JP2000348764A - Nonflammable nonaqueous electrolytic solution and secondary battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonflammable nonaqueous electrolytic solution without deteriorating charge-discharge efficiency, energy density, output density, a service life or the like by including at least a specific electrolyte and phosphoric ester in the electrolytic solution. SOLUTION: An electrolyte is expressed by the formula I. In the formula I, R1 is a 1-10C hydrocarbon group that may contain an amino group, nitro group or cyano group, and part or all of hydrogen atoms of the hydrocarbon group may be substituted with halogen atoms. X+ is a cation. Phosphoric ester is preferably expressed by the formula II or formula III. In the formula II, R2, R3 and R4 may be the same or different, each being a 1-10C hydrocarbon group that may contain an amino group or the like, and part or all of hydrogen atoms of the hydrocarbon group may be substituted with halogen atoms. In the formula III, R5 is a 2-8C alkylene group, R6 is a 1-10C hydrocarbon group that may contain an amino group or the like, and part or all of its hydrogen atoms may be substituted with halogen atoms.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel flame-retardant non-aqueous electrolyte used for an electrochemical element such as a secondary battery, a primary battery, or an electric double layer capacitor, and more particularly to a flame retardant suitable for a secondary battery. To a non-aqueous electrolytic solution. Furthermore, using this electrolytic solution, for example, a cordless power supply required for portable devices, etc.
The present invention relates to a flame-retardant non-aqueous electrolyte secondary battery that can be reused by charging and is used for a power supply of an electric vehicle or the like.

[0002]

2. Description of the Related Art A battery using a non-aqueous electrolyte has a high withstand voltage,
Because of its high energy density and excellent storage properties, it is widely used as a power source for consumer electronic devices. However, lithium secondary batteries using metallic lithium for the negative electrode, despite their excellent properties, do not have sufficient charge / discharge cycle life due to the precipitation of dendritic lithium,
It has not been put to practical use yet. Therefore, instead of using metallic lithium as it is, a carbonaceous material that can occlude and release lithium ions has attracted attention and is being actively developed.
In addition, various studies have been made on a non-aqueous solvent constituting an electrolytic solution suitable for the electrolyte. Typical examples of the non-aqueous solvent include a mixture of a high dielectric constant solvent such as propylene carbonate and ethylene carbonate and a low-viscosity solvent such as diethyl carbonate and dimethoxyethane.

[0003]

However, there is a strong demand for higher energy density and higher output density, and in order to realize these demands, it is necessary to further improve safety such as flame retardancy and non-flammability. Improvement of performance is essential. Currently used non-aqueous solvents have relatively low flash points,
Flammable.

For this reason, it has been proposed to add flame-retardant phosphoric esters to the electrolyte (Japanese Patent Laid-Open No. 184/1984).
870, JP-A-8-88023, JP-A-1
0-189038-189040). However, when this type of compound is added, flame retardancy can be imparted, but the electrical conductivity is reduced, and the properties of the electrolytic solution are significantly deteriorated. Further, since the phosphate ester itself has a very high permeability, the phosphate ester penetrates into a film formed on the electrode surface and directly touches the electrode to cause an electrolysis reaction. As a result, the battery characteristics such as charge / discharge efficiency, energy density, output density, and life are significantly inferior to those before the addition of the phosphate ester, and thus have not been put to practical use. In addition, silane compounds (JP-A-03-236168-236171) proposed as flame-retardant components and fluorinated compounds (JP-A-08-138737).
Similarly, in Japanese Patent Application Laid-Open No. Hei 10-116629, the electrolyte properties and the battery properties are greatly deteriorated by the addition, and thus have not been put to practical use.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in view of the above-mentioned problems. The purpose is to provide. It is another object of the present invention to provide a flame-retardant non-aqueous electrolyte having excellent withstand voltage, electric conductivity characteristics, load characteristics and low-temperature characteristics. Another object of the present invention is to provide a flame-retardant non-aqueous electrolyte secondary battery having excellent charge-discharge cycle characteristics and a long life.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have reached the present invention. That is, the present invention provides a flame-retardant non-aqueous electrolyte containing at least an electrolyte (A) represented by the following general formula (1) and a phosphate ester (B); It is a flame-retardant non-aqueous electrolyte secondary battery comprising an electrolyte.

[0007]

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(Wherein R ¹ is a hydrocarbon group having 1 to 10 carbon atoms which may contain an amino group, a nitro group, a cyano group, a carbonyl group, a carbonic acid diester group or an ether group (a methyl group, an ethyl group) , propyl group, butyl group, hexyl group, octyl group, a phenyl group, a benzyl group, etc.), part or all of the hydrogen atoms of the hydrocarbon group may be substituted with a halogen atom. in addition, X ⁺ Represents a cation.)

[0009]

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(Wherein R ² , R ³ and R ⁴ may be the same or different and each contains an amino group, a nitro group, a cyano group, a carbonyl group, a carbonic acid diester group or an ether group). A hydrocarbon group having 1 to 10 carbon atoms (a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a phenyl group, a benzyl group, etc.), and a part of hydrogen atoms of the hydrocarbon group. Alternatively, all may be substituted by halogen atoms.)

