JP2002134169A - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte and a nonaqueous electrolyte secondary battery, using the electrolyte having superior cycle characteristics and low-temperature characteristics, in which the rate of change of the electric capacity and internal resistance are small during charging and discharging repetition, and the increase in the internal resistance at a lower temperature is small, thereby maintaining high electric capacity. SOLUTION: This electrolyte, including an electrolyte salt dissolved in an organic solvent, contains a silicon compound having unsaturated bond represented in Formula (1) (wherein R1 to R6 represent alkyl group, alkoxy group, alkenyl group, alkenyloxy group, alkynyl group, alkynyloxy group, aryl group or aryloxy group; these groups may have ether bond in a chain i and n is 0 to 5, when n is 1 to 5; X represents direct bond, oxygen atom, alkylene group, alkylenedioxy group, alkenylene group, alkenylenedioxy group, alkynylene group, alkynylendioxy group, arylene group, or arylenedioxy group, where at least one of R1 to R6 and X represent unsaturated bond containing group.).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte containing a silicon compound having an unsaturated bond and a non-aqueous electrolyte secondary battery using the electrolyte. Non-aqueous liquids with excellent cycle characteristics and low-temperature characteristics that can maintain high electric capacity because the rate of change in electric capacity and internal resistance during charge / discharge is small and the increase in internal resistance at low temperatures is small when used as a liquid. The present invention relates to an electrolyte and a non-aqueous electrolyte secondary battery using the electrolyte.

[0002]

2. Description of the Related Art With the spread of portable electronic devices such as portable personal computers and handy video cameras in recent years, non-aqueous electrolyte secondary batteries having high voltage and high energy density have been used as power sources. It has become widely used. Also, due to environmental problems, battery vehicles and hybrid vehicles that use electric power as part of power have been put into practical use.

[0003] However, non-aqueous electrolyte secondary batteries exhibit a decrease in electric capacity and an increase in internal resistance at low temperatures or repeated charge / discharge, and thus lack reliability as a stable power supply source.

Various additives have been proposed for improving the stability and electric characteristics of non-aqueous electrolyte secondary batteries. For example,
Japanese Patent Application Laid-Open No. 10-326611 proposes using tetramethyl silicate as an organic solvent in an organic solvent-based electrolyte. However, this additive has the disadvantage that although the cycle characteristics are improved, the capacity is reduced. Also, Japanese Patent Application Laid-Open No. 10-55822 proposes an electrolyte solution having flame retardancy by using a silane compound such as octyltriethoxysilane as a flame retardant organic solvent. However, although this additive improves flame retardancy,
The electrical properties were not fully satisfactory. Further, Japanese Patent Application Laid-Open No. 11-16602 discloses that Si
An electrolytic solution to which an organosilicon compound having a -N bond is added has been proposed. However, although this additive can prevent the generation of halogen acid due to the incorporation of water and can prevent the battery from deteriorating to some extent, the electrical characteristics obtained by repeating the cycle are not sufficiently satisfactory.

Therefore, an object of the present invention is to provide a cycle characteristic and a low-temperature characteristic of maintaining a high electric capacity because the rate of change of electric capacity and internal resistance at the time of repetition of charge and discharge is small and the internal resistance at low temperatures is small. And a non-aqueous electrolyte secondary battery using the electrolyte.

[0006]

The present inventors have made various studies in view of the present situation, and as a result, have found that a silicon compound having an unsaturated bond containing at least one unsaturated bond is added to an electrolytic solution. Thus, it was found that a non-aqueous electrolyte having excellent cycle characteristics and low-temperature characteristics could be obtained.

The present invention has been made based on the above findings, and it is an object of the present invention to provide an electrolytic solution obtained by dissolving an electrolyte salt in an organic solvent, which contains a silicon compound having an unsaturated bond represented by the following general formula (1). An object of the present invention is to provide a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery using the electrolyte.

[0008]

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[0009]

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.

