JP2002329528A - Nonaqueous electrolyte, secondary battery using it and additive for electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte capable of restraining a decomposition reaction of a solvent on a negative electrode, capacity drop of a battery during high-temperature storage, generation of gas and degradation of a load characteristic of the battery, to provide a nonaqueous electrolyte capable of providing excellent load characteristic and low-temperature characteristic for a battery, to provide a secondary battery including the nonaqueous electrolyte and to provide an additive for an electrolyte. SOLUTION: This nonaqueous electrolyte contains an unsaturated sultone. This secondary battery uses the nonaqueous electrolyte. This additive for an electrolyte comprises a compound which is a preferable example for the unsaturated sultone and expressed by Formula (1) where R<1> -R<4> are each hydrogen, fluorine or a 1-12C hydrocarbon group that may contain fluorine, and (n) is an integer of 0 to 3.

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 life characteristics, a secondary battery using the same, and an additive for the electrolyte. Further, the present invention relates to a non-aqueous electrolyte having excellent life characteristics, a high flash point, and excellent safety, a secondary battery using the same, and an electrolyte additive. More specifically,
The present invention relates to a non-aqueous electrolyte suitable for a lithium secondary battery containing unsaturated sultone, a secondary battery using the same, and an additive for an electrolyte.

[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.

[0003] As such a battery, there is a non-aqueous electrolyte secondary battery, a typical example of which is a lithium battery. As an electrolytic solution used for this, LiBF is added to an aprotic organic solvent.
₄ , LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiC
A solution in which a Li electrolyte such as F ₃ SO ₃ and Li ₂ SiF ₆ is mixed is used (edited by Jean-Paul Gabano, “Lithi
um Battery ", ACADEMIC PRESS (1983)).

[0004] As representatives of aprotic organic solvents, carbonates are known, and the use of various carbonate compounds such as ethylene carbonate, propylene carbonate, dimethyl carbonate and the like has been proposed (JP-A-4-184872, JP-A-4-184872). No. 10-27625). Many other sulfur-based solvents have been proposed as other aprotic solvents that can be used. For example, cyclic sulfones (JP-A-57-187878, JP-A-61-164)
No. 78), chain sulfones (JP-A-3-152879,
JP-A-8-241732, sulfoxides (JP-A-57-141878, JP-A-61-16478, etc.), sultones (JP-A-63-102173), and sulfites (JP-A-61-172173). No. 64080) and the like. In addition, esters (Japanese Patent Laid-Open No.
No. 769, JP-A-4-284374), use of aromatic compounds (JP-A-4-249870) and the like have also been proposed.

One of the mainstream lithium secondary batteries at present is a lithium ion secondary battery. This battery includes a negative electrode made of an active material capable of inserting and extracting lithium, a positive electrode made of a composite oxide of lithium and a transition metal, an electrolyte, and the like.

As a negative electrode active material of a lithium ion secondary battery, a carbon material capable of occluding and releasing lithium is often used. In particular, highly crystalline carbon such as graphite has a flat discharge potential and a true discharge potential. It has features such as high density and good filling properties, and has been adopted as most negative electrode active materials of currently marketed lithium ion secondary batteries.

[0007] In addition, a mixed solvent of a high dielectric constant carbonate solvent such as propylene carbonate and ethylene carbonate and a low viscosity carbonate solvent such as diethyl carbonate, methyl ethyl carbonate and dimethyl carbonate is used in the electrolyte solution, and LiBF ₄ , LiPF ₆ , LiN
(SO ₂ CF ₃ ) ₂ and LiN (SO ₂ CF ₂ CF ₃ ) ₂
For example, a solution in which a Li electrolyte is mixed is used.

However, when highly crystalline carbon such as graphite is used for the negative electrode, it is necessary to suppress the problem that a reductive decomposition reaction of the electrolytic solution occurs on the graphite negative electrode. For example, propylene carbonate or 1,1,
In the electrolyte using 2-butylene carbonate, the reductive decomposition reaction of the solvent occurs violently while exfoliation of the graphite edge surface occurs at the time of the first charge, and the insertion reaction of lithium ion, an active material, into the graphite proceeds. It becomes difficult to do. As a result, it is known that the initial charge / discharge efficiency decreases and the energy density of the battery decreases (J. Electroc.
hem. Soc., 146 (5) 1664-1671 (1999)).

[0009] As an attempt to solve this problem, as a non-aqueous solvent having a high dielectric constant used in an electrolytic solution, ethylene carbonate which is solid at ordinary temperature but hardly undergoes reductive decomposition reaction continuously is used. A proposal to use a mixed solvent of carbonate and propylene carbonate is known (J. Electrochem. Soc., 146 (5) 1664-1671 (1.
999)). Also, even if ethylene carbonate is used,
It is known that a reductive decomposition reaction of a small amount of electrolyte continuously occurs on the negative electrode surface (J. Electrochem. Soc., 147 (10) 36).
28-3632 (2000), J. Electrochem. Soc., 146 (11) 4014-4018
(1999), J. Power Sources 81-82 (1999) 8-12) For example, the battery capacity decreases when the battery is cycled repeatedly for a long time and stored at high temperature. Can be considered.

[0010] Therefore, as an attempt to further suppress the reductive decomposition reaction of the solvent on the negative electrode, many reports have been made on adding a compound that suppresses the reductive decomposition of the electrolytic solution to the electrolytic solution.

For example, by incorporating vinylene carbonate, the storage characteristics and cycle characteristics of the battery are improved (Japanese Patent Application Laid-Open Nos. 5-13088 and 6-528).
No. 87, JP-A-7-122296, JP-A-9-347
778) that propylene carbonate undergoing reductive decomposition at the edge surface of the graphite anode can be used (10th International Conference on Lithium Batteries, Abstract No. 286, Japanese Patent Application No. 10-15)
No. 0420).

As another example, it has been reported that sulfur acids are added. For example, ethylene sulfate (J. Electrochem. Soc. 146 (2) 470-472 (1999), No. 10
Lithium Battery International Conference, Abstract No. 289, JP-A-11
No. 73990) and SO ₃ (J. Electrochem. Soc., 143, L
195 (1996)) makes it possible to use propylene carbonate in a graphite negative electrode, and to use sultones (JP-A-11-162).
No. 511, JP-A-11-339850, JP-A-2000
-3724, JP-A-2000-3725, JP-A-200
0-123868, JP-A-2000-77098),
Sulfonic esters (JP-A-9-245834, JP-A-10-189041, JP-A-2000-13330)
No. 4) has been proposed as an additive for improving cycle characteristics.

Further, vinylene carbonate has a structure in which a carbon-carbon unsaturated bond is introduced into ethylene carbonate, which is a general solvent for a graphite negative electrode. Many attempts have been made to include an unsaturated bond to have an improving effect.

