JP2002373702A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery using it, capable of maintaining the battery's good cycle characteristic and enhancing low-temperature characteristics. SOLUTION: For the nonaqueous electrolyte obtained by dissolving an electrolyte salt into a organic solvent, the solvent contains as essential components a cyclic carbonate compound represented by the chemical formula (1) and at least one kind of chain ester compound represented by the general formula (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the electrolyte.
As a solvent constituting the non-aqueous electrolytic solution, a specific cyclic carbonate compound having a fluorine atom in a molecule, and a non-aqueous electrolytic solution using a solvent containing a chain ester compound having a specific structure and the electrolytic solution were used. The present invention relates to a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years,
Non-aqueous electrolyte secondary batteries that use a lithium metal or lithium alloy or a substance capable of occluding and releasing lithium ions as a negative electrode active material have attracted attention because of their features such as high energy density and low self-discharge. ing.

However, in the above nonaqueous electrolyte secondary battery, a reaction with the negative electrode using lithium as an active material occurs on the negative electrode side, and the positive electrode is maintained at a high potential. Has a disadvantage that it is easily decomposed and has poor storage stability.

[0004] For this reason, developing a non-aqueous electrolyte having excellent storage characteristics or cycle characteristics has been the most important issue in putting a non-aqueous electrolyte secondary battery into practical use.

The above non-aqueous electrolyte is obtained by dissolving an electrolyte which is a solute in an organic solvent. The characteristics required for this solvent include a large dielectric constant, a large amount of the electrolyte which is a solute, and a low viscosity. Excellent in low-temperature characteristics, stable against oxidation and reduction, not decomposed, low in volatility, and high in safety in use.

Conventionally, low-boiling solvents such as 1,2-dimethoxyethane and 1,3-dioxolane have been used as solvents for use in non-aqueous electrolyte secondary batteries, but these low-boiling solvents have a dielectric constant. Not only is it small, but when used alone, the negative electrode material, lithium, reacts as a solvent and elutes into the electrolyte, resulting in poor storage characteristics. However, there is a drawback that the internal resistance of the battery increases and the high-rate discharge characteristics deteriorate.

For this reason, a mixed solvent of a cyclic carbonate having a large dielectric constant, such as ethylene carbonate or propylene carbonate, and a low boiling point solvent, such as 1,2-dimethoxyethane or tetrahydrofuran, has been used. The purpose of this type of solvent is to reduce the viscosity of the electrolytic solution by using a solvent having a low boiling point while forming a lithium carbonate film having excellent ionic conductivity on the negative electrode surface by reacting the cyclic carbonate with lithium. This is intended to prevent the ionic conductivity of the electrolytic solution from lowering and to improve the high-rate discharge characteristics.

However, low-boiling solvents such as 1,2-dimethoxyethane and tetrahydrofuran are easily decomposed at the contact interface with a high-potential positive electrode because of their low oxidation-reduction potential. Since the lithium carbonate film formed on the surface is gradually decomposed and changed to an insulating lithium oxide film, the initial high-rate discharge characteristics can be improved to some extent, but the high-rate discharge characteristics after storage are sufficient. It was not satisfactory.

For this reason, there is a strong demand for improvements regarding the electrolyte solvent, for example, Japanese Patent Application Laid-Open Nos. 2-172162, 2-172163, 4-171.
No. 674, Japanese Unexamined Patent Publication No. 5-13088 and the like propose use of a mixed solvent of a cyclic carbonate compound such as ethylene carbonate and propylene carbonate and a chain carbonate compound such as dimethyl carbonate, diethyl carbonate and dipropyl carbonate. ing.

Although the use of a chain carbonate compound in place of 1,2-dimethoxyethane, tetrahydrofuran or the like can improve the high-rate discharge characteristics at initial and after storage to some extent, these chain carbonate compounds are not solutes. However, the disadvantage that the electrolyte is difficult to dissolve and that it is easily volatilized because it is a low molecular compound could not be solved.

