JP2001307770A - Electrolytic solution for lithium storage battery and secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution having improved battery life and a secondary battery using the same. SOLUTION: The nonaqueous electrolytic solution comprises a nonaqueous solvent, an electrolyte, hydrogen fluoride and a compound having carboxyl or carboxylic anhydride groups. The nonaqueous electrolytic solution secondary battery comprises using the same.

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 having excellent charge / discharge characteristics and a secondary battery using the same. More specifically, the present invention relates to an electrolyte suitable for a lithium secondary battery containing hydrogen fluoride, a compound having a carboxyl group or a carboxylic anhydride group, a non-aqueous solvent, and an electrolyte, and a secondary battery using the same.

[0002]

BACKGROUND OF THE INVENTION A battery using a non-aqueous electrolyte has a high voltage, a high energy density, and a high reliability such as storability, so that it is widely used as a power source for consumer electronic devices. Have been.

As such a battery, there is a non-aqueous electrolyte secondary battery, a typical example of which is a lithium ion secondary battery. Carbonate compounds having a high dielectric constant are known as non-aqueous solvents used for such a purpose, and the use of various carbonate compounds has been proposed. As an electrolytic solution, LiBF ₄ , LiPF ₆ , LiPF ₆ , a mixed solvent of the high dielectric constant carbonate compound solvent such as propylene carbonate and ethylene carbonate, and a low viscosity solvent such as diethyl carbonate.
A solution in which an electrolyte such as LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , or Li ₂ SiF ₆ is mixed is used.

[0004] On the other hand, research on electrodes has been promoted with the aim of increasing the capacity of batteries, and carbon materials capable of occluding and releasing lithium are used as negative electrodes of lithium ion secondary batteries. In particular, highly crystalline carbon such as graphite has characteristics such as a flat discharge potential, and is therefore used as most negative electrodes of currently commercially available lithium ion secondary batteries. However, on the negative electrode described above,
Depending on the type of the non-aqueous solvent of the electrolytic solution, there is a problem that the electrolytic solution is reductively decomposed, albeit slightly, and this reductive decomposition is particularly remarkable at a high temperature. When reductive decomposition occurs, there is a problem in that the reaction product covers the electrodes, hinders the movement of lithium ions, and the load characteristics of the battery deteriorate.

[0005] For this reason, as a non-aqueous solvent having a high dielectric constant used for the electrolytic solution, ethylene carbonate which is solid at ordinary temperature but hardly undergoes a reductive decomposition reaction continuously can be used. Attempts have been made to suppress the reductive decomposition reaction by the addition. These measures have improved the charge / discharge characteristics of batteries, but further improvements are required.

[0006]

SUMMARY OF THE INVENTION In order to meet the above demand, an object of the present invention is to provide an electrolyte for a lithium battery which suppresses deterioration of the load characteristics of a battery and consequently gives excellent load characteristics. Another object of the present invention is to provide a secondary battery including the electrolytic solution.

[0007]

The present invention provides a non-aqueous solvent,
0.001 to 0.001 for electrolyte, non-aqueous solvent and electrolyte
Provided is a non-aqueous electrolyte containing 0.7% by weight of hydrogen fluoride and 0.01 to 4.0% by weight of a compound having a carboxyl group or a carboxylic anhydride group based on a non-aqueous solvent and a lithium salt. I do.

The compound having a carboxyl group or a carboxylic acid anhydride group has 4 to 20 carbon atoms and 2 in the molecule.
A non-aqueous electrolyte which is a compound having at least one carboxyl group or at least one carboxylic anhydride group and having a carbon-carbon unsaturated group is a preferred embodiment of the present invention.

The non-aqueous solvent is at least one selected from compounds represented by the following general formulas (1a) and (1b):
Non-aqueous electrolytes that are cyclic carbonates and / or chain carbonates are also a preferred embodiment of the present invention.

Embedded image (In the formula, R ^{1 to} R ⁴ may be the same or different from each other, and are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.)

[0010] The present invention provides a secondary battery containing the above non-aqueous electrolyte.

The present invention also relates to a carbon material capable of doping and undoping lithium metal, a lithium-containing alloy or lithium ion, a tin oxide capable of doping and undoping lithium ion, and a doping and undoping of lithium ion. Including at least one negative electrode active material selected from possible titanium oxide, niobium oxide, vanadium oxide, transition metal nitride capable of doping and undoping lithium ions and silicon capable of doping and undoping lithium ions A negative electrode, a positive electrode including at least one positive electrode active material selected from a transition metal oxide, a transition metal sulfide, a composite oxide of lithium and a transition metal, a conductive polymer material, and a carbon material; And a non-aqueous electrolyte according to any one of the above.

Further, the present invention provides a lithium ion secondary battery in which the negative electrode active material is a carbon material capable of doping / dedoping lithium ions.

Next, the non-aqueous electrolyte according to the present invention and a secondary battery using this electrolyte will be described in detail. The non-aqueous electrolyte according to the present invention contains a non-aqueous solvent, an electrolyte, hydrogen fluoride, and a compound having a carboxyl group or a carboxylic anhydride group. Hereinafter, each of them will be described in detail.

Hydrogen Fluoride The non-aqueous electrolyte of the present invention contains hydrogen fluoride as an essential component. As a method of adding hydrogen fluoride to the electrolytic solution, a method of directly blowing a predetermined amount of hydrogen fluoride gas into the electrolytic solution can be adopted. Further, the electrolyte used in the present invention is L
In the case of a lithium salt containing fluorine such as iPF ₆ or LiBF ₄ , water may be added to the electrolytic solution by utilizing the reaction between water and the electrolyte shown in the following formula, and may be generated in the electrolytic solution. .