For example, a cyclic carbonate having a vinyl group (JP-A-2000-40526), an acid anhydride containing a double bond (JP-A-7-122297), and a sulfone containing a double bond (Japanese Patent Laid-Open No. -329494, JP-A-2000-294278), esters, benzenes and sulfones having a triple bond introduced therein (JP-A-2000-1).
95545) and esters containing a double bond (JP-A-11-273725, JP-A-11-2737).
No. 24, JP-A-11-273723, JP-A-2000-
No. 182666).

Although these carbon-carbon-unsaturated-additives have a certain effect by allowing propylene carbonate to be used in a graphite negative electrode, improvement in high-temperature storage characteristics and cycle characteristics is not achieved by vinylene. It has not yet achieved the same or better effects as carbonate.

For example, in the study of the present inventor, it has been found that the above-mentioned electrolytic solution to which a sulfur-based compound containing a carbon-carbon unsaturated bond is added, in particular, when the battery is stored at a high temperature, self-discharge accompanying the electrolysis rather occurs. The desired effect has not been realized.

As described above, various electrolytic solutions have been studied. However, no satisfactory electrolytic solution including vinylene carbonate has been obtained, and the electrolytic solution that occurs when the high-temperature storage and charge / discharge cycles are repeated is not obtained. There is a need for an electrolyte solution that further suppresses the reductive decomposition reaction of the solution and further improves the deterioration of the load characteristics of the battery and the decrease in the battery capacity.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and have reached the present invention. According to the present invention, it is possible to obtain a battery in which reductive decomposition of an electrolytic solution during high-temperature storage is greatly suppressed, and as a result, self-discharge is small, load characteristics and resistance deterioration are largely suppressed, and gas generation in the battery is small. I found that I can do it.

[0019]

SUMMARY OF THE INVENTION In order to meet the above demand, the present invention suppresses the decomposition reaction of a solvent on a negative electrode,
It is an object of the present invention to provide a non-aqueous electrolyte in which the capacity of a battery is reduced, generation of gas is suppressed, and deterioration of load characteristics of the battery is suppressed even when stored at high temperatures. Another object of the present invention is to provide a non-aqueous electrolyte having excellent life characteristics, a high flash point and excellent safety. It is another object of the present invention to provide a non-aqueous electrolyte which gives a battery excellent load characteristics and low-temperature characteristics. The present invention
It is an object to provide a secondary battery containing this non-aqueous electrolyte. It is a further object of the present invention to provide an additive for an electrolytic solution that imparts such a function to the electrolytic solution.

[0020]

The present invention provides a non-aqueous electrolyte containing unsaturated sultone. A non-aqueous electrolyte in which the unsaturated sultone is a compound represented by the following general formula (1) is a preferred embodiment of the present invention.

Embedded image Here, R ^{1 to} R ⁴ are hydrogen, fluorine, or carbon 1
A hydrocarbon group which may contain from 12 to 12 fluorine atoms, and n is an integer from 0 to 3.

The present invention provides a non-aqueous electrolyte containing the unsaturated sultone, a non-aqueous solvent and an electrolyte.

The non-aqueous electrolyte in which the non-aqueous solvent is a cyclic aprotic solvent and / or a chain aprotic solvent is
This is a preferred embodiment of the present invention.

The non-aqueous electrolyte in which the non-aqueous solvent is γ-butyrolactone or a mixture of γ-butyrolactone and at least one selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, sulfolane and methyl sulfolane is This is a preferred embodiment of the present invention.

A non-aqueous electrolyte further containing a vinylene carbonate derivative represented by the following general formula (3) is a preferred embodiment of the present invention.

Embedded image (R ⁵ and R ⁶ are hydrogen, a methyl group, an ethyl group, or a propyl group.)

The above non-aqueous electrolyte in which the electrolyte is a lithium salt is a preferred embodiment of the present invention.

The present invention also relates to an unsaturated sultone and γ
- providing a non-aqueous solvent containing butyrolactone, the non-aqueous electrolyte containing an electrolyte containing LiPF _6.

Further, the present invention provides a negative electrode active material comprising metallic lithium, a lithium-containing alloy, a metal or alloy capable of being alloyed with lithium, an oxide capable of doping / dedoping lithium ions, and a lithium ion doping / doping. A negative electrode including at least one selected from a undoped transition metal nitride, a carbon material capable of doping / dedoping lithium ions, or a mixture thereof, and a transition metal oxide or a transition metal as a positive electrode active material. Provided is a lithium secondary battery including a positive electrode including at least one selected from a sulfide, a composite oxide of lithium and a transition metal, a conductive polymer material, and a carbon material, and the nonaqueous electrolyte.

Further, the present invention provides an additive for an electrolytic solution comprising an unsaturated sultone.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The non-aqueous electrolyte according to the present invention, a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte, and additives for the electrolyte will be specifically described. The non-aqueous electrolyte of the present invention is a non-aqueous electrolyte containing unsaturated sultone. A preferred embodiment of the present invention is a non-aqueous electrolyte comprising an unsaturated sultone, a non-aqueous solvent and an electrolyte. The present invention also provides a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte, and the present invention provides an additive for an electrolyte comprising an unsaturated sultone having a specific structure.

Unsaturated sultone The unsaturated sultone of the present invention is a sultone compound which is a cyclic sulfonic acid ester and has a carbon-carbon unsaturated bond in the ring. Preferred examples of the unsaturated sultone of the present invention include unsaturated sultone having a specific structure represented by the following general formula (1).

Embedded image Here, R ^{1 to} R ⁴ are hydrogen, fluorine, or carbon 1
A hydrocarbon group which may contain from 12 to 12 fluorine atoms, and n is an integer from 0 to 3.

As n, n = 0 to 3 are effective, but n = 1 or 2 is more preferable, and n = 1 is more preferable.

Specific examples of the hydrocarbon group having 1 to 12 carbon atoms which may contain fluorine include a methyl group, an ethyl group, a vinyl group, an ethynyl group, a propyl group, an isopropyl group,
Propenyl group, 2-propenyl group, 1-propynyl group, 2-propynyl group, butyl group, sec-butyl group, t-butyl group, 1-
Butenyl group, 2-butenyl group, 3-butenyl group, 2-methyl-2
-Propenyl group, 1-methylenepropyl group, 1-methyl-2-propenyl group, 1,2-dimethylvinyl group, 1-butynyl group, 2-
Butynyl group, 3-butynyl group, pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-methyl
-2-methylpropyl group, 2,2-dimethylpropyl group, phenyl group, methylphenyl group, ethylphenyl group, vinylphenyl group, ethynylphenyl group, hexyl group, cyclohexyl group, heptyl group, octyl group, nonyl group, decyl Group, undecyl group, dodecyl group, difluoromethyl group, monofluoromethyl group, trifluoromethyl group, trifluoroethyl group, difluoroethyl group, pentafluoroethyl group, pentafluoropropyl group, tetrafluoropropyl group, perfluorobutyl Group, perfluoropentyl group, perfluorohexyl group, perfluorocyclohexyl group, perfluoroheptyl group, perfluorooctyl group, perfluorononyl group, perfluorodecyl group, perfluoroundecyl group, perfluorododecyl group, fluorophen Examples thereof include a phenyl group, a difluorophenyl group, a trifluorophenyl group, a perfluorophenyl group, a trifluoromethylphenyl group, a naphthyl group and a biphenyl group.