Japanese Patent Application Laid-Open Nos. 8-306364 and 9-528 disclose proposals in which a compound obtained by introducing a fluorine atom into a cyclic carbonate compound is contained in an electrolytic solution.
No. 92, JP-A-9-63644 and the like. The fluorine-containing cyclic carbonate according to these proposals can lower the viscosity and improve the stability of the electrolyte solution as compared with the cyclic carbonate having a structure in which fluorine is not introduced. However, the structure of the fluorine-containing cyclic carbonate is a structure in which fluorine is introduced into a methyl group of propylene carbonate, or a structure in which a fluorine atom and a lower alkyl group are introduced into ethylene carbonate, each having a chain-like substituent. Therefore, it was not possible to obtain sufficient performance in the stability of the electrolytic solution as compared with a compound having only a cyclic structure. Therefore, it has been strongly desired to find a solvent that is stable to oxidation-reduction reaction, hardly decomposes, has low viscosity, is excellent in electrolyte solubility, and has low volatility.

Therefore, a proposal has been made, for example, in Japanese Patent Application Laid-Open No. 11-260402, in which a compound obtained by introducing a fluorine atom into a cyclic carbonate compound having no chain-like substituent is contained in an electrolytic solution. The fluorine-containing cyclic ester according to this proposal was excellent in high-rate discharge characteristics at the initial stage and after storage, and also excellent in cycle characteristics when used as a secondary battery. However, the low-temperature characteristics were not sufficiently satisfactory.

Accordingly, an object of the present invention is to provide a non-aqueous electrolyte capable of improving low-temperature characteristics while maintaining good cycle characteristics of the battery, and a non-aqueous electrolyte secondary battery using the electrolyte. Is to do.

[0014]

The present inventors have made various studies in view of the present situation, and as a result, as a solvent in a non-aqueous electrolyte, a specific cyclic carbonate compound having a fluorine atom in a molecule and a specific cyclic carbonate compound having a fluorine atom in a molecule. It has been found that a non-aqueous electrolyte using a solvent containing a chain ester compound having a structure can achieve the above object.

The present invention has been made based on the above findings. In an electrolytic solution in which an electrolyte salt is dissolved in an organic solvent, a cyclic carbonate compound represented by the following chemical formula (1) is used as the solvent. The present invention provides a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the electrolyte, wherein the non-aqueous electrolyte contains at least one of the chain ester compounds represented by the formula (1) as an essential component.

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[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The non-aqueous electrolyte of the present invention and a non-aqueous electrolyte secondary battery using the electrolyte will be described in detail below.
However, the present invention is not limited by the following examples.

The non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte comprising a solute and a solvent. And the solvent of the non-aqueous electrolyte is
A non-aqueous solvent represented by the chemical formula (1) (5,5-difluoro-1,3-dioxacyclohexane-2-one) and the linear ester compound represented by the general formula (2) It contains.

A cyclic carbonate compound represented by the above chemical formula (1) (hereinafter sometimes referred to as FPC)
Reacts, for example, 2,2-difluoro-1,3-propylene glycol with an alkyl chloroformate in the presence of an acid acceptor such as an organic amine compound. Furthermore, it can be easily produced by cyclization in the presence of a basic catalyst, but the production method is not limited at all.

In the above general formula (2), R ₁ or R ₂
Examples of the alkyl group having 1 to 8 carbon atoms represented by include methyl, trifluoromethyl, ethyl, trifluoroethyl, propyl, pentafluoropropyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl and the like. . Examples of the chain ester compound represented by the general formula (2) include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl-n-butyl carbonate, and methyl-t-butyl. -Carbonate, di-
Examples include i-propyl carbonate, t-butyl-i-propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, sec-butyl acetate, butyl acetate, methyl propionate, and ethyl propionate. At least one of the above-mentioned chain ester compounds is used as an essential component, and if necessary, two or more kinds are used in combination. Among the above, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DE
C), ethyl-n-butyl carbonate, methyl-t-
Chain carbonate compounds such as butyl-carbonate, di-i-propyl carbonate, and t-butyl-i-propyl carbonate have excellent cycle stability when blended in the electrolytic solution and are preferably used.

The non-aqueous electrolyte of the present invention has the above chemical formula (1)
Although only two kinds of the cyclic carbonate compound represented by the general formula (2) and the chain ester compound represented by the above general formula (2) can be used as a solvent, if necessary, a 5-membered cyclic carbonate compound is contained. Can be. Examples of the 5-membered cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, butylene carbonate (BC), and 4-methyl-1,3-dioxolan.

