JP2010245034A - Electrolyte for lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for increasing battery output and battery capacity of a lithium secondary battery by enhancing the ion conductivity of a lithium secondary battery. <P>SOLUTION: The electrolyte for a lithium secondary battery contains: (A) a negative electrode protection film forming agent comprising an azacrown ether compound having such structure that one or more of nitrogen atoms in an azacrown ether skeleton are bonded with an organic group (a) having a polymerizable unsaturated bond; (B) an electrolyte dissociation accelerator comprising a sulfoxide compound and/or an ether compound; and (C) an electrolyte, and preferably, the azacrown ether skeleton of the negative electrode protection film forming agent (A) is aza-12-crown-4, aza-14-crown-4, aza-15-crown-5, or aza-18-crown-6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrolyte solution for a lithium secondary battery. More specifically, the present invention relates to an electrolytic solution for a lithium secondary battery comprising a negative electrode protective film forming agent, an electrolyte dissociation accelerator, and an electrolyte.

  In recent years, there is an increasing demand for secondary batteries that can be repeatedly charged and discharged as power supply devices for electronic products such as mobile phones and personal computers. Among them, lithium secondary batteries are actively developed because they can be increased in voltage, reduced in size, and reduced in weight. Conventionally, for the purpose of increasing the battery output and battery capacity of a lithium secondary battery, attempts have been made to mix various additives into the electrolytic solution. For example, in order to prevent the carbonic acid ester used as the solvent for the electrolyte solution for lithium secondary batteries from being decomposed at the negative electrode and degrading the battery output and battery capacity characteristics, it is possible to polymerize such as vinylene carbonate and vinyl ethylene carbonate. It has been proposed to form a negative electrode protective film by adding a carbonate compound having an unsaturated bond to an electrolytic solution and electrolytically polymerizing vinylene carbonate or vinyl ethylene carbonate on the negative electrode (for example, Patent Documents 1 and 2). Further, it is known that by adding an ether compound having a high donor number to the electrolytic solution, dissociation of the electrolyte is promoted and lithium ion conductivity is improved (for example, Non-Patent Document 1).

JP 2003-151621 A JP 2003-031259 A

Zenkaku Okumi, “Technology of the latest secondary battery materials”, CMC Publishing, 2002, 120-123 pages

  However, since the negative electrode protective film produced from the carbonate compound having a polymerizable unsaturated bond described above is insufficient in the adhesion of the negative electrode protective film, it is difficult to sufficiently suppress the decrease in battery output and battery capacity. was there. Further, when the compound having a high donor number is added to the electrolyte solution for a lithium secondary battery, the dissociation of the electrolyte is promoted, while the solvation energy increases. Since the ions cannot be inserted and cannot be charged, there is a problem that the battery output and the battery capacity of the lithium secondary battery cannot be increased.

  An object of this invention is to provide the electrolyte solution which can increase the battery output and battery capacity of a lithium secondary battery by raising the ionic conductivity of a lithium secondary battery.

The inventors of the present invention have reached the present invention as a result of studies to achieve the above object. That is, the present invention is an electrolyte solution for a lithium secondary battery comprising the following (A) to (C) and a lithium secondary battery comprising the electrolyte solution;
(A) A negative electrode protective film forming agent comprising an azacrown ether compound having a structure in which one or more nitrogen atoms in the azacrown ether skeleton are bonded to an organic group (a) having a polymerizable unsaturated bond;
(B) an electrolyte dissociation accelerator comprising a sulfoxide compound and / or an ether compound;
(C) Electrolyte.

  The electrolytic solution for a lithium secondary battery of the present invention has an effect of increasing the battery output and the battery capacity of the lithium secondary battery and further improving the battery capacity retention rate.

  The electrolyte solution for a lithium secondary battery of the present invention comprises (A) an azacrown ether compound having a structure in which one or more nitrogen atoms in the azacrown ether skeleton are bonded to an organic group (a) having a polymerizable unsaturated bond. And (B) an electrolyte dissociation accelerator comprising a sulfoxide compound and / or an ether compound; (C) an electrolyte, with the symbols (A), (B), and (C) These elements are also referred to as a negative electrode protective film forming agent (A), an electrolyte dissociation accelerator (B), and an electrolyte (C), respectively, in the present specification.

  Examples of the azacrown ether skeleton forming the azacrown ether compound constituting the negative electrode protective film forming agent (A) in the present invention include 9- to 24-membered crown ether skeletons having 1 to 4 nitrogen atoms. It is done.

Examples of 9- to 24-membered crown ethers having 1 to 4 nitrogen atoms include aza-9-crown-3-ethers (4-aza-9-crown-3-ethers and 4,7-diaza-9s). -Crown-3-ether and the like), aza-12-crown-4-ether (such as 4-aza-12-crown-4-ether and 4,10-diaza-12-crown-4-ether), aza-14 -Crown-4-ether (such as 4-aza-14-crown-4-ether and 4,10-diaza-14-crown 4-ether), aza-15-crown-5-ether (4-aza-15- Crown-5-ether, 4,10-diaza-15-crown-5-ether, 4,14-diaza-15-crown-5 and 4,10,16-triaza-15-crown-5-ether ), Aza-18-crown-6-ether (4-aza-18-crown 6-ether, 4,10-diaza-18-crown-6-ether and 4,10,16-triaza-18-crown-6) -Ether etc.), aza-21-crown-7-ether (4-aza-21-crown-7-ether, 4,10-diaza-21-crown-7-ether and 4,10,16-triaza-21 -Crown-7-ether etc.) and aza-24-crown-8-ether (4-aza-24-crown-8-ether, 4,10-diaza-24-crown-8-ether and 4,10,16) -Triaza-24-crown-8-ether, etc.).
Of these, aza-12-crown-4-ether, aza-14-crown-4-ether, aza-15-crown-5-ether and aza- are preferred from the viewpoint of the coordination power with lithium ions. 18-crown-6-ether, more preferably 4-aza-12-crown-4-ether, 4,10-diaza-12-crown-4-ether, 4-aza-15-crown-5 Ether and 4,10-diaza-15-crown-5 ether.

  The number of nitrogen atoms in the azacrown ether skeleton is preferably 1 to 3, more preferably 1 or 2, from the viewpoint of coordination power to lithium ions.

  The organic group (a) having a polymerizable unsaturated bond in the present invention is an organic group having a polymerizable ethylenically unsaturated bond. For example, the group represented by the general formula (1), the general formula (2) , A (meth) acryloyloxyalkyl group, a (meth) acryloylalkyl group, and the like. Among these, the group represented by the general formula (1), the group represented by the general formula (2), and the (meth) acryloyloxyalkyl group are preferable from the viewpoint of easy formation of the negative electrode protective film.

In the formula, R is an alkylene group having 1 to 3 carbon atoms, Q ¹ , Q ² and Q ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a halogen atom or a fluoroalkyl group. , A cyano group, a carboxyl group, an alkoxy group or an alkoxycarbonyl group.
Examples of the alkylene group having 1 to 3 carbon atoms include a methylene group, an ethylene group, a 1,2-propylene group, and a 1,3-propylene group. Among these, a methylene group and an ethylene group are preferable from the viewpoint of compatibility with the electrolytic solution.
Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group and t-butyl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
Examples of the fluoroalkyl group include those in which 1 to 5 hydrogen atoms on a methyl group or an ethyl group are substituted with fluorine atoms. For example, a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, Examples thereof include a difluoroethyl group, a trifluoroethyl group, a tetrafluoroethyl group, and a pentafluoroethyl group.
As an alkoxy group, a C1-C3 alkoxy group, for example, a methoxy group, an ethoxy group, n-propoxy group, an isopropoxy group, etc. are mentioned.
Examples of the alkoxycarbonyl group include those having an alkoxy group having 1 to 3 carbon atoms, such as a methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, and an isopropoxycarbonyl group.

