JP2016162523A - Electrolytic solution for nonaqueous secondary battery and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an electrolytic solution for a nonaqueous secondary battery capable of improving flame retardancy while suppressing a deterioration in battery performance of a battery; and a secondary battery including the electrolytic solution for a nonaqueous secondary battery.SOLUTION: An electrolytic solution for a nonaqueous secondary battery contains: at least one phosphazene compound selected from the group consisting of a compound represented by formula (A1) and a compound represented by formula (A2); at least one cyclopropane compound selected from the group consisting of a compound represented by formula (I-1), a compound represented by formula (II-1) and a compound represented by formula (III-1); an electrolyte; and a nonaqueous solvent.SELECTED DRAWING: None

Description

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

  Lithium ion secondary batteries can achieve a large energy density in charge and discharge compared to lead batteries and nickel cadmium batteries. Utilizing this characteristic, application to portable electronic devices such as mobile phones and notebook personal computers is widespread. Accordingly, as a power source for portable electronic devices, development of a secondary battery that is particularly lightweight and capable of obtaining a high energy density is in progress. Further, there is a strong demand for miniaturization, weight reduction, long life, and reliability. High reliability is essential for applications such as electric vehicles and power storage equipment, which are expected to increase in capacity in the future, and there is a strong demand for both battery performance and reliability.

  As an electrolytic solution for a lithium ion secondary battery, a combination of a carbonate-based solvent such as propylene carbonate or diethyl carbonate and an electrolyte salt such as lithium hexafluorophosphate is widely used. This is because these substances have high conductivity and are stable in potential.

  On the other hand, since such a low molecular weight combustible organic compound is contained in the component, it is important to impart flame retardancy from the viewpoint of reliability. For the purpose of this improvement, a technique for containing a phosphazene compound in an electrolytic solution has been proposed (see Patent Document 1).

International Publication No. 2013/047342 Pamphlet

In recent years, it is necessary to achieve not only flame retardancy but also various battery performances, and there has been a demand for a battery in which deterioration of battery characteristics does not occur even when charging and discharging are repeated. In addition, it is preferable that it is a battery with a high discharge capacity maintenance factor as a battery in which the said battery characteristic does not deteriorate.
When the present inventors evaluated the characteristic using the cyclic compound described in Patent Document 1, the present flame retardant and battery performance levels are satisfied, but flame retardant at a higher level than required recently. Therefore, further improvement was necessary.
The present invention has been made in view of such a situation, and an electrolyte for a non-aqueous secondary battery capable of improving flame retardancy while suppressing a decrease in battery performance of the battery, and the non-aqueous secondary It is an object of the present invention to provide a secondary battery including a battery electrolyte.

The above problem has been solved by the following means.
(1) at least one phosphazene compound selected from the group consisting of a compound represented by formula (A1) described later and a compound represented by formula (A2) described later;
Selected from the group consisting of a compound represented by formula (I-1) described later, a compound represented by formula (II-1) described later, and a compound represented by formula (III-1) described later At least one cyclopropane compound;
Electrolyte,
An electrolyte for a non-aqueous secondary battery containing a non-aqueous solvent.
(2) The electrolyte solution for nonaqueous secondary batteries according to (1), wherein the content of the cyclopropane compound is 10 parts by mass or more and 120 parts by mass or less with respect to 100 parts by mass of the phosphazene compound.
(3) The electrolyte solution for nonaqueous secondary batteries according to (1) or (2), wherein X in formula (I-1) is a cyano group, an alkoxycarbonyl group, or a carbamoyl group.
(4) The electrolyte solution for nonaqueous secondary batteries in any one of (1)-(3) whose R < ¹¹ > -R < ¹⁴ > is a hydrogen atom in Formula (I-1).
(5) The electrolyte solution for nonaqueous secondary batteries according to any one of (1) to (4), wherein X in formula (I-1) is a cyano group or an alkoxycarbonyl group.
(6) The electrolyte solution for non-aqueous secondary batteries according to any one of (1) to (5), wherein -L ¹¹ -R ^{15 in} formula (I-1) is -COOR ¹⁶ .
R ¹⁶ represents a carbonyl group, an ether group, or an alkyl group having 1 to 6 carbon atoms that may intervene —NR ¹⁷ —. R ¹⁷ represents a hydrogen atom or an alkyl group.
(7) The electrolyte for a nonaqueous secondary battery according to any one of (1) to (6), wherein the ring formed by L ²¹ in formula (II-1) contains —CONR ²⁵ — or —COO—. . R ²⁵ represents an alkyl group or an aryl group.
(8) The nonaqueous secondary battery according to any one of (1) to (7), wherein the compound represented by the formula (II-1) is a compound represented by the formula (II-2) described later. Electrolyte.
(9) The electrolyte solution for nonaqueous secondary batteries according to any one of (1) to (7), wherein the ring formed by L ²¹ in formula (II-1) is a 5-membered ring or a 6-membered ring.
(10) In any one of (1) to (9), the linking group formed by (L ³¹ ) n in formula (III-1) is a carbonyloxy group, an oxycarbonyl group, or —CO—NR ³⁵ —. The electrolyte solution for non-aqueous secondary batteries as described.
(11) The electrolysis for nonaqueous secondary battery according to any one of (1) to (10), wherein L ³² in formula (III-1) is an alkylene group, an oxygen atom, a sulfur atom, or —NR ³⁵ —. liquid. R ³⁵ represents an alkyl group or an aryl group.
(12) The compound represented by formula (III-1) is a compound represented by formula (III-2) described later or a compound represented by formula (III-3) described later (1) to (11) The electrolyte solution for nonaqueous secondary batteries in any one of.
(13) The electrolyte solution for nonaqueous secondary batteries according to any one of (1) to (12), wherein L ³² is an alkylene group having 1 to 3 carbon atoms.
(14) The electrolyte solution for nonaqueous secondary batteries according to any one of (1) to (13), wherein L ³² is a methylene group.
(15) The electrolysis for a nonaqueous secondary battery according to any one of (1) to (14), wherein the compound represented by the formula (A1) is a compound represented by the formula (A1-1) described later. liquid.
(16) The electrolyte solution for nonaqueous secondary batteries according to (15), wherein Ra ⁴¹ is a dialkylamino group.
(17) Further, it contains at least one selected from the group consisting of aromatic compounds, halogen-containing compounds, polymerizable compounds, sulfur-containing compounds, silicon-containing compounds, nitrile compounds, boron-containing compounds, and imide compounds. (1) The electrolyte solution for nonaqueous secondary batteries in any one of (16).
(18) The nonaqueous secondary liquid according to any one of (1) to (17), wherein the concentration of the phosphazene compound is 1% by mass to 20% by mass with respect to the total mass of the electrolyte solution for the nonaqueous secondary battery. Secondary battery electrolyte.
(19) The non-aqueous solution according to any one of (1) to (18), wherein the concentration of the cyclopropane compound is 1% by mass to 15% by mass with respect to the total mass of the electrolyte solution for the non-aqueous secondary battery. Secondary battery electrolyte.
(20) A nonaqueous secondary battery comprising a positive electrode, a negative electrode, and the electrolyte solution for a nonaqueous secondary battery according to any one of (1) to (19).

  The electrolyte solution for a non-aqueous secondary battery of the present invention can suppress capacity deterioration during charge and discharge and improve flame retardancy in a secondary battery equipped with the same.

It is sectional drawing which shows typically the mechanism of the lithium secondary battery which concerns on preferable embodiment of this invention. It is sectional drawing which shows the specific structure of the lithium secondary battery which concerns on preferable embodiment of this invention.

The electrolyte solution for non-aqueous secondary batteries of this invention contains a phosphazene compound and a cyclopropane compound. Hereinafter, it demonstrates in detail centering on preferable embodiment of this invention.
In this specification, when there are a plurality of substituents or linking groups indicated by a specific symbol, or when a plurality of substituents etc. (the definition of the number of substituents is the same) is specified simultaneously or alternatively The respective substituents may be the same as or different from each other. Further, when a plurality of substituents and the like are close to each other, they may be bonded to each other or condensed to form a ring.

A feature of the present invention is that a phosphazene compound and a cyclopropane compound are used in combination.
The cyclopropane compound functions to maintain the effect of improving the flame retardancy of the phosphazene compound and suppress the influence on the battery performance. This is because the phosphazene compound oxidized on the positive electrode accelerates the deterioration of the battery. However, when the cyclopropane compound is used in combination, the cyclopropane ring is opened, reacting with the reactive oxidized phosphazene compound, and deactivated. It is understood that this has the effect of suppressing the chain reaction. The opening of the cyclopropane ring is more likely to occur when it has a specific substituent X having the property of attracting electrons.
In addition, the electrolyte solution for non-aqueous secondary batteries of this invention adapts to the use conditions in the high voltage severe to deterioration, and exhibits said outstanding performance.

<Phosphazene Compound (A)>
As the phosphazene compound (A), a compound represented by the following formula (A1) or the following formula (A2) is preferable.

In formula (A1) and formula (A2), Ra ^{11 to} Ra ¹⁶ and Ra ^{21 to} Ra ²⁸ each independently represent a monovalent substituent. In the adjacent Ra ¹¹ to Ra ¹⁶ and Ra ^{21 to} Ra ²⁸ , the substituents may form a ring.
The Ra ¹¹ to Ra ¹⁶ and ^Ra 21 ^{to Ra 28,} halogen atom (a fluorine atom is particularly desirable), alkyl group (1 to 12 carbon atoms are preferred, from 1 to 6 carbon atoms are more preferred, and 1 to 3 carbon atoms Particularly preferred), an alkoxy group (preferably having 1 to 12 carbon atoms, more preferably having 1 to 6 carbon atoms, and particularly preferably having 1 to 3 carbon atoms), a thioalkoxy group (preferably having 1 to 12 carbon atoms, and 1 to 1 carbon atoms). 6 is more preferable, carbon number 1 to 3 is particularly preferable), an aryloxy group (preferably 6 to 22 carbon atoms, more preferably 6 to 14 carbon atoms), and an arylthio group (preferably 6 to 22 carbon atoms are preferable). 6 to 14 are more preferable), an aralkyl group (preferably 7 to 23 carbon atoms, more preferably 7 to 15 carbon atoms), an amino group (preferably 0 to 6 carbon atoms, preferably 0 to 3 carbon atoms). Preferred) can be mentioned.
Ra ^{11 to} Ra ¹⁶ and Ra ^{21 to} Ra ²⁸ are more preferably an alkoxy group, an aryloxy group, a halogen atom, and an amino group. As alkoxy groups, unsubstituted alkoxy groups such as methoxy group, ethoxy group, butoxy group, 2,2,2-trifluoroethoxy group, 1,1,1,3,3,3-hexafluoroisopropoxy group, perfluoro group A fluorine-substituted alkoxy group such as a butylethyl group is preferred. As the aryloxy group, a phenoxy group and a fluorine-substituted phenoxy group are preferable.
In Formula (A1), 3 to 6 (preferably 4 or 5, more preferably 5) of Ra ^{11 to} Ra ¹⁶ are fluorine atoms, and 0 to 3 (preferably 1 or 2 or more). It is preferable that one is preferably an alkoxy group, an aryloxy group, a halogen atom, or an amino group.
In Formula (A2), 5 to 8 (preferably 6 or 7, more preferably 7) of Ra ^{21 to} Ra ²⁸ are fluorine atoms, and 0 to 3 (preferably 1 or 2 or more). It is preferable that one is preferably an alkoxy group, an aryloxy group, a halogen atom, or an amino group.
When Ra ^{11 to} Ra ¹⁶ and Ra ^{21 to} Ra ²⁸ are amino groups, the structure is represented by the following formula:

Ra ³¹ and Ra ³² are each independently a monovalent substituent, preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and an alkyl group having 1 to 3 carbon atoms. Particularly preferred. Ra ³¹ and Ra ³² may be bonded to each other or condensed to form a ring. At this time, a hetero atom such as a nitrogen atom, an oxygen atom, or a sulfur atom may be incorporated. The ring to be formed is preferably a 5-membered ring or a 6-membered ring. The 5-membered ring is preferably a compound containing a nitrogen-containing 5-membered ring, such as pyrrole, imidazole, pyrazole, indazole, indole, benzimidazole, pyrrolidine, imidazolidine, pyrazolidine, indoline, carbazole, or derivatives thereof (all N substitution). Examples of the 6-membered ring include piperidine, morpholine, piperazine, and derivatives thereof (all are N-substituted).

