JP2013069512A - Nonaqueous electrolytic solution, lithium ion secondary battery, and module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution excellent in high-temperature storage characteristics and high-voltage cycle characteristics.SOLUTION: The nonaqueous electrolytic solution contains a nonaqueous solvent and an electrolyte salt, and the nonaqueous solvent contains at least one kind of hydrofluoric acid addition salt of an amine selected from the group consisting of compounds represented by the formula (1), where R, R, and Rare identical or different, and they represent H or a C1-C4 alkyl group, and n is in the range of 1 to 10, compounds represented by the formula (2), where Rrepresents a C3-C5 saturated or unsaturated nitrogen-containing heterocycle including -N= or -NH-, and n is in the range of 1 to 10, and the like.

Description

The present invention relates to a non-aqueous electrolyte, a lithium ion secondary battery, and a module.

With the recent reduction in weight and size of electrical products, development of lithium-ion secondary batteries having high energy density is in progress. Further, as the application field of lithium ion secondary batteries expands, improvement of battery characteristics is desired. In particular, when lithium ion secondary batteries are used in vehicles, safety and battery characteristics will become increasingly important.

However, the lithium ion secondary battery is not sufficient for safety such as when the battery is overcharged, when it is internally short-circuited, and when it is pierced with a nail, etc. Furthermore, it is necessary to make the battery highly safe. In addition, in the case of in-vehicle use, it is necessary to further increase the voltage used at present in order to increase the capacity.

As a method for improving the safety and increasing the voltage of a non-aqueous electrolyte secondary battery, it has been proposed to use a fluorinated ether having a specific structure (see, for example, Patent Document 1). However, the non-aqueous electrolyte secondary battery of Patent Document 1 has a problem in that the discharge capacity decreases when the battery is left in a high temperature environment or repeatedly charged and discharged.

As a method for improving the cycle characteristics of a lithium ion secondary battery, it has been proposed that the alcohol content in the electrolytic solution be less than 50 ppm (see, for example, Patent Document 2).

Japanese Patent No. 3,807,459 JP-A-10-270076

The present invention provides a non-aqueous electrolyte that can provide a secondary battery having excellent storage characteristics at high temperatures and high voltage cycle characteristics, a lithium ion secondary battery using the non-aqueous electrolyte, and a module using the non-aqueous electrolyte. Let it be an issue.

Patent Document 2 discloses that HF and fluorinated electrolytes react gradually with diols or monoalcohols contained in a high dielectric constant solvent such as ethylene carbonate or a low viscosity solvent such as dimethyl carbonate at room temperature. It is described that the HF in the electrolytic solution is increased with the passage of time, thereby reducing the cycle characteristics of the battery.
However, as a result of various studies by the present inventors to solve the above-mentioned problems, a very small amount of HF is generated by using a non-aqueous electrolytic solution containing a specific amine hydrofluoric acid addition salt. It has been found that the above problems can be solved, and the present invention has been completed.

（式中、Ｒ^１、Ｒ^２およびＲ^３は同じか又は異なり、いずれもＨ又は炭素数１〜４のアルキル基；ｎは１〜１０）で示される化合物、
式（２）：

（式中、Ｒ^４は−Ｎ＝又は−ＮＨ−を含む炭素数３〜５の飽和又は不飽和の含窒素複素環；ｎは１〜１０）で示される化合物、及び、
式（３）：

（式中、Ｒ^４は−Ｎ＝又は−ＮＨ−を含む炭素数３〜５の飽和又は不飽和の含窒素複素環；ｎは１〜１０；ｍは１〜２０）で示される化合物からなる群より選択される少なくとも１種のアミンフッ酸付加塩を含むことを特徴とする非水電解液である。 That is, the present invention is a nonaqueous electrolytic solution containing a nonaqueous solvent and an electrolyte salt, wherein the nonaqueous solvent has the formula (1):

(Wherein R ¹ , R ² and R ³ are the same or different and all are H or an alkyl group having 1 to 4 carbon atoms; n is 1 to 10),
Formula (2):

(Wherein R ⁴ is a saturated or unsaturated nitrogen-containing heterocyclic ring having 3 to 5 carbon atoms including —N═ or —NH—; n is 1 to 10), and
Formula (3):

(Wherein R ⁴ is a saturated or unsaturated nitrogen-containing heterocycle having 3 to 5 carbon atoms including —N═ or —NH—; n is 1 to 10; m is 1 to 20). A non-aqueous electrolyte comprising at least one amine hydrofluoric acid addition salt selected from the group.

The non-aqueous solvent preferably further contains a non-fluorinated cyclic carbonate and a non-fluorinated chain carbonate.

The non-fluorinated cyclic carbonate is preferably at least one compound selected from the group consisting of ethylene carbonate, propylene carbonate, and butylene carbonate.