[Formula 1] LiMF _n + H ₂ O → LiPF _(n−2) O + 2HF (where M = P, B, etc., and M = P
When n = 6, n = 4 when M = B. )

When water is added to the electrolytic solution to indirectly generate HF in the electrolytic solution, two molecules of HF are generated almost quantitatively from one molecule of water. Calculate and add according to the concentration. Specifically, the desired H
Water of 0.45 times (weight ratio) the amount of F is added.

As the compound that generates HF by utilizing the reaction with the electrolyte, a protic compound having a strong acidity other than water can be used. Specific examples of such compounds include alcohols such as methanol, ethanol, ethylene glycol, and propylene glycol.

Compounds having a carboxyl group or a carboxylic anhydride group 1) Compounds having a carboxyl group The compounds having a carboxyl group used in the present invention are exemplified below. Carboxyl groups are linked to hydrocarbon groups
Combined compounds formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, stearic acid, cyclohexylacetic acid and the like.

The hydrocarbon group containing an unsaturated group such as carbon
Compounds with a boxyl group bonded acrylic acid, methacrylic acid, crotonic acid, itaconic acid,
Sorbic acid, cinnamic acid, 10-undecenoic acid, linoleic acid, fumaric acid, maleic acid, norbornene dicarboxylic acid, furan carboxylic acid, orotic acid, imidazole dicarboxylic acid, orotic acid, acetylene carboxylic acid, acetylenedicarboxylic acid, norbornene carboxylic acid, Norbornene dicarboxylic acid, butenedicarboxylic acid, hexenedicarboxylic acid, octenedicarboxylic acid, cyclopentenedicarboxylic acid, cyclohexenedicarboxylic acid, cyclooctenedicarboxylic acid and the like.

Carboxylic acid is used as the halogenated hydrocarbon group.
There bound compound trifluoroacetic acid, difluoroacetic acid, pentafluoropropionic acid, perfluoro decanoate dichroic acid, trichloroacetic acid, dichloroacetic acid, hexafluoro glutaric acid, fluoromalonic acid, perfluoropentane acid, perfluoro nonanoic acid.

Compounds having two or more carboxyl groups: oxalic acid, malonic acid, methylmalonic acid, ethylmalonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
Sebacic acid, cyclohexanedicarboxylic acid fumaric acid, camphoric acid, malic acid, glutamic acid, mucinic acid, benzenetetracarboxylic acid, aurintricarboxylic acid, citric acid, ethylenediaminetetraacetic acid, nitrilo-3-propionic acid and the like.

Compound in which a carboxyl group is bonded to an aromatic group
Things benzoic acid, phthalic acid, cumin acid, ethoxy benzoate, ethyl benzoate, hydroxybenzoic acid, dihydroxybenzoic acid, dimethoxybenzoic acid, acetyl benzoic acid, aminobenzoic acid, anthranilic acid, acetyl anthranilic acid,
Gallic acid, fluorobenzoic acid, protocatechuic acid, salicylic acid, acetylsalicylic acid, lithium sulfosalicylate, toluic acid, vanillic acid, benzoylbenzoic acid, biphenylcarboxylic acid, butoxybenzoic acid, 5 (6) -carboxyfluorescein, 4-carboxyanhydride phthalate Acid, trimesic acid, pyromellitic acid, etc.

Substitution having an oxo group or an oxy group
Compounds with a carboxyl group attached to the group Aspartic acid, acetylpropionic acid, benzoylformic acid, camphoric acid, tartaric acid, dibenzoyltartaric acid, oxyformic acid, oxydiacetic acid, oxoglutaric acid, glycolic acid, lactic acid, glyceric acid glycerate, pyruvate , Methoxyacetic acid and the like.

A carboxyl group is substituted for the amino group-containing substituent.
Compound but bound alanine, betaine, and carbamate.

A carboxyl group is bonded to a nitrogen-containing aromatic ring
Compounds nicotinic acid, citrazic acid, isosincomeronic acid, isonicotinic acid, pyridinedicarboxylic acid and the like.

Compound represented by the following general formula (2)

Embedded image (R ⁵ and R ⁶ represent a substituent having 1 to 12 carbon atoms.
^7, R ⁸ are hydrogen or carbon atoms represents from 1 to 12 substituents. R ^{5 to} R ⁸ may be the same or different. Also, R
⁵ and R ⁶ may be chemically bonded to each other. n is an integer of 0-6. )

As the compound represented by the general formula (2),
The following are mentioned. Barbituric acid-N, N-di (carboxyethyl), barbituric acid-N- (carboxyethyl), diethyl barbituric acid-N, N-carboxyethyl, diethyl barbituric acid-N-carboxyethyl, carboxyethyl alloxan , Dicarboxyethyl alloxane, N-carboxymaleimide, N-carboxymethylmaleimide, N-carboxyethylmaleimide, N-carboxyethylphthalimide,
Methyl-N- (carboxyethyl) carbamate, methyl-N, N-di (carboxyethyl) carbamate, methyl-N-methyl-N-carboxyethylcarbamate, N- (carboxyethyl) formamide, N, N-
Di (carboxyethyl) formamide, N-methyl-
N-carboxyethylformamide, N- (carboxyethyl) acetamide, N, N-di (carboxyethyl) acetamide, N-methyl-N-carboxyethylacetamide, N-carboxyethylurea, N, N
-Di (carboxyethyl) urea, N, N, N-tri (carboxyethyl) urea, N, N, N, N-tetra (carboxyethyl) urea, N-carboxyethylpyrrolidinone, N-carboxyethyloxazolidinone, N
-Carboxyethylimidazolidinone, N, N-di (carboxyethylimidazolidinone), N-carboxyethyl-N-methylimidazolidinone, carbamic acid, N
-Methylcarbamic acid, N, N-dimethylcarbamic acid, N, N-diethylcarbamic acid, N-carboxyethylsuccinimide, hydantoin-N-carboxyethyl, hydantoin-N, N-di (carboxyethyl), uric acid-N -Carboxyethyl, uric acid-N, N-di (carboxyethyl), uric acid-N, N, N-tri (carboxyethyl), uric acid-N, N, N, N-tetra (carboxyethyl), tricarboxyisocyanurate Ethyl and the like.

