in the normal operating potential range. However, a substance that reacts at around 4.5 V is preferable, and an aromatic compound is mainly used. Specific examples of the overcharge inhibitor include biphenyl, alkylbiphenyl, terphenyl,
Partial hydrogenated products of terphenyl, cyclohexylbenzene, diphenyl ether, benzofuran, dibenzofuran, and their halides such as 2-fluorobiphenyl, mainly fluorinated compounds, and 2,4-difluoroanisole, 2,5-difluoroanisole, 2 Examples thereof include fluorine-containing anisole compounds such as 6,6-difluoroanisole, and these compounds may be used as a mixture of two or more kinds.

The content of the overcharge inhibitor in the non-aqueous solvent is not particularly limited, but is preferably 0.01 to 5% by weight, more preferably 0.1 to 4% by weight. The non-aqueous solvent used in the present invention contains a compound selected from a cyclic carbonic acid ester having an unsaturated bond or an acid anhydride. The cyclic carbonic acid ester having an unsaturated bond is not particularly limited, and examples thereof include vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, 4,5-dimethylvinylene carbonate, 4,5-diethylvinylene carbonate, fluorovinylene carbonate, trifluoromethyl. Vinylene carbonate compounds such as vinylene carbonate, 4-vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, 4-ethyl-4-
Vinyl ethylene carbonate, 4-n-propyl-4-
Vinyl ethylene carbonate, 5-methyl-4-vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, 4,5-divinyl ethylene carbonate,
4,4-dimethyl-5-methyleneethylene carbonate, 4,4-diethyl-5-methyleneethylene carbonate and the like can be mentioned. Among them, vinylene carbonate, 4
-Vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate and 4,5-divinylethylene carbonate are preferable, and vinylene carbonate and 4-vinylethylene carbonate are more preferable.

The acid anhydride is not particularly limited, either.
It may be a compound having a plurality of acid anhydride structures in one molecule. Specific examples of the acid anhydride, acetic anhydride, propionic anhydride, butyric anhydride, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic acid, cyclohexane. Dicarboxylic acid anhydride, cyclopentanetetracarboxylic acid dianhydride, 4-cyclohexene-1,2-dicarboxylic acid anhydride, 3,4,5,6-tetrahydrophthalic acid anhydride, 5-norbornene-2,3-dicarboxylic acid Examples thereof include acid anhydride, phenylsuccinic anhydride, 2-phenylglutaric anhydride, phthalic anhydride and pyromellitic dianhydride. Among them, preferred is succinic anhydride,
Glutaric anhydride and cyclohexanedicarboxylic acid anhydride.

The cyclic carbonic acid ester or acid anhydride having an unsaturated bond may be used as a mixture of two or more kinds. The content of the compound selected from the cyclic carbonic acid ester having an unsaturated bond or the acid anhydride in the non-aqueous solvent is not particularly limited, but is preferably 0.01 to 5% by weight, more preferably 0.1 to 5% by weight. Is. Above all, in the case of a cyclic carbonic acid ester having an unsaturated bond, it is preferably 0.1 to 4% by weight, and in the case of an acid anhydride, it is preferably 0.1 to 3% by weight.

