JP2006351337A - Lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery having little deterioration of capacity against charge and discharge cycle by increasing open circuit voltage between battery terminals at finishing of charging and controlling the amount of gas generation at continuous charging. <P>SOLUTION: A sulfonate compound of the formula (1) is made to contain in a non-aqueous electrolytic solution of a lithium secondary battery having the open circuit voltage between battery terminals of 4.25 V or more at the finishing of charging at 25°C. In the formula (1), L expresses a bivalent coupling group constituted of carbon atom and hydrogen atom, R expresses non-substituted or fluorine-substituted aliphatic hydrocarbon group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lithium secondary battery using a non-aqueous electrolyte.

  Lithium secondary batteries have the advantages of high energy density and less self-discharge. Therefore, in recent years, it has been widely used as a power source for consumer mobile devices such as mobile phones, notebook computers, and PDAs.

  A conventional electrolyte for a lithium secondary battery is composed of a lithium salt that is a supporting electrolyte and a nonaqueous solvent. The nonaqueous solvent used here is required to have a high dielectric constant in order to dissociate the lithium salt, to exhibit high ionic conductivity in a wide temperature range, and to be stable in the battery. Since it is difficult to achieve these requirements with a single solvent, usually a combination of a high boiling point solvent typified by propylene carbonate, ethylene carbonate and the like and a low boiling point solvent such as dimethyl carbonate, diethyl carbonate, Used as a non-aqueous solvent.

  In order to improve various characteristics of lithium secondary batteries, various improvements are made to improve initial capacity, rate characteristics, cycle characteristics, high temperature storage characteristics, low temperature characteristics, continuous charge characteristics, self-discharge characteristics, overcharge prevention characteristics, etc. Many methods have been reported so far in which a small amount of the above-mentioned auxiliary is contained in the electrolyte. However, a universal electrolyte for all properties has not yet been found.

  On the other hand, for the purpose of improving the energy density, attempts have been made to charge to a high end voltage exceeding 4.2V. Specifically, when a conventional general lithium secondary battery is charged at 25 ° C., the open circuit voltage between the battery terminals at the end of charging is usually 4.2 V or less. For this reason, there has been an attempt to develop a lithium secondary battery in which, when charged at 25 ° C., the open circuit voltage between battery terminals at the end of charging exceeds 4.2V. However, the higher the voltage, the more unavoidable side reactions are caused by the decomposition of the electrolyte in the positive electrode, and the cycle deterioration becomes extremely large. Therefore, the conventional lithium secondary voltage is increased until the open circuit voltage between the battery terminals exceeds 4.2V. When the battery was charged, it was not practical.

  In addition, even when an electrolytic solution that is effective for improving the cycle characteristics at a voltage of 4.2 V or lower is applied, the battery performance can be improved even when such an electrolytic solution exceeds 4.2 V. Not necessarily bring. For example, the electrolytic solution containing cyclohexylbenzene disclosed in Patent Document 1 did not show improvement in cycle characteristics at 4.4 V, as shown in a comparative example later.

In response to such a desire to increase the open circuit voltage between the battery terminals at the end of charging, Patent Document 2 discloses a technique using an electrolytic solution composed of a nonaqueous solvent containing 50% by volume or more of γ-butyrolactone and a lithium salt. Proposed. Moreover, this patent document 2 describes that the capacity of a secondary battery whose open circuit voltage between battery terminals at 25 ° C. at full charge is 4.3 V or more is increased by the above technique, and the cycle characteristics and the like are further improved. Has been.
Patent Document 3 discloses that the cycle characteristics at 4.3 V are improved by using an electrolytic solution containing a sultone compound having a 5- to 7-membered cyclic sulfonate structure as a main skeleton.

Japanese Patent No. 3417228 JP 2003-272704 A JP 2004-235145 A

  In recent years, the demand for higher performance of lithium secondary batteries has increased, and it has been required to achieve various characteristics such as high capacity, cycle characteristics, high-temperature storage characteristics, and continuous charge characteristics at a high level. ing. Among them, improvement of continuous charge characteristics and cycle characteristics have been particularly demanded recently.

  However, the lithium secondary batteries conventionally proposed in Patent Documents 1 to 3 and the like have insufficient continuous charge characteristics and cycle characteristics. This is the same in the techniques conventionally proposed in Patent Documents 2 to 3 and the like that a lithium secondary battery having a high open circuit voltage between battery terminals at the end of charging can be obtained.

  The present invention was devised in view of the above problems, can increase the open circuit voltage between the battery terminals at the end of charging, can suppress the amount of gas generated during continuous charging, and is further charged and discharged. An object of the present invention is to provide a lithium secondary battery with little capacity deterioration even with respect to the cycle.

  As a result of intensive studies to solve the above problems, the inventor of the present invention increases the open circuit voltage between the battery terminals at the end of charging by incorporating a sulfonate compound having a specific structure into the non-aqueous electrolyte. In addition, the present inventors have found that the amount of gas generated during continuous charging can be suppressed and the cycle capacity retention rate can be improved, and the present invention has been completed.

（式（１）中、Ｌは炭素原子と水素原子とから構成された２価の連結基を表わす。Ｒは、それぞれ独立に、無置換又はフッ素で置換された脂肪族飽和炭化水素基を表わす。） That is, the gist of the present invention includes a positive electrode, a negative electrode, and a nonaqueous electrolytic solution containing a sulfonate compound represented by the following formula (1), and an open circuit voltage between battery terminals at 25 ° C. at the end of charging is 4. It exists in the lithium secondary battery characterized by being 25V or more (Claim 1).

(In Formula (1), L represents a divalent linking group composed of a carbon atom and a hydrogen atom. R independently represents an aliphatic saturated hydrocarbon group which is unsubstituted or substituted with fluorine. .)

At this time, the open circuit voltage between the battery terminals is preferably 4.3 V or more (claim 2).
Moreover, it is preferable that this non-aqueous electrolyte solution contains unsaturated carbonates (Claim 3).

  According to the present invention, a lithium secondary battery can be charged up to a high open circuit voltage between battery terminals, the amount of gas generated during continuous charging can be suppressed, and the cycle characteristics can be improved.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented without departing from the gist of the present invention.
The lithium secondary battery of the present invention includes a non-aqueous electrolyte, a positive electrode, and a negative electrode. In addition, the lithium secondary battery of the present invention may include other components.

[I. Non-aqueous electrolyte]
The non-aqueous electrolyte solution used in the lithium secondary battery of the present invention (hereinafter, appropriately referred to as “non-aqueous electrolyte solution in the present invention”) is a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent, Contains sulfonate compounds of specific structure.

なお、式（１）中、Ｌは炭素原子と水素原子とから構成された２価の連結基を表わす。また、Ｒは、それぞれ独立に、無置換又はフッ素で置換された脂肪族飽和炭化水素基を表わす。 [1. Sulfonate compound]
[1-1. type]
The sulfonate compound contained in the non-aqueous electrolyte solution in the present invention (hereinafter referred to as “the sulfonate compound of the present invention” as appropriate) is represented by the following formula (1).

In formula (1), L represents a divalent linking group composed of a carbon atom and a hydrogen atom. R independently represents an aliphatic saturated hydrocarbon group which is unsubstituted or substituted with fluorine.

Hereinafter, Formula (1) will be described in more detail.
In the said General formula (1), L represents the bivalent coupling group comprised from the carbon atom and the hydrogen atom.
The number of carbon atoms constituting the linking group L is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 2 or more, usually 10 or less, preferably 6 or less, more preferably 4 or less. .

Specific examples of the linking group L include the following.

In the formula (1), R represents an aliphatic saturated hydrocarbon group which is unsubstituted or substituted with fluorine. Here, when R is substituted with fluorine, only some of the hydrogen atoms of R may be substituted with fluorine, or all of the hydrogen atoms of R may be substituted with fluorine.
Among these, R is preferably an aliphatic saturated hydrocarbon group in which some or all of the hydrogen atoms are substituted with fluorine.

  The number of carbons constituting R is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 or more, usually 8 or less, preferably 4 or less, more preferably 2 or less. When this upper limit is exceeded, the compatibility or solubility of the sulfonate compound of the present invention with respect to the non-aqueous electrolyte decreases, and the gas generation suppression and cycle during continuous charging of the lithium secondary battery of the present invention using the non-aqueous electrolyte There is a possibility that sufficient effects cannot be exhibited in improving the characteristics.

  Furthermore, in formula (1), there are two Rs, but Rs may be the same or different from each other. However, from the viewpoint of facilitating the production of the sulfonate compound of the present invention, it is preferable that Rs are the same as each other.

  Specific examples of R include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group; trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, perfluorobutyl group, Linear perfluoroalkyl groups such as perfluoropentyl group, perfluorohexyl group, perfluoroheptyl group, perfluorooctyl group; perfluoro-1-methylethyl group, perfluoro-t-butyl group, perfluoro-3 -Branched perfluoroalkyl groups such as methylbutyl group and perfluoro-5-methylhexyl group; fluoromethyl group, difluoromethyl group, 2-fluoroethyl group, 1,1-difluoroethyl group, 1,2-difluoroethyl group, 2,2-difluoroethyl group, 1,1,2-trifluoroethyl group, 2, , 2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 1,2,2,2-tetrafluoroethyl group, 1,2,2 , 3,3,4,4,4-octafluorobutyl group, etc., partially fluorine-substituted linear alkyl group; di (fluoromethyl) methyl group, bis (trifluoromethyl) methyl group, 1-trifluoromethyl-ethyl group 1,1-bis (trifluoromethyl) ethyl group, 1-methyl-1-trifluoromethylethyl group, 1-trifluoromethylhexyl group, 1-fluoro-1-methylethyl group, 1,2,2,2 -Partially fluorine-substituted branched chain such as tetrafluoro-1-methylethyl group, 1,1-difluoro-2-methylpropyl group, 1,2,2,3,3,3-hexafluoro-1-methylpropyl group Kill group, and the like.