Further, other non-aqueous solvents can be used for the purpose of reducing the viscosity and the like. Other non-aqueous solvents that can be used in the non-aqueous electrolyte of the present invention are not particularly limited. For example, γ-butyrolactone (GBL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2MeTHF), 1,3- Dioxane (DO
L), diethyl ether, 1,2-dimethoxyethane,
Ethoxymethoxyethane, dimethyl ether, 1,2-
Bis (methoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) propane, diethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, dimethylsulfoxide, dimethylformamide , Sulfolane, tetramethylsulfolane, dimethyl sulfone, dimethyl sulfoxide, 3-
Examples thereof include those used as conventional solvents for nonaqueous electrolytes such as sulfolene, toluene, N-methylpyrrolidone, dimethylformamide, and N, N-dimethylacetamide.

The content of the cyclic carbonate compound represented by the above formula (1) according to the present invention is preferably 0.1 to 80 parts by mass, more preferably 1 to 50 parts by mass, based on 100 parts by mass of the total solvent. Parts by weight. If the amount is less than 0.1 part by mass, the dielectric constant of the electrolytic solution is reduced, and if the amount exceeds 80 parts by mass, there is a problem in low-temperature performance, which is not preferable. Further, the content of the chain ester compound represented by the general formula (2) is preferably 1 to 95 parts by mass, more preferably 30 to 90 parts by mass, based on 100 parts by mass of the total solvent.
Parts by weight. If the amount is less than 1 part by mass, it is not sufficient to improve the performance at a low temperature, and if it exceeds 95 parts by mass, a sufficient dielectric constant cannot be obtained, which is not preferable. Further, the content of the 5-membered cyclic carbonate compound to be blended as required is preferably 0 to 40 with respect to 100 parts by mass of the total solvent.
Parts by mass, and the content of the other solvents is 100
It is preferably 0 to 30 parts by mass with respect to parts by mass.

The non-aqueous electrolyte solution of the present invention may optionally contain a halogen-based, phosphorus-based or other flame retardant as a flame retardant in order to impart flame retardancy. Examples of the phosphorus-based flame retardant include phosphoric esters such as trimethyl phosphate and triethyl phosphate.

The amount of the phosphorus-based flame retardant to be used is preferably 5 to 100 parts by mass, particularly preferably 10 to 50 parts by mass, based on 100 parts by mass of the total solvent constituting the electrolytic solution. If the amount is less than 5 parts by mass, a sufficient flame retarding effect cannot be obtained.

As the electrolyte in the non-aqueous electrolyte, a conventionally known electrolyte is used.
₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , L
iN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ ,
LiSbF ₆ , LiSiF ₅ , LiAlF ₄ , LiSC
N, LiClO ₄ , LiCl, LiF, LiBr, Li
I, LiAlF ₄ , LiAlCl ₄ , NaClO ₄ , N
aBF ₄ , NaI and the like.
Inorganic salts such as PF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , and CF ₃ SO ₃ Li, N (CF ₃ S
A combination of one or more salts selected from the group consisting of organic salts such as O ₃ ) ₂ Li and C (CF ₃ SO ₂ ) ₃ Li is preferable because of its excellent electrical properties.

The above electrolyte has a concentration in the electrolyte of 0.1%.
It is preferable to dissolve in the above-mentioned organic solvent so as to be 3.0 to 3.0 mol / l, particularly 0.5 to 2.0 mol / l. If the concentration of the electrolyte is less than 0.1 mol / l, a sufficient current density may not be obtained. If the concentration is more than 3.0 mol / l, the stability of the electrolyte may be impaired.

The positive electrode, the negative electrode and the separator in the non-aqueous electrolyte secondary battery of the present invention are not particularly limited, but various materials conventionally used for non-aqueous electrolyte secondary batteries can be used. Can be used as is.

The electrode material includes a positive electrode and a negative electrode.
For the positive electrode, a positive electrode active material, a binder, and a conductive material are slurry.
And apply it to the current collector and dry it to form a sheet.
Is used. As the positive electrode active material, TiS_Two,
TiS_Three, MoS_Three, FeS _Two, Li_(1-x)MnO_Two,
Li_(1-x)Mn_TwoO_Four, Li_(1-x)CoO_Two, Li_(1
-x)NiO_Two, LiV_TwoO_Three, V_TwoO_FiveEtc.
You. Note that x in the example of the positive electrode active material is a number of 0 to 1.
Is shown. Of these positive electrode active materials, lithium and transition metals
Are preferred, and LiCoO_Two, LiNi
O_Two, LiMn_TwoO_Four, LiMnO_Two, LiV_TwoO_Threeetc
Is preferred. Examples of binders for negative and positive electrode active materials
For example, polyvinylidene fluoride, polytetrafluoroethylene
Len, EPDM, SBR, NBR, fluoro rubber, etc.
But not limited to these.