  The compound represented by the above formula (A1) is preferably a compound represented by the following formula (A1-1) or the following formula (A1-2).

Ra ⁴¹ and Ra ⁴² have the same meaning as Ra ^11, and are preferably an alkoxy group, an aryloxy group, a halogen atom, or an amino group. From the viewpoint of imparting flame retardancy to the electrolytic solution, Ra ⁴¹ and Ra ⁴² are preferably an alkoxy group or a dialkylamino group, and more preferably a dialkylamino group.

  In the formula (A1), the compound represented by the formula (A1-1) is more preferable from the viewpoint of imparting flame retardancy to the electrolytic solution.

  Preferred specific examples of the compound having a structure represented by the formula (A1) are shown below. Me represents a methyl group, Et represents an ethyl group, and Ph represents a phenyl group.

A phosphazene compound may be used individually by 1 type, or may be used in combination of 2 or more type.
The concentration of the phosphazene compound in the electrolyte solution for non-aqueous secondary batteries is not particularly limited, but may be 1% by mass or more based on the total mass of the electrolyte solution for non-aqueous secondary batteries (the total amount including the electrolyte). Preferably, it is more preferably 3% by mass or more, and particularly preferably 5% by mass or more. The upper limit is preferably 20% by mass or less, more preferably 15% by mass or less, and particularly preferably 10% by mass or less. By blending the phosphazene compound at the lower limit or higher, sufficient flame retardancy can be imparted. By blending the phosphazene compound below this upper limit, it is possible to suppress a decrease in battery performance.

A commercially available phosphazene compound can be used, or it can be modified into a compound having a desired structure. As a method for introducing a specific substituent into a phosphazene compound, for example, an alkoxy-substituted fluorinated phosphazene includes a compound represented by (PNF ₂ ) _n and R-OM (wherein R is an alkyl group, M Represents an alkali metal) or an alcohol represented by R—OH (wherein R is as defined above), non-catalyst, or basic such as sodium carbonate or potassium carbonate. A method of reacting in the presence of a catalyst has been proposed (Japanese Patent Application Laid-Open No. 2009-161559, Japanese Patent Application Laid-Open No. 2001-335590, Japanese Patent Application Laid-Open No. 2001-139594, pamphlet of International Publication No. 03/005479, special table). 2001-516492). As for the synthesis of a fluorinated phosphazene substituted with an amino group, a method of reacting a compound represented by (PNF ₂ ) _n with 2 equivalents of an amine (Journal of the Chemical Society [Section] A: Inorganic, Physical , Theoretical, 1970, p.2324-2329).

<Cyclopropane compound (B)>
As the cyclopropane compound, a compound represented by the following formula (I-1), a compound represented by the following formula (II-1), and a compound represented by the following formula (III-1) are preferable.

[Compound represented by Formula (I-1)]

· ^R 11 ~R ¹⁴
In the formula, R ^{11 to} R ¹⁴ each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a fluorine atom, a carbonyl group-containing group, or a cyano group. Specific examples of the alkyl group, aryl group, and alkoxy group include examples of the substituent T described below. R ^{11 to} R ¹⁴ may be bonded to each other or condensed to form a ring structure. R ^{11 to} R ¹⁴ may further have a substituent, and examples of the substituent include examples of the substituent T described below. Especially, it is especially preferable that R < ¹¹ > -R < ¹⁴ > is a hydrogen atom.

・ R ¹⁵
R ¹⁵ represents a substituent having 1 to 7 carbon atoms, preferably a substituent having 1 to 5 carbon atoms. R ¹⁵ may be a hydrocarbon substituent composed of only carbon atoms and hydrogen atoms, but may be a substituent containing O (oxygen atom), N (nitrogen atom) or S (sulfur atom). R ¹⁵ may be linear or branched, and may be cyclic or linear. R ¹⁵ may be composed only of a saturated bond or may have an unsaturated bond. When it is cyclic, it may be an aromatic ring, an aliphatic ring, an aromatic heterocyclic ring, or an aliphatic heterocyclic ring. When R ¹⁵ contains O or N, examples of the atomic group containing O include an ether group (—O—), a carbonyl group (—CO—), a carbonyloxy group (—COO—), and the like. Examples of the atomic group containing N include an imino group (—NR ¹⁷ —: R ¹⁷ is a hydrogen atom or an alkyl group, and a preferred range will be described later), an amide group (—CONR ¹⁷ —), and the like.

・ L ¹¹
L ¹¹ represents an alkylene group (preferably having 1 to 3 carbon atoms) or a carbonyl group. The alkylene group may have a substituent, and the substituent T described below is preferable.
Incidentally, ^-L 11 ^{-R 15} of formula (I-1) is preferably a -COOR ^16. The definition of R ¹⁶ will be described in detail later.

・ X
X represents an electron withdrawing group. The electron-withdrawing group is a substituent having an electron-withdrawing property due to an electronic effect, and using the Hammett's rule substituent constant σp, which is a measure of the electron-withdrawing property and electron-donating property of the substituent, It is a substituent having a σp value of 0 or more. Hammett's rule was established in 1935 by L.L. in order to quantitatively discuss the effect of substituents on the reaction or equilibrium of benzene derivatives. P. A rule of thumb proposed by Hammett, which is widely accepted today. Substituent constants determined by Hammett's rule include a σp value and a σm value, and these values can be found in many general books. A. Dean, “Lange's Handbook of Chemistry”, 12th edition, 1979 (Mc Graw-Hill) and “Areas of Chemistry”, 122, 96-103, 1979 (Nankodo), Corwin Hansch, A . LEO and R.M. W. TAFT “A Survey of Hammett Substitute Students and Resonance and Field Parameters” Chem. Rev. 1991, 91, 165-195. In this embodiment, each substituent is limited or explained by Hammett's substituent constant σp. However, this is limited only to a substituent having a known value found in the above-mentioned book. Needless to say, it also includes a substituent that would be included in the range when the value is unknown based on the Hammett rule even if the value is unknown.

  The substituent constant σp value is preferably 0.1 to 1.0, more preferably 0.2 to 1.0, and most preferably 0.3 to 1.0.

Specific examples of the substituent for X include a cyano group (—CN), an alkoxycarbonyl group (—COOR ¹⁶ ), and a carbamoyl group (—CON (R ¹⁸ ) ₂ ).
R ¹⁶ represents a C 1-6 alkyl group that may intervene with a carbonyl group (—CO—), an ether group (—O—), or an imino group (—NR ¹⁷ —). R ¹⁶ is preferably an alkyl group having no hetero atom, more preferably a methyl group, an ethyl group, an i-propyl group, or a t-butyl group. R ¹⁶ may have a substituent, and examples of the substituent include substituent T described below.
R ¹⁷ represents a hydrogen atom or an alkyl group. When R ¹⁷ is an alkyl group, it preferably has 1 to 4 carbon atoms, and more preferably a methyl group, an ethyl group, an i-propyl group, or a t-butyl group. R ¹⁷ may have a substituent, and examples of the substituent include substituent T described below.
R ¹⁸ represents a group having the same meaning as R ¹⁷ .
X is preferably a cyano group (—CN) or an alkoxycarbonyl group (—COOR ¹⁶ ), and more preferably a cyano group (—CN).

  The σp values for some of the exemplified substituents are shown below.

In addition, although the function of each said substituent or coupling group is not definitive, it is estimated as follows. The linking group L ^11, alkylene group, by a carbonyl group, work potential adjustment action is considered to be able to effectively coat formed in the range of operating potential in the secondary battery. Among these, when L ¹¹ is a carbonyl group, it is considered that the electron withdrawing property further acts to improve the film forming property. Further, it is presumed that the terminal substituent of R ¹⁵ contributes to the stabilization of lithium ions in the formed film.

  Specific examples of the compound represented by formula (I-1) are shown below, but the present embodiment is not construed as being limited thereto. Me represents a methyl group, Et represents an ethyl group, and tBu represents a t-butyl group.

  The compound represented by the above formula (I-1) can be synthesized by a conventional method. Specifically, the procedure described in JP2013-110102A can be referred to.

[Compound represented by Formula (II-1)]

・ R ^{21 to} R ²⁴
In the formula, R ^{21 to} R ²⁴ each independently represent a hydrogen atom or a substituent, and preferably each independently, a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a fluorine atom, a carbonyl group-containing group, or a cyano group. Indicates. Specific examples of the alkyl group, aryl group, and alkoxy group include examples of the substituent T described below. R ^{21 to} R ²⁴ may be bonded to each other or condensed to form a ring structure. R ^{21 to} R ²⁴ may further have a substituent, and examples of the substituent include examples of the substituent T described below.
Among these, R ^{21 to} R ²⁴ are preferably a hydrogen atom, an alkyl group, a fluorine atom, a carbonyl group-containing group, or a cyano group, and particularly preferably a hydrogen atom or an alkyl group.
Examples of the alkyl group include the substituent T described later, preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms, a methyl group, an ethyl group, an isopropyl group, A butyl group or a benzyl group is particularly preferred.
As the aryl group, an aryl group having 6 to 26 carbon atoms is preferable, and a phenyl group is particularly preferable.
As an alkoxy group, a C1-C20 alkoxy group is preferable, a C1-C10 alkoxy group is more preferable, a C1-C6 alkoxy group is further more preferable, a methoxy group, an ethoxy group, an isopropoxy group, Or a tertiary butoxy group is particularly preferable.
As the carbonyl group-containing group, an alkylcarbonyl group, an amide group, or an alkoxycarbonyl group is preferable, and a methylcarbonyl group, an ethylcarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, an isopropoxycarbonyl group, or a tertiary butoxycarbonyl group is particularly preferable. preferable.

