JP2016139611A - Nonaqueous electrolyte and nonaqueous secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte improved in cycle characteristics in a nonaqueous secondary battery, and specifically to provide a nonaqueous electrolyte contributing an improvement in charge/discharge cycle characteristics when charging/discharging is performed at a high voltage condition of 4.5 V or more in terms of metallic lithium, and a nonaqueous secondary battery using the nonaqueous electrolyte.SOLUTION: A nonaqueous electrolyte contains: a nonaqueous solvent: a lithium salt; and a fluorine-containing phosphoric acid ester with an aryl group represented by the following formula (1) (in the formula, n represents 1 or 2, A represents a 6-10C aryl group or aralkyl group that is unsubstituted or substituted with a substituent selected from the group consisting of a fluorine atom, a 1-6C linear or branched alkyl group, a cyano group, a 2-6C linear or branched cyanoalkyl group and a 1-6C alkoxy group, and Rfrepresents a 1-6C linear or branched fluorine-containing alkyl group.)SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous secondary battery using the same.

Non-aqueous secondary batteries such as lithium ion secondary batteries have high output density and high energy density, and are widely used as power sources for mobile phones, notebook computers, tablet computers, and the like. In recent years, with the increase in performance and size of non-aqueous secondary batteries, there has been a demand for higher energy density in non-aqueous electrolyte secondary batteries, and the reduction in battery size or the cruising range of electric vehicles. Extension is desired. In response to these demands, a non-aqueous secondary battery using a positive electrode active material capable of higher voltage (for example, 4.5 V or more based on metallic lithium) has been proposed.
The electrolyte solution of such a non-aqueous secondary battery is obtained by dissolving an electrolyte salt in an organic solvent obtained by mixing a low dielectric solvent such as dimethyl carbonate or diethyl carbonate with a high dielectric constant solvent such as ethylene carbonate or propylene carbonate. Things are commonly used. However, it cannot be said that these electrolytic solutions are sufficient for problems such as deterioration of battery charge / discharge characteristics due to decomposition of the electrolytic solution on the positive electrode and the negative electrode. In particular, when charging / discharging is performed under high voltage conditions, the electrolytic solution is oxidized and decomposed on the positive electrode, causing the battery to swell due to the generation of carbon dioxide gas, or increasing the electrical resistance due to the deposition of decomposition products, thereby increasing the charge / discharge cycle. There is a problem that tends to cause a decrease in performance (Non-Patent Documents 1 and 2).

On the other hand, when a fluorine-containing phosphate ester is included as a solvent as an electrolyte, decomposition of the solvent on the positive electrode is suppressed even when charged and discharged under a high voltage condition of 4.5 V or more based on metallic lithium, and gas It is disclosed that a battery with less generation can be configured (Patent Document 1). However, this technique is still not sufficient in terms of charge / discharge cycle performance.
As a method for suppressing the problem of electrochemical decomposition of the electrolytic solution on the electrode, a nonaqueous electrolytic solution in which various additives are present in the electrolytic solution has been proposed (Non-patent Document 3). And Patent Documents 2 to 4). Non-Patent Document 3 and Patent Document 2 disclose that a protective film (SEI: Solid Electrolyte Interface) is formed by adding a small amount of vinylene carbonate to an electrolytic solution. Patent Document 3 discloses that fluoroethylene carbonate is allowed to coexist in an electrolytic solution, thereby suppressing capacity reduction accompanying high-temperature charge / discharge cycles and gas generation during high-temperature storage. Further, Patent Document 4 discloses a method in which a surface modifier such as 1,3-propane sultone is present and a lithium permeable film is formed on the electrode during charge / discharge.

  Furthermore, a method of adding a flame retardant phosphate ester for the purpose of improving safety such as making the electrolyte solution flame retardant or flame retardant is disclosed (Patent Document 5). In Patent Document 5, by adding a cyclic phosphate ester or a chain phosphate ester to an electrolytic solution containing a cyclic carboxylate ester or a cyclic carbonate ester, the flash point is high, and high conductivity and electrochemical stability are achieved. A method for providing an electrolyte solution having excellent safety is disclosed.

International Publication No. 2012/0777712 JP 2005-149985 A JP 2007-250415 A JP 2011-96672 A JP 2002-203598 A

“Development of materials for next-generation automotive lithium-ion batteries”, CMC Publishing Co., Ltd. (2008) p. 86-89 “Automotive Lithium Ion Battery”, Nikkan Kogyo Shimbun (2010) p. 20-25, p. 130-131 “Functional Chemistry Series of Electrons and Ions” vol.3 Next-Generation Type Lithium Secondary Batteries ”NTS Corporation (2003) p. 134-137

The methods disclosed in Patent Documents 2 to 4 mainly suppress the electrochemical decomposition of the electrolytic solution by forming a stable film on the negative electrode surface.
Therefore, it is difficult to form a film on the positive electrode, and when charge / discharge is performed under high voltage conditions, SEI generation on the negative electrode may be insufficient due to decomposition of the additive. Therefore, even if these prior arts are used, the cycle performance improvement is still not sufficient when charging / discharging is performed under high voltage conditions.
On the other hand, although the method disclosed in Patent Document 5 describes the effect of increasing the thermal stability of the battery, the phosphate ester containing an aryl group described in Examples 6 and 7 is specific. However, it does not describe that the battery performance is improved, and that the effect is remarkably improved by containing fluorine in the ester side chain, which cannot be easily achieved by those skilled in the art.

  The present invention has been made in view of the above problems. That is, the present invention aims to provide an electrolyte solution with improved cycle characteristics in a non-aqueous secondary battery, and in particular, in a lithium ion secondary battery under a high voltage condition of 4.5 V or more on a lithium metal basis. It aims at providing the non-aqueous electrolyte solution which contributes to the improvement of the charging / discharging cycling characteristics at the time of charging / discharging, and a non-aqueous secondary battery using the same.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made the non-aqueous electrolyte contain a fluorine-containing phosphate ester containing a specific aryl group, thereby providing charge / discharge cycle characteristics (hereinafter referred to as “charge / discharge cycle characteristics”). , Simply referred to as cycle characteristics). In particular, the present invention has been completed by finding that in the case of a lithium ion battery, the cycle characteristics are greatly improved when charging and discharging are performed under a high voltage condition of 4.5 V or more on the basis of lithium metal. That is, the present invention relates to the following gist.

1. A non-aqueous solvent;
Lithium salt,
The following general formula (1)


(In the formula, n is 1 or 2, and A is an unsubstituted or fluorine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a cyano group, or a linear or branched cyano group having 2 to 6 carbon atoms. Represents an aryl group or aralkyl group having 6 to 10 carbon atoms substituted by a substituent selected from the group consisting of an alkyl group and an alkoxy group having 1 to 6 carbon atoms, and Rf ¹ is a straight chain having 1 to 6 carbon atoms or A non-aqueous electrolyte solution containing an aryl group-containing fluorine-containing phosphate ester represented by: a branched fluorine-containing alkyl group.
In order to improve cycle characteristics particularly when charging / discharging under high voltage conditions, it is necessary to contain fluorine atoms in the ester side chain.
2. As the aryl-containing fluorine-containing phosphate represented by the general formula (1), the following general formula (2)


(In the formula, n is 1 or 2, and R ^{1 to} R ⁵ each independently represents a hydrogen atom, a fluorine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a cyano group, or 2 to 2 carbon atoms. A straight-chain or branched cyanoalkyl group having 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and Rf ¹ represents a straight-chain or branched fluorine-containing alkyl group having 1 to 6 carbon atoms. The nonaqueous electrolytic solution according to 1 above, comprising
3. In General Formula (2), R ^{1 to} R ⁵ each independently represent a hydrogen atom, a fluorine atom, a cyano group, or an alkoxy group having 1 to 6 carbon atoms, and at least one of them is other than a hydrogen atom. The non-aqueous electrolyte described.
4). In General Formula (2), R ^{1 to} R ⁵ each independently represent a hydrogen atom or an alkoxy group having 1 to 6 carbon atoms, and at least one is an alkoxy group having 1 to 6 carbon atoms. Non-aqueous electrolyte.
5. The nonaqueous electrolytic solution according to any one of items 1 to 4, wherein the nonaqueous solvent is a chain carbonate, a cyclic carbonate, or a mixture thereof.
6). The following general formula (3)

(In the formula, m is an integer of 0 to 3, R ⁶ represents a linear or branched alkyl group having 1 to 6 carbon atoms, and Rf ² represents a linear or branched alkyl group having 1 to 6 carbon atoms. The nonaqueous electrolytic solution according to any one of 1 to 5, further comprising a phosphate ester represented by: a fluorine alkyl group.
Phosphoric acid ester derivatives are known to be effective in suppressing gas generation when charging / discharging at a high voltage, but the charge / discharge cycle characteristics are further improved by coexisting with the compound of general formula (1) above. To do.
7). The content of the aryl group-containing fluorine-containing phosphoric acid ester represented by the general formula (1) is 0.1 to 10% by weight with respect to the nonaqueous solvent, according to any one of items 1 to 6. Water electrolyte.
8). In the non-aqueous electrolyte, 1 to 10% by weight of one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate are contained in a weight ratio of 0.1 to 10% with respect to the non-aqueous solvent. 8. The nonaqueous electrolytic solution according to any one of items 7.
Vinylene carbonate, fluoroethylene carbonate, and vinyl ethylene carbonate are known as a film forming agent (SEI) that forms a film on the negative electrode surface, but when used in combination with these SEI agents, the charge / discharge cycle characteristics can be remarkably improved. .
9. A nonaqueous secondary battery comprising a negative electrode, a positive electrode, a separator, and the nonaqueous electrolytic solution according to any one of 1 to 8.
10. Item 10. The nonaqueous secondary battery according to item 9, wherein the positive electrode contains a positive electrode active material that develops a potential of 4.5 V or more on the basis of lithium metal.

  According to the present invention, a non-aqueous electrolyte with improved cycle characteristics and a non-aqueous secondary battery including the same are provided, and particularly when charging / discharging is performed under a high voltage condition of 4.5 V or more based on lithium metal. In addition, the charge / discharge cycle performance is significantly improved.

It is a schematic cross section which shows the structure of the coin cell type battery used for Examples 1-30 and Comparative Examples 1-7. It is a figure which shows the linear sweep voltagram measured in Example 31, 32 and the comparative example 8. FIG.

  The non-aqueous electrolyte of the present embodiment is characterized in that the non-aqueous electrolyte obtained by dissolving an electrolyte salt in a non-aqueous solvent contains an aryl group-containing fluorine-containing phosphate represented by the general formula (1). And

  The mechanism for improving the cycle characteristics of aryl group-containing fluorine-containing phosphates is unknown, but aryl groups that contribute to film formation, phosphoric acid moieties that contribute to ionic conductivity, and fluorine atoms in the ester side chain Thus, it is estimated that having an appropriate decomposition potential (film forming ability) and good ionic conductivity is involved in the function. In addition, when a substituent such as an alkoxy group is introduced into the aryl group, the cycle characteristics are further improved. Lithium and the substituent interact with each other, and a protective film having high lithium permeability is formed on the electrode surface. It is estimated that it is formed.