As the negative electrode, one obtained by slurrying a negative electrode active material and a binder with a solvent is applied to a current collector and dried to form a sheet. Examples of the negative electrode active material include inorganic compounds such as lithium, lithium alloys and tin compounds, carbonaceous materials, and conductive polymers. In particular, a carbonaceous material that can store and release highly safe lithium ions is preferable. This carbonaceous material is not particularly limited, but graphite and petroleum-based coke, coal-based coke, petroleum-based pitch carbide, coal-based pitch carbide, phenolic resin, carbonized resin such as crystalline cellulose, and partially carbonized these Examples include carbon materials, furnace black, acetylene black, pitch-based carbon fibers, and PAN-based carbon fibers.

Examples of the conductive material for the positive electrode include graphite fine particles, carbon black such as acetylene black, and amorphous carbon fine particles such as needle coke, but are not limited thereto. As a solvent for forming a slurry, an organic solvent that dissolves a binder is usually used. For example, N-
Methylpyrrolidone, dimethylformamide, dimethylacetamide, methylethylketone, cyclohexanone,
Methyl acetate, methyl acrylate, diethyltriamine,
NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like,
It is not limited to this. In some cases, the active material is slurried with latex such as SBR by adding a dispersant, a thickener, and the like to water.

The current collector of the negative electrode usually contains copper, nickel,
Stainless steel, nickel-plated steel, or the like is used, and aluminum, stainless steel, nickel-plated steel, or the like is usually used for the positive electrode current collector.

In the non-aqueous electrolyte secondary battery of the present invention, a separator is used between the positive electrode and the negative electrode, but a commonly used polymer microporous film can be used without any particular limitation. For example,
Polyethers such as polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyether sulfone, polycarbonate, polyamide, polyimide, polyethylene oxide and polypropylene oxide, carboxymethyl cellulose and hydroxy Examples thereof include films composed of various celluloses such as propylcellulose, polymer compounds mainly composed of poly (meth) acrylic acid and various esters thereof, derivatives thereof, and copolymers and mixtures thereof. Further, such a film may be used alone, or a multilayer film in which these films are laminated. Further, various additives may be used for these films, and the types and contents thereof are not particularly limited.
Among these microporous films, polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone are preferably used for the nonaqueous electrolyte secondary battery of the present invention.

[0033] These separator films are made microporous so that the electrolyte solution permeates and ions easily permeate. The microporous method includes a phase separation method in which a film of a polymer compound and a solvent is formed while microphase-separating the solution, and the solvent is extracted and removed to form a porous layer. The film is extruded and heat-treated, and the crystals are arranged in one direction, and a `` stretching method '' or the like is used to form a gap between the crystals by stretching to make the film porous, which is appropriately selected depending on the polymer film used. You. In particular, a phase separation method is preferably used for polyethylene and polyvinylidene fluoride preferably used in the present invention.

The non-aqueous electrolyte, electrode material and separator of the present invention contain a phenolic antioxidant, a phosphorus antioxidant, a thioether antioxidant and a hindered amine light stabilizer for the purpose of further improving safety. It may be added.

Examples of the phenolic antioxidants include 1,6-hexamethylenebis [(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionamide] and 4,4'-thiobis ( 6-tert-butyl-m-
Cresol), 4,4′-butylidenebis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,3 5-tris (2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate,
1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl)
-2,4,6-trimethylbenzene, tetrakis [3-
(Methyl (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane, thiodiethylene glycol bis [(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,6-hexamethylenebis [(3,5-di-tert-butyl-4-hydroxyphenyl)
Propionate], bis [3,3-bis (4-hydroxy-3-tert-butylphenyl) butyric acid] glycol ester, bis [2-tert-butyl-4-methyl-6- (2-hydroxy-3- Tert-butyl-5-methylbenzyl) phenyl] terephthalate, 1,3,5-tris [(3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxyethyl] isocyanurate,
3,9-bis [1,1-dimethyl-2-{(3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy} ethyl] -2,4,8,10-tetraoxaspiro [5 , 5] undecane, triethylene glycol bis [(3-tert-butyl-4-hydroxy-5-methylphenyl) propionate] and the like, preferably 0.01 to 10 parts by mass based on 100 parts by mass of the electrode material. Parts, more preferably 0.05 to 5 parts by weight.