The number of carbon atoms of R ^{1 to} R ⁴ is preferably 1 to 12, but is more preferably 4 or less, and still more preferably 2 or less, from the viewpoint of solubility in an electrolytic solution. Most preferred R ¹ -R ⁴ are that they are both hydrogen.

Specific examples of the unsaturated sultone of the present invention represented by the above general formula (1) include the following compounds.

[0035]

Embedded image

[0036]

Embedded image

The most preferred compound among these is 1,3-propene sultone represented by the following formula (2).

Embedded image

This compound can be synthesized by the method described in the following literature. Angew.Chem./70.Jahr
g.1958 / Nr.16, Ger.Pat.1146870 (1963) (CA 59 , 11259 (1
963)), Can.J.Chem., 48 , 3704 (1970), Synlett, 1411 (198
8), Chem. Commun., 611 (1997), Tetrahedron 55 , 2245 (19
99)

The electrolytic solution of the present invention to which the unsaturated sultone is added has a high effect of suppressing the reductive decomposition reaction of the electrolytic solution on the negative electrode, and suppresses a decrease in the capacity of the battery during a high-temperature storage test or a cycle test. Suppresses gas generation accompanying the decomposition of Although the function is unknown, it suppresses an increase in interfacial impedance of the positive electrode during a high-temperature storage test or a cycle test, thereby suppressing deterioration in load characteristics. The unsaturated sultone of the present invention is effective as an additive for an electrolytic solution, and the additive for an electrolytic solution comprising the unsaturated sultone of the present invention can impart excellent characteristics to the electrolytic solution.

If the amount of the unsaturated sultone of the present invention is too small, the effect may not be easily exhibited, and if it is too large, the interface impedance of the negative electrode may increase. Therefore, the addition amount (content in the electrolyte solution) of the unsaturated sultone of the present invention to the electrolyte solution is preferably 0.0001% by weight to 30% by weight, and
1 wt% to 10 wt% is more preferable, and 0.1 wt% to
7% by weight is more preferred, and 0.2-5% by weight is particularly preferred.

The unsaturated sultone of the present invention is presumed to form a passivation film for preventing the reductive decomposition of the electrolytic solution on the surface of the negative electrode and exert its effect. It may be determined from the amount of electrolyte to be made. If the addition amount is too small, a sufficient passive film will not be formed, and if the addition amount is too large, the interface impedance of the negative electrode active material may be excessively increased.

From this viewpoint, the unsaturated sultone of the present invention is:
0.1 mg / m ² to 1 per BET surface area of the negative electrode active material
00 mg / m ² is preferred, and 0.5 mg / m ^{2 to} 50 m
g / m ² is more preferable, and 1 mg / m ^{2 to} 20 mg / m
² is more preferred, and 2 mg / m ^{2 to} 10 mg / m ² is particularly preferred.

In this case, the amount of the unsaturated sultone of the present invention added to the electrolytic solution is determined in consideration of the ratio of the electrolytic solution used in the battery to the negative electrode active material, and the BET surface area of the negative electrode active material. .

Since the ratio of the amount of the electrolyte to the amount of the negative electrode active material and the BET surface area of the negative electrode are considered to vary depending on the battery, the preferable range of the amount added per electrolyte cannot be fixed. Thus, the content is preferably 0.0001% by weight to 30% by weight based on the whole electrolytic solution,
1 wt% to 10 wt% is more preferable, and 0.1 wt% to
7% by weight is more preferred, and 0.2-5% by weight is particularly preferred.

Non-aqueous solvent The non-aqueous solvent used in the present invention can be appropriately selected, and particularly preferably comprises a cyclic aprotic solvent and / or a chain aprotic solvent. .

Examples of the cyclic aprotic solvent include a cyclic carbonate such as ethylene carbonate, a cyclic carboxylic acid ester such as γ-butyrolactone, a cyclic sulfone such as sulfolane, and a cyclic ether such as dioxolan. Examples of the aprotic solvent include a chain carbonate such as dimethyl carbonate, a chain carboxylate such as methyl propionate, a chain ether such as dimethoxyethane, and a chain phosphate such as trimethyl phosphate. Is exemplified. These aprotic solvents may be used alone or as a mixture of two or more.

When the load characteristics and low-temperature characteristics of the battery are particularly intended to be improved, it is desirable that the non-aqueous solvent be a combination of a cyclic aprotic solvent and a chain aprotic solvent. Further, from the electrochemical stability of the electrolytic solution, it is most preferable to apply a cyclic carbonate to the cyclic aprotic solvent and to apply a chain carbonate to the chain aprotic solvent.

Also, the conductivity of the electrolytic solution relating to the charge / discharge characteristics of the battery can be increased by the combination of the cyclic carboxylate and the cyclic carbonate and / or chain carbonate.

Specific examples of the cyclic carbonate include:
Ethylene carbonate, propylene carbonate, 1,
Examples thereof include 2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and 2,3-pentylene carbonate. In particular, ethylene carbonate and propylene carbonate having a high dielectric constant are preferably used. In the case of a battery using graphite as the negative electrode active material, ethylene carbonate is particularly preferred. Further, 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, dipropyl carbonate,
Methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, methyl trifluoroethyl carbonate and the like can be mentioned. 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 kinds.

Specific examples of the cyclic carboxylic acid ester include γ-butyrolactone, γ-valerolactone, δ-valerolactone, and alkyl-substituted products such as methyl γ-butyrolactone, ethyl γ-valerolactone, and ethyl δ-valerolactone. Can be exemplified.

Specific examples of the combination of a cyclic carbonate and a chain carbonate include ethylene carbonate and dimethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, propylene carbonate and methyl ethyl carbonate, and propylene. Carbonate and diethyl carbonate,
Ethylene carbonate, 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 Methyl ethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and methyl ethyl carbonate and diethyl carbonate, ethylene carbonate and propylene carbonate and dimethyl carbonate and methyl ethyl carbonate,
Examples include ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate, and ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate.

The mixing ratio of the cyclic carbonate and the chain carbonate is represented by a weight ratio, and the ratio of the cyclic carbonate to the chain carbonate is 5:95 to 80:20, more preferably 10:90 to 70:30, and particularly preferably. 15:85
55:45. With such a ratio, the increase in the viscosity of the electrolyte can be suppressed, and the degree of dissociation of the electrolyte can be increased. Therefore, the conductivity of the electrolyte relating to the charge / discharge characteristics of the battery can be increased, and Can be further increased in solubility. Therefore, an electrolyte having excellent electrical conductivity at normal temperature or low temperature can be obtained, and the load characteristics of the battery at normal temperature to low temperature can be improved.

