JP2014199792A - Additive for nonaqueous electrolyte, nonaqueous electrolyte, and lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an additive for a nonaqueous electrolyte which allows for driving of a power storage device under a high voltage, while maintaining the capacity stably for a long time.SOLUTION: The additive for a nonaqueous electrolyte contains a cyano borate compound represented by general formula (1). (In the formula (1), Mrepresents proton, or an organic or inorganic cation of monovalent, bivalent or trivalent, Y represents H, halogen, a hydrocarbon group, cyano group, -C(O)R, -S(O)R, -Z(R)or -XRwhich may have halogen and a carbon number of 1-10C in the main chain, Rrepresents H, halogen or an organic substituent having carbon number of 1-10C in the main chain, l represents an integer of 1-2, m represents an integer of 1-3, and n represents an integer of 0-10).

Description

  The present invention relates to an additive for a non-aqueous electrolyte used in an electricity storage device such as a lithium ion secondary battery, and more specifically, enables the electricity storage device to be driven under a high voltage and can improve cycle characteristics. The present invention relates to a non-aqueous electrolyte additive.

  Electric storage devices such as electrolytic capacitors, electric double layer capacitors, lithium ion capacitors, and lithium ion secondary batteries are used in a wide range of fields such as power supplies for mobile phones, personal computers, and automobile power supplies. In these electricity storage devices, various studies have been made for the purpose of improving durability and low-temperature characteristics, and these studies also include techniques for improving by adding additives to the electrolyte. . For example, in Patent Document 1, as an additive of an electrolytic solution, an ammonium salt having a structure in which an imidazole ring and an amine are bonded to an alkylene group is used, so that crystals of other ion conductive salts contained in the electrolytic solution are used. And prevention of dendrite formation of metals. Further, in Patent Document 2, when an organometallic compound having a specific structure is used as an additive for a non-aqueous electrolyte, an insulating film having heat resistance is formed on the surface of the positive electrode by a decomposition byproduct of the additive, As a result, it is described that the safety against overcharge of the non-aqueous electrolyte secondary battery is improved.

JP 2009-105028 A Japanese Patent No. 3934557

  However, in order to increase the energy density of the electricity storage device, it is necessary to drive the electricity storage device under a high voltage, and there is still room for improvement in the conventional technology. There is also a need for improvement in durability, that is, cycle characteristics that can withstand long-term use.

  The present invention has been made paying attention to the above-described circumstances, and enables the storage device to be driven under a high voltage without degrading the performance of the electrolyte, and stable capacity maintenance over a long period of time. It is an object of the present invention to provide an additive for a non-aqueous electrolyte solution that can make the above-mentioned possible. Another problem is to provide an electrolytic solution and a lithium secondary battery using this additive.

  This invention which solved the above-mentioned subject is an additive for nonaqueous electrolytes containing the cyanoborate compound denoted by general formula (1).

(In formula (1), M ^{m +} represents a proton, monovalent, divalent, or trivalent organic or inorganic cation, and Y represents the number of carbon atoms in the main chain that may have H, halogen, or halogen. 1 to 10 hydrocarbon group, cyano group, —C (O) R ¹⁴ , —S (O) ₁ R ¹⁴ , —Z (R ¹⁴ ) ₂ or —XR ¹⁴ , wherein R ¹⁴ represents H, halogen or The main chain represents an organic substituent having 1 to 10 atoms, Z represents N or P, X represents O or S, l represents an integer of 1 to 2, and m represents an integer of 1 to 3. And n represents an integer of 0 to 10.)
Y in the above formula (1) is preferably a substituent selected from the group consisting of halogen, a hydrocarbon group having 1 to 10 carbon atoms in the main chain which may have halogen, and a cyano group, It is the most preferred embodiment of the present invention that the non-aqueous electrolyte additive is for a lithium secondary battery.

The present invention also includes a nonaqueous electrolytic solution containing the additive for a nonaqueous electrolytic solution of the present invention, a supporting salt, and a solvent. In this case, the supporting salt is
Formula (6): M′N (R ¹⁵ SO ₂ ) (R ¹⁶ SO ₂ )
Formula (7): M′PF _a (C _b F _{2b + 1} ) _6-a (0 ≦ a ≦ 6, 1 ≦ b ≦ 2),
General formula (8): M′BF _c (C _d F _{2d + 1} ) _4-c (0 ≦ c ≦ 4, 1 ≦ d ≦ 2), and (in the above general formulas (6) to (8), M 'Represents an alkali metal ion, and R ¹⁵ and R ¹⁶ in the general formula (6) each independently represents a fluorine atom or a fluoroalkyl group having 1 to 6 carbon atoms.) It is preferable to include at least one compound selected from the group consisting of compounds. Here, any one of R ¹⁵ and R ¹⁶ is preferably a fluorine atom.

  The present invention also includes a lithium secondary battery using a non-aqueous electrolyte containing the non-aqueous electrolyte additive of the present invention and a lithium secondary battery using the non-aqueous electrolyte of the present invention.

  By using the non-aqueous electrolyte additive of the present invention, the obtained lithium secondary battery can be driven even under a high voltage of 4.4 V, and the cycle characteristics are also good. In addition, the storage capacity retention rate after high-temperature storage is also improved.

FIG. 1 shows the results of a cycle test using electrolytic solutions A to C. FIG. 2 shows the results of the cycle test (discharge capacity retention rate) using the electrolytic solutions A, D, and E. FIG. 3 shows the results of the cycle test using the electrolytic solutions A and F (discharge capacity retention rate). FIG. 4 shows the results of a cycle test using the electrolytic solutions A, D, and E (change in internal resistance). FIG. 5 shows the results of a cycle test using the electrolytic solutions A and F (change in internal resistance).

  The additive for non-aqueous electrolyte of the present invention contains a cyanoborate compound represented by the general formula (1) (hereinafter referred to as compound (1)).

  In the cyanoborate compound (1) according to the present invention, the cyanoborate anion constituting the compound (1) has two ester-bonded substituents bonded to boron, and is bonded to each other to form a ring. It is characterized in that That is, the compound (1) according to the present invention has a structure in which a cyano group, an ester bond, and a substituent Y are bonded to boron. By appropriately selecting the substituent Y, it is expected that the solubility in an organic solvent is improved, and there is an advantage that the range of selection of the electrolytic solution is widened. In addition, it is predicted that the ester bond bonded to boron is appropriately decomposed, and by using the compound (1) of the present invention as an additive for an electrolytic solution, a film is formed on the electrode surface of the electricity storage device, and the solvent or supporting salt The decomposition of (electrolyte) or the like is suppressed, and a stable capacity maintaining action (high cycle characteristics, storage capacity maintaining) can be exhibited without impairing the performance of the supporting salt.

  The film formed by the compound (1) of the present invention is characterized by containing a cyano group. The thermal stability of the coating increases due to the strong electron-attracting properties of the cyano group, which suppresses solvent decomposition at high temperatures and the accompanying gas generation, resulting in the effect of suppressing an increase in internal resistance and battery swelling. The effect which suppresses can be expected. Further, the inclusion of a cyano group increases the oxidation potential of the compound (1) of the present invention, and it is difficult to oxidatively decompose even if only the present compound (1) is exposed to a high voltage. Is present and is expected to form a continuous electrode surface coating. Furthermore, this compound (1) and this film are expected to suppress decomposition of the solvent and the like on the positive electrode by covering the active sites on the positive electrode surface. This effect is presumed to be due to the high affinity of the cyano group for the transition metal. Thus, the stability of the electrode is increased by forming a stable film on the electrode surface, and as a result, a negative electrode additive (for example, vinylene carbonate, fluoroethylene carbonate, ethylene sulfite, 1,3-propane) Decomposition of the sultone or the like on the positive electrode is suppressed, and further performance improvement is expected. Similarly, by forming a film on the negative electrode, propylene carbonate and γ-butyrolactone have excellent properties such as easy dissolution of the electrolyte and high dielectric constant, but are easily reduced and have limited use. It can also be expected that the battery performance is suppressed from lowering when a solvent such as an electrolyte is used.

  Moreover, the compound (1) of this invention can adjust the oxidation potential freely by selecting the substituent Y suitably. Thereby, an insulating film is formed even under high voltage, and the additive has an overcharge preventing function. Further, the introduction of the cyano group stabilizes the compound (1) (cyanoborate compound) of the present invention and makes it difficult to react with other additives.