Examples of the phosphorus antioxidants include, for example,
Tris nonylphenyl phosphite, tris [2-tert-butyl-4- (3-tert-butyl-4-hydroxy-5-
Methylphenylthio) -5-methylphenyl] phosphite, tridecyl phosphite, octyl diphenyl phosphite, di (decyl) monophenyl phosphite,
Di (tridecyl) pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, bis (2,4-ditertbutylphenyl) pentaerythritol diphosphite, bis (2,6-ditertbutyl) 4-methylphenyl) pentaerythritol diphosphite, bis (2,4,6-tritert-butylphenyl) pentaerythritol diphosphite, bis (2,4-dicumylphenyl) pentaerythritol diphosphite, tetra (tridecyl) ) Isopropylidene diphenol diphosphite, tetra (tridecyl)-
4,4'-n-butylidenebis (2-tert-butyl-5-
Methylphenol) diphosphite, hexa (tridecyl) -1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butanetriphosphite, tetrakis (2,4-di-tert-butylphenyl) biphenyl Range phosphonite, 9,10-dihydro-9-
Oxa-10-phosphaphenanthrene-10-oxide, 2,2′-methylenebis (4,6-tert-butylphenyl) -2-ethylhexyl phosphite, 2,2 ′
-Methylenebis (4,6-tert-butylphenyl) -octadecylphosphite, 2,2′-ethylidenebis (4,6-ditert-butylphenyl) fluorophosphite, tris (2-[(2,4,8 , 10-Tetrakis tert-butyldibenzo [d, f] [1,3,2] dioxaphosphepin-6-yl) oxy] ethyl) amine, 2-
Ethyl-2-butylpropylene glycol and 2,4,6
Phosphites of tri-tert-butylphenol and the like.

The thioether-based antioxidants include:
Examples include dialkylthiodipropionates such as dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiodipropionate, and pentaerythritol tetra (β-alkylmercaptopropionate).

Examples of the hindered amine light stabilizer include 2,2,6,6-tetramethyl-4-piperidyl stearate, 1,2,2,6,6-pentamethyl-4-piperidyl stearate, , 2,6,6-tetramethyl-4-piperidylbenzoate, bis (2,
2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1-octoxy-2,
2,6,6-tetramethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-)
Piperidyl) -1,2,3,4-butanetetracarboxylate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, bis ( 2,2,6,6-tetramethyl-4-piperidyl) di (tridecyl) -1,2,2
3,4-butanetetracarboxylate, bis (1,
2,2,6,6-pentamethyl-4-piperidyl) di (tridecyl) -1,2,3,4-butanetetracarboxylate, bis (1,2,2,4,4-pentamethyl-4-piperidyl) ) -2-Butyl-2- (3,5-ditert-butyl-4-hydroxybenzyl) malonate, 1-
(2-hydroxyethyl) -2,2,6,6-tetramethyl-4-piperidinol / diethyl succinate polycondensate, 1,6-bis (2,2,6,6-tetramethyl-4
-Piperidylamino) hexane / 2,4-dichloro-6
Morpholino-s-triazine polycondensate, 1,6-bis (2,2,6,6-tetramethyl-4-piperidylamino) hexane / 2,4-dichloro-6-tert-octylamino-s-triazine Polycondensate, 1,5,8,12-tetrakis [2,4-bis (N-butyl-N- (2,2,
6,6-tetramethyl-4-piperidyl) amino) -s
-Triazin-6-yl] -1,5,8,12-tetraazadodecane, 1,5,8,12-tetrakis [2,4
-Bis (N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino) -s-triazin-6-yl] -1,5,8-12-tetraazadodecane, 1,6,11-tris [2,4-bis (N-butyl-N- (2,2,6,6-tetramethyl-4-piperidyl) amino) -s-triazin-6-yl] aminoundecane, 1,6,11-tris [2,4-bis (N-butyl-N- (1,2,2,6,6-pentamethyl-4-
Hindered amine compounds such as piperidyl) amino) -s-triazin-6-yl] aminoundecane.

The non-aqueous electrolyte secondary battery of the present invention having the above-mentioned structure is not particularly limited in its shape, and can be used as batteries of various shapes such as a flat type (button type), a cylindrical type and a square type. it can. Examples of the nonaqueous electrolyte secondary battery of the present invention include a lithium secondary battery composed of lithium and the like,
The present invention is not limited to this, and a configuration in which the configuration is appropriately changed without impairing the effects of the present invention can also be adopted.