・ L ²¹
L ²¹ represents an atomic group forming a ring structure together with the carbon atom of the cyclopropyl group and the carbonyl group. The ring formed by L ²¹ may be any of an aromatic hydrocarbon ring, an aliphatic hydrocarbon ring, an aromatic heterocyclic ring, and an aliphatic heterocyclic ring, but preferably a heterocyclic ring (aromatic heterocyclic ring and aliphatic heterocyclic ring). An aliphatic heterocyclic ring is more preferable. Although the hetero atom which comprises a heterocyclic ring is not specifically limited, An oxygen atom, a nitrogen atom, and a sulfur atom are mentioned, It is preferable that it is an oxygen atom or a nitrogen atom. The ring formed by L ²¹ may have a substituent, and examples of the substituent include a substituent T described below. Note that the aliphatic hydrocarbon ring and the aliphatic heterocyclic ring may contain an unsaturated bond.

In L ²¹ , the ring formed together with the carbon atom of the cyclopropyl group and the carbonyl group (C═O) in the formula preferably contains —CONR ²⁵ — or —COO—. Here, R ²⁵ represents an alkyl group (preferably having 1 to 5 carbon atoms) or an aryl group (preferably having 6 to 24 carbon atoms). Specific examples of the alkyl group or aryl group herein include the following examples of the substituent T. R ²⁵ may further have a substituent, and examples of the substituent include examples of the substituent T described below.

  The compound represented by the formula (II-1) is preferably a compound represented by the following formula (II-2).

・ R ^{21 to} R ²⁴
R ^{21 to} R ²⁴ have the same meaning as in formula (II-1).

・ L ²²
In the formula, L ²² represents an atomic group that forms a ring structure with the carbon atoms of the two carbonyl groups and the cyclopropyl group in the formula. The preferred range of the ring formed by L ²² is the same as L ²¹ , and any of an aromatic hydrocarbon ring, an aliphatic hydrocarbon ring, an aromatic heterocyclic ring, and an aliphatic heterocyclic ring may be used. Ring and aliphatic heterocycle) are preferred, and aliphatic heterocycles are more preferred. Although the hetero atom which comprises a heterocyclic ring is not specifically limited, An oxygen atom and a nitrogen atom are mentioned. The ring formed by L ²² may have a substituent, and examples of the substituent include the substituent T described below. Note that the aliphatic hydrocarbon ring and the aliphatic heterocyclic ring may contain an unsaturated bond.

The ring formed by L ²¹ or L ²² is preferably a 5-membered ring or a 6-membered ring, and particularly preferably a 6-membered ring. The ring formed by L ²¹ or L ²² is preferably the following formula (IIa) or (IIb).

* Represents the position of the carbon atom with the cyclopropyl group. X ¹ and X ³ each represents an oxygen atom (—O—), CR ²⁵ ₂ or NR ²⁵ . R ²⁵ has the same meaning as above. X ² is CR ²⁵ ₂ or CO. Y ¹ and Y ² are an oxygen atom, NR ²⁵ , or CR ²⁵ ₂ .

  Specific examples of the compound represented by formula (II-1) are shown below, but the present embodiment is not construed as being limited thereto. Et represents an ethyl group.

  The compound represented by the above formula (II-1) can be synthesized by a conventional method. Specifically, the procedures described in JP2013-110102A and the like can be referred to.

[Compound represented by Formula (III-1)]

・ R ^{31 to} R ³⁴
In the formula, each of R ^{31 to} R ³⁴ independently represents a hydrogen atom or a substituent, and preferably represents a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a fluorine atom, a carbonyl group-containing group, or a cyano group. Specific examples of the alkyl group, aryl group, and alkoxy group include examples of the substituent T described below. R ^{31 to} R ³⁴ may be bonded to each other or condensed to form a ring structure. R ^{31 to} R ³⁴ may further have a substituent, and examples of the substituent include examples of the substituent T described below.
R ^{31 to} R ³⁴ are each independently preferably a hydrogen atom, an alkyl group, a fluorine atom, a carbonyl group-containing group, or a cyano group, and more preferably a hydrogen atom, an alkyl group, a carbonyl group-containing group, or a cyano group.
Examples of the alkyl group include the substituent T described later, preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 7 carbon atoms, a methyl group, an ethyl group, an isopropyl group, More preferred is a butyl group or a benzyl group.
As the aryl group, an aryl group having 6 to 26 carbon atoms is preferable, and a phenyl group is particularly preferable.
As an alkoxy group, a C1-C20 alkoxy group is preferable, a C1-C10 alkoxy group is more preferable, a C1-C6 alkoxy group is further more preferable, a methoxy group, an ethoxy group, an isopropoxy group, Or a tertiary butoxy group is particularly preferable.
As the carbonyl group-containing group, an alkylcarbonyl group, an amide group, or an alkoxycarbonyl group is preferable, and a methylcarbonyl group, an ethylcarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, an isopropoxycarbonyl group, or a tertiary butoxycarbonyl group is particularly preferable. preferable.

・ L ³¹
L ³¹ represents an oxygen atom, —NR ³⁵ —, or a carbonyl group. Preferably, it is an oxygen atom or a carbonyl group. R ³⁵ has the same meaning as defined in L ³² described later. In terms of (L ³¹ ) n in the formula, the linking group formed by this is preferably a carbonyloxy group, an oxycarbonyl group, or —CO—NR ³⁵ —.

・ L ³²
L ³² represents an alkylene group (preferably having 1 to 4 carbon atoms), an oxygen atom (O), a sulfur atom (S), —SO ₂ —, or —NR ³⁵ —, and R ³⁵ is an alkyl group (preferably a carbon atom). Number 1-5) or an aryl group (preferably having 6 to 24 carbon atoms). Specific examples of the alkyl group or aryl group herein include the following examples of the substituent T. R ³⁵ may further have a substituent, and examples of the substituent include the substituent T described below. The substituents of L ³¹ to L ³² may be bonded to each other or condensed to form a ring structure. When there are a plurality of L ³¹ and L ³² , they may be different from each other.
Among them, L ³² is preferably an alkylene group having 1 to 3 carbon atoms, more preferably a methylene group.

・ N, m
n and m each independently represent 1 or 2. n + m is preferably 3 or 4, and more preferably 3. Note that a structure formed by-(L ³¹ ) n- (L ³² ) m- in the formula is not —CO—O—CO—. When n and m are 2, the plurality of structural parts defined there may be different from each other.

  The compound represented by the formula (III-1) is preferably a compound represented by the following formula (III-2) or a compound represented by (III-3).

In formula, R < ³¹ > -R < ³⁴ >, L < ³² > is synonymous with Formula (III-1).

  Specific examples of the compound represented by formula (III-1) are shown below, but the present embodiment is not construed as being limited thereto. Me represents a methyl group, and Et represents an ethyl group.

  The compound represented by the above formula (III-1) can be synthesized by a conventional method. Specifically, the procedures described in JP2013-110102A can be referred to.

  The concentration of the cyclopropane compound in the electrolyte solution for non-aqueous secondary batteries is not particularly limited, but 0.1% by mass or more based on the total mass of the electrolyte solution for non-aqueous secondary batteries (the total amount including the electrolyte). It is preferably 1% by mass or more, more preferably 2% by mass or more, particularly preferably 3% by mass or more, and most preferably 5% by mass or more. The upper limit is preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less. By blending the cyclopropane compound at the lower limit value or more, the battery characteristic maintaining effect is effectively exhibited. On the other hand, it is preferable to set it to the upper limit value or less without hindering battery performance.

  In terms of the relationship with the phosphazene compound, the content of the cyclopropane compound is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, with respect to 100 parts by mass of the phosphazene compound. Part or more is particularly preferable. The upper limit is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, particularly preferably 80 parts by mass or less, and most preferably 70 parts by mass or less.

  In addition, the combination of the phosphazene compound and the cyclopropane compound is not particularly limited, but the compound represented by the formula (A1-1) (particularly, Ra41 is a dialkylamine group in that the effect of the present invention is more excellent). And a combination of compounds represented by formula (I-1) is preferable.

Examples of the substituent T include the following.
An alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, such as methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), alkenyl group (Preferably an alkenyl group having 2 to 20 carbon atoms, such as vinyl, allyl, oleyl, etc.), alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, such as ethynyl, butadiynyl, phenylethynyl, etc.), cycloalkyl group (Preferably a cycloalkyl group having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), an aryl group (preferably an aryl group having 6 to 26 carbon atoms such as phenyl, 1-naphthyl, etc. 4-methoxyphenyl, 2-chlorophenyl, -Methylphenyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, such as 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, etc.), An alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms such as methoxy, ethoxy, isopropyloxy, benzyloxy and the like), an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms such as phenoxy, 1- Naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), alkoxycarbonyl groups (preferably C2-C20 alkoxycarbonyl groups such as ethoxycarbonyl, 2-ethylhexyloxycarbonyl, etc.), amino groups (preferably carbon A number 0-20 amino group, for example amino N, N-dimethylamino, N, N-diethylamino, N-ethylamino, anilino, etc.), sulfonamide group (preferably a sulfonamide group having 0 to 20 carbon atoms, such as N, N-dimethylsulfonamide, N- Phenylsulfonamide, etc.), acyloxy groups (preferably C1-C20 acyloxy groups such as acetyloxy, benzoyloxy, etc.), carbamoyl groups (preferably C1-C20 carbamoyl groups such as N, N- Dimethylcarbamoyl, N-phenylcarbamoyl, etc.), acylamino group (preferably an acylamino group having 1 to 20 carbon atoms, such as acetylamino, benzoylamino, etc.), cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, Iodine atoms, etc.), more preferably alkyl groups, alkeni Group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkoxycarbonyl group, amino group, acylamino group, cyano group or halogen atom, particularly preferably alkyl group, alkenyl group, heterocyclic group, alkoxy group , An alkoxycarbonyl group, an amino group, an acylamino group, or a cyano group.

  When a compound or a substituent includes an alkyl group, an alkenyl group, etc., these may be linear or branched, and may be substituted or unsubstituted. When an aryl group, a heterocyclic group, or the like is included, they may be monocyclic or condensed, and may be substituted or unsubstituted.

