JP2003331915A - Nonaqueous electrolyte secondary cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary cell with large capacity, excellent preservability, load property, and cycle property. <P>SOLUTION: For the nonaqueous electrolyte secondary cell composed of a negative electrode at least capable of storing/releasing lithium, a positive electrode, and electrolyte liquid containing lithium salt dissolved in nonaqueous solvent, the nonaqueous solvent contains at least one compound chosen from the group of cyclic carbonate including unsaturated bond and acid anhydride, organic compound including sulfur, and at least one compound chosen from aromatic compound of not more than nine carbons containing fluorine, aliphatic hydrocarbon, and aliphatic hydrocarbon containing fluorine. <P>COPYRIGHT: (C)2004,JPO

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 having a high capacity and excellent storage characteristics, load characteristics and cycle characteristics.

[0002]

2. Description of the Related Art With the recent lightening and miniaturization of electric products, development of lithium secondary batteries having a high energy density has been promoted. Further, with the expansion of application fields of lithium secondary batteries, improvement of battery characteristics is also demanded. Secondary batteries using metallic lithium as a negative electrode have been actively researched for a long time as batteries that can achieve high capacity. However, there is a problem that metallic lithium grows in a dendrite shape by repeating charging and discharging, and finally reaches the positive electrode to cause a short circuit inside the battery. This problem is the biggest technical problem when putting a metallic lithium secondary battery into practical use.

On the other hand, a negative electrode, for example, coke,
A non-aqueous electrolyte secondary battery using a carbonaceous material capable of inserting and extracting lithium such as artificial graphite and natural graphite has been proposed. In such a non-aqueous electrolyte secondary battery,
Since lithium does not exist in a metallic state, formation of dendrite is suppressed, and battery life and safety can be improved. In particular, non-aqueous electrolyte secondary batteries using graphite-based carbonaceous materials such as artificial graphite and natural graphite have been attracting attention as ones that meet the demand for higher capacity.

In a lithium secondary battery using the above carbonaceous material, a cyclic carbonate such as propylene carbonate or ethylene carbonate is usually widely used as a high dielectric constant solvent for a non-aqueous electrolyte. In a non-aqueous electrolyte secondary battery using a non-graphite carbonaceous material such as coke, a solvent containing propylene carbonate can be preferably used. On the other hand, in a non-aqueous electrolyte secondary battery in which a graphite-based carbonaceous material is used alone or as a negative electrode by mixing with another negative electrode material capable of absorbing and desorbing lithium, when a solvent containing propylene carbonate is used, the electrode is not charged during charging. The decomposition reaction of propylene carbonate progresses violently on the surface, and it becomes impossible to occlude and release lithium smoothly into the graphite-based carbonaceous negative electrode.

On the other hand, since ethylene carbonate is less likely to be decomposed like this, ethylene carbonate is often used as a high dielectric constant solvent in the electrolytic solution of a non-aqueous electrolytic solution secondary battery using a graphite-based carbonaceous negative electrode. However, even when ethylene carbonate is used as a main solvent, there are problems such as deterioration of charge / discharge efficiency, deterioration of cycle characteristics, and increase of battery internal pressure due to gas generation because the electrolytic solution is decomposed on the electrode surface during charge / discharge process.

Therefore, an electrolytic solution containing various additives has been proposed in order to improve the characteristics of the non-aqueous electrolytic solution secondary battery. An electrolytic solution containing vinylene carbonate and a derivative thereof (Japanese Patent Laid-Open No. 8-45545) and an electrolytic solution containing an acid anhydride in order to suppress decomposition of the electrolytic solution of a non-aqueous electrolytic battery using a graphite-based negative electrode Is proposed. In the electrolytic solution containing these compounds, these compounds are reductively decomposed on the surface of the negative electrode to form a film, and the film suppresses excessive decomposition of the electrolytic solution. However, although these compounds are effective in improving the cycle characteristics,
The storage characteristics in a high temperature environment above ℃ are not always satisfactory. Further, the vinylene carbonate compound easily reacts with the positive electrode material in a charged state, and the storage property tends to be further deteriorated when the added amount is increased.