The non-aqueous solvent used in the present invention contains a sulfur-containing organic compound. The sulfur-containing organic compound is not particularly limited, for example, ethylene sulfite, propylene sulfite, butylene sulfite, vinylene sulfite, cyclic sulfite such as tetrahydrofuran sulfite, dimethyl sulfite, diethyl sulfite, ethyl methyl sulfite, Chain sulfites such as methylpropyl sulfite and ethylpropyl sulfite, halides of the above cyclic sulfites and chain sulfites, sulfolane, 2-methylsulfolane, 3-
Cyclic sulfones such as methylsulfolane, 2-ethylsulfolane, 3-ethylsulfolane, 2,4-dimethylsulfolane, sulfolene, 2-methylsulfolene, 3-methylsulfolene, dimethylsulfone, diethylsulfone,
Chain sulfones such as ethylmethyl sulfone, methylpropyl sulfone, ethylpropyl sulfone, divinyl sulfone, methyl vinyl sulfone, diphenyl sulfone and dibenzyl sulfone, halides of the above cyclic sulfones and chain sulfones, 1,3-propane sultone, Cyclic sulfonates such as 1,4-butane sultone, 2,4-butane sultone, 1,3-butane sultone, 3-phenyl-1,3-propane sultone, 4-phenyl-1,4-butane sultone, methyl methane sulfonate, Ethyl methane sulfonate, propyl methane sulfonate, methyl ethane sulfonate, ethyl ethane sulfonate, propyl ethane sulfonate, methyl benzene sulfonate, ethyl benzene sulfonate, propyl benzene sulfonate, phenyl methane sulfonate , Chain sulfonates such as phenyl ethane sulfonate, phenyl propane sulfonate, methyl benzyl sulfonate, ethyl benzyl sulfonate, propyl benzyl sulfonate, benzyl methane sulfonate, benzyl ethane sulfonate, benzyl propane sulfonate, and busarufan, The above-mentioned cyclic sulfonate ester or chain sulfonate halide, ethylene glycol sulfate ester, 1,2-propanediol sulfate ester, 1,3-propanediol sulfate ester, 1,2-butanediol sulfate ester, 1,3 -Cyclic sulfates such as butanediol sulfate, 2,3-butanediol sulfate, phenylethylene glycol sulfate, dimethyl sulfate, diethyl sulfate,
Chain sulfates such as ethyl methyl sulfate, methyl propyl sulfate, ethyl propyl sulfate, methyl phenyl sulfate, ethyl phenyl sulfate, phenyl propyl sulfate, benzyl methyl sulfate and benzyl ethyl sulfate, and halides of the above cyclic sulfates and chain sulfates. , And the like, and among them, ethylene sulfite, 1,3-propane sultone, dimethyl sulfone, and methyl methanesulfonate are preferable. You may use these sulfur-containing organic compounds in mixture of 2 or more types.

The content of the sulfur-containing organic compound in the non-aqueous solvent is not particularly limited, but is preferably 0.01 to 5% by weight,
More preferably 0.1 to 5% by weight, and even more preferably 0.1.
It is 1 to 3% by weight. Furthermore, in the present invention, when a compound selected from a fluorine-containing aromatic compound having 9 or less carbon atoms, an aliphatic hydrocarbon or a fluorine-containing aliphatic hydrocarbon compound is contained in the non-aqueous solvent, a large current discharge after high temperature storage The characteristics can be improved.

The fluorine-containing aromatic compound having 9 or less carbon atoms is not particularly limited, and examples thereof include fluorobenzene, 1,2
-Difluorobenzene, 1,3-difluorobenzene,
1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,
3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene,
Pentafluorobenzene, hexafluorobenzene, 2
-Fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-
Difluorotoluene, 2,5-difluorotoluene,
2,6-difluorotoluene, 3,4-difluorotoluene, benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 3-fluoro-o-xylene, 4-fluoro -O-xylene, 2-
Examples thereof include fluoro-m-xylene, 5-fluoro-m-xylene, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride and octafluorotoluene.

The above-mentioned aliphatic hydrocarbon is not particularly limited,
For example, hexane, heptane, octane, nonane, decane, 2-methylhexane, 3-methylhexane, 2-methylheptane, 3-methylheptane, cyclohexane,
Examples include cycloheptane, cyclooctane, methylcyclohexane, ethylcyclohexane, butylcyclohexane, dicyclohexyl, decalin and the like.

Examples of the above-mentioned fluorine-containing aliphatic hydrocarbon compound include fluorinated compounds of the above aliphatic hydrocarbons such as 1-fluorohexane and 1-fluoroheptane. Among the compounds selected from the fluorine-containing aromatic compounds having 9 or less carbon atoms, the aliphatic hydrocarbons and the fluorine-containing aliphatic hydrocarbon compounds, fluorobenzene, benzotrifluoride and heptane are preferable. These compounds are 2
You may mix and use 1 or more types.