<Electrolyte>
The electrolyte used for the electrolyte solution for a non-aqueous secondary battery of the present invention is preferably a salt of a metal ion belonging to Group 1 or Group 2 of the periodic table. The material is appropriately selected depending on the intended use of the electrolytic solution. For example, lithium salt, potassium salt, sodium salt, calcium salt, magnesium salt and the like can be mentioned. When used in a secondary battery or the like, lithium salt is preferable from the viewpoint of output. When using the electrolyte solution for non-aqueous secondary batteries of this invention as a non-aqueous electrolyte solution for lithium secondary batteries, it is preferable to select a lithium salt as a salt of a metal ion. As a lithium salt, the lithium salt normally used for the electrolyte of the nonaqueous electrolyte solution for lithium secondary batteries is preferable, For example, what is described below is preferable.

(L-1) Inorganic lithium salts: inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ ; perhalogenates such as LiClO ₄ , LiBrO ₄ , LiIO ₄ ; inorganic chloride salts such as LiAlCl ₄ etc.

(L-2) Fluorine-containing organic lithium salt: Perfluoroalkane sulfonate such as LiCF ₃ SO ₃ ; LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , Perfluoroalkanesulfonylimide salts such as LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ); perfluoroalkanesulfonylmethide salts such as LiC (CF ₃ SO ₂ ) ₃ ; Li [PF ₅ (CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [PF ₅ (CF ₂ CF ₂ CF ₂ CF _{3 )], Li [PF 4 (} CF 2 CF 2 CF 2 CF 3) 2], Li [PF 3 (CF 2 CF 2 CF 2 CF 3) 3] fluoroalkyl fluoride such as potash Acid salts, and the like.

(L-3) Oxalatoborate salt: lithium bis (oxalato) borate, lithium difluorooxalatoborate and the like.
Among these, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiClO ₄ , Li (Rf ¹ SO ₃ ), LiN (Rf ¹ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , and LiN (Rf ¹ SO ₂ ) (Rf ² SO ₂ ) is preferred, and lithium such as LiPF ₆ , LiBF ₄ , LiN (Rf ¹ SO ₂ ) ₂ , LiN (FSO ₂ ) ₂ , and LiN (Rf ¹ SO ₂ ) (Rf ² SO ₂ ) More preferred are imide salts. Here, Rf ¹ and Rf ² each represent a perfluoroalkyl group.
In addition, the electrolyte used for electrolyte solution may be used individually by 1 type, or may combine 2 or more types arbitrarily.
The electrolyte (preferably metal ions belonging to Group 1 or Group 2 of the periodic table or metal salts thereof) in the electrolytic solution is preferably added in such an amount that a predetermined salt concentration is obtained. The salt concentration is appropriately selected depending on the purpose of use of the electrolytic solution, but generally it is preferably 10% by mass to 50% by mass, more preferably 15% by mass to 30% by mass with respect to the total mass of the electrolytic solution. It is. The molar concentration is preferably 0.5M to 1.5M. In addition, when evaluating as an ion density | concentration, what is necessary is just to calculate by salt conversion with the metal applied suitably.

<Non-aqueous solvent>
The non-aqueous solvent used in the present invention is preferably an aprotic organic solvent, and more preferably an aprotic organic solvent having 2 to 10 carbon atoms. The non-aqueous solvent is preferably a compound having an ether group, a carbonyl group, an ester group, or a carbonate group, and more preferably a cyclic carbonate, a chain carbonate, or a cyclic ester. The compound may have a substituent, and examples thereof include the above-described substituent T.

Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2 -Methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, butyric acid Methyl, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, Examples thereof include N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N′-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethyl sulfoxide, and dimethyl sulfoxide phosphoric acid. These may be used alone or in combination of two or more.
Among these, at least one member selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and γ-butyrolactone is preferable, and in particular, high viscosity (high dielectric constant) such as ethylene carbonate or propylene carbonate. The combination of a solvent (for example, relative dielectric constant ε ≧ 30) and a low viscosity solvent (for example, viscosity ≦ 1 mPa · s) such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate is more preferable. This is because the dissociation property of the electrolyte salt and the ion mobility are improved.
However, the non-aqueous solvent used in the present invention is not limited by the above examples.

<Functional additives>
The electrolyte solution for a non-aqueous secondary battery of the present invention may contain other components other than the above-described phosphazene compound, cyclopropane compound, electrolyte, and non-aqueous solvent, and contains various functional additives. It is preferable. Examples of the function manifested by this additive include improved flame retardancy, improved cycle characteristics, and improved capacity characteristics. Examples of functional additives that are preferably applied to the electrolyte of the present invention are shown below.

(Aromatic compounds)
Examples of aromatic compounds include biphenyl compounds and alkyl-substituted benzene compounds. The biphenyl compound has a partial structure in which two benzene rings are bonded by a single bond, and the benzene ring may have a substituent, and preferred substituents are alkyl groups having 1 to 4 carbon atoms (for example, Methyl, ethyl, propyl, t-butyl and the like) and aryl groups having 6 to 10 carbon atoms (for example, phenyl, naphthyl and the like).
Specific examples of the biphenyl compound include biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, 4-methylbiphenyl, 4-ethylbiphenyl, and 4-tert-butylbiphenyl.
The alkyl-substituted benzene compound is preferably a benzene compound substituted with an alkyl group having 1 to 10 carbon atoms. Specifically, ethylbenzene, isopropylbenzene, cyclohexylbenzene, t-amylbenzene, t-butylbenzene, and tetrahydrohydronaphthalene are used. Can be mentioned.

(Halogen-containing compounds)
As a halogen atom which a halogen containing compound has, a fluorine atom, a chlorine atom, or a bromine atom is preferable, and a fluorine atom is more preferable. The number of halogen atoms is preferably 1 to 6, and more preferably 1 to 3. The halogen-containing compound is preferably a carbonate compound substituted with a fluorine atom, a polyether compound having a fluorine atom, or a fluorine-substituted aromatic compound.
The halogen-substituted carbonate compound may be either linear or cyclic. From the viewpoint of ion conductivity, a cyclic carbonate compound having a high coordination property of an electrolyte salt (for example, lithium ion) is preferable, and a 5-membered cyclic carbonate compound is particularly preferable. preferable.
Preferred specific examples of the halogen-substituted carbonate compound are shown below. Among these, compounds of Bex1 to Bex4 are particularly preferable, and Bex1 is particularly preferable.

(Polymerizable compound)
Carbon as a polymerizable compound - preferably a compound having a carbon double bond, cyclic carbonate compounds having a double bond, acrylate group, methacrylate group, a cyano acrylate group, a compound having a group selected from ArufaCF ₃ acrylate groups, styryl group A compound having a double bond is preferable, and a cyclic carbonate compound having a double bond or a compound having two or more polymerizable groups in the molecule is more preferable.

  Examples of the cyclic carbonate compound having a double bond include at least one selected from the group consisting of vinylene carbonate compounds, vinyl ethylene carbonate compounds, and methylene ethylene carbonate compounds. These may be used alone or in combination of two or more. Among these, vinylene carbonate or vinyl ethylene carbonate compound is preferable, and vinylene carbonate (1,3-dioxol-2-one) or vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one) is more preferable. preferable. This is because a high effect can be obtained.

(Sulfur-containing compounds)
As the sulfur-containing compound, compounds having —SO ₂ —, —SO ₃ —, and —OS (═O) O— bonds are preferable, and cyclic sulfur-containing compounds such as propane sultone, propene sultone, and ethylene sulfite, and sulfonic acid Esters are preferred. Examples of the cyclic sulfur-containing compound include the following Eex1 to Eex12.

(Silicon-containing compound)
As the silicon-containing compound, a compound represented by the following formula (F1) or (F2) is preferable.

R ^F1 represents an alkyl group, an alkenyl group, an acyl group, an acyloxy group, or an alkoxycarbonyl group.
R ^F2 represents an alkyl group, an alkenyl group, an alkynyl group, or an alkoxy group.
A plurality of R ^F1 and R ^{F2 in} one formula may be different or the same.

(Nitrile compound)
As the nitrile compound, acetonitrile, propionitrile, isobutyronitrile, succinonitrile, malononitrile, glutaronitrile, adiponitrile, 2-methylglutonitrile, hexanetricarbonitrile, propanetetracarbonitrile and the like are preferable. Particularly preferred are succinonitrile, malononitrile, glutaronitrile, adiponitrile, 2-methylglutanonitrile, hexanetricarbonitrile, and propanetetracarbonitrile.

(Boron-containing compounds)
As the boron-containing compound, compounds represented by the following formulas (H1) to (H3) are preferable.

In the formula, R ^H1 , R ^{H4 to} R ^H11 are each independently an alkyl group, an alkoxy group, an alkylcarbonyloxy group, an aryl group, an aryloxy group, an arylcarbonyloxy group, a heteroaryl group, a heteroaryloxy group, a hetero group An arylcarbonyloxy group, an alkylamino group, an arylamino group, a cyano group, a carbamoyl group, or a halogen atom may be represented and linked together to form a ring. R ^{H2 to} R ^H3 each independently represent an alkyl group, an alkylcarbonyl group, an aryl group, an arylcarbonyl group, a heteroaryl group, a heteroarylcarbonyl group, or a boron atom, and may be connected to each other to form a ring. . Z ⁺ represents an inorganic or organic cation, and is preferably an ammonium cation, Li ⁺ , Na ⁺ , or K ⁺ . Specific examples of the boron-containing compound include the following structures, and more preferably Hex1 to Hex2.

(Imide compound)
As the imide compound, a sulfonimide compound having a perfluoro group is preferable from the viewpoint of oxidation resistance, and specifically, a perfluorosulfoimide lithium compound may be mentioned. Specific examples of the imide compound include the following structures, and Cex1 and Cex2 are more preferable.

  The electrolyte solution for a non-aqueous secondary battery of the present invention may contain at least one selected from the above, a negative electrode film forming agent, an overcharge preventing agent and the like. Although the content rate of these functional additives in the electrolyte solution for non-aqueous secondary batteries is not particularly limited, 0.001 mass for each of the total mass (including electrolyte) of electrolyte solution for non-aqueous secondary batteries. % To 10% by mass is preferable. By adding these compounds, it is possible to suppress the rupture of the battery at the time of abnormality due to overcharge, or to improve the capacity maintenance characteristic and cycle characteristic after high temperature storage.

<Method for preparing electrolytic solution>
The electrolyte solution for a non-aqueous secondary battery of the present invention is prepared by a conventional method by dissolving the above components in the non-aqueous solvent, including an example using a lithium salt as a metal ion salt.
In the present invention, “non-water” means that water is not substantially contained, and a trace amount of water may be contained as long as the effects of the invention are not hindered. In view of obtaining good characteristics, the concentration of water is preferably 200 ppm (mass basis) or less, more preferably 100 ppm or less, and further preferably 20 ppm or less. Although there is no lower limit in particular, it is practical that it is 1 ppm or more considering inevitable mixing.
Although the viscosity of the electrolyte solution for non-aqueous secondary batteries of this invention is not specifically limited, It is preferable that it is 0.1-10 mPa * s at 25 degreeC, and it is more preferable that it is 0.5-5 mPa * s.