Specific examples of the combination of the cyclic carboxylic acid ester and the cyclic carbonate and / or chain carbonate include, specifically, γ-butyrolactone and ethylene carbonate, γ-butyrolactone, ethylene carbonate and dimethyl carbonate, and γ-butyrolactone and ethylene carbonate. And methyl ethyl carbonate, γ-butyrolactone and ethylene carbonate and diethyl carbonate, γ-butyrolactone and propylene carbonate, γ
-Butyrolactone and propylene carbonate and dimethyl carbonate, γ-butyrolactone and propylene carbonate and methyl ethyl carbonate, γ-butyrolactone and propylene carbonate and diethyl carbonate,
γ-butyrolactone, ethylene carbonate, propylene carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, γ-
Butyrolactone, ethylene carbonate, propylene carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, methyl ethyl carbonate, diethyl Carbonate,
γ-butyrolactone, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, ethylene carbonate, propylene carbonate, methyl ethyl carbonate and diethyl carbonate,
γ-butyrolactone, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, γ-butyrolactone and sulfolane, γ-butyrolactone and ethylene carbonate and sulfolane, γ-butyrolactone and propylene carbonate and sulfolane, γ-butyrolactone and ethylene carbonate And propylene carbonate and sulfolane, and γ-butyrolactone, sulfolane and dimethyl carbonate.

The mixing ratio of the cyclic carboxylic acid ester in the non-aqueous solvent is from 100 to 10%, more preferably from 90 to 20%, particularly preferably from 80 to 30%, by weight. With such a ratio, the conductivity of the electrolytic solution relating to the charge / discharge characteristics of the battery can be increased.

In order to improve the flash point of the solvent in order to improve the safety of the battery, it is preferable to use a cyclic aprotic solvent as the non-aqueous solvent. Cyclic aprotic solvents may be used alone or in combination of two or more. Further, a mixture of a cyclic aprotic solvent and a chain aprotic solvent may be used, but in this case where a mixture of a chain aprotic solvent is used, in this case, the chain aprotic solvent is used. Is preferably less than about 20% by weight based on the whole non-aqueous solvent.

A cyclic carboxylate such as γ-butyrolactone has a low vapor pressure, a low viscosity and a high dielectric constant. For this reason, the viscosity of the electrolyte can be reduced without lowering the flash point of the electrolyte and the degree of dissociation of the electrolyte. For this reason, since it has the feature that the conductivity of the electrolyte, which is an index related to the discharge characteristics of the battery, can be increased without increasing the flammability of the electrolyte, if the aim is to improve the flash point of the solvent, It is preferable to use a cyclic carboxylate as the cyclic aprotic solvent.

A preferred non-aqueous solvent for improving the flash point of the solvent is a cyclic carboxylate alone, but a preferred mixture of a cyclic carboxylate and another cyclic aprotic solvent is preferred.

Examples of preferred combinations of a mixture of a cyclic carboxylic acid ester and another cyclic aprotic solvent include γ-butyrolactone and ethylene carbonate, γ-butyrolactone,
Butyrolactone and propylene carbonate, γ-butyrolactone, ethylene carbonate and propylene carbonate, γ-butyrolactone, ethylene carbonate and sulfolane can be exemplified.

When a cyclic aprotic solvent is used to improve the flash point of the solvent in order to improve the safety of the battery, other preferable specific examples include ethylene carbonate, propylene carbonate, and the like. Sulfolane,
One kind selected from N-methyloxazolidinone or a mixture thereof can be mentioned. Specific combinations of the mixture include ethylene carbonate and propylene carbonate, ethylene carbonate and sulfolane, ethylene carbonate and propylene carbonate and sulfolane, and ethylene carbonate and N-methyloxazolidinone.

In order to improve the flash point of the solvent in order to improve the safety of the battery, chain carbonates, chain carboxylic esters, and chain aprotic solvents which may be mixed and used may be used. Chain phosphates are exemplified, and chain carbonates such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, diheptyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl butyl carbonate, and methyl heptyl carbonate are particularly preferable. .

In the non-aqueous electrolyte according to the present invention, the non-aqueous solvent
Then, other solvents other than the above may be included. Other melting
As the medium, specifically, dimethylformamide or the like
Chains of amide, methyl-N, N-dimethylcarbamate, etc.
Cyclic amines such as carbamates and N-methylpyrrolidone
Cyclic urea such as N, N, N-dimethylimidazolidinone
A, trimethyl borate, triethyl borate, triborate
Butyl, trioctyl borate, trimethylsilyl borate
And a boron-containing compound represented by the following general formula:
And ethylene glycol derivatives.
You. HO (CH₂CH ₂O)_aH, HO ｛CH₂CH
(CH₃) O｝_bH, CH₃O (CH₂CH₂O)
_cH, CH₃O @ CH₂CH (CH₃) O｝_dH, CH
₃O (CH₂CH₂O)_eCH₃, CH₃O ｛CH₂C
H (CH₃) O｝_fCH₃, C₉H₁₉PhO (CH₂
CH₂O)_g｛CH (CH₃) O｝_hCH₃(Ph is
Enyl group), CH₃O @ CH₂CH (CH₃) O｝_iC
O ｛OCH (CH₃) CH₂｝_jOCH ₃(The above equation
Wherein a to f are integers of 5 to 250, and g to j are 2 to 249.
Integer, 5 ≦ g + h ≦ 250, 5 ≦ i + j ≦ 250
You. )

Other Additives In the present invention, by further containing other additives in addition to the unsaturated sultone of the present invention, it is possible to impart more excellent characteristics to the electrolytic solution.

If other additives that may be added in the present invention alone have a function of suppressing the electrolysis on the negative electrode, the electrolysis on the negative electrode is further suppressed, and the self-removal of the battery is further suppressed. Discharge can be suppressed small. As a result, an effect is obtained that the load characteristics, high-temperature storage characteristics, and cycle characteristics of the battery are improved.

As such a compound having an effect of suppressing electrolysis on the negative electrode, a vinylene carbonate derivative represented by the following general formula (3):

Embedded image (R ⁵ and R ⁶ are hydrogen, methyl, ethyl, or propyl.);

Carboxylic anhydrides such as maleic anhydride, norbornene dicarboxylic anhydride, diglycolic acid, ethynyl phthalic anhydride, vinyl phthalic anhydride and sulfobenzoic anhydride; benzenedisulfonic anhydride, dibenzenesulfonic acid Phenylsulfonic acids such as anhydrides, benzenesulfonic acid methyl ester, o-, m-, p-benzenedisulfonic acid dimethyl ester, o-, m-, p-benzenedisulfonic acid dilithium salt; 1,3-propane sultone; And sultones comprising a saturated hydrocarbon substituent such as 1,4-butane sultone.

Of these compounds, vinylene carbonate derivatives represented by the general formula (3) are most preferred.