The content of these compounds in the non-aqueous solvent is not particularly limited, but is preferably 0.1 to 10% by weight, more preferably 0.2 to 5% by weight. When a non-aqueous solvent contains a fluorine-containing aromatic compound having 9 or less carbon atoms, an aliphatic hydrocarbon or a fluorine-containing aliphatic hydrocarbon compound,
Since these compounds are relatively stable against oxidation and reduction, their presence on the surface of the positive electrode and the negative electrode
It is considered that the opportunity for the overcharge inhibitor to react on the surfaces of the positive electrode and the negative electrode is reduced, and as a result, the large current discharge characteristics after high temperature storage can be improved. The non-aqueous solvent used in the present invention is not particularly limited, and examples thereof include cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate and dialkyl carbonate such as ethylmethyl carbonate. (It is preferable that the alkyl group has 1 to 4 carbon atoms), cyclic ether such as tetrahydrofuran and 2-methyltetrahydrofuran, chain ether such as dimethoxyethane and dimethoxymethane, cyclic ester such as γ-butyrolactone and γ-valerolactone. , Chain esters such as methyl acetate, methyl propionate and ethyl propionate, and phosphorus-containing organic solvents such as trimethyl phosphate and triethyl phosphate. You may use these solvents in mixture of 2 or more types.

The non-aqueous solvent contains 20% by volume or more of an alkylene carbonate having an alkylene group having 2 to 4 carbon atoms and a dialkyl carbonate having an alkyl group having 1 to 4 carbon atoms, and these carbonates are contained. Is preferably a mixed solvent which occupies 70% by volume or more of the whole, because the electrolytic solution has high electric conductivity, cycle characteristics and large current discharge characteristics. The alkylene group has 2 to 4 carbon atoms.
Specific examples of the alkylene carbonate can include ethylene carbonate, propylene carbonate, butylene carbonate and the like, and among these, ethylene carbonate and propylene carbonate are preferable.

Specific examples of the dialkyl carbonate in which the alkyl group has 1 to 4 carbon atoms include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethylmethyl carbonate and methyl-n-.
Examples include propyl carbonate and ethyl-n-propyl carbonate. Of these, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferred.

As another preferred embodiment of the non-aqueous solvent, one containing one or more solvents having a relative dielectric constant of 25 or more in a proportion of 60% by volume or more, and particularly 85% or more, the boiling point of the solvent itself is It is relatively high, and it is preferable because it has less problems of volatilization and liquid leakage even at high temperatures. Examples of the non-aqueous solvent having a relative dielectric constant of 25 or more include ethylene carbonate, propylene carbonate, γ-butyrolactone, and γ-valerolactone. Those containing ethylene carbonate are particularly preferable, and among them, ethylene carbonate is 5% by volume. Or more and mixed solvent occupying 55% by volume or more of γ-butyrolactone, and 30% by volume of ethylene carbonate
Above all, a mixed solvent containing propylene carbonate in an amount of 30% by volume or more is more preferable because the generation of gas during high temperature storage is small, the cycle characteristics and the large current discharge characteristics are well balanced.

The non-aqueous electrolyte of the present invention may be mixed with other useful compounds such as conventionally known additives, dehydrating agents and deoxidizing agents. For example, conventionally known additives such as fluoroethylene carbonate, trifluoropropylene carbonate, and other fluorinated carbonates, 1-methyl-
2-pyrrolidinone, 1-methyl-2-piperidone, 3-
Methyl-2-oxazolidinone, 1,3-dimethyl-2
-When 0.1 to 5% by weight of a nitrogen-containing compound such as imidazolidinone and N-methylsuccinimide is contained, the capacity retention characteristics and cycle characteristics are better than when not containing it. .