  In the present specification, the viscosity is a value measured by the following method. 1 mL of a sample is put into a rheometer (CLS 500) and measured using a Steel Cone (both manufactured by TA Instruments) having a diameter of 4 cm / 2 °. The sample is kept warm in advance until the temperature becomes constant at the measurement start temperature, and the measurement starts thereafter. The measurement temperature is 25 ° C.

<Secondary battery>
In this invention, it is preferable to set it as the non-aqueous secondary battery containing the electrolyte solution for non-aqueous secondary batteries. As a preferred embodiment, a lithium ion secondary battery will be described with reference to FIG. 1 schematically showing the mechanism.
The lithium ion secondary battery 10 of this embodiment includes the electrolyte solution 5 for a non-aqueous secondary battery of the present invention and a positive electrode C capable of inserting and releasing lithium ions (a positive electrode current collector 1 and a positive electrode active material layer 2). And a negative electrode A (a negative electrode current collector 3 and a negative electrode active material layer 4) capable of inserting and releasing lithium ions or dissolving and depositing lithium ions. In addition to these essential members, considering the purpose for which the battery is used, the shape of the potential, etc., a separator 9 disposed between the positive electrode and the negative electrode, a current collecting terminal (not shown), an outer case, etc. (Not shown). If necessary, a protective element may be attached to at least one of the inside of the battery and the outside of the battery. By adopting such a structure, lithium ion exchanges a and b occur in the electrolytic solution 5, charging α and discharging β can be performed, and operation or storage is performed via the circuit mechanism 7 via the operation mechanism 6. It can be performed.
Hereinafter, the configuration of the lithium secondary battery which is a preferred embodiment of the present invention will be described in more detail.

(Battery shape)
The battery shape to which the lithium secondary battery of the present embodiment is applied is not particularly limited, and examples thereof include a bottomed cylindrical shape, a bottomed square shape, a thin shape, a sheet shape, and a paper shape. Any of these may be used. Further, it may be of a different shape such as a horseshoe shape or a comb shape considering the shape of the system or device to be incorporated. Among these, from the viewpoint of efficiently releasing the heat inside the battery to the outside, a rectangular shape such as a bottomed rectangular shape or a thin shape having at least one surface that is relatively flat and has a large area is preferable.

  In a battery having a bottomed cylindrical shape, since the outer surface area with respect to the power generating element to be filled becomes small, it is preferable to design so that Joule heat generated by the internal resistance at the time of charging and discharging efficiently escapes to the outside. Moreover, it is preferable to design so that the filling ratio of the substance having high thermal conductivity is increased and the temperature distribution inside is reduced. FIG. 2 is an example of a bottomed cylindrical lithium secondary battery 100. This battery is a bottomed cylindrical lithium secondary battery 100 in which a positive electrode sheet 14 and a negative electrode sheet 16 overlapped with a separator 12 are wound and accommodated in an outer can 18.

In the bottomed square shape, the ratio of the area S of the largest surface (the product of the width and height of the outer dimensions excluding the terminal portion, unit cm ² ) to the thickness T (unit cm) of the battery outer shape The 2S / T value is preferably 100 or more, and more preferably 200 or more. By increasing the maximum surface, it is possible to improve characteristics such as cycle performance and high-temperature storage even for high-power and large-capacity batteries, and increase the heat dissipation efficiency during abnormal heat generation. Can be prevented from becoming a dangerous state.

(Members constituting the battery)
The lithium secondary battery according to the present embodiment includes the basic member of the electrolyte 5, the electrode mixture of the positive electrode C and the negative electrode A, and the separator 9, based on FIG. 1. Hereinafter, each of these members will be described.

(Electrode mixture)
The electrode mixture is obtained by applying a dispersion of an active material and a conductive agent, a binder, a filler, etc. on a current collector (electrode substrate). In a lithium battery, the active material is a positive electrode active material. It is preferable to use a negative electrode mixture in which the positive electrode mixture and the active material are a negative electrode active material. Next, each component in the dispersion (electrode composition) constituting the electrode mixture will be described.

-Positive electrode active material It is preferable to use a transition metal oxide for the positive electrode active material, and in particular, it has a transition element M ^a (one or more elements selected from Co, Ni, Fe, Mn, Cu, V). It is preferable. Further, mixed element M ^b (elements of the first (Ia) group of the metal periodic table other than lithium, elements of the second (IIa) group, Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si , P, B, etc.) may be mixed. Examples of the transition metal oxide include specific transition metal oxides including those represented by any of the following formulas (MA) to (MC), or other transition metal oxides such as V ₂ O ₅ and MnO _2. Is mentioned. As the positive electrode active material, a particulate positive electrode active material may be used. Specifically, a transition metal oxide capable of reversibly inserting and releasing lithium ions can be used, but a specific transition metal oxide is preferably used.

The transition metal oxides, oxides containing a transition element M ^a is preferably exemplified. At this time, a mixed element M ^b (preferably Al) or the like may be mixed. The mixing amount is preferably 0 to 30 mol% with respect to the amount of the transition metal. That the molar ratio of li / ^{M a} is synthesized by mixing so that 0.3 to 2.2 is more preferable.

[Transition metal oxide represented by formula (MA) (layered rock salt structure)]
Among them, lithium-containing transition metal oxides are preferably those represented by the following formula.
Li _a M ¹ O _b (MA)

In the formula, M ¹ has the same meaning as M ^a . a represents 0 to 1.2, preferably 0.1 to 1.15, and more preferably 0.6 to 1.1. b represents 1-3 and is preferably 2. A part of M ¹ may be substituted with the mixed element M ^b . The transition metal oxide represented by the formula (MA) typically has a layered rock salt structure.

The transition metal oxide is more preferably one represented by the following formulas.
_{(MA-1) Li g CoO} k
_{(MA-2) Li g NiO} k
_{(MA-3) Li g MnO} k
_{(MA-4) Li g Co} j Ni 1-j O k
_{(MA-5) Li g Ni} j Mn 1-j O k
_{(MA-6) Li g Co} j Ni i Al 1-j-i O k
_{(MA-7) Li g Co} j Ni i Mn 1-j-i O k

Here, g is synonymous with a. j represents 0.1 to 0.9. i represents 0 to 1; However, 1-j-i is 0 or more. k is synonymous with b. Specific examples of the transition metal compound include LiCoO ₂ (lithium cobaltate [LCO]), LiNi ₂ O ₂ (lithium nickelate), LiNi _0.85 Co _0.01 Al _0.05 O ₂ (nickel cobalt aluminum acid Lithium [NCA]), LiNi _0.33 Co _0.33 Mn _0.33 O ₂ (lithium nickel manganese cobaltate [NMC]), LiNi _0.5 Mn _0.5 O ₂ (lithium manganese nickelate).

The transition metal oxide represented by the formula (MA) partially overlaps, but when represented by changing the notation, those represented by the following are also preferable examples.
_{(I) Li g Ni x Mn} y Co z O 2 (x> 0.2, y> 0.2, z ≧ 0, x + y + z = 1)
Representative:
_{Li g Ni 1/3 Mn 1/3 Co 1/3} O 2
Li _g Ni _1/2 Mn _1/2 O _{2
(Ii) Li g Ni x Co} y Al z O 2 (x> 0.7, y>0.1,0.1> z ≧ 0.05, x + y + z = 1)
Representative:
_{Li g Ni 0.8 Co 0.15 Al 0.05} O 2

[Transition metal oxide represented by formula (MB) (spinel structure)]
As the lithium-containing transition metal oxide, those represented by the following formula (MB) are particularly preferable.
Li _c M ² ₂ O _d (MB)

In the formula, M ² has the same meaning as M ^a . c represents 0 to 2, preferably 0.1 to 1.15, and more preferably 0.6 to 1.5. d represents 3 to 5 and is preferably 4.

The transition metal oxide represented by the formula (MB) is more preferably one represented by the following formulas.
_{(MB-1) Li m Mn} 2 O n
_{(MB-2) Li m Mn} p Al 2-p O n
_{(MB-3) Li m Mn} p Ni 2-p O n

m is synonymous with c. n is synonymous with d. p represents 0-2. Specific examples of the transition metal compound are LiMn ₂ O ₄ and LiMn _1.5 Ni _0.5 O ₄ .

Preferred examples of the transition metal oxide represented by the formula (MB) include those represented by the following.
(A) LiCoMnO ₄
(B) Li ₂ FeMn ₃ O ₈
(C) Li ₂ CuMn ₃ O ₈
(D) Li ₂ CrMn ₃ O ₈
(E) Li ₂ NiMn ₃ O ₈
Of these, an electrode containing Ni is more preferable from the viewpoint of high capacity and high output.

[Transition metal oxide represented by formula (MC)]
As the lithium-containing transition metal oxide, it is also preferable to use a lithium-containing transition metal phosphor oxide, and among them, one represented by the following formula (MC) is more preferable.
Li _e M ³ (PO ₄ ) _f ... (MC)

  In the formula, e represents 0 to 2, preferably 0.1 to 1.15, and more preferably 0.5 to 1.5. f represents 1 to 5 and is preferably 0.5 to 2.

M ³ represents one or more elements selected from V, Ti, Cr, Mn, Fe, Co, Ni, and Cu. M ³ represents, in addition to the mixing element ^{M b} above, Ti, Cr, Zn, Zr, may be substituted by other metals such as Nb. Specific examples include, for example, olivine-type iron phosphates such as LiFePO ₄ and Li ₃ Fe ₂ (PO ₄ ) ₃ , iron pyrophosphates such as LiFeP ₂ O ₇ , cobalt phosphates such as LiCoPO ₄ , and Li _3. Monoclinic Nasicon type vanadium phosphate salts such as V ₂ (PO ₄ ) ₃ (lithium vanadium phosphate) can be mentioned.
The a, c, g, m, and e values representing the composition of Li are values that change due to charge and discharge, and are typically evaluated as values in a stable state when Li is contained. In the formulas (a) to (e), the composition of Li is shown as a specific value, and this also changes depending on the operation of the battery.
In particular, in the present invention, a positive electrode active material containing Ni and / or Mn atoms is preferably used, and a positive electrode active material containing both Ni and Mn atoms is more preferably used. Specific examples of particularly preferable positive electrode active materials include the following.
LiNi _0.33 Co _0.33 Mn _0.33 O ₂
LiNi _0.6 Co _0.2 Mn _0.2 O ₂
LiNi _0.5 Co _0.3 Mn _0.2 O ₂
LiNi _0.5 Mn _0.5 O ₂
LiNi _0.5 Mn _1.5 O ₄
Since these can be used at a high potential, the battery capacity can be increased, and even when used at a high potential, the capacity retention rate is high, which is particularly preferable.