In the general formula (1), the alkyl and alkoxy groups represented by R _{1 to} R ₆ include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, Heptyl, octyl, isooctyl, 2-ethylhexyl, nonyl,
1 to 12 carbon atoms such as decyl, undecyl and dodecyl
Or an alkoxy group derived from these groups. Examples of the alkenyl group and the alkenyloxy group include alkenyl groups having 2 to 8 carbon atoms such as vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, 1,3-butadienyl, 2-pentenyl, and 2-octenyl; And an alkenyloxy group derived from the group Examples of the alkynyl group and the alkynyloxy group include alkynyl groups having 2 to 8 carbon atoms such as ethynyl, 2-propynyl, and 1,1-dimethyl-2-propynyl, and alkynyloxy groups derived from these groups. Examples of the aryl group and the aryloxy group include aryl groups having 6 to 12 carbon atoms such as phenyl, tolyl, xylyl, and tert-butylphenyl, and aryloxy groups derived from these groups.

In the general formula (1), the alkylene group and alkylenedioxy group represented by X include methylene, ethylene, trimethylene, 2,2-dimethyltrimethylene, tetramethylene, pentamethylene,
Examples thereof include an alkylene group having 1 to 8 carbon atoms such as hexamethylene or an alkylenedioxy group derived from these groups. Examples of the alkenylene group and the alkenylenedioxy group include alkenylene groups having 2 to 8 carbon atoms such as vinylene, propenylene, isopropenylene, butenylene, and pentenylene, and alkenyleneoxy groups derived from these groups. Examples of the alkynylene group and the alkynylenedioxy group include ethynylene, propynylene, butynylene, pentynylene, alkynylene groups having 2 to 8 carbon atoms such as 1,1,4,4-tetramethylbutenylene. No. Examples of the arylene group and arylenedioxy group include arylene groups having 6 to 12 carbon atoms such as phenylene, methylphenylene, dimethylphenylene, and tert-butylphenylene, and arylenedioxy groups derived from these groups.

As the silicon compound having an unsaturated bond represented by the general formula (1), more specifically, the following compound No. 1 to No. 26 and the like. However, the silicon compound used in the present invention is not limited at all by the following examples.

[0013]

Embedded image Compound No. 1

[0014]

Embedded image Compound No. 2

[0015]

[Image Omitted] Compound No. 3

[0016]

Embedded image Compound No. 4

[0017]

Embedded image Compound No. 5

[0018]

Embedded image Compound No. 6

[0019]

[Image Omitted] Compound No. 7

[0020]

Embedded image Compound No. 8

[0021]

[Image Omitted] Compound No. 9

[0022]

Embedded image Compound No. 10

[0023]

Embedded image Compound No. 11

[0024]

Embedded image Compound No. 12

[0025]

[Image Omitted] Compound No. 13

[0026]

[Image Omitted] Compound No. 14

[0027]

[Image Omitted] Compound No. Fifteen

[0028]

Embedded image Compound No. 16

[0029]

Embedded image Compound No. 17

[0030]

Embedded image Compound No. 18

[0031]

Embedded image Compound No. 19

[0032]

Embedded image Compound No. 20

[0033]

Embedded image Compound No. 21

[0034]

Embedded image Compound No. 22

[0035]

Embedded image Compound No. 23

[0036]

Embedded image Compound No. 24

[0037]

Embedded image Compound No. 25

[0038]

Embedded image Compound No. 26

The above-mentioned silicon compound having an unsaturated bond is a known compound, and its synthesis method is not particularly limited. For example, the silicon compound is obtained by a dehydrogenation coupling reaction between a hydrogen-containing silicon compound and a hydroxyl-containing silicon compound. The above compound No. 1 is obtained.

The silicon compound is a compound that easily undergoes self-polymerization, and is capable of forming a stable film by performing a polymerization reaction at the electrode interface at the beginning of the cycle, thereby suppressing an increase in interface resistance due to the cycle. Conceivable.
In order to exhibit this effect, the silicon compound is desirably contained in an amount of 0.05 to 5% by volume or less, and more desirably 0.1 to 3% by volume. 0.05
The effect is hardly recognized when it is less than the volume%,
If the content exceeds 5% by volume, the effect will not be exhibited any more, which is not only wasteful but also may adversely affect the characteristics of the electrolytic solution, which is not preferable.