Japanese Unexamined Patent Publication No. 2002-33121 proposes a secondary battery using a non-aqueous electrolytic solution containing a specific electrolyte. Among them, carbonic acid ester type additives such as vinylene carbonate and propane are proposed. An electrolytic solution containing a sulfur compound-based additive such as sultone, and an electrolytic solution containing these at the same time are disclosed, and when they are contained at the same time, the capacity deterioration after storage and the gas generation amount are suppressed, and to a certain extent. The effect was seen, but the load characteristics after storage were not sufficient.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and provides a non-aqueous liquid electrolyte secondary battery having a high capacity and excellent balance in storage characteristics, load characteristics and cycle characteristics. The challenge is to provide.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned objects, and as a result, by using an electrolytic solution of a specific composition, the storage characteristics, load characteristics and cycle characteristics can be increased with high capacity. The present invention has been completed by finding that the above can be improved in a well-balanced manner.

That is, the gist of the present invention is a non-aqueous electrolyte solution comprising at least a negative electrode capable of occluding and releasing lithium, a positive electrode, and an electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent. In the following battery, in the non-aqueous solvent, at least one compound selected from the group consisting of a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride, a sulfur-containing organic compound, and a fluorine-containing aromatic compound having 9 or less carbon atoms. And a non-aqueous electrolyte secondary battery containing at least one compound selected from the group consisting of a compound, an aliphatic hydrocarbon and a fluorine-containing aliphatic hydrocarbon 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, in the non-aqueous solvent, at least one compound selected from the group consisting of cyclic carbonic acid esters and acid anhydrides having an unsaturated bond, and sulfur-containing Organic compound and carbon number 9
A non-aqueous electrolyte solution for a secondary battery, which contains at least one compound selected from the group consisting of the following fluorine-containing aromatic compounds, aliphatic hydrocarbons and fluorine-containing aliphatic hydrocarbon compounds: Exist.

The reason why the battery characteristics are improved by using the above electrolytic solution is not fully clear. Conventionally, a cyclic carbonic acid ester or acid anhydride having an unsaturated bond improves cycle characteristics by reacting on the negative electrode surface, but especially at high temperatures, a side reaction occurs on the positive electrode surface, resulting in a balance. Good battery characteristics were not obtained.

In the present invention, at least one compound selected from the group consisting of a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride, a sulfur-containing organic compound, a fluorine-containing aromatic compound having 9 or less carbon atoms, An electrolytic solution containing at least one compound selected from the group consisting of an aliphatic hydrocarbon and a fluorine-containing aliphatic hydrocarbon compound is used, whereby a cyclic carbonic acid ester or acid anhydride having an unsaturated bond is obtained. , A composite film of reduction reaction products derived from them is formed efficiently on the surface of the negative electrode from the time of initial charging, the composite film is stable even in a high temperature environment, and the negative electrode of the sulfur-containing compound and other electrolytic solution components The sulfur-containing organic compound suppresses the side reaction above, suppresses the reactivity of the positive electrode by adsorbing or reacting on the active site of the positive electrode, and has a cyclic carbonic acid having an unsaturated bond. Suppresses side reactions of stellates or acid anhydrides and other electrolytic solution components on the positive electrode, and the fluorine-containing aromatic compound, aliphatic hydrocarbon or fluorine-containing aliphatic hydrocarbon compound having a carbon number of 9 or less is oxidized. Since these compounds are stable against reduction and reduction, these compounds exist at the active sites on the surface of the positive electrode and the negative electrode, which were insufficiently suppressed by the cyclic carbonic acid ester or acid anhydride having an unsaturated bond and the sulfur-containing organic compound alone. This suppresses side reactions of cyclic carbonic acid esters or acid anhydrides having unsaturated bonds, sulfur-containing organic compounds, and other electrolytic solution components, and suppresses side reactions that occur inside the battery during high temperature storage as a whole. It is considered that the large current discharge characteristics can be improved.

[0014]

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,
In the non-aqueous solvent, at least one compound selected from the group consisting of a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride, a sulfur-containing organic compound, a fluorine-containing aromatic compound having 9 or less carbon atoms, an aliphatic At least one selected from the group consisting of hydrocarbons and fluorine-containing aliphatic hydrocarbon compounds
A compound of a species.

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 ester carbonate having an unsaturated bond is not particularly limited, and examples thereof include vinylene carbonate, methylvinylene carbonate, ethylvinylene carbonate, 4,5-dimethylvinylene carbonate,
Vinylene carbonate compounds such as 4,5-diethylvinylene carbonate, fluorovinylene carbonate, trifluoromethylvinylene carbonate, 4-vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, 4-ethyl-4-vinylethylene carbonate, 4 -N-propyl-4-vinylethylene carbonate, 5-methyl-4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-
Divinyl ethylene carbonate, 4,4-dimethyl-5
-Methylene ethylene carbonate, 4,4-diethyl-
5-methylene ethylene 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. It is 5% by weight. In particular, in the case of cyclic carbonic acid ester having an unsaturated bond, it is 0.1 to 4
%, And in the case of 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, among them, ethylene sulfite, sulfolane, 1,3
-Propane sultone, dimethyl sulfone, methyl methanesulfonate are preferred. 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. The non-aqueous solvent used in the present invention contains 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.