In the general formula (1), n is 1 or 2, and has 1 or 2 aryl groups or aralkyl groups and 2 or 1 fluorine-containing alkyl group in the molecule. In the general formula (1), A is unsubstituted or a fluorine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a cyano group, a linear or branched cyanoalkyl group having 2 to 6 carbon atoms, and a carbon number of 1 Represents an aryl group or aralkyl group having 6 to 10 carbon atoms substituted by a substituent selected from the group consisting of ˜6 alkoxy groups. Examples of such A include, for example, phenyl group, 1-naphthyl group, 2-naphthyl group, benzyl group, 1-phenylethyl group, 2-phenylethyl group, 3-phenylpropyl group, 4-phenylbutyl group. 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, 4-ethylphenyl group, 4-n-propylphenyl group, 4-isopropylphenyl group, 4-n-butylphenyl group, 4-tert -Butylphenyl group, 4-n-pentylphenyl group, 4-n-hexylphenyl group, 2-cyanophenyl group, 3-cyanophenyl group, 4-cyanophenyl group, 4- (2-cyanoethyl) phenyl group, 2 , 3-dimethylphenyl group, 2,4-dimethylphenyl group, 2,6-dimethylphenyl, 3,4-dimethylphenyl group, 2,4,6-tri Tylphenyl group, 2-methoxyphenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, 2-ethoxyphenyl group, 3-ethoxyphenyl group, 4-ethoxyphenyl group, 2-n-propoxyphenyl group, 3-n -Propoxyphenyl group, 4-n-propoxyphenyl group, 2-iso-propoxyphenyl group, 3-iso-propoxyphenyl group, 4-iso-propoxyphenyl group, 2-n-butoxyphenyl group, 3-n-butoxy Phenyl group, 4-n-butoxyphenyl group, 2-iso-butoxyphenyl group, 3-iso-butoxyphenyl group, 4-iso-butoxyphenyl group, 2-sec-butoxyphenyl group, 3-sec-butoxyphenyl group 4-sec-butoxyphenyl group, 2-tert-butoxyphenyl group, 3 tert-butoxyphenyl group, 4-tert-butoxyphenyl group, 2-n-pentyloxyphenyl group, 3-n-pentyloxyphenyl group, 4-n-pentyloxyphenyl group, 2- (1-methylbutyloxy) Phenyl group, 3- (1-methylbutyloxy) phenyl group, 4- (1-methylbutyloxy) phenyl group, 2- (2-methylbutyloxy) phenyl group, 3- (2-methylbutyloxy) phenyl group 4- (2-methylbutyloxy) phenyl group, 2- (3-methylbutyloxy) phenyl group, 3- (3-methylbutyloxy) phenyl group, 4- (3-methylbutyloxy) phenyl group, 2 -(1-ethylpropyloxy) phenyl group, 3- (1-ethylpropyloxy) phenyl group, 4- (1-ethylpropyloxy) phenyl group Enyl group, 2- (1,1-dimethylpropyloxy) phenyl group, 3- (1,1-dimethylpropyloxy) phenyl group, 4- (1,1-dimethylpropyloxy) phenyl group, 2- (2, 2-dimethylpropyloxy) phenyl group, 3- (2,2-dimethylpropyloxy) phenyl group, 4- (2,2-dimethylpropyloxy) phenyl group, 2- (1,2-dimethylpropyloxy) phenyl group 3- (1,2-dimethylpropyloxy) phenyl group, 4- (1,2-dimethylpropyloxy) phenyl group, 2-n-hexyloxyphenyl group, 3-n-hexyloxyphenyl group, 4-n -Hexyloxyphenyl group, 2- (1-methylpentyloxy) phenyl group, 3- (1-methylpentyloxy) phenyl group, 4- (1-methyl) Nthyloxy) phenyl group, 2- (2-methylpentyloxy) phenyl group, 3- (2-methylpentyloxy) phenyl group, 4- (2-methylpentyloxy) phenyl group, 2- (3-methylpentyloxy) Phenyl group, 3- (3-methylpentyloxy) phenyl group, 4- (3-methylpentyloxy) phenyl group, 2- (4-methylpentyloxy) phenyl group, 3- (4-methylpentyloxy) phenyl group 4- (4-methylpentyloxy) phenyl group, 2- (1-ethylbutyloxy) phenyl group, 3- (1-ethylbutyloxy) phenyl group, 4- (1-ethylbutyloxy) phenyl group, 2 -(2-ethylbutyloxy) phenyl group, 3- (2-ethylbutyloxy) phenyl group, 4- (2-ethylbutyloxy) phenyl group Nyl group, 2- (1,1-dimethylbutyloxy) phenyl group, 3- (1,1-dimethylbutyloxy) phenyl group, 4- (1,1-dimethylbutyloxy) phenyl group, 2- (1, 2-dimethylbutyloxy) phenyl group, 3- (1,2-dimethylbutyloxy) phenyl group, 4- (1,2-dimethylbutyloxy) phenyl group, 2- (1,3-dimethylbutyloxy) phenyl group 3- (1,3-dimethylbutyloxy) phenyl group, 4- (1,3-dimethylbutyloxy) phenyl group, 2- (2,3-dimethylbutyloxy) phenyl group, 3- (2,3- Dimethylbutyloxy) phenyl group, 4- (2,3-dimethylbutyloxy) phenyl group, 2- (2,2-dimethylbutyloxy) phenyl group, 3- (2,2-dimethylbutyloxy) ) Phenyl group, 4- (2,2-dimethylbutyloxy) phenyl group, 2- (3,3-dimethylbutyloxy) phenyl group, 3- (3,3-dimethylbutyloxy) phenyl group, 4- (3 , 3-dimethylbutyloxy) phenyl group, 2- (1-ethylbutyloxy) phenyl group, 3- (1-ethylbutyloxy) phenyl group, 4- (1-ethylbutyloxy) phenyl group, 2- (2 -Ethylbutyloxy) phenyl group, 3- (2-ethylbutyloxy) phenyl group, 4- (2-ethylbutyloxy) phenyl group, 2- (1-ethyl-2-methylpropyloxy) phenyl group, 3- (1-ethyl-2-methylpropyloxy) phenyl group, 4- (1-ethyl-2-methylpropyloxy) phenyl group, 2- (2-ethyl-1-methylpropyloxy) ) Phenyl group, 3- (2-ethyl-1-methylpropyloxy) phenyl group, 4- (2-ethyl-1-methylpropyloxy) phenyl group, 2- (1-ethyl-1-methylpropyloxy) phenyl Group, 3- (1-ethyl-1-methylpropyloxy) phenyl group, 4- (1-ethyl-1-methylpropyloxy) phenyl group, 2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl Group, 2,3-difluorophenyl group, 2,4-difluorophenyl group, 3,4-difluorophenyl group, 2,4,6-trifluorophenyl group, 3,4,5-trifluorophenyl group, pentafluoro Phenyl group, 4-methylbenzyl group, 4-fluorobenzyl group, 4-methoxybenzyl group, 4-cyanobenzyl group, 4- (2-cyanoethyl) Le) benzyl group, and the like. A 2-cyanophenyl group, 3-cyanophenyl group, 4-cyanophenyl group, 2-methoxyphenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, 3-cyanophenyl group, 4-cyanophenyl group, 2-methoxyphenyl group, 4-methoxyphenyl group, 4-methoxyphenyl group, 4-methoxyphenyl group, 4-methoxyphenyl group, 4-methoxyphenyl group, 4-methoxyphenyl group Methoxyphenyl group, 2-ethoxyphenyl group, 3-ethoxyphenyl group, 4-ethoxyphenyl group, 2-n-propoxyphenyl group, 3-n-propoxyphenyl group, 4-n-propoxyphenyl group, 2-iso- Propoxyphenyl group, 3-iso-propoxyphenyl group, 4-iso-propoxyphenyl group, 2-n-butoxyphenyl group, 3-n-butoxyphenyl group, 4-n-butoxyphenyl group, 2-iso-butoxyphenyl Group, 3-iso-butoxyphenyl group, 4-iso-butoxyphenyl group, 2-sec-butoxy Phenyl group, 3-sec-butoxyphenyl group, 4-sec-butoxyphenyl group, 2-tert-butoxyphenyl group, 3-tert-butoxyphenyl group, 4-tert-butoxyphenyl group, 2-n-pentyloxyphenyl Group, 3-n-pentyloxyphenyl group, 4-n-pentyloxyphenyl group, 2- (1-methylbutyloxy) phenyl group, 3- (1-methylbutyloxy) phenyl group, 4- (1-methyl) Butyloxy) phenyl group, 2- (2-methylbutyloxy) phenyl group, 3- (2-methylbutyloxy) phenyl group, 4- (2-methylbutyloxy) phenyl group, 2- (3-methylbutyloxy) ) Phenyl group, 3- (3-methylbutyloxy) phenyl group, 