Preferred combinations of Q ¹ , Q ² and Q ³ include the following (1) to (6).
(1) Q ¹ = hydrogen atom, Q ² = hydrogen atom, Q ³ = phenyl group (2) Q ¹ = hydrogen atom, Q ² = hydrogen atom, Q ³ = alkoxycarbonyl group (3) Q ¹ = phenyl group, Q ² = hydrogen atom, Q ³ = phenyl group (4) Q ¹ = phenyl group, Q ² = hydrogen atom, Q ³ = alkoxycarbonyl group (5) Q ¹ = alkoxycarbonyl group, Q ² = hydrogen atom, Q ³ = Phenyl group (6) Q ¹ = alkoxycarbonyl group, Q ² = hydrogen atom, Q ³ = alkoxycarbonyl group Of these combinations, the combination of (2) is more preferred.

式中、Ｒは炭素数１〜３のアルキレン基であり、Ｑ⁴は水素原子又はハロゲン原子であり、Ｑ⁵、Ｑ⁶及びＱ⁷は、それぞれ独立して水素原子、炭素数が１〜４のアルキル基、フェニル基、ハロゲン原子、フルオロアルキル基、シアノ基、カルボキシル基、アルコキシ基又はアルコキシカルボニル基である。これらの基の具体例としては、前記のＲ、Ｑ¹、Ｑ²及びＱ³で例示した基と同じ基が挙げられる。Ｑ⁴の内、負極保護膜の形成し易さ及び重合性不飽和結合を有する有機基（ａ）の安定性の観点から好ましいのは、水素原子、フッ素原子及び塩素原子であり、更に好ましいのは水素原子である。

In the formula, R is an alkylene group having 1 to 3 carbon atoms, Q ⁴ is a hydrogen atom or a halogen atom, and Q ⁵ , Q ⁶ and Q ⁷ are each independently a hydrogen atom and 1 to 4 carbon atoms. Alkyl group, phenyl group, halogen atom, fluoroalkyl group, cyano group, carboxyl group, alkoxy group or alkoxycarbonyl group. Specific examples of these groups include the same groups as those exemplified for R, Q ¹ , Q ² and Q ³ above. Of Q ⁴ , a hydrogen atom, a fluorine atom, and a chlorine atom are preferable from the viewpoint of easy formation of a negative electrode protective film and stability of the organic group (a) having a polymerizable unsaturated bond, and more preferable. Is a hydrogen atom.

Of Q ^5, a hydrogen atom is preferable from the viewpoint of easy formation of the negative electrode protective film. Of Q ⁶ and Q ^7, a hydrogen atom and a methyl group are preferable from the viewpoint of easy formation of the negative electrode protective film, and a hydrogen atom is more preferable.

Preferred combinations of Q4, Q5, Q6 and Q7 include the following (1) to (12).
(1) Q4 = hydrogen atom, Q5 = hydrogen atom, Q6 = hydrogen atom, Q7 = hydrogen atom (2) Q4 = fluorine atom, Q5 = hydrogen atom, Q6 = hydrogen atom, Q7 = hydrogen atom (3) Q4 = chlorine Atom, Q5 = hydrogen atom, Q6 = hydrogen atom, Q7 = hydrogen atom (4) Q4 = hydrogen atom, Q5 = hydrogen atom, Q6 = methyl group, Q7 = hydrogen atom (5) Q4 = fluorine atom, Q5 = hydrogen atom Q6 = methyl group, Q7 = hydrogen atom (6) Q4 = chlorine atom, Q5 = hydrogen atom, Q6 = methyl group, Q7 = hydrogen atom (7) Q4 = hydrogen atom, Q5 = hydrogen atom, Q6 = hydrogen atom, Q7 = methyl group (8) Q4 = fluorine atom, Q5 = hydrogen atom, Q6 = hydrogen atom, Q7 = methyl group (9) Q4 = chlorine atom, Q5 = hydrogen atom, Q6 = hydrogen atom, Q7 = methyl group (10 Q4 = Hydrogen atom, Q5 = Hydrogen atom, Q6 = Me Q7 = methyl group (11) Q4 = fluorine atom, Q5 = hydrogen atom, Q6 = methyl group, Q7 = methyl group (12) Q4 = chlorine atom, Q5 = hydrogen atom, Q6 = methyl group, Q7 = methyl Group Among these combinations, the combination of (1) is more preferable.

  Examples of the (meth) acryloyloxyalkyl group in the organic group (a) having a polymerizable unsaturated bond in the present invention include a (meth) acryloyloxyethyl group and a (meth) acryloyloxymethyl group.

  The number of organic groups (a) having a polymerizable unsaturated bond in the azacrown ether compound in the present invention is 1 to 3, more preferably 1 or 2 from the viewpoint of ease of forming the negative electrode protective film. is there.

  Specific examples of the azacrown ether compound in the present invention include N- (methyl 2-butenoate) -4-aza-12-crown-4-ether, N, N-di- (methyl 2-butenoate) -4. , 10-diaza-12-crown-4-ether, N- (methyl 2-butenoate) -4-aza-15-crown-5-ether, N, N-di- (methyl 2-butenoate) -4 , 10-diaza-15-crown-5-ether, N- (cinnamyl) -4-aza-12-crown-4-ether, N, N-di- (cinnamyl) -4,10-diaza-12-crown -4-ether, N- (cinnamyl) -4-aza-15-crown-5-ether, N, N-di- (cinnamyl) -4,10-diaza-15-crown-5-ether, N- ( 4-vinylbenzyl) -4- The-12-crown-4-ether, N, N-di- (4-vinylbenzyl) -4,10-diaza-12-crown-4-ether, N- (4-vinylbenzyl) -4-aza- 15-crown-5-ether, N, N-di- (4-vinylbenzyl) -4,10-diaza-15-crown-5-ether, N, N-di- (1-acryloyloxyethyl) -4 , 10-diaza-15-crown-5-ether, N- (1-acryloyloxyethyl) -4-aza-14-crown-4-ether, N- (ethyl 2-pentenoate) -4-aza-18 -Crown-6-ether and N, N-di- (2-pentenoic acid methyl) -4,14-diaza-18-crown-6-ether.

  As the method for producing an azacrown ether compound in the present invention, a usual method can be used. For example, a method of reacting an unsubstituted azacrown ether with an alkyl halide having an organic group (a) having a polymerizable unsaturated bond in an organic solvent in the absence of a catalyst or in the presence of a catalyst. Examples of the organic solvent include nitrile organic solvents (acetonitrile, propiononitrile, benzonitrile, etc.), ketone organic solvents (acetone, methyl ethyl ketone, etc.), amide organic solvents (formamide, acetamide, dimethylformamide, dimethylacetamide, etc.) , Ether organic solvents (such as dimethyl ether, tetrahydrofuran and dioxane), ester organic solvents (such as ethyl acetate and diethyl maleate), sulfur-containing organic solvents (such as dimethyl sulfoxide and sulfolane), halogenated hydrocarbons (such as chloroform and dichloromethane) , Hydrocarbons (hexane, heptane, toluene, xylene, etc.) and mixtures of two or more of these solvents. Catalysts include alkali metal hydroxides (for example, lithium hydroxide, sodium hydroxide and potassium hydroxide), alkali metal carbonates (such as sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate) and alkali metal hydrides. (Such as sodium hydride and potassium hydride). The reaction temperature is usually 10 to 150 ° C., and the reaction time is usually 0.5 to 24 hours. After completion of the reaction, if necessary, the catalyst can be neutralized and treated with an adsorbent to remove and purify the catalyst.