Of the carboxyl group-containing compounds exemplified above, a compound having 3 to 20 carbon atoms in which a carboxyl group is bonded to a substituent containing a carbon-carbon unsaturated group is desirable. Further, a compound having 4 to 20 carbon atoms in which two or more carboxyl groups are bonded is more preferable. The presence of the carbon-carbon unsaturated group not only suppresses the deterioration of the load characteristics during the life test, but also significantly enhances the capacity retention rate during the high-temperature storage test.

2) Compound having a carboxylic anhydride group The compounds having a carboxylic anhydride group used in the present invention are exemplified below. Compounds in which a carboxylic anhydride group is bonded to a hydrocarbon group: acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, caproic anhydride, cyclohexylacetic anhydride,
Malonic anhydride, methylmalonic anhydride, ethylmalonic anhydride, succinic acid, glutaric anhydride, adipic anhydride, pimelic anhydride, sebacic anhydride, cyclohexanedicarboxylic anhydride, citric anhydride Such.

Anhydrous carboxyl is substituted for a substituent containing a carbon-carbon unsaturated group.
Compounds to which a boric acid group is bound Acrylic anhydride, methacrylic anhydride, crotonic anhydride, itaconic anhydride, sorbic anhydride, cinnamic anhydride, fumaric anhydride, maleic anhydride, methyl maleic acid Anhydride, ethyl maleic anhydride, dimethyl maleic anhydride, diethyl maleic anhydride, methyl ethyl maleic anhydride, norbornene dicarboxylic anhydride, furan carboxylic anhydride, acetylene carboxylic anhydride, acetylene dicarboxylic anhydride Anhydride, norbornene carboxylic anhydride, butenedicarboxylic anhydride, hexenedicarboxylic anhydride, octenedicarboxylic anhydride, cyclopentenedicarboxylic anhydride, cyclohexenedicarboxylic anhydride, cyclooctenedicarboxylic anhydride and the like.

A carboxylic anhydride group is substituted for a halogenated hydrocarbon group.
Compounds to which trifluoroacetic anhydride, difluoroacetic anhydride, pentafluoropropionic anhydride, trichloroacetic anhydride, dichloroacetic anhydride, hexafluoroglutaric anhydride, fluoromalonic anhydride, perfluoropentanoic anhydride And perfluorononanoic anhydride.

Conversion of a carboxylic anhydride group to an aromatic group
Compound benzoic anhydride, phthalic anhydride, cumic anhydride, ethoxybenzoic anhydride, ethylbenzoic anhydride, hydroxybenzoic anhydride, fluorobenzoic anhydride, salicylic anhydride, benzoylbenzoic anhydride , Biphenylcarboxylic anhydride and the like.

Substitution having an oxo group or an oxy group
Compounds in which carboxylic anhydride groups are bonded to groups aspartic anhydride, acetylpropionic anhydride,
Tartaric anhydride, oxydiacetic anhydride, oxoglutaric anhydride, lactic anhydride, methoxyacetic anhydride and the like.

Carboxylic anhydride is used as a substituent having an amino group.
Compounds to which groups are bonded, such as alanine anhydride, betaine anhydride, and carbamic anhydride.

A carboxylic anhydride group is bonded to the nitrogen-containing aromatic ring.
Compounds nicotinic anhydride, isonicotinic anhydride, pyridinedicarboxylic anhydride and the like.

Among the compounds having a carboxylic anhydride group exemplified above, a carboxylic anhydride group is bonded to a substituent containing a carbon-carbon unsaturated group, such as a maleic anhydride derivative or norbornene dicarboxylic anhydride. A compound having 4 to 20 carbon atoms is desirable. The presence of the carbon-carbon unsaturated group not only suppresses the deterioration of the load characteristics during the life test, but also significantly enhances the capacity retention rate during the high-temperature storage test.

A compound having a carboxyl group or a carboxylic anhydride group at an added concentration has an effect of suppressing deterioration of load characteristics of a battery after a life test even when used alone. For hydrogen fluoride, the effect of suppressing the deterioration of the load characteristics is not significant. However, when both compounds are used in combination, a synergistic effect occurs, and the effect of suppressing a decrease in load characteristics further increases. From the viewpoint of expressing such a synergistic effect and reducing the loss of battery capacity,
The amount of hydrogen fluoride added is preferably 0.0005 to 0.7% by weight, more preferably 0.01 to 0.3% by weight, and still more preferably 0.02 to 0.7% by weight, based on the total amount of the nonaqueous solvent and the electrolyte. 0.2% by weight.

The addition amount of the compound having a carboxyl group or a carboxylic anhydride group is determined based on the total amount of the non-aqueous solvent and the electrolyte, from the viewpoint of exhibiting the effect of suppressing deterioration of load characteristics and reducing the loss of battery capacity. For 0.
It is preferably from 0.1 to 4% by weight, more preferably from 0.1 to 4% by weight.
It is 3.5% by weight, more preferably 0.2 to 3% by weight.

When expressed as a combined ratio of hydrogen fluoride and a compound having a carboxyl group or a carboxylic anhydride group, the weight ratio of the hydrogen: the compound having a carboxyl group or a carboxylic anhydride group = 1: 400 to 70: 1. Preferably, the ratio is 1: 200 to 2: 1, more preferably 1:50 to 1: 1.

When water is added to the electrolytic solution in order to indirectly generate hydrogen fluoride, 0.00045 to 0.315% by weight of water is added to the total amount of the nonaqueous solvent and the electrolyte. And more preferably 0.00
45 to 0.135% by weight, more preferably 0.009%
０．０0.09% by weight. When the electrolyte is LiPF6, the added water changes almost quantitatively to hydrogen fluoride in three days.