[0011]

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Wherein R ⁵ represents an alkylene group having 2 to 8 carbon atoms, and R ⁶ represents a carbon atom which may contain an amino group, a nitro group, a cyano group, a carbonyl group, a carbonic acid diester group or an ether group. Represents a hydrocarbon group represented by Formulas 1 to 10 (eg, a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a phenyl group, and a benzyl group), and some or all of the hydrogen atoms of the hydrocarbon group are halogen. It may be substituted with an atom.)

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The flame-retardant non-aqueous electrolyte containing at least the electrolyte (A) represented by the general formula (1) and the phosphate ester (B) according to the present invention has flame retardancy and ion dissociation. It has a very large degree and excellent lithium ion conductivity.

Specific examples of the electrolyte (A) represented by the above general formula (1) of the present invention include lithium monomethyl carbonate, lithium monoethyl carbonate, lithium monopropyl carbonate, lithium monobutyl carbonate, lithium monohexyl carbonate, and monooctyl carbonate. Lithium, lithium monophenyl carbonate, lithium monobenzyl carbonate, lithium monotrifluoromethyl carbonate, lithium monotrichloromethyl carbonate, lithium monoperfluoroethyl carbonate, lithium monoperchloroethyl carbonate, lithium monoperfluoropropyl carbonate, monoperchloropropyl Lithium carbonate, lithium monoperfluorobutyl carbonate, lithium monoperchlorobutyl carbonate, lithium monoperfluorohexyl carbonate, lithium monoperfluorooctyl carbonate, lithium lithium monomethoxymethyl carbonate , Monomethoxy-ethyl lithium carbonate, mono-methoxypropyl lithium carbonate, mono ethoxymethyl lithium carbonate, mono-ethoxyethyl lithium carbonate, mono trifluoromethoxymethyl lithium carbonate,
Lithium salts such as lithium monotrifluoromethoxyethyl carbonate, lithium monotrifluoromethoxypropyl carbonate, lithium monoperfluoroethoxymethyl carbonate, lithium monoperfluoroethoxyethyl carbonate; sodium monomethyl carbonate, sodium monoethyl carbonate, sodium monopropyl carbonate, monobutyl sodium carbonate,
Sodium monohexyl carbonate, sodium monooctyl carbonate, sodium monophenyl carbonate, sodium monobenzyl carbonate, sodium monotrifluoromethyl carbonate,
Sodium monotrichloromethyl carbonate, sodium monoperfluoroethyl carbonate, sodium monoperchloroethyl carbonate, sodium monoperfluoropropyl carbonate,
Sodium monoperchloropropyl carbonate, sodium monoperfluorobutyl carbonate, sodium monoperchlorobutyl carbonate, sodium monoperfluorohexyl carbonate, sodium monoperfluorooctyl carbonate, sodium monomethoxymethyl carbonate, sodium monomethoxyethyl carbonate, monomethoxypropyl Sodium carbonate, monoethoxymethyl sodium carbonate, monoethoxyethyl sodium carbonate, monotrifluoromethoxymethyl sodium carbonate, monotrifluoromethoxyethyl sodium carbonate, monotrifluoromethoxypropyl sodium carbonate, monoperfluoroethoxymethyl sodium carbonate, monoperfluoro Sodium salts such as sodium ethoxyethyl carbonate; potassium monomethyl carbonate, potassium monoethyl carbonate, monop Potassium pill carbonate, monobutyl potassium carbonate, monohexyl carbonate, monooctyl potassium carbonate, monophenyl potassium carbonate, monobenzyl potassium carbonate, monotrifluoromethyl potassium carbonate, monotrichloromethyl potassium carbonate, monoperfluoroethyl potassium carbonate, monoperchloro Potassium ethyl carbonate, potassium monoperfluoropropyl carbonate, potassium monoperchloropropyl carbonate, potassium monoperfluorobutyl carbonate, potassium monoperchlorobutyl carbonate, potassium monoperfluorohexyl carbonate, potassium monoperfluorooctyl carbonate, monomethoxymethyl carbonate Potassium, monomethoxyethyl potassium carbonate, monomethoxypropyl potassium carbonate, monoethoxymethyl potassium