In the present invention, the positive electrode active material is preferably a material that can maintain normal use at a positive electrode potential (Li / Li ⁺ standard) of 3.5 V or higher, more preferably 3.8 V or higher, and more preferably 4 V or higher. More preferably, it is more preferably 4.25V or more, and most preferably 4.3V or more. Although there is no upper limit in particular, it is practical that it is 5V or less. By setting it as the above range, cycle characteristics and high rate discharge characteristics can be improved.
Here, being able to maintain normal use means that even when charging is performed at that voltage, the electrode material does not deteriorate and cannot be used, and this potential is also referred to as a normal usable potential.
The positive electrode potential during charging / discharging (Li / Li ⁺ reference) is (positive electrode potential) = (negative electrode potential) + (battery voltage). When lithium titanate is used as the negative electrode, the negative electrode potential is 1.55V. When graphite is used as the negative electrode, the negative electrode potential is set to 0.1V. The battery voltage is observed during charging and the positive electrode potential is calculated.

  The electrolyte solution for a non-aqueous secondary battery of the present invention is particularly preferably used in combination with a high potential positive electrode. When a positive electrode with a high potential is used, the cycle characteristics tend to be greatly deteriorated. However, according to a preferred embodiment of the present invention, the electrolyte for nonaqueous secondary batteries maintains good performance with this decrease suppressed. can do.

In the non-aqueous secondary battery of the present invention, the average particle size of the positive electrode active material used is not particularly limited, but is preferably 0.1 μm to 50 μm. No particular limitation is imposed on the specific surface area, preferably from 0.01m ² / g~50m ² / g by the BET method. Further, the pH of the supernatant when 5 g of the positive electrode active material is dissolved in 100 ml of distilled water is preferably 7 or more and 12 or less.

  To make the positive electrode active material have a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a vibration ball mill, a vibration mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill, a sieve, or the like is used. The positive electrode active material obtained by the firing method may be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.

  Although the compounding quantity of a positive electrode active material is not specifically limited, In the dispersion (mixture) for comprising an active material layer, it is preferable that it is 60-98 mass% in 100 mass% of solid components, and is 70-95 mass. % Is more preferable.

・ Negative electrode active material As the negative electrode active material, those capable of reversibly inserting and releasing lithium ions are preferable, and there is no particular limitation. Carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium Examples thereof include a single alloy and a lithium alloy such as a lithium aluminum alloy, and a metal capable of forming an alloy with lithium such as Sn or Si.
These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Of these, carbonaceous materials or lithium composite oxides are preferably used from the viewpoint of reliability.
Moreover, as a metal complex oxide, what can occlude and discharge | release lithium is preferable, and it is preferable from a viewpoint of a high current density charge / discharge characteristic that it contains titanium and / or lithium as a structural component.

  The carbonaceous material used as the negative electrode active material is a material substantially made of carbon. Examples thereof include carbonaceous materials obtained by baking various synthetic resins such as artificial graphite such as petroleum pitch, natural graphite and vapor-grown graphite, and PAN (Polyacrylonitrile) -based resin and furfuryl alcohol resin. Furthermore, various carbon fibers such as PAN-based carbon fiber, cellulose-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, dehydrated PVA-based carbon fiber, lignin carbon fiber, glassy carbon fiber, activated carbon fiber, mesophase micro Examples thereof include spheres, graphite whiskers, and flat graphite.

  These carbonaceous materials can be divided into non-graphitizable carbon materials and graphite-based carbon materials depending on the degree of graphitization. Further, the carbonaceous material preferably has the surface spacing, density, and crystallite size described in JP-A-62-222066, JP-A-2-6856, and 3-45473. The carbonaceous material does not need to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-90844, graphite having a coating layer described in JP-A-6-4516, or the like is used. You can also.

  It is preferable that the metal oxide and metal composite oxide which are negative electrode active materials used in the non-aqueous secondary battery of the present invention contain at least one of them. As the metal oxide and the metal composite oxide, an amorphous oxide is particularly preferable, and chalcogenite which is a reaction product of a metal element and an element of Group 16 of the periodic table is also preferably used. The term “amorphous” as used herein means an X-ray diffraction method using CuKα rays, which has a broad scattering band having an apex in the region of 20 ° to 40 ° in terms of 2θ values, and is a crystalline diffraction line. You may have. The strongest intensity of crystalline diffraction lines seen from 2 ° to 40 ° to 70 ° is 100 times the diffraction line intensity at the peak of the broad scattering band seen from 2 ° to 20 °. It is preferable that it is 5 times or less, and it is particularly preferable not to have a crystalline diffraction line.

Among the group of compounds consisting of amorphous oxides and chalcogenides, amorphous metal oxides and chalcogenides are more preferable, and elements in groups 13 (IIIB) to 15 (VB) of the periodic table, Al , Ga, Si, Sn, Ge, Pb, Sb, Bi alone or in combination of two or more thereof, and chalcogenide are particularly preferable. Specific examples of preferable amorphous oxides and chalcogenides include, for example, Ga ₂ O ₃ , SiO, GeO, SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₂ O ₄ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ O ₄ , SnSiO ₃ , GeS, SnS, SnS ₂ , PbS, PbS ₂ , Sb ₂ S ₃ , Sb ₂ S ₅ , such as SnSiS ₃ may preferably be mentioned. Moreover, these may be a complex oxide with lithium oxide, for example, Li ₂ SnO ₂ .

  In the nonaqueous secondary battery of the present invention, the average particle size of the negative electrode active material used is preferably 0.1 μm to 60 μm. To obtain a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill or a sieve is preferably used. When pulverizing, wet pulverization in the presence of water or an organic solvent such as methanol can be performed as necessary. In order to obtain a desired particle size, classification is preferably performed. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as necessary. Classification can be used both dry and wet.

  The chemical formula of the compound obtained by the firing method can be calculated from the mass difference between the powders before and after firing as an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method.

  In the present invention, the negative electrode active material that can be used in combination with the amorphous oxide negative electrode active material centering on Sn, Si, and Ge includes a carbon material capable of inserting and extracting lithium ions or lithium metal, lithium, Preferred examples include lithium alloys and metals that can be alloyed with lithium.

The electrolyte for a non-aqueous secondary battery of the present invention is preferably combined with a high potential negative electrode (preferably lithium / titanium oxide, potential 1.55 V vs. Li metal) and a low potential negative electrode (preferably a carbon material, silicon). Excellent characteristics are exhibited in any combination of the contained material and the potential of about 0.1 V vs. Li metal. Further, metal or metal oxide negative electrodes (preferably Si, Si oxide, Si / Si oxide, Sn, Sn oxide, SnB _x P _y O _z , Cu, which can be alloyed with lithium, which are being developed for higher capacity) / Sn and a plurality of these composites), and a battery using a composite of these metals or metal oxides and a carbon material as a negative electrode.
In the present invention, it is particularly preferable to use a negative electrode active material containing at least one selected from carbon, Si, titanium, and tin.

-Conductive material The conductive material is preferably an electron conductive material that does not cause a chemical change in the constructed non-aqueous secondary battery, and a known conductive material can be arbitrarily used. Usually, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber and metal powder (copper, nickel, aluminum, silver (Japanese Patent Laid-Open No. Sho 63- Etc.), etc.), metal fibers or polyphenylene derivatives (described in JP-A-59-20971) can be contained as one kind or a mixture thereof. Among these, the combined use of graphite and acetylene black is particularly preferable. As addition amount of a electrically conductive agent, 11-50 mass% is preferable and 2-30 mass% is more preferable. In the case of carbon or graphite, 2 to 15% by mass is particularly preferable.

-Binders Examples of binders include polysaccharides, thermoplastic resins and rubber-elastic polymers, among which starch, carboxymethylcellulose, cellulose, diacetylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropyl, and the like. Water-soluble cellulose, sodium alginate, polyacrylic acid, sodium polyacrylate, polyvinyl phenol, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylonitrile, polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer, etc. Polymer, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, (Meta) such as vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate (Meth) acrylic ester copolymer containing acrylic ester, (meth) acrylic ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer, Acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluororubber, polyethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate Polyurethane resins, polyester resins, phenolic resins, emulsion (latex) or suspension such as an epoxy resin is preferable, polyacrylate latex, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride is more preferable.

  A binder can be used individually by 1 type or in mixture of 2 or more types. If the amount of the binder added is small, the holding power and cohesive strength of the electrode mixture are weakened. If the amount is too large, the electrode volume increases and the capacity per electrode unit volume or unit mass decreases. For this reason, the addition amount of the binder is preferably 1 to 30% by mass, and more preferably 2 to 10% by mass.

-Filler The electrode compound material may contain the filler. The material forming the filler is preferably a fibrous material that does not cause a chemical change in the non-aqueous secondary battery of the present invention. Usually, fibrous fillers made of materials such as olefin polymers such as polypropylene and polyethylene, glass, and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 mass% is preferable in a dispersion.

-Current collector As the positive / negative current collector, an electron conductor that does not cause a chemical change in the nonaqueous secondary battery of the present invention is used. As the positive electrode current collector, in addition to aluminum, stainless steel, nickel, titanium, etc., a surface of aluminum or stainless steel treated with carbon, nickel, titanium, or silver is preferable, and among them, aluminum, aluminum Alloys are more preferred.

  As the negative electrode current collector, aluminum, copper, stainless steel, nickel, and titanium are preferable, and aluminum, copper, and a copper alloy are more preferable.

As the shape of the current collector, a film sheet is usually used, but a net, a punched one, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like can also be used. Although it does not specifically limit as thickness of a collector, 1 micrometer-500 micrometers are preferable. Moreover, it is also preferable that the current collector surface is roughened by surface treatment.
An electrode mixture of the lithium secondary battery is formed by a member appropriately selected from these materials.

(Separator)
The separator used in the non-aqueous secondary battery of the present invention is made of a material that mechanically insulates the positive electrode and the negative electrode, has ion permeability, and has oxidation / reduction resistance at the contact surface between the positive electrode and the negative electrode. Preferably it is. As such a material, a porous polymer material, an inorganic material, an organic-inorganic hybrid material, glass fiber, or the like is used. These separators preferably have a shutdown function for ensuring reliability, that is, a function of closing a gap at 80 ° C. or higher to increase resistance and blocking current, and a closing temperature is 90 ° C. or higher and 180 ° C. or lower. It is preferable.

  The shape of the hole of the separator is usually a circle or an ellipse, and the size is 0.05 μm to 30 μm, preferably 0.1 μm to 20 μm. Furthermore, it may be a rod-like or irregular-shaped hole as in the case of making by a stretching method or a phase separation method. The ratio of these gaps, that is, the porosity, is 20% to 90%, preferably 35% to 80%.

  As the polymer material, a single material such as a cellulose nonwoven fabric, polyethylene, or polypropylene may be used, or two or more composite materials may be used. What laminated | stacked the 2 or more types of microporous film which changed the hole diameter, the porosity, the obstruction | occlusion temperature of a hole, etc. is preferable.