FIG. 1 is a perspective view showing a cross section of an internal structure of a lithium secondary battery (cylindrical battery) as a non-aqueous electrolyte secondary battery of the present invention, and FIG. 2 is a schematic diagram showing a basic configuration thereof. FIG. 1 and 2, reference numeral 1 denotes a negative electrode, 1 ′
Is a negative electrode plate, 1 "is a negative electrode lead, 2 is a negative electrode current collector, 3 is a positive electrode, 3 'is a positive electrode plate, 3" is a positive electrode lead, 4 is a positive electrode current collector, 5 is an electrolytic solution, 6 is a separator, 7 Is the positive terminal, 8
Is a negative electrode terminal, 10 is a non-aqueous electrolyte secondary battery, 11 is a case, 12 is an insulating plate, 13 is a gasket, 14 is a safety valve,
Reference numeral 15 denotes a PTC element.

As shown in FIG. 2, the lithium secondary battery as the non-aqueous electrolyte secondary battery 10 has a negative electrode 1, a negative electrode current collector 2, and a positive electrode terminal at least composed of lithium or a lithium alloy as an active material. 7 and a negative electrode terminal 8. The non-aqueous electrolyte secondary battery can use, as necessary, constituent materials other than those described above which are usually used for a non-aqueous electrolyte secondary battery.

[0042]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited at all by the following examples. In addition, the compounding numerical values of the solvents shown in Tables 1 to 3 are all based on parts by mass.

[Reference Examples 1-1 and 1-2 and Reference Comparative Example 1]
-1 to 1-4] The freezing points, viscosities and dielectric constants of the solvents obtained with the formulations shown in Table 1 below were measured as Reference Examples and Reference Comparative Examples. Table 1 shows the results.

[0044]

[Table 1]

As is evident from the results in Table 1 above, the electrolyte solutions of Reference Examples 1-1 to 1-2 containing the specific cyclic carbonate compound and chain ester compound used in the present invention are shown in Reference Comparative Examples. It has excellent properties that cannot be predicted from 1-1 to 1-3. Specifically, it was confirmed that the solidification point was low and the viscosity was low while maintaining the dielectric constant.
On the other hand, the electrolyte solution of Reference Comparative Example 1-4, which is a combination of a conventionally used cyclic carbonate compound and a chain carbonate compound, has a high dielectric constant but a high freezing point and has a problem in low-temperature characteristics.

[Production of Lithium Secondary Battery] Next, the lithium secondary battery of the example was produced in the following procedure. <Preparation of positive electrode> Positive electrode active material LiNiO ₂ was 80 parts by mass,
A positive electrode material was prepared by mixing 10 parts by weight of acetylene black as a conductive agent and 10 parts by weight of polyvinylidene fluoride as a binder. This positive electrode material was dispersed in N-methyl-2-pyrrolidone to form a slurry. This slurry was applied to both surfaces of a positive electrode current collector made of aluminum, dried, and press-formed to obtain a positive electrode plate. Thereafter, this positive electrode plate was cut into a predetermined size, and a sheet-like positive electrode was produced by scraping off the electrode mixture at a portion to be a lead tab weld for current extraction.

<Preparation of Negative Electrode> 90 parts by mass of carbon material powder and 10 parts by mass of polyvinylidene fluoride were mixed to prepare a negative electrode material. This negative electrode material was dispersed in N-methyl-2-pyrrolidone to form a slurry. This slurry was applied to both surfaces of a copper negative electrode current collector in the same manner as the positive electrode, dried, and press-formed to obtain a negative electrode plate. Then, this negative electrode plate was cut into a predetermined size, and a sheet-shaped negative electrode was produced by scraping off the electrode mixture at a portion to be a lead tab weld for current extraction.

<Preparation of Electrolyte> Table 2 and Table 3
Were mixed at the mixing ratio shown in Table 1, and LiPF ₆ was dissolved at a concentration of 1 mol / liter to obtain a non-aqueous electrolyte.

<Assembly of Battery> The sheet-shaped positive electrode and sheet-shaped negative electrode obtained above were wound with a 25 μm-thick microporous polyethylene film interposed therebetween to form a wound electrode body. . The obtained wound electrode body was inserted into the case and held in the case. At this time, the current collecting lead having one end welded to the lead tab welding portion of the sheet-shaped positive electrode and the sheet-shaped negative electrode was joined to the positive electrode terminal or the negative electrode terminal of the case. Thereafter, the electrolytic solution was injected into the case holding the wound electrode body, and the case was hermetically sealed.
By the above procedure, φ18mm, axial length 65mm
Was manufactured.