carbonate, monoethoxyethyl potassium carbonate Potassium salts such as potassium monotrifluoromethoxymethyl carbonate, potassium monotrifluoromethoxyethyl carbonate, potassium monotrifluoromethoxypropyl carbonate, potassium monoperfluoroethoxymethyl carbonate, potassium monoperfluoroethoxyethyl carbonate; tetramethylammonium monomethyl carbonate , Tetramethylammonium monoethyl carbonate, tetramethylammonium monopropyl carbonate, tetramethylammonium monobutyl carbonate, tetramethylammonium monohexyl carbonate, tetramethylammonium monooctyl carbonate, tetramethylammonium monophenyl carbonate, tetramethylammonium monobenzyl carbonate, monotrifluorocarbonate Tetramethylammonium methyl carbonate, tetramethylammonium monotrichloromethyl carbonate Tetramethylammonium monoperfluoroethyl carbonate, tetramethylammonium monoperchloroethyl carbonate, tetramethylammonium monoperfluoropropyl carbonate, tetramethylammonium monoperchloropropyl carbonate, tetramethylammonium monoperfluorobutyl carbonate, monoperchloromethyl Tetramethylammonium butyl carbonate, tetramethylammonium monoperfluorohexyl carbonate, tetramethylammonium monoperfluorooctyl carbonate, tetramethylammonium monomethoxymethyl carbonate, tetramethylammonium monomethoxyethyl carbonate, tetramethylammonium monomethoxypropyl carbonate, monoethoxy Tetramethylammonium methyl carbonate, tetramethylammonium monoethoxyethyl carbonate, Tetramethylammonium trifluoromethoxymethyl carbonate, tetramethylammonium monotrifluoromethoxyethyl carbonate, tetramethylammonium monotrifluoromethoxypropyl carbonate, tetramethylammonium monoperfluoroethoxymethyl carbonate, tetramethylammonium monoperfluoroethoxyethyl carbonate, monomethyl Tetraethylammonium carbonate, tetraethylammonium monoethyl carbonate, tetraethylammonium monopropyl carbonate, tetraethylammonium monobutyl carbonate, tetraethylammonium monohexyl carbonate, tetraethylammonium monooctyl carbonate, tetraethylammonium monophenyl carbonate, tetraethylammonium monobenzylcarbonate, monoethyltetrafluoromethylcarbonate Ammonium, tetraethylammonium monotrichloromethyl carbonate, tetraethylammonium monoperfluoroethyl carbonate, tetraethylammonium monoperchloroethyl carbonate, tetraethylammonium monoperfluoropropyl carbonate, tetraethylammonium monoperchloropropyl carbonate, tetraethylammonium monoperfluorobutyl carbonate, mono Tetraethylammonium perchlorobutyl carbonate, tetraethylammonium monoperfluorohexyl carbonate, tetraethylammonium monoperfluorooctyl carbonate, tetraethylammonium monomethoxymethyl carbonate, tetraethylammonium monomethoxyethyl carbonate, tetraethylammonium monomethoxypropyl carbonate, tetraethylammonium monoethoxymethyl carbonate Monium, monoethoxyethyltetraethylammonium carbonate, monotrifluoromethoxymethyltetraethylammonium carbonate, monotrifluoromethoxyethyltetraethylammonium carbonate, monotrifluoromethoxypropyltetraethylammonium carbonate,
Monoperfluoroethoxymethyl tetraethylammonium carbonate, monoperfluoroethoxyethyl tetraethylammonium carbonate, monomethylmethyltriethylammonium carbonate, monoethylmethyltriethylammonium carbonate, monopropylmethyltriethylammonium, monobutylmethyltriethylammonium, monohexylmethyltriethylammonium, mono Methyltriethylammonium octyl carbonate, methyltriethylammonium monophenyl carbonate, methyltriethylammonium monobenzyl carbonate, methyltriethylammonium monotrifluoromethyl carbonate, methyltriethylammonium monotrichloromethyl carbonate, methyltriethylammonium monoperfluoroethyl carbonate, monoperchloroethyl Methyltriethylammonium carbonate, methyltriethylammonium monoperfluoropropyl carbonate, methyltriethylammonium monoperchloropropyl carbonate, methyltriethylammonium monoperfluorobutyl carbonate, methyltriethylammonium monoperchlorobutyl carbonate, methyltriethylammonium monoperfluorohexyl carbonate, Monoperfluorooctyl methyltriethylammonium carbonate, monomethoxymethylmethyltriethylammonium carbonate, monomethoxyethylmethyltriethylammonium