Further, the non-aqueous electrolyte solution contains a separator.
A surfactant is used to improve the wettability with the electrode and electrode material.
You may add in 0.01-2 weight%. In the present invention
As the solute of the non-aqueous electrolyte used, lithium salt is
Used. For lithium salt, use as a solute
It is not particularly limited as long as it can be obtained, but specific examples thereof
Then LiClO_Four, LiPF₆, LiBF_FourChoose from
Inorganic lithium salt, LiCF₃SO₃, LiN (CF₃
SO₂)₂, LiN (C₂F_FiveSO ₂)₂, LiN (CF₃S
O₂) (C_FourF₉SO₂), LiC (CF₃SO₂)₃, Li
PF_Four(CF₃)₂, LiPF_Four(C₂F_Five)₂, LiPF
_Four(CF₃SO₂)₂, LiPF_Four(C₂F_FiveSO₂)₂, Li
BF₂(CF₃)₂, LiBF₂(C₂F_Five)₂, LiBF
₂(CF₃SO₂)₂, LiBF₂(C₂F_FiveSO₂)₂Etc.
Fluoroorganic lithium salts may be mentioned. Among these, dissolve
Of LiPF,
₆, LiBF_Four, LiCF₃SO₃, LiN (CF₃SO₂)
₂, LiN (C₂F_FiveSO₂)₂Is preferred, and LiPF₆, L
iBF_FourIs more preferable. Note that there are two or more types of these solutes.
You may mix and use above.

Further, an inorganic lithium salt selected from LiPF ₆ or LiBF ₄ , LiCF ₃ SO ₃ and LiN (CF ₃
The combined use of two or more lithium salts of a fluorine-containing organic lithium salt selected from SO ₂ ) ₂ or LiN (C ₂ F ₅ SO ₂ ) ₂ tends to suppress deterioration after storage at high temperature, which is preferable. When a non-aqueous solvent containing 60% by weight or more of γ-butyrolactone is selected as the non-aqueous solvent, L
It is preferable that iBF ₄ is 50% by weight or more of the whole lithium salt.

The concentration of the solute lithium salt in the non-aqueous electrolyte is usually preferably 0.5 to 3 mol / liter. If the concentration is too high or too low, the electric conductivity of the electrolytic solution is low, and the battery performance tends to deteriorate. As the material of the negative electrode constituting the secondary battery of the present invention, a carbonaceous material capable of occluding and releasing lithium such as a pyrolyzed product of an organic substance under various pyrolysis conditions or artificial graphite, natural graphite, tin oxide,
A metal oxide material capable of inserting and extracting lithium such as silicon oxide, lithium metal, or various lithium alloys can be used. You may use these negative electrode materials in mixture of 2 or more types.

Specific examples of the carbonaceous material capable of inserting and extracting lithium include pyrolyzed products of organic substances under various pyrolysis conditions, artificial graphite, natural graphite and the like. Preferably, artificial graphite and purified natural graphite produced by high temperature heat treatment of graphitizable pitch obtained from various raw materials, or materials obtained by subjecting these graphites to various surface treatments including pitch are mainly used.

In the above graphite material, the d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by Gakushin method is 0.3.
35 to 0.338 nm, especially 0.335 to 0.3
It is preferably 37 nm. The ash content is preferably 1% by weight or less, more preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less. In addition, the crystallite size (L
c) is preferably 30 nm or more, more preferably 50 nm or more, and particularly preferably 100 nm or more.