The above-mentioned silicon compound according to the present invention is used as a non-aqueous electrolyte in combination with one or more non-aqueous solvents usually used as a non-aqueous electrolyte. As such a non-aqueous solvent, in particular, a combination of a chain carbonate compound and a cyclic carbonate compound is preferable. Not only excellent cycle characteristics are obtained by using this combination, but also the viscosity of the electrolytic solution and the electric capacity of the obtained battery. A non-aqueous electrolyte having a good balance of output and the like can be provided.

Examples of the non-aqueous solvent used in the non-aqueous electrolyte of the present invention are listed below. However, the non-aqueous solvent used in the present invention is not limited by the following examples.

The cyclic carbonate compound, the cyclic ester compound, the sulfone or sulfoxide compound, and the amide compound have a high relative dielectric constant, and thus play a role of increasing the dielectric constant of the electrolytic solution. Specifically, the cyclic carbonate compound includes: Examples include ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, butylene carbonate, and the like. Examples of the cyclic ester compound include γ-butyrolactone, γ-valerolactone, and the like. As the sulfone or sulfoxide compound,
Examples include sulfolane, sulfolene, tetramethylsulfolane, diphenylsulfone, dimethylsulfone, and dimethylsulfoxide. Examples of the amide compound include N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

A chain carbonate compound, a chain or cyclic ether compound, a chain ester compound or the like can lower the viscosity of the electrolytic solution. Therefore, battery characteristics such as output density can be improved, for example, the mobility of electrolyte ions can be increased. Further, since the viscosity is low, the performance of the electrolyte at a low temperature can be improved.
Specifically, examples of the chain carbonate compound include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl-n-butyl carbonate, methyl-t-butyl carbonate, and di-i-propyl. Carbonate, t-butyl-
i-propyl carbonate and the like, and as the chain or cyclic ether compound, dimethoxyethane (DM
E), ethoxymethoxyethane, diethoxyethane, tetrahydrofuran, dioxolan, dioxane and the like.

Further, as the above chain ester compound,
Carboxylic acid ester compounds represented by the following general formula (2) are exemplified. Examples of the alkyl group having 1 to 4 carbon atoms in the following general formula (2) include methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, Tertiary butyl, specifically, methyl formate, ethyl formate, methyl acetate,
Ethyl acetate, propyl acetate, sec-butyl acetate, butyl acetate, methyl propionate, ethyl propionate and the like can be mentioned. These carboxylic acid ester compounds have a low freezing point and can be added to a cyclic or chain-like carbonate compound to improve the battery characteristics even at low temperatures. The amount of the carboxylic acid ester compound to be added is preferably 1 to 50% by volume based on 100 volumes of the nonaqueous solvent. In addition, acetonitrile, propionitrile, nitromethane, and derivatives thereof can also be used.

[0046]

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Further, the alkylene biscarbonate compound classified as a chain carbonate compound represented by the following general formula (3) can lower the volatility of the electrolytic solution,
Further, since the storage characteristics at high temperatures are excellent, the battery characteristics at high temperatures can be improved.

[0048]

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In the above formula (3), R ₉ and R ₁₁
In the alkyl groups represented include methyl, ethyl, propyl, butyl, and examples of the alkylene group represented by R _10, ethylene, propylene, dimethylpropylene, and the like. Specific examples of the alkylene biscarbonate compound include 1,2-bis (methoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) ethane, and 1,2-bis (ethoxycarbonyloxy) propane. No.

The glycol diether compound represented by the following general formula (4), which is classified as a chain ether compound, has a terminal group substituted with a fluorine atom, and thus acts like a surfactant at the electrode interface. And the affinity of the non-aqueous electrolyte with the electrode can be increased, the initial internal resistance of the battery can be reduced, and the mobility of lithium ions can be increased.

[0051]

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In the above general formula (4), R ₁₂ and R ₁₄
In the alkyl group represented by methyl, trifluoromethyl, ethyl, trifluoroethyl, propyl, pentafluorophenyl propyl, isopropyl, butyl, pentyl, hexyl, heptyl, octyl and the like to, R ₁₃
Examples of the alkylene group represented by are ethylene, propylene, difluoropropylene, butylene and the like.
As the glycol diether compound, specifically, ethylene glycol bis (trifluoroethyl) ether, i-propylene glycol (trifluoroethyl) ether, ethylene glycol bis (trifluoromethyl) ether, diethylene glycol bis (trifluoroethyl) ) Ether and the like.