  Among these, those having 4 or less carbon atoms are preferable. For example, methyl group, ethyl group, propyl group, butyl group, trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, perfluorobutyl group, perfluoro-1-methylethyl group, perfluoro-t-butyl group , Fluoromethyl group, difluoromethyl group, 2-fluoroethyl group, 1,1-difluoroethyl group, 1,2-difluoroethyl group, 2,2-difluoroethyl group, 1,1,2-trifluoroethyl group, 2,2,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 1,2,2,2-tetrafluoroethyl group, di ( Fluoromethyl) methyl group, bis (trifluoromethyl) methyl group, 1-trifluoromethyl-ethyl group, 1,1-bis (trifluoromethyl) Til, 1-methyl-1-trifluoromethylethyl, 1-fluoro-1-methylethyl, 1,2,2,2-tetrafluoro-1-methylethyl, 1,1-difluoro-2- A methylpropyl group, 1,2,2,3,3,3-hexafluoro-1-methylpropyl group and the like are preferable.

  Furthermore, those having 2 or less carbon atoms are more preferable. For example, methyl group, ethyl group, trifluoromethyl group, pentafluoroethyl group, fluoromethyl group, difluoromethyl group, 2-fluoroethyl group, 1,1-difluoroethyl group, 1,2-difluoroethyl group, 2, 2-difluoroethyl group, 1,1,2-trifluoroethyl group, 2,2,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl Group, 1,2,2,2-tetrafluoroethyl group and the like are more preferable.

  Among these, those containing fluorine are more preferable. For example, trifluoromethyl group, pentafluoroethyl group, fluoromethyl group, difluoromethyl group, 2-fluoroethyl group, 1,1-difluoroethyl group, 1,2-difluoroethyl group, 2,2-difluoroethyl group, 1,1,2-trifluoroethyl group, 2,2,2-trifluoroethyl group, 1,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 1,2, 2,2-tetrafluoroethyl group and the like are more preferable.

  Furthermore, the molecular weight of the sulfonate compound of the present invention is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 200 or more, usually 800 or less, preferably 600 or less, more preferably 450 or less. When the upper limit of this range is exceeded, the compatibility or solubility of the sulfonate compound of the present invention with respect to the non-aqueous electrolyte decreases, and the suppression of gas generation during continuous charging of the lithium secondary battery of the present invention using the non-aqueous electrolyte. In addition, there is a possibility that sufficient effects cannot be exhibited in improving the cycle characteristics.

Hereinafter, although the specific example of the sulfonate compound of this invention is given, the sulfonate compound of this invention is not limited to the following illustrations.
Specific examples of the sulfonate compound of the present invention include ethanediol dimethanesulfonate, ethanediol diethanesulfonate, ethanediol dipropanesulfonate, ethanediol dibutanesulfonate, ethanediol bis (trifluoromethanesulfonate), ethanediol bis (pentafluoro). Ethane sulfonate), ethanediol bis (heptafluoropropane sulfonate), ethanediol bis (perfluorobutane sulfonate), ethanediol bis (perfluoropentane sulfonate), ethanediol bis (perfluorohexane sulfonate), ethanediol bis (perfluoro) Octanesulfonate), ethanediol bis (perfluoro-1-methylethanesulfonate), ethanediol bis ( -Fluoro-1,1-dimethylethanesulfonate), ethanediol bis (perfluoro-3-methylbutanesulfonate), ethanediol di (fluoromethanesulfonate), ethanediol bis (difluoromethanesulfonate), ethanediol di (2-fluoro) Ethanesulfonate), ethanediol bis (1,1-difluoroethanesulfonate), ethanediol bis (1,2-difluoroethanesulfonate), ethanediol bis (2,2-difluoroethanesulfonate), ethanediol bis (1,1,2- Trifluoroethanesulfonate), ethanediol bis (1,2,2-trifluoroethanesulfonate), ethanediol bis (2,2,2-trifluoroethanesulfonate), ethanediol bis 1,1,2,2-tetrafluoroethanesulfonate), ethanediol bis (1,2,2,2-tetrafluoroethanesulfonate), ethanediol di (1-fluoro-1-methylethanesulfonate), ethanediol bis (1,2,2,2-tetrafluoro-1-methylethanesulfonate), ethanediol bis (1,1-difluoro-2-methylpropanesulfonate), ethanediol bis (1,2,2,3,3, 3-hexafluoro-1-methylpropanesulfonate), ethanediol di (2-fluoro-1-fluoromethylethanesulfonate), ethanediol bis (2,2,2-trifluoro-1-trifluoromethylethanesulfonate), Ethanediol bis (1-trifluoromethylethanesulfonate), Ethanediol disulfonates such as ethanediol di (1-methyl-1-trifluoromethylethanesulfonate), ethanediol bis (1-trifluoromethylhexanesulfonate);

1,2-propanediol dimethanesulfonate, 1,2-propanediol diethanesulfonate, 1,2-propanediol dipropanesulfonate, 1,2-propanediol dibutanesulfonate, 1,2-propanediol bis (trifluoromethane) Sulfonate), 1,2-propanediol bis (pentafluoroethane sulfonate), 1,2-propanediol bis (heptafluoropropane sulfonate), 1,2-propanediol bis (perfluorobutane sulfonate), 1,2-propane Diol bis (perfluoropentane sulfonate), 1,2-propanediol bis (perfluorohexane sulfonate), 1,2-propanediol bis (perfluorooctane sulfonate), 1,2-propanediol Rubis (perfluoro-1-methylethane sulfonate), 1,2-propanediol bis (perfluoro-1,1-dimethylethane sulfonate), 1,2-propanediol bis (perfluoro-3-methylbutane sulfonate), 1,2-propanediol di (fluoromethanesulfonate), 1,2-propanediol bis (difluoromethanesulfonate), 1,2-propanediol di (2-fluoroethanesulfonate), 1,2-propanediol bis (1 , 1-difluoroethanesulfonate), 1,2-propanediol bis (1,2-difluoroethanesulfonate), 1,2-propanediol bis (2,2-difluoroethanesulfonate), 1,2-propanediol bis (1,1 , 2-Trifluoroethane Sulfonate), 1,2-propanediol bis (1,2,2-trifluoroethanesulfonate), 1,2-propanediol bis (2,2,2-trifluoroethanesulfonate), 1,2-propanediol bis (1,1,2,2-tetrafluoroethane sulfonate), 1,2-propanediol bis (1,2,2,2-tetrafluoroethane sulfonate), 1,2-propanediol di (1-fluoro-1) -Methylethanesulfonate), 1,2-propanediol bis (1,2,2,2-tetrafluoro-1-methylethanesulfonate), 1,2-propanediol bis (1,1-difluoro-2-methylpropane) Sulfonate), 1,2-propanediol bis (1,2,2,3,3,3-hexafluoro-1-methylpro Pansulfonate), 1,2-propanediol di (2-fluoro-1-fluoromethylethanesulfonate), 1,2-propanediol bis (2,2,2-trifluoro-1-trifluoromethylethanesulfonate), 1,2-propanediol bis (1-trifluoromethylethanesulfonate), 1,2-propanediol di (1-methyl-1-trifluoromethylethanesulfonate), 1,2-propanediol bis (1-trifluoro 1,2-propanediol disulfonates such as methyl hexanesulfonate);

1,3-propanediol dimethanesulfonate, 1,3-propanediol diethanesulfonate, 1,3-propanediol dipropanesulfonate, 1,3-propanediol dibutanesulfonate, 1,3-propanediol bis (trifluoromethane) Sulfonate), 1,3-propanediol bis (pentafluoroethane sulfonate), 1,3-propanediol bis (heptafluoropropane sulfonate), 1,3-propanediol bis (perfluorobutane sulfonate), 1,3-propane Diol bis (perfluoropentane sulfonate), 1,3-propanediol bis (perfluorohexane sulfonate), 1,3-propanediol bis (perfluorooctane sulfonate), 1,3-propanediol Rubis (perfluoro-1-methylethane sulfonate), 1,3-propanediol bis (perfluoro-1,1-dimethylethane sulfonate), 1,3-propanediol bis (perfluoro-3-methylbutane sulfonate), 1,3-propanediol di (fluoromethanesulfonate), 1,3-propanediol bis (difluoromethanesulfonate), 1,3-propanediol di (2-fluoroethanesulfonate), 1,3-propanediol bis (1 , 1-difluoroethanesulfonate), 1,3-propanediol bis (1,2-difluoroethanesulfonate), 1,3-propanediol bis (2,2-difluoroethanesulfonate), 1,3-propanediol bis (1,1 , 2-Trifluoroethane Sulfonate), 1,3-propanediol bis (1,2,2-trifluoroethanesulfonate), 1,3-propanediol bis (2,2,2-trifluoroethanesulfonate), 1,3-propanediol bis (1,1,2,2-tetrafluoroethane sulfonate), 1,3-propanediol bis (1,2,2,2-tetrafluoroethane sulfonate), 1,3-propanediol di (1-fluoro-1) -Methylethanesulfonate), 1,3-propanediol bis (1,2,2,2-tetrafluoro-1-methylethanesulfonate), 1,3-propanediol bis (1,1-difluoro-2-methylpropane) Sulfonate), 1,3-propanediol bis (1,2,2,3,3,3-hexafluoro-1-methylpro Pansulfonate), 1,3-propanediol di (2-fluoro-1-fluoromethylethanesulfonate), 1,3-propanediol bis (2,2,2-trifluoro-1-trifluoromethylethanesulfonate), 1,3-propanediol bis (1-trifluoromethylethanesulfonate), 1,3-propanediol di (1-methyl-1-trifluoromethylethanesulfonate), 1,3-propanediol bis (1-trifluoro 1,3-propanediol disulfonates such as methyl hexanesulfonate);