  Examples of the halogenated alkyl having an organic group (a) having a polymerizable unsaturated bond include 4-bromo-2-butenoic acid methyl ester, 4-chloro-2-butenoic acid methyl ester, and 1-bromo-4- Cyano-2-butene, 1-chloro-4-cyano-2-butene, acrylic acid chloromethyl ester, acrylic acid bromomethyl ester, acrylic acid-2-chloroethyl ester, acrylic acid-2-bromoethyl ester, methacrylic acid Chloromethyl ester, methacrylic acid bromomethyl ester, methacrylic acid-2-chloroethyl ester, methacrylic acid-2-bromoethyl ester, cinnamilk chloride, cinnamyl bromide, 4- (chloromethyl) styrene, 4- (bromomethyl) styrene Etc.

  The negative electrode protective film forming agent (A) in the present invention is usually composed only of the azacrown ether compound.

  The electrolyte salt dissociation promoter (B) in the present invention comprises a sulfoxide compound and / or an ether compound, and examples of the sulfoxide compound include compounds represented by the general formula (3).

式中、Ｒ¹及びＲ²はそれぞれ独立して炭素数１〜５のアルキル基である。炭素数１〜５のアルキル基としては、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基及びｔ−ブチル基、ｎ−ペンチル基、イソペンチル基及び２，２−ジメチルプロピル基等が挙げられる。これらの内、電解液のイオン伝導性の観点から好ましいのはメチル基である。

In the formula, R ¹ and R ² are each independently an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group having 1 to 5 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and t-butyl group, n-pentyl group, isopentyl group and 2,2- A dimethylpropyl group etc. are mentioned. Among these, a methyl group is preferable from the viewpoint of ionic conductivity of the electrolytic solution.

  Specific examples of the sulfoxide compound include dimethyl sulfoxide, ethyl methyl sulfoxide, methyl n-propyl sulfoxide, butyl methyl sulfoxide, methyl pentyl sulfoxide, diethyl sulfoxide, ethyl isopropyl sulfoxide, n-butyl ethyl sulfoxide, ethyl n-pentyl sulfoxide, diisopropyl sulfoxide. N-butyl n-propyl sulfoxide, isopentyl n-propyl sulfoxide, di-n-butyl sulfoxide, butyl 2,2-dimethylpropyl sulfoxide, diisopentyl sulfoxide and the like.

  As a manufacturing method of a sulfoxide compound, the method of oxidizing and manufacturing the alkyl sulfide which has a C1-C5 alkyl with an oxidizing agent is mentioned. Examples of the oxidizing agent include hydrogen peroxide and perhalogenates (such as sodium perchlorate, sodium perbromate, and sodium periodate). The reaction temperature is usually 0 to 100 ° C., and the reaction time is usually 1 to 10 hours. After completion of the reaction, the oxidizing agent can be decomposed with a reducing agent (such as sodium thiosulfate and sodium hydrogensulfite) and then treated with an adsorbent to remove and purify the catalyst.

As said ether compound, the compound shown by General formula (4) is mentioned.
^{_{R 3 -O- (CH 2 CH 2}} O) n-R 4 (4)
In the formula, R ³ and R ⁴ are each independently an alkyl group having 1 to 5 carbon atoms, and n is a number from 1 to 10. As a C1-C5 alkyl group, the same thing as R < ¹ > and R < ² > in General formula (3) is mentioned. Of R ³ and R ^4, a methyl group is preferred from the viewpoint of coordination to lithium ions. n is preferably 1 or 2 from the viewpoint of the electrolyte solution viscosity.

  Specific examples of the ether compound include dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol dimethyl ether, penta Ethylene glycol diethyl ether, hexaethylene glycol ethyl methyl ether, hexaethylene glycol n-butylisopentyl ether, heptaethylene glycol isobutyl n-propyl ether, heptaethylene glycol ethyl 2,2-dimethylpropyl ether, octaethylene glycol ethyl n-propyl ether, Kuta ethylene glycol diisobutyl ether, nonaethylene glycol dimethyl ether, nonaethylene glycol t- butyl isopropyl ether, decaethylene glycol diisopropyl ether and decamethylene glycol 2,2-dimethylpropyl isopentyl ether, and the like. These can be obtained commercially.

As a manufacturing method of an ether compound, the method of manufacturing through the following processes is mentioned.
(1): A monohydric alcohol having 1 to 5 carbon atoms is charged into a pressurized reaction vessel, ethylene oxide is blown in the presence of no catalyst or a catalyst, and ethylene oxide is added in one step or multiple steps under normal pressure or pressure. Perform the reaction.
(2): The hydroxyl group of the ethylene oxide adduct of a monohydric alcohol having 1 to 5 carbon atoms obtained in (1) is etherified with an etherifying agent.

  As a catalyst for the addition reaction of a monohydric alcohol having 1 to 5 carbon atoms and ethylene oxide, an alkali catalyst [eg, alkali metal (such as lithium, sodium, potassium and cesium)], an acid [perhalogen acid (perchlorine) Acid, perbromic acid and periodic acid), sulfuric acid, phosphoric acid and nitric acid (preferably perchloric acid)] and their salts [preferably divalent or trivalent metals (Mg, Ca, Sr, Ba, Zn) , Co, Ni, Cu and Al). The reaction temperature is usually 50 to 150 ° C., and the reaction time is usually 2 to 20 hours. After completion of the addition reaction of ethylene oxide, the catalyst can be neutralized if necessary and treated with an adsorbent to remove and purify the catalyst.

  Examples of the catalyst for the etherification reaction of an ethylene oxide adduct of a monohydric alcohol having 1 to 5 carbon atoms include hydroxides of alkali catalysts [eg, alkali metals (lithium, sodium, potassium, cesium, etc.)]. Examples of the etherifying agent include alkyl chloride or alkyl bromide having 1 to 5 carbon atoms, such as methyl chloride, methyl bromide, ethyl chloride, ethyl bromide, n-propyl chloride, n-propyl bromide, and chloride. Isopropyl, isopropyl bromide, n-butyl chloride, n-butyl bromide, isobutyl chloride, isobutyl bromide, t-butyl chloride, t-butyl bromide, n-pentyl chloride, n-pentyl bromide, isopentyl chloride, odor And isopentyl chloride, 2,2-dimethylpropyl chloride and 2,2-dimethylpropyl bromide. The reaction temperature is usually 50 to 100 ° C., and the reaction time is usually 6 to 24 hours. The equivalent ratio of the etherifying agent to the ethylene oxide adduct of a monohydric alcohol having 1 to 5 carbon atoms is preferably 1 to 2. In the etherification reaction, a solvent such as toluene or benzene can be used as necessary. After completion of the reaction, the unreacted etherifying agent and solvent are distilled off under reduced pressure, the catalyst is neutralized, and the catalyst can be removed and purified by treatment with an adsorbent.

  Of the sulfoxide compounds and ether compounds, ether compounds are preferable from the viewpoint of battery capacity, and dimethoxyethane, diethoxyethane, diethylene glycol dimethyl ether and diethylene glycol diethyl ether are more preferable from the viewpoint of volatility and electrolyte viscosity.