In order to impart flame retardancy to the non-aqueous electrolyte of the present invention, a halogen-based, phosphorus-based or other flame retardant can be appropriately added as a flame retardant.

As the phosphorus-based flame retardant, it is preferable to add at least one phosphoric ester compound represented by the following general formula (5), (6) or (7).

[0055]

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The alkyl groups represented by R ₁₅ , R ₁₆ , R ₁₇ and R ₁₉ in the above general formulas (5) and (6) include, for example, methyl, ethyl, propyl, butyl, pentyl and hexyl. Examples of the fluorine-substituted alkyl group include 2-fluoroethyl, 2,2,2-
Trifluoroethyl and the like.

The alkylene group represented by R ₁₈ in the general formula (6) includes, for example, ethylene, propylene, trimethylene, 2,2-dimethyltrimethylene and the like, and the alkenylene group includes vinylene, butenylene and the like. And the alkynylene group includes ethynylene, propynylene, 2-butynylene, 1,1,4,4-
Tetramethyl-2-butynylene, 1,4-dimethyl-
Examples thereof include 1,4-diethyl-2-butynylene and 1,4-dimethyl-1,4-diisobutyl-2-butynylene.

A trihydric alcohol residue having 3 to 18 carbon atoms represented by R ₂₀ in the general formula (7) is provided.
Examples of the divalent alcohol include glycerin, trimethylolethane, trimethylolpropane, 1,2,4
-Trihydroxybutane and the like.

As the phosphoric ester compounds represented by the above general formulas (5) to (7), more specifically, the following compound Nos. 27 to 35. However, the phosphoric ester compound used in the present invention is not limited at all by the following compounds.

[0060]

Embedded image Compound No. 27

[0061]

Embedded image Compound No. 28

[0062]

Embedded image Compound No. 29

[0063]

Embedded image Compound No. 30

[0064]

Embedded image Compound No. 31

[0065]

Embedded image Compound No. 32

[0066]

Embedded image Compound No. 33

[0067]

Embedded image Compound No. 34

[0068]

Embedded image Compound No. 35

The amount of the phosphate compound represented by the above general formulas (5) to (7) is preferably 5 to 100% by mass, and more preferably 10 to 50% by mass, based on the organic solvent constituting the electrolytic solution. Particularly preferred. If it is less than 5% by mass, a sufficient flame retarding effect cannot be obtained.

The method for synthesizing the phosphoric ester compounds represented by the above general formulas (5) to (7) is not particularly limited, but may be easily prepared by, for example, reacting phosphorus oxychloride with the corresponding alcohol. Can be synthesized.

As the electrolyte salt used in the present invention, a conventionally known electrolyte salt 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, etc., among which LiPF ₆ ,
Inorganic salts such as LiBF ₄ , LiClO ₄ , LiAsF ₆ ,
And CF ₃ SO ₃ Li, N (CF ₃ SO ₂ ) ₂ L
One or a combination of two or more salts selected from the group consisting of organic salts such as i, C (CF ₃ SO ₂ ) ₃ Li is preferable because of its excellent electrical properties.

The above-mentioned electrolyte salt has a concentration in the electrolytic solution of 0.
1 to 3.0 mol / l, especially 0.5 to 2.0 mol / l
It is preferable to dissolve in the above-mentioned non-aqueous solvent (organic solvent) so as to make liter. 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 non-aqueous electrolyte of the present invention can be suitably used as a non-aqueous electrolyte constituting a primary or secondary battery, particularly a non-aqueous electrolyte secondary battery described later.