The median diameter of the carbonaceous material powder obtained by the laser diffraction / scattering method is preferably 1 to 100 μm, more preferably 3 to 50 μm, and 5 to 4 μm.
The thickness is more preferably 0 μm, particularly preferably 7 to 30 μm. BET specific surface area is 0.3 to 25.
It is preferably from 0m ² / g, 0.5~20.0m ² /
g is more preferable, and 0.7 to 15.0 m ² / g
Is more preferable, and 0.8 to 10.0 m ² / g is particularly preferable. Further, when Raman spectrum analysis is performed on the powder having the adjusted diameter by using an argon ion laser beam, the peak P _A (peak intensity I _A ) and 1300 to 1400 cm ^{−1 in} the range of 1570 to 1620 cm ^−1.
Intensity ratio R = I _B of the peak P _B (peak intensity I _B ) in the range
/ I _A is preferably 0.01 to 0.7, 1570-16
The full width at half maximum of the peak in the range of 20 cm ^-1 is 26 cm ^-1 or less,
In particular, it is preferably 25 cm ^-1 or less.

The method for producing a negative electrode using these negative electrode materials is not particularly limited. For example, a negative electrode can be manufactured by adding a binder, a thickener, a conductive material, a solvent and the like to the negative electrode material to form a slurry, applying the slurry to the substrate of the current collector, and drying. Alternatively, the negative electrode material may be directly roll-formed into a sheet electrode,
A pellet electrode can also be formed by compression molding.

The binder used in the production of the electrode is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolytic solution used in the production of the electrode. Specific examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, isoprene rubber and butadiene rubber. As a thickener,
Examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch and casein.

Examples of the conductive material include metal materials such as copper and nickel, and carbon materials such as graphite and carbon black. As the material of the negative electrode current collector, a metal such as copper, nickel or stainless steel is used, and among these, a copper foil is preferable from the viewpoints of being easily processed into a thin film and cost. The material of the positive electrode that constitutes the secondary battery of the present invention,
Materials capable of inserting and extracting lithium such as lithium transition metal composite oxides such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide can be used.

The method for producing the positive electrode is not particularly limited, and it can be produced according to the above-mentioned method for producing the negative electrode. Regarding the shape, a binder, a conductive material, a solvent, etc. are added to the positive electrode material as needed and mixed, and then applied to the substrate of the current collector to form a sheet electrode, or press-molded to form a pellet electrode. Can be As the material of the positive electrode current collector, a metal such as aluminum, titanium, tantalum or an alloy thereof is used. Among these, aluminum or its alloy is particularly preferable in terms of energy density because it is lightweight.

The material and shape of the separator used in the secondary battery of the present invention are not particularly limited. However, it is preferable to select from materials that are stable to the electrolytic solution and have excellent liquid retention properties, and it is preferable to use a porous sheet or nonwoven fabric made of polyolefin such as polyethylene or polypropylene as a raw material. The method for producing the secondary battery of the present invention having at least the negative electrode, the positive electrode, and the non-aqueous electrolyte solution is not particularly limited, and can be appropriately selected from the methods usually adopted.

Further, the shape of the battery is not particularly limited, and is a cylinder type in which the sheet electrode and the separator are formed in a spiral shape, a cylinder type of an inside-out structure in which the pellet electrode and the separator are combined, and a coin type in which the pellet electrode and the separator are stacked. Etc. can be used.

[0038]

EXAMPLES Next, specific examples of the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless it exceeds the gist. Example 1 The d value of the lattice plane (002 plane) in X-ray diffraction was 0.33.
6 nm, crystallite size (Lc) is 100 nm or more (65
2 nm), ash content is 0.07% by weight, median diameter by laser diffraction / scattering method is 12 μm, specific surface area by BET method is 7.5 m ² / g, and Raman spectrum analysis using argon ion laser light is 1570-1620 cm ^−1.
P _A (peak intensity I _A ) and 1300-
The intensity ratio R = I _B / I _A of the peak P _B (peak intensity I _B ) in the range of 1400 cm ⁻¹ is 0.12, 1570 to 1620c.
A mixture in which 6 parts by weight of polyvinylidene fluoride was mixed with 94 parts by weight of natural graphite powder having a half-value width of a peak in the range of m ^-1 of 19.9 cm ^-1 and dispersed with N-methyl-2-pyrrolidone to form a slurry. Is evenly applied on a copper foil having a thickness of 18 μm, which is a negative electrode current collector, and dried, and then pressed by a pressing machine so that the negative electrode layer density is 1.5 g / cm ³ , and then the diameter is 12.5 mm. It was punched into a disk shape to obtain a negative electrode.