carbonate, monomethoxypropylmethyltriethylammonium carbonate, monoethoxymethylmethyltriethylammonium carbonate, monoethoxyethylmethyltriethylammonium carbonate, mono Trifluoromethoxymethy Quaternary ammonium salts such as methyltriethylammonium carbonate, monotrifluoromethoxyethyl methyltriethylammonium carbonate, monotrifluoromethoxypropyl methyltriethylammonium carbonate, monoperfluoroethoxymethyl methyltriethylammonium carbonate, monoperfluoroethoxyethyl methyltriethylammonium carbonate 1-methyl-3-ethylimidazolium monomethyl carbonate, 1-methyl-3-ethylimidazolium monoethyl carbonate, 1-methyl-3-ethylimidazolium monopropyl carbonate, 1-methyl-3-ethylimidazolium monobutyl carbonate, 1-methyl-3-ethylimidazolium monohexyl carbonate, 1-methyl-3 monooctyl carbonate
-Ethyl imidazolium, 1-methyl-3-ethyl imidazolium monophenyl carbonate, 1-methyl-3-ethyl imidazolium monobenzyl carbonate, 1-methyl-3-ethyl imidazolium monotrifluoromethyl carbonate, monotrichloromethyl carbonate 1-methyl-3-ethylimidazolium, 1-methyl-3-monoperfluoroethyl carbonate
Ethyl imidazolium, monoperchloroethyl carbonate 1-
Methyl-3-ethylimidazolium, 1-methyl-3-ethylimidazolium monoperfluoropropyl carbonate,
1-methyl-3-ethylimidazolium monoperchloropropyl carbonate, 1-methyl-3-ethylimidazolium monoperfluorobutyl carbonate, 1-methyl-3-ethylimidazolium monoperchlorobutyl carbonate, monoperfluorohexyl carbonate 1-methyl-3-ethylimidazolium, 1-methyl-3-monoperfluorooctyl carbonate
Ethyl imidazolium, 1-methyl-3-ethyl imidazolium monomethoxymethyl carbonate, 1-methyl-3-ethyl imidazolium monomethoxyethyl carbonate, 1-methyl-3-ethyl imidazolium monomethoxypropyl carbonate, monoethoxymethyl carbonate 1-methyl-3-ethylimidazolium, 1-methyl-3 monoethoxyethyl carbonate
-Ethyl imidazolium, 1-methyl-3-ethyl imidazolium monotrifluoromethoxymethyl carbonate, 1-methyl-3-ethyl imidazolium monotrifluoromethoxyethyl carbonate, 1-methyl-3-ethyl monotrifluoromethoxypropyl carbonate Imidazolium, 1-methyl-3-ethyl monoperfluoroethoxymethyl carbonate imidazolium, monoperfluoroethoxyethyl carbonate 1
Imidazolium salts such as -methyl-3-ethylimidazolium; 1,2,3,4-tetramethylimidazolinium monomethyl carbonate, 1,2,3,4-tetramethylimidazolinium monoethyl carbonate, monopropyl carbonate 1 ,
2,3,4-tetramethylimidazolinium, 1,2,3,4-tetramethylimidazolinium monobutyl carbonate, 1,2,3,4-tetramethylimidazolinium monohexyl carbonate, 1,2 monooctyl carbonate , 3,4-tetramethylimidazolinium, monophenyl carbonate 1,
2,3,4-tetramethylimidazolinium, 1,2,3,4-tetramethylimidazolinium monobenzyl carbonate, 1,2,3,4-tetramethylimidazolinium monotrifluoromethyl carbonate, monotrichloro 1,2,3,4-tetramethylimidazolinium methyl carbonate, 1,2,3,4-tetramethylimidazolinium monoperfluoroethyl carbonate, 1,2,2, monoperchloroethyl carbonate
3,4-tetramethylimidazolinium, 1,2,3,4-tetramethylimidazolinium monoperfluoropropyl carbonate, 1,2,3, monoperchloropropyl carbonate
4-tetramethylimidazolinium, 1,2,3,4-tetramethylimidazolinium monoperfluorobutyl carbonate, 1,2,3,4-tetramethylimidazolinium monoperchlorobutyl carbonate, monoperfluorohexyl 1,2,3,4-tetramethylimidazolinium carbonate,
Monoperfluorooctyl carbonate 1,2,3,4-tetramethylimidazolinium, monomethoxymethyl carbonate 1,
2,3,4-tetramethylimidazolinium, 1,2,3,4-tetramethylimidazolinium monomethoxyethyl carbonate, 1,2,3,4-monomethoxypropyl carbonate
Tetramethylimidazolinium, 1,2,3,4-tetramethylimidazolinium monoethoxymethyl carbonate, 1,2,3,4-tetramethylimidazolinium monoethoxyethyl carbonate, 1, monotrifluoromethoxymethyl carbonate 2,3,4-tetramethylimidazolinium, monotrifluoromethoxyethyl carbonate 1,2,3,4-tetramethylimidazolinium, monotrifluoromethoxypropyl carbonate 1,2,3,4-tetramethylimidazolin And monoperfluoroethoxymethyl carbonate 1,2,2
And imidazolinium salts such as 3,4-tetramethylimidazolinium and 1,2,3,4-tetramethylimidazolinium monoperfluoroethoxyethyl carbonate.