The electrode material of the non-aqueous electrolyte secondary battery of the present invention
For example, there are a positive electrode and a negative electrode.
Slurry of material, binder and conductive material used as current collector
It is applied and dried to form a sheet. Correct
TiS as the extremely active material _Two, TiS_Three, MoS_Three, F
eS_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_FiveAnd the like. Examples of the positive electrode active material
X in the following indicates a number of 0 to 1. These positive electrode active materials
Of these, a composite oxide of lithium and a transition metal is preferable.
iCoO_Two, LiNiO_Two, LiMn_TwoO_Four, LiMn
O_Two, LiV_TwoO_ThreeAre preferred. Negative and positive active materials
Examples of the binder include polyvinylidene fluoride and polycarbonate.
Litetrafluoroethylene, EPDM, SBR, NB
R, fluororubber and the like, but are not limited thereto.
No.

As the negative electrode, one obtained by slurrying a negative electrode active material and a binder with a solvent, applying the slurry to a current collector, and drying it to form a sheet is used. 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. The 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, but are not limited to, graphite fine particles, carbon black such as acetylene black, and amorphous carbon fine particles such as needle coke. 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, polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate,
Polyethers such as polyamides, polyimides, polyethylene oxides and polypropylene oxides, various celluloses such as carboxymethylcellulose and hydroxypropylcellulose, and high molecular compounds mainly composed of poly (meth) acrylic acid and various esters thereof and the like. Derivatives, films made of copolymers and mixtures thereof, and the like are included. 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.

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 then heat-treated, 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 crystals 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 electrode material, the electrolyte and the separator used in the non-aqueous electrolyte secondary battery of the present invention are preferably phenol-based antioxidants, phosphorus-based antioxidants, thioether-based oxidants, for the purpose of further improving safety. You may add an inhibitor and a hindered amine light stabilizer.

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, and 0.01 to 10 parts by weight, More preferably, 0.05 to 5 parts by weight is used.

Examples of the phosphorus-based antioxidants include:
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 thereof include dialkylthiodipropionates such as dilauryl thiodipropionate, dimyristyl thiodipropionate, and distearyl thiodipropionate, and pentaerythritol tetra (β-alkylmercaptopropionate).

Examples of the hindered amine light stabilizer include, for example, 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, 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 structure is not particularly limited in its shape, and can be used as batteries of various shapes such as coin type, cylindrical type, square type and the like. FIG. 1 shows an example of a coin-type battery of the non-aqueous electrolyte secondary battery of the present invention, and FIGS. 2 and 3 show an example of a cylindrical battery of the non-aqueous electrolyte secondary battery of the present invention.

In the coin-type non-aqueous electrolyte secondary battery 10 shown in FIG. 1, 1 is a positive electrode capable of releasing lithium ions,
1a is a positive electrode current collector, 2 is a negative electrode made of a carbon chamber material capable of occluding and releasing lithium ions released from the positive electrode 1;
a is a negative electrode current collector, 3 is the non-aqueous electrolyte of the present invention, 4 is a stainless steel positive electrode case, 5 is a stainless steel negative electrode case,
Reference numeral 6 denotes a polypropylene gasket, and reference numeral 7 denotes a polyethylene separator.

In the cylindrical non-aqueous electrolyte secondary battery 10 'shown in FIGS. 2 and 3, 11 is a negative electrode, 12 is a negative electrode assembly, 13 is a positive electrode, 14 is a positive electrode current collector, and 15 is a Inventive nonaqueous electrolyte, 16 is a separator, 17 is a positive electrode terminal, 1
8 is a negative electrode terminal, 19 is a negative electrode plate, 20 is a negative electrode lead, 21
Is a positive electrode plate, 22 is a positive electrode lead, 23 is a case, 24 is an insulating plate, 25 is a gasket, 26 is a safety valve, 27 is PTC
Element.

Although the action mechanism of the present invention is not clear, it is considered that in the initial cycle, the silicon compound used in the present invention undergoes a polymerization reaction at the electrode interface to form a film. For this reason, it is considered that since the coating is more stable than in the case where no silicon compound is added, side reactions between the electrode and the electrolyte during the cycle can be suppressed, and an increase in internal resistance due to the cycle can be suppressed. . In addition, since the resistance of the coating is low at a low temperature, it is considered that a high discharge capacity can be maintained.

[0089]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited by the following examples.