4- (3-methylbutyloxy) phenyl group, 2- ( -Ethylpropyloxy) phenyl group, 3- (1-ethylpropyloxy) phenyl group, 4- (1-ethylpropyloxy) phenyl group, 2- (1,1-dimethylpropyloxy) phenyl group, 3- (1 , 1-dimethylpropyloxy) phenyl group, 4- (1,1-dimethylpropyloxy) phenyl group, 2- (2,2-dimethylpropyloxy) phenyl group, 3- (2,2-dimethylpropyloxy) phenyl Group, 4- (2,2-dimethylpropyloxy) phenyl group, 2- (1,2-dimethylpropyloxy) phenyl group, 3- (1,2-dimethylpropyloxy) phenyl group, 4- (1,2 -Dimethylpropyloxy) phenyl group, 2-n-hexyloxyphenyl group, 3-n-hexyloxyphenyl group, 4-n-hexyloxyph Enyl group, 2- (1-methylpentyloxy) phenyl group, 3- (1-methylpentyloxy) phenyl group, 4- (1-methylpentyloxy) phenyl group, 2- (2-methylpentyloxy) phenyl group 3- (2-methylpentyloxy) phenyl group, 4- (2-methylpentyloxy) phenyl group, 2- (3-methylpentyloxy) phenyl group, 3- (3-methylpentyloxy) phenyl group, 4 -(3-methylpentyloxy) phenyl group, 2- (4-methylpentyloxy) phenyl group, 3- (4-methylpentyloxy) phenyl group, 4- (4-methylpentyloxy) phenyl group, 2- ( 1-ethylbutyloxy) phenyl group, 3- (1-ethylbutyloxy) phenyl group, 4- (1-ethylbutyloxy) phenyl group, 2 (2-ethylbutyloxy) phenyl group, 3- (2-ethylbutyloxy) phenyl group, 4- (2-ethylbutyloxy) phenyl group, 2- (1,1-dimethylbutyloxy) phenyl group, 3- (1,1-dimethylbutyloxy) phenyl group, 4- (1,1-dimethylbutyloxy) phenyl group, 2- (1,2-dimethylbutyloxy) phenyl group, 3- (1,2-dimethylbutyloxy) ) Phenyl group, 4- (1,2-dimethylbutyloxy) phenyl group, 2- (1,3-dimethylbutyloxy) phenyl group, 3- (1,3-dimethylbutyloxy) phenyl group, 4- (1 , 3-dimethylbutyloxy) phenyl group, 2- (2,3-dimethylbutyloxy) phenyl group, 3- (2,3-dimethylbutyloxy) phenyl group, 4- (2,3- Methylbutyloxy) phenyl group, 2- (2,2-dimethylbutyloxy) phenyl group, 3- (2,2-dimethylbutyloxy) phenyl group, 4- (2,2-dimethylbutyloxy) phenyl group, 2 -(3,3-dimethylbutyloxy) phenyl group, 3- (3,3-dimethylbutyloxy) phenyl group, 4- (3,3-dimethylbutyloxy) phenyl group, 2- (1-ethylbutyloxy) Phenyl group, 3- (1-ethylbutyloxy) phenyl group, 4- (1-ethylbutyloxy) phenyl group, 2- (2-ethylbutyloxy) phenyl group, 3- (2-ethylbutyloxy) phenyl group 4- (2-ethylbutyloxy) phenyl group, 2- (1-ethyl-2-methylpropyloxy) phenyl group, 3- (1-ethyl-2-methylpropyloxy) Xyl) phenyl group, 4- (1-ethyl-2-methylpropyloxy) phenyl group, 2- (2-ethyl-1-methylpropyloxy) phenyl group, 3- (2-ethyl-1-methylpropyloxy) Phenyl group, 4- (2-ethyl-1-methylpropyloxy) phenyl group, 2- (1-ethyl-1-methylpropyloxy) phenyl group, 3- (1-ethyl-1-methylpropyloxy) phenyl group 4- (1-ethyl-1-methylpropyloxy) phenyl group, 2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 2,3-difluorophenyl group, 2,4-difluorophenyl group 3,4-difluorophenyl group, 2,4,6-trifluorophenyl group, 3,4,5-trifluorophenyl group, pentafluorophenyl 2-methoxyphenyl group, 3-methoxyphenyl group, 4-methoxyphenyl group, 2-ethoxyphenyl group, 3-ethoxyphenyl group, 4-ethoxyphenyl group, 2-n-propoxyphenyl group, 3-n -Propoxyphenyl group, 4-n-propoxyphenyl group, 2-isopropoxyphenyl group, 3-isopropoxyphenyl group, 4-isopropoxyphenyl group, 2-n-butoxyphenyl group, 3-n-butoxyphenyl group, 4-n-butoxyphenyl group, 2-iso-butoxyphenyl group, 3-iso-butoxyphenyl group, 4-iso-butoxyphenyl group, 2-sec-butoxyphenyl group, 3-sec-butoxyphenyl group, 4- sec-butoxyphenyl group, 2-tert-butoxyphenyl group, 3-tert-buto Siphenyl group, 4-tert-butoxyphenyl group, 2-n-pentyloxyphenyl group, 3-n-pentyloxyphenyl group, 4-n-pentyloxyphenyl group, 2- (1-methylbutyloxy) phenyl group, 3- (1-methylbutyloxy) phenyl group, 4- (1-methylbutyloxy) phenyl group, 2- (2-methylbutyloxy) phenyl group, 3- (2-methylbutyloxy) phenyl group, 4- (2-methylbutyloxy) phenyl group, 2- (3-methylbutyloxy) phenyl group, 3- (3-methylbutyloxy) phenyl group, 4- (3-methylbutyloxy) phenyl group, 2- (1 -Ethylpropyloxy) phenyl group, 3- (1-ethylpropyloxy) phenyl group, 4- (1-ethylpropyloxy) phenyl group, 2- ( 1,1-dimethylpropyloxy) phenyl group, 3- (1,1-dimethylpropyloxy) phenyl group, 4- (1,1-dimethylpropyloxy) phenyl group, 2- (2,2-dimethylpropyloxy) Phenyl group, 3- (2,2-dimethylpropyloxy) phenyl group, 4- (2,2-dimethylpropyloxy) phenyl group, 2- (1,2-dimethylpropyloxy) phenyl group, 3- (1, 2-dimethylpropyloxy) phenyl group, 4- (1,2-dimethylpropyloxy) phenyl group, 2-n-hexyloxyphenyl group, 3-n-hexyloxyphenyl group, 4-n-hexyloxyphenyl group, 2- (1-methylpentyloxy) phenyl group, 3- (1-methylpentyloxy) phenyl group, 4- (1-methylpentyloxy) Enyl group, 2- (2-methylpentyloxy) phenyl group, 3- (2-methylpentyloxy) phenyl group, 4- (2-methylpentyloxy) phenyl group, 2- (3-methylpentyloxy) phenyl group 3- (3-methylpentyloxy) phenyl group, 4- (3-methylpentyloxy) phenyl group, 2- (4-methylpentyloxy) phenyl group, 3- (4-methylpentyloxy) phenyl group, 4 -(4-methylpentyloxy) phenyl group, 2- (1-ethylbutyloxy) phenyl group, 3- (1-ethylbutyloxy) phenyl group, 4- (1-ethylbutyloxy) phenyl group, 2- ( 2-ethylbutyloxy) phenyl group, 3- (2-ethylbutyloxy) phenyl group, 4- (2-ethylbutyloxy) phenyl group, 2- ( , 1-dimethylbutyloxy) phenyl group, 3- (1,1-dimethylbutyloxy) phenyl group, 4- (1,1-dimethylbutyloxy) phenyl group, 2- (1,2-dimethylbutyloxy) phenyl Group, 3- (1,2-dimethylbutyloxy) phenyl group, 4- (1,2-dimethylbutyloxy) phenyl group, 2- (1,3-dimethylbutyloxy) phenyl group, 3- (1,3 -Dimethylbutyloxy) phenyl group, 4- (1,3-dimethylbutyloxy) phenyl group, 2- (2,3-dimethylbutyloxy) phenyl group, 3- (2,3-dimethylbutyloxy) phenyl group, 4- (2,3-dimethylbutyloxy) phenyl group, 2- (2,2-dimethylbutyloxy) phenyl group, 3- (2,2-dimethylbutyloxy) phenyl group, 4 -(2,2-dimethylbutyloxy) phenyl group, 2- (3,3-dimethylbutyloxy) phenyl group, 3- (3,3-dimethylbutyloxy) phenyl group, 4- (3,3-dimethylbutyl) Oxy) phenyl group, 2- (1-ethylbutyloxy) phenyl group, 3- (1-ethylbutyloxy) phenyl group, 4- (1-ethylbutyloxy) phenyl group, 2- (2-ethylbutyloxy) Phenyl group, 3- (2-ethylbutyloxy) phenyl group, 4- (2-ethylbutyloxy) phenyl group, 2- (1-ethyl-2-methylpropyloxy) phenyl group, 3- (1-ethyl- 2-methylpropyloxy) phenyl group, 4- (1-ethyl-2-methylpropyloxy) phenyl group, 2- (2-ethyl-1-methylpropyloxy) phenyl group, -(2-ethyl-1-methylpropyloxy) phenyl group, 4- (2-ethyl-1-methylpropyloxy) phenyl group, 2- (1-ethyl-1-methylpropyloxy) phenyl group, 3- ( A 1-ethyl-1-methylpropyloxy) phenyl group and a 4- (1-ethyl-1-methylpropyloxy) phenyl group are more preferable.