Non-Aqueous Solvent In the non-aqueous electrolyte according to the present invention, an organic solvent is preferable as the non-aqueous solvent, and particularly, the following general formulas (1a) and (1)
It is desirable to use a non-aqueous solvent containing at least one cyclic carbonate and / or chain carbonate selected from the compounds represented by b).

Examples of the non-aqueous solvent that can be used include at least one cyclic carbonate and / or chain carbonate selected from the compounds represented by the following general formulas (1a) and (1b). it can.

Embedded image (In the formula, R ^{1 to} R ⁴ may be the same or different from each other and are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.) In the above, the alkyl group has 1 carbon atom. Preferred are alkyl groups 3 to 3, specifically, a methyl group, an ethyl group, and an n-propyl group.

Specific examples of the cyclic carbonate represented by the general formula (1a) or (1b) include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate,
Examples thereof include 2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. In particular, ethylene carbonate and propylene carbonate having a high dielectric constant are preferably used. When the improvement of the battery life is particularly intended, ethylene carbonate is particularly preferable. These cyclic carbonates may be used as a mixture of two or more kinds.

Specific examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate and the like. In particular, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate having low viscosity are preferably used. These chain carbonates may be used as a mixture of two or more.

Specific examples of the combination of the cyclic carbonate and the chain carbonate of the non-aqueous solvent include ethylene carbonate and dimethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, and propylene carbonate. And methyl ethyl carbonate, propylene carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate, ethylene carbonate and propylene carbonate and methyl ethyl carbonate,
Ethylene carbonate and propylene carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate Diethyl carbonate and the like.

When such a chain carbonate is contained in the non-aqueous solvent, the viscosity of the non-aqueous electrolyte can be reduced, the solubility of the electrolyte can be further increased, and the electric conductivity at normal temperature or low temperature can be improved. It is possible to obtain an electrolytic solution having excellent properties.
Therefore, the load characteristics of the battery can be improved.

In a non-aqueous solvent, the compound represented by the general formula (1a)
And at least one cyclic carbonate selected from the compounds represented by (1b) and / or at least one cyclic carbonate selected from the compounds represented by the chain carbonates (1a) and (1b) And the mixing ratio of the chain carbonate with the above-mentioned general formula (1)
at least one cyclic carbonate selected from the compounds represented by a) and (1b):
0: 100 to 100: 0, preferably 5:95 to 80:
20, more preferably from 10:90 to 70:30, particularly preferably from 15:85 to 55:45. With such a ratio, the increase in the viscosity of the electrolytic solution is suppressed,
Since the degree of dissociation of the electrolyte can be increased, the conductivity of the electrolyte relating to the charge / discharge characteristics of the battery can be increased.

Therefore, preferred non-aqueous solvents according to the present invention are at least one cyclic carbonate selected from the compounds represented by formulas (1a) and (1b) and / or the chain carbonate. Including. In addition to these, it is also possible to further mix or add a small amount of a solvent which is widely used as a non-aqueous solvent for batteries.

Specific examples of such a solvent include chains such as methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl butyrate, and methyl valerate. Ester; phosphate ester such as trimethyl phosphate; 1,2-
Chain ethers such as dimethoxyethane, 1,2-diethoxyethane, diethyl ether, dimethyl ether, methyl ethyl ether and dipropyl ether; 1,4-dioxane, 1,3-dioxolan, tetrahydrofuran, 2-methyltetrahydrofuran, Methyl-1,3-dioxolan, 2-
Cyclic ethers such as methyl-1,3-dioxolane; amides such as dimethylformamide; linear carbamates such as methyl-N, N-dimethylcarbamate; γ-butyrolactone, γ-valerolactone, 3-methyl-γ-butyrolactone, 2 Cyclic esters such as -methyl-γ-butyrolactone;
Cyclic sulfones such as sulfolane; cyclic carbamates such as N-methyloxazolidinone; cyclic amides such as N-methylpyrrolidone; cyclic ureas such as N, N-dimethylimidazolidinone; 4,4-dimethyl-5-methyleneethylene carbonate; -Methyl-4-ethyl-5-methyleneethylene carbonate, 4-methyl-4-propyl-5-methyleneethylene carbonate, 4-methyl-4-butyl-5-methyleneethylene carbonate, 4,4-diethyl-5-methylene Ethylene carbonate, 4-ethyl-4-propyl-5-methyleneethylene carbonate, 4-ethyl-4-butyl-5-methyleneethylene carbonate, 4,4-dipropyl-5-methyleneethylene carbonate, 4-propyl-4-butyl -5-methylene ethylene carbonate, 4,4-dibutyl-5-methylene ethylene carbonate, 4,4-dimethyl-5-ethylidene ethylene carbonate , 4-methyl-4-ethyl-5-ethylidene ethylene carbonate, 4-methyl-4-propyl-5-ethylidene ethylene carbonate, 4-methyl-4-butyl-5-ethylidene ethylene carbonate, 4,4-diethyl-5 -Ethylidene ethylene carbonate, 4-ethyl-4-propyl-5-ethylidene ethylene carbonate, 4-ethyl-4-butyl-5-ethylidene ethylene carbonate, 4,4-dipropyl-5-ethylidene ethylene carbonate, 4-propyl-4 -Butyl-5-ethylidene ethylene carbonate, 4,4-dibutyl-5-ethylidene ethylene carbonate, 4-methyl-4-vinyl-5-methyleneethylene carbonate, 4-methyl-4-allyl-5-methyleneethylene carbonate, 4 -Methyl-4-methoxymethyl-5-
Cyclic carbonates such as methyleneethylene carbonate, 4-methyl-4-acryloxymethyl-5-methyleneethylene carbonate, 4-methyl-4-allyloxymethyl-5-methyleneethylene carbonate; 4-vinylethylene carbonate, 4,4 -Vinylethylene carbonate derivatives such as -divinylethylene carbonate and 4,5-divinylethylene carbonate; 4-vinyl-4-methylethylene carbonate, 4-vinyl-5-methylethylene carbonate, 4-vinyl-4,5-dimethylethylene carbonate , 4-vinyl-5,
Alkyl-substituted vinylethylene carbonate derivatives such as 5-dimethylethylene carbonate and 4-vinyl-4,5,5-trimethylethylene carbonate; allyloxymethyl such as 4-allyloxymethylethylene carbonate and 4,5-diallyloxymethylethylene carbonate Ethylene carbonate derivatives; alkyl-substituted allyloxymethylethylene carbonate derivatives such as 4-methyl-4-allyloxymethylethylene carbonate and 4-methyl-5-allyloxymethylethylene carbonate; 4-acryloxymethylethylene carbonate, 4,5- Acryloxymethylethylene carbonate derivatives such as acryloxymethylethylene carbonate; 4-methyl-4-acryloxymethylethylene carbonate, 4-methyl-5-acryloxymethylethylene carbonate, etc. Alkyl-substituted acryloxymethyl ethylene carbonate derivatives; sulfur-containing compounds such as sulfolane and dimethyl sulfate;
Phosphorus-containing compounds such as trimethylphosphoric acid and triethylphosphoric acid; and compounds represented by the following general formula. HO (CH ₂ CH ₂ O) _a H, HO ｛CH ₂
CH (CH ₃ ) O｝ _b H, CH ₃ O (CH ₂ CH ₂ O) _c H,
CH ₃ O ｛CH ₂ CH (CH ₃ ) O｝ _d H, CH ₃ O (CH ₂
CH ₂ O) _e CH ₃ , CH ₃ O {CH ₂ CH (CH ₃ ) O} _f
CH ₃ , C ₉ H ₁₉ PhO (CH ₂ CH ₂ O) _g ｛CH (CH
₃ ) O｝ _h CH ₃ (Ph is a phenyl group), CH ₃ O ｛CH ₂
CH (CH ₃ ) O｝ _i CO ｛O (CH ₃ ) CHCH ₂ ｝ _j O
CH ₃ (where a to f are integers of 5 to 250, g to j
Is an integer of 2 to 249, 5 ≦ g + h ≦ 250, 5 ≦ i + j
≦ 250. )