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 products of the above-mentioned 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. You may use these compounds in mixture of 2 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. The non-aqueous solvent used in the present invention is not particularly limited, for example, ethylene carbonate, propylene carbonate, cyclic carbonate such as butylene carbonate, dimethyl carbonate,
Dialkyl carbonates such as diethyl carbonate, di-n-propyl carbonate, ethylmethyl carbonate (preferably having an alkyl group having 1 to 4 carbon atoms), tetrahydrofuran, cyclic ethers such as 2-methyltetrahydrofuran, dimethoxyethane, dimethoxymethane, etc. Chain ethers, γ-butyrolactone, cyclic esters such as γ-valerolactone, methyl acetate, methyl propionate, chain esters such as ethyl propionate, trimethyl phosphate, phosphorus-containing organic solvents such as triethyl phosphate, and the like. To be 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 a mixed solvent occupying 70% by volume or more of the whole, and thus the electric conductivity of the electrolytic solution is high, and the cycle characteristics and the large current discharge characteristics are high, which is preferable.

Specific examples of the alkylene carbonate having 2 to 4 carbon atoms in the alkylene group include ethylene carbonate, propylene carbonate and butylene carbonate. Of these, ethylene carbonate and propylene carbonate are preferred. Specific examples of the dialkyl carbonate having 1 to 4 carbon atoms in the alkyl group include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethylmethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate. Etc. can be mentioned. 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, 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, γ-valerolactone, and the like. Those containing ethylene carbonate are particularly preferable, and among them, 5 volumes of ethylene carbonate are preferable. % Or more and 55 volume% or more of γ-butyrolactone, or a mixed solvent containing 30 volume% or more of ethylene carbonate and 30 volume% or more of propylene carbonate is less likely to generate gas during high temperature storage, and has cycle characteristics and large current. A good balance of discharge characteristics and the like is more preferable.

The non-aqueous electrolyte solution of the present invention may be mixed with other useful compounds such as conventionally known additives, dehydrating agents, deoxidizing agents and overcharge preventing 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,
When 0.1 to 5% by weight of a nitrogen-containing compound such as 3-dimethyl-2-imidazolidinone and N-methylsuccinimide is contained, the capacity-maintaining property and the cycle characteristic are improved as compared with the case where it is not contained. Is better.

As the overcharge preventing agent, biphenyl, alkylbiphenyl, terphenyl, a partially hydrogenated form of terphenyl, cyclohexylbenzene, diphenyl ether, benzofuran, dibenzofuran, and their halides such as 2-fluorobiphenyl, mainly fluorine. And fluorine-containing anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole and 2,6-difluoroanisole.
If it contains 1 to 5% by weight, the battery may burst when overcharged.
Ignition can be suppressed.

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_FourInorganic such as
Lithium salt, LiCF₃SO₃, LiN (CF₃S
O₂)₂, LiN (C₂F_FiveSO₂)₂, LiN (CF₃SO
₂) (C_FourF₉SO₂), LiC (CF₃SO₂)₃, LiP
F_Four(CF₃)₂, LiPF_Four(C₂F_Five)₂, LiPF_Four(C
F₃SO₂)₂, LiPF_Four(C₂F _FiveSO₂)₂, LiBF₂
(CF₃)₂, LiBF₂(C₂F_Five)₂, LiBF₂(CF₃
SO₂)₂, LiBF₂(C₂F_FiveSO₂)₂With fluorine
Organic lithium salts are mentioned. Among these, solubility and i
In terms of dissociation degree and electric conductivity characteristics, LiPF₆, Li
BF_Four, LiCF₃SO₃, LiN (CF₃SO₂)₂, Li
N (C₂F_FiveSO₂)₂Is preferred, and LiPF₆, LiBF_Four
Is more preferable. These solutes are a mixture of two or more.
You may use it.