In the general formula (1), Rf ¹ represents a linear or branched fluorine-containing alkyl group having 1 to 6 carbon atoms. For example, 2-fluoroethyl group, 2,2-difluoroethyl group, 2,2,2 -Trifluoroethyl group, 2,2,3,3-tetrafluoropropyl group, 2,2,3,3,3-pentafluoropropyl group, hexafluoroisopropyl group, 2,2,3,3,4,4 , 5,5-octafluoropentyl group and 3,3,4,4,5,5,6,6,6-nonafluorohexyl group. Further, in order to achieve both an appropriate decomposition potential (film forming ability) and good ionic conductivity, at least one Rf ¹ side chain is required.

As an example of the aryl group-containing fluorine-containing phosphate ester of the general formula (1), when n = 1, for example, bis (2-fluoroethyl) phenyl phosphate, bis (2,2-difluoroethyl) phenyl phosphate, Bis (2,2,2-trifluoroethyl) phenyl phosphate, bis (2,2,3,3-tetrafluoropropyl) phenyl phosphate, bis (2,2,3,3,3-pentafluorophosphate) Propyl) phenyl, bis (hexafluoroisopropyl) phenyl phosphate, bis (2,2,3,3,4,4,5,5-octafluoropentyl) phenyl phosphate, bis (3,3,4, phosphate) 4,5,5,6,6,6-nonafluorohexyl) phenyl, bis (2,2,2-trifluoroethyl) phosphate 1-naphthyl, bis (2,2,2-trifluoroethyl phosphate) -Naphtyl, bis (2,2,2-trifluoroethyl) benzyl phosphate, bis (2,2,2-trifluoroethyl) phosphate (1-phenylethyl), bis (2,2,2-phosphate) Trifluoroethyl) (2-phenylethyl), bis (2,2,2-trifluoroethyl) phosphate (3-phenylpropyl), bis (2,2,2-trifluoroethyl) phosphate (4-phenyl) Butyl), bis (2,2,2-trifluoroethyl) phosphate (2-methylphenyl), bis (2,2,2-trifluoroethyl) phosphate (3-methylphenyl), bis (2 , 2,2-trifluoroethyl) (4-methylphenyl), bis (2,2,2-trifluoroethyl) phosphate (4-ethylphenyl), bis (2,2,2-trifluoroethyl phosphate) ) (4-n Propylphenyl), bis (2,2,2-trifluoroethyl) phosphate (4-isopropylphenyl), bis (2,2,2-trifluoroethyl) phosphate (4-n-butylphenyl), phosphoric acid Bis (2,2,2-trifluoroethyl) (4-tert-butylphenyl), bis (2,2,2-trifluoroethyl) phosphate (4-n-pentylphenyl), bis (2, 2,2-trifluoroethyl) (4-n-hexylphenyl), bis (2,2,2-trifluoroethyl) phosphate (2,3-dimethylphenyl), bis (2,2,2-phosphate) Trifluoroethyl) (2,4-dimethylphenyl), bis (2,2,2-trifluoroethyl) phosphate (3,4-dimethylphenyl), bis (2,2,2-trifluoroethyl phosphate) (2,6 -Dimethylphenyl), bis (2,2,2-trifluoroethyl) phosphate (2,4,6-trimethylphenyl), bis (2,2,2-trifluoroethyl) phosphate (2-methoxyphenyl) Bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (4-methoxyphenyl), bis (2,2 , 2-trifluoroethyl) (2-ethoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (3-ethoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate ( 4-ethoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (2-n-propoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (3-n-propoxyphene) ), Bis (2,2,2-trifluoroethyl) phosphate (4-n-propoxyphenyl), bis (2,2,2-trifluoroethyl phosphate) (2-iso-propoxyphenyl), phosphorus Bis (2,2,2-trifluoroethyl) acid (3-iso-propoxyphenyl), bis (2,2,2-trifluoroethyl phosphate) (4-iso-propoxyphenyl), bis (2 , 2,2-trifluoroethyl) (2-n-butoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (3-n-butoxyphenyl), bis (2,2,2) phosphate -Trifluoroethyl) (4-n-butoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (2-iso-butoxyphenyl), bis (2,2,2-trifluoroethyl phosphate) (3-iso-butoxyphenyl), bis (2,2,2-trifluoroethyl phosphate) (4-iso-butoxyphenyl), bis (2,2,2-trifluoroethyl phosphate) (2-sec -Butoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (3-sec-butoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (4-sec-butoxyphenyl) Bis (2,2,2-trifluoroethyl) phosphate (2-tert-butoxyphenyl), bis (2,2,2-trifluoroethyl phosphate) (3-tert-butoxyphenyl), bisphosphate (2,2,2-trifluoroethyl) (4-tert-butoxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (2-n-pentyloxyphenyl), Bis (2,2,2-trifluoroethyl) phosphate (3-n-pentyloxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (4-n-pentyloxyphenyl), phosphoric acid Bis (2,2,2-trifluoroethyl) (2-n-hexyloxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (3-n-hexyloxyphenyl), bis ( 2,2,2-trifluoroethyl) (4-n-hexyloxyphenyl), bis (2,2,2-trifluoroethyl) phosphate (2-fluorophenyl), bis (2,2,2) phosphate -Trifluoroethyl) (3-fluorophenyl), bis (2,2,2-trifluoroethyl) phosphate (4-fluorophenyl), bis (2,2,2-trifluoroethyl) phosphate (2, 3-di Fluorophenyl), bis (2,2,2-trifluoroethyl) phosphate (2,4-difluorophenyl), bis (2,2,2-trifluoroethyl) phosphate (2,6-difluorophenyl), phosphorus Bis (2,2,2-trifluoroethyl) acid (3,4-difluorophenyl), bis (2,2,2-trifluoroethyl phosphate) (2,4,6-trifluorophenyl), phosphoric acid Bis (2,2,2-trifluoroethyl) (3,4,5-trifluorophenyl), bis (2,2,2-trifluoroethyl) phosphate (pentafluorophenyl), bis (2, 2,2-trifluoroethyl) (2-cyanophenyl), bis (2,2,2-trifluoroethyl) phosphate (3-cyanophenyl), bis (2,2,2-trifluoroethyl phosphate) (4- Anophenyl), bis (2,2,2-trifluoroethyl) phosphate [4- (2-cyanoethyl) phenyl], bis (2,2,2-trifluoroethyl) phosphate (4-methylbenzyl), phosphorus Bis (2,2,2-trifluoroethyl) acid (4-fluorobenzyl), Bis (2,2,2-trifluoroethyl phosphate) (4-methoxybenzyl), Bis (2,2,2) phosphate -Trifluoroethyl) (4-cyanobenzyl), bis (2,2,2-trifluoroethyl) phosphate [4- (2-cyanoethyl) benzyl] and the like.
In the case of n = 2, for example, diphenyl phosphate (2-fluoroethyl), diphenyl phosphate (2,2-difluoroethyl), diphenyl phosphate (2,2,2-trifluoroethyl), diphenyl phosphate (2,2,3,3-tetrafluoropropyl), diphenyl phosphate (2,2,3,3,3-pentafluoropropyl), diphenyl phosphate (hexafluoroisopropyl), diphenyl phosphate (2,2, 3,3,4,4,5,5-octafluoropentyl), diphenyl phosphate (3,3,4,4,5,5,6,6,6-nonafluorohexyl), di-1-phosphate Naphthyl (2,2,2-trifluoroethyl), di-2-naphthyl phosphate (2,2,2-trifluoroethyl), dibenzyl phosphate (2,2,2-trifluoroethyl), phosphoric acid (1-phenylethyl) (2,2,2-trifluoroethyl), bis (2-phenylethyl) phosphate (2,2,2-trifluoroethyl), bis (3-phenylpropyl) phosphate ( 2,2,2-trifluoroethyl), bis (4-phenylbutyl) phosphate (2,2,2-trifluoroethyl), bis (2-methylphenyl) phosphate (2,2,2-trifluoro) Ethyl), bis (3-methylphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-methylphenyl) phosphate (2,2,2-trifluoroethyl), bis (4 -Ethylphenyl) (2,2,2-trifluoroethyl), bis (4-n-propylphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-isopropylphenyl) phosphate (2 , 2,2- Trifluoroethyl), bis (4-n-butylphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-tert-butylphenyl) phosphate (2,2,2-trifluoroethyl) Bis (4-n-pentylphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-n-hexylphenyl) phosphate (2,2,2-trifluoroethyl), bisphosphate (2,3-dimethylphenyl) (2,2,2-trifluoroethyl), bis (2,4-dimethylphenyl) phosphate (2,2,2-trifluoroethyl), bis (3,4) phosphate -Dimethylphenyl) (2,2,2-trifluoroethyl), bis (2,6-dimethylphenyl) phosphate (2,2,2-trifluoroethyl), bis (2,4,6-trimethyl phosphate) Phenyl) (2,2 , 2-trifluoroethyl), bis (2-methoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (3-methoxyphenyl) phosphate (2,2,2-trifluoroethyl), Bis (4-methoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (2-ethoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (3-ethoxyphenyl phosphate) ) (2,2,2-trifluoroethyl), bis (4-ethoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (2-n-propoxyphenyl) phosphate (2,2, 2-trifluoroethyl), bis (3-n-propoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-n-propoxyphenyl) phosphate (2,2,2-trifluoro) Chill), bis (2-iso-propoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (3-iso-propoxyphenyl) phosphate (2,2,2-trifluoroethyl), phosphorus Bis (4-iso-propoxyphenyl) acid (2,2,2-trifluoroethyl), Bis (2-n-butoxyphenyl) phosphate (2,2,2-trifluoroethyl), Bis (3 -N-butoxyphenyl) (2,2,2-trifluoroethyl), bis (4-n-butoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (2-iso-butoxy phosphate) Phenyl) (2,2,2-trifluoroethyl), bis (3-iso-butoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-iso-butoxypheny phosphate) ) (2,2,2-trifluoroethyl), bis (2-sec-butoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (3-sec-butoxyphenyl) phosphate (2, 2,2-trifluoroethyl), bis (4-sec-butoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (2-tert-butoxyphenyl) phosphate (2,2,2- Trifluoroethyl), bis (3-tert-butoxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-tert-butoxyphenyl) phosphate (2,2,2-trifluoroethyl) Bis (2-n-pentyloxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (3-n-pentyloxyphenyl) phosphate (2,2,2-trifluoroethyl) ), Bis (4-n-pentyloxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (2-n-hexyloxyphenyl) phosphate (2,2,2-trifluoroethyl) Bis (3-n-hexyloxyphenyl) phosphate (2,2,2-trifluoroethyl), bis (4-n-hexyloxyphenyl) phosphate (2,2,2-trifluoroethyl), phosphorus Bis (2-fluorophenyl) acid (2,2,2-trifluoroethyl), Bis (3-fluorophenyl) phosphate (2,2,2-trifluoroethyl), Bis (4-fluorophenyl) phosphate (2,2,2-trifluoroethyl), bis (2,3-difluorophenyl) phosphate (2,2,2-trifluoroethyl), bis (2,4-difluorophenyl) phosphate (2,2 , 2- Trifluoroethyl), bis (2,6-difluorophenyl) phosphate (2,2,2-trifluoroethyl), bis (3,4-difluorophenyl) phosphate (2,2,2-trifluoroethyl) Bis (3,4,5-trifluorophenyl) phosphate (2,2,2-trifluoroethyl), bis (2,4,6-trifluorophenyl) phosphate (2,2,2-trifluoro Ethyl), bis (pentafluorophenyl) phosphate (2,2,2-trifluoroethyl), bis (2-cyanophenyl) phosphate (2,2,2-trifluoroethyl), bis (3- Cyanophenyl) (2,2,2-trifluoroethyl), bis (4-cyanophenyl) phosphate (2,2,2-trifluoroethyl), bis [4- (2-cyanoethyl) phenyl] phosphate ( 2,2,2- Trifluoroethyl), bis (4-methylbenzyl) phosphate (2,2,2-trifluoroethyl), bis (4-fluorobenzyl) phosphate (2,2,2-trifluoroethyl), bisphosphate (4-methoxybenzyl) (2,2,2-trifluoroethyl), bis (4-cyanobenzyl) phosphate (2,2,2-trifluoroethyl), bis [4- (2-cyanoethyl) phosphate Benzyl] (2,2,2-trifluoroethyl) and the like.
Among these aryl group-containing fluorine-containing phosphate esters, when A represented by the general formula (1) is an unsubstituted or substituted phenyl group, it is preferable because better cycle characteristics can be obtained.

  Further, from the viewpoint that even better cycle characteristics can be obtained, the compound represented by the general formula (2) is an aryl group-containing fluorine-containing phosphate represented by the general formula (1). It is preferable to contain in a non-aqueous electrolyte.

In formula (2), n is 1 or 2, and R ^{1 to} R ⁵ are each independently a hydrogen atom, a fluorine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a cyano group, or a carbon number. represents a 2-6 straight-chain or branched cyanoalkyl group or an alkoxy group having 1 to 6 carbon atoms, Rf ¹ represents a linear or branched fluorinated alkyl group having 1 to 6 carbon atoms.
Among these, since even better cycle characteristics can be obtained, as the compound of the general formula (2), R ^{1 to} R ⁵ are each independently a hydrogen atom, a fluorine atom, a cyano group, or a carbon number of 1 to 6 is an alkoxy group, and at least one is preferably a compound substituted with a substituent other than a hydrogen atom. Most preferably, R ^{1 to} R ⁵ are each independently a hydrogen atom or a carbon number of 1 to 6 is a compound in which at least one is substituted with an alkoxy group having 1 to 6 carbon atoms.