Specific examples of the vinylene carbonate derivative represented by the general formula (3) include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, propyl ethylene carbonate, dimethyl vinylene carbonate, diethyl vinylene carbonate,
Dipropyl vinylene carbonate and the like are exemplified. Of these, vinylene carbonate is most preferred.

When the above other additives are contained in the electrolyte together with the unsaturated sultone of the present invention, the ratio of the unsaturated sultone of the present invention to the other additives is 1: 1 by weight.
It is preferably from 100 to 100: 1, more preferably from 1:20 to 20: 1, and particularly preferably from 1:10 to 20: 1. In particular, when the other additive is vinylene carbonate, the above ratio is preferable, and the most preferable ratio is 1: 5 to 20:
1 can be mentioned. When the unsaturated sultone of the present invention and the above-mentioned other additives are both contained in the electrolytic solution, the total amount thereof is preferably 30% by weight or less based on the whole electrolytic solution.

Nonaqueous Electrolyte The nonaqueous electrolyte of the present invention is a nonaqueous electrolyte containing the unsaturated sultone of the present invention. More preferably, it comprises the unsaturated sultone of the present invention, a non-aqueous solvent and an electrolyte. 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, (C ₂ H ₅ ) ₄
NPF ₆ , (C ₂ H ₅ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ N
ClO ₄ , (C ₂ H ₅ ) ₄ NAsF ₆ , (C ₂ H ₅ ) ₄
N ₂ SiF ₆ , (C ₂ H ₅ ) ₄ NOSO ₂ C _k F
_{(2k + 1)} (k = 1 to 8), (C ₂ H ₅ ) _{4
NPF n (C k F (2k} + 1)) (6-n) (n = 1~
5, k = 1 to 8), such as a tetraalkylammonium salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , Li
_{AsF 6, Li 2 SiF 6,} LiOSO 2 C k F (2
_{k + 1)} (k = 1 to 8), LiPF _n (C _k F
_{(2k + 1)} ) _{(6-n )} (n = 1-5, k = 1-8)
And an integer of 1). Further, a lithium salt represented by the following general formula can also be used. L
iC (SO ₂ R ⁷ ) (SO ₂ R ⁸ ) (SO ₂ R ⁹ ), L
iN (SO ₂ OR ¹⁰ ) (SO ₂ OR ¹¹ ), LiN
(SO ₂ R ¹² ) (SO ₂ OR ¹³ ) (where R ⁷ to
R ¹³ may be the same or different from each other,
A perfluoroalkyl group having 1 to 8 carbon atoms). These lithium salts may be used alone or as a mixture of two or more.

Of these, lithium salts are particularly desirable, and LiPF ₆ , LiBF ₄ , LiOSO ₂ C
_k F _{(2k + 1)} (k = 1 to 8), LiCl
O ₄ , LiAsF ₆ , LiN (SO ₂ C _k F
_{(2k + 1)} ) ₂ (k = 1 to 8), LiPF _{n
(C k F (2k + 1} )) (6-n) (n = 1~5, k =
(An integer of 1 to 8) is preferred.

When a cyclic carboxylic acid ester such as γ-butyrolactone is used in combination as the non-aqueous solvent in the electrolytic solution of the present invention, it is particularly desirable to contain LiPF ₆ . Since LiPF ₆ has a high degree of dissociation, it can increase the conductivity of the electrolytic solution, and has an effect of suppressing the reductive decomposition reaction of the electrolytic solution on the negative electrode.

In the electrolytic solution of the present invention, it is recommended to use LiPF ₆ alone or use LiPF ₆ and another lithium salt. As the electrolyte used other than LiPF ₆ , any electrolyte which is usually used as a non-aqueous electrolyte electrolyte can be used. Specifically, among the specific examples of the lithium salt described above, lithium salts other than LiPF ₆ can be exemplified.

Specific examples of the combination of LiPF ₆ and another lithium salt include LiPF ₆ , LiBF ₄ and LiP
F ₆ and LiN (SO ₂ C _k F _{(2k + 1)} ) ₂ (k =
1-8), LiPF ₆ , LiBF ₄ and LiN (S
O ₂ C _k F _{(2k + 1)} ) ₂ (k = 1 to 8).

The ratio of LiPF _{6 in} the lithium salt is 100 to 1% by weight, preferably 100 to 10% by weight, and more preferably 100 to 50% by weight.

Such an electrolyte is preferably 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 electrolytic solution of the present invention preferably contains the unsaturated sultone of the present invention, a non-aqueous solvent and an electrolyte as essential components. If necessary, the above-mentioned other additives and other solvents may be used. Etc. may be added. In the electrolytic solution of the present invention, hydrogen fluoride, water, oxygen, nitrogen, and the like can be present in addition to the other additives described above.

When hydrogen fluoride is used as an additive, a method for adding hydrogen fluoride to the electrolyte is to directly blow a predetermined amount of hydrogen fluoride gas into the electrolyte. When the lithium salt used in the present invention is a lithium salt containing fluorine such as LiPF ₆ or LiBF ₄ , the water is converted into an electrolyte by utilizing a reaction between water and an electrolyte shown in the following (formula 1). Added to
It may be generated in an electrolytic solution. _{LiMF n + H 2 O → LiPF} (n-2) O + 2HF ( Equation 1) (where, M = P, B, etc., when M is P, n = 6, M
When B is n = 4)

As a method of adding water to the electrolyte, water may be directly added to the electrolyte or water may be previously contained in the electrode of the battery, and after the electrolyte is injected into the battery, Water may be supplied from inside to the electrolyte.

When water is added to the electrolyte and HF is generated indirectly in the electrolyte, 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 between the electrolyte and water, a protic compound having a strong acidity other than water can be used. As such a compound, specifically, methanol, ethanol, ethylene glycol, propylene glycol, acetic acid, acrylic acid, maleic acid,
1,4-dicarboxy-2-butene and the like can be raised. The addition amount of hydrogen fluoride is preferably 0.0001 to 0.7% by weight based on the whole electrolytic solution, and 0.001 to 0.7% by weight.
-0.3 wt% is more preferable, 0.001-0.2 wt% is more preferable, and 0.001-0.1 wt% is particularly preferable.

The non-aqueous electrolyte according to the present invention as described above
Not only suitable as a non-aqueous electrolyte for lithium secondary batteries, but also as a non-aqueous electrolyte for primary batteries, a non-aqueous electrolyte for electrochemical capacitors, an electric double layer capacitor, an electrolyte for aluminum electrolytic capacitors Can also be used.

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 lithium metal, a lithium-containing alloy, a metal or alloy capable of being alloyed with lithium, an oxide capable of doping and undoping lithium ions, and a lithium ion doping / dedoping. Either a transition metal nitride which can be de-doped, a carbon material which can be doped or de-doped with lithium ions, or a mixture thereof can be used.

Examples of the metal or alloy that can be alloyed with lithium include silicon, silicon alloy, tin, and tin alloy. Examples of oxides that can be doped and undoped with lithium ions include tin oxide and silicon oxide, and transition metal oxides that can be doped and undoped with lithium ions.