Of these, those in which the cation component is a lithium cation are preferred when used in a lithium secondary battery. These electrolytes (A) may be used alone or in combination of two or more.

The concentration of the electrolyte (A) is usually 0.0
It can be used at 1 to 3 mol / L, preferably 0.1 mol / L.
It can be used at a rate of from 0.5 to 1.5 mol / L.

Further, within a range that does not impair the object of the present invention,
A commonly used electrolyte can be added. For example, alkali metal salts, quaternary ammonium salts and the like can be mentioned. Examples of the alkali metal salt include a lithium salt, a sodium salt, and a potassium salt. For example, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, and the following general formula (4) A lithium salt of a sulfonylimide represented by the following, a lithium salt of a sulfonylmethide represented by the following general formula (5), lithium acetate, lithium trifluoroacetate, lithium benzoate, lithium p-toluenesulfonate, lithium nitrate, lithium bromide, Lithium salts such as lithium iodide and lithium phenylborate; sodium salts such as sodium perchlorate, sodium iodide, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium trifluoromethanesulfonate, and sodium bromide; Potassium, potassium tetrafluoroborate, 6 Potassium phosphate, potassium salts such as potassium trifluoromethanesulfonate acid. General formula (R ⁷ SO ₂ ) (R ⁸ SO ₂ ) NLi (4) wherein R ⁷ and R ⁸ are each a perfluoro group having 1 to 4 carbon atoms which may have one or two ether groups. Shows an alkyl group. General formula (R ⁹ SO ₂ ) (R ¹⁰ SO ₂ ) (R ¹¹ SO ₂ ) CLi (5) In the formula, R ⁹ , R ¹⁰ and R ¹¹ may each have one or two ether groups. A good perfluoroalkyl group having 1 to 4 carbon atoms is shown.

Specific examples of the lithium salt of sulfonylimide represented by the general formula (4) include (CF ₃ SO ₂ ) ₂ N
Li, (C ₂ F ₅ SO ₂ ) ₂ NLi, (C ₃ F ₇ SO ₂ ) ₂ NLi,
(C ₄ F ₉ SO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ ) N
Li, (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ ) NLi, (CF ₃ S
O ₂ ) (C ₄ F ₉ SO ₂ ) NLi, (C ₂ F ₅ SO ₂ ) (C ₃ F ₇ S
O ₂ ) NLi, (C ₂ F ₅ SO ₂ ) (C ₄ F ₉ SO ₂ ) NLi, (C
F ₃ OCF ₂ SO ₂ ) ₂ NLi.

A specific example of the lithium salt of sulfonylmethide represented by the above general formula (5) is (CF ₃ SO ₂ ) ₃ CL
i, (C ₂ F ₅ SO ₂ ) ₃ CLi, (C ₃ F ₇ SO ₂ ) ₃ CLi,
(C ₄ F ₉ SO ₂ ) ₃ CLi, (CF ₃ SO ₂ ) ₂ (C ₂ F ₅ SO ₂ ) C
Li, (CF ₃ SO ₂ ) ₂ (C ₃ F ₇ SO ₂ ) CLi, (CF ₃ SO ₂ )
_{2) 2 (C 4 F 9} SO 2) CLi, (CF 3 SO 2) (C 2 F 5 SO 2) 2
CLi, (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ ) ₂ CLi, (CF ₃ S
O ₂ ) (C ₄ F ₉ SO ₂ ) ₂ CLi, (C ₂ F ₅ SO ₂ ) ₂ (C ₃ F ₇ S
O ₂ ) CLi, (C ₂ F ₅ SO ₂ ) ₂ (C ₄ F ₉ SO ₂ ) CLi, (C
F ₃ OCF ₂ SO ₂ ) ₃ CLi and the like.

The quaternary ammonium salts include tetramethylammonium / 6-fluorophosphate, tetraethylammonium / 6-fluorophosphate, tetrapropylammonium / 6-fluorophosphate, and methyltriethylammonium / 6-fluorophosphate. Salt, tetraethylammonium / 4
Fluoroborates, tetraethylammonium / perchlorates, etc., or chain amidines, cyclic amidines (imidazoles, imidazolines, pyrimidines, 1,5-
Diazabicyclo [4,3,0] nonene-5 (DBN),
1,8-diazabicyclo [5,4,0] undecene-7
(DBU)), pyrroles, pyrazoles, oxazoles, thiazoles, oxadiazoles, thiadiazoles, triazoles, pyridines, pyrazines and triazines, pyrrolidines, morpholines, piperidines, piperazines And the like.

Among them, lithium tetrafluoroborate, 6
The lithium fluorophosphate, the lithium salt of the sulfonylimide represented by the above general formula (4), and the lithium salt of the sulfonylmethide represented by the above general formula (5) show particularly high ionic conductivity and have high thermal stability. Is also preferable because it is an excellent electrolyte. These may be used alone or in combination of two or more.

The concentration of the above electrolyte is usually 0 to 2 mol.
1 / L, preferably 0.1 to 1.5
mol / L can be used.

The present invention can provide a flame-retardant non-aqueous electrolyte having excellent properties by further containing a phosphate (B) together with the above-mentioned electrolyte. Examples of the phosphate (B) used in the present invention include a chain phosphate (B-1) and a cyclic phosphate (B-2) represented by the following general formulas (2) and (3). No.

[0025]

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In the formula, R ² , R ³ , and R ⁴ may be the same or different and include an amino group, a nitro group, a cyano group,
A hydrocarbon group having 1 to 10 carbon atoms which may contain a carbonyl group, a carbonic acid diester group or an ether group (a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group,
Octyl group, phenyl group, benzyl group, etc.), and part or all of the hydrogen atoms of the hydrocarbon group may be substituted with halogen atoms.