1,2-butanediol dimethanesulfonate, 1,2-butanediol diethanesulfonate, 1,2-butanediol bis (trifluoromethanesulfonate), 1,2-butanediol bis (pentafluoroethanesulfonate), 1,2 -Butanediol bis (heptafluoropropane sulfonate), 1,2-butanediol bis (perfluorobutane sulfonate), 1,2-butanediol bis (perfluoro-1-methylethane sulfonate), 1,2-butanediol bis (Perfluoro-1,1-dimethylethanesulfonate), 1,2-butanediol di (fluoromethanesulfonate), 1,2-butanediol bis (difluoromethanesulfonate), 1,2-butanediol di (2-fluoro) Ethanesulfonate ), 1,2-butanediol bis (2,2-difluoroethanesulfonate), 1,2-butanediol bis (2,2,2-trifluoroethanesulfonate), 1,2-butanediol di (1-fluoro-) 1-methylethanesulfonate), 1,2-butanediol di (2-fluoro-1-fluoromethylethanesulfonate), 1,2-butanediol bis (2,2,2-trifluoro-1-trifluoromethylethane) Sulfonate), 1,2-butanediol bis (1-trifluoromethylethanesulfonate), 1,2-butanediol di (1-methyl-1-trifluoromethylethanesulfonate), 1,2-butanediol bis (1 1,2-butanediol disulfonates such as -trifluoromethylhexanesulfonate)

1,3-butanediol dimethanesulfonate, 1,3-butanediol diethanesulfonate, 1,3-butanediol bis (trifluoromethanesulfonate), 1,3-butanediol bis (pentafluoroethanesulfonate), 1,3 -Butanediol bis (heptafluoropropane sulfonate), 1,3-butanediol bis (perfluorobutane sulfonate), 1,3-butanediol bis (perfluoro-1-methylethane sulfonate), 1,3-butanediol bis (Perfluoro-1,1-dimethylethanesulfonate), 1,3-butanediol di (fluoromethanesulfonate), 1,3-butanediol bis (difluoromethanesulfonate), 1,3-butanediol di (2-fluoro) Ethanesulfonate ), 1,3-butanediol bis (2,2-difluoroethanesulfonate), 1,3-butanediol bis (2,2,2-trifluoroethanesulfonate), 1,3-butanediol di (1-fluoro-) 1-methylethanesulfonate), 1,3-butanediol di (2-fluoro-1-fluoromethylethanesulfonate), 1,3-butanediol bis (2,2,2-trifluoro-1-trifluoromethylethane) Sulfonate), 1,3-butanediol bis [(1-trifluoromethyl) ethanesulfonate], 1,3-butanediol di (1-methyl-1-trifluoromethylethanesulfonate), 1,3-butanediol bis 1,3-butanediol disulfonate such as (1-trifluoromethylhexanesulfonate) Kind;

1,4-butanediol dimethanesulfonate, 1,4-butanediol diethanesulfonate, 1,4-butanediol dipropanesulfonate, 1,4-butanediol dibutanesulfonate, 1,4-butanediol bis (trifluoromethane Sulfonate), 1,4-butanediol bis (pentafluoroethane sulfonate), 1,4-butanediol bis (heptafluoropropane sulfonate), 1,4-butanediol bis (perfluorobutane sulfonate), 1,4-butane Diol bis (perfluoropentane sulfonate), 1,4-butanediol bis (perfluorohexane sulfonate), 1,4-butanediol bis (perfluorooctane sulfonate), 1,4-butanediol bis (perfluoro- -Methylethanesulfonate), 1,4-butanediol bis (perfluoro-1,1-dimethylethanesulfonate), 1,4-butanediol bis (perfluoro-3-methylbutanesulfonate), 1,4-butanediol Di (fluoromethanesulfonate), 1,4-butanediol bis (difluoromethanesulfonate), 1,4-butanediol di (2-fluoroethanesulfonate), 1,4-butanediol bis (1,1-difluoroethanesulfonate) 1,4-butanediol bis (1,2-difluoroethanesulfonate), 1,4-butanediol bis (2,2-difluoroethanesulfonate), 1,4-butanediol bis (1,1,2-trifluoroethane) Sulfonate), 1,4-butanediol bis 1,2,2-trifluoroethanesulfonate), 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate), 1,4-butanediol bis (1,1,2,2-tetrafluoro) Ethanesulfonate), 1,4-butanediol bis (1,2,2,2-tetrafluoroethanesulfonate), 1,4-butanediol di (1-fluoro-1-methylethanesulfonate), 1,4-butane Diol bis (1,2,2,2-tetrafluoro-1-methylethane sulfonate), 1,4-butanediol bis (1,1-difluoro-2-methylpropane sulfonate), 1,4-butanediol bis ( 1,2,2,3,3,3-hexafluoro-1-methylpropanesulfonate), 1,4-butanediol di (2-fluoro) -1-fluoromethylethanesulfonate), 1,4-butanediol bis (2,2,2-trifluoro-1-trifluoromethylethanesulfonate), 1,4-butanediol bis (1-trifluoromethylethanesulfonate) 1,4-butanediol disulfonate (1,4-butanediol di (1-methyl-1-trifluoromethylethanesulfonate), 1,4-butanediol bis (1-trifluoromethylhexanesulfonate), etc.) Kind;

1,4-benzenediol dimethanesulfonate, 1,4-benzenediol diethanesulfonate, 1,4-benzenediol bis (trifluoromethanesulfonate), 1,4-benzenediol bis (pentafluoroethanesulfonate), 1,4 -Benzenediol bis (heptafluoropropane sulfonate), 1,4-benzenediol bis (perfluorobutane sulfonate), 1,4-benzenediol bis (perfluoro-1-methylethane sulfonate), 1,4-benzenediol bis (Perfluoro-1,1-dimethylethanesulfonate), 1,4-benzenediol di (fluoromethanesulfonate), 1,4 difluoromethanesulfonate), 1,4-benzenediol di (2-fluoroethanesulfonate) 1,4-benzenediol bis (2,2-difluoroethanesulfonate), 1,4-benzenediol bis (2,2,2-trifluoroethanesulfonate), 1,4-benzenediol di (1-fluoro-1) -Methylethanesulfonate), 1,4-benzenediol di (2-fluoro-1-fluoromethylethanesulfonate), 1,4-benzenediol bis (2,2,2-trifluoro-1-trifluoromethylethanesulfonate) ), 1,4-benzenediol bis (1-trifluoromethylethanesulfonate), 1,4-benzenediol di (1-methyl-1-trifluoromethylethanesulfonate), 1,4-benzenediol bis (1- 1,4-benzenediol such as trifluoromethylhexanesulfonate) Such as disulfonate compounds, and the like.

  Among these, R having 1 to 2 carbon atoms is preferable. For example, ethanediol dimethanesulfonate, ethanediol diethanesulfonate, ethanediol bis (trifluoromethanesulfonate), ethanediol bis (pentafluoroethanesulfonate), ethanediol di (fluoromethanesulfonate), ethanediol bis (difluoromethanesulfonate) Ethanediol disulfonates such as ethanediol di (2-fluoroethanesulfonate), ethanediol bis (2,2-difluoroethanesulfonate), ethanediol bis (2,2,2-trifluoroethanesulfonate);

1,2-propanediol dimethanesulfonate, 1,2-propanediol diethanesulfonate, 1,2-propanediol bis (trifluoromethanesulfonate), 1,2-propanediol bis (pentafluoroethanesulfonate), 1,2 -Propanediol di (fluoromethanesulfonate), 1,2-propanediol bis (difluoromethanesulfonate), 1,2-propanediol di (2-fluoroethanesulfonate), 1,2-propanediol bis (2,2- 1,2-propanediol disulfonates such as difluoroethanesulfonate), 1,2-propanediol bis (2,2,2-trifluoroethanesulfonate);

1,3-propanediol dimethanesulfonate, 1,3-propanediol diethanesulfonate, 1,3-propanediol bis (trifluoromethanesulfonate), 1,3-propanediol bis (pentafluoroethanesulfonate), 1,3 -Propanediol di (fluoromethanesulfonate), 1,3-propanediol bis (difluoromethanesulfonate), 1,3-propanediol di (2-fluoroethanesulfonate), 1,3-propanediol bis (2,2- 1,3-propanediol disulfonates such as difluoroethanesulfonate), 1,3-propanediol bis (2,2,2-trifluoroethanesulfonate);

1,2-butanediol dimethanesulfonate, 1,2-butanediol diethanesulfonate, 1,2-butanediol bis (trifluoromethanesulfonate), 1,2-butanediol bis (pentafluoroethanesulfonate), 1,2 -Butanediol di (fluoromethanesulfonate), 1,2-butanediol bis (difluoromethanesulfonate), 1,2-butanediol di (2-fluoroethanesulfonate), 1,2-butanediol bis (2,2- 1,2-butanediol disulfonates such as difluoroethanesulfonate), 1,2-butanediol bis (2,2,2-trifluoroethanesulfonate);

1,3-butanediol dimethanesulfonate, 1,3-butanediol diethanesulfonate, 1,3-butanediol bis (trifluoromethanesulfonate), 1,3-butanediol bis (pentafluoroethanesulfonate), 1,3 -Butanediol di (fluoromethanesulfonate), 1,3-butanediol bis (difluoromethanesulfonate), 1,3-butanediol di (2-fluoroethanesulfonate), 1,3-butanediol bis (2,2- 1,3-butanediol disulfonates such as difluoroethanesulfonate), 1,3-butanediol bis (2,2,2-trifluoroethanesulfonate);

1,4-butanediol dimethanesulfonate, 1,4-butanediol diethanesulfonate, 1,4-butanediol bis (trifluoromethanesulfonate), 1,4-butanediol bis (pentafluoroethanesulfonate), 1,4 -Butanediol di (fluoromethanesulfonate), 1,4-butanediol bis (difluoromethanesulfonate), 1,4-butanediol di (2-fluoroethanesulfonate), 1,4-butanediol bis (2,2- Preferred examples include 1,4-butanediol disulfonates such as difluoroethanesulfonate) and 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate).