[Production of Positive Electrode] LiNi was used as a positive electrode active material.
85 parts by weight of O ₂ , acetylene black 10 as a conductive agent
Parts by weight, polyvinylidene fluoride (PVD)
F) 5 parts by weight were mixed to obtain a positive electrode material. This positive electrode material was dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry. This slurry was applied to both sides of an aluminum positive electrode current collector, dried, and then pressed,
A positive electrode plate was used. Thereafter, the positive electrode plate was cut into a predetermined size, and a sheet-shaped positive electrode was manufactured by scraping off the electrode mixture at a portion to be a lead tab weld for current extraction.

[Preparation of Negative Electrode] 92.5 parts by weight of carbon material powder and 7.5 parts by weight of PVDF were mixed to prepare a negative electrode material. This negative electrode material was dispersed in NMP to form a slurry. This slurry was applied to both surfaces of a negative electrode current collector made of copper in the same manner as the positive electrode, dried, and press-formed to obtain a negative electrode plate.
Thereafter, the negative electrode plate was cut into a predetermined size, and a portion of the electrode mixture serving as a lead tab weld for current extraction was scraped off to produce a sheet-shaped negative electrode.

[Preparation of Nonaqueous Electrolyte] That is, nonaqueous electrolytes were prepared as described in Examples 1-1 to 1-31 and Comparative Examples 1-1 to 1-3 described later. The organic solvent was mixed at the following volume%, LiPF ₆ was dissolved at a concentration of 1 mol / liter, and the test compound (described in Table 1) was added at the blending amount (vol%) shown in Table 1. A non-aqueous electrolyte was used.

[Preparation of Battery] The sheet-shaped positive electrode and sheet-shaped negative electrode obtained as described above were wound with a 25 μm-thick microporous polyethylene film interposed therebetween to form a wound electrode body. Formed. The obtained wound electrode body was inserted into the case and held inside the case. At this time, the current collecting lead having one end welded to the lead tab welding portion of each 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 nonaqueous electrolyte was injected into a case holding the wound electrode body, and the case was hermetically sealed. By the above procedure, φ18
A cylindrical non-aqueous electrolyte secondary battery (cylindrical lithium secondary battery) having a length of 65 mm and an axial length of 65 mm was produced.

Various characteristics of the cylindrical lithium secondary battery were measured by the following measuring methods. The results are shown in Table 1 below.

<Initial Discharge Capacity> First, charging current 0.25
The battery was charged at a constant current and a constant voltage of 4.1 V at mA / cm ² , and was discharged at a constant current of 3.03 mA / cm ² to 3.0 V. Then constant-current constant-voltage charging to 4.1V at a charging current 1.1 mA / cm ^2, after four constant current discharge to 3.0V at a discharge current 1.1 mA / cm ^2, the charging current 1.
Constant-current constant-voltage charge at 1 mA / cm ² up to 4.1 V, the discharge current 0.33 mA / cm ² up to 3.0V constant current discharge, the discharge capacity at this time was a battery initial capacity. The measurement was performed in a 20 ° C. atmosphere.

<High temperature cycle characteristic test>
Battery in a constant temperature bath at an ambient temperature of 60 ° C.
Charge current 2.2 mA / cm^TwoConstant current charging up to 4.1V
And a discharge current of 2.2 mA / cm ^TwoConstant current discharge up to 3V
Was repeated 500 times. afterwards,
Return the ambient temperature to 20 ° C. and charge current 1.1 mA / c
m^TwoConstant current constant voltage charge to 4.1V, discharge current 0.3
3mA / cm^TwoAnd discharge at a constant current to 3.0 V at this time.
The ratio of the discharge capacity of the battery to the initial capacity of the battery is defined as the discharge capacity maintenance rate.
Was.