In particular, for the purpose of increasing the flash point of the solvent,
The solvent is preferably a combination of the cyclic carbonate represented by the general formulas (1a) and (1b) and a solvent having a high boiling point. Examples of the high boiling point solvent include γ-butyrolactone, sulfolane, and trialkyl phosphate.

Non-Aqueous Electrolyte The non-aqueous electrolyte of the present invention comprises a non-aqueous solvent and an electrolyte, and further contains the above-mentioned hydrogen fluoride and a compound having a carboxyl group or a carboxylic anhydride group. Is what you do. As the electrolyte to be used, any electrolyte which is usually used as an electrolyte for a non-aqueous electrolyte can be used.

As a specific example of the electrolyte, LiPF₆, Li
BF_Four, LiClO_Four, LiAsF₆, Li _TwoSiF₆, LiC_FourF
₉SO_Three, LiC₈F₁₇SO_ThreeLithium salts such as
You. In addition, a lithium salt represented by the following general formula is also used.
be able to. LiOSO_TwoR₈, Lin (SO_TwoR₉) (S
O_TwoR_Ten), LiC (SO_TwoR₁₁) (SO_TwoR₁₂) (SO_Two
R₁₃), LiN (SO_TwoOR₁₄) (SO_TwoOR_Fifteen)(here
And R⁸~ R^FifteenAre the same but different
And a perfluoroalkyl group having 1 to 6 carbon atoms.
). These lithium salts may be used alone or
Or two or more of them may be used in combination.

Among these, in particular, LiPF ₆ , LiB
F ₄ , LiOSO ₂ R ₈ , LiN (SO ₂ R ₉ ) (SO
_{2 R 10), LiC (SO} 2 R 11) (SO 2 R 12) (SO 2 R
₁₃ ), and LiN (SO ₂ OR ₁₄ ) (SO ₂ OR ₁₅ ) are preferred.

It is desirable that such an electrolyte is usually contained in the non-aqueous electrolyte at a concentration of 0.1 to 3 mol / l, preferably 0.5 to 2 mol / l.

The non-aqueous electrolyte in the present invention contains hydrogen fluoride, a compound having a carboxyl group or a carboxylic anhydride group, a non-aqueous solvent, and an electrolyte as essential components.
Other additives and the like may be added as necessary.

The non-aqueous electrolyte according to the present invention as described above
Not only is it suitable as a non-aqueous electrolyte for lithium ion secondary batteries, but it can also be used as a non-aqueous electrolyte for primary batteries.

Secondary Battery The non-aqueous electrolyte secondary battery according to the present invention comprises a negative electrode, a positive electrode,
The non-aqueous electrolyte is basically configured to include,
Usually, a separator is provided between the negative electrode and the positive electrode.

The negative electrode active material constituting the negative electrode includes metallic lithium, a lithium alloy, a carbon material capable of doping and undoping lithium ions, tin oxide capable of doping and undoping lithium ions, and oxides Niobium, vanadium oxide, titanium oxide capable of doping and undoping lithium ions, silicon capable of doping and undoping lithium ions, transition metal nitrogen capable of doping and undoping lithium ions Any of the compounds can be used. Among these, a carbon material capable of doving / de-doping lithium ions is preferable. Such a carbon material may be graphite or amorphous carbon, and activated carbon, carbon fiber, carbon black, mesocarbon microbeads, natural graphite and the like are used.