  The addition amount of the non-aqueous electrolyte of the aryl group-containing fluorine-containing phosphate ester of the general formula (1) is desirably 0.1 to 10% by weight with respect to the non-aqueous solvent, and more preferably, 0.5 to 5%. When the addition amount is less than 0.1%, a sufficient effect of improving the cycle characteristics cannot be obtained as compared with the case where it is within the range, and when the addition amount exceeds 10%, it is compared with the case where it is within the range. As a result, the electrical conductivity of the electrolytic solution may decrease, and the performance of the nonaqueous secondary battery may decrease.

  In addition to the aryl group-containing fluorine-containing phosphate ester of the general formula (1), the non-aqueous electrolyte of the present embodiment further includes at least one selected from the group consisting of vinylene carbonate, fluoroethylene carbonate, and vinylethylene carbonate. The presence of the compound is preferable because improved cycle characteristics can be obtained. In addition, it is desirable for the addition amount of vinylene carbonate etc. in this case to be 0.1 to 10% by weight ratio with respect to a nonaqueous solvent, More preferably, it is 0.5 to 5%.

  Examples of the non-aqueous solvent contained in the non-aqueous electrolyte include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, diphenyl carbonate, bis Chain carbonates such as (2,2,2-trifluoroethyl) carbonate, cyclic esters such as γ-butyrolactone, γ-valerolactone and propiolactone, chain esters such as methyl acetate, methyl butyrate and ethyl trifluoroacetate , Ethers such as diisopropyl ether, tetrahydrofuran, dioxolane, dimethoxyethane, diethoxyethane, methoxyethoxyethane, and nitrates such as acetonitrile and benzonitrile Examples thereof include rils alone or a mixture of two or more thereof. Among these, it is particularly preferable to use a solvent containing either one of cyclic carbonate and chain carbonate or a mixture of cyclic carbonate and chain carbonate in terms of ion conductivity and battery cycle performance.

  Moreover, in the non-aqueous electrolyte of this embodiment, by further containing the phosphate ester represented by the general formula (3), particularly when charging / discharging at a high voltage of 4.5 V or more on the lithium metal basis In view of gas generation and cycle characteristics, high performance is preferable.

In the phosphate ester represented by the general formula (3), m is an integer of 0 to 3, R ⁶ represents a linear or branched alkyl group having 1 to 6 carbon atoms, and Rf ² represents the number of carbon atoms. 1 to 6 linear or branched fluorine-containing alkyl groups are represented.
Examples of the phosphate ester of the general formula (3) include, for example, trimethyl phosphate, triethyl phosphate, tri-n-propyl phosphate, tri-iso-propyl phosphate, tri-n-butyl phosphate, triphosphate -Iso-butyl, tri-tert-butyl phosphate, triphenyl phosphate, tris phosphate (2-fluoroethyl), tris phosphate (2,2-difluoroethyl), tris phosphate (2,2,2- Trifluoroethyl), tris phosphate (2,2,3,3-tetrafluoropropyl), tris phosphate (2,2,3,3,3-pentafluoropropyl), tris phosphate (hexafluoro-iso-) Propyl), tris phosphate (2,2,3,3,4,4,5,5-octafluoropentyl), tris phosphate (2,2,3,3,4,4,5,5,5- Nonafluo Pentyl), bis (2,2,2-trifluoroethyl) methyl phosphate, bis (2,2,2-trifluoroethyl) ethyl phosphate, bis (2,2,2-trifluoroethyl) n phosphate -Propyl, bis (2,2,2-trifluoroethyl) phosphate, iso-propyl, bis (2,2,2-trifluoroethyl) n-butyl phosphate, bis (2,2,2-triphosphate) Fluoroethyl) tert-butyl, bis (2,2,2-trifluoroethyl) phosphate (2,2-difluoroethyl), bis (2,2,2-trifluoroethyl phosphate) (2,2,3 , 3-tetrafluoropropyl), bis (2,2,3,3-tetrafluoropropyl) phosphate (2,2,2-trifluoroethyl) and phosphoric acid (2,2,2-trifluoroethyl) ( 2,2,3,3- It can be exemplified tiger trifluoropropyl) methyl and the like, in the nonaqueous electrolytic solution in this embodiment, for example, they can be made to contain one or more.

As the electrolyte salt contained in the nonaqueous electrolytic solution of the present embodiment, a lithium salt that is stable in a wide potential region is used. Examples of such electrolyte salts include LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC _(CF 3 _{SO 2) 3} and the like. These may be used alone or in combination of two or more. In order to improve battery characteristics, it is desirable that the concentration of the electrolyte salt in the non-aqueous electrolyte is in the range of 0.2 to 2.5 mol / L.

  The non-aqueous secondary battery according to this embodiment can be configured to include a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. Usually, among non-aqueous secondary batteries, a case where metallic lithium is used as a negative electrode is called a lithium secondary battery, and a case where a material capable of doping and dedoping lithium ions is used as a negative electrode is called a lithium ion secondary battery.

As the positive electrode material, a composite oxide composed of lithium and a transition metal such as LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFeO ₂ , LiFePO ₄ can be used. In particular, as a positive electrode material that develops a potential of 4.5 V or more on the basis of the negative electrode metal, LiNi _1/3 Mn _1/3 Co _1/3 O ₂ or LixMn _2-y Ni _y O ₄ (0 ≦ x ≦ 1, 0 A positive electrode including an active material having a composition such as .45 ≦ y ≦ 0.6) is preferable because a potential of 4.5 V or more is stably expressed on the basis of metallic lithium.

As the negative electrode material, metal lithium, lithium and transition metal composite oxides such as Li ₄ Ti ₅ O ₁₂ or carbon materials such as graphite and other materials capable of doping and dedoping lithium ions, respectively, should be used. Can do.

As the separator, a microporous film or the like is used, and as a material, a polyolefin resin such as polyethylene or a fluorine resin such as polyvinylidene fluoride is used.
As the shape and form of the nonaqueous electrolyte secondary battery, a cylindrical type, a square type, a coin type, a card type, a laminate type, and the like are usually selected.

  Hereinafter, although an example, a comparative example, and a reference example explain the present invention, the present invention is not limited to these.

Example 1 Using lithium cobalt oxide (LiCoO ₂₎ as creating a positive electrode active material of the coin-type lithium ion secondary battery, to which acetylene black as a conductive auxiliary agent, polyvinylidene fluoride (PVDF) with LiCoO _2: acetylene black: PVDF = 86 : 7: 7 was blended and slurried with 1-methyl-2-pyrrolidone was applied on an aluminum current collector with a certain film thickness and dried to obtain a positive electrode. Natural negative graphite is used as a negative electrode active material, PVDF is blended as a binder so that graphite: PVDF = 9: 1, and slurried using 1-methyl-2-pyrrolidone is placed on a copper current collector. It apply | coated with the fixed film thickness, it was made to dry and the negative electrode was obtained.

  As the separator, an inorganic filler-containing polyolefin porous membrane was used. Using the above components, a lithium ion secondary battery using a coin-type cell having the structure shown in FIG. 1 was prepared. In the lithium ion secondary battery, the positive electrode 1 and the negative electrode 5 are arranged opposite to each other with the separator 8 interposed therebetween, the stainless steel leaf spring 7 is installed on the negative electrode stainless steel cap 4, and the laminate composed of the negative electrode 5, the separator 8 and the positive electrode 1 is coined. Housed in a mold cell. After injecting a non-aqueous electrolyte into this laminate, the gasket 9 was placed, and then a positive electrode stainless steel cap 3 was placed thereon, and a coin-type cell case was caulked.

Creation example 2. Preparation of coin cell type lithium ion secondary battery Lithium nickel manganese cobalt composite oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) is used as a positive electrode active material, and acetylene black is used as a conductive auxiliary agent and binder is used. Polyvinylidene fluoride (PVDF) was blended so that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ : acetylene black: PVDF = 86: 7: 7 and slurried using 1-methyl-2-pyrrolidone The resulting product was applied on an aluminum current collector with a constant film thickness and dried to obtain a positive electrode. Natural negative graphite is used as a negative electrode active material, PVDF is blended as a binder so that graphite: PVDF = 9: 1, and slurried using 1-methyl-2-pyrrolidone is placed on a copper current collector. It apply | coated with the fixed film thickness, it was made to dry and the negative electrode was obtained.

  As the separator, an inorganic filler-containing polyolefin porous membrane was used. Using the above components, a lithium ion secondary battery using a coin-type cell having the structure shown in FIG. 1 was prepared. In the lithium ion secondary battery, the positive electrode 1 and the negative electrode 5 are arranged opposite to each other with the separator 8 interposed therebetween, the stainless steel leaf spring 7 is installed on the negative electrode stainless steel cap 4, and the laminate composed of the negative electrode 5, the separator 8 and the positive electrode 1 is coined. Housed in a mold cell. After injecting a non-aqueous electrolyte into this laminate, the gasket 9 was placed, and then a positive electrode stainless steel cap 3 was placed thereon, and a coin-type cell case was caulked.

Test Example 1 Charge / Discharge Test of Coin Cell Type Lithium Ion Secondary Battery A coin cell type lithium ion secondary battery made with a lithium cobalt oxide (LiCoO ₂ ) positive electrode and a carbon negative electrode has an upper limit voltage at a constant current of 25 ° C. and a charging current of 0.1 C. The battery was charged as 4.2 V, and then discharged to 3.0 V with a discharge current of 0.1 C.
After performing this operation three times, under a constant temperature condition of 65 ° C., a constant current-low voltage charge of 4.2 V is performed with a charge current of 0.2 C, and a constant current is reached with a discharge current of 0.2 C to a final voltage of 3.0 V. Discharge was performed. The discharge capacity at this time was defined as the initial discharge capacity, the discharge capacity when this operation was repeated 50 times was measured, and the comparison was performed using the discharge capacity / initial discharge capacity ratio after 50 cycles as the capacity retention rate.

Test Example 2 Charge / Discharge Test of Coin Cell Type Lithium Ion Secondary Battery A coin cell type lithium ion secondary battery prepared by using a lithium nickel manganese composite oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) positive electrode and a carbon negative electrode at 25 ° C. Under the constant temperature conditions, the battery was charged with an upper limit voltage of 4.5 V with a charging current of 0.1 C, and subsequently discharged to 3.0 V with a discharging current of 0.1 C.
After performing this operation three times, under a constant temperature of 65 ° C., a constant current-low voltage charge of 4.5 V is performed with a charge current of 0.2 C, and a constant current is reached with a discharge current of 0.2 C to a final voltage of 3.0 V. Discharge was performed. The discharge capacity at this time was defined as the initial discharge capacity, the discharge capacity when this operation was repeated 50 times was measured, and the comparison was performed using the discharge capacity / initial discharge capacity ratio after 50 cycles as the capacity retention rate.