The number of donors of the sulfide compound and the polyether compound in the present invention represents the affinity between the sulfide compound or the polyether compound and the electrolyte, and the coordination stabilization to SbCl _{5 in} 1,2-dichloroethane. It is a number obtained by measuring enthalpy (kcal / mol). As the number of donors of typical compounds, for example, those described in “V. Gutman, Hitoshi Ohtsuki, Isao Okada,“ Donor and Acceptor ”Society Publishing Center, published in 1983” can be used. The larger the number of donors, the higher the dissociation ability of the electrolyte. The number of donors of the sulfide compound and the polyether compound is preferably 16 to 40 for both the sulfide compound and the polyether compound, more preferably 20 to 30 from the viewpoint of the dissociation ability of the electrolyte and the ion transfer resistance at the electrode active material interface. It is. In order to increase the donor number of the sulfide compound in the present invention, the carbon number of the alkyl group having 1 to 5 carbon atoms of R ¹ and R ² in the general formula (3) may be decreased. In order to increase the number of donors of the ether compound in the present invention, the number of carbon atoms of the alkyl group having 1 to 5 carbon atoms of R ³ and R ⁴ in the general formula (4) may be decreased, and the number of n should be increased. That's fine. In order to reduce the number of donors in the ether compound, the number of carbon atoms in the alkyl group having 1 to 5 carbon atoms of R ³ and R ⁴ in the general formula (4) may be increased, and the number of n may be decreased. If the number of donors is 16 or more, the affinity with lithium ions is above a certain level, and the battery output does not decrease.

As the electrolyte (C) in the present invention, those used in ordinary electrolyte solutions for lithium secondary batteries can be used, for example, inorganic acids such as LiPF ⁶ , LiBF ⁴ , LiSbF ⁶ , LiAsF ⁶ and LiClO ^4. Examples thereof include lithium salts of organic acids such as lithium salts, LiN (CF ³ SO ² ) ² , LiN (C ² F ⁵ SO ² ) ² , and LiC (CF ³ SO ² ) ³ . Of these, LiPF ⁶ is preferable from the viewpoint of battery output.

  The electrolytic solution for a lithium secondary battery of the present invention contains a carbonate compound (D) having a polymerizable unsaturated bond in addition to the protective film forming agent (A), the dissociation accelerator (B) and the electrolyte (C). Also good. By containing (D), the electrolytic solution for a lithium secondary battery of the present invention increases battery capacity and battery output, and further improves battery capacity retention.

  When (D) is used alone instead of (A) as the negative electrode protective film forming agent, the lithium secondary battery cannot be charged. However, by using (A) and (D) together, (D) By promoting the negative electrode protective film forming effect of (A), it is considered that the battery capacity and the battery output are further increased and the battery capacity retention rate is improved as compared with the case where (A) is used alone.

Examples of the carbonate compound (D) having a polymerizable unsaturated bond include a chain carbonate compound (D1) having 4 to 7 carbon atoms and a cyclic carbonate compound (D2) having 3 to 9 carbon atoms. Among these, (D2) is preferable from the viewpoint of the cycle characteristics of the lithium secondary battery.
Examples of (D1) include methyl vinyl carbonate, ethyl vinyl carbonate, n-propyl vinyl carbonate, isopropyl vinyl carbonate, divinyl carbonate, allyl methyl carbonate, allyl ethyl carbonate, allyl n-propyl carbonate, allyl isopropyl carbonate, and diallyl carbonate. It is done. These can be obtained commercially.

  As a C3-C9 cyclic carbonate compound (D2), the compound shown by General formula (5) and the compound shown by following General formula (6) are mentioned.

式中、Ｒ⁵及びＲ⁶はそれぞれ独立して水素原子又は炭素数１〜３のアルキル基である。炭素数が１〜３のアルキル基としては、メチル基、エチル基、ｎ−プロピル基及びイソプロピル基が挙げられる。これらの内、リチウム二次電池のサイクル特性の観点から好ましいのは水素原子である。

In the formula, R ⁵ and R ⁶ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. Among these, a hydrogen atom is preferable from the viewpoint of the cycle characteristics of the lithium secondary battery.

  Specific examples of the compound represented by the general formula (5) include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, n-propyl vinylene carbonate, isopropyl vinylene carbonate, dimethyl vinylene carbonate, diethyl vinylene carbonate, and di-n-propyl vinylene carbonate. , Diisopropyl vinylene carbonate, ethyl methyl vinylene carbonate, ethyl n-propyl vinylene carbonate, and ethyl isopropyl vinylene carbonate. These can be obtained commercially.

式中、Ｒ⁷及びＲ⁸はそれぞれ独立して水素原子又は炭素数２〜３のアルケニル基であり、Ｒ⁷及びＲ⁸が同時に水素原子となることはない。炭素数が２〜３のアルケニル基としては、ビニル基及びアリル基が挙げられる。これらの内、リチウム二次電池のサイクル特性の観点から好ましいのは、Ｒ⁷及びＲ⁸の内の一方が水素原子で他方がビニル基である組み合わせ並びにＲ⁷及びＲ⁸が共にビニル基である組み合わせである。

In the formula, R ⁷ and R ⁸ are each independently a hydrogen atom or an alkenyl group having 2 to 3 carbon atoms, and R ⁷ and R ⁸ do not simultaneously become a hydrogen atom. Examples of the alkenyl group having 2 to 3 carbon atoms include a vinyl group and an allyl group. Among these, from the viewpoint of the cycle characteristics of the lithium secondary battery, a combination in which one of R ⁷ and R ⁸ is a hydrogen atom and the other is a vinyl group, and R ⁷ and R ⁸ are both vinyl groups. It is a combination.

  Specific examples of the compound represented by the general formula (6) include vinyl ethylene carbonate, allyl ethylene carbonate, divinyl ethylene carbonate, and diallyl ethylene carbonate. These can be obtained commercially.

  The electrolyte solution for a lithium secondary battery of the present invention may further contain a nonaqueous solvent and other additives as necessary.

  As the non-aqueous solvent, those used in ordinary electrolyte solutions for lithium secondary batteries can be used. For example, cyclic or chain carbonate ester, chain carboxylate ester, cyclic or chain ether, phosphate ester, Lactone compounds, nitrile compounds, amide compounds, and the like and mixtures thereof can be used. Examples of the cyclic carbonate include propylene carbonate, ethylene carbonate and butylene carbonate. Examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate. Examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate. Examples of the cyclic ether include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 1,4-dioxane and the like. Examples of the chain ether include dimethoxymethane and 1,2-dimethoxyethane. Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trichloromethyl) phosphate, Tri (trifluoroethyl) phosphate, tri (triperfluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphospholan-2-one, 2-trifluoroethoxy-1,3,2- Examples include dioxaphospholan-2-one and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one. Examples of the lactone compound include γ-butyrolactone and γ-valerolactone. A nitrile compound includes acetonitrile. Examples of the amide compound include dimethylformamide. Among the non-aqueous solvents, from the viewpoint of battery output, preferred are cyclic carbonates, chain carbonates and phosphate esters, and more preferred are cyclic carbonates.

  Examples of other additives include an overcharge inhibitor, a dehydrating agent, and a capacity stabilizer.

  Examples of the overcharge inhibitor include biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, aromatic compounds such as cyclohexylbenzene, t-butylbenzene, and t-amylbenzene. The usage-amount of an overcharge inhibiting agent is 0-5 weight% normally based on the total weight of the electrolyte solution for lithium secondary batteries, Preferably it is 0-3 weight%.

  Examples of the dehydrating agent include zeolite, silica gel and calcium oxide. The usage-amount of a dehydrating agent is 0-5 weight% normally based on the total weight of the electrolyte solution for lithium secondary batteries, Preferably it is 0-3 weight%.

  Examples of the capacity stabilizer include fluoroethylene carbonate, succinic anhydride, 1-methyl-2-piperidone, heptane, and fluorobenzene. The usage-amount of a capacity stabilizer is 0-5 weight% normally based on the total weight of the electrolyte solution for lithium secondary batteries, Preferably it is 0-3 weight%.