As the negative electrode active material, the spacing (d002) of the (002) plane measured by X-ray analysis was 0.340 nm.
The following carbon materials are preferable, and the density is 1.70 g / cm ³
The graphite described above or a highly crystalline carbon material having properties similar thereto is desirable. When such a carbon material is used, the energy density of the battery can be increased.

As the positive electrode active material constituting the positive electrode, Mo is used.
Transition metal oxides or sulfides such as S ₂ , TiS ₂ , MnO ₂ , V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ , LiMn ₂
Conductive oxides such as O ₄ , LiNiO ₂ , LiNi _X Co _(1-X) O ₂ , and complex oxides composed of lithium and transition metals, polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole / polyaniline composites Polymer materials and the like can be mentioned. Among these, a composite oxide composed of lithium and a transition metal is particularly preferable. When the negative electrode is a lithium metal or lithium alloy, a carbon material can be used as the positive electrode.
Further, as the positive electrode, a mixture of a composite oxide of lithium and a transition metal and a carbon material can be used.

The separator is a porous membrane, and usually a microporous polymer film is suitably used. In particular, a porous polyolefin film is preferable, and specific examples thereof include a porous polyethylene film, a porous polypropylene film, and a multilayer film of a porous polyethylene film and polypropylene.

Such a non-aqueous electrolyte secondary battery can be formed in a cylindrical shape, a coin shape, a square shape, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be changed according to the purpose. Next, the structures of the cylindrical and coin type batteries will be described. The negative electrode active material, the positive electrode active material, and the separator constituting each battery are commonly used.

For example, in the case of a cylindrical non-aqueous electrolyte secondary battery, a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector,
A positive electrode obtained by applying a positive electrode active material to a positive electrode current collector is wound through a separator into which a non-aqueous electrolyte is injected, and is housed in a battery can with an insulating plate placed above and below the wound body. ing.

As a representative example, the structure of a cylindrical nonaqueous electrolyte secondary battery will be described with reference to FIG. In FIG. 1, the negative electrode current collector 9
A negative electrode 1 obtained by applying a negative electrode active material to a negative electrode, and a positive electrode current collector 10
A positive electrode 2 coated with a positive electrode active material is wound around a separator 3 into which a non-aqueous electrolytic solution has been injected, and an insulating plate 4 is placed above and below the wound body to form a battery can 5. It is stored. A battery lid 7 is provided with a sealed gasket 6 in the battery can 5.
And are electrically connected to the negative electrode 1 or the positive electrode 2 via the negative electrode lead 11 and the positive electrode lead 12, respectively, and function as a negative electrode or a positive electrode of the battery.

In this battery, the positive electrode lead 12 is electrically connected to the battery cover 7 via the current interrupting thin plate 8. When the pressure inside the battery rises, the current interrupting thin plate 8
Is pushed up and deformed, and the positive electrode lead 12
It is cut off leaving a welded part, and the current is cut off.

The non-aqueous electrolyte secondary battery according to the present invention can be applied to a coin-type non-aqueous electrolyte secondary battery. In a coin-type battery, a disc-shaped negative electrode, a separator, a disc-shaped positive electrode, and a stainless steel or aluminum plate are housed in a coin-shaped battery can in a state of being stacked in this order.

The non-aqueous electrolyte secondary battery of the present invention can be obtained by injecting the electrolytic solution of the present invention into the battery having the above-mentioned structure.
In practicing the present invention, the components of the electrolytic solution, for example, a compound having a carboxyl group or a carboxylic anhydride group are previously contained in the battery, and the electrolytic solution not containing the components is injected in advance. It is also possible to adopt a method in which the contained constituents are dissolved in the electrolytic solution, and as a result, the nonaqueous electrolytic solution of the present invention is composed.

In this case, examples of the battery member containing the additive include a negative electrode, a positive electrode, a separator, and a binder, and it is desirable that the additive be contained as uniformly as possible on the electrode surface. In the case of a compound having a carboxyl group or a carboxylic anhydride group, the concentration to be contained is desirably 0.01 to 4% by weight based on the amount of the electrolyte to be injected later.

For hydrogen fluoride, the electrolyte is L
In the case of a fluorine-containing electrolyte such as iPF ₆ or LiBF ₄ , it can be substantially added to the battery in advance by the following method. After water is contained in the battery and the electrolyte is injected, the water in the battery dissolves in the electrolyte and reacts with the electrolyte to generate hydrogen fluoride. In this case, the amount of water contained in the battery is desirably 0.0045 to 0.36% by weight.

[0068]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0069]

[Example] (Example 1). Preparation of Battery < Preparation of Non-Aqueous Electrolyte> Ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed with EC: MEC
= 4: 6 (weight ratio) was used as a non-aqueous solvent, and then LiPF ₆ as an electrolyte was dissolved in the non-aqueous solvent to prepare an electrolyte having a concentration of 1.0 mol / l. did. In the electrolytic solution, 0.2% by weight of tricarboxyethyl isocyanurate based on the total amount of the nonaqueous solvent and the electrolyte was added. Subsequently, a predetermined amount of water was added to the electrolytic solution, and hydrogen fluoride was added by generating hydrogen fluoride at a ratio shown in Table 1 with respect to the total amount of the nonaqueous solvent and the electrolyte in the electrolytic solution. . The determination of hydrogen fluoride was performed by titration with alkali three days after the addition of water.

<Preparation of Negative Electrode> Natural graphite (LF made of Chuetsu graphite)
-18A) 87 parts by weight and 13 parts by weight of polyvinylidene fluoride (PVDF) as a binder were mixed and dispersed in N-methylpyrrolidinone as a solvent to prepare a natural graphite mixture slurry. Next, this negative electrode mixture slurry was applied to a 18-μm-thick negative electrode current collector made of strip-shaped copper foil, dried, compression-molded, and punched out into a 14 mm disk shape to form a coin-shaped natural graphite. An electrode was obtained. The thickness of this natural graphite electrode mixture is 1
10 μm, weight was 20 mg / Φ14 mm.