The non-fluorinated chain carbonate is at least one compound selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, and ethyl butyl carbonate. Is preferred.

The electrolyte salts include LiPF ₆ , LiBF ₄ , LiNSO ₃ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , lithium difluoro (oxalate) borate, lithium bis (oxalate) borate, and And selected from the group consisting of salts represented by the formula: LiPF _a (C _n F _{2n + 1} ) _6-a (wherein, a is an integer from 0 to 5 and n is an integer from 1 to 6). Preferably, it is at least one lithium salt.

The nonaqueous electrolytic solution of the present invention preferably contains 0.5 to 70 ppm of hydrofluoric acid.

The non-aqueous solvent further includes at least one compound selected from the group consisting of unsaturated cyclic carbonates, fluorinated cyclic carbonates, and cyclic sulfonic acid compounds, and the content thereof is 0.1 to 10% by mass. Is preferred.

This invention is also a lithium ion secondary battery provided with the said non-aqueous electrolyte.

The present invention is also a module including the lithium ion secondary battery.

The present invention can provide a non-aqueous electrolyte that can provide a lithium ion secondary battery that is excellent in retention characteristics at high temperatures and high voltage cycle characteristics.

The present invention is a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt,
The non-aqueous solvent has the formula (1):

（式中、Ｒ^１、Ｒ^２およびＲ^３は同じか又は異なり、いずれもＨ又は炭素数１〜４のアルキル基；ｎは１〜１０）で示される化合物、
式（２）：

（式中、Ｒ^４は−Ｎ＝又は−ＮＨ−を含む炭素数３〜５の飽和又は不飽和の含窒素複素環；ｎは１〜１０）
で示される化合物、及び、
式（３）：

（式中、Ｒ^４は−Ｎ＝又は−ＮＨ−を含む炭素数３〜５の飽和又は不飽和の含窒素複素環；ｎは１〜１０；ｍは１〜２０）
で示される化合物からなる群より選択される少なくとも１種のアミンフッ酸付加塩を含むことを特徴とする非水電解液である。
以下に、本発明を詳述する。

(Wherein R ¹ , R ² and R ³ are the same or different and all are H or an alkyl group having 1 to 4 carbon atoms; n is 1 to 10),
Formula (2):

(In the formula, R ⁴ is a saturated or unsaturated nitrogen-containing heterocycle having 3 to 5 carbon atoms including —N═ or —NH—; n is 1 to 10)
And a compound represented by
Formula (3):

(Wherein R ⁴ is a saturated or unsaturated nitrogen-containing heterocycle having 3 to 5 carbon atoms including —N═ or —NH—; n is 1 to 10; m is 1 to 20)
A nonaqueous electrolytic solution comprising at least one amine hydrofluoric acid addition salt selected from the group consisting of compounds represented by:
The present invention is described in detail below.

The non-aqueous electrolyte of the present invention contains a non-aqueous solvent and an electrolyte salt, and the non-aqueous solvent is selected from the group consisting of the compounds represented by the general formulas (1), (2) and (3). Containing at least one amine hydrofluoric acid addition salt. By containing such a specific amine hydrofluoric acid addition salt, it can be set as the electrolyte solution for secondary batteries excellent in the retention characteristic at high temperature and the high voltage cycling characteristic.

The molar ratio n of hydrofluoric acid to amine in the amine hydrofluoric acid addition salt is 1-10. If n is less than 1, the effect of the present invention may not be exhibited, and if it exceeds 10, the battery characteristics may be impaired. From the viewpoint of obtaining an electrolytic solution for a secondary battery excellent in high temperature retention characteristics and high voltage cycle characteristics, n is preferably in the range of 1 to 3, and more preferably in the range of 1 to 2.5.

The compound represented by the formula (1) is preferable because it can be produced at a low cost and can be produced by selecting a value of n. In Formula (1), n is 1-10. From the point which does not impair a battery characteristic, Preferably it is 1-5, More preferably, it is 1-3.

Examples of the compound represented by the formula (1) include trimethylamine n hydrofluoric acid addition salt, triethylamine n hydrofluoric acid addition salt, tripropylamine n hydrofluoric acid addition salt, triisopropylamine n hydrofluoric acid addition salt, tributylamine n hydrofluoric acid addition salt. Salt, triisobutylamine n hydrofluoric acid addition salt, tri t-butylamine n hydrofluoric acid addition salt, dimethylamine n hydrofluoric acid addition salt, diethylamine n hydrofluoric acid addition salt, dipropylamine n hydrofluoric acid addition salt, diisopropylamine n hydrofluoric acid Addition salt, dibutylamine n hydrofluoric acid addition salt, diisobutylamine n hydrofluoric acid addition salt, di-t-butylamine n hydrofluoric acid addition salt, methylamine n hydrofluoric acid addition salt, ethylamine n hydrofluoric acid addition salt, propylamine n hydrofluoric acid addition Salt, isopropylamine n hydrofluoric acid addition salt, butylamine n hydrofluoric acid addition salt, isobutylamine n Tsu acid addition salts, such as t- butylamine n hydrofluoric acid addition salt (n 1 to 10) and the like. In particular, compounds having n in the range of 1 to 3 among these exemplified compounds are preferable from the viewpoint of excellent retention characteristics at high temperatures and high voltage cycle characteristics.