In the following Examples and Comparative Examples, various characteristics of the lithium secondary battery were measured by the following measuring methods.

<Cycle Characteristics Test> The above-mentioned cylindrical lithium battery was placed in a thermostat at 20 ° C. in an atmosphere, and the current density per unit area of the positive electrode 1 was set at a constant current of 1.1 mA / cm ² and 4.2 V. The battery was charged at the final voltage of (CC). Thereafter, the cut-off voltage was set to 3.0 V at a constant current of 0.5 mA / cm ²
Discharge was performed at the final voltage of (CC). In the charge / discharge cycle test, the initial battery capacity of each lithium secondary battery and the battery capacity after 100 cycles of charge / discharge were measured. The battery capacity after 100 cycles of charging / discharging was shown as a ratio (referred to as a capacity retention rate) when the initial battery capacity was taken as 100%.

<Low Temperature Characteristic Evaluation Test> Evaluation was made by measuring the discharge capacity ratio (%) at −30 ° C. with respect to 20 ° C. Low temperature discharge capacity ratio = [(discharge capacity at −30 ° C.) / (20
Discharge capacity at 100 ° C.) × 100

[Examples 1-1 to 1-8, Comparative Examples 1-1 to 1]
1-4] LiP was added to the mixed solvent having the composition shown in Tables 2 and 3.
F ₆ is dissolved at a concentration of 1 mol / liter to form an electrolyte,
It was incorporated in the above lithium secondary battery. The test results are shown in Tables 2 and 3.

[0054]

[Table 2]

[0055]

[Table 3]

[0056]

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[0057]

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As apparent from the results in Tables 2 and 3, Examples 1-1 to 1-8 containing specific cyclic carbonate compounds and chain ester compounds according to the present invention were used.
It was confirmed that the electrolyte solution of Example 1 had excellent performance in low-temperature discharge capacity ratio at low temperature while maintaining the same cycle characteristics as the electrolyte solutions of Comparative Examples 1-1 to 1-4.

[0059]

By using a non-aqueous electrolyte containing a specific cyclic carbonate compound and a specific chain ester compound as a solvent according to the present invention, a non-aqueous solution having excellent cycle characteristics and improved low-temperature characteristics can be obtained. An electrolyte secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a cross section of an internal structure of a lithium secondary battery (cylindrical battery) as a nonaqueous electrolyte secondary battery of the present invention.

FIG. 2 is a schematic diagram showing a basic configuration of a lithium secondary battery as a non-aqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

 1: negative electrode 1 ': negative electrode plate 1 ": negative electrode lead 2: negative electrode current collector 3: positive electrode 3': positive electrode plate 3": positive electrode lead 4: positive electrode current collector 5: electrolytic solution 6: separator 7: positive electrode terminal 8 : Negative electrode terminal 10: non-aqueous electrolyte secondary battery 11: case 12: insulating plate 13: gasket 14: safety valve 15: PTC element

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasunori Takeuchi 7-35 Higashiogu, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. F-term (reference) 5H029 AJ00 AJ05 AK03 AL06 AM00 AM03 AM04 AM05 AM07 HJ02

Claims (6)

[Claims] In an electrolytic solution in which an electrolyte salt is dissolved in an organic solvent, at least one of a cyclic carbonate compound represented by the following chemical formula (1) and a chain ester compound represented by the following general formula (2) is used as the solvent. Non-aqueous electrolyte solution characterized by containing one kind as an essential component. Embedded image 2. The compound represented by the general formula (2)
2. The non-aqueous electrolyte according to claim 1, which is a chain carbonate compound. 3. The non-aqueous electrolyte according to claim 1, wherein the solvent further contains a 5-membered cyclic carbonate compound. 4. The non-aqueous electrolyte according to claim 3, wherein the five-membered cyclic carbonate is at least one of ethylene carbonate, propylene carbonate, and vinylene carbonate. 5. The solvent according to claim 1, wherein the content of the cyclic carbonate compound represented by the chemical formula (1) in the solvent is 1 to 50 parts by mass based on 100 parts by mass of the total solvent. Non-aqueous electrolyte. 6. A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte according to claim 1.