  On the other hand, this additive having a cyano group that is a central element of boron and a strong electron-attracting group is capable of reducing moisture contained in the electrolyte and lithium fluoride and hydrofluoric acid generated during charge and discharge. The effect of collecting is also expected. If the electrolytic solution contains a large amount of water, decomposition of the supporting salt proceeds, causing problems not only in terms of function but also in terms of safety. In addition, the deposition of lithium fluoride causes battery ignition and causes deterioration of the performance of the electrode surface coating. Hydrofluoric acid is known to cause elution into the electrolyte of the metal used for the positive electrode, and it is important to collect it. Hereinafter, the anion and cation constituting the compound (1) according to the present invention will be described in order.

1-1. Cyanoborate anion In the cyanoborate anion represented by the above general formula (1), n represents an integer of 0 to 10, and is a direct bond or carbon of a methylene group in which two ester bonds bonded to boron are bonded to each other. Indicates a number. n is preferably 0 to 4, more preferably 0 to 2.

Accordingly, as the cyanoborate anion of the present invention, cyanooxalatoborate (n = 0), cyanomalonatoborate (n = 1), cyanosuccinateborate (n = 2), cyanoglutaratoborate (n = 3) And cyano adipolato borate (n = 4). In the cyanoborate anion represented by the above general formula, Y is H, halogen, a hydrocarbon group having 1 to 10 carbon atoms in the main chain which may have halogen, a cyano group, -C (O) R. ¹⁴ , —S (O) ₁ R ¹⁴ , —Z (R ¹⁴ ) ₂ or —XR ¹⁴ is represented.

  When the substituent Y constituting the cyanoborate anion is halogen, Y includes F, Cl, Br, or I. Among halogens, F (fluorine) is preferable because of its high affinity with boron atoms and stable BF bond.

  When the substituent Y is a hydrocarbon group having 1 to 10 carbon atoms in the main chain, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, sec- C 1-10 alkyl groups such as butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl; vinyl, propenyl, isopropenyl, allyl, 1- Carbon such as butenyl group, 2-butenyl group, 3-butenyl group, 1,3-butadienyl group, 1-cyclohexenyl group, 2-cyclohexenyl group, 3-cyclohexenyl group, methylcyclohexenyl group, ethylcyclohexenyl group An alkenyl group having 1 to 10 carbon atoms; an alkynyl having 1 to 10 carbon atoms such as an ethynyl group, a propargyl group, a cyclohexylethynyl group, and a phenylethynyl group; ; Include; phenyl group, a benzyl group, a thienyl group, a pyridyl group, an aryl group or a heteroatom-containing aryl group having 6 to 10 carbon atoms such as an imidazolyl group.

  Examples of the halogenated hydrocarbon group having 1 to 10 carbon atoms in the main chain include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a chloromethyl group, a bromomethyl group, an iodomethyl group, a difluorochloromethyl group, and a fluorodichloromethyl group. , Fluoroethyl group, difluoroethyl group, trifluoroethyl group, tetrafluoroethyl group, perfluoroethyl group, fluorochloroethyl group, chloroethyl group, fluoropropyl group, perfluoropropyl group, fluorochloropropyl group, perfluorobutyl group Perfluorooctyl group, pentafluorocyclohexyl group, perfluorocyclohexyl group, pentafluorophenyl group, perchlorophenyl group, fluoromethylene group, fluoroethylene group, fluorocyclohexene group, etc. Some or all of the hydrogen atoms halogen (F, Cl, Br or I) halogenated alkyl group or halogenated aryl groups substituted with the like.

The hydrocarbon group Y having 1 to 10 carbon atoms in the main chain which may have a halogen has a substituent (for example, an alkoxy group, an amino group, a cyano group, a carbonyl group, a sulfonyl group, etc.). May be. Moreover, you may have a functional group containing hetero atoms, such as Si, B, O, N, and Al. Examples of the functional group containing a hetero atom include a cyano group, a trimethylsilyl group, a triethylsilyl group, a dimethoxyaluminum group, —CH ₂ CH ₂ B (CN) ₃ , —C ₃ H ₆ B (CN) _{3 and the} like. . When the substituent Y contains an electrophilic substituent such as a cyano group, the withstand voltage of the cyanoborate salt is increased, which is preferable.

  As described above, when Y is a hydrocarbon group having 1 to 10 carbon atoms in the main chain which may have a halogen, the solubility of the cyanoborate salt in an organic solvent is improved. When used as an additive for an electrolytic solution, a high-performance electrolytic solution can be obtained, which is preferable.

In the above -C (O) R ¹⁴ , -S (O) ₁ R ¹⁴ , -Z (R ¹⁴ ) ₂ and -XR ¹⁴ , R ¹⁴ is H, halogen or the number of atoms of the main chain is 1 to 10 Represents an organic substituent. As the halogen, F, Cl, Br, or I is preferable. The organic substituent may be linear, branched or cyclic, and may have two or more of these structures, or may have a substituent. Furthermore, the organic substituent R ¹⁴ may contain an unsaturated bond. The number of atoms in the main chain of the organic substituent R ¹⁴ is as described above, but the number of carbons (including the substituent) contained in the organic substituent R ¹⁴ is preferably in the range of 1 to 20, more preferably. Is in the range of 1-10. The organic substituent R ¹⁴ may contain hetero atoms other than carbon and hydrogen (O, N, Si, etc.) and halogen atoms (F, Cl, Br, etc.), and the number and position thereof are particularly limited. There is no. Therefore, for example, in the case of Y in the general formula (1), when Y is —XR ¹⁴ , the type of atoms adjacent to X is not particularly limited to carbon, and is, for example, a heteroatom such as Si or Al. There may be. Further, the organic substituent R ¹⁴ may be composed only of atoms other than carbon.

Specific examples of the organic substituent R ¹⁴ include organic groups including saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, cyanated hydrocarbon groups, alkoxylated and / or aryloxylated hydrocarbon groups, and alkanoyl groups. Substituent, organic substituent having an ester bond, nitrogen-containing organic substituent, group having a thioalkoxy structure, organic substituent having a sulfinyl group, organic substituent having a sulfonyl group, organic substituent having a hetero atom, -CH ₂ CH ₂ OB (CN) ₃ , —C ₃ H ₆ OB (CN) ₃ ; The organic substituent R ¹⁴ may include linear, branched, cyclic, or a combination thereof.

When Y is represented by —C (O) R ¹⁴ , R ¹⁴ is a saturated or unsaturated hydrocarbon group or halogenated hydrocarbon group, alkoxylated or aryloxylated hydrocarbon group, or nitrogen-containing An organic substituent is preferable, and R ¹⁴ is more preferably a methyl group, an ethyl group, a phenyl group, a trifluoromethyl group, or a pentafluorophenyl group. Therefore, as the substituent Y, acetyl group, propanoyl group, butanoyl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, isobutanoyl group, trifluoroacetyl group, benzoyl group, pentafluorobenzoyl group, acryloyl group, methacryloyl group Including linear, branched, cyclic, or combinations thereof, such as methyl oxalyl group (—COCOCH ₃ ), methyl malonyl group (—COCH ₂ COCH ₃ ), methyl succinyl group (—COCH ₂ CH ₂ COCH ₃ ) Organic substituents containing alkanoyl group, acetoxymethylcarbonyl group, acetoxyethylcarbonyl group, benzoyloxyethylcarbonyl group, methoxycarbonyl group, ethoxycarbonyl group, methoxyethyleneoxycarbonyl group, etc., linear, branched, Organic substituents having an ester bond, including amide groups, combinations thereof; nitrogen-containing organic substituents including linear, branched, cyclic, or combinations thereof, such as amide groups, N-alkylamide groups, and N-phenylamide groups Is mentioned.

When Y is represented by —S (O) ₁ R ¹⁴ , R ¹⁴ is preferably a halogen, a saturated or unsaturated hydrocarbon group or a halogenated hydrocarbon group, more preferably a halogen, A halogenated hydrocarbon group; Specifically, as —S (O) ₁ R ¹⁴ , a fluorosulfinyl group, a chlorosulfinyl group, a trifluoromethylsulfinyl group, a pentafluoroethylsulfinyl group, a phenylsulfinyl group, a pentafluorophenylsulfinyl group, a tolylsulfinyl group, etc. Sulfonyl groups (l = 1), fluorosulfonyl groups, chlorosulfonyl groups, trifluoromethylsulfonyl groups, pentafluoroethylsulfonyl groups, tolylsulfonyl groups, phenylsulfonyl groups, pentafluorophenylsulfonyl groups and the like (l = 2) ) Is more preferable.

-C (O) R ¹⁴ and -S (O) ₁ R ¹⁴ are electron-withdrawing substituents like the cyano group and delocalize the negative charge charged in the central element. Therefore, improvement in withstand voltage when used as an additive can be expected.