  In the electrolyte solution for a lithium secondary battery of the present invention, the negative electrode protective film forming agent (A), the electrolyte dissociation accelerator (B), the electrolyte (C), polymerizable unsaturated, based on the total weight of the electrolyte solution for the lithium secondary battery Preferable contents (% by weight) of the carbonate compound (D) having a bond, the nonaqueous solvent and other additives are as follows.

The negative electrode protective film-forming agent (A) is preferably 0.1 to 10% by weight, more preferably 2 to 5% by weight, from the viewpoint of ease of forming the negative electrode protective film and battery capacity.
The electrolyte dissociation accelerator (B) is preferably 3 to 99.6% by weight, more preferably 4 to 94.8% by weight from the viewpoint of battery output.
The electrolyte (C) is preferably 0.3 to 25% by weight, more preferably 3 to 10% by weight from the viewpoint of battery output.
The carbonate compound (D) having a polymerizable unsaturated bond is preferably 0 to 10% by weight, more preferably 0.2 to 3% from the viewpoints of the battery capacity, battery output and battery capacity retention of the lithium secondary battery. % By weight.
The non-aqueous solvent is preferably 0 to 90% by weight, and more preferably 0 to 75 parts by weight from the viewpoint of battery output.
The other additive is preferably 0 to 15% by weight, more preferably 0 to 9% by weight.

  As a method for preparing the electrolyte solution for a lithium secondary battery of the present invention, (A), (B), the electrolyte (C) and, if necessary, (D), a nonaqueous solvent and / or other additives are stirred. There is a method in which a mixing apparatus [for example, a mixing vessel with a stirring blade (blade shape: chi-shaped, three-stage paddle, etc.), etc.] is charged without any particular limitation in the order of addition and is uniformly dissolved under stirring. Moreover, it is preferable to dehydrate each raw material in advance when preparing the electrolytic solution so that the amount of water in the electrolytic solution is 50 ppm or less.

  The lithium secondary battery of this invention is obtained by inject | pouring the electrolyte solution for lithium secondary batteries of this invention in the battery can which accommodated the positive electrode, the negative electrode, and the separator, and sealing a battery can.

  As the positive electrode in the lithium secondary battery of the present invention, a slurry obtained by dispersing a positive electrode active material, a conductive agent and a binder in a solvent is applied to a positive electrode current collector with a coating device such as a bar coater. , Dried to remove the solvent, and if necessary, pressed with a press machine can be used.

As the positive electrode active material, composite oxides of lithium and transition metals (for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ and LiMn ₂ O ₄ ), transition metal oxides (for example, MnO ₂ and V ₂ O ₅ ), transition Examples thereof include metal sulfides (such as MoS ₂ and TiS ₂ ), and conductive polymers (such as polyaniline, polyvinylidene fluoride, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polycarbazole).
Examples of the conductive agent include graphite (for example, natural graphite and artificial graphite), carbon blacks (for example, carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black), metal powder (for example, aluminum) Powder and nickel powder), conductive metal oxides (such as zinc oxide and titanium oxide), and the like.

Examples of the binder include high molecular compounds such as starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, and polypropylene.
Examples of the solvent include 1-methyl-2-pyrrolidone, methyl ethyl ketone, dimethylformamide, dimethylacetamide, N, N-dimethylaminopropylamine, and tetrahydrofuran.
Examples of the current collector for positive electrode include aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass, and the like.

In the lithium secondary battery of the present invention, preferable contents (% by weight) of the positive electrode active material, the conductive agent, and the binder based on the total weight of the positive electrode are as follows.
The content (% by weight) of the positive electrode active material is preferably 70 to 100% by weight, and more preferably 90 to 98% by weight. The content (% by weight) of the conductive agent is preferably 0 to 30% by weight, and more preferably 0 to 10% by weight. The content (% by weight) of the binder is preferably 0 to 30% by weight, and more preferably 0 to 10% by weight.

  The amount (% by weight) of the solvent used in the slurry of the positive electrode active material, the conductive agent and the binder is preferably 20 to 70% by weight based on the total weight of the positive electrode active material, the conductive agent and the binder. More preferably, it is 30 to 50% by weight.

As the negative electrode in the lithium secondary battery of the present invention, a negative electrode active material, a conductive agent and a binder dispersed in a solvent and applied to a negative electrode current collector with a coating device such as a bar coater, What was dried and removed the solvent, and what was pressed with the press if necessary can be used.
Examples of the negative electrode active material include graphite, polymer compound fired bodies (for example, those obtained by firing and carbonizing phenol resin and furan resin), cokes (for example, pitch coke, needle coke, and petroleum coke), carbon fiber, and conductivity. Examples thereof include polymers (for example, polyacetylene and polypyrrole), metal alloys (for example, lithium-aluminum alloy, lithium-aluminum-manganese alloy), and the like.
As the conductive agent, the binder and the solvent, the same materials as those used for the production of the positive electrode can be used.
Examples of the current collector for the negative electrode include copper, stainless steel, nickel, aluminum, titanium, calcined carbon, conductive polymer, conductive glass, and an aluminum-cadmium alloy.

  In the lithium secondary battery of the present invention, the preferred contents (% by weight) of the negative electrode active material, the conductive agent and the binder based on the total weight of the negative electrode are the positive electrode active material, the conductive agent and the positive electrode based on the total weight of the positive electrode. It is the same as each preferable content (weight%) of a binder.

  The amount (% by weight) of the solvent used in the slurry of the negative electrode active material, the conductive agent and the binder is the same as the amount (% by weight) of the solvent used in the slurry of the positive electrode active material, the conductive agent and the binder. .

  As the separator in the lithium secondary battery of the present invention, polyethylene, a microporous film of a polypropylene film, a multilayer film of a porous polyethylene film and polypropylene, a non-woven fabric made of polyester fiber, aramid fiber, glass fiber, and the like, and those Examples thereof include those having ceramic fine particles such as silica, alumina and titania attached to the surface.

  As the battery can in the lithium secondary battery of the present invention, metal materials such as stainless steel, iron, aluminum and nickel-plated steel can be used, but plastic materials can also be used depending on the battery application. Further, the battery can can be formed into a cylindrical shape, a coin shape, a square shape, or any other shape depending on the application.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, unless otherwise specified, “%” represents “% by weight” and “parts” represents “parts by weight”.

<Production Example 1>
Production of positive electrode;
After thoroughly mixing 9.0 parts of LiCoO ₂ powder, 0.5 part of Ketjen Black [manufactured by Aldrich Co., Ltd.] and 0.5 part of polyvinylidene fluoride [manufactured by Aldrich Co., Ltd.] in a mortar, 1-methyl- 7.0 parts of 2-pyrrolidone [manufactured by Tokyo Chemical Industry Co., Ltd.] was added and further mixed well in a mortar to obtain a slurry. The obtained slurry was applied to one side of an aluminum electrolytic foil having a thickness of 20 μm using a wire bar in the atmosphere, dried at 100 ° C. for 15 minutes, and further under reduced pressure (10 mmHg) at 80 ° C. for 5 minutes. By drying, 1-methyl-2-pyrrolidone was removed, and a positive electrode having a thickness of 30 μm was produced.

<Production Example 2>
Production of negative electrode;
92.5 parts of graphite powder having an average particle size of about 8 to 12 μm, 7.5 parts of polyvinylidene fluoride, and 200 parts of 1-methyl-2-pyrrolidone [manufactured by Tokyo Chemical Industry Co., Ltd.] are thoroughly mixed in a mortar to obtain a slurry. Obtained. The obtained slurry was applied to one side of a copper foil having a thickness of 20 μm, dried at 100 ° C. for 15 minutes to remove 1-methyl-2-pyrrolidone, punched to 12 mmφ, and made 30 μm thick with a press. A negative electrode was produced.