  Further, among these, a C 1-2 aliphatic saturated hydrocarbon group in which R is fluorine-substituted is particularly preferable. Examples of these are ethanediol bis (trifluoromethanesulfonate), ethanediol bis (pentafluoroethanesulfonate), ethanediol di (fluoromethanesulfonate), ethanediol di (2-fluoroethanesulfonate), ethanediol bis (2, Ethanediol disulfonates such as 2,2-trifluoroethanesulfonate);

1,2-propanediol bis (trifluoromethanesulfonate), 1,2-propanediol bis (pentafluoroethanesulfonate), 1,2-propanediol di (fluoromethanesulfonate), 1,2-propanediol di (2- 1,2-propanediol disulfonates such as fluoroethanesulfonate), 1,2-propanediol bis (2,2,2-trifluoroethanesulfonate);

1,3-propanediol bis (trifluoromethanesulfonate), 1,3-propanediol bis (pentafluoroethanesulfonate), 1,3-propanediol di (2-fluoroethanesulfonate), 1,3-propanediol bis ( 1,3-propanediol disulfonates such as 2,2,2-trifluoroethanesulfonate);

1,2-butanediol bis (trifluoromethanesulfonate), 1,2-butanediol bis (pentafluoroethanesulfonate), 1,2-butanediol di (fluoromethanesulfonate), 1,2-butanediol di (2- 1,2-butanediol disulfonates such as fluoroethanesulfonate), 1,2-butanediol bis (2,2,2-trifluoroethanesulfonate);

1,3-butanediol bis (trifluoromethanesulfonate), 1,3-butanediol bis (pentafluoroethanesulfonate), 1,3-butanediol di (fluoromethanesulfonate), 1,3-butanediol di (2- 1,3-butanediol disulfonates such as fluoroethanesulfonate), 1,3-butanediol bis (2,2,2-trifluoroethanesulfonate);

1,4-butanediol bis (trifluoromethanesulfonate), 1,4-butanediol bis (pentafluoroethanesulfonate), 1,4-butanediol di (fluoromethanesulfonate), 1,4-butanediol di (2- 1,4-butanediol disulfonates such as fluoroethanesulfonate) and 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate).

These sulfonate compounds are not too large in molecular weight, are easily dissolved in a non-aqueous electrolyte, and act on the positive electrode and the negative electrode, so that the continuous charge characteristics and cycle characteristics of a high-voltage lithium secondary battery are particularly improved.
Moreover, the sulfonate compound of this invention mentioned above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

[1-2. composition]
The non-aqueous electrolyte in the present invention contains the sulfonate compound of the present invention, but the concentration thereof is arbitrary as long as the effects of the present invention are not significantly impaired. However, the concentration of the sulfonate compound of the present invention in the non-aqueous electrolyte in the present invention is usually 0.01% by weight or more, preferably 0.1% by weight or more, and usually 10% by weight or less, preferably 5% by weight. Hereinafter, it is more preferably 3% by weight or less, and further preferably 2% by weight or less. Below the lower limit of this range, the non-aqueous electrolyte in the present invention may not be able to improve the continuous charge characteristics / cycle characteristics. On the other hand, if the upper limit of this range is exceeded, a thick film is formed on the negative electrode, and since this film has a high resistance, it becomes difficult for Li ions to move between the non-aqueous electrolyte and the negative electrode, resulting in a battery with rate characteristics, etc. There is a risk that the characteristics will deteriorate. In addition, when using together 2 or more types of sulfonate compounds of this invention, it is made for the sum total of the density | concentration of the sulfonate compound to be used to be in the said range.

[2. Nonaqueous solvent]
There is no restriction | limiting in particular about a non-aqueous solvent, Although a well-known non-aqueous solvent can be used arbitrarily, Usually, an organic solvent is used. Examples of non-aqueous solvents include chain carbonates, cyclic carbonates, chain esters, cyclic esters (lactone compounds), chain ethers, cyclic ethers, sulfur-containing organic solvents, and the like. Among them, as a solvent that exhibits high ionic conductivity, chain carbonates, cyclic carbonates, chain esters, cyclic esters, chain ethers, and cyclic ethers are usually preferable.

Specific examples of the chain carbonates include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate.
Specific examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate and the like.

Furthermore, specific examples of the chain esters include methyl formate, methyl acetate, methyl propionate and the like.
Specific examples of cyclic esters include γ-butyrolactone and γ-valerolactone.

Furthermore, specific examples of chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether and the like.
Specific examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane and the like.

  Furthermore, specific examples of the sulfur-containing organic solvent include sulfolane and dimethyl sulfoxide.

  Furthermore, the non-aqueous solvent may be used alone or in combination of two or more in any combination and ratio. However, it is preferable to use a mixture of two or more non-aqueous solvents so as to exhibit desired characteristics, that is, continuous charge characteristics. In particular, it is preferable to mainly consist of cyclic carbonates and chain carbonates or cyclic esters. Here, “being mainly” specifically means that the non-aqueous solvent contains a total of 70% by weight or more of cyclic carbonates and chain carbonates or cyclic esters.

  When two or more kinds of non-aqueous solvents are used in combination, examples of preferable combinations include binary solvents such as ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and γ-butyrolactone; ethylene carbonate and dimethyl carbonate And ternary solvents such as ethylene methyl carbonate, ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. Nonaqueous solvents mainly containing these are preferably used because they satisfy various properties in a well-balanced manner.

  When an organic solvent is used as the non-aqueous solvent, the carbon number of the organic solvent is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 3 or more, usually 13 or less, preferably 7 or less. It is. If the number of carbon atoms is too large, the solubility of the electrolyte in the electrolytic solution may be deteriorated, and the effect of the present invention of improving the cycle characteristics may not be sufficiently exhibited. On the other hand, if the carbon number is too small, the volatility is increased, which may cause an increase in the internal pressure of the battery, which is not preferable.

  Furthermore, the molecular weight of the organic solvent used as the non-aqueous solvent is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 50 or more, preferably 80 or more, and usually 250 or less, preferably 150 or less. If the molecular weight is too large, the solubility of the electrolyte in the electrolytic solution is deteriorated and the viscosity is also increased. Therefore, the effect of the present invention of improving the cycle characteristics may not be sufficiently exhibited. On the other hand, if the molecular weight is too small, the volatility is increased, which causes an increase in the internal pressure of the battery, which is not preferable.

Moreover, when using the binary or more nonaqueous solvent which used together 2 or more types of nonaqueous solvent containing cyclic carbonate, the ratio of the cyclic carbonate in the binary water or more nonaqueous solvent is 10 volume% or more normally. It is preferably 15% by volume or more, more preferably 20% by volume or more, and usually 60% by volume or less, preferably 50% by volume or less, more preferably 40% by volume or less. If the lower limit of the above range is not reached, the lithium salt is less likely to dissociate and the conductivity is reduced, so the high load capacity tends to decrease.If the upper limit is exceeded, the viscosity becomes too high and Li ions are difficult to move, resulting in a high load. Capacity tends to decrease.
However, when γ-butyrolactone is used, its concentration is preferably 20% by weight or less.

[3. Electrolytes]
There is no restriction | limiting in particular about electrolyte, Although a well-known thing can be used arbitrarily if it is used as an electrolyte of a lithium secondary battery, Usually, lithium salt is used.
As the lithium salt used for the electrolyte, either an inorganic lithium salt or an organic lithium salt may be used.

Examples of inorganic lithium salts include inorganic fluoride salts such as LiPF ₆ , LiAsF ₆ , LiBF ₄ and LiSbF ₆ ; inorganic chloride salts such as LiAlCl ₄ ; perhalogenates such as LiClO ₄ , LiBrO ₄ and LiIO _4. Etc.
Examples of organic lithium salts include perfluoroalkane sulfonates such as CF ₃ SO ₃ Li and C ₄ F ₉ SO ₃ Li; perfluoroalkane carboxylates such as CF ₃ COOLi; (CF ₃ CO) Perfluoroalkanecarbonimide salts such as ₂ NLi; fluorine-containing organic lithium salts such as perfluoroalkanesulfonimide salts such as (CF ₃ SO ₂ ) ₂ NLi and (C ₂ F ₅ SO ₂ ) ₂ NLi.

Among these, LiPF ₆ , LiBF ₄ , CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, and the like are preferable because they are easily soluble in non-aqueous solvents and exhibit a high degree of dissociation.
In addition, electrolyte may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
In particular, the combined use of LiPF ₆ and LiBF ₄ or the combined use of LiPF ₆ and (CF ₃ SO ₂ ) ₂ NLi is preferable because it has an effect of improving the continuous charge characteristics.

  Furthermore, the concentration of the electrolyte in the non-aqueous electrolyte is arbitrary as long as the effects of the present invention are not significantly impaired, but usually 0.5 mol / L or more, preferably 0.75 mol / L with respect to the non-aqueous electrolyte. In addition, it is usually 2 mol / L or less, preferably 1.75 mol / L or less. If the concentration of the electrolyte is too low, the electric conductivity of the non-aqueous electrolyte may be insufficient. On the other hand, if the concentration of the electrolyte is too high, the electrical conductivity is lowered due to an increase in viscosity, and precipitation at a low temperature is likely to occur, and the performance of the lithium secondary battery tends to be lowered.

[4. Film-forming agent]
The nonaqueous electrolytic solution in the present invention preferably contains an unsaturated carbonate as a film forming agent for the purpose of forming a film on the negative electrode and improving battery characteristics.
The unsaturated carbonate is not particularly limited as long as it is a carbonate having a carbon-carbon unsaturated bond, and any unsaturated carbonate can be used. Examples thereof include carbonates having an aromatic ring and carbonates having carbon-carbon unsaturated bonds such as carbon-carbon double bonds and carbon-carbon triple bonds.

  Specific examples of the unsaturated carbonates include vinylene carbonate derivatives such as vinylene carbonate, methyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, phenyl vinylene carbonate, 1,2-diphenyl vinylene carbonate; -Ethylene carbonate derivatives substituted with a substituent having a carbon-carbon unsaturated bond such as divinylethylene carbonate, phenylethylene carbonate, 1,2-diphenylethylene carbonate; diphenyl carbonate, methylphenyl carbonate, t-butylphenyl carbonate, etc. Phenyl carbonates; vinyl carbonates such as divinyl carbonate and methyl vinyl carbonate; diallyl carbonate, allyl methyl carbonate Allyl carbonate such as theft and the like.