  As the inorganic material, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used, and those having a particle shape or fiber shape are used. As the form, a thin film shape such as a non-woven fabric, a woven fabric, or a microporous film is used. In the thin film shape, those having a pore diameter of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm are preferably used. In addition to the independent thin film shape, a separator formed by forming a composite porous layer containing inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can also be used. For example, alumina particles having a 90% particle diameter of less than 1 μm are formed on both surfaces of the positive electrode as a porous layer using a fluororesin binder.

<Production of non-aqueous secondary battery>
As described above, the shape of the nonaqueous secondary battery of the present invention can be applied to any shape such as a sheet shape, a square shape, and a cylinder shape. The positive electrode active material and the composite material of the negative electrode active material are mainly used after being applied (coated), dried and compressed on the current collector.

Hereinafter, with reference to FIG. 2, a configuration and a manufacturing method thereof will be described using the bottomed cylindrical lithium secondary battery 100 as an example.
In a battery having a bottomed cylindrical shape, since the outer surface area with respect to the power generating element to be filled becomes small, it is preferable to design so that Joule heat generated by the internal resistance at the time of charging and discharging efficiently escapes to the outside. Moreover, it is preferable to design so that the filling ratio of the substance having high thermal conductivity is increased and the temperature distribution inside is reduced. FIG. 2 shows an example of a bottomed cylindrical lithium secondary battery 100. This battery is a bottomed cylindrical lithium secondary battery 100 in which a positive electrode sheet 14 and a negative electrode sheet 16 overlapped with a separator 12 are wound and accommodated in an outer can 18. In addition, in the figure, 20 is an insulating plate, 22 is a sealing plate, 24 is a positive electrode current collector, 26 is a gasket, 28 is a pressure sensitive valve body, and 30 is a current interruption element. In addition, although the illustration in the enlarged circle has changed hatching in consideration of visibility, each member corresponds to the whole drawing by reference numerals.

  First, a negative electrode active material is mixed with a binder or filler that is optionally used in an organic solvent to prepare a slurry-like or paste-like negative electrode mixture. The obtained negative electrode mixture is uniformly applied over the entire surface of both surfaces of the metal core as a current collector, and then the organic solvent is removed to form a negative electrode mixture layer. Further, the laminate of the current collector and the negative electrode composite material layer is rolled with a roll press or the like to prepare a predetermined thickness to obtain a negative electrode sheet (electrode sheet). At this time, the coating method of each agent, the drying of the coated material, and the method of forming the positive and negative electrodes may be in accordance with conventional methods.

  In the present embodiment, a cylindrical battery has been described as an example. However, the present invention is not limited to this, and for example, after the produced positive and negative electrode sheets are overlapped via a separator, the sheet is used as it is. After processing into a battery or folding it and inserting it into a square can, electrically connecting the can and the sheet, injecting electrolyte, sealing the opening with a sealing plate and square A battery may be formed.

  In any embodiment, a safety valve can be used as a sealing plate for sealing the opening. In addition to the safety valve, the sealing member may be provided with various conventionally known safety elements. For example, a fuse, a bimetal, a PTC (Positive Temperature Coefficient) element, or the like is preferably used as the overcurrent prevention element.

  In addition to the safety valve, as a countermeasure against the increase in internal pressure of the battery can, a method of cutting the battery can, a method of cracking the gasket, a method of cracking the sealing plate, or a method of cutting the lead plate can be used. Further, the charger may be provided with a protection circuit incorporating measures against overcharge and overdischarge, or may be connected independently.

  For the can and lead plate, a metal or alloy having electrical conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum, or alloys thereof are preferably used.

  As a welding method for the cap, can, sheet, and lead plate, a known method (eg, direct current or alternating current electric welding, laser welding, ultrasonic welding) can be used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.

<Applications of non-aqueous secondary batteries>
Secondary batteries called lithium batteries are secondary batteries that use the insertion and extraction of lithium for charge / discharge reactions (lithium ion secondary batteries), and secondary batteries that use precipitation and dissolution of lithium (lithium metal secondary batteries). ). In the present invention, application as a lithium ion secondary battery is preferable.
Since the nonaqueous secondary battery of the present invention can produce a secondary battery with good cycle performance, it is applied to various applications. Although there is no particular limitation on the application mode, for example, when installed in an electronic device, a notebook computer, a pen input personal computer, a mobile personal computer, an electronic book player, a mobile phone, a cordless phone, a pager, a handy terminal, a mobile fax machine, a mobile phone Copy, portable printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, minidisc, electric shaver, transceiver, electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, memory card, etc. It is done. Other consumer products include automobiles, electric vehicles, motors, lighting equipment, toys, game equipment, road conditioners, watches, strobes, cameras, medical equipment (such as pacemakers, hearing aids, and shoulder grinders). Furthermore, it can be used for various military purposes and space. Moreover, it can also combine with a solar cell.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not construed as being limited thereto.

<Example 1>
<Preparation of electrolyte>
1M LiPF ₆ ethylene carbonate / ethyl methyl carbonate = 1/2 To the electrolyte, add 15% by mass of phosphazene compound A-108 and cyclopropane compound SI-01 in amounts shown in Table 1, and further add vinylene carbonate. An electrolyte solution for each test was prepared by adding 1% by mass with respect to the total electrolyte solution. All the prepared electrolyte solutions had a viscosity at 25 ° C. of 5 mPa · s or less, and the water content of the electrolyte solution measured by the Karl Fischer method (JIS K0113) was 20 ppm or less.
The phosphazene compound A-108 and the cyclopropane compound SI-01 correspond to the compounds exemplified above.

<Evaluation of flame retardancy of electrolyte>
The flame retardancy of the prepared electrolyte was evaluated as follows at 25 ° C. in the air.
The evaluation was carried out under the following test conditions with reference to the UL-94HB horizontal combustion test. A glass filter paper (ADVANTEC GA-100) having a width of 13 mm and a length of 110 mm was cut out, and 1.5 ml of the prepared electrolyte was evenly dropped onto the glass filter paper. After the electrolyte solution was sufficiently infiltrated into the glass filter paper, the excess electrolyte solution was wiped off and suspended so that the minor axis was vertical. The flame of the butane gas burner adjusted to a total flame length of 2 cm ignites for 3 seconds at the position where it touches the tip of the glass filter paper. When the time to reach was evaluated as follows, ignition was not seen and it was nonflammable (Evaluation 5).
5 ... Ignition was not seen and it was nonflammable.
4 ... I ignited but extinguished immediately.
3 ... ignited but extinguished before the flame reached from the ignition point to the other end.
2 ... Flame reaches from the ignition point to the other end for 10 seconds or more, and the combustion suppression effect is seen, but it does not lead to non-flammability and extinction Level 1 ... Flame reaches from the ignition point to the other end The burning time is less than 10 seconds and there is no combustion suppression effect.

<Production of battery (1)>
The positive electrode is made of active material: LiNi _1/3 Mn _1/3 Co _1/3 O ₂ (NMC) 94% by mass, conductive assistant: carbon black 3% by mass, binder: PVDF (PolyVinylidene DiFluoride) 3% by mass, The negative electrode was made with active material: 97% by mass of graphite, binder: 2% by mass of styrene butadiene rubber (SBR), and thickener: 1% by mass of CMC (carboxymethylcellulose). As the separator, a polypropylene porous film having a thickness of 24 μm was used. Using the positive electrode, the negative electrode, and the separator described above, a 2032 type coin battery (1) was manufactured using the electrolytic solution shown in Table 1.

<Battery initialization>
Using a 2032 type coin battery (1), 0.2C constant current charging was performed in a thermostat at 30 ° C. until the battery voltage reached 4.35V. Next, 0.2 C constant current discharge was performed until the battery voltage became 2.75 V in a thermostat at 30 ° C. This operation was repeated three times to initialize the 2032 type coin battery (1). Next, the following items were evaluated using the obtained 2032 type coin battery (1). The results are shown in Table 1.
Here, 1C represents a current value for discharging or charging the battery capacity in one hour, 0.2C represents 0.2 times, 0.5C represents 0.5 times, and 2C represents twice the current value. .

(First discharge capacity)
Using a 2032 type coin battery (1), a constant current of 0.7 C was charged in a constant temperature bath at 45 ° C. until the battery voltage reached 4.35 V, and then the current value at a constant voltage of 4.35 V was 0. The battery was charged until reaching 03C. However, the upper limit of the time was 2 hours. This battery was subjected to a 0.5 C constant current discharge in a 45 ° C. thermostat until the battery voltage reached 2.75 V, and the initial discharge capacity (I) was measured.

(High temperature cycle test)
The 2032 type coin battery (1) whose initial discharge capacity was measured was charged at a constant current of 0.7 C in a constant temperature bath at 45 ° C. until the battery voltage reached 4.35 V, and then the current value at a constant voltage of 4.35 V. The battery was charged until 0.03C was reached. However, the upper limit of the time was 2 hours. This battery was repeatedly charged and discharged 300 times in a constant temperature bath at 45 ° C. for 0.5C constant current discharge until the battery voltage reached 2.75V.

(Discharge capacity after cycle test)
The 2032 type coin battery (1) after the high-temperature cycle test was charged and discharged under the same conditions as the initial discharge capacity measurement, and the discharge capacity (II) after the cycle test was measured.

From the obtained results, the discharge capacity retention rate after the cycle test was calculated by the following formula.
Discharge capacity maintenance ratio after cycle test = discharge capacity (II) / initial discharge capacity (I)
In addition, the obtained discharge capacity maintenance rate was evaluated by taking the discharge capacity maintenance rate after the cycle test of test No101 to which 0.5% by mass of cyclopropane compound SI-01 was added as 100, and evaluating the relative value as a capacity ratio. It is shown in 1.

<Comparative Example 1>
The same operation as in Example 1 was carried out except that phosphazene compound A-108 was not added. All the prepared electrolyte solutions had a viscosity at 25 ° C. of 5 mPa · s or less, and the water content of the electrolyte solution measured by the Karl Fischer method (JIS K0113) was 20 ppm or less. In the flame retardancy evaluation of the electrolyte, the time for the flame to reach from the ignition point to the other end was less than 5 seconds (Evaluation 1).

From the comparison between Example 1 and Comparative Example 1, as shown in Test Nos. 102 to 107, by adding 1 to 15% by mass of the cyclopropane compound, a high discharge capacity retention rate can be achieved even under severe use conditions. As shown in ˜106, it can be seen that the addition of 5 to 10% by mass exhibits a higher effect.
In terms of the relationship between the phosphazene compound and the cyclopropane compound, as shown in Test Nos. 103 to 107, the cyclopropane compound is added in an amount of 10 to 100 parts by mass with respect to 100 parts by mass of the phosphazene compound. It can be seen that a high discharge capacity retention rate can be achieved and, as shown in Test Nos. 104 to 106, a higher effect is exhibited by addition of 30 to 70 parts by mass.