Among them, lithium ions are
Carbon materials that can be de-dove are preferred. Such a carbon material may be carbon black, activated carbon, artificial graphite, natural graphite or amorphous carbon, and may be in any form of fibrous, spherical, potato, or flake.

Specific examples of the amorphous carbon material include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500 ° C. or lower, mesophase pitch carbon fiber (MCF), and the like. There are natural graphite and artificial graphite, and as the artificial graphite, graphitized MCMB, graphitized MCF and the like are used. Further, as the graphite material, a material containing boron or the like can be used, and gold, platinum, silver, copper, Sn
A material coated with such a metal, a material coated with amorphous carbon, or a mixture of amorphous carbon and graphite can also be used.
These carbon materials may be used alone or in combination of two or more.

As the carbon material, the plane distance d _{(002 ) of} the (002) plane measured by X-ray analysis is 0.340 nm.
The following carbon materials are preferable, and the true density is 1.70 g / cm
Graphite of ³ or more or a highly crystalline carbon material having properties close thereto is preferred. 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, Fe
S₂, MoS₂, TiS₂, MnO ₂, V₂O₅Such as
Transition metal oxide or transition metal sulfide, LiCoO₂,
LiMnO₂, LiMn₂O₄, LiNiO₂, LiNi_x
Co_(1-x)O₂, LiNi_xCo_yMn
_(1-xy)O₂Such as lithium and transition metal
Composite oxide, polyaniline, polythiophene,
Roll, polyacetylene, polyacene, dimercaptochi
Conductive polymers such as azizole / polyaniline composite
Materials, carbon materials such as fluorinated carbon, activated carbon, etc.
It is.

Among these, a composite oxide composed of lithium and a transition metal is particularly preferred. One type of the positive electrode active material may be used, or two or more types may be used in combination. Since the positive electrode active material generally has insufficient conductivity, the positive electrode is used together with a conductive auxiliary to constitute a positive electrode. Examples of the conductive assistant include carbon materials such as carbon black, amorphous whiskers, and graphite.

The separator is a film that electrically insulates the positive electrode and the negative electrode and transmits lithium ions, and examples thereof include a porous film and a polymer electrolyte. As the porous film, a microporous polymer film is suitably used, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester, and the like. 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. Other resins having excellent thermal stability may be coated on the porous polyolefin film.

Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved, a polymer swelled with an electrolytic solution, and the like. The electrolyte of the present invention may be used for the purpose of obtaining a polymer electrolyte by swelling a polymer.

Such a non-aqueous electrolyte secondary battery can be formed in a cylindrical shape, a coin shape, a square shape, a film 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 nonaqueous electrolyte secondary battery, a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector such as a copper foil and a positive electrode current collector such as an Al foil A positive electrode coated with a substance is wound around 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.

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 filled with a non-aqueous electrolyte, a disc-shaped positive electrode, and, if necessary, a spacer plate of stainless steel or aluminum are stacked in this order on a coin-type battery can. It is stored.

[0097]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

[0098] (Examples 1 to 6 and Reference Example 1). Preparation of coin-type battery < Preparation of non-aqueous electrolyte> Ethylene carbonate (EC) and methyl ethyl carbonate (MEC) were mixed with EC: MEC.
= 4: 6 (weight ratio), and then LiPF ₆ as an electrolyte was dissolved in a non-aqueous solvent to prepare a non-aqueous electrolyte so that the electrolyte concentration was 1.0 mol / L. Next, 1,3-
Propene sultone 0.5% by weight (Example 1), 1.0% by weight (Example 2), 1.5% by weight (Example 3), 2.0%
% By weight (Example 4), 2.5% by weight (Example 5) 3.0
By weight (Example 6), a non-aqueous electrolyte of the present invention was obtained. In addition, the case where the addition of the additive was omitted is shown in Reference Example 1.
(Blank).

<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 strip-shaped copper foil-made negative electrode current collector, and dried. This was compression-molded and punched into a 14 mm disc to obtain a coin-shaped natural graphite electrode. The thickness of this natural graphite electrode mixture is 110
μm and weighs 20 per area of a 14 mm diameter circle.
mg.

<Preparation of LiCoO ₂ electrode> LiCoO 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 is applied to a 20 μm thick aluminum foil,
Dried. This was compression-molded and punched into a 13.5 mm disk to obtain a coin-shaped LiCoO ₂ electrode. This L
The thickness of the iCoO ₂ mixture is 90 μm and the weight is 1
The weight was 40 mg per 3.5 mm circle area.

<Production of Battery> A natural graphite electrode having a diameter of 14 mm, a LiCoO ₂ electrode having a diameter of 13.5 mm, and a thickness of 25 μm
A separator made of a microporous polypropylene film having a diameter of 16 mm and a diameter of 16 mm was placed in a stainless steel battery can of 2032 size using a natural graphite electrode, a separator, and LiCo.
It was laminated in the order of O ₂ electrodes. Thereafter, 0.03 ml of the non-aqueous electrolyte prepared above was injected into the separator, and an aluminum plate (thickness: 1.2 mm, diameter: 16 mm, and a spring was housed. Finally, via a gasket made of polypropylene, By caulking the battery can lid, airtightness in the battery was maintained, and a coin-type battery having a diameter of 20 mm and a height of 3.2 mm was produced.

[0102] 3. Evaluation of battery characteristics < Evaluation of high-temperature storage characteristics by battery> A coin-type battery prepared as described above was used, and the battery was operated at a constant voltage of 0.3 mA, a constant voltage of 4.2 V, and a constant voltage of 4.2 V. Was charged until the current value became 0.05 mA, and then discharged under the condition of 1 mA constant current and 3.0 V constant voltage until the current value at the time of 3.0 V constant voltage became 0.05 mA. Next, the battery was subjected to 3.85 V under the condition of 1 mA constant current and 3.85 V constant voltage.
The battery was charged until the current value at the time of constant voltage became 0.05 mA. Thereafter, the battery was stored (“aging”) in a thermostat at 45 ° C. for 7 days.

After aging, under the conditions of a constant current and a constant voltage of 1 mA, the termination condition was a current value of 0.05 mA at the time of a constant voltage, and a charge / discharge of 4.2 V to 3.0 V was performed once to discharge capacity (“low load”). Discharge capacity ") was measured. At this time, the resistance of the battery ("resistance after aging") was determined from the change in the battery voltage two minutes after the start of discharging. Next, the battery was charged to 4.2 V under the same conditions, then discharged at a constant current of 10 mA, and discharged when the battery voltage reached 3.0 V. ) Was measured. In Examples 20 to 22 and Reference Example 3, the measurement was performed at a constant current discharge current of 5 mA instead of 10 mA. Then, the ratio of the high load discharge capacity to the low load discharge capacity at this time is determined, and this is referred to as “load characteristic index after aging”.
And

After the battery was once discharged to 3.0 V, the capacity when recharged to 4.2 V (“charge capacity”) was measured, and then stored at 60 ° C. for 4 days (“high-temperature storage”). Was.