When Y is represented by —Z (R ¹⁴ ) ₂ , amino groups such as dimethylamino group and ethylmethylamino group where Z is N; Z such as diphenylphosphino group and dicyclohexylphosphino group is P A certain phosphino group;

When Y is represented by —XR ¹⁴ , X is O, and R ¹⁴ may have a halogenated hydrocarbon group having 1 to 20 carbon atoms (for example, methyl group, ethyl group, phenyl group) Group, a saturated hydrocarbon group or an unsaturated hydrocarbon group such as a pentafluorophenyl group, a trifluoromethyl group, or a pentafluoroethyl group); X is O, and R ¹⁴ is an alkylsilyl group (for example, trimethylsilyl group) An alkanoyl group (for example, an acetyl group, a triethylsilyl group, etc.) wherein X is O and R ¹⁴ is selected from monovalent, linear, branched, cyclic, or combinations thereof Fluoroacetyl, propanoyl, butanoyl, pentanoyl, hexanoyl, heptanoyl, octanoyl, isopropanoyl, isobutanoyl, benzoyl, penta Fluorobenzoyl group, an acryloyl group, a methacryloyl group, methyl oxalyl group, methylmalonyl group, group a Mechirusukushiniru group); a X is O, R ¹⁴ is a sulfinyl group (e.g., fluoro-sulfinyl group, chloro sulfinyl group, A trifluoromethylsulfinyl group, a tolylsulfinyl group, etc.) or a sulfonyl group (a fluorosulfonyl group, a chlorosulfonyl group, a trifluoromethylsulfonyl group, a tolylsulfonyl group, etc.); X is S, and R ¹⁴ is Groups (for example, a methylthio group, a trifluoromethylthio group, etc.) which are C1-C20 hydrocarbon groups which may have a halogen, etc. are mentioned. X is O or S, but X is preferably O from the viewpoint of easy availability of raw materials and cost.

When Z (R ¹⁴ ) ₂ or XR ¹⁴ is introduced into the cyanoborate salt, it becomes a salt having not only high withstand voltage but also excellent solubility in a solvent, and the range of choice of electrolyte to be added is widened. In this case, it is preferable that R ¹⁴ contains an electron-withdrawing substituent because the withstand voltage of the cyanoborate anion increases and the withstand voltage of the electrolyte to be added also increases. Specifically, R ¹⁴ preferably contains an alkanoyl group, a sulfinyl group, or a sulfonyl group. Similarly, R ¹⁴ is preferably fluorine or a group containing fluorine such as a fluoroalkyl group.

Of these substituents Y, a cyano group, halogen, and XR ¹⁴ are particularly preferable.

  The anion of the cyanoborate compound of the present invention may be cyanoborate anions represented by the following general formulas (8-1) and (8-2).

(In the general formulas (8-1) and (8-2), X represents O, and p represents an integer of 0 to 10. Preferably, p is 0 to 4, and 0 to 1. More preferred.)

  More specific examples of the anion of the cyanoborate compound of the present invention include those represented by the following formulas (10-1) to (10-14) (n is an integer of 0 to 2, 1 is preferable, and 0 is more preferable. Preferred anions include (10-1), (10-2), (10-3), (10-4), (10-7), (10-9) and (10-10).

1-2. Proton (H ⁺ ), organic or inorganic cation; M ^{m +}
The organic cation M ^{m +} constituting the compound (1) of the present invention is represented by the general formula (2): L ⁺ -R _S (wherein L represents C, Si, N, P, S or O, R Are the same or different organic groups, and may be bonded to each other, s represents the number of R bonded to L, and is 3 or 4. Here, s is directly related to the valence of element L and L The onium cation represented by (the value determined by the number of double bonds to be bonded) is preferable.

  The “organic group” represented by R means a group having at least one hydrogen atom, fluorine atom, or carbon atom. The “group having at least one carbon atom” only needs to have at least one carbon atom, and may have another atom such as a halogen atom or a hetero atom, a substituent, or the like. Good. Examples of the substituent include amino group, imino group, amide group, ether bond group, thioether bond group, ester group, hydroxyl group, alkoxy group, carboxyl group, carbamoyl group, cyano group, disulfide group, nitro group. Group, nitroso group, sulfonyl group and the like.

  Examples of the onium cation represented by the general formula (2) include those represented by the following general formula.

(R in the formula is the same as in the general formula (2))

  Among the six onium cations represented by the above general formula, those in which L is N, P, S or O are more preferable, and onium cations in which L is N are more preferable. The said onium cation may be used independently and may use 2 or more types together. Specifically, examples of the onium cation in which L is N, P, S, or O include those represented by the following general formulas (3) to (5).

  General formula (3):

At least one of 15 types of heterocyclic onium cations represented by the formula:

Examples of the organic groups R ^{1 to} R ⁸ include the same organic groups R exemplified in the general formula (2). More specifically, R ^{1 to} R ⁸ are a hydrogen atom, a fluorine atom, or an organic group. Examples of the organic group include a straight chain, a branched chain, or a ring (provided that R ^{1 to} R ⁸ are bonded to each other to form a ring). Are preferably a hydrocarbon group having 1 to 18 carbon atoms or a fluorine group, and more preferably a hydrocarbon group having 1 to 8 carbon atoms or a fluorine group. Moreover, the organic group may contain the substituent illustrated about the said General formula (2), hetero atoms, such as N, O, and S, and a halogen atom.

  General formula (4):

(Wherein R ^{1 to} R ¹² are the same as R ^{1 to} R ^{8 in} the general formula (3))
At least one of nine types of saturated ring onium cations represented by the formula:

  General formula (5):

(Wherein R ^{1 to} R ⁴ are the same as R ^{1 to} R ^{8 in} the general formula (3))
A chain onium cation represented by

For example, as the chain onium cation represented by the general formula (5), tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetraheptylammonium, tetrahexylammonium, tetraoctylammonium, triethylmethylammonium, methoxy Ethyl diethylmethylammonium, trimethylphenylammonium, benzyltrimethylammonium, benzyltriethylammonium, benzyltributylammonium, dimethyldistearylammonium, diallyldimethylammonium, 2-methoxyethoxymethyltrimethylammonium and tetrakis (pentafluoroethyl) ammonium, N-methoxytrimethyl Ammonium, N-ethoxylate Quaternary ammoniums such as methylammonium and N-propoxytrimethylammonium, tertiary ammoniums such as trimethylammonium, triethylammonium, tributylammonium, diethylmethylammonium, dimethylethylammonium and dibutylmethylammonium, dimethylammonium and diethylammonium, Secondary ammoniums such as dibutylammonium, primary ammoniums such as methylammonium, ethylammonium, butylammonium, hexylammonium and octylammonium, and ammonium compounds represented by NH ₄ are included.

  Among the onium cations of the above general formulas (3) to (5), an onium cation containing a nitrogen atom is more preferable, and a more preferable one is the following general formula:

(Wherein, R ¹ to R ¹² are the same as R ¹ to R ⁸ of general formula (3).)
And at least one of six kinds of onium cations represented by the formula:

  Among the six kinds of onium cations, chain quaternary ammonium such as tetraethylammonium, tetrabutylammonium and triethylmethylammonium, chained tertiary ammonium such as triethylammonium, tributylammonium, dibutylmethylammonium and dimethylethylammonium, Pyrrolidiniums such as 1-ethyl-3-methylimidazolium and imidazolium such as 1,2,3-trimethylimidazolium, N, N-dimethylpyrrolidinium and N-ethyl-N-methylpyrrolidinium are readily available. It is more preferable because it exists. More preferred are quaternary ammonium and imidazolium. From the viewpoint of reduction resistance, quaternary ammonium such as tetraethylammonium, tetrabutylammonium and triethylmethylammonium classified into the chain onium cation is more preferable.

Examples of the inorganic cation M ^{m +} include monovalent inorganic cations M ¹⁺ such as Li ⁺ , Na ⁺ , K ⁺ , Cs ⁺ , and Pb ⁺ ; Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Pd ²⁺ , Sn ^{2 +, Hg 2+, Rh 2+,} Cu 2+, Be 2+, Sr 2+, 2 divalent inorganic cations M ²⁺ of Ba ^2+, and the like; and trivalent inorganic cation M ³ of Ga ³⁺ etc. ⁺ . Among these, Li ⁺ , Na ⁺ , Mg ^2+, and Ca ²⁺ are preferable because they have a small ionic radius and can be easily used for power storage devices and the like, and a more preferable inorganic cation M ^{m +} is Li ⁺ .