<Preparation of LiCoO ₂ Electrode>
₂ (HLC-2 manufactured by Honjo FMC Energy Systems Co., Ltd.)
1) 90 parts by weight, 6 parts by weight of graphite as a conductive agent, 1 part by weight of acetylene black, and polyvinylidene fluoride 3 as a binder
Parts by weight were mixed and dispersed in N-methylpyrrolidone as a solvent to prepare a LiCoO ₂ mixture slurry. This LiC
The oO ₂ mixture slurry was applied to a 20-μm-thick aluminum foil, dried, compression-molded, and cut into a diameter of 13 mm to produce a LiCoO ₂ electrode. This LiCoO ₂ mixture had a thickness of 90 μm and a weight of 35 mg / Φ13 mm.

<Production of Battery> A coin-type battery shown in FIG. 2 was produced. 14 mm diameter natural graphite electrode (negative electrode) 1
3, a LiCoO ₂ electrode (positive electrode) 13 having a diameter of 13 mm, a separator 15 made of a microporous polypropylene film having a thickness of 25 μm and a diameter of 16 mm, and a stainless steel 2
The natural graphite electrode 13, the separator 3, and the LiCoO ₂ electrode 14 were stacked in the order of 032 size battery can 16. Then, 0.03 ml of the non-aqueous electrolyte was added to the separator.
And an aluminum plate 17 (1.2 mm thick,
16 mm in diameter) and the spring 20 were housed. Finally,
By caulking the battery can lid 19 via the polypropylene gasket 18, airtightness in the battery is maintained,
A coin-type battery having a diameter of 20 mm and a height of 3.2 mm was manufactured.

2. Evaluation of Battery Characteristics Using the coin battery prepared as described above, this battery was used under the condition of 0.5 mA constant current and 4.2 V constant voltage until the current value at 4.2 V constant voltage became 0.05 mA. Charge, and then 3.0 V under the condition of 1 mA constant current and 3.0 V constant voltage.
It discharged until the current value at the time of a constant voltage became 0.05 mA. Next, under the condition of 1 mA constant current and 3.85 V constant voltage, the current value at the time of 3.85 V constant voltage was 0.05 mA.
It was charged until it became.

Thereafter, the battery was placed in a thermostat at 60 ° C. for 2 hours.
High-temperature storage was performed for 4 hours. After preservation at a high temperature, the termination condition was set to a constant current / constant voltage of 0.0 mA at a constant current / constant voltage of 1 mA.
The charge / discharge of 4.2 V to 3.0 V was performed once at 5 mA, and the discharge capacity was measured. This is referred to as “low load discharge capacity”.

Next, the battery was charged to 4.2 V under the same conditions, and then discharged at a constant current of 10 mA and the discharge was terminated when the battery voltage reached 3.0 V, and the discharge capacity was measured. This is referred to as “high load discharge capacity”.

Then, the ratio of the high-load discharge capacity to the low-load discharge capacity at this time was determined and defined as a “load characteristic index”.

After the high-temperature storage test, the resistance of the battery was determined from the change in the battery voltage two minutes after the start of discharging. After recharging the battery to 4.2 V and measuring the charging capacity,
After storage at 7 ° C. for 7 days, the battery was discharged to 3.0 V and the remaining capacity was measured. At this time, the ratio of the remaining capacity to the charged capacity was determined as an index indicating the self-discharge property of the battery. This was named "survival rate". Table 1 shows the results of the evaluation in this example.

(Comparative Examples 1 to 5) Experiments were carried out in the same manner as in Examples 1 to 5, except that the use of tricarboxyethyl isocyanurate was omitted. Table 1 shows the results of the evaluation.

[0079]

[Table 1]

Examples 6 to 13 Experiments were carried out in the same manner as in Example 1 except that the preparation of the nonaqueous electrolyte was carried out under the following conditions. The results are shown in Table 2. <Preparation of non-aqueous electrolyte> Ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed with EC: MEC
= 4: 6 (weight ratio) was used as a non-aqueous solvent, and then LiPF ₆ as an electrolyte was dissolved in the non-aqueous solvent to prepare an electrolyte having a concentration of 1.0 mol / l. did. Next, a compound having a carboxyl group shown in Table 2 was added to this solution so as to have a ratio (% by weight) shown in Table 2 with respect to the total amount of the nonaqueous solvent and the electrolyte. Subsequently, a predetermined amount of water was added to the electrolytic solution, and hydrogen fluoride was added by generating hydrogen fluoride in the electrolytic solution at a ratio shown in Table 2 with respect to the total amount of the nonaqueous solvent and the electrolyte. The determination of hydrogen fluoride was performed by titration with alkali three days after the addition of water.

Comparative Example 6 An experiment was conducted in the same manner as in Example 6, except that the use of maleic acid was omitted.
The results are shown in Table 2.

[0082]

[Table 2]

(Examples 14 to 19) An experiment was conducted in the same manner as in Example 1 except that the preparation of the nonaqueous electrolyte was performed under the following conditions. The results are shown in Table 2. <Preparation of non-aqueous electrolyte> Ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed with EC: MEC
= 4: 6 (weight ratio) was used as a non-aqueous solvent, and then LiPF ₆ as an electrolyte was dissolved in the non-aqueous solvent to prepare an electrolyte having a concentration of 1.0 mol / l. did. Next, a compound having a carboxylic anhydride group shown in Table 3 was added to this solution so as to have a ratio (% by weight) shown in Table 3 with respect to the total amount of the nonaqueous solvent and the electrolyte.
Subsequently, a predetermined amount of water was added to the electrolyte, and hydrogen fluoride was added by generating hydrogen fluoride in the electrolyte at a ratio shown in Table 3 with respect to the total of the nonaqueous solvent and the electrolyte. The determination of hydrogen fluoride was performed by titration with alkali three days after the addition of water.