Among these, vinylene carbonate derivatives and ethylene carbonate derivatives substituted with a substituent having a carbon-carbon unsaturated bond are preferable.
In particular, vinylene carbonate, 1,2-diphenyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, and vinyl ethylene carbonate are more preferable.
By using these unsaturated carbonates, a stable interface protective film is formed on the negative electrode, so that the cycle characteristics of the lithium secondary battery are improved.

In addition, unsaturated carbonates may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The carbon number of the unsaturated carbonate is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 3 or more, and usually 20 or less, preferably 15 or less. If the upper limit of the above range is exceeded, the solubility in the electrolytic solution tends to decrease.

  Furthermore, the molecular weight of the unsaturated carbonates is arbitrary as long as the effects of the present invention are not significantly impaired. The preferred range of the molecular weight of the unsaturated carbonate is usually 80 or more, and usually 250 or less, preferably 150 or less. If the molecular weight is too large, the solubility in the electrolytic solution is lowered, and there is a possibility that the effect of the present invention of improving the cycle characteristics cannot be sufficiently exhibited.

  Further, the concentration of unsaturated carbonates in the non-aqueous electrolytic solution is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably It is 0.3% by weight or more, usually 10% by weight or less, preferably 7% by weight or less, more preferably 5% by weight or less. If the concentration of unsaturated carbonates is too high, the film formed on the negative electrode becomes thick and becomes resistive, which may reduce battery capacity. In addition, the amount of gas generated increases under high temperature conditions, which may further increase resistance and decrease the capacity. On the other hand, if the concentration is too small, the effects of the present invention may not be sufficiently exhibited. In addition, when using 2 or more types of unsaturated carbonate together, it is made for the sum total of the density | concentration of the used unsaturated carbonate to be in the said range.

Here, the reason why the nonaqueous electrolytic solution in the present invention preferably contains an unsaturated carbonate will be described. A part or all of the sulfonate compound of the present invention is decomposed on the negative electrode during initial charging to form a film. Thereby, since the subsequent reductive decomposition reaction of the nonaqueous solvent can be suppressed, the cycle characteristics of the lithium secondary battery are improved.
However, since the film formed from a sulfonate compound has a relatively high resistance, the capacity retention rate during the charge / discharge cycle may be reduced depending on the charge / discharge rate.

  On the other hand, when unsaturated carbonates are included in the non-aqueous electrolyte, the sulfonate compound of the present invention and unsaturated carbonates are reduced together in the initial charging, and therefore both derived. A hybrid coating is formed on the negative electrode. Since this hybrid film has low resistance and is excellent in thermal stability and solvent stability, this leads to an improvement in the cycle characteristics of the lithium secondary battery of the present invention.

[5. Other auxiliaries]
The non-aqueous electrolyte solution in the present invention may contain other auxiliary agents for the purpose of improving the wettability, overcharge characteristics, etc. of the non-aqueous electrolyte solution as long as the effects of the present invention are not significantly impaired.
Examples of auxiliaries include acid anhydrides such as maleic anhydride, succinic anhydride, and glutaric anhydride; carboxylic acid esters such as vinyl acetate, divinyl adipate, and allyl acetate; diphenyl disulfide, 1,3-propane sultone, Sulfur-containing compounds such as 1,4-butane sultone, dimethyl sulfone, divinyl sulfone, dimethyl sulfite, ethylene sulfite, 1,4-butanediol dimethanesulfonate, methyl methanesulfonate, 2-propynyl methanesulfonate; t- Aromatic compounds such as butylbenzene, biphenyl, o-terphenyl, 4-fluorobiphenyl, fluorobenzene, 2,4-difluorobenzene, cyclohexylbenzene, diphenyl ether, 2,4-difluoroanisole, trifluoromethylbenzene and the fragrance Such as those compounds substituted with fluorine atom.
Moreover, 1 type may be used independently for an adjuvant, and 2 or more types may be used together by arbitrary combinations and a ratio.

The concentration of the auxiliary agent in the non-aqueous electrolyte is arbitrary as long as the present invention does not significantly impair the effects of the present invention, but is usually 0.01% by weight or more, preferably 0.05% by weight or more. It is 10% by weight or less, preferably 5% by weight or less.
In addition, when using 2 or more types of adjuvants together, it is made for the sum total of these density | concentrations to be settled in the said range.

[6. Non-aqueous electrolyte state]
The nonaqueous electrolytic solution in the present invention is usually present in a liquid state when used in the lithium secondary battery of the present invention. For example, it may be gelled with a polymer to form a semi-solid electrolyte. The polymer used for the gelation is arbitrary, and examples thereof include polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyethylene oxide, polyacrylate, and polymethacrylate. In addition, the polymer | macromolecule used for gelatinization may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Moreover, when using a non-aqueous electrolyte as a semi-solid electrolyte, the ratio of the non-aqueous electrolyte in the semi-solid electrolyte is arbitrary as long as the effects of the present invention are not significantly impaired. As a suitable range, the ratio of the non-aqueous electrolyte to the total amount of the semisolid electrolyte is usually 30% by weight or more, preferably 50% by weight or more, more preferably 75% by weight or more, and usually 99.95. % By weight or less, preferably 99% by weight or less, more preferably 98% by weight or less. If the ratio of the non-aqueous electrolyte solution is too large, it may be difficult to hold the electrolyte solution, and liquid leakage may easily occur. Conversely, if it is too small, the charge / discharge efficiency and capacity may be insufficient.

[7. Method for producing non-aqueous electrolyte]
The non-aqueous electrolyte solution in the present invention can be prepared by dissolving the electrolyte, the sulfonate compound of the present invention, and if necessary, unsaturated carbonates and other auxiliary agents in a non-aqueous solvent.

  When preparing the non-aqueous electrolyte, each raw material of the non-aqueous electrolyte, that is, the electrolyte, the sulfonate compound of the present invention, the non-aqueous solvent, the unsaturated carbonates, and other auxiliary agents may be dehydrated in advance. preferable. The degree of dehydration is usually 50 ppm or less, preferably 30 ppm or less. In the present specification, ppm means a ratio based on weight.

If water is present in the non-aqueous electrolyte, electrolysis of water, reaction between water and lithium metal, hydrolysis of lithium salt, and the like may occur, which is not preferable.
The dehydration means is not particularly limited. For example, when the object to be dehydrated is a liquid such as a non-aqueous solvent, a molecular sieve or the like may be used. When the object to be dehydrated is a solid such as an electrolyte, it may be dried at a temperature lower than the temperature at which decomposition occurs.

[II. Lithium secondary battery]
The lithium secondary battery of the present invention includes the above-described non-aqueous electrolyte solution according to the present invention, a positive electrode, and a negative electrode. In addition, the lithium secondary battery of the present invention may have other configurations. For example, a lithium secondary battery usually includes a spacer.

[1. Positive electrode]
As long as the positive electrode can occlude and release lithium, any positive electrode can be used as long as the effects of the present invention are not significantly impaired.
Usually, a positive electrode having a positive electrode active material layer provided on a current collector is used. Note that the positive electrode may include other layers as appropriate.

[1-1. Positive electrode active material layer]
The positive electrode active material layer includes a positive electrode active material. The positive electrode active material is not limited as long as it can occlude and release lithium ions. Examples include oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides of transition metals and lithium, and sulfides of transition metals.

Specific examples of transition metal oxides include MnO, V ₂ O ₅ , V ₆ O ₁₃ , and TiO ₂ .
Specific examples of the composite oxide of transition metal and lithium include a lithium nickel composite oxide whose basic composition is LiNiO ₂ ; a lithium cobalt composite oxide whose basic composition is LiCoO ₂ ; a basic composition of LiMnO ₂ and LiMnO. _And lithium manganese composite oxide such as ₄ .
Further, specific examples of the transition metal sulfide include TiS ₂ and FeS.
Among these, a composite oxide of lithium and a transition metal is preferable because it can achieve both high capacity and high cycle characteristics of a lithium secondary battery.

  Further, in the above-described composite oxide of transition metal and lithium, some of the main transition metal atoms are Al, B, Ti, Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg. Replacing with other metals such as Ca and Ga is preferable because they can be stabilized. Of these, replacement with Al, Mg, Ca, Ti, Zr, Co, Ni, and Mn is particularly preferable because deterioration of the positive electrode at a high voltage is suppressed.

Furthermore, the surface of the composite oxide of transition metal and lithium described above is oxidized with metals such as Al, B, Ti, Zr, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Ca, and Ga. It is preferable to coat with an object because the oxidation reaction of the solvent at a high voltage is suppressed. Of these, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , and MgO are particularly preferable because they have high strength and exhibit a stable coating effect.
In addition, any one of these positive electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.

The specific surface area of the positive electrode active material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.1 m ² / g or more, preferably 0.2 m ² / g or more, and usually 10 m ² / g. Hereinafter, it is preferably 5.0 m ² / g or less, more preferably 3.0 m ² / g or less. If the specific surface area is too small, the rate characteristics and capacity may be reduced. If the specific surface area is too large, the positive electrode active material may cause an undesirable reaction with the non-aqueous electrolyte and the like, and the cycle characteristics may be deteriorated.

  Further, the average secondary particle size of the positive electrode active material is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.2 μm or more, preferably 0.3 μm or more, and usually 20 μm or less, preferably 10 μm or less. It is. If the average secondary particle size is too small, the cycle deterioration of the lithium secondary battery may be increased and handling may be difficult. If the average secondary particle size is too large, the internal resistance of the battery may be increased and output may be difficult to output.

  The thickness of the positive electrode active material layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and further preferably 40 μm or more. Usually, it is 200 micrometers or less, Preferably it is 150 micrometers or less, More preferably, it is 100 micrometers or less. If it is too thin, it becomes difficult to apply the coating and it is difficult to ensure uniformity, and the capacity of the lithium secondary battery of the present invention may be small. On the other hand, if it is too thick, there is a risk that the rate characteristics will deteriorate.