  The compound (1) according to the present invention includes all compounds composed of combinations of the above cations and anions. Specific compounds (1) include triethylmethylammonium cyanofluorooxalatoborate, triethylammonium dicyanooxalatoborate, tributylammonium dicyanooxalatoborate, triethylammonium dicyanomalonatoborate, 1-ethyl-3-methylimidazolium dicyano. Oxalatoborate, triethylmethylammonium dicyanosuccinateborate, triethylmethylammonium dicyanooxalateborate (triethylmethylammonium dicyanooxalylborate), triethylmethylammoniummethylcyanooxalateborate, triethylmethylammonium trifluoromethylcyanooxalateborate, 1- Ethyl-3-methylimidazolium cyanophenylmalonatobo Salts of organic cations such as lithium salt; lithium cyanophenyl oxalate borate, sodium dicyano oxalate borate, magnesium bis (dicyano oxalate borate), lithium trifluoromethyl cyanosuccinate borate, lithium cyanophenyl oxalate ethoxyborate, lithium cyano Pentafluorophenoxyoxalatobutoxyborate, lithium trifluoromethoxycyanomalonatoborate, lithium cyano (pentafluorophenoxy) succinateborate, lithium cyano (acetoxy) oxalatoborate, lithium cyano (trifluoroacetoxy) malonatoborate, lithium cyano (( Methoxycarbonyl) oxo) oxalatoborate, lithium cyano (fluorosulfonate) oxalatoborate, lithium Thium cyano (trifluoromethanesulfonate) oxalate borate, lithium cyano (methanesulfonate) oxalate borate, lithium cyano (p-toluenesulfonate) oxalate borate, lithium cyano (fluorosulfonyl) oxalate borate, lithium cyano (acetyl) Oxalatoborate, lithium cyano (trifluoroacetyl) oxalatoborate, lithium cyano (trimethylsiloxy) oxalatoborate, lithium dicyanooxalatoborate (lithium dicyanooxalylborate), lithium cyanofluorooxalatoborate (lithium cyanofluorooxalylborate) And salts of inorganic cations such as

1-3. Addition amount of additive The additive for non-aqueous electrolyte of the present invention is used by being added to the non-aqueous electrolyte. As addition amount, 0.01-20 mass% is preferable in 100 mass% of non-aqueous electrolyte. If the amount is too small, the additive effect does not appear. If the amount is too large, the concentration of the electrolytic solution increases and the charge transfer efficiency decreases, or the supporting salt separates and precipitates in the electrolytic solution, which adversely affects the device. there is a possibility. Moreover, since the cost rise by the large amount use of the additive of this invention also arises, it is not preferable. A more preferable addition amount is 0.03 to 15% by mass, and further preferably 0.05 to 10% by mass.

  The use amount of the additive for non-aqueous electrolyte of the present invention is preferably 0.05 to 50 mol% when the total amount of the additive and the supporting salt described later is 100 mol%. If the amount is too small, the additive effect does not appear. If the amount is too large, the concentration of the electrolytic solution increases and the charge transfer efficiency decreases, or the supporting salt separates and precipitates in the electrolytic solution, which adversely affects the device. there is a possibility. Moreover, since the cost rise by the large amount use of the additive of this invention also arises, it is not preferable. A more preferable addition amount is 0.1 to 30 mol%, and further preferably 0.1 to 10 mol%.

2-1. Production Method The cyanoborate compound represented by the general formula (1) can be produced by reacting a specific boron compound with an alkylsilyl compound or a metal cyanide. In addition, you may use the halogen salt of an organic or inorganic cation for the said reaction as needed.

As a preferable boron compound that can be used in the above production method, an organic halogen represented by a general formula of B (Y ′) _q (X ¹⁵ ) _3-q or M ⁺ B (Y ′) _q (X ¹⁵ ) _4-q compounds (Y ', M ⁺ similarly Y in the general formula (1), and M ^{m +} is an m = 1, X ¹⁵ is a halogen, q represents 2 or 3). Among these, B (Y) _t (X) _1-t (OCO (CH ₂ ) _n COO) or M ⁺ B (Y) _t (X) _2−t (OCO (CH ₂ ) _n COO) (where Y As in the definition in the general formula (1), X is a halogen, and n = 0 to 10, t = 0 or 1) can be suitably used. Specifically, LiB (F) ₂ (OCOCOO), LiB (F) (Me) (OCOCOO), LiB (F) (CF ₃ ) (OCOCOO), LiB (F) (OSO ₂ CF ₃ ) (OCOCOO) _{, LiB (F) 2 (OCOCH} 2 COO), LiB (Cl) (OCH 2 CH = CH 2) (OCOCOO), LiB (OSO 2 F) (F) (OCOCH 2 CH 2 COO), Et 3 NHB (F ) (OCOCF ₃ ) (OCOCOO), Et ₃ MeNB (Ph) (F) (OCOCOO), EMImB (OCOCH ₃ ) (Cl) (OCOCH ₂ COO), Et ₄ NB (OCF ₃ ) (F) (OCOCOO), _{Et 3 MeNB (OCOPh) (F} ) (OCOCOO), LiB (OMe) (F) (OCOCOO), LiB (CH 2 CH = CH 2) , such as (F) (OCOCOO), And androgenic, alkyl group, and an organic group such as an aryl group or an alkanoyl group, an organic boron halide compound bonded to the boron and the like. In addition, said organic boron halide compound can be manufactured with reference to the method as described in Chemistry-A European Journal 2009, 15, 10, p2270-p2272, for example.

  As a cyan source for introducing a cyano group into the organic boron halide compound, an alkylsilyl compound or a metal cyanide can be used. Specific examples of the alkylsilyl compound include trimethylsilylcyanide, triethylsilylcyanide, triisopropylsilylcyanide, alkyldimethylcyanide such as ethyldimethylsilylcyanide, isopropyldimethylsilyl chloride, tert-butyldimethylsilylcyanide; dimethyl Examples thereof include alkylarylsilyl cyanides such as phenylsilylcyanide and phenyldimethylsilylcyanide. Examples of the metal cyanide include copper cyanide, zinc cyanide, potassium cyanide, sodium cyanide, lithium cyanide and the like. Of these, alkylsilylcyanides or alkylarylsilylcyanides are preferably used. More preferred is trialkylsilyl cyanide. More preferred is trimethylsilylcyanide.

  The above production method may be performed in the presence of a halogen salt of an organic or inorganic cation. As the halogen constituting the halogen salt of an organic or inorganic cation, F, Cl, Br and I are preferable, and Cl or Br is more preferable. On the other hand, the organic or inorganic cation constituting the halogen salt of an organic or inorganic cation includes the organic or inorganic cation constituting the compound (1) described above.

  Preferred halogen salts of organic or inorganic cations include triethylammonium bromide, tributylammonium bromide, triethylmethylammonium bromide, 1-ethyl-3-methylimidazolium bromide, lithium bromide, triethylammonium chloride, tributylammonium chloride, triethylmethylammonium chloride. 1-ethyl-3-methylimidazolium chloride, triethylmethylammonium chloride, and lithium chloride. More preferred halogen salts of organic or inorganic cations are triethylammonium bromide, triethylmethylammonium bromide, lithium bromide, triethylammonium chloride, triethylmethylammonium chloride, lithium chloride, and more preferably triethylammonium bromide, triethylmethylammonium bromide, Lithium bromide.

  The amount of the halogen salt of the organic or inorganic cation used is preferably 1: 5 to 5: 1 (boron compound: halogen salt of organic or inorganic cation, molar ratio) with respect to the boron compound. More preferably, it is 1: 2 to 2: 1, and still more preferably 1: 0.8 to 1: 1.2. If the blending amount of the organic or inorganic cation halogen salt is too small, removal of by-products may be insufficient, or the amount of cation may be insufficient and the target product may not be efficiently produced. On the other hand, when the amount of the halogen salt of the organic or inorganic cation is too large, the halogen salt of the organic or inorganic cation tends to remain as an impurity.

  In the said manufacturing method, in order to advance reaction uniformly, it is preferable to use a reaction solvent. The reaction solvent is not particularly limited as long as it dissolves the above raw materials, and water or an organic solvent is used. Examples of organic solvents include hydrocarbon solvents such as toluene, xylene, benzene and hexane, chlorine solvents such as chloroform, dichloromethane, dichloroethane, chlorobenzene and dichlorobenzene, diethyl ether, cyclohexyl methyl ether, dibutyl ether, dimethoxyethane, and dioxane. , Ether solvents such as tetrahydrofuran and dioxolane, ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as 2-butanone and methyl isobutyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol and butanol, acetonitrile , Nitrile solvents such as isobutyronitrile, valeronitrile, benzonitrile, γ-butyrolactone, ε-caprolactone, ethylene carbonate, propylene carbonate, dimethyl Examples include carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl sulfoxide, dimethylformamide, N-methyl-2-pyrrolidone and the like. These reaction solvents may be used alone or in combination of two or more. Preferred are chlorinated solvents such as chloroform, dichloromethane, dichloroethane, chlorobenzene and dichlorobenzene, and nitrile solvents such as acetonitrile, isobutyronitrile, valeronitrile and benzonitrile. More preferred are nitrile solvents. The reaction conditions are not particularly limited. For example, the reaction temperature may be 20 ° C. to 150 ° C. (more preferably 30 ° C. to 120 ° C., still more preferably 50 ° C. to 100 ° C.), and the reaction time may be 1 hour to 50 hours. (More preferably 2 hours to 10 hours).