Next, a method for synthesizing the aryl group-containing fluorine-containing phosphate used in the examples will be described with reference examples.
The following analytical method was used to identify the aryl group-containing fluorine-containing phosphate ester. Bruker 400 ULTRASHIELD AVANCE II (400 MHz and 376 MHz) was used for the measurement of ¹ H-NMR and ¹⁹ F-NMR. ¹ H-NMR was measured using deuterated chloroform (CDCl ₃ ) as a measurement solvent and tetramethylsilane (TMS) as an internal standard substance. ¹⁹ F-NMR was measured using deuterated chloroform (CDCl ₃ ) as a measurement solvent and benzotrifluoride as an internal standard substance. Mass spectrometry was performed using GCMS-QP2010 PLUS manufactured by SHIMADZU. The melting point was measured using B-545 manufactured by Büch.

[Reference Example 1]
Synthesis of bis (2,2,2-trifluoroethyl) phenyl phosphate

Under a nitrogen atmosphere, phenyl dichlorophosphate (500 g, 2.37 mol) and magnesium chloride (6.77 g, 0.0711 mol) were added to the flask, and the temperature was raised to 70 ° C. Further, 2,2,2-trifluoroethanol (711 g, 7.11 mmol) was added dropwise and stirred at 95 ° C. for 26 hours. After completion of the reaction, the organic layer was washed with 5% aqueous sodium hydrogen carbonate solution and water. The organic layer was purified by distillation under reduced pressure to obtain the desired bis (2,2,2-trifluoroethyl) phenyl phosphate as a colorless liquid (703 g, 88%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 4.46 (q, J = 8.0 Hz, 4H), 7.20-7.40 (m, 5H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-75.8 (t, J = 8.0 Hz, 6F).
MS (EI): m / z (%) = 338 (M ^<+> , 100), 319 (19), 298 (77), 94 (76), 77 (85).

[Reference Example 2]
Synthesis of diphenyl phosphate (2,2,2-trifluoroethyl)

Under a nitrogen atmosphere, diphenyl chlorophosphate (200 g, 0.745 mol), chloroform (400 ml) and 2,2,2-trifluoroethanol (78.2 g, 0.782 mol) were added to the flask and cooled to 0 ° C. Subsequently, triethylamine (89.2 g, 0.882 mol) was added dropwise, and the mixture was stirred at 0 ° C. for 1 hour and further at room temperature for 19 hours. After completion of the reaction, the organic layer was washed with 1% sodium hydroxide aqueous solution, 5% sulfuric acid aqueous solution and water, and the organic layer was dried over sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was purified by distillation under reduced pressure to obtain the target diphenyl phosphate (2,2,2-trifluoroethyl) as a colorless liquid (138 g, 56%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 4.50 (qd, J = 8.0 Hz, J = 8.0 Hz, 4H), 7.20-7.39 (m, 10H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-75.7 (t, J = 8.0 Hz, 3F).
MS (EI): m / z (%) = 332 (M ^<+> , 87), 170 (25), 94 (38), 77 (100), 65 (34).

[Reference Example 3]
Synthesis of bis (2,2,2-trifluoroethyl) phosphate (3-fluorophenyl)

In a nitrogen atmosphere, the flask was synthesized according to Bis (2,2,2-trifluoroethyl) chlorophosphate (Journal of Fluorine Chemistry, 2002, 113, 65-78: 208 g, 0.743 mol), magnesium chloride (2 .83 g, 0.0297 mol) and 3-fluorophenol (100 g, 0.892 mol) were added, and the mixture was stirred at 80 ° C. for 24 hours. After completion of the reaction, the organic layer was washed with 2% aqueous sodium hydroxide and water. The organic layer was purified by distillation under reduced pressure to obtain the desired bis (2,2,2-trifluoroethyl) phosphate (3-fluorophenyl) as a colorless liquid (186 g, 70%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 4.46 (qd, J = 9.4 Hz, J = 5.6 Hz, 4H), 6.95-7.38 (m, 4H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-75.8 (t, J = 9.4 Hz, 6F), δ-109.9 (q, J = 7.5 Hz, 1F).
MS (EI): m / z (%) = 356 (M ⁺ , 83), 337 (21), 316 (63), 112 (100), 95 (79).

[Reference Example 4]
Synthesis of bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl)

Under a nitrogen atmosphere, 3-methoxyphenol (38.7 g, 0.311 mol), chloroform (150 ml) and triethylamine (37.8 g, 0.311 mol) were added to the flask, and the mixture was stirred at room temperature. Further, bis (2,2,2-trifluoroethyl) chlorophosphate (90.6 g, 0.323 mol) was added dropwise, and the mixture was stirred at 60 ° C. for 19 hours. After completion of the reaction, the organic layer was washed with 2% aqueous sodium hydroxide solution, 5% aqueous sulfuric acid solution and water, and then the organic layer was concentrated under reduced pressure to obtain a crude product. The crude product was purified by distillation under reduced pressure to obtain the desired bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl) as a colorless liquid (86.6 g, 76%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 3.80 (s, 3H), 4.46 (q, J = 8.0 Hz, 4H), 6.74-7.38 (m, 4H)
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-75.8 (t, J = 9.4 Hz, 6F), −109.9 (q, J = 7.5 Hz, 1F)
MS (EI): m / z (%) = 368 (M ⁺ , 100), 349 (8), 328 (35), 299 (15), 76 (53).

[Reference Example 5]
Synthesis of bis (2,2,2-trifluoroethyl) phosphate (3-cyanophenyl)

Under a nitrogen atmosphere, 3-cyanophenol (70.0 g, 0.588 mol), toluene (470 ml) and triethylamine (101 g, 0.999 mol) were added to the flask and heated to 60 ° C. Further, bis (2,2,2-trifluoroethyl) chlorophosphate (214 g, 0.764 mol) was added dropwise, and the mixture was stirred at 110 ° C. for 47 hours. After completion of the reaction, the organic layer was washed with water, and the organic layer was dried over sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was distilled under reduced pressure to obtain the desired bis (2,2,2-trifluoroethyl) phosphate (3-cyanophenyl) as a colorless liquid (110 g, 52%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 4.49 (qd, J = 8.0 Hz, J = 8.0 Hz, 4H), 7.47-7.58 (m, 4H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-75.8 (t, J = 8.0 Hz, 6F).
MS (EI): m / z (%) = 363 (M ⁺ , 66), 344 (24), 323 (74), 165 (47), 119 (100).

[Reference Example 6]
Synthesis of bis (2,2,2-trifluoroethyl) phosphate (4-cyanophenyl)

Under a nitrogen atmosphere, 4-cyanophenol (73.0 g, 0.613 mol), toluene (450 ml) and triethylamine (105 g, 1.04 mol) were added to the flask and heated to 60 ° C. Further, bis (2,2,2-trifluoroethyl) chlorophosphate (206 g, 0.735 mol) was added dropwise, and the mixture was stirred at 105 ° C. for 44 hours. After completion of the reaction, the organic layer was washed with 10% sodium hydroxide aqueous solution, 2.5% sulfuric acid aqueous solution, saturated brine and water, and then the organic layer was dried over sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain a crude product. A simple distillation of the organic layer was performed to obtain a crude product. The crude product was recrystallized and purified from diethyl ether / hexane to obtain the desired bis (2,2,2-trifluoroethyl) phosphate (4-cyanophenyl) as a white solid (56.3 g, 25%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 4.49 (qd, J = 8.0 Hz, J = 8.0 Hz, 4H), 7.34 (d, J = 8.0 Hz, 2H), 7.71 (D, J = 8.0Hz, 2H)
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-75.8 (t, J = 8.0 Hz, 6F)
MS (EI): m / z (%) = 363 (M ⁺ , 83), 344 (26), 323 (79), 165 (54), 119 (100).
Melting point: 43-45 ° C.

[Reference Example 7]
Synthesis of bis (3-cyanophenyl) phosphate (2,2,2-trifluoroethyl)

Under a nitrogen atmosphere, 3-cyanophenol (35.0 g, 0.294 mol), toluene (240 ml) and triethylamine (62.5 g, 0.617 mol) were added to the flask and heated to 60 ° C. Under a nitrogen atmosphere, dichlorophosphoric acid (2,2,2-trifluoroethyl) (Synthesis according to Journal of Fluorine Chemistry, 2000, 104, 215-223: 31.1 g, 0.143 mol) was added dropwise. Stir at 19 ° C. for 19 hours. After completion of the reaction, the organic layer was washed with 5% aqueous sodium hydrogen carbonate solution, 5% aqueous sulfuric acid solution and water, and the organic layer was dried over sodium sulfate. After the desiccant was filtered off, the filtrate was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography (ethyl acetate / chloroform) and vacuum distillation to obtain the desired bis (3-cyanophenyl) phosphate (2,2,2-trifluoroethyl) as a colorless liquid. (47.2 g, 42%).
¹ H-NMR (400 MHz, CDCl ₃ ): δ 4.55 (qd, J = 8.0 Hz, J = 8.0 Hz, 2H), 7.49-7.59 (m, 8H).
¹⁹ F-NMR (376 MHz, CDCl ₃ ): δ-75.6 (t, J = 8.0 Hz, 3F).
MS (EI): m / z (%) = 382 (M ^<+> , 59), 244 (12), 220 (57), 119 (30), 102 (100).

[Example 1]
Ethylene carbonate (hereinafter abbreviated as EC) and dimethyl carbonate (hereinafter abbreviated as DMC) as a solvent were mixed at a weight ratio of 50:50, and bisphosphate (synthesized by the method shown in Reference Example 1) was mixed with this mixed solvent. 2,2,2-trifluoroethyl) phenyl was added at 2% by weight. Next, a nonaqueous electrolytic solution was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt at a concentration of 1.0 mol / L.

  Using this non-aqueous electrolyte, a coin cell type lithium ion secondary battery was prepared according to Preparation Example 1 described above, and a 50-cycle charge / discharge test was performed according to Test Example 1 described above. The results are shown in Table 1.

[Example 2]
A non-aqueous electrolyte was prepared in the same manner as in Example 1, a coin cell type lithium ion secondary battery was prepared in accordance with Preparation Example 2 described above, and a 50-cycle charge / discharge test was performed in accordance with Test Example 2 described above. The results are shown in Table 1.

[Example 3]
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that tris (2,2,2-trifluoroethyl) phosphate (hereinafter abbreviated as TFEP) was used instead of DMC. A coin cell type lithium ion secondary battery was prepared in the same manner, and a charge / discharge test was conducted. The results are shown in Table 1.

[Example 4]
Except for adding 2% by weight of bis (2,2,2-trifluoroethyl) phosphate (4-fluorophenyl) instead of bis (2,2,2-trifluoroethyl) phenyl phosphate A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 3, and a charge / discharge test was performed. The results are shown in Table 1.

[Example 5]
Instead of bis (2,2,2-trifluoroethyl) phenyl phosphate, 2% by weight of diphenyl phosphate (2,2,2-trifluoroethyl) synthesized by the method shown in Reference Example 2 was added. Except for this, a coin cell type lithium ion secondary battery was prepared in the same manner as in Example 3, and a charge / discharge test was conducted. The results are shown in Table 1.