The positive electrode active material layer is formed by, for example, slurrying the above-described positive electrode active material, a binder (binder), and various auxiliary agents as necessary with a solvent to form a coating liquid, and collecting the coating liquid. It can be manufactured by applying to the body and drying. Further, for example, the above-described positive electrode active material may be roll-formed to form a sheet electrode, or may be formed into a pellet electrode by compression molding.
Hereinafter, a case where the slurry is applied to the positive electrode current collector and dried will be described.

  The binder is not particularly limited as long as it is a material that is stable with respect to the non-aqueous solvent used in the non-aqueous electrolyte solution or the solvent used during electrode production, but weather resistance, chemical resistance, heat resistance, difficulty It is preferable to select in consideration of flammability and the like. Specific examples of the binder include inorganic compounds such as silicate and water glass, alkane polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene , Polymers having a ring such as polymethylstyrene, polyvinylpyridine, poly-N-vinylpyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, Acrylic derivative polymers such as polymethacrylic acid and polyacrylamide; Fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride and polytetrafluoroethylene; CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; Polyvinyl chloride, halogen-containing polymers of polyvinylidene chloride; Le, polyvinyl alcohol polymers such as polyvinyl alcohol such as a conductive polymer such as polyaniline can be used.

In addition, mixtures of the above polymers, modified products, derivatives, random copolymers, alternating copolymers, graft copolymers, block copolymers, and the like can also be used as the binder.
Among these, preferred binders are a fluororesin and a CN group-containing polymer.
In addition, a binder may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  When a resin is used as the binder, the weight average molecular weight of the resin is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 10,000 or more, preferably 100,000 or more, and usually 300. 10,000 or less, preferably 1,000,000 or less. If the molecular weight is too low, the strength of the electrode tends to decrease. On the other hand, if the molecular weight is too high, the viscosity becomes high and it may be difficult to form an electrode.

  Furthermore, the amount of the binder used is arbitrary as long as the effects of the present invention are not significantly impaired. However, the positive electrode active material (in the case of use in the negative electrode, the negative electrode active material. Hereinafter, the positive electrode active material and the negative electrode active material are distinguished. Without being referred to, simply referred to as “active material”) is usually 0.1 parts by weight or more, preferably 1 part by weight or more, and usually 30 parts by weight or less, preferably 20 parts by weight. It is as follows. If the amount of the binder is too small, the strength of the electrode tends to decrease, and if the amount of the binder is too large, the ionic conductivity tends to decrease.

The electrode may contain various auxiliaries as described above. Examples of the auxiliary agent include a conductive material that increases the conductivity of the electrode, and a reinforcing material that improves the mechanical strength of the electrode.
Specific examples of the conductive material are not particularly limited as long as an appropriate amount can be mixed with the active material to impart conductivity. However, carbon powders such as acetylene black, carbon black, and graphite, and various metals are usually used. Examples include fibers and foils.

As specific examples of the reinforcing material, various inorganic, organic spherical, fibrous fillers and the like can be used.
In addition, these adjuvants etc. may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  The solvent for forming the slurry is not particularly limited in type as long as it is a solvent capable of dissolving or dispersing the active material, the binder, and auxiliary agents used as necessary. Either an aqueous solvent or an organic solvent may be used.

Examples of the aqueous solvent include water and alcohol.
On the other hand, examples of organic solvents include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like.

In addition, the solvent for forming these slurries may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
The active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.

[1-2. Current collector]
As a material for the current collector, a known material can be arbitrarily used, but usually a metal or an alloy is used. Specifically, examples of the current collector for the positive electrode include aluminum, nickel, and SUS (stainless steel). Among these, aluminum is preferable as the positive electrode current collector. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and ratios.

  Furthermore, in order to improve the binding effect between the current collector and the active material layer formed on the surface, it is preferable that the surface of these current collectors is roughened in advance. The surface roughening method includes blasting or rolling with a rough roll, and the surface of the current collector with a wire brush equipped with abrasive cloth paper, grindstone, emery buff, steel wire, etc. to which abrasive particles are fixed. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  Further, the shape of the current collector is arbitrary. For example, in order to reduce the weight of the battery, that is, to improve the energy density per weight, a perforated type current collector such as an expanded metal or a punching metal can be used. In this case, the weight can be freely changed by changing the aperture ratio. In addition, when a coating layer is formed on both surfaces of such a perforated current collector, the coating layer tends to be more difficult to peel due to the rivet effect of the coating layer through the hole, but the aperture ratio is too high. When it becomes high, the contact area between the coating layer and the current collector becomes small, so the adhesive strength is rather low.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary as long as the effects of the present invention are not significantly impaired, but it is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 50 μm or less. . If it is too thick, the capacity of the entire battery will be reduced. Conversely, if it is too thin, handling will be difficult.

[2. Negative electrode]
Any negative electrode can be used as long as it can occlude and release lithium as long as the effects of the present invention are not significantly impaired.
Usually, as in the case of the positive electrode, a negative electrode having a negative electrode active material layer provided on a current collector is used. Note that, similarly to the positive electrode, the negative electrode may include other layers as appropriate.

[2-1. Negative electrode active material]
The negative electrode active material is not particularly limited as long as it is a material capable of occluding and releasing lithium ions, and a known negative electrode active material can be arbitrarily used. For example, it is preferable to use carbonaceous materials such as coke, acetylene black, mesophase micro beads, and graphite; lithium metal; lithium alloys such as lithium-silicon and lithium-tin.

From the viewpoint of high capacity per unit weight and good safety, lithium alloys are particularly preferred, and from the viewpoint of good cycle characteristics and safety, it is particularly preferred to use a carbonaceous material.
In addition, a negative electrode active material may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Further, the particle size of the negative electrode active material is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 1 μm or more, preferably 15 μm in terms of excellent battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics. These are usually 50 μm or less, preferably about 30 μm or less.

  In addition, for example, those obtained by coating the above carbonaceous material with an organic substance such as pitch and then firing, those obtained by forming amorphous carbon on the surface using the CVD method, etc. It can be suitably used as a quality material. Here, organic substances used for coating include coal tar pitch from soft pitch to hard pitch; coal heavy oil such as dry distillation liquefied oil; straight heavy oil such as atmospheric residual oil and vacuum residual oil; crude oil And heavy petroleum oils such as cracked heavy oil (eg, ethylene heavy end) produced as a by-product during thermal decomposition of naphtha and the like. Moreover, what grind | pulverized the solid residue obtained by distilling these heavy oils at 200-400 degreeC to 1-100 micrometers can also be used. Furthermore, a vinyl chloride resin, a phenol resin, an imide resin, etc. can also be used.

  For example, the negative electrode active material layer can be formed into a sheet electrode by roll molding the negative electrode active material described above, or a pellet electrode by compression molding. Usually, as in the case of the positive electrode active material layer, The negative electrode active material, the binder, and, if necessary, various auxiliary agents and the like can be produced by applying a coating solution obtained by slurrying with a solvent onto a current collector and drying it. it can. As the solvent, binder, auxiliary agent and the like for forming the slurry, the same materials as those described above for the positive electrode active material can be used.

[2-2. Current collector]
As a material for the current collector of the negative electrode, a known material can be arbitrarily used. For example, a metal material such as copper, nickel, or SUS is used. Among these, copper is particularly preferable from the viewpoint of ease of processing and cost.

The negative electrode current collector is also preferably subjected to a roughening treatment in advance, as with the positive electrode current collector.
Further, like the positive electrode, the shape of the current collector is also arbitrary, and a perforated current collector such as expanded metal or punching metal can also be used. Moreover, the preferable thickness when using a thin film as a current collector is the same as that of the positive electrode.

[3. Spacer]
In order to prevent a short circuit, a spacer is usually interposed between the positive electrode and the negative electrode. The material and shape of the spacer are not particularly limited, but those that are stable with respect to the non-aqueous electrolyte described above, have excellent liquid retention properties, and can reliably prevent short-circuiting between electrodes are preferable.

As a material for the spacer, for example, polyolefin such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone and the like can be used, and polyolefin is preferable.
The spacer is preferably porous. In this case, the non-aqueous electrolyte is used by impregnating a porous spacer.

  The thickness of the spacer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably. Is 30 μm or less. If the spacer is too thin, the insulation and mechanical strength may be deteriorated. If the spacer is too thick, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole battery may be lowered. .

  Further, when a porous film is used as the spacer, the porosity of the spacer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 20% or more, preferably 35% or more, more preferably 45% or more. It is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too small, the membrane resistance increases and the rate characteristics tend to deteriorate. On the other hand, if it is too large, the mechanical strength of the film tends to decrease and the insulating property tends to decrease.

  Further, when a porous film is used as the spacer, the average pore diameter of the spacer is arbitrary as long as the effect of the present invention is not significantly impaired, but it is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.8. It is 05 μm or more. If it is too large, a short circuit is likely to occur, and if it is too small, the film resistance increases and the rate characteristics may deteriorate.

[4. Assembly of secondary battery]
The lithium secondary battery of the present invention is manufactured by assembling the above-described non-aqueous electrolyte solution according to the present invention, a positive electrode, a negative electrode, and a spacer used as necessary into an appropriate shape. Furthermore, other components such as an outer case can be used as necessary. Furthermore, the shape of the lithium secondary battery of the present invention is not particularly limited, and can be appropriately selected from various shapes generally employed according to the application. For example, a coin-type battery, a cylindrical battery, a square battery, etc. are raised. The method for assembling the battery is not particularly limited, and can be appropriately selected from various commonly used methods according to the shape of the target battery.

[5. Action]
By using the non-aqueous electrolyte containing the sulfonate compound of the present invention as described above for the lithium secondary battery of the present invention, the open circuit voltage between the battery terminals at 25 ° C. at the end of charging is usually 4.25V. As described above, even if charging is performed until the voltage is preferably 4.30 V or higher, and more preferably 4.40 V or higher, gas generation can be significantly suppressed, and deterioration in recovery capacity can be reduced.

[6. Others]
[6-1. Regarding the open circuit voltage between battery terminals at the end of charging]
In this specification, the open circuit voltage between battery terminals is a battery voltage in a state where no current flows in the circuit. Although the measuring method is arbitrary, it can measure with a normal charging / discharging apparatus, for example.