2-2. Cation Exchange Reaction The cyanoborate compound obtained by the above production method may further undergo a cation exchange reaction. Since the characteristics of the cyanoborate compound represented by the general formula (1) depend on the cation species, cyanoborate salts having different characteristics can be easily obtained by performing a cation exchange reaction.

  The cation exchange reaction may be performed by reacting the cyanoborate compound represented by the general formula (1) obtained by the above production method with an ionic substance having a desired cation. The ionic substance may be a compound having a desired cation, such as hydroxide, halogen salt, tetrafluoroborate, hexafluorophosphate, perchlorate, bis (trifluoromethanesulfonyl). ) Imide salts and the like. The conditions for the cation exchange reaction are not particularly limited, and the reaction temperature and time may be appropriately adjusted according to the progress of the reaction. Moreover, you may use a solvent as needed, for example, the reaction solvent mentioned above is used preferably.

2-3. Purification In the production method of the present invention, after the above reaction, purification may be performed to further reduce the amount of impurities in the produced compound (1) (crude product) and increase the purity. The purification method is not particularly limited. For example, the product is washed with water, an organic solvent, and a mixed solvent thereof, the oxidizing agent treatment in which the product is brought into contact with an oxidizing agent, the adsorption purification method, the reprecipitation method, the liquid separation. Any conventionally known purification methods such as extraction, recrystallization, crystallization, and purification by chromatography can be employed.

  These purification methods may be implemented individually by 1 type, or may combine 2 or more types. In addition, from the viewpoint of reducing the impurities, it is preferable to employ at least one of an oxidant treatment, an adsorption purification method, a liquid separation extraction method, and a crystallization method, and it is particularly preferable to implement all of them.

3-1. Nonaqueous Electrolyte The nonaqueous electrolyte of the present invention comprises the additive for nonaqueous electrolyte of the present invention, a supporting salt, and a solvent.

3-2. Support salt (electrolyte)
As the supporting salt, a conventionally known non-aqueous electrolyte solution electrolyte can be used and is not particularly limited. Those having a large dissociation constant in the electrolytic solution and having an anion that is difficult to solvate with a non-aqueous solvent described later are preferred. Examples of the cation species constituting the supporting salt include alkali metal ions such as Li ⁺ , Na ⁺ and K ⁺ , alkaline earth metal ions such as Ca ²⁺ and Mg ²⁺ , and the above-described onium cation.

On the other hand, examples of the anion species include anions, Cl ⁻ , Br ⁻ , ClO ₄ ⁻ , AlCl ₄ ⁻ , C [(CN) ₃ ] ⁻ , N [(CN) included in the general formulas (6) to (8) described later. ) ₂ ] ⁻ , CF ₃ (SO ₃ ) ⁻ , C [(CF ₃ SO ₂ ) ₃ ] ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ and dicyanotriazolate ion (DCTA).

Specific supporting salts include alkali metal salts and alkaline earth metal salts of trifluoromethanesulfonic acid such as LiCF ₃ SO ₃ , NaCF ₃ SO ₃ , KCF ₃ SO ₃ ; LiC (CF ₃ SO ₂ ) ₃ , LiN ( Alkali metal salts and alkaline earth metal salts of perfluoroalkanesulfonic acid imides such as CF ₃ CF ₂ SO ₂ ) ₂ and LiN (FSO ₂ ) ₂ ; alkalis of hexafluorophosphoric acid such as LiPF ₆ , NaPF ₆ and KPF ₆ metal salts and alkaline earth metal salts; tetrafluoroborate salt such as _{LiBF 4, NaBF 4;; LiClO} 4, NaClO 4 perchlorate alkali metal salts and alkaline earth metal salts such as _{LiAsF 6, LiI, LiSbF 6,} LiAlO ₄ , alkali metal salts such as LiAlCl ₄ , LiCl, NaI, NaAsF ₆ , KI; tetraethylammonium perchlorate Quaternary ammonium salts of perchloric acid and the _{like; (C 2 H 5) 4} NBF 4, (C 2 H 5) 3 (CH 3) quaternary ammonium salts of tetrafluoroborate of ₄ such NBF; (C ₂ Quaternary ammonium salts such as H ₅ ) ₄ NPF ₆ ; quaternary phosphonium salts such as (CH ₃ ) ₄ P · BF ₄ , (C ₂ H ₅ ) ₄ P · BF _{4, and the} like. A polymer electrolyte may be used as the electrolyte. A polymer electrolyte is one in which an electrolyte is supported on a base polymer. For example, a polymer electrolyte obtained by impregnating a polymer with the electrolytic solution of the present invention (polymer gel electrolytic solution) or a solid solution in a base polymer. (Intrinsic polymer electrolyte).

  Particularly preferred are the supporting salts represented by the following general formulas (6) to (8).

Formula (6): M′N (R ¹⁵ SO ₂ ) (R ¹⁶ SO ₂ )
Formula (7): M′PF _a (C _b F _{2b + 1} ) _6-a (0 ≦ a ≦ 6, 1 ≦ b ≦ 2),
General formula (8): M′BF _c (C _d F _{2d + 1} ) _4-c (0 ≦ c ≦ 4, 1 ≦ d ≦ 2), and (in the above general formulas (6) to (8), M 'Represents an alkali metal ion, and R ¹⁵ and R ¹⁶ in the general formula (6) each independently represents a fluorine atom or a fluoroalkyl group having 1 to 6 carbon atoms.) At least one compound selected from the group consisting of compounds is preferred. As the alkali metal ion, lithium ion, sodium ion, potassium ion, rubidium ion, and cesium ion are preferable, lithium ion, sodium ion, and potassium ion are more preferable, and lithium ion is more preferable.

3-2-1. Compound represented by general formula (6)
The compound represented by the following general formula (6) (hereinafter referred to as compound (6)) can be said to be an imide-based alkali metal salt.

Formula (6): M′N (R ¹⁵ SO ₂ ) (R ¹⁶ SO ₂ )
(In the formula, M ′ represents an alkali metal ion, and R ¹⁵ and R ¹⁶ independently represent a fluorine atom or a C 1-6 fluoroalkyl group.)
One of R ¹⁵ and R ¹⁶ is preferably a fluorine atom. The fluoroalkyl group having 1 to 6 carbon atoms may be linear, branched, cyclic, or a combination thereof. The fluoroalkyl group may be any group in which part of the hydrogen atoms bonded to the carbon atom is replaced with a fluorine atom. Specific examples of the fluoroalkyl group include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a pentafluoroethyl group, a fluoropropyl group, a fluoropentyl group, and a fluorohexyl group. Groups and the like. R ¹⁵ and R ¹⁶ are preferably a fluorine atom, a trifluoromethyl group, or a pentafluoroethyl group. In addition, when one of R ¹⁵ and R ¹⁶ is a fluoroalkyl group, the other is preferably a fluorine atom (F).

  Preferred compounds (6) include lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, lithium bis (pentafluoroethylsulfonyl) imide, lithium (fluorosulfonyl) (trifluoromethylsulfonyl) imide, lithium (Fluorosulfonyl) (pentafluoroethylsulfonyl) imide, potassium bis (fluorosulfonyl) imide, potassium bis (trifluoromethylsulfonyl) imide, potassium bis (pentafluoroethylsulfonyl) imide, potassium (fluorosulfonyl) (trifluoromethylsulfonyl) ) Imide, sodium bis (fluorosulfonyl) imide, sodium bis (trifluoromethylsulfonyl) imide, sodium bis (pentafluoro) Tilsulfonyl) imide, sodium (fluorosulfonyl) (trifluoromethylsulfonyl) imide, and more preferably lithium bis (fluorosulfonyl) imide, lithium (fluorosulfonyl) (trifluoromethylsulfonyl) imide, lithium (fluorosulfonyl) ) (Pentafluoroethylsulfonyl) imide, more preferably lithium bis (fluorosulfonyl) imide. As these imide-based alkali metal salts, commercially available products may be used, or those synthesized by a conventionally known method may be used.

3-2-2. Compound Represented by General Formula (7) A compound represented by the following general formula (7) (hereinafter referred to as compound (7)) is a fluorine-containing salt compound.

General formula (7): M′PF _a (C _b F _{2b + 1} ) _6-a (0 ≦ a ≦ 6, 1 ≦ b ≦ 2)
Specific examples include LiPF ₆ and LiPF ₃ (C ₂ F ₅ ) ₃ , and LiPF ₆ is preferred.