After storage at high temperature, the capacity when discharged to 3.0 V (“remaining capacity”) was measured. Further, "low load discharge capacity" and "high load discharge capacity" were measured in the same manner as in aging, and "load characteristic index after high temperature storage" was obtained.
Further, "resistance after high-temperature storage" corresponding to "resistance after aging" was measured.

The results of the above examples were analyzed based on the following indices. The ratio of the “load characteristic index after high-temperature storage” to the “load characteristic index after aging” was defined as “load characteristic change rate”. Load characteristic change rate = (“Load characteristic index after high temperature storage” /
"Load characteristic index after aging") x 100 (%) "resistance after high temperature storage" against "resistance after aging"
Is defined as the “resistance change rate”. Resistance change rate = (“resistance after high-temperature storage” / “resistance before high-temperature storage (after aging)”) × 100 (%)

The difference between the charge capacity after aging and before storage at high temperature and the remaining capacity after storage at high temperature (charge capacity-remaining capacity) was obtained as an index indicating the self-discharge property of the battery, that is, the electrolytic property of the electrolyte. Was. The ratio of the difference of the electrolytic solution to the difference of the electrolytic solution (Reference Example 1, blank) when no additive was added was determined as the “self-discharge ratio”. Self-discharge ratio = {(charge capacity of electrolyte−remaining capacity) / (charge capacity of blank−remaining capacity of blank)} × 100
(%) Table 1 shows the measurement results of the evaluated battery characteristics.

(Comparative Examples 1 to 13) Table 1 shows the results obtained in Example 1 in place of adding 0.5% by weight of 1,3-propene sultone as an additive in <Preparation of nonaqueous electrolyte>. A coin-type battery was prepared in the same manner except that the above additives were added in the amounts shown in the same table, and the battery characteristics were measured. The results are shown in Table 1.

[0109]

[Table 1]

From the above results, the electrolytic solution to which 1,3-propene sultone of the present invention is added has an excellent effect on the self-discharge ratio, the load characteristics and the suppression of the deterioration of the resistance in comparison with the comparative example. You can see that.

(Examples 7 to 15) In Example 1, in <Preparation of non-aqueous electrolyte>, vinylene carbonate was added in addition to 1,3-propene sultone as an additive. A coin-type battery was prepared in the same manner except that the amount was added, and the battery characteristics were measured. The results are shown in Table 2.

[0112]

[Table 2]

From the above results, the 1,3-propene sultone of the present invention shows an excellent action even when used alone. However, when the amount of addition to the electrolytic solution was kept constant, when 1,3-propene sultone was used together with vinylene carbonate, It can be seen that the discharge rate ratio is further reduced, and the effect of suppressing the deterioration of the load characteristics and the resistance can be maintained at a high level.

Reference Example 2 A laminated battery was manufactured, and the amount of gas generated in the battery during a high-temperature storage test was measured. 1. Preparation of Laminated Battery <Preparation of Nonaqueous Electrolyte> The nonaqueous electrolyte prepared in Reference Example 1 was used as the nonaqueous electrolyte.

<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 a strip-shaped copper foil and dried. The thickness of this natural graphite electrode mixture was 110 μm. 85mm ×
A lead wire made of stamped copper was attached to 50 mm.

<Preparation of LiCoO ₂ electrode> LiCoO 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 is applied to a 20 μm thick aluminum foil,
Dried. This was punched out to 76 mm x 46 mm, and a lead wire made of platinum was attached.

<Preparation of Laminated Battery> Dimension 85 mm ×
50mm natural graphite electrode, L of size 76mm x 46mm
The iCoO ₂ electrodes were opposed to each other via a separator made of a microporous polypropylene film having a width of 55 mm and a length of 110 mm to form an electrode group. This electrode group is housed in a cylindrical bag made of an aluminum laminate film (manufactured by Showa Laminate) so that both the positive and negative lead wires are pulled out from one open part. The other side was heat-sealed and closed. Next, 1.4 ml of the nonaqueous electrolyte solution prepared above was injected into the electrode group and impregnated.
The remaining open portion was heat-sealed to seal the electrode group in a bag, thereby obtaining a laminated battery.

[0118] 2. Measurement of gas generation amount during high-temperature storage using a laminated battery A laminated battery prepared as described above was used, and this battery was subjected to 4.2 V at a constant current of 10 mA and a constant voltage of 4.2 V.
Charge until the current value at the time of constant voltage becomes 0.05 mA,
Thereafter, the battery was discharged at a constant current of 10 mA, and the battery was discharged under the condition that the discharge was terminated when the battery voltage reached 3.0 V. next,
Under the condition of 10 mA constant current and 3.85 V constant voltage,
The battery was charged until the current value at a constant voltage of 3.85 V became 0.05 mA.

Thereafter, the battery was placed in a thermostat at 45 ° C. for 7 hours.
Aged for days. After the aging, the battery was discharged at a constant current of 10 mA, and the battery was discharged under the condition that the discharge was stopped when the battery voltage reached 3.0 V. Next, this battery is
The battery was charged under the condition of A constant current of 4.2 V constant voltage until the current value at the time of 4.2 V constant voltage became 0.05 mA. The battery was stored at 85 ° C. for 3 days.

Immediately after the production of a laminated battery and after storage at a high temperature, the volume of the battery was measured, and the difference was defined as the amount of gas generated. Table 3 shows the results.

(Example 16) Example 1 was used as a non-aqueous electrolyte.
A laminated battery was prepared in the same manner as in Reference Example 2 except that the non-aqueous electrolyte adjusted at 0 was used, and the amount of gas generated during high-temperature storage was measured. Table 3 shows the results.

(Example 17) Example 1 using a non-aqueous electrolyte
A laminated battery was prepared in the same manner as in Reference Example 2 except that the non-aqueous electrolyte prepared in the above was used, and the amount of gas generated during high-temperature storage was measured. Table 3 shows the results.

(Example 18) Example 1 using a non-aqueous electrolyte
A laminated battery was prepared in the same manner as in Reference Example 2 except that the non-aqueous electrolyte prepared in 1 was used, and the amount of gas generated during high-temperature storage was measured. Table 3 shows the results.

(Embodiment 19) Embodiment 3 using a non-aqueous electrolyte
A laminated battery was prepared in the same manner as in Reference Example 2 except that the non-aqueous electrolyte prepared in the above was used, and the amount of gas generated during high-temperature storage was measured. Table 3 shows the results.

(Comparative Example 14) As a non-aqueous electrolytic solution, in Example 3, <Preparation of non-aqueous electrolytic solution>,
Instead of 1.5% by weight of 3-propene sultone, 1,3-
Using a non-aqueous electrolyte prepared in the same manner except that 1.5% by weight of propane sultone was added, a laminated battery was prepared in the same manner as in Reference Example 2, and the amount of gas generated during high-temperature storage was measured. Table 3 shows the results.