<Measurement of Internal Resistance Increase Rate> The internal resistance of the battery was measured by charging at a constant current and a constant voltage of 3.75 V at 20 ° C. or −30 ° C. at a charging current of 1.1 mA / cm ^2. Impedance measuring device manufactured by Toyo Corp .: Frequency response analyzer solartron 126
0, potentio / galvanostat solartron
1287) using a frequency of 100 kHz to 0.02H
Scanning was performed up to z, and a Cole-Cole plot showing an imaginary part on the vertical axis and a real part on the horizontal axis was created. Then, this call-
In the Cole plot, the arc portion was fitted with a circle, and the larger of the two points intersecting the real part of the circle was taken as the resistance value, which was taken as the internal resistance of the battery. The rate of increase in the internal resistance was defined by the following equation by measuring the internal resistance before and after the cycle test. (Internal resistance increase rate) = (Resistance value after cycle test) /
(Resistance value before cycle test)

<Low temperature property evaluation test>
The discharge capacity ratio at 0 ° C. and the internal resistance ratio were measured. Discharge capacity ratio = (discharge capacity at −30 ° C.) / (Discharge capacity at 20 ° C.) Internal resistance ratio = (internal resistance at −30 ° C.) / (Internal resistance at 20 ° C.)

[Examples 1-1 to 1-31 and Comparative Example 1-
1-1-1] Li in a mixed solvent composed of 30% by volume of ethylene carbonate and 70% by volume of diethyl carbonate
PF6 was dissolved at a concentration of 1 mol / liter, and a test compound (see Table 1) was further added to prepare an electrolytic solution. In Comparative Example 1, no test compound was added, and in Comparative Examples 1-2 and 1-3, the following comparative compound No. was used as a test compound. 3
6 and 37 were used, respectively. As a result, Comparative Example 1-1
Assuming that the initial battery capacity in Example 1 was 100, the initial battery capacities of the other Examples and Comparative Examples also showed values equal to or greater than those.

[0100]

[Table 1]

[0101]

Embedded image Comparative compound No. 36

[0102]

Embedded image Comparative compound No. 37

[Examples 2-1 to 2-10 and Comparative Example 2-
1-2-2] LiPF ₆ was added to a mixed solvent consisting of 30% by volume of ethylene carbonate, 60% by volume of diethyl carbonate, and 10% by volume of triethyl phosphate in an amount of 1 mol / L.
The solution was dissolved at a concentration of 1 liter, and a test compound (see Table 2) was added at 0.5% by volume to obtain a non-aqueous electrolyte.

Then, the discharge capacity retention rate (%) after 500 cycles and the internal resistance increase rate (%) after 500 cycles were measured by the same measurement method as in the high-temperature cycle characteristic test and the measurement of the internal resistance increase rate, respectively. It was measured. Further, a flame retardancy test was also performed by the method described below. The results are shown in Table 2 below.

<Flame Retardancy Test> The non-aqueous electrolyte described in Examples 2-1 to 2-10 and Comparative Examples 2-1 to 2-2 was added with a width of 15%.
The separator was immersed in a 0.04 mm-thick manila paper cut to a length of 320 mm and a length of 320 mm. Thereafter, the separator-manila paper was suspended vertically for 3 minutes to remove excess non-aqueous electrolyte. The manila paper for a separator impregnated with the non-aqueous electrolyte was inserted horizontally into the support needles of the sample table having the support needles at intervals of 25 mm and fixed horizontally. This sample table is 25
Put it in a metal box of 0mm x 250mm x 500mm,
One end of the separator manila paper was ignited with a lighter, and the burned length (burning length) of the separator manila paper was measured.
The case where the burning length was less than 10 mm was evaluated as ○ as having self-extinguishing property, and the case where the burning length was 10 mm or more was evaluated as × as having no self-extinguishing property.

[0106]

[Table 2]

Examples 3-1 and 3-5 LiPF ₆ was dissolved at a concentration of 1 mol / l in a mixed solvent having the composition shown in Table 3 below. 1 (see Table 3)
Was added to obtain a non-aqueous electrolyte. Then, the discharge capacity ratio (%) was measured by the same measurement method as in the low-temperature characteristic evaluation test. The results are shown in Table 3 below.

[0108]

[Table 3]

As is clear from the evaluation results in Tables 1 and 2, the non-aqueous electrolyte secondary battery using the non-aqueous electrolyte to which the silicon compound of the present invention was added exhibited a decrease in discharge capacity ratio due to cycling. Is small. On the other hand, it was confirmed that the non-aqueous electrolyte secondary batteries using the non-aqueous electrolytes of Comparative Examples 1-1 and 2-1 in which the silicon compound was not added had significantly reduced discharge capacity after cycling. did it.