Further, an inorganic lithium salt selected from LiPF ₆ or LiBF ₄ , LiCF ₃ SO ₃ and LiN (CF ₃
By using two or more lithium salts in combination with a fluorine-containing organic lithium salt selected from SO ₂ ) ₂ or LiN (C ₂ F ₅ SO ₂ ) ₂ , deterioration after storage at high temperature tends to be suppressed, 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 thermal decomposition products of organic substances under various thermal decomposition 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 as determined 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 manufacturing method of the positive electrode is not particularly limited, and the positive electrode can be manufactured according to the above-described manufacturing method of the negative electrode. Regarding the shape, after adding a binder, a conductive material, a solvent and the like to the positive electrode material as needed, and mixing them, the current collector substrate is coated with a sheet electrode, or press-molded to form a pellet. It can be an electrode.

As the material of the positive electrode current collector, a metal such as aluminum, titanium, tantalum or the 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 stable to the electrolyte,
It is preferable to select from materials having excellent liquid retention, 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 employed. Further, the shape of the secondary 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 in which the pellet electrode and the separator are combined with each other, and a coin type in which the pellet electrode and the separator are stacked. Can be used.

[0040]

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 was added 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 electrolytic solution, LiPF ₆ sufficiently dried in a dry argon atmosphere was used as a solute, and 1% by weight of vinylene carbonate was added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio).
0.5% by weight of 1,3-propane sultone and 2% by weight of fluorobenzene were added, and 1% of LiPF ₆ was added.
It was prepared by dissolving at a ratio of 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 To a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio), 1% by weight of vinylene carbonate and 0.5% by weight of 1,3-propane sultone were added, and 1% by weight of LiPF ₆ was added. A coin-type battery was produced in the same manner as in Example 1 except that the electrolytic solution prepared by dissolving at a mol / liter ratio was used.

Example 2 1% by weight of vinylene carbonate, 0.5% by weight of 1,3-propanesultone and 2% by weight of heptane in 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 1 mol / liter was used.

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

Example 4 1% by weight of vinylene carbonate, 0.5% by weight of sulfolane and 2% by weight of fluorobenzene were added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio), 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 5 0.2% by weight of succinic anhydride, 0.5% by weight of 1,3-propane sultone and 2 parts of fluorobenzene were added to a mixture of ethylene carbonate and ethylmethyl carbonate (3: 7 volume ratio). % By weight, and LiPF ₆
A coin-type battery was manufactured in the same manner as in Example 1 except that the electrolytic solution prepared by dissolving 1 was dissolved at a rate of 1 mol / liter was used.

Example 6 1% by weight of vinylene carbonate was added to a mixture of ethylene carbonate and γ-butyrolactone (3: 7 volume ratio).
0.5% by weight of vinyl ethylene carbonate, 1,3-
Example 1 except that an electrolytic solution prepared by adding 0.5% by weight of propane sultone and 2% by weight of fluorobenzene and further dissolving LiBF ₄ at a rate of 1.5 mol / liter was used. A coin-type battery was manufactured in the same manner as in.

Comparative Example 2 1% by weight of vinylene carbonate was added to a mixture (3: 7 volume ratio) of ethylene carbonate and γ-butyrolactone,
0.5% by weight of vinyl ethylene carbonate, 1,3-
Coin-type battery in the same manner as in Example 1 except that an electrolyte solution prepared by adding propane sultone at a rate of 0.5% by weight and further dissolving LiBF ₄ at a rate of 1.5 mol / liter was used. Was produced.

[Evaluation of Battery] Each of the above batteries was charged and discharged at 25 ° C. 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 for 5 cycles to stabilize, and then, in a charged state. 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 characteristic was measured by discharging up to 3V with a current value corresponding to 2C (here, 1C represents a current value that can be fully charged in 1 hour, and 2C is the value thereof). Represents twice the current value).

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.

[0052]

[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.

[0054]

By using the non-aqueous electrolyte solution of the present invention,
A battery having a high capacity and excellent storage characteristics, load characteristics, and cycle characteristics can be manufactured, which can contribute to miniaturization and high performance of a non-aqueous electrolyte secondary battery.

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Claims (2)

[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, At least one compound selected from the group consisting of a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride in a water solvent, a sulfur-containing organic compound, and a carbon number of 9
A non-aqueous electrolyte secondary battery comprising the following fluorine-containing aromatic compound, an aliphatic hydrocarbon, and at least one compound selected from the group consisting of fluorine-containing aliphatic hydrocarbon compounds. 2. 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, and in the non-aqueous solvent, at least one compound selected from the group consisting of a cyclic carbonic acid ester having an unsaturated bond and an acid anhydride,
2. A sulfur-containing organic compound and at least one compound 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. Non-aqueous electrolyte for secondary batteries.