[0126]

[Table 3]

(Examples 20 to 22) In Example 1,
In <Preparation of Non-Aqueous Electrolyte>, ethylene carbonate (EC), γ-butyrolactone (γ-BL) and dibutyl carbonate (DBC) were used as non-aqueous solvents, and EC: γ-BL: D
BC = 30: 65: 5 (weight ratio), and then, as an electrolyte, LiPF ₆ was prepared as a non-aqueous electrolyte so as to have an electrolyte concentration of 1 mol / liter. 1% by weight of 1,3-propene sultone (Example 20), 2% by weight of 1,3-propene sultone (Example 21), 2% by weight of 1,3-propene sultone and vinylene carbonate A coin-type battery was prepared in the same manner except that a 2% by weight mixture (Example 22) was added to obtain a non-aqueous electrolyte, and the battery characteristics were measured. The case where the addition of the additive was omitted was referred to as Reference Example 3. The results are shown in Table 4.

[0128]

[Table 4]

[0129]

According to the present invention, the use of the electrolytic solution to which the unsaturated sultone is added makes it possible to reduce self-discharge, greatly suppress the deterioration of load characteristics and resistance, and greatly reduce the amount of gas generated in the battery. The obtained non-aqueous electrolyte secondary battery can be obtained. Further, the non-aqueous solvent having a specific composition according to the present invention can provide a non-aqueous electrolyte secondary battery having excellent low-temperature characteristics and load characteristics.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Chiho Hirano 580-32 Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals Co., Ltd. (72) Inventor Takeshi Hayashi 580-32 Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals F Terms (Reference) 5H029 AJ02 AJ04 AJ06 AJ07 AK03 AL02 AL07 AL12 AM02 AM03 AM04 AM05 AM07 BJ02 BJ03 BJ12 BJ14 DJ08 DJ17 HJ01 HJ02 HJ13 5H050 AA02 AA09 AA12 AA13 BA16 BA17 CA02 CA07 CA08 CA11 CA02 CB01 CB01

Claims (27)

[Claims] 1. A non-aqueous electrolyte containing unsaturated sultone. 2. The non-aqueous electrolyte according to claim 1, wherein the unsaturated sultone is a compound represented by the following general formula (1). Embedded image Here, R ^{1 to} R ⁴ are hydrogen, fluorine, or carbon 1
A hydrocarbon group which may contain from 12 to 12 fluorine atoms, and n is an integer from 0 to 3. 3. The non-aqueous electrolyte according to claim 2, wherein in the general formula (1), R ^{1 to} R ⁴ are both hydrogen. 4. The non-aqueous electrolyte according to claim 2, wherein n in the general formula (1) is 1. 5. The non-aqueous electrolyte according to claim 1, wherein the unsaturated sultone is 1,3-propene sultone represented by the following formula (2). Embedded image 6. The non-aqueous electrolyte according to claim 1, wherein the amount of the unsaturated sultone is 0.001% by weight to 10% by weight based on the whole non-aqueous electrolyte. Water electrolyte. 7. The non-aqueous electrolyte according to claim 1, further comprising a non-aqueous solvent and an electrolyte in addition to the unsaturated sultone. 8. The non-aqueous electrolytic solution according to claim 7, wherein the non-aqueous solvent contains a cyclic aprotic solvent and / or a chain aprotic solvent. 9. The non-aqueous electrolyte according to claim 8, wherein the cyclic aprotic solvent is a cyclic carbonate, a cyclic carboxylate, a cyclic sulfone, or a mixture thereof. 10. The non-aqueous electrolyte according to claim 9, wherein the cyclic aprotic solvent is ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfolane or a mixture thereof. 11. The cyclic aprotic solvent is γ-butyrolactone or a mixture of γ-butyrolactone and at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, sulfolane and methylsulfolane. The non-aqueous electrolyte according to claim 9, wherein 12. The non-aqueous electrolyte according to claim 8, wherein the chain aprotic solvent is a chain carbonate, a chain ester, or a mixture thereof. 13. The linear aprotic solvent is any of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate,
Or a mixture thereof.
3. The non-aqueous electrolyte according to 2. 14. The weight ratio of the cyclic aprotic solvent to the chain aprotic solvent in the non-aqueous solvent is 15:85 to 5:
The non-aqueous electrolyte according to any one of claims 8 to 13, wherein the ratio is 5:45. 15. The non-aqueous electrolyte according to claim 1, further comprising a vinylene carbonate derivative represented by the following general formula (3). Embedded image (R ⁵ and R ⁶ are hydrogen, a methyl group, an ethyl group, or a propyl group.) 16. The method according to claim 15, wherein the addition ratio of the unsaturated sultone to the vinylene carbonate derivative represented by the general formula (3) is 1: 100 to 100: 1 by weight. Water electrolyte. 17. The electrolyte according to claim 1, wherein the electrolyte is a lithium salt.
17. The non-aqueous electrolyte according to any one of 16. 18. The lithium salt is LiPF6, LiB
F₄, LiOSO₂C_kF _{(2k + 1)}(K = 1-8
Integer), LiClO4, LiAsF₆, LiN (SO ₂C
_kF_{(2k + 1)})₂(K = 1 to 8), LiPF
_n(C_kF_{(2k + 1)})_(6-n)(N = 1-5, k
= 1 to 8)
18. The non-aqueous electrolyte according to claim 17, wherein: 19. A non-aqueous electrolyte containing a non-aqueous solvent containing unsaturated sultone and γ-butyrolactone, and an electrolyte containing LiPF6. 20. As the negative electrode active material, metallic lithium, a lithium-containing alloy, a metal or alloy capable of being alloyed with lithium, an oxide capable of doping and undoping lithium ions, and a doping and undoping of lithium ions A negative electrode containing at least one selected from a transition metal nitride, a carbon material capable of doping / dedoping lithium ions, or a mixture thereof; A lithium secondary battery comprising: a positive electrode including at least one selected from a composite oxide of a transition metal, a conductive polymer material, and a carbon material; and the nonaqueous electrolyte according to claim 1. . 21. The lithium secondary battery according to claim 20, wherein the negative electrode active material is a carbon material capable of doping / dedoping lithium ions. 22. The inter-plane distance d _{(002 )} of the (002) plane of a carbon material capable of being doped / dedoped with lithium ions as a negative electrode active material, as measured by X-ray analysis,
The lithium secondary battery according to claim 21, wherein the thickness is 0.340 nm or less. 23. An electrolyte additive comprising an unsaturated sultone. 24. An unsaturated sultone having the general formula (1)
24. A compound represented by the formula:
The additive for an electrolytic solution according to 1. 25. In the general formula (1), R ^{1 to} R ⁴
25. The additive for an electrolytic solution according to claim 24, wherein is hydrogen. 26. The additive for an electrolytic solution according to claim 24, wherein n is 1 in the general formula (1). 27. The additive for an electrolytic solution according to claim 23, wherein the unsaturated sultone is 1,3-propene sultone represented by the formula (2).