[0027]

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In the formula, R ⁵ represents an alkylene group having 2 to 8 carbon atoms, and R ⁶ represents an alkyl group which may contain an amino group, a nitro group, a cyano group, a carbonyl group, a carbonic acid diester group or an ether group. 1 to 10 hydrocarbon groups (methyl group,
Ethyl group, propyl group, butyl group, hexyl group, octyl group, phenyl group, benzyl group, etc.), and part or all of the hydrogen atoms of the hydrocarbon group may be substituted with halogen atoms.

Specific examples of the above-mentioned chain phosphate (B-1) and cyclic phosphate (B-2) include, for example, trimethyl phosphate, phosphate Triethyl, ethyl dimethyl phosphate,
Diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, tri (trifluoroethyl) phosphate, tri (tripperfluoroethyl) phosphate, etc. And examples of the cyclic phosphate (B-2) include:
For example, ethylene methyl phosphate, ethylene ethyl phosphate,
Ethylene propyl phosphate, ethylene butyl phosphate, ethylene trifluoromethyl phosphate, ethylene perfluoroethyl phosphate, ethylene perfluoropropyl phosphate,
Ethylene perfluorobutyl phosphate, propylene methyl phosphate, propylene ethyl phosphate, propylene propyl phosphate, propylene butyl phosphate, propylene trifluoromethyl phosphate, propylene perfluoroethyl phosphate, propylene perfluoropropyl phosphate, phosphoric acid Propylene perfluorobutyl, tetramethylene methyl phosphate, tetramethylene ethyl phosphate, tetramethylene propyl phosphate, tetramethylene butyl phosphate, tetramethylene trifluoromethyl phosphate, tetramethylene perfluoroethyl phosphate, tetramethylene perphosphate Fluoropropyl, tetramethylene perfluorobutyl phosphate and the like. These can be used alone or in combination of two or more.

In the present invention, a solvent can be added as required. For example, compounds such as cyclic or chain carbonate, chain carboxylate, cyclic or chain ether, lactone compounds, nitrile compounds, amide compounds, and the like, and mixtures thereof can be used.

Examples of the cyclic carbonate include alkylene carbonates such as propylene carbonate, ethylene carbonate and butylene carbonate, and examples of the chain carbonate include dialkyl carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate. . Examples of the chain carboxylate include methyl acetate and methyl propionate, and examples of the cyclic or chain ether include tetrahydrofuran,
1,3-dioxolan and 1,2-dimethoxyethane are exemplified. Examples of the lactone compound include γ-butyrolactone, examples of the nitrile compound include acetonitrile, and examples of the amide compound include dimethylformamide. Of these, the use of a cyclic carbonate and / or a chain carbonate is preferable because of exhibiting battery performance such as high charge / discharge characteristics and output characteristics.

The mixing ratio of the above-mentioned phosphate (B) and other solvents is usually 10/90 to 90/10 by weight.
Range.

The flame-retardant non-aqueous electrolyte of the present invention may further contain an additive such as an activator, if necessary.

The flame-retardant non-aqueous electrolyte of the present invention comprises a secondary battery,
It can be used for electrochemical devices such as primary batteries and electric double layer capacitors. When the flame-retardant nonaqueous electrolyte of the present invention is used for a secondary battery, particularly excellent performance is exhibited.

The flame-retardant non-aqueous electrolyte secondary battery of the present invention uses a flame-retardant non-aqueous electrolyte having the above composition together with a positive electrode and a negative electrode. Here, in the flame-retardant non-aqueous electrolyte secondary battery of the present invention, the above-described flame-retardant non-aqueous electrolyte is completely devised. Therefore, the types and preparation methods of the electrodes, which are other battery materials, the combination of the positive electrode and the negative electrode, and the shape and preparation method of the secondary battery can all be designed within the existing technical range.

The positive electrode is made of LiCoO as an active material.
₂ , LiNiO ₂ , Li _x Ni _y Co _{1- y} O ₂ (where x, y
Depends on the charge / discharge state of the battery, and usually 0 <x <1,
0.7 <y <1.02), LiMnO ₂ , LiM
Composite oxide of lithium and one or more transition metals such as n ₂ O ₄ ; transition metal oxides such as MnO ₂ and V ₂ O ₅ ; transition metal sulfides such as MoS ₂ and TiS ₂ ; polyaniline , Polypyrrole, polyacene, polythiophene,
Conductive polymers such as polyacetylene, poly-p-phenylene, and polycarbazole; and compounds that reversibly electrolytically polymerize and depolymerize, such as disulfide compounds, can be used. Among them, a composite oxide of lithium and a transition metal is preferable because it improves battery capacity and is excellent in energy density.

In forming a positive electrode using such a positive electrode active material, a known conductive agent or binder can be added and used in combination.

The negative electrode uses a light metal or light metal ion as its active material. Such light metals include:
Examples include lithium, sodium, potassium, cesium, and aluminum. Similarly, light metal ions include lithium ion, sodium ion, potassium ion, cesium ion, and aluminum ion. Of these, lithium and lithium ion are particularly preferred in terms of battery output and energy density.

The negative electrode is composed of the active material itself or a material capable of inserting and extracting the active material. As a constituent material of such a negative electrode, a light metal itself; a compound itself having light metal ions; an alloy itself containing these light metals may be used, or a material capable of occluding and releasing such light metals or ions thereof. May be used.