As a positive electrode active material, 85 parts by weight of LiCoO ₂ were mixed with 6 parts by weight of carbon black and 9 parts by weight of polyvinylidene fluoride (KF-1000, manufactured by Kureha Chemical Co., Ltd.) and mixed to prepare N-methyl-2-pyrrolidone. Was uniformly dispersed on a 20 μm thick aluminum foil, which is a positive electrode current collector, and dried to obtain a positive electrode layer density of 3.0 g / cm ^3. It was pressed and then punched out into a disk shape having a diameter of 12.5 mm to obtain a positive electrode.

As the electrolyte, LiPF ₆ sufficiently dried under a dry argon atmosphere was used as a solute, and 2 wt% of biphenyl and vinylene carbonate were added to a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio of 3: 7). Was added in an amount of 1% by weight, 1,3-propane sultone was added in an amount of 0.5% by weight, and LiPF ₆ was dissolved in an amount of 1 mol / liter.

Using these negative electrode, positive electrode and electrolytic solution,
The positive electrode was housed in a stainless steel can that also served as the positive electrode conductor, and the negative electrode was placed on the positive electrode via a separator impregnated with the electrolytic solution. The can body and the sealing plate which also serves as the negative electrode conductor were caulked and sealed with an insulating gasket interposed therebetween to produce a coin-type battery. Comparative Example 1 An electrolyte solution prepared by adding 2% by weight of biphenyl to a mixture of ethylene carbonate and ethyl methyl carbonate (3: 7 volume ratio) and further dissolving LiPF ₆ at a rate of 1 mol / liter was prepared. A coin-type battery was produced in the same manner as in Example 1 except that it was used.

Comparative Example 2 2% by weight of biphenyl was added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio), 1, 2.
3-propane sultone was added at a rate of 0.5% by weight,
Further, a coin type battery was produced in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving LiPF ₆ at a rate of 1 mol / liter was used.

Example 2 2% by weight of biphenyl, 1% by weight of vinylene carbonate, 0.5% by weight of 1,3-propane sultone, and fluoro of a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio). A coin type battery was produced in the same manner as in Example 1 except that an electrolyte solution prepared by adding benzene at a ratio of 2% by weight and dissolving LiPF ₆ at a ratio of 1 mol / liter was used.

Example 3 Of ethylene carbonate and ethyl methyl carbonate
2% by weight of biphenyl in the mixture (3: 7 volume ratio),
1 wt% len carbonate, 1,3-propanesalt
0.5% by weight and heptane at 2% by weight
And further LiPF ₆Is dissolved at a rate of 1 mol / liter
The same as Example 1 except that the electrolyte solution prepared by
Then, a coin-type battery was manufactured.

Example 4 Cyclohexylbenzene was added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio).
%, Vinylene carbonate 1% by weight, 1,3-propane sultone 0.5% by weight, and L
A coin-type battery was produced in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving iPF ₆ at a ratio of 1 mol / liter was used.

Comparative Example 3 Cyclohexylbenzene was added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio).
A coin type battery was produced in the same manner as in Example 1 except that an electrolyte solution prepared by dissolving LiPF _{6 in an amount} of 1% by weight and dissolving LiPF _{6 in an amount} of 1% by weight was used.

Example 5 Cyclohexylbenzene was added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio).
% By weight, 1% by weight vinylene carbonate, 0.5% by weight 1,3-propane sultone, 2% fluorobenzene.
A coin type battery was produced in the same manner as in Example 1 except that an electrolyte solution prepared by dissolving LiPF _{6 in an amount} of 1% by weight and dissolving LiPF _{6 in an amount} of 1% by weight was used.