<Production Example 3>
Production of battery cans for lithium secondary batteries;
The positive electrode and the negative electrode obtained in Production Examples 1 and 2 are arranged at both ends in the 2032 type coin cell so that the respective coated surfaces face each other, and “Celguard # 3501” [manufactured by Celgard Co., Ltd.] is used as a separator between the two electrodes. Was inserted to prepare a battery can for a lithium secondary battery.

<Production Example 4>
N- (methyl 2-butenoate) -4-aza-15-crown-5-ether [hereinafter referred to as (A-1). ] Synthesis;
To a flask equipped with a stirrer, thermometer and condenser, 4-aza-15-crown-5-ether [manufactured by Tokyo Chemical Industry Co., Ltd.] 1.2 parts (5.6 mmol), 4-bromo-2- 1 part (5.6 mmol) of butenoic acid methyl ester [manufactured by Tokyo Chemical Industry Co., Ltd.] and 10 parts of acetonitrile were charged and dissolved uniformly with stirring, and then reacted at room temperature for 24 hours with stirring. After the acetonitrile was removed under reduced pressure (10 mmHg), the reaction product was purified by an alumina column [150 mesh, Blockman 1, standard grade, manufactured by Aldrich Co., Ltd.] using acetone as a solvent, and 1.4 parts of (A-1) (4. 4 mmol) was obtained (yield 79%). (A-1) is bonded to an organic group (a) having a polymerizable unsaturated bond in which R is a methylene group, Q ¹ and Q ² are hydrogen atoms, and Q ³ is a methoxycarbonyl group in the general formula (1). The azacrown ether compound.

<Production Example 5>
N, N-di- (2-methyl butenoate) -4,10-diaza-15-crown-5-ether [hereinafter referred to as (A-2). ] Synthesis;
Instead of 1.2 parts of 4-aza-15-crown-5-ether, 0.61 part (2.8 mmol) of 4,10-diaza-15-crown-5-ether [manufactured by Tokyo Chemical Industry Co., Ltd.] Except having used, it carried out similarly to manufacture example 4, and obtained 0.85 part (2.0 mmol) of (A-2) (yield 71%). (A-2) is bonded to the organic group (a) having a polymerizable unsaturated bond in which R is a methylene group, Q ¹ and Q ² are hydrogen atoms, and Q ³ is a methoxycarbonyl group in the general formula (1). Diaza crown ether compound.

<Production Example 6>
N, N-di- (1-acryloyloxyethyl) -4,10-diaza-15-crown-5-ether [hereinafter referred to as (A-3). ] Synthesis;
Production Example 4 except that 0.76 part (5.6 mmol) of acrylic acid-2-chloroethyl ester [manufactured by Tokyo Chemical Industry Co., Ltd.] was used instead of 1 part of 4-bromo-2-butenoic acid methyl ester In the same manner, 0.60 part (1.9 mmol) of (A-3) was obtained (yield 68%). (A-3) is a diaza crown ether compound in which the organic group (a) having a polymerizable unsaturated bond is an acryloyloxyethyl group and is bonded to the organic group.

<Production Example 7>
N, N-di- (4-vinylbenzyl) -4,10-diaza-15-crown-5-ether [hereinafter referred to as (A-4). ] Synthesis;
Production Example 4 except that 4- (chloromethyl) styrene [manufactured by Tokyo Chemical Industry Co., Ltd.] 0.85 part (5.6 mmol) was used instead of 1 part of 4-bromo-2-butenoic acid methyl ester. Similarly, 0.90 part (1.99 mmol) of (A-4) was obtained (yield 71%). (A-4) is an organic group (a) having a polymerizable unsaturated bond in which R is a methylene group and Q ⁴ , Q ⁵ , Q ⁶ and Q ⁷ are hydrogen atoms in the general formula (2) It is a diaza crown ether compound bound by

<Production Example 8>
N, N-dicinnamyl-4,10-diaza-15-crown-5-ether [hereinafter referred to as (A-5). ] Synthesis;
In the same manner as in Production Example 4 except that 0.85 part (5.6 mmol) of cinnamilk chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 1 part of 4-bromo-2-butenoic acid methyl ester ( A-5) 0.92 part (2.0 mmol) was obtained (yield 73%). (A-5) is bonded to an organic group (a) having a polymerizable unsaturated bond in which R is a methylene group, Q ¹ and Q ² are hydrogen atoms, and Q ³ is a phenyl group in the general formula (1). It is a diaza crown ether compound.

<Examples 1-5>
Production of evaluation lithium secondary battery;
Dimethoxyethane which is an electrolyte dissociation accelerator (B) [a compound in which R ³ and R ⁴ are methyl groups and n = 1 in the general formula (4). Hereinafter abbreviated as DME. The number of donors = 24] 81 parts, and 3 parts of ethylene carbonate and 3 parts of diethyl carbonate as a non-aqueous solvent were mixed with 10 parts of LiPF ₆ as an electrolyte (C) to prepare an electrolyte solution. To 97 parts of the obtained electrolyte solution, 3 parts of any of the protective film forming agents (A-1) to (A-5) obtained in Production Examples 4 to 8 were added, and the mixture was stirred until uniform and transparent. A secondary battery electrolyte was prepared. The obtained electrolyte solution for a lithium secondary battery was put into the battery can for lithium secondary battery prepared in Production Example 3, and the battery can was sealed to prepare lithium secondary batteries for evaluation of Examples 1 to 5 [lithium secondary Content of (A) in secondary battery electrolyte: 3 wt%, content of (B): 81 wt%, content of (C): 10 wt%, content of nonaqueous solvent: 6 wt%] .

<Example 6>
Production of evaluation lithium secondary battery;
The electrolyte dissociation accelerator (B) is changed from DME to dimethyl sulfoxide [a compound in which R ¹ and R ² are methyl groups in the general formula (3). Hereinafter abbreviated as DMSO. A lithium secondary battery for evaluation was produced in the same manner as in Example 1 except that the number of donors was changed to 30] [Content of (A) in electrolyte solution for lithium secondary battery: 3% by weight, (B) Content: 81 wt%, (C) content: 10 wt%, non-aqueous solvent content: 6 wt%].

<Example 7>
Production of evaluation lithium secondary battery;
The electrolyte dissociation accelerator (B) is changed from DME to dibutyl sulfoxide [a compound in which R ¹ and R ² are butyl groups in the general formula (3). Hereinafter, abbreviated as DBSO. A lithium secondary battery for evaluation was produced in the same manner as in Example 1 except that the number of donors was changed to 27] [Content of (A) in the electrolyte solution for lithium secondary battery: 3 wt%, (B) Content: 81 wt%, (C) content: 10 wt%, non-aqueous solvent content: 6 wt%].

<Example 8>
Production of evaluation lithium secondary battery;
The electrolyte dissociation accelerator (B) is changed from DME to diethylene glycol diethyl ether [a compound in which R ³ and R ⁴ are ethyl groups and n = 2 in the general formula (4). Hereinafter, abbreviated as DEG. A lithium secondary battery for evaluation was produced in the same manner as in Example 1 except that the number of donors was changed to 22] [Content of (A) in the electrolyte solution for lithium secondary battery: 3% by weight, (B) Content of 81 wt%, content of (C): 10 wt%, content of non-aqueous solvent: 6 wt%].

<Example 9>
Production of evaluation lithium secondary battery;
The electrolyte dissociation accelerator (B) is changed from DME to triethylene glycol diethyl ether [a compound in which R ³ and R ⁴ are ethyl groups and n = 3 in the general formula (4). Hereinafter abbreviated as TAGE. A lithium secondary battery for evaluation was produced in the same manner as in Example 1 except that the number of donors was changed to 25] [Content of (A) in electrolyte solution for lithium secondary battery: 3 wt%, (B) Content: 81 wt%, (C) content: 10 wt%, non-aqueous solvent content: 6 wt%].