Among the constituent materials of such a negative electrode, for example, materials that can occlude and release lithium or its ions include, for example, (1) graphites, fired organic polymer compounds (phenol resins, furan resins, etc.). Carbonized materials such as fired at an appropriate temperature and carbonized, cokes (pitch coke, needle coke, petroleum coke, etc.), carbon fiber, glassy carbons, pyrolytic carbons, activated carbon, etc .; (2) lithium For example, polymers such as polyacetylene and polypyrrole, which exhibit conductivity by absorbing ions, can be used. Further, as the light metal alloy, for example, a lithium-aluminum alloy or the like can be used.

Among these materials, it is preferable to use the carbonaceous material (1) from the viewpoint of improving the charge / discharge characteristics and the self-discharge characteristics.

In forming a negative electrode from such a material, a known binder or the like can be added.

The flame-retardant non-aqueous electrolyte secondary battery of the present invention contains the above-described flame-retardant non-aqueous electrolyte as an electrolyte, and is disclosed in, for example, JP-A-63-121260 and JP-A-62-162. 9
No. 0863, JP-A-8-306364, JP-A-63-32870, JP-A-6-60906, and "Battery Technology" [Vol. 6, 129 (issued in 1994)]. By using a combination of negative electrodes, the nonflammable nonaqueous electrolyte has excellent flame retardancy without impairing battery characteristics such as charge and discharge efficiency, energy density and output density, and has a long service life and excellent practicality. It can be a secondary battery. Further, the shape, form, and the like of the flame-retardant nonaqueous electrolyte secondary battery of the present invention can be arbitrarily selected, such as a cylindrical shape, a square shape, a coin shape, a card shape, and even a large size. In addition, a non-aqueous non-aqueous electrolyte secondary battery that has flame retardancy without impairing battery characteristics such as charge / discharge efficiency, energy density, and output density, and has a long service life and excellent practicability. it can.

[0044]

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 Triethyl phosphate, ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1:
In a 1: 1 mixed solvent, 0.1% lithium monocarbonate was added.
25 mol / L and lithium hexafluorophosphate (LiPF
₆ ) was dissolved in 0.5 mol / L to prepare an electrolytic solution. 1.5cm in width and 30c in length in a beaker containing electrolyte
m, soak the separator manila paper prepared to a thickness of 0.04 mm for 5 minutes. 5cm after wiping liquid dripping from Manila paper
The manila paper is stabbed over the support needles at intervals and fixed horizontally. I ignite one end of the manila paper with a lighter in a windless state and wait for it to extinguish naturally. The burning length (cm) and burning speed (cm / sec) were measured three times, respectively, and the average value was obtained. In addition, using an AC impedance meter, 10 kHz
The electric conductivity was measured at two points at 25 ° C. and −20 ° C. at z.

<Examples 2 to 5> Examples 2 and 3 were performed in the same manner as in Example 1 except that lithium monomethyl carbonate and lithium monotrifluoromethyl carbonate were used instead of lithium monoethyl carbonate. And the same evaluation and measurement were performed. In Example 1, instead of triethyl phosphate,
The electrolytes of Examples 4 and 5 were prepared in the same manner as in Example 1 except that tri (trifluoromethyl) phosphate and propylene ethyl phosphate were used, and the same evaluation and measurement were performed.

COMPARATIVE EXAMPLES 1 AND 2 Lithium hexafluorophosphate (LiPF ₆ ) was added to a solvent obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 with 0.65 m.
ol / L was dissolved to prepare an electrolytic solution. Comparative Example 1 Lithium hexafluorophosphate (LiPF ₆ ) was added to a solvent in which triethyl phosphate, ethylene carbonate, and diethyl carbonate were mixed at a volume ratio of 1: 1: 1.
An electrolytic solution prepared by dissolving mol / L was used as Comparative Example 2. Table 1 shows the results.

[0048]

[Table 1]

As is clear from Table 1, the electrolytes of Examples 1 to 5 of the present invention all exhibited excellent flame retardancy and high electric conductivity.

<Preparation of Secondary Battery> A coin-type nonaqueous electrolyte lithium secondary battery as shown in FIG. 1 was prepared. In FIG. 1, 1 is graphite, 2 is a positive electrode active material molded body, 3 is a porous separator, 4 is a negative electrode can, 5 is a positive electrode can, and 6 is a gasket. The non-aqueous electrolyte lithium secondary battery shown in FIG. 1 was prepared in the following procedure. A positive electrode active material molded body 2 prepared by mixing LiCoO ₂ with acetylene black as a conductive agent and polyvinylidene fluoride powder as a binder and press-molding the mixture was put on a nickel net placed on the bottom surface of a stainless steel positive electrode can 5. Crimped. Next, after placing the polypropylene porous separator 3 on the molded body,
Was injected, and the gasket 6 was inserted. Thereafter, the stainless steel negative electrode can 4 having the graphite 1 adhered thereto was placed on the polypropylene porous separator 3, the opening end of the positive electrode can 5 was bent inward, and the sealing portion was glass hermetically sealed. The non-aqueous electrolyte lithium secondary battery of Example 6 shown in FIG.