[6-2. About charging]
When charging a lithium secondary battery, the battery is generally charged in a state where a voltage drop of resistance is added. That is, the charging voltage is obtained by adding the product of the charging current and the resistance to the open circuit voltage between the battery terminals. Therefore, the difference between the charging voltage and the open circuit voltage between the battery terminals increases as the charging current increases and as the internal resistance of the lithium secondary battery or the resistance of the protection open circuit increases.

In the lithium secondary battery of the present invention, the charging method is not particularly limited and can be charged by any charging method. For example, constant current charging (CC charging), constant current-constant voltage charging (CCCV charging), pulse charging, reverse taper charging, or the like is used.
As for the end of charging, the charging may be performed for a predetermined time (for example, longer than the time required for calculation for completion of charging), or it may be detected that the charging current value has become a specified value or less. The voltage value may reach the specified value.

  In current lithium secondary batteries, the open circuit voltage between battery terminals at the end of charging is usually in the range of 4.08V to 4.20V. The higher the open circuit voltage between the battery terminals at the end of charging, the higher the capacity (mAh) of the lithium secondary battery. In addition, the higher the open circuit voltage between the battery terminals at the end of charging, the higher the voltage of the lithium secondary battery itself, so the weight energy density (mWh / kg) also increases, and the lithium secondary battery is light and long in duration. Can be obtained.

[6-3. mechanism]
Hereinafter, the mechanism that the inventor of the present invention infers that the effect of the present invention is obtained is not clear, but is considered as follows.
Conventionally, development of a lithium secondary battery capable of increasing the open circuit voltage between battery terminals at the end of charging has been desired. However, in the conventional technique, an electrolyte solution mainly on the positive electrode is used under a high voltage condition of 4.25 V or more. As a result, the cycle characteristics were low, and a practical secondary battery could not be obtained.
On the other hand, in the lithium secondary battery of the present invention, the sulfonate compound of the present invention forms a protective film on the positive electrode and can suppress the oxidation reaction of the non-aqueous electrolyte solution. It is considered that a lithium secondary battery excellent in continuous charge characteristics can be obtained.

  As described above, the sulfonate compound of the present invention forms a protective film on the positive electrode. In this case, the protective film includes chemical adsorption at the molecular level in addition to the case where the protective film is observed as a film. That is, since the sulfonate compound of the present invention acts as an acid and coats the base point of the positive electrode active material, it can suppress the decarboxylation reaction of the main solvent and suppress the generation of gas such as carbon dioxide. It is inferred that

  Therefore, if the gas is generated, the electrode is drained and the resistance increases, so that the charge / discharge cycle characteristics of the lithium secondary battery are deteriorated. However, in the lithium secondary battery of the present invention, the sulfonate of the present invention is used. It is presumed that the compound is adsorbed stably even under a high voltage condition of 4.25 V or higher, so that the charge / discharge cycle characteristics are improved.

  Furthermore, since the sulfonate compound of the present invention is susceptible to reduction, in the initial charging of the lithium secondary battery of the present invention, the sulfonate compound of the present invention is partially reduced at the negative electrode. The decomposition product at that time moves to the positive electrode, undergoes oxidation, and can form a stable film even under a high voltage condition of 4.25 V or higher. Therefore, since the decomposition of the subsequent main solvent is suppressed by the above-described coating, in the lithium secondary battery of the present invention, the generated gas under the continuous charge condition is reduced, and the capacity deterioration under the charge / discharge cycle is also reduced. Inferred.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples and comparative examples, and may be arbitrarily set without departing from the gist of the present invention. It can be implemented with deformation.

<Explanation of test operation>
[Production of positive electrode]
A mixture obtained by mixing 92 parts by weight of lithium cobaltate (LiCoO ₂ ), 4 parts by weight of polyvinylidene fluoride (hereinafter referred to as “PVdF”) and 4 parts by weight of acetylene black, and adding N-methylpyrrolidone to form a slurry. The positive electrode was obtained by applying and drying both sides of a current collector made of aluminum.

[Manufacture of negative electrode]
90 parts by weight of graphite powder and 10 parts by weight of PVdF were mixed, and a slurry obtained by adding N-methylpyrrolidone was applied to one side of a current collector made of copper and dried to obtain a negative electrode.

[Manufacture of lithium secondary batteries]
FIG. 1 shows a schematic cross-sectional view of lithium secondary batteries produced in Examples and Comparative Examples.
The above-described positive electrode, negative electrode, and a polyethylene biaxially stretched porous film (separator, spacer) having a film thickness of 16 μm, a porosity of 45%, and an average pore diameter of 0.05 μm were each coated and impregnated with an electrolyte solution described later. Thereafter, a negative electrode [2], a separator [3], a positive electrode [1], a separator [3], and a negative electrode [2] were laminated in this order. The battery element thus obtained was first sandwiched between polyethylene terephthalate (PET) films [4]. Next, positive and negative terminals were protruded from a laminate film [7] having resin layers formed on both sides of an aluminum foil and vacuum sealed to produce a sheet-like lithium secondary battery. Moreover, the lead [8] with a sealing material was attached to the terminal of a positive electrode and a negative electrode. Further, in order to improve the adhesion between the electrodes, the sheet-like battery was sandwiched between the silicon rubber [5] and the glass plate [6] and pressurized at a pressure of 3.4 × 10 ⁻⁴ Pa.

[Capacity evaluation]
The discharge rate per hour of lithium cobaltate was set to 160 mAh / g, and the rate was set by obtaining the discharge rate 1C from this and the amount of active material of the positive electrode of the lithium secondary battery for evaluation, and then a constant temperature bath at 25 ° C. In the middle, after constant current-constant voltage charge to 0.2 V at 0.2 C (hereinafter referred to as “CCCV charge” as appropriate), it was discharged to 3 V at 0.2 C, and an initial formation was performed. Subsequently, after CCCV charge to 4.4V at 0.7C, it discharged again to 3V at 0.2C, and the initial discharge capacity was obtained. Note that the cut current at the time of charging was 0.05C.

[4.35V continuous charge characteristics evaluation]
The battery for which the capacity evaluation test was completed was placed in a constant temperature bath at 60 ° C., charged at a constant current of 0.7 C, and switched to constant voltage charging when 4.35 V was reached. After charging for 7 days, the battery was cooled to 25 ° C., and the open circuit voltage between the battery terminals was measured. Next, the battery was immersed in an ethanol bath and the buoyancy was measured (Archimedes principle), and the amount of gas generated was determined from the buoyancy. In addition, in order to evaluate the degree of capacity deterioration after continuous charging, first discharge to 3V at 0.2C, then charge to 4.4V at 0.7C, and further discharge to 3V at 0.2C. The discharge capacity (recovery capacity) was measured, and the recovery capacity maintenance rate after continuous charging was determined according to the following formula. A larger value indicates less battery deterioration.

[4.45V continuous charge characteristics evaluation]
The battery for which the capacity evaluation test was completed was placed in a constant temperature bath at 60 ° C., charged at a constant current of 0.7 C, and switched to constant voltage charging when it reached 4.45V. After charging for 7 days, the battery was cooled to 25 ° C., and the open circuit voltage between the battery terminals was measured. Next, the battery was immersed in an ethanol bath and the buoyancy was measured (Archimedes principle), and the amount of gas generated was determined from the buoyancy.

[4.4V cycle characteristics evaluation]
50 cycles of charge / discharge cycles in which the battery for which the capacity evaluation test has been completed is CCCV charged to 4.4V at 0.7C (cut current is set to 0.05C) and CC discharged to 3V at 1C in a constant temperature bath at 25 ° C. Repeated. The capacity retention rate after 50 cycles was determined by the following formula. Moreover, the open circuit voltage between battery terminals was measured at the end of the first charge.

[4.2V cycle characteristics evaluation]
200 cycles of charge / discharge cycles in which the battery for which the capacity evaluation test has been completed was CCCV charged to 4.2V at 0.7C (cut current was set to 0.05C) and CC discharged to 3V at 1C in a 25 ° C constant temperature bath. Repeated. However, in this case, the rate was set by setting the discharge rate per hour of lithium cobaltate to 140 mAh / g and determining the discharge rate 1C from this and the amount of the active material of the positive electrode of the lithium secondary battery for evaluation. The capacity retention rate after 200 cycles was determined by the following formula. Moreover, the open circuit voltage between battery terminals was measured at the end of the first charge.

<Example 1>
A mixed solvent of ethylene carbonate (EC) is a cyclic carbonate and ethyl methyl carbonate is a chain carbonate (EMC) (volume mixing ratio of 1: 3) to, those of LiPF ₆ as the electrolyte was dissolved in a proportion of 1 mol / L Was used as a base electrolyte (I), and 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as a sulfonate compound was added to the base electrolyte (I) at a concentration of 1 with respect to the non-aqueous electrolyte. A non-aqueous electrolyte solution was added in such a way as to be in% by weight.

  Using the obtained non-aqueous electrolyte solution, a lithium secondary battery was produced according to the above-described method, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1. In Table 1, the numerical values described in parentheses in the columns of sulfonate compound, unsaturated carbonate and electrolyte represent the composition in the non-aqueous electrolyte. The numerical value described in parentheses in the non-aqueous solvent column represents the mixing ratio of the non-aqueous solvent.

<Example 2>
A nonaqueous system in which 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as a sulfonate compound is added to the base electrolyte solution (I) so that the concentration with respect to the nonaqueous electrolyte solution is 2% by weight. Using the electrolytic solution, a lithium secondary battery was prepared according to the above-described method, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Example 3>
1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as a sulfonate compound was added to the base electrolyte (I) so that the concentration with respect to the non-aqueous electrolyte was 0.5% by weight. Using a non-aqueous electrolyte, a lithium secondary battery was prepared according to the above-described method, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Example 4>
Using the non-aqueous electrolyte obtained by adding 1,4-butanediol dimethanesulfonate as the sulfonate compound to the base electrolyte (I) so that the concentration with respect to the non-aqueous electrolyte is 1% by weight, Therefore, a lithium secondary battery was produced, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Example 5>
Using a non-aqueous electrolyte solution in which 1,4-butanediolbis (trifluoromethanesulfonate) as a sulfonate compound was added to the base electrolyte solution (I) so that the concentration with respect to the non-aqueous electrolyte solution was 0.5% by weight. Then, a lithium secondary battery was prepared according to the method described above, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Comparative Example 1>
Using the base electrolyte (I) itself, a lithium secondary battery was prepared according to the above-described method, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Example 6>
1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as the sulfonate compound and vinylene carbonate (VC) as the unsaturated carbonate are added to the base electrolyte (I) with respect to the non-aqueous electrolyte. Using the non-aqueous electrolyte solution added so that the concentration is 1% by weight and 2% by weight, respectively, a lithium secondary battery is manufactured according to the above-described method, and 4.35V continuous charge characteristics evaluation and 4.45V continuous charge are performed. Characteristic evaluation was performed. The results are shown in Table 1.