<Example 10>
Production of evaluation lithium secondary battery;
The electrolyte dissociation accelerator (B) is changed from DME to decaethylene glycol dipentyl ether [in the general formula (4), R ³ and R ⁴ are pentyl groups, and n = 10. Hereinafter, it is abbreviated as DEGP. A lithium secondary battery for evaluation was produced in the same manner as in Example 1 except that the number of donors was changed to 25] [Content of (A) in electrolyte solution for lithium secondary battery: 3 wt%, (B) Content: 81 wt%, (C) content: 10 wt%, non-aqueous solvent content: 6 wt%].

<Example 11>
Production of evaluation lithium secondary battery;
Add 3 parts of LiPF ₆ as the electrolyte (C) and 2 parts of the protective film forming agent (A-1) obtained in Production Example 4 to 95 parts of DME which is the electrolyte dissociation accelerator (B), and stir until uniform and transparent. Then, an electrolyte for a lithium secondary battery was prepared. The obtained electrolyte solution for lithium secondary battery was put into the battery can for lithium secondary battery prepared in Production Example 3, and the battery can was sealed to produce a lithium secondary battery for evaluation of Example 11 [lithium secondary battery Content of (A) in the electrolyte for use: 2% by weight, content of (B): 95% by weight, content of (C): 3% by weight].

<Example 12>
Production of evaluation lithium secondary battery;
Except for changing 95 parts of DME to 75 parts, 3 parts of LiPF ₆ to 20 parts, and 2 parts of (A-1) to 5 parts, evaluation lithium secondary batteries were evaluated in the same manner as in Example 11. A secondary battery was produced [content of (A) in electrolyte solution for lithium secondary battery: 5 wt%, content of (B): 75 wt%, content of (C): 20 wt%].

<Example 13>
Production of evaluation lithium secondary battery;
Evaluation lithium secondary for evaluation as in Example 11 except that 95 parts of DME were changed to 65 parts, 3 parts of LiPF ₆ were changed to 25 parts, and 2 parts of (A-1) were changed to 10 parts A battery was produced [content of (A) in electrolyte solution for lithium secondary battery: 10 wt%, content of (B): 65 wt%, content of (C): 25 wt%].

<Example 14>
Production of evaluation lithium secondary battery;
Example 11 except that 95 parts of DME were changed to 99.6 parts, 3 parts of LiPF ₆ were changed to 0.3 parts, and 2 parts of (A-1) were changed to 0.1 parts. Thus, a lithium secondary battery for evaluation was produced [content of (A) in electrolyte solution for lithium secondary battery: 0.1 wt%, content of (B): 99.6 wt%, inclusion of (C) Amount: 0.3% by weight].

<Example 15>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was produced in the same manner as in Example 1 except that 10 parts of LiPF ₆ was changed to 10 parts of LiN (CF ³ SO ² ) ² [Containing (A) in Lithium Secondary Battery Electrolyte] Amount: 3 wt%, (B) content: 81 wt%, (C) content: 10 wt%, non-aqueous solvent content: 6 wt%].

<Example 16>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was prepared in the same manner as in Example 1 except that 95 parts of DME were changed to 29 parts, and 3 parts each of ethylene carbonate and diethyl carbonate as nonaqueous electrolyte were changed to 29 parts each [ Content of (A) in electrolyte solution for lithium secondary battery: 3% by weight, content of (B): 29% by weight, content of (C): 10% by weight, content of non-aqueous solvent: 58% by weight %].

<Example 17>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was prepared in the same manner as in Example 1 except that 3 parts of (A-1) was changed to 2 parts and 1 part of vinylene carbonate was added as the carbonate compound (D). Content of (A) in secondary battery electrolyte: 2% by weight, content of (B): 81% by weight, content of (C): 10% by weight, content of (D): 1% by weight, Content of non-aqueous solvent: 6% by weight].

<Example 18>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was prepared in the same manner as in Example 1 except that 3 parts of (A-1) was changed to 2 parts and 1 part of di-n-propyl vinylene carbonate was added as the carbonate compound (D). [(A) content in electrolyte for lithium secondary battery: 2 wt%, (B) content: 81 wt%, (C) content: 10 wt%, (D) content: 1 wt%, non-aqueous solvent content: 6 wt%].

<Example 19>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was produced in the same manner as in Example 1 except that 3 parts of (A-1) was changed to 2 parts and 1 part of vinyl ethylene carbonate was added as the carbonate compound (D). Content of (A) in electrolyte solution for secondary battery: 2% by weight, content of (B): 81% by weight, content of (C): 10% by weight, content of (D): 1% by weight Non-aqueous solvent content: 6% by weight].

<Example 20>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was prepared in the same manner as in Example 1 except that 3 parts of (A-1) was changed to 2 parts and 1 part of divinyl carbonate was added as the carbonate compound (D). Content of (A) in secondary battery electrolyte: 2% by weight, content of (B): 81% by weight, content of (C): 10% by weight, content of (D): 1% by weight, Content of non-aqueous solvent: 6% by weight].

<Example 21>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was prepared in the same manner as in Example 1 except that 3 parts of (A-1) were changed to 2.8 parts and 0.2 part of vinylene carbonate was added as the carbonate compound (D). [Content of (A) in electrolyte for lithium secondary battery: 2.8% by weight, content of (B): 81% by weight, content of (C): 10% by weight, content of (D) Amount: 0.2% by weight, non-aqueous solvent content: 6% by weight].

<Example 22>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was prepared in the same manner as in Example 1 except that 3 parts of (A-1) was changed to 0.1 part and 2.9 parts of vinylene carbonate was added as the carbonate compound (D). [The content of (A) in the electrolyte for a lithium secondary battery: 0.1 wt%, the content of (B): 81 wt%, the content of (C): 10 wt%, the content of (D) Amount: 2.9% by weight, content of non-aqueous solvent: 6% by weight].

<Comparative Example 1>
Production of evaluation lithium secondary battery;
The electrolyte solution prepared in the same manner as in Example 1 was used as it was [without adding (A)] to produce a lithium secondary battery for evaluation of Comparative Example 1 [(A) in an electrolyte for a lithium secondary battery] Content: 0 wt%, (B) content: 84 wt%, (C) content: 10 wt%, non-aqueous solvent content: 6 wt%].

<Comparative example 2>
Production of evaluation lithium secondary battery;
To 97 parts of the electrolyte solution prepared in the same manner as in Example 1, 3 parts of vinylene carbonate was added instead of (A-1) and stirred until uniform and transparent, and a lithium secondary battery for evaluation of Comparative Example 2 was produced. [Content of (A) in electrolyte solution for lithium secondary battery: 0 wt%, content of (B) 81 wt%, content of (C): 10 wt%, content of nonaqueous solvent: 6 % By weight, vinylene carbonate content: 3% by weight].

<Comparative Example 3>
Production of evaluation lithium secondary battery;
In a mixture of 43.5 parts of ethylene carbonate and 43.5 parts of diethyl carbonate, 10 parts of LiPF ₆ as an electrolyte (C) was dissolved to prepare an electrolyte solution. To 97 parts of the obtained electrolyte solution, 3 parts of vinylene carbonate was added instead of (A), and the mixture was stirred until it became uniformly transparent to prepare an electrolyte solution for a lithium secondary battery. The obtained electrolyte solution for a lithium secondary battery was put in the battery can for lithium secondary battery prepared in Production Example 3, and the battery can was sealed to produce a lithium secondary battery for evaluation of Comparative Example 3 [lithium secondary battery (A) content in electrolyte solution: 0 wt%, (B) content 0 wt%, (C) content: 10 wt%, non-aqueous solvent content: 87 wt%, vinylene carbonate Content: 3% by weight].