3-2-3. Compound represented by general formula (8) A compound represented by the following general formula (8) (hereinafter referred to as compound (8)) is a fluorine-containing salt compound.

General formula (8): M′BF _c (C _d F _{2d + 1} ) _4-c (0 ≦ c ≦ 4, 1 ≦ d ≦ 2)
Specifically, LiBF ₄ and LiBF (CF _{3) 3} and the like, LiBF ₄ are preferred.

3-2-4. Concentration of supporting salt The supporting salt is one or more of compounds (6) to (8), and the concentration is the sum of these compounds, and the concentration is 0.1 mol / L in the nonaqueous electrolyte. As mentioned above, it is preferable to use it so that it may become a saturated concentration or less. More preferably, it is 0.2 mol / L to 2.5 mol / L, still more preferably 0.3 mol / L to 2 mol / L, still more preferably 0.6 mol / L to 1.8 mol / L, Still more preferably, it is 0.8 mol / L-1.4 mol / L.

3-3. solvent
The solvent contained in the non-aqueous electrolyte of the present invention is not particularly limited as long as it can dissolve the supporting salt and the additive for non-aqueous electrolyte of the present invention. As the non-aqueous solvent, a solvent having a large dielectric constant, high solubility of the supporting salt and the additive for non-aqueous electrolyte of the present invention, a boiling point of 60 ° C. or higher, and a wide electrochemical stability range is preferable. An organic solvent (non-aqueous solvent) having a low water content is preferable. Examples of such organic solvents include ethylene glycol dimethyl ether (1,2-dimethoxyethane), ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, Ethers such as tetraethylene glycol dimethyl ether, 1,4-dioxane, 1,3-dioxolane; chains such as dimethyl carbonate, ethyl methyl carbonate (methyl ethyl carbonate), diethyl carbonate (diethyl carbonate), diphenyl carbonate, methyl phenyl carbonate Carbonates: ethylene carbonate (ethylene carbonate), propylene carbonate (propylene carbonate), 2,3-dimethylethylene carbonate, butyric carbonate , Cyclic carbonates such as vinylene carbonate and 2-vinylethylene carbonate; aliphatic carboxylic acid esters such as methyl formate, methyl acetate, propionic acid, methyl propionate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate; Aromatic carboxylic acid esters such as methyl acid and ethyl benzoate; carboxylic acid esters such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; trimethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, phosphorus Phosphate esters such as triethyl acid; Nitriles such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile, isobutylnitrile; N-methylformamide, N-Echi Amides such as formamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidinone, N-vinylpyrrolidone; dimethylsulfone, ethylmethylsulfone, diethylsulfone, sulfolane, 3-methylsulfolane, 2,4 -Sulfur compounds such as dimethylsulfolane: alcohols such as ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether; sulfoxides such as dimethyl sulfoxide, methyl ethyl sulfoxide, diethyl sulfoxide; benzonitrile, tolunitrile, etc. Aromatic nitriles; nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone , 3-methyl-2-oxazolidinone and the like. Among these, chain carbonic acid esters, cyclic carbonic acid esters, aliphatic carboxylic acid esters, carboxylic acid esters, and ethers are preferred, dimethyl carbonate, ethyl methyl carbonate (ethyl methyl carbonate), diethyl carbonate, ethylene carbonate, Propylene carbonate, γ-butyrolactone, γ-valerolactone and the like are more preferable. The said solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

4). Electric storage device The nonaqueous electrolytic solution of the present invention is suitably used as an electrolytic solution or an electrolytic solution material for various electric storage devices. As an electricity storage device provided with the electrolytic solution of the present invention, a battery having a charging and discharging mechanism such as a primary battery, a lithium (ion) secondary battery, a fuel cell, an electrolytic capacitor, an electric double layer capacitor, a lithium ion capacitor, Among these, a lithium ion secondary battery will be described in more detail.

Lithium ion secondary battery A lithium ion secondary battery is composed of a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution as basic components. The lithium ion secondary battery of the present invention is provided with the electrolytic solution of the present invention, that is, the non-aqueous electrolytic solution containing the additive for non-aqueous electrolytic solution of the present invention as the electrolytic solution of the basic component. The lithium ion secondary battery having the above configuration can be driven even under a high voltage of 4.4 V, and the cycle characteristics are also good.

A lithium ion secondary battery uses a carbon material such as graphite as a negative electrode active material, which will be described later, and a compound containing a metal oxide such as LiCoO ₂ as a positive electrode active material. In the secondary battery, at the time of charging, for example, a reaction of C ₆ Li → 6C + Li + e occurs in the negative electrode, and electrons (e) generated on the negative electrode surface are ion-conducted in the electrolytic solution and move to the positive electrode surface. Then, for example, a reaction of CoO ₂ + Li + e → LiCoO ₂ occurs, and a current flows from the negative electrode to the positive electrode. On the other hand, at the time of discharging, a reverse reaction at the time of charging occurs, and a current flows from the positive electrode to the negative electrode. Thus, in a lithium ion secondary battery, electricity is stored or supplied by a chemical reaction caused by ions.

  The lithium ion secondary battery of the present invention has a positive electrode, a negative electrode, and an electrolytic solution. A separator is provided between the positive electrode and the negative electrode in order to prevent a short circuit due to contact between the two.

  Each of the positive electrode and the negative electrode is composed of a current collector, a positive electrode active material or a negative electrode active material, a conductive agent, a binder (binder material), and the like. It is formed by forming a thin coating film, sheet or plate on the top.

The positive electrode is not particularly limited, and a known positive electrode can be used. For example, a positive electrode current collector, a positive electrode active material, a conductive agent, a binder, and the like are used. Examples of the positive electrode current collector include aluminum and stainless steel. Examples of the positive electrode active material include LiNiVO ₄ , LiCoPO ₄ , LiCoVO ₄ , LiCrMnO ₄ , LiCr _x Mn _2−x O ₄ (0 <x <0.5), LiCr _0.2 Ni _0.4 Mn _1.4 O ₄ , LiPtO ₃ , Li _x Fe ₂ (SO ₄ ) ₃ , LiFeO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiCoO ₂ , LiMn _1.6 Ni _0.4 O ₄ , LiFePO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNi _0.5 Mn _1.5 O ₄ , LiNi _0.8 Co _0.2 O ₂ , LiNiO ₂ , Li _{1 + x} (Fe _0.4 Mn _0.4 Co _0.2 ) _1-x O ₂ can be used. . Among these, LiMn ₂ O ₄ , LiCoO ₂ , LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.8 Co _0.2 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ is preferred. In order to increase the output, it is preferable to use a material having a high potential of 4 V or more as the positive electrode material. Examples of the material having a high potential include LiCoO ₂ (4.2 V), LiCr _x Mn _2−x O ₄ (0 <x <0.5) (4.2 V), LiCr _0.2 Ni _0.4 Mn _1.4 O ₄ ( 4.7V), LiNi _0.5 Mn _1.5 O ₄ (4.7V), LiCoPO ₄ (4.8V), LiNiPO ₄ (5.1V), LiNi _1/3 Mn _1/3 Co _1/3 O ₂ (4. 2V), LiNi _0.8 Co _0.15 Al _0.05 O ₂ (4.2 V), and the like.

  The positive electrode active material is preferably in the form of powder (granular), and preferably has a particle diameter of 10 nm or more and 500 μm or less. The particle diameter is more preferably 20 nm or more and 100 μm or less, further preferably 50 nm or more and 50 μm or less, particularly preferably 100 nm or more and 30 μm or less, and further preferably 10 μm or less. Here, the average particle diameter is a value of a volume average particle diameter measured by a laser diffraction particle size distribution measuring apparatus. The nominal value of the seller may be referred to.

  The negative electrode is not particularly limited, and any known negative electrode used in a lithium ion secondary battery can be used. Specifically, a negative electrode current collector, a negative electrode active material, a conductive agent, a binder, and the like Those composed of are preferably used. These materials are the same for the positive electrode, but are formed by forming a thin coating film, sheet or plate on the negative electrode current collector.

  Examples of the negative electrode current collector include copper, nickel, and stainless steel. As a negative electrode active material, the conventionally well-known negative electrode active material used with a lithium ion secondary battery can be used. Specifically, carbon materials such as natural graphite, artificial graphite, amorphous carbon, coke and mesophase pitch carbon fiber, graphite, amorphous carbon hard carbon, C-Si composite material, lithium-aluminum alloy, lithium -One or more of lithium alloys such as magnesium alloy, lithium-indium alloy, lithium-thallium alloy, lithium-lead alloy, lithium-bismuth alloy, titanium, tin, iron, molybdenum, niobium, vanadium and zinc And metal oxides containing metal sulfides. Among these, metallic lithium and carbon materials that can occlude and release alkali metal ions are more preferable.