Further, it was confirmed that when the silicon compound according to the present invention was added even at a low temperature, the discharge capacity could be improved and the internal resistance could be reduced.

Further, in Table 3 above, by blending an ester compound having a low freezing point as a solvent of the low-temperature electrolyte, the test of Example 1-4 (electrolyte containing no ester compound having a low freezing point) was carried out. As a result, it was confirmed that the discharge capacity at low temperature was improved.

[0112]

The use of the non-aqueous electrolyte to which the silicon compound of the present invention is added can provide a non-aqueous electrolyte secondary battery having excellent cycle characteristics and low-temperature characteristics.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing an example of the structure of a coin-type battery of the non-aqueous electrolyte secondary battery of the present invention.

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

FIG. 3 is a perspective view showing a cross section of an internal structure of a cylindrical battery of the nonaqueous electrolyte secondary battery of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Positive electrode collector 2 Negative electrode 2a Negative electrode collector 3 Electrolyte 4 Positive case 5 Negative case 6 Gasket 7 Separator 10 Coin type non-aqueous electrolyte secondary battery 10 'Cylindrical non-aqueous electrolyte secondary battery DESCRIPTION OF SYMBOLS 11 Negative electrode 12 Negative electrode assembly 13 Positive electrode 14 Positive electrode assembly 15 Electrolyte solution 16 Separator 17 Positive terminal 18 Negative terminal 19 Negative plate 20 Negative lead 21 Positive plate 22 Positive lead 23 Case 24 Insulating plate 25 Gasket 26 Safety valve 27 PTC element

Continuing from the front page (72) Inventor Naohiro Kubota Asahi Denka Kako Kogyo Co., Ltd., 7-2-35 Higashiogu, Arakawa-ku, Tokyo (72) Inventor Yasutake Takeuchi 7-2-35 Higashiogu, Arakawa-ku, Tokyo Asahi Denka F-term in Industrial Co., Ltd. (reference) 5H029 AJ02 AJ05 AK02 AK03 AK05 AL01 AL06 AL12 AL16 AM02 AM03 AM04 AM07 BJ02 BJ03 DJ08 EJ11

Claims (11)

[Claims] 1. A non-aqueous electrolytic solution characterized in that an electrolytic solution obtained by dissolving an electrolyte salt in an organic solvent contains a silicon compound having an unsaturated bond represented by the following general formula (1). Embedded image 2. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte contains a silicon compound in which n is 1 in the general formula (1). 3. In the above general formula (1), R _{1 to} R ₆
The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte contains a silicon compound in which at least one of them is a vinyl group. 4. The non-aqueous electrolyte according to claim 1, wherein in the general formula (1), X contains a silicon compound in which X is an oxygen atom. 5. The non-aqueous electrolyte according to claim 1, wherein in the general formula (1), X contains a silicon compound in which X is an ethynylene group. 6. The organic solvent according to claim 1, wherein the organic solvent contains at least one selected from the group consisting of non-aqueous solvents consisting of carbonates, lactones, ethers, sulfolanes and dioxolanes. Non-aqueous electrolyte. 7. The non-aqueous electrolytic solution according to claim 1, wherein said electrolytic solution contains at least one or more cyclic carbonate compounds and at least one chain carbonate compound. 8. The non-aqueous electrolyte according to claim 7, further comprising a carboxylic acid ester compound represented by the following general formula (2). Embedded image 9. The method according to claim 8, wherein the electrolyte salt comprises lithium ion and PF
₆, BF_Four, ClO _FourAnd AsF₆A selected from
Inorganic salt and lithium ion
SO_ThreeCF_Three, N (CF_ThreeSO_Two)_Two, C (CF_ThreeSO
_Two)_ThreeAnd organic salts composed of these derivatives
A combination with at least one or two or more salts selected from the group
The non-water according to any one of claims 1 to 8, wherein the non-water is combined.
Electrolyte. 10. The non-aqueous electrolyte according to claim 1, which contains 0.05 to 5% by volume of the silicon compound having an unsaturated bond represented by the general formula (1). 11. A non-aqueous electrolyte secondary battery comprising the non-aqueous electrolyte according to claim 1 as an electrolyte.