<Comparative example 4>
Production of evaluation lithium secondary battery;
A lithium secondary battery for evaluation was produced in the same manner as in Comparative Example 3 except that 3 parts of vinylene carbonate was changed to 3 parts of (A-1) [Content of (A) in electrolyte solution for lithium secondary battery: 3 wt%, (B) content 0 wt%, (C) content: 10 wt%, non-aqueous solvent content: 87 wt%].

  An evaluation lithium secondary battery using the electrolyte solution for lithium secondary battery of the present invention prepared in Examples 1 to 22 as an ion conductor, and an evaluation using an electrolyte solution prepared in Comparative Examples 1 to 4 as an ion conductor The battery capacity, battery output, and battery capacity retention rate of the lithium secondary battery were measured by the following methods. The results are shown in Tables 1-3.

<Method for measuring battery capacity>
After putting the lithium secondary battery in a constant temperature bath of 50 ° C., using a charge / discharge measuring device “Battery Analyzer 1470 type” [manufactured by Toyo Technica Co., Ltd.], a voltage of 0 V to 3 V at a current of 0.2 mA / cm ^2. The battery voltage was discharged to 0 V with a current of 0.2 mA / cm ² after 10 minutes of rest, and this charging / discharging was repeated 10 times, and the average value of the discharge capacity at this time was defined as the battery capacity.

<Measurement method of battery output>
Using a charge / discharge measurement device “Battery Analyzer 1470” [manufactured by Toyo Technica Co., Ltd.], charge so that SOC (State of charge, the ratio of the capacity in a fully charged state to the capacity at a predetermined time) is 60%. Then, discharge at a constant current and read the voltage after 10 seconds. This operation is performed with several current values, and the current value is plotted on the horizontal axis and the voltage value after 10 seconds is plotted on the vertical axis to create an approximate line, and the current value (I3. The battery output is calculated from the following formula.
Battery output (W) = I3.0V × 3.0

<Evaluation of battery capacity retention>
Using a charge / discharge measuring device “Battery Analyzer 1470 type” [manufactured by Toyo Technica Co., Ltd.], the battery is charged from 0 V to 2 V with a current of 0.2 mA / cm ² , and after resting for 10 minutes, 0.2 mA / cm ^The battery voltage was discharged to 0 V with a current of ² , and this charge / discharge was repeated 50 cycles. At this time, the battery capacity at the first charge and the battery capacity at the 50th cycle charge are measured, and the battery capacity retention rate is calculated from the following formula. A larger numerical value indicates a higher battery capacity retention rate.
Battery capacity retention rate (%) = (battery capacity at the 50th cycle charge / battery capacity at the first charge) × 100

  All of the lithium ion secondary batteries using the electrolytic solution containing the protective film forming agent (A), the electrolyte dissociation accelerator (B) and the electrolyte (C) as an ion conductor showed high battery output. Moreover, the lithium ion secondary battery (Comparative Example 1) and the protective film forming agent (A) containing the electrolytic solution containing only the electrolyte dissociation accelerator (B) and not containing the protective film forming agent (A) are converted into vinylene carbonate. The lithium ion secondary battery (Comparative Example 2) containing the changed electrolyte solution could not be charged. This is because if the protective film forming agent (A) is not present in the electrolytic solution, the coordinating force of (B) is too large, and therefore desolvation does not proceed when lithium ions are inserted between the graphite layers of the negative electrode. This is probably because of this. Moreover, although it was possible to charge / discharge even if it used the electrolyte solution which does not contain an electrolyte dissociation promoter (B), the output characteristics were inferior compared with the lithium ion secondary battery containing (B). This result is considered because the ionic conductivity of the electrolytic solution is improved by the presence of (B).

  The electrolyte for a lithium secondary battery of the present invention promotes dissociation of the electrolyte by the electrolyte salt dissociation accelerator (B) and improves the ionic conductivity, and forms a protective film on the negative electrode surface by the negative electrode protective film forming agent (A). Then, the battery output and the battery capacity of the lithium secondary battery are increased by promoting the desorption of the dissociation promoter (B) coordinated to lithium ions.

  Since the electrolyte solution for lithium secondary batteries of the present invention is excellent in battery output, battery capacity, and battery capacity retention rate, it is useful as an electrolyte solution for secondary batteries for mobile phones and personal computers. Moreover, the lithium secondary battery using the electrolytic solution of the present invention is useful as an in-vehicle secondary battery such as an electric vehicle.

Claims (9)

An electrolytic solution for a lithium secondary battery comprising the following (A) to (C):
(A) A negative electrode protective film forming agent comprising an azacrown ether compound having a structure in which one or more nitrogen atoms in the azacrown ether skeleton are bonded to an organic group (a) having a polymerizable unsaturated bond;
(B) an electrolyte dissociation accelerator comprising a sulfoxide compound and / or an ether compound;
(C) Electrolyte.   The electrolyte solution for a lithium secondary battery according to claim 1, further comprising a carbonate compound (D) having a polymerizable unsaturated bond. The electrolysis for a lithium secondary battery according to claim 1 or 2, wherein the organic group (a) is a group represented by the general formula (1), a group represented by the general formula (2), or a (meth) acryloyloxyalkyl group. liquid.

(In the formula, R is an alkylene group having 1 to 3 carbon atoms, and Q ¹ , Q ² and Q ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a halogen atom, A fluoroalkyl group, a cyano group, a carboxyl group, an alkoxy group or an alkoxycarbonyl group.)

(In the formula, R is an alkylene group having 1 to 3 carbon atoms, Q ⁴ is a hydrogen atom or a halogen atom, and Q ⁵ , Q ⁶ and Q ⁷ are each independently a hydrogen atom, having 1 to 4 carbon atoms. An alkyl group, a phenyl group, a halogen atom, a fluoroalkyl group, a cyano group, a carboxyl group, an alkoxy group or an alkoxycarbonyl group.)   The azacrown ether skeleton is aza-12-crown-4, aza-14-crown-4, aza-15-crown-5 or aza-18-crown-6. Electrolyte for lithium secondary battery.   The electrolyte solution for a lithium secondary battery according to any one of claims 1 to 4, wherein the electrolyte dissociation accelerator (B) is a sulfoxide compound having a donor number of 16 to 40 and / or an ether compound having a donor number of 16 to 40. . The said sulfoxide compound is a sulfoxide compound shown by General formula (3), The electrolyte solution for lithium secondary batteries in any one of Claims 1-5.

(In the formula, R ¹ and R ² are each independently an alkyl group having 1 to 5 carbon atoms.) The electrolyte solution for a lithium secondary battery according to any one of claims 1 to 6, wherein the ether compound is an ether compound represented by the general formula (4).
_{^{R 3 -O- (CH 2 CH 2}} O) n-R 4 (4)
(Wherein, R ³ and R ⁴ are each independently an alkyl group of 1 to 5 carbon atoms, n is the number of 1 to 10.) The electrolyte solution for a lithium secondary battery according to any one of claims 2 to 7, wherein the carbonate compound (D) is a compound represented by the general formula (5) and / or a compound represented by the general formula (6).

(In the formula, R ⁵ and R ⁶ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.)

(In the formula, R ⁷ and R ⁸ are each independently a hydrogen atom or an alkenyl group having 2 to 3 carbon atoms, and R ⁷ and R ⁸ are not both hydrogen atoms.)     The lithium secondary battery formed by containing the electrolyte solution for lithium secondary batteries in any one of Claims 1-8.