  As the conductive agent, carbon black such as acetylene black and ketjen black, natural graphite, thermally expanded graphite, carbon fiber, metal fiber such as ruthenium oxide, titanium oxide, aluminum, and nickel are preferable. These can use 1 type (s) or 2 or more types. Among these, acetylene black and ketjen black are more preferable in that the conductivity can be effectively improved with a small amount. Although the compounding quantity of a electrically conductive agent changes also with the kind of active material to be used, it is preferable to set it as 1 mass part-10 mass parts with respect to 100 mass parts of a positive electrode or a negative electrode active material, and 3 mass parts-5 mass parts. It is more preferable that

  As the binder substance, polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, fluoroolefin copolymer crosslinked polymer, polyvinyl alcohol, polyacrylic acid, polyimide, petroleum pitch, coal pitch, phenol resin, and the like are suitable. These can use 1 type (s) or 2 or more types. The blending amount of the binder material varies depending on the type of the active material to be used, but is preferably 0.5 parts by mass to 10 parts by mass with respect to 100 parts by mass of the positive electrode or the negative electrode active material. More preferably, it is 5 parts by mass.

  As a method for forming the positive electrode and the negative electrode, for example, (1) a binder material is added and mixed in a mixture of an electrode active material of a positive electrode or a negative electrode and acetylene black as a conductive agent, and then applied onto each current collector. And (2) a method in which an electrode active material and a binder material are mixed and molded, integrated with a current collector, and then heat-treated in an inert atmosphere to form an electrode as a sintered body. It is. In addition, when using the activated carbon fiber cloth obtained by activating a carbon fiber cloth, you may use as an electrode as it is, without using a binder substance.

  In the lithium ion secondary battery of the present invention, the contact between the positive electrode and the negative electrode is achieved by a method in which a separator is sandwiched between the positive electrode and the negative electrode, or a method in which each electrode is opposed to each other with a gap using a holding means. It is preferable to prevent short circuit.

  As the separator, it is preferable to use a porous thin film that does not cause a chemical reaction with an electrolytic solution or the like in the operating temperature range. As the material of the separator, paper; organic materials such as polyolefin (polypropylene, polyethylene, etc.) and aramid; organic porous materials such as aramid fiber; inorganic materials such as glass fiber; In particular, when an electricity storage device is operated under a high voltage, a high insulating property is required, and therefore a separator made of an inorganic material, a polyolefin material, or a mixture thereof is suitable. From an insulating viewpoint, a polypropylene (PP) film, a polyethylene (PE) film, or a laminated film in which these films are laminated (for example, a PP / PE / PP three-layer film); a polyolefin-based material and an inorganic-based material A molded body of the above mixture; a product obtained by applying or impregnating the organic material to a porous sheet containing cellulose; and the like are suitable as a separator. From the viewpoint of driving under a high voltage, a separator containing polypropylene (PP) is preferable.

  The lithium ion secondary battery of the present invention only needs to have a positive electrode, a negative electrode, and an electrolyte, and may include a plurality of cells each having the positive electrode, the negative electrode, and the electrolyte as one unit. Good. If it has the said structure, the shape of the lithium ion secondary battery of this invention will not be limited, Conventionally well-known shapes, such as a coin type | mold, a winding cylinder type | mold, a lamination | stacking square type | mold, an aluminum lamination type | mold, can be employ | adopted. Moreover, the said exterior case is not specifically limited, What is necessary is just to employ | adopt conventionally well-known things, such as those made from aluminum and steel.

5. Application
The additive for non-aqueous electrolyte of the present invention is added to the non-aqueous electrolyte, and the non-aqueous electrolyte using the additive for non-aqueous electrolyte of the present invention is the above compound (6) to The nonaqueous electrolytic solution of the present invention using (8) as a supporting salt can be used as an electrolytic solution for various power storage devices. Storage devices include primary batteries, lithium (ion) secondary batteries, fuel cells, molten salt batteries, and other batteries having charging and discharging mechanisms, as well as electrolytic capacitors, electric double layer capacitors, lithium ion capacitors, solar cells, etc. Among them, the nonaqueous electrolytic solution of the present invention is effective for improving the performance of a lithium ion secondary battery among these, and is therefore preferably used for a lithium ion secondary battery.

  Next, the present invention will be described in detail with reference to examples and comparative examples. However, the present invention is not limited to these examples, and all modifications may be made without departing from the spirit described above and below. It is included in the technical scope of the present invention.

[NMR measurement]
Using “Unity Plus” (400 MHz) manufactured by Varian, ¹ H-NMR, ¹³ C-NMR, and ¹⁹ F-NMR spectra were measured, and the structure of the sample was analyzed based on the peak intensities of proton, carbon, and fluorine. . ^For the measurement of ¹¹ B-NMR spectrum, “Advanced 400M” (400 MHz) manufactured by Bruker was used.

In addition, the measurement of an NMR spectrum measured the measurement sample which dissolved the reaction solution or the obtained salt so that the density | concentration might be 1 mass%-5 mass% in heavy dimethyl sulfoxide, and the product made from aluminum oxide which does not contain a boron element. It measured in room temperature (25 degreeC) and the frequency | count of integration | stacking 64 times in the NMR tube. In the measurement of ¹ H-NMR and ¹³ C-NMR spectra, tetramethylsilane is used as the standard substance, in the measurement of ¹⁹ F-NMR spectrum, trifluoromethylbenzene is used as the standard substance, and in the measurement of ¹¹ B-NMR spectrum. 1-ethyl-3-methylimidazolium tetrafluoroborane was quantified as a calibration standard.

Synthesis Example 1 Synthesis of Lithium Cyano (fluoro) oxalatoborate LiB (CN) (F) (OC (O) C (O) O)
The structural formula is shown below.

  To a 200 mL three-necked flask equipped with a stirrer, 7.19 g (50.0 mmol) of lithium difluorooxalatoborate (lithium difluorooxalylborate) was added to Chemistry-A European Journal 2009, 15 , 10, p2270-p2272), and the inside of the flask was replaced with nitrogen gas. To this, 50 mL of isobutyronitrile was added, and 9.3 mL (75.0 mmol, 1.5 equivalents relative to the boron compound) of trimethylsilylcyanide was added dropwise at room temperature while stirring the resulting mixed solution. After that, the reaction solution was heated to 80 ° C. with an oil bath, and stirring was continued at this temperature for 2.5 hours to cause reaction.

Then, the organic solvent was distilled off from the obtained yellow solution under reduced pressure and concentrated, followed by reprecipitation with acetonitrile / toluene co-solvent (volume ratio 1/2) to obtain a pale yellow solid (lithium cyano (fluoro) oxalato). Borate). (Yield: 4.03 g (26.7 mmol), yield: 54%).
¹⁹ F-NMR (d6-DMSO) δ-143.8 (q, J = 30.8 Hz)
¹¹ B-NMR (d6-DMSO) δ-0.37 (d, J = 30.8 Hz)

Synthesis Example 2 Synthesis of lithium dicyanooxalatoborate LiB (CN) ₂ (OC (O) C (O) O)
The structural formula is shown below.

  Lithium difluorooxalatoborate (lithium difluorooxalylborate) 5.75 g (40.0 mmol) was added to a 200 mL three-necked flask equipped with a stirrer, and the inside of the flask was replaced with nitrogen gas. To this, 40 mL of valeronitrile was added. While stirring the obtained mixed solution, 14.9 mL (120.1 mmol, 3.0 equivalents relative to the boron compound) of trimethylsilylcyanide was added dropwise at room temperature (25 ° C.). Thereafter, the reaction solution was heated to 120 ° C. with an oil bath, and stirred at the same temperature for 6 hours to be reacted.

Then, the organic solvent was distilled off from the obtained yellow solution under reduced pressure and concentrated, and silica gel column purification (column solvent: acetonitrile / toluene) was performed to obtain a light yellow solid (lithium dicyanooxalatoborate). (Yield: 3.14 g (19.9 mmol), yield: 50%). ¹¹ B-NMR (d6-DMSO) δ-6.9 (s)

<Preparation of non-aqueous electrolyte>
Electrolyte lithium hexafluorophosphate (LiPF ₆ , manufactured by Kishida Chemical Co., Ltd.) is dissolved in a non-aqueous solvent ethylene carbonate (EC) / ethyl methyl carbonate (EMC) in a mixed solvent of EC3: EMC7, A 1.0 mol / L non-aqueous electrolyte A was prepared. Thereafter, non-aqueous electrolyte B in which lithium cyano (fluoro) oxalatoborate (LiBFCN (C ₂ O ₄ )) obtained in the above synthesis example was added to non-aqueous electrolyte A so as to be 2% by mass. And non-aqueous electrolyte D added to 0.08 mass% and lithium dicyanooxalatoborate (LiB (CN) ₂ (C ₂ O ₄ )) to 2 mass% A nonaqueous electrolytic solution E added to be 0.08% by mass with liquid C was prepared.