[0084]

[Table 3]

(Examples 20 and 21) <Preparation of non-aqueous electrolyte> Ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed with EC: MEC.
= 4: 6 (weight ratio) was used as a non-aqueous solvent, and LiPF ₆ as an electrolyte was dissolved in the non-aqueous solvent to prepare an electrolyte having a concentration of 1.0 mol / liter. did. Subsequently, a predetermined amount of water is added to the electrolytic solution, and hydrogen fluoride is added in the electrolytic solution by generating hydrogen fluoride in a ratio (% by weight) shown in Table 4 with respect to the total amount of the nonaqueous solvent and the electrolyte. Was performed. The determination of hydrogen fluoride was performed by titration with alkali three days after the addition of water. <Preparation of Negative Electrode> Natural Graphite (LF-18A made by Chuetsu Graphite) 8
6.5 parts by weight of polyvinylidene fluoride (PVD) as a binder
F) 12.9 parts by weight of maleic acid and 0.6 part by weight of maleic acid were mixed and dispersed in N-methylpyrrolidinone as a solvent to prepare a natural graphite mixture slurry. Next, this negative electrode mixture slurry was applied to a negative electrode current collector made of a strip-shaped copper foil having a thickness of 18 μm,
After being dried, it was compression molded and punched out into a 14 mm disc to obtain a coin-shaped natural graphite electrode. This natural graphite electrode mixture has a thickness of 110 μm and a weight of 20 mg / Φ.
14 mm.

<Preparation of Battery> A battery was prepared in the same manner as in Example 1 using the above-mentioned electrolyte and negative electrode. At this time, the ratio of the compound having a carboxyl group contained in the negative electrode to the injected electrolyte was 0.2% by weight.

Example 1 of the battery manufactured as described above
The battery characteristics were evaluated in the same manner as described above. The results are shown in Table 4.

(Comparative Examples 7 and 8) Examples 20 and 2
1, an experiment was conducted in the same manner except that the use of maleic acid in the production of the negative electrode was omitted. The results are shown in Table 4.

[0089]

[Table 4]

[0090]

EFFECTS OF THE INVENTION By using the non-aqueous electrolyte of the present invention, a non-aqueous electrolyte secondary having improved load characteristics, battery resistance and remaining rate after a life test (such as high-temperature storage and cycle test) has been performed. You can get a battery. This non-aqueous electrolyte is particularly suitable as an electrolyte for a lithium ion secondary battery.
The present invention provides a secondary battery having excellent performance using the above non-aqueous electrolyte. In particular, it provides a lithium ion secondary battery having excellent performance using the above non-aqueous electrolyte.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cylindrical secondary battery to which a non-aqueous electrolyte according to the present invention is applied.

FIG. 2 is a cross-sectional view of a coin-type secondary battery to which the non-aqueous electrolyte according to the present invention is applied.

[Explanation of symbols]

 1, 13 ... negative electrode 2, 14 ... positive electrode 3, 15 ... separator 4 ... insulating plate 5, 16 ... battery can 6, 18 gasket 7 19 battery lid 8 current-cut thin plate 9 negative electrode current collector 10・ Positive electrode collector 11 ・ ・ ・ ・ ・ ・ Anode lead 12 ・ ・ ・ ・ ・ ・ Positive electrode lead 17 ・ ・ ・ ・ ・ ・ Aluminum plate 20 ・ ・ ・ ・ ・ ・ Spring

Claims (9)

[Claims] 1. A non-aqueous solvent, an electrolyte, 0.0005 to 0.7% by weight of hydrogen fluoride with respect to the total amount of the non-aqueous solvent and the electrolyte, and a 0.1% by weight of the non-aqueous solvent and the electrolyte. 01 ~
A non-aqueous electrolyte containing 4.0% by weight of a compound having a carboxyl group or a carboxylic anhydride group. 2. The compound having a carboxyl group or a carboxylic anhydride group having 4 to 20 carbon atoms and having 2 in the molecule.
The non-aqueous electrolytic solution according to claim 1, wherein the compound has at least one carboxyl group or at least one carboxylic anhydride group and has a carbon-carbon unsaturated group. 3. The method according to claim 1, wherein the non-aqueous solvent is at least one selected from compounds represented by the following general formulas (1a) and (1b).
The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte is a cyclic carbonate and / or a chain carbonate. Embedded image (In the formula, R ^{1 to} R ⁴ may be the same or different from each other, and are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.) 4. The non-aqueous electrolyte according to claim 3, wherein said cyclic carbonate is at least one compound selected from ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate. 5. The non-aqueous electrolyte according to claim 3, wherein the chain carbonate is at least one compound selected from dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate. 6. The non-aqueous solution according to claim 3, wherein the weight ratio of the cyclic carbonate to the chain carbonate in the non-aqueous solvent is 15:85 to 55:45. Electrolyte. 7. A secondary battery comprising the non-aqueous electrolyte according to claim 1. 8. A carbon material capable of doping and undoping lithium metal, a lithium-containing alloy, or lithium ions.
Tin oxide, capable of doping and undoping lithium ions,
Selected from titanium oxide, niobium oxide, vanadium oxide, capable of doping and undoping lithium ions, transition metal nitride capable of doping and undoping lithium ions, and silicon capable of doping and undoping lithium ions A negative electrode including at least one negative electrode active material, including at least one positive electrode active material selected from a transition metal oxide, a transition metal sulfide, a composite oxide of lithium and a transition metal, a conductive polymer material, and a carbon material A positive electrode;
A secondary battery comprising the non-aqueous electrolyte according to any one of claims 1 to 6. 9. The method according to claim 9, wherein the negative electrode active material is lithium ion-doped.
9. The lithium ion secondary battery according to claim 8, wherein the lithium ion secondary battery is a undoped carbon material.