Example 6 2% by weight of biphenyl, 1% by weight of vinylene carbonate and 0.5% of dimethyl sulfone were added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio).
A coin type battery was produced in the same manner as in Example 1 except that an electrolyte solution prepared by dissolving LiPF _{6 in an amount} of 1% by weight and dissolving LiPF _{6 in an amount} of 1% by weight was used.

Example 7 2% by weight of biphenyl, 1% by weight of vinylene carbonate and 0.5% by weight of methyl methanesulfonate were added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio). Then, a coin-type battery was produced in the same manner as in Example 1 except that an electrolytic solution prepared by dissolving LiPF ₆ at a rate of 1 mol / liter was used.

Example 8 2% by weight of biphenyl, 0.2% by weight of succinic anhydride and 0.5% by weight of 1,3-propanesultone were added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio). %, And LiPF ₆ was further dissolved at a rate of 1 mol / liter to prepare a coin-type battery in the same manner as in Example 1 except that an electrolytic solution prepared was used.

[Evaluation of Battery] Each of the above batteries was charged and discharged at a constant current of 0.5 mA at 25 ° C. for 5 cycles at a charge end voltage of 4.2 V and a discharge end voltage of 3 V to stabilize the battery. Stored at 85 ° C for 3 days. The battery after storage has a discharge end voltage of 3 at a constant current of 0.5 mA at 25 ° C.
The battery was discharged to V to measure the remaining capacity, and then charged and discharged with a constant current of 0.5 mA at a charge end voltage of 4.2 V and a discharge end voltage of 3 V to measure the capacity after storage. Next, after charging under the same conditions, the high load discharge characteristics were measured by discharging up to 3 V with a current value corresponding to 1.5 C (here, 1 C means 1
Represents the current value that can be fully charged in time, and 1.5C represents the current value 1.5 times that).

Table 1 shows the remaining capacity after storage, the capacity after storage and the capacity at high load discharge when the discharge capacity before storage was 100.

[0053]

[Table 1]

As is clear from Table 1 above, the battery of the present invention has a residual capacity after storage with respect to a discharge capacity before storage,
The subsequent capacity and high-load discharge characteristics are improved in a well-balanced manner, which is effective in improving storage characteristics at high temperatures.

[0055]

By using the non-aqueous electrolyte solution of the present invention,
While ensuring safety during overcharge, it is possible to manufacture batteries with high capacity and excellent storage characteristics, load characteristics, and cycle characteristics, which contributes to downsizing and higher performance of non-aqueous electrolyte secondary batteries. be able to.

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising a negative electrode capable of occluding and releasing at least lithium, a positive electrode, and an electrolytic solution obtained by dissolving a lithium salt in a non-aqueous solvent, A compound that reacts at a voltage higher than the maximum operating voltage of the battery when overcharged in a water solvent, at least one compound selected from the group consisting of cyclic carbonic acid esters and acid anhydrides having an unsaturated bond, and a sulfur-containing organic compound And a non-aqueous electrolyte secondary battery comprising: 2. At least one selected from the group consisting of a fluorine-containing aromatic compound having 9 or less carbon atoms, an aliphatic hydrocarbon, and a fluorine-containing aliphatic hydrocarbon compound in a non-aqueous solvent.
The non-aqueous electrolyte secondary battery according to claim 1, which contains one kind of compound. 3. A non-aqueous electrolyte solution for a non-aqueous electrolyte secondary battery comprising a negative electrode capable of inserting and extracting at least lithium and a positive electrode, wherein the non-aqueous electrolyte solution is at least a non-aqueous solvent. And a lithium salt, at least one selected from the group consisting of a compound that reacts in the nonaqueous solvent at a voltage higher than the maximum operating voltage of the battery when overcharged, a cyclic carbonic acid ester having an unsaturated bond, and an acid anhydride. A non-aqueous electrolyte for a secondary battery, which comprises a seed compound and a sulfur-containing organic compound.