<Production of coin-type lithium battery>
A commercially available ternary positive electrode sheet (positive electrode active material: LNMC, 2.0 mAh / cm ² ) and a commercially available negative electrode sheet (negative electrode active material: graphite, 2.4 mAh / cm ² ) were punched into a circle. A polyethylene separator was also punched into a circle. CR2032 coin-type battery parts purchased from Hosen Co., Ltd. (positive electrode case (Al clad-treated product), negative electrode sealant cap (manufactured by SUS316L), spacer (1 mm thickness, manufactured by SUS316L), wave washer (manufactured by SUS316L), gasket ( (Made of polypropylene)), a negative cap with a gasket, a wave washer, a spacer, a negative electrode (installed so that the copper foil side of the negative electrode faces the spacer) A was impregnated on the separator. Further, a positive electrode was placed so that the positive electrode mixture was opposed to the negative electrode mixture, and a positive electrode case was sequentially stacked on the positive electrode mixture, followed by caulking to produce a coin-type lithium battery. For the non-aqueous electrolyte B and the non-aqueous electrolyte C, coin-type lithium batteries were respectively produced in the same manner.

<Production of laminated lithium battery>
A commercially available ternary positive electrode sheet (positive electrode active material: LNMC, 2.0 mAh / cm ² ) and a commercially available negative electrode sheet (negative electrode active material: graphite, 2.4 mAh / cm ² ) are laminated to face each other. Then, a polyethylene separator was sandwiched between them. The laminate was sandwiched between two aluminum laminate films (polyethylene resin layer / aluminum layer / polyethylene resin layer), filled with each of the non-aqueous electrolytes A, D, and E, and then sealed in a vacuum state.

<Cycle characteristic test>
2. For each lithium battery using the non-aqueous electrolytes A to E, a charge / discharge rate of 1.0 C (constant current mode) is used using a charge / discharge test apparatus (manufactured by Instrument Center or Asuka Electronics Co., Ltd.). A cycle test was conducted at 0 to 4.4 V with a charge / discharge pause time of 10 minutes at each charge / discharge. The results are shown in FIG. 1 and FIG. After the cycle test, internal resistance was measured for nonaqueous electrolytes A, D, and E using an impedance analyzer (1260 type, manufactured by Solartron Co., Ltd.) after discharge under conditions of 10 mV and 1 MHz to 0.01 Hz. did. The results are shown in FIG.

Based on the results shown in FIGS. 1, 2, and ₄ , the book adopting non-aqueous electrolytes B, C, D, and E containing LiBFCN (C ₂ O ₄ ) and LiB (CN) ₂ (C ₂ O ₄ ) as additives. It was found that the lithium battery of the invention exhibited good cycle characteristics, as compared with the example employing the non-aqueous electrolyte A containing only LiPF ₆ as the electrolyte, the deterioration of the discharge capacity and the increase of the internal resistance were suppressed. .

<High temperature storage test>
About each coin type lithium battery using non-aqueous electrolytes A to C, using the above-described charge / discharge test apparatus, charge at 25 ° C. with a charge rate of 0.2 C (constant current constant voltage mode) to 4.4 V. The battery was discharged to 3.0 V at a discharge rate of 0.2 C (constant current mode). The discharge capacity at this time was defined as the initial discharge capacity (A). Each coin-type lithium battery was charged at 25 ° C. with a charging speed of 0.2 C (constant current constant voltage mode) to 4.4 V, and stored at 60 ° C. for 1 week after charging. Thereafter, the battery was discharged to a discharge rate of 0.2 C (constant current mode) and a 3.0 V cut. Let the discharge capacity at this time be the discharge capacity (B) after high-temperature storage. The capacity retention rate after high-temperature storage was calculated from the following formula, and the results are shown in Table 2.
Storage capacity retention rate = discharge capacity after high temperature storage (B) / initial discharge capacity (A) × 100

From the results shown in Table 2, the coin-type lithium battery of the present invention using the non-aqueous electrolytes B and C containing LiBFCN (C ₂ O ₄ ) or LiB (CN) ₂ (C ₂ O ₄ ) as an additive, It was found that the storage capacity retention rate was improved as compared with the example in which the non-aqueous electrolyte A containing only LiPF ₆ was used as the electrolyte.

Reference example <Preparation of non-aqueous electrolyte>
A non-aqueous electrolyte F was prepared by adding lithium tetracyanoborate (LiB (CN) ₄ ) to the non-aqueous electrolyte A so as to be 0.08% by mass.

<Production of laminated lithium battery>
A commercially available ternary positive electrode sheet (positive electrode active material: LNMC, 2.0 mAh / cm ² ) and a commercially available negative electrode sheet (negative electrode active material: graphite, 2.4 mAh / cm ² ) are laminated to face each other. Then, a polyethylene separator was sandwiched between them. The laminate was sandwiched between two aluminum laminate films (polyethylene resin layer / aluminum layer / polyethylene resin layer), filled with the non-aqueous electrolytes A and F, and sealed in a vacuum state.

<Cycle characteristic test>
About each lithium battery using the non-aqueous electrolyte A and F, charge / discharge rate 1.0C (constant current mode) and 3.0-4.4V using a charge / discharge test apparatus (made by Asuka Electronics Co., Ltd.). A cycle test was conducted by providing a charge / discharge pause time of 10 minutes during each charge / discharge. The results are shown in FIG. Moreover, the internal resistance was measured on the conditions of 10 mV and 1 MHz-0.01 Hz using the impedance analyzer (1260 type | mold, Solartron Co., Ltd.) after completion | finish of a cycle test. The results are shown in FIG.

  The additive for non-aqueous electrolyte of the present invention is added to the non-aqueous electrolyte. The non-aqueous electrolyte using the additive for non-aqueous electrolyte of the present invention can be used as an electrolyte for various power storage devices. Storage devices include primary batteries, lithium (ion) secondary batteries, fuel cells, molten salt batteries, and other batteries having charging and discharging mechanisms, as well as electrolytic capacitors, electric double layer capacitors, lithium ion capacitors, solar cells, etc. Among them, the nonaqueous electrolytic solution of the present invention is effective for improving the performance of a lithium (ion) secondary battery among them, and is therefore preferably used for a lithium secondary battery.

Claims (7)

A non-aqueous electrolyte additive comprising a cyanoborate compound represented by the general formula (1).
(In formula (1), M ^{m +} represents a proton, monovalent, divalent, or trivalent organic or inorganic cation, and Y represents the number of carbon atoms in the main chain that may have H, halogen, or halogen. 1 to 10 hydrocarbon group, cyano group, —C (O) R ¹⁴ , —S (O) ₁ R ¹⁴ , —Z (R ¹⁴ ) ₂ or —XR ¹⁴ , wherein R ¹⁴ represents H, halogen or The main chain represents an organic substituent having 1 to 10 atoms, Z represents N or P, X represents O or S, l represents an integer of 1 to 2, and m represents an integer of 1 to 3. And n represents an integer of 0 to 10.)   Y in the formula (1) is a substituent selected from the group consisting of halogen, a hydrocarbon group having 1 to 10 carbon atoms in the main chain which may have halogen, and a cyano group. The additive for non-aqueous electrolyte described.   The additive for non-aqueous electrolyte according to claim 1 or 2, which is used for a lithium secondary battery.   A nonaqueous electrolytic solution comprising the additive for a nonaqueous electrolytic solution according to any one of claims 1 to 3, a supporting salt, and a solvent. The supporting salt is
Formula (6): M′N (R ¹⁵ SO ₂ ) (R ¹⁶ SO ₂ )
Formula (7): M′PF _a (C _b F _{2b + 1} ) _6-a (0 ≦ a ≦ 6, 1 ≦ b ≦ 2),
General formula (8): M′BF _c (C _d F _{2d + 1} ) _4-c (0 ≦ c ≦ 4, 1 ≦ d ≦ 2), and (in the above general formulas (6) to (8), M 'Represents an alkali metal ion, and R ¹⁵ and R ¹⁶ in the general formula (6) each independently represents a fluorine atom or a fluoroalkyl group having 1 to 6 carbon atoms.) The nonaqueous electrolytic solution according to claim 4, comprising at least one compound selected from the group consisting of compounds.   The lithium secondary battery using the non-aqueous electrolyte containing the additive for non-aqueous electrolytes in any one of Claims 1-3.   A lithium secondary battery using the non-aqueous electrolyte according to claim 4.