<Example 2>
The same operation as in Example 1 was carried out except that phosphazene compound A-120 was added in an amount of 10% by mass and cyclopropane compound SIII-06 was added in amounts shown in Table 2. All the prepared electrolyte solutions had a viscosity at 25 ° C. of 5 mPa · s or less, and the water content of the electrolyte solution measured by the Karl Fischer method (JIS K0113) was 20 ppm or less. The results are shown in Table 2.
The phosphazene compound A-120 and the cyclopropane compound SIII-06 correspond to the compounds exemplified above, respectively.

<Comparative example 2>
The same operation as in Example 2 was performed, except that phosphazene compound A-120 was not added. All the prepared electrolyte solutions had a viscosity at 25 ° C. of 5 mPa · s or less, and the water content of the electrolyte solution measured by the Karl Fischer method (JIS K0113) was 20 ppm or less. The results are shown in Table 2.

From the comparison between Example 2 and Comparative Example 2, as shown in Test Nos. 202 to 206, by adding 1 to 10% by mass of the cyclopropane compound, a high discharge capacity maintenance rate can be achieved even under severe use conditions. As shown in ˜205, it can be seen that the addition of 5 to 7.5% by mass exhibits a higher effect.
In terms of the relationship between the phosphazene compound and the cyclopropane compound, as shown in Test Nos. 202 to 206, 10 to 100% by mass of the cyclopropane compound with respect to 100 parts by mass of the phosphazene compound can be used under severe conditions. It can be seen that a high discharge capacity retention rate can be achieved, and as shown in Test Nos. 203 to 205, the addition of 30 to 75 parts by mass exhibits a higher effect.

<Example 3 and Comparative Example 3>
(Preparation of electrolyte)
1M LiPF ₆ Ethylene carbonate / ethyl methyl carbonate = 1/2 To the electrolyte solution, add the phosphazene compound (A) and the cyclopropane compound (B) to the amounts shown in Table 3 (content relative to the total mass of the electrolyte solution). Furthermore, vinylene carbonate was added at 1% by mass with respect to the total electrolyte solution, and succinonitrile was added at 1% by mass with respect to the total electrolyte solution to prepare electrolyte solutions for each test. All the prepared electrolyte solutions had a viscosity at 25 ° C. of 5 mPa · s or less, and the water content of the electrolyte solution measured by the Karl Fischer method (JIS K0113) was 20 ppm or less.
In Comparative Example 3, the cyclopropane compound (B) was not used.

<Flame retardance>
Using the prepared electrolytic solution, the same evaluation as in <Evaluation of Flame Retardancy of Electrolytic Solution> performed in Example 1 was performed. The results are shown in Table 1.
In the electrolyte solution to which the additive (phosphazene compound (A)) was not added, the time required for the flame to reach from the ignition point to the other end was less than 5 seconds.

<Production of battery>
Using the prepared electrolytic solution, the discharge capacity retention rate after the cycle test was calculated according to the same procedure as in Example 1. In addition, the obtained discharge capacity maintenance factor (discharge capacity (II) / discharge capacity (I)) was evaluated as follows. The larger the value, the higher the capacity is maintained even under severe test conditions. The results are shown in Table 3.
A: 0.7 or more B: 0.65 or more and less than 0.7 C: 0.6 or more and less than 0.65 D: 0.55 or more and less than 0.6 E: 0.5 or more and less than 0.55 F: 0. Less than 5

As shown in Table 3, it was confirmed that the desired effect was obtained when the electrolytic solution of the present invention was used. In particular, when a compound represented by the formula (A1-1) in which Ra ⁴¹ is a dialkylamino group and a compound represented by the formula (I-1) are used in combination, a more excellent effect was obtained. .

<Example 4 and Comparative Example 4>
Example 3 except that the electrolytic solution was 1.1M LiBF ₄ ethylene carbonate / dimethyl carbonate = 2/3, succinonitrile was 1,3-propane sultone, and the positive electrode active material was lithium cobaltate (LiCoO ₂ ). The same operation was performed. The results are shown in Table 4.

As shown in Table 4, it was confirmed that the desired effect was obtained when the electrolytic solution of the present invention was used. In particular, when a compound represented by the formula (A1-1) in which Ra ⁴¹ is a dialkylamino group and a compound represented by the formula (III-1) are used in combination, an excellent effect was obtained.
According to the electrolyte solution for a non-aqueous secondary battery of the present invention, it has been found that a high discharge capacity retention rate can be achieved even under severe use conditions while realizing high flame retardancy.

C positive electrode (positive electrode composite)
1 Positive electrode conductive material (current collector)
2 Positive electrode active material layer A Negative electrode (negative electrode composite)
3 Negative electrode conductive material (current collector)
4 Negative electrode active material layer 5 Electrolyte for non-aqueous secondary battery 6 Operating means 7 Wiring 9 Separator 10 Lithium ion secondary battery 12 Separator 14 Positive electrode sheet 16 Negative electrode sheet 18 Exterior can 20 also serving as negative electrode Electricity 26 Gasket 28 Pressure-sensitive valve body 30 Current interrupting element 100 Bottomed cylindrical lithium secondary battery

Claims (20)

At least one phosphazene compound selected from the group consisting of a compound represented by formula (A1) and a compound represented by formula (A2);
At least one cyclopropane compound selected from the group consisting of a compound represented by formula (I-1), a compound represented by formula (II-1), and a compound represented by formula (III-1) When,
Electrolyte,
An electrolyte for a non-aqueous secondary battery containing a non-aqueous solvent.

In the formula, Ra ^{11 to} Ra ¹⁶ and Ra ^{21 to} Ra ²⁸ each independently represent a monovalent substituent. In adjacent Ra ¹¹ to Ra ¹⁶ and Ra ^{21 to} Ra ²⁸ , the substituents may form a ring.

In formula (I-1), R ^{11 to} R ¹⁴ each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a fluorine atom, a carbonyl group-containing group, or a cyano group. R ¹⁵ represents a C 1-7 substituent that may contain an oxygen atom, a nitrogen atom, or a sulfur atom. L ¹¹ represents an alkylene group or a carbonyl group. X represents an electron-attracting group showing a value of 0 or more in the Hammett's rule σp value.
In formula (II-1), R ^{21 to} R ²⁴ each independently represent a hydrogen atom or a substituent. L ²¹ represents an atomic group that forms a ring structure with the carbon atoms of the carbonyl group and the cyclopropyl group in the formula.
In formula (III-1), R ^{31 to} R ³⁴ each independently represent a hydrogen atom or a substituent. L ³¹ represents an oxygen atom, —NR ³⁵ —, or a carbonyl group. L ³² represents an alkylene group, an oxygen atom, a sulfur atom, —SO ₂ —, or —NR ³⁵ —. R ³⁵ represents an alkyl group or an aryl group. n and m each independently represent 1 or 2.   2. The electrolyte solution for a non-aqueous secondary battery according to claim 1, wherein the content of the cyclopropane compound is 10 parts by mass or more and 120 parts by mass or less with respect to 100 parts by mass of the phosphazene compound.   The electrolyte solution for nonaqueous secondary batteries according to claim 1 or 2, wherein X in the formula (I-1) is a cyano group, an alkoxycarbonyl group, or a carbamoyl group. The electrolyte solution for non-aqueous secondary batteries of any one of Claims 1-3 whose R < ¹¹ > -R < ¹⁴ > is a hydrogen atom in the said formula (I-1).   The electrolyte solution for non-aqueous secondary batteries according to any one of claims 1 to 4, wherein X in the formula (I-1) is a cyano group or an alkoxycarbonyl group. ^-L 11 ^{-R 15} is a -COOR ^16, a non-aqueous liquid electrolyte for a secondary battery according to any one of claims 1 to 5 wherein the formula (I-1).
R ¹⁶ represents a carbonyl group, an ether group, or an alkyl group having 1 to 6 carbon atoms that may intervene —NR ¹⁷ —. R ¹⁷ represents a hydrogen atom or an alkyl group. ^{Ring L 21} is formed in the formula (II-1) is, -CONR ²⁵ - or a -COO-, non-aqueous liquid electrolyte for a secondary battery according to any one of claims 1-6. R ²⁵ represents an alkyl group or an aryl group. The electrolyte solution for non-aqueous secondary batteries according to any one of claims 1 to 7, wherein the compound represented by the formula (II-1) is a compound represented by the following formula (II-2). .

In formula, R < ²¹ > -R < ²⁴ > is synonymous with Formula (II-1). L ²² represents an atomic group that forms a ring structure with the carbon atoms of the two carbonyl groups and cyclopropyl group in the formula. Formula (II-1) ring L ²¹ is formed in is a 5- or 6-membered ring, non-aqueous liquid electrolyte for a secondary battery according to any one of claims 1-7. The linking group formed by (L ³¹ ) n in the formula (III-1) is a carbonyloxy group, an oxycarbonyl group, or —CO—NR ³⁵ —, according to any one of claims 1 to 9. Electrolyte for non-aqueous secondary battery. ^{L 32} in the formula (III-1) is an alkylene group, an oxygen atom, a sulfur atom, or ^{-NR 35} - non-aqueous liquid electrolyte for a secondary battery according to any one of claims 1 to 10 is. R ³⁵ represents an alkyl group or an aryl group. The compound represented by the formula (III-1) is a compound represented by the formula (III-2) or a compound represented by the formula (III-3). Electrolyte for non-aqueous secondary batteries as described in 2.

In formula, R < ³¹ > -R < ³⁴ > and L < ³² > are synonymous with Formula (III-1). The electrolyte solution for nonaqueous secondary batteries according to any one of claims 1 to 12, wherein L ³² is an alkylene group having 1 to 3 carbon atoms. The electrolyte solution for nonaqueous secondary batteries according to any one of claims 1 to 13, wherein L ³² is a methylene group. The electrolyte solution for non-aqueous secondary batteries of any one of Claims 1-14 whose compound represented by said Formula (A1) is a compound represented by Formula (A1-1).

In the formula, Ra ⁴¹ is an alkoxy group or a dialkylamino group. Ra ⁴¹ is a dialkylamino group, a non-aqueous liquid electrolyte for a secondary battery according to claim 15.   Furthermore, it contains at least one selected from the group consisting of aromatic compounds, halogen-containing compounds, polymerizable compounds, sulfur-containing compounds, silicon-containing compounds, nitrile compounds, boron-containing compounds, and imide compounds. The electrolyte solution for non-aqueous secondary batteries of any one of -16.   The nonaqueous secondary battery according to any one of claims 1 to 17, wherein the concentration of the phosphazene compound is 1% by mass or more and 20% by mass or less based on the total mass of the electrolyte solution for a nonaqueous secondary battery. Electrolyte.   19. The non-aqueous secondary according to claim 1, wherein the concentration of the cyclopropane compound is 1% by mass or more and 15% by mass or less with respect to the total mass of the electrolyte solution for a non-aqueous secondary battery. Battery electrolyte.   The nonaqueous secondary battery which comprises a positive electrode, a negative electrode, and the electrolyte solution for nonaqueous secondary batteries of any one of Claims 1-19.