<Example 7>
In the base electrolyte (I), 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as the sulfonate compound and vinylene carbonate as the unsaturated carbonates, respectively, with respect to the non-aqueous electrolyte Using the non-aqueous electrolyte added so as to be 2% by weight and 2% by weight, a lithium secondary battery was prepared according to the above-described method, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. I did it. The results are shown in Table 1.

<Example 8>
1,4-butanediol bis (2,2,2-trifluoroethane sulfonate) as the sulfonate compound and vinyl ethylene carbonate (VEC) as the unsaturated carbonate in the base electrolyte (I), a non-aqueous electrolyte A lithium secondary battery was prepared according to the above-described method using a non-aqueous electrolyte solution added so that the concentration with respect to 1 wt% and 2 wt% respectively, and 4.35 V continuous charge characteristics evaluation and 4.45 V continuous The charging characteristics were evaluated. The results are shown in Table 1.

<Example 9>
In the base electrolyte (I), 1,4-butanediol dimethanesulfonate as the sulfonate compound and vinylene carbonate as the unsaturated carbonate, so that the concentration with respect to the non-aqueous electrolyte is 1% by weight and 2% by weight, respectively. Using the non-aqueous electrolyte added to the battery, a lithium secondary battery was prepared according to the above-described method, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Example 10>
In the base electrolyte (I), 1,4-butanediol bis (trifluoromethanesulfonate) as the sulfonate compound, and vinylene carbonate as the unsaturated carbonates, the concentration with respect to the non-aqueous electrolyte is 0.5% by weight and 2%, respectively. A lithium secondary battery was prepared according to the above-described method using a non-aqueous electrolyte solution added so as to be in wt%, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Example 11>
In a mixed solvent (mixing volume ratio 1: 1: 1) of ethylene carbonate (EC), which is a cyclic carbonate, and ethyl methyl carbonate (EMC), which is a chain carbonate, and diethyl carbonate (DEC), 1 LiPF ₆ is used as an electrolyte. A base electrolyte (II) was dissolved at a rate of 25 mol / L, and 1,4-butanediolbis (2,2,2-trifluoroethanesulfonate) as a sulfonate compound was added to the base electrolyte (II). In addition, vinylene carbonate as an unsaturated carbonate was added so that the concentration with respect to the non-aqueous electrolyte solution was 1% by weight and 2% by weight, respectively, to obtain a non-aqueous electrolyte solution. Using the obtained non-aqueous electrolyte solution, a lithium secondary battery was produced according to the above-described method, and 4.35V continuous charge characteristic evaluation and 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Comparative Example 2>
A lithium secondary battery according to the above-described method using a non-aqueous electrolyte solution in which vinylene carbonate as an unsaturated carbonate is added to the base electrolyte solution (I) so that the concentration with respect to the non-aqueous electrolyte solution is 2% by weight. The 4.35V continuous charge characteristic evaluation and the 4.45V continuous charge characteristic evaluation were performed. The results are shown in Table 1.

<Example 12>
A non-aqueous system in which 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as a sulfonate compound is added to the base electrolyte (I) so that the concentration with respect to the non-aqueous electrolyte is 1% by weight. Using the electrolytic solution, a lithium secondary battery was produced according to the above-described method, and the 4.4 V cycle characteristics were evaluated. The results are shown in Table 2. In Table 2, the numerical values described in parentheses in the column of sulfonate compound, unsaturated carbonate and electrolyte represent the composition in the non-aqueous electrolyte. The numerical value described in parentheses in the non-aqueous solvent column represents the mixing ratio of the non-aqueous solvent.

<Example 13>
Using the non-aqueous electrolyte obtained by adding 1,4-butanediol dimethanesulfonate as the sulfonate compound to the base electrolyte (I) so that the concentration with respect to the non-aqueous electrolyte is 1% by weight, Therefore, a lithium secondary battery was prepared and evaluated for 4.4V cycle characteristics. The results are shown in Table 2.

<Comparative Example 3>
Using the base electrolyte (I) itself, a lithium secondary battery was produced according to the method described above, and the 4.4V cycle characteristics were evaluated. The results are shown in Table 2.

<Example 14>
In the base electrolyte (I), 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as the sulfonate compound and vinylene carbonate as the unsaturated carbonates, respectively, with respect to the non-aqueous electrolyte A lithium secondary battery was produced according to the above-described method using a non-aqueous electrolyte solution added so as to be 1 wt% and 2 wt%, and 4.4 V cycle characteristics were evaluated. The results are shown in Table 2.

<Example 15>
In the base electrolyte (I), 1,4-butanediol dimethanesulfonate as the sulfonate compound and vinylene carbonate as the unsaturated carbonate, so that the concentration with respect to the non-aqueous electrolyte is 1% by weight and 2% by weight, respectively. Using the non-aqueous electrolyte added to the battery, a lithium secondary battery was produced according to the method described above, and the 4.4 V cycle characteristics were evaluated. The results are shown in Table 2.

<Comparative Example 4>
A lithium secondary battery according to the above-described method using a non-aqueous electrolyte solution in which vinylene carbonate as an unsaturated carbonate is added to the base electrolyte solution (I) so that the concentration with respect to the non-aqueous electrolyte solution is 2% by weight. The 4.4V cycle characteristics were evaluated. The results are shown in Table 2.

<Comparative Example 5>
To the base electrolyte (I), cyclohexylbenzene as an additive in place of the sulfonate compound and vinylene carbonate as an unsaturated carbonate were added so that the concentrations with respect to the non-aqueous electrolyte were 1% by weight and 2% by weight, respectively. Using a non-aqueous electrolyte, a lithium secondary battery was prepared according to the method described above, and 4.4 V cycle characteristics were evaluated. The results are shown in Table 2.

<Reference Example 1>
In the base electrolyte (I), 1,4-butanediol bis (2,2,2-trifluoroethanesulfonate) as the sulfonate compound and vinylene carbonate as the unsaturated carbonates, respectively, with respect to the non-aqueous electrolyte A lithium secondary battery was prepared according to the above-described method using a non-aqueous electrolyte solution added to 1 wt% and 2 wt%, and 4.2 V cycle characteristics evaluation was performed. The results are shown in Table 2.

<Reference Example 2>
A lithium secondary battery according to the above-described method using a non-aqueous electrolyte solution in which vinylene carbonate as an unsaturated carbonate is added to the base electrolyte solution (I) so that the concentration with respect to the non-aqueous electrolyte solution is 2% by weight. And 4.2V cycle characteristics were evaluated. The results are shown in Table 2.

<Reference Example 3>
To the base electrolyte (I), cyclohexylbenzene as an additive in place of the sulfonate compound and vinylene carbonate as an unsaturated carbonate were added so that the concentrations with respect to the non-aqueous electrolyte were 1% by weight and 2% by weight, respectively. Using a non-aqueous electrolyte, a lithium secondary battery was produced according to the method described above, and 4.2 V cycle characteristics were evaluated. The results are shown in Table 2.

  From Table 1, by including the sulfonate compound of the present invention in a non-aqueous electrolyte solution, when charging until a high open circuit voltage between battery terminals such as 4.35 V and 4.45 V, the continuous charge characteristic test It can be seen that the amount of gas generated can be reduced, and further the recovery capacity maintenance rate at 4.35 V can be improved. In particular, when non-aqueous electrolytes mixed with unsaturated carbonates are used (Examples 6 to 11), it can be seen that the suppression of generated gas and the improvement of recovery capacity can be achieved at a high level.

  Furthermore, it can be seen from Table 2 that the capacity retention ratio can be improved in a high voltage cycle test of 4.4 V by adding the sulfonate compound of the present invention to the non-aqueous electrolyte solution. Further, from the results of Reference Examples 1 to 3 which are 4.2 V cycle tests and the results of Example 14 and Comparative Examples 4 and 5 which are 4.4 V tests, cyclohexylbenzene which has been effective in improving the cycle characteristics in the past, etc. It can be seen that even in the case of the additive, in the cycle test under a high voltage of 4.4 V or the like, the characteristics may rather deteriorate.

  The use of the lithium secondary battery of the present invention is not particularly limited, and can be used for various uses in any known field. Specific examples of suitable applications include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, and portable CD players. , Mini-discs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, etc.

It is a schematic sectional drawing which shows the structure of the lithium secondary battery produced in the Example of this invention, the comparative example, and the reference example.

Explanation of symbols

1 Positive electrode 2 Negative electrode 3 Separator (spacer)
4 PET film 5 Silicon rubber 6 Glass plate 7 Laminate film 8 Lead with sealing material

Claims (3)

A positive electrode, a negative electrode, and a nonaqueous electrolytic solution containing a sulfonate compound represented by the following formula (1):
A lithium secondary battery, wherein an open circuit voltage between battery terminals at 25 ° C. at the end of charging is 4.25 V or more.

(In the formula (1), L represents a divalent linking group composed of a carbon atom and a hydrogen atom. R independently represents an aliphatic saturated hydrocarbon group which is unsubstituted or substituted with fluorine. .) 2. The lithium secondary battery according to claim 1, wherein the open circuit voltage between the battery terminals is 4.3 V or more. The lithium secondary battery according to any one of claims 1 and 2, wherein the non-aqueous electrolyte contains unsaturated carbonates.

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