The same operation as in Example 6 was carried out except that the non-aqueous electrolytes having the compositions of Examples 3 and 5 were used, and the non-aqueous electrolytes of Examples 7 and 8 having the same structure as in FIG. A secondary battery was created.

As a comparative example, the same operation as in Example 6 was performed except that the electrolytic solution used in Comparative Examples 1 and 2 was used instead of the flame-retardant nonaqueous electrolytic solution. Non-aqueous electrolyte lithium secondary batteries of Comparative Examples 3 and 4 were produced.

<Evaluation of Battery Characteristics> The charge / discharge characteristics of the nonaqueous electrolyte lithium secondary battery prepared as described above were compared as follows. Set the upper limit voltage to 4.2V and set 1
The battery was charged at a constant current and a constant voltage of 10 mA at a current of 10 mA, then discharged at a low current of 1 mA to a final voltage of 3.0 V, and this charging and discharging was repeated as a predetermined number of cycles. FIG. 2 is a graph in which the charge / discharge efficiency at that time is plotted against the number of cycles. As shown in FIG. 2, Examples 6 to 8 exhibited better charge / discharge than Comparative Examples 3 and 4. In particular, the charge-discharge characteristics which were significantly inferior when the conventional phosphoric acid ester was used (Comparative Example 4) are clearly improved in Examples 6 to 8 of the present invention. It can be seen that it has been improved.

[0054]

As described above, according to the present invention, the flame-retardant non-aqueous electrolyte containing the electrolyte represented by the general formula (1) and the phosphate (B) has never been provided before. It is possible to provide a flame-retardant non-aqueous electrolyte secondary battery exhibiting excellent charge / discharge characteristics and the like even if it contains a flame-retardant component such as an acid ester, and has a great industrial value.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a lithium secondary battery prepared in an example of the present invention.

FIG. 2 is a diagram showing a comparison of charge and discharge characteristics of lithium secondary batteries prepared using various non-aqueous electrolytes.

[Explanation of symbols]

 1 Graphite 2 Positive electrode active material molded body 3 Porous separator 4 Negative electrode can 5 Positive electrode can 6 Gasket ● Cycle number and charge / discharge efficiency measurement value of Example 6 ▲ Cycle number and charge / discharge efficiency measurement value of Example 7 ■ Example 8 Cycle number and charge / discharge efficiency measured value of Comparative Example 3 × cycle number and charge / discharge efficiency measured value of Comparative Example 3 サ イ ク ル Cycle number and charge / discharge efficiency measured value of Comparative Example 4

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4H050 AB78 AB80 5H029 AJ02 AJ12 AK03 AL06 AL07 AL12 AL16 AM02 AM03 AM05 AM07 BJ03 DJ09 EJ11 HJ02

Claims (7)

[Claims] 1. A flame-retardant non-aqueous electrolyte containing at least an electrolyte (A) represented by the following general formula (1) and a phosphate (B). General formula (Wherein, R ¹ represents a hydrocarbon group having 1 to 10 carbon atoms which may contain an amino group, a nitro group, a cyano group, a carbonyl group, a carbonic acid diester group or an ether group, and a hydrogen atom of the hydrocarbon group May be partially or entirely substituted with a halogen atom, and X ⁺ represents a cation.) 2. The flame-retardant non-aqueous electrolyte according to claim 1, wherein the cation component of the electrolyte (A) is a lithium cation. 3. The non-aqueous flame-retardant electrolytic solution according to claim 1, wherein the phosphate (B) is represented by the following general formula (2) or (3). General formula (Wherein R ² , R ³ and R ⁴ may be the same or different and may contain an amino group, a nitro group, a cyano group, a carbonyl group, a carbonic acid diester group or an ether group) It represents a hydrocarbon group having 1 to 10 carbon atoms, and a part or all of the hydrogen atoms of the hydrocarbon group may be substituted with halogen atoms.) (Wherein, R ⁵ represents an alkylene group having 2 to 8 carbon atoms, R ⁶
Represents a hydrocarbon group having 1 to 10 carbon atoms which may contain an amino group, a nitro group, a cyano group, a carbonyl group, a carbonic acid diester group or an ether group, and part or all of the hydrogen atoms of the hydrocarbon group are It may be substituted with a halogen atom. ) 4. A flame-retardant non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode and the flame-retardant non-aqueous electrolyte according to claim 1. 5. A flame-retardant non-aqueous electrolyte lithium secondary battery comprising a positive electrode, a negative electrode and the flame-retardant non-aqueous electrolyte according to claim 1. 6. The flame-retardant non-aqueous electrolyte lithium secondary battery according to claim 5, wherein the active material of the negative electrode comprises lithium or lithium ion. 7. The flame-retardant non-aqueous electrolyte lithium secondary battery according to claim 5, wherein the active material of the positive electrode comprises a composite oxide of lithium and one or more transition metals.