[Example 6]
In addition to bis (2,2,2-trifluoroethyl) phosphate, vinylene carbonate (hereinafter abbreviated as VC) was added in a weight ratio of 2%, and the non-aqueous electrolyte was treated in the same manner as in Example 3. A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 2, and a charge / discharge test was performed. The results are shown in Table 1.

[Comparative Example 1]
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that bis (2,2,2-trifluoroethyl) phenyl phosphate was not added, and coin cell lithium was prepared in the same manner as in Example 1. An ion secondary battery was created and a charge / discharge test was performed. The results are shown in Table 1.

[Comparative Example 2]
A non-aqueous electrolyte was prepared in the same manner as in Example 2 except that bis (2,2,2-trifluoroethyl) phenyl phosphate was not added, and coin cell lithium was prepared in the same manner as in Example 2. An ion secondary battery was created and a charge / discharge test was performed. The results are shown in Table 1.

[Comparative Example 3]
A non-aqueous electrolyte was prepared in the same manner as in Example 3 except that bis (2,2,2-trifluoroethyl) phenyl phosphate was not added, and coin cell lithium was prepared in the same manner as in Example 3. An ion secondary battery was created and a charge / discharge test was performed. The results are shown in Table 1.

[Comparative Example 4]
A nonaqueous electrolytic solution was prepared in the same manner as in Example 3 except that 2% by weight of VC was added instead of bis (2,2,2-trifluoroethyl) phenyl phosphate, and this nonaqueous electrolytic solution was prepared. A coin cell type lithium ion secondary battery was prepared in accordance with the above-described Preparation Example 2 and a 50-cycle charge / discharge test was performed in accordance with the above-described Test Example 2. The results are shown in Table 1.

[Comparative Example 5]
The same as Example 1 except that 2% by weight of diethylphenyl phosphate having no fluorine atom in the ester side chain was added instead of bis (2,2,2-trifluoroethyl) phenyl phosphate. A coin cell type lithium ion secondary battery was prepared by the method described above and a charge / discharge test was conducted. The results are shown in Table 1.

[Comparative Example 6]
Similar to Example 3 except that 2% by weight of diethylphenyl phosphate having no fluorine atom in the ester side chain was added in place of bis (2,2,2-trifluoroethyl) phenyl phosphate. A coin cell type lithium ion secondary battery was prepared by the method described above and a charge / discharge test was conducted. The results are shown in Table 1.

  From Table 1, Example 1 using the EC-DMC mixed solvent as the nonaqueous solvent and the nonaqueous electrolytic solution according to the present invention containing the aryl group-containing fluorine-containing phosphate ester as the additive is 4.2 V. Under the charging / discharging conditions, a higher capacity retention rate was shown compared to Comparative Example 1 containing no additive or Comparative Example 5 containing diethylphenyl phosphate as an additive.

  Furthermore, in a test using a positive electrode active material that expresses a potential of 4.5 V or more on the positive electrode, the non-aqueous electrolysis according to the present invention containing an aryl group-containing fluorine-containing phosphate ester as an additive using an EC-DMC mixed solvent. Example 2 using the liquid showed a higher capacity retention rate than Comparative Example 2 containing no additive. Examples 3 to 5 using TFEP which is a fluorine-containing phosphate ester as non-aqueous solvent 2, Comparative Example 3 containing no additive, Comparative Example 4 using VC as an additive, and phosphoric acid as an additive Compared to Comparative Example 6 using diethylphenyl, a high capacity retention rate was exhibited. In addition, under the charge / discharge conditions at 4.5 V, Examples 3 to 5 using TFEP as the solvent 2 showed a higher capacity retention rate than Example 2 using DMC. Although this mechanism is not clear, it is thought that the lifetime was improved by the specific interaction of the aryl group-containing fluorine-containing phosphate ester such as forming a film complementary to TFEP. In addition, since Example 6 to which both the aryl group-containing fluorine-containing phosphate ester and VC are added exhibits a higher capacity retention rate, the aryl group-containing fluorine-containing phosphate ester and VC have different mechanisms of action and have a synergistic effect. It can be considered that the battery life is improved by manifesting.

[Example 7]
EC and TFEP were mixed at a weight ratio of 50:50 to add bis (2,2,2-trifluoroethyl) phenyl phosphate, and bis (2,2,2-trifluorophosphate) was added to the mixed solvent. Ethyl) phenyl was added at 0.1% by weight. The mixed electrolyte was subjected to a charge / discharge test in the same manner as in Example 2. The results are shown in Table 2.

[Example 8]
A charge / discharge test was conducted in the same manner as in Example 6 except that 5% by weight of bis (2,2,2-trifluoroethyl) phenyl phosphate was added. The results are shown in Table 2.

[Example 9]
A charge / discharge test was conducted in the same manner as in Example 6 except that 10% by weight of bis (2,2,2-trifluoroethyl) phenyl phosphate was added. The results are shown in Table 2.

  In Table 2, the test results in the case where the additive carried out in Comparative Example 3 is not included are also shown for reference.

  In Examples 7 to 9, the addition amount of the aryl group-containing fluorine-containing phosphate ester was changed and examined. As a result, it was found that when the aryl group-containing fluorine-containing phosphoric acid ester was added by 0.1% by weight, the capacity retention rate was improved as compared with the non-addition. However, compared with Example 3 described in Table 1, since the capacity is clearly reduced, it can be inferred that a sufficient effect cannot be obtained at less than 0.1%.

[Example 10]
A charge / discharge test was carried out in the same manner as in Example 3 except that lithium bis (trifluorosulfonyl) imide (LiN (CF ₃ SO ₂ ) ₂ , hereinafter abbreviated as LiTFSA in the table) was used as the electrolyte salt. The results are shown in Table 3.

[Example 11]
A charge / discharge test was performed in the same manner as in Example 9 except that triethyl phosphate (hereinafter abbreviated as TEP) was used instead of TFEP. The results are shown in Table 3.

[Example 12]
A charge / discharge test was conducted in the same manner as in Example 9 except that bis (2,2,2-trifluoroethyl) ethyl phosphate (hereinafter abbreviated as BFEP) was used instead of TFEP. The results are shown in Table 3.

[Example 13]
A charge / discharge test was performed in the same manner as in Example 9 except that bis (2,2,2-trifluoroethyl) methyl phosphate (hereinafter abbreviated as BFMP) was used instead of TFEP. The results are shown in Table 3.

[Comparative Example 7]
A charge / discharge test was conducted in the same manner as in Example 9 except that bis (2,2,2-trifluoroethyl) phenyl phosphate was not added. The results are shown in Table 3.

In Examples 10 to 13 and Comparative Example 7, LiTFSA, which is a kind of organic acid lithium salt, was used as the electrolyte. As a result, it was confirmed that the aryl group-containing fluorine-containing phosphoric acid ester improves the capacity retention rate not only with an inorganic acid lithium salt such as LiPF ₆ but also with an organic acid lithium salt such as LiTFSA.

  In Examples 11 to 13, the same effect can be obtained when TEP, which is a non-fluorinated phosphate ester, or BFEP or BFMP in which a fluorinated ester side chain and a non-fluorinated ester side chain coexist is used as a main solvent. I understood.

[Example 14]
EC and DMC were mixed as a solvent in a weight ratio of 50:50, and bis (2,2,2-trifluoroethyl phosphate) (3-fluorophosphate) synthesized by the method shown in Reference Example 3 was added to the mixed solvent. Phenyl) was added at 2% by weight. Next, a nonaqueous electrolytic solution was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt at a concentration of 1.0 mol / L.

  Using this non-aqueous electrolyte, a coin cell type lithium ion secondary battery was prepared according to the above-described Preparation Example 2, and a 50-cycle charge / discharge test was performed according to the above-described Test Example 2. The results are shown in Table 4.

[Example 15]
Instead of bis (2,2,2-trifluoroethyl) phosphate (3-fluorophenyl), bis (2,2,2-trifluoroethyl phosphate) synthesized by the method shown in Reference Example 4 (3- A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 14 except that methoxyphenyl was used, and a charge / discharge test was performed. The results are shown in Table 4.

[Example 16]
Instead of bis (2,2,2-trifluoroethyl) phosphate (3-fluorophenyl), bis (2,2,2-trifluoroethyl phosphate) synthesized according to the method shown in Reference Example 5 (3- A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 14 except that (cyanophenyl) was used, and a charge / discharge test was performed. The results are shown in Table 4.

[Example 17]
Instead of bis (2,2,2-trifluoroethyl phosphate) (3-fluorophenyl), bis (2,2,2-trifluoroethyl phosphate) synthesized according to the method shown in Reference Example 6 (4- A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 14 except that (cyanophenyl) was used, and a charge / discharge test was performed. The results are shown in Table 4.

[Example 18]
EC and TFEP as a solvent were mixed at a weight ratio of 50:50, and 2% by weight of bis (2,2,2-trifluoroethyl) phosphate (3-fluorophenyl) was added to the mixed solvent. did. Next, a nonaqueous electrolytic solution was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt at a concentration of 1.0 mol / L.

  Using this non-aqueous electrolyte, a coin cell type lithium ion secondary battery was prepared according to the above-described Preparation Example 2, and a 50-cycle charge / discharge test was performed according to the above-described Test Example 2. The results are shown in Table 4.

[Example 19]
Except for using bis (2,2,2-trifluoroethyl phosphate) (3-methoxyphenyl) instead of bis (2,2,2-trifluoroethyl phosphate) (3-fluorophenyl), A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 18, and a charge / discharge test was conducted. The results are shown in Table 4.

[Example 20]
Except for using bis (2,2,2-trifluoroethyl phosphate) (3-cyanophenyl) instead of bis (2,2,2-trifluoroethyl phosphate) (3-fluorophenyl), A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 18, and a charge / discharge test was conducted. The results are shown in Table 4.

[Example 21]
Except for using bis (2,2,2-trifluoroethyl) phosphate (4-cyanophenyl) instead of bis (2,2,2-trifluoroethyl) phosphate (3-fluorophenyl), A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 18, and a charge / discharge test was conducted. The results are shown in Table 4.

[Example 22]
Instead of bis (2,2,2-trifluoroethyl) phosphate (3-fluorophenyl), bis (3-cyanophenyl) phosphate (2,2,2-trifluorophosphate) synthesized by the method shown in Reference Example 7 A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 18 except that (fluoroethyl) was used, and a charge / discharge test was performed. The results are shown in Table 4.

[Example 23]
EC and TFEP as a solvent are mixed at a weight ratio of 50:50, and 2% by weight of bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl) is added to the mixed solvent. Further, 2% by weight of VC was added. Next, a nonaqueous electrolytic solution was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt at a concentration of 1.0 mol / L.

  Using this non-aqueous electrolyte, a coin cell type lithium ion secondary battery was prepared according to the above-described Preparation Example 2, and a 50-cycle charge / discharge test was performed according to Test Example 2. The results are shown in Table 4.

In Table 4, the test results of Examples 2 to 6 are also shown for reference.
From the comparison between Examples 14 to 17 and Example 2, the comparison between Examples 4 and 18 to 22 and Example 3, and the comparison between Example 23 and Example 6, an aryl group-containing fluorine-containing group having a substituent on the aryl group It was confirmed that the phosphoric acid ester has an improved capacity retention rate compared to the unsubstituted aryl group-containing fluorine-containing phosphoric acid ester. This result supports the result described earlier in the text, and by introducing a substituent that interacts with lithium to the aryl group, a protective film with high lithium permeability can be formed, maintaining the capacity. It is estimated that the rate has improved.

[Example 24]
EC and TFEP as a solvent were mixed at a weight ratio of 50:50, and bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl) phosphate was mixed at a weight ratio of 0.1 to this mixed solvent. % Was added. Next, a nonaqueous electrolytic solution was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt at a concentration of 1.0 mol / L.

  Using this non-aqueous electrolyte, a coin cell type lithium ion secondary battery was prepared according to the above-described Preparation Example 2, and a 50-cycle charge / discharge test was performed according to the above-described Test Example 2. The results are shown in Table 5.

[Example 25]
A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 24 except that 5% by weight of bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl) was added, A charge / discharge test was conducted. The results are shown in Table 5.

[Example 26]
A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 24 except that 10% by weight of bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl) was added. A charge / discharge test was conducted. The results are shown in Table 5.

In Table 5, the test results of Examples 7 to 9 and Comparative Example 3 are also shown for reference.
From the comparison between Examples 24-26 and Comparative Example 3, it was found that when the substituted aryl group-containing fluorine-containing phosphate ester was added at a weight ratio of 0.1%, the capacity retention ratio was improved as compared with the non-added case. Furthermore, from the comparison with the test results of Examples 7 to 9, it was confirmed that the substituted aryl group-containing fluorine-containing phosphate ester was more effective than the unsubstituted aryl group-containing fluorine-containing phosphate ester.

[Example 27]
EC and TFEP as a solvent are mixed at a weight ratio of 50:50, and 2% by weight of bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl) is added to the mixed solvent. did. Next, LiTFSA was dissolved as an electrolyte salt at a concentration of 1.0 mol / L to prepare a nonaqueous electrolytic solution.

  Using this non-aqueous electrolyte, a coin cell type lithium ion secondary battery was prepared according to the above-described Preparation Example 2, and a 50-cycle charge / discharge test was performed according to the above-described Test Example 2. The results are shown in Table 6.

[Example 28]
A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 27 except that TEP was used instead of TFEP as a solvent, and a charge / discharge test was performed. The results are shown in Table 6.

[Example 29]
A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 27 except that BFEP was used instead of TFEP as a solvent, and a charge / discharge test was performed. The results are shown in Table 6.

[Example 30]
A coin cell type lithium ion secondary battery was prepared in the same manner as in Example 27 except that BFMP was used instead of TFEP as a solvent, and a charge / discharge test was performed. The results are shown in Table 6.

In Table 6, the test results of Examples 10 to 13 and Comparative Example 7 are also shown for reference.
From the comparison of Examples 27 to 30, Examples 10 to 13, and Comparative Example 7, the substituted aryl group-containing fluorine-containing phosphate ester is similar to the unsubstituted aryl group-containing phosphate ester. The capacity retention rate is improved even when BFEP or BFMP in which TEP or a fluorine-containing ester side chain and a non-fluorine ester side chain coexist are used as a main solvent, and the effect is higher than that of an unsubstituted aryl group-containing phosphate ester. I understand.

[Example 31]
EC and ethyl methyl carbonate as a solvent were mixed at a weight ratio of 30:70, and bis (2,2,2-trifluoroethyl) phenyl phosphate was added at 10% by weight to the mixed solvent. Next, lithium hexafluorophosphate (LiPF ₆ ) was dissolved as an electrolyte salt at a concentration of 0.2 mol / L to prepare a nonaqueous electrolytic solution.

In this non-aqueous electrolyte, platinum as a working electrode, lithium foil as a reference electrode, and lithium foil as a counter electrode are inserted, and the voltage is increased from 3 to 6 V (vs. Li / Li ⁺ ) at a scanning speed of 5 mV / s. Sweep voltammetry measurements were performed. The apparatus was a multichannel potentiostat / galvanostat (VMP-3). From the measurement results, the potential when the current density was 0.1 mA / cm ² was defined as the oxidative decomposition potential. The results are shown in Table 7, and the linear sweep voltagram is shown in FIG.

[Example 32]
The same as Example 31 except that bis (2,2,2-trifluoroethyl) phosphate (3-methoxyphenyl) was used instead of bis (2,2,2-trifluoroethyl) phenyl phosphate. The linear sweep voltammetry measurement was performed by the method described above. From the measurement results, the potential when the current density was 0.1 mA / cm ² was defined as the oxidative decomposition potential. The results are shown in Table 7, and the linear sweep voltagram is shown in FIG.

[Comparative Example 8]
EC and ethyl methyl carbonate as a solvent were mixed at a weight ratio of 30:70. In the mixed solvent, lithium hexafluorophosphate (LiPF ₆ ) was dissolved as an electrolyte salt at a concentration of 0.2 mol / L to prepare a nonaqueous electrolytic solution.

In this non-aqueous electrolyte, platinum as a working electrode, lithium foil as a reference electrode, and lithium foil as a counter electrode are inserted, and the voltage is increased from 3 to 6.7 V (vs. Li / Li ⁺ ) at a scanning speed of 5 mV / s. A linear sweep voltammetry measurement was performed. From the measurement results, the potential when the current density was 0.1 mA / cm ² was defined as the oxidative decomposition potential. The results are shown in Table 7, and the linear sweep voltagram is shown in FIG.

  Although the reason why the cycle characteristics are improved by the electrolytic solution containing the aryl group-containing fluorine-containing phosphate ester is not clear, from the comparison between Example 31 and Example 32 and Comparative Example 8, the aryl group-containing fluorine-containing phosphoric acid It can be seen that the non-aqueous electrolyte containing the ester has a lower oxidative decomposition potential than the non-aqueous electrolyte containing no ester. In other words, the fluorine-containing phosphate ester containing an aryl group decomposes at a lower potential than the solvents (EC and ethyl methyl carbonate) to form a film on the positive electrode, and these films suppress further decomposition of the solvent. It is presumed that the battery performance has been improved by the effect of such as. In particular, it can be seen that the aryl group-containing fluorine-containing phosphate ester to which the methoxy group is bonded has a lower oxidative decomposition potential than the unsubstituted aryl group-containing fluorine-containing phosphate ester. Therefore, it is presumed that the aryl group-containing fluorine-containing phosphate ester to which the methoxy group is bonded has a higher effect of forming a film on the positive electrode at a lower potential and suppressing the decomposition of the solvent.

  By using the non-aqueous electrolyte containing the aryl group-containing fluorine-containing phosphate having a specific structure of the present invention, a non-aqueous secondary battery with improved cycle characteristics can be provided. In particular, in a lithium ion secondary battery, charge / discharge cycle characteristics are remarkably improved when charge / discharge is performed under a high voltage condition of 4.5 V or more on a lithium metal basis, which is extremely useful.

DESCRIPTION OF SYMBOLS 1 Positive electrode active material 2 Positive electrode collector 3 Positive electrode stainless steel cap 4 Negative electrode stainless steel cap 5 Negative electrode material 6 Negative electrode current collector 7 Stainless steel leaf spring 8 Inorganic filler containing polyolefin porous separator 9 Gasket

Claims (10)

A non-aqueous solvent;
Lithium salt,
The following general formula (1)

(In the formula, n is 1 or 2, and A is an unsubstituted or fluorine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a cyano group, or a linear or branched cyano group having 2 to 6 carbon atoms. Represents an aryl group or aralkyl group having 6 to 10 carbon atoms substituted by a substituent selected from the group consisting of an alkyl group and an alkoxy group having 1 to 6 carbon atoms, and Rf ¹ is a straight chain having 1 to 6 carbon atoms or A non-aqueous electrolyte solution containing an aryl group-containing fluorine-containing phosphate ester represented by: As the aryl group-containing fluorine-containing phosphate represented by the general formula (1), the following general formula (2)

(In the formula, n is 1 or 2, and R ^{1 to} R ⁵ each independently represents a hydrogen atom, a fluorine atom, a linear or branched alkyl group having 1 to 6 carbon atoms, a cyano group, or 2 to 2 carbon atoms. A straight-chain or branched cyanoalkyl group having 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and Rf ¹ represents a straight-chain or branched fluorine-containing alkyl group having 1 to 6 carbon atoms. The nonaqueous electrolytic solution according to claim 1, comprising: In the general formula (2), R ^{1 to} R ⁵ each independently represent a hydrogen atom, a fluorine atom, a cyano group, or an alkoxy group having 1 to 6 carbon atoms, and at least one is other than a hydrogen atom. Item 3. A nonaqueous electrolytic solution according to Item 2. In the general formula (2), R ^{1 to} R ⁵ each independently represent a hydrogen atom or an alkoxy group having 1 to 6 carbon atoms, and at least one is an alkoxy group having 1 to 6 carbon atoms. The non-aqueous electrolyte described in 1.   The nonaqueous electrolytic solution according to any one of claims 1 to 4, comprising a chain carbonate, a cyclic carbonate, or a mixture thereof as the nonaqueous solvent. The following general formula (3)

(In the formula, m is an integer of 0 to 3, R ⁶ represents a linear or branched alkyl group having 1 to 6 carbon atoms, and Rf ² represents a linear or branched alkyl group having 1 to 6 carbon atoms. The nonaqueous electrolytic solution according to any one of claims 1 to 5, further comprising a phosphoric acid ester represented by a fluorine alkyl group.   The content of the aryl group-containing fluorine-containing phosphate represented by the general formula (1) is 0.1 to 10% by weight with respect to the non-aqueous solvent. The non-aqueous electrolyte described.   The non-aqueous electrolyte further contains 0.1 to 10% by weight of one or more compounds selected from the group consisting of vinylene carbonate, fluoroethylene carbonate and vinyl ethylene carbonate with respect to the non-aqueous solvent. Item 8. The nonaqueous electrolytic solution according to any one of Items 1 to 7.   A nonaqueous secondary battery comprising a negative electrode, a positive electrode, a separator, and the nonaqueous electrolytic solution according to claim 1.   The non-aqueous secondary battery according to claim 9, wherein the positive electrode contains a positive electrode active material that expresses a potential of 4.5 V or more on a lithium metal basis.