The compound represented by Formula (2) is preferable from the viewpoint of high compound stability. In Formula (2), n is 1-10. N is preferably 1 to 5, more preferably 1 to 3, from the viewpoint of excellent retention characteristics at high temperatures and high voltage cycle characteristics.

Examples of the compound represented by the formula (2) include the following.

Further, from the viewpoint of high stability of the compound, among the compounds represented by the formula (2), those having a nitrogen-containing heterocyclic ring having 4 to 5 carbon atoms are preferable. Also preferred are unsaturated nitrogen-containing heterocycles. The specific compound is more preferably at least one selected from the group consisting of pyridine n hydrofluoric acid addition salt, pyrrole n hydrofluoric acid addition salt, piperidine n hydrofluoric acid addition salt, and pyrrolidine n hydrofluoric acid addition salt.

The compound represented by Formula (3) is preferable from the viewpoint of high compound stability. In Formula (3), n is 1-10. It is preferably 1 to 5, more preferably 1 to 3, from the viewpoint of excellent retention characteristics at high temperatures and high voltage cycle characteristics.

Examples of the compound represented by the formula (3) include the following.

（式中、ｎ及びｍは、前記と同じ）

(Wherein n and m are the same as above)

Further, from the viewpoint of high stability of the compound, among the compounds represented by the formula (3), those having a nitrogen-containing heterocycle having 4 to 5 carbon atoms are preferable. Also preferred are unsaturated nitrogen-containing heterocycles. The specific compound is at least one selected from the group consisting of polyvinylpyridine n hydrofluoric acid addition salt, polyvinylpyrrole n hydrofluoric acid addition salt, polyvinylpiperidine n hydrofluoric acid addition salt, and polyvinylpyrrolidine n hydrofluoric acid addition salt. Is more preferable.

Among these, a compound having n of 1 to 3 is particularly preferable because it can be used as an electrolytic solution for a secondary battery excellent in high temperature retention characteristics and high voltage cycle characteristics.

The molar ratio n of hydrofluoric acid to amine in the hydrofluoric acid addition salt of amine (hereinafter sometimes referred to as “hydrofluoric acid molar ratio n”) can be adjusted, for example, by the following method.

(I) Mixing two or more amine hydrofluoric acid addition salts different in n.
For example, 1 mol of a hydrofluoric acid addition salt of an amine with n = 3 and 1 mol of a hydrofluoric acid addition salt of an amine with n = 1 are mixed to obtain a hydrofluoric acid of an amine with n = 2 [= (3 × 1 + 1 × 1) / 2]. Let acid addition salt.

(Ii) Add amine to the hydrofluoric acid addition salt of amine.
For example, 1 mol of an amine hydrofluoric acid addition salt of n = 3 and 1 mol of an amine are mixed to obtain an amine hydrofluoric acid addition salt of n = 1.5 [= (3 × 1) / 2].

The amine used in combination with the amine hydrofluoric acid addition salt may be the same as or different from the amine constituting the amine hydrofluoric acid addition salt, but the same is preferable from the viewpoint of excellent retention characteristics at high temperatures and high voltage cycle characteristics.

Specific examples of the amine to be used in combination include the amine moiety compounds exemplified in the above-mentioned amine hydrofluoric acid addition salt.

In addition, the amine hydrofluoric acid addition salt and the amine may be mixed with the amine hydrofluoric acid addition salt and the amine in advance and then added to the non-aqueous solvent, or after adding one of them to the non-aqueous solvent, the other is added. May be.

(Iii) The amount of hydrofluoric acid mixed with the amine is adjusted.
For example, 2 mol of hydrofluoric acid is mixed with a solution obtained by dissolving 1 mol of amine in an organic solvent to prepare a hydrofluoric acid addition salt of n = 2 amine in situ.

The content of the amine hydrofluoric acid addition salt is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / kg in terms of mol of HF in the non-aqueous solvent. More preferably, it is 1 * 10 < ^-5 > ^-1 * 10 < ^-3 > mol / kg. If the content of the amine hydrofluoric acid addition salt is too small, the effects of the present invention may not be exhibited. If the content is too large, battery characteristics may be impaired.

The non-aqueous solvent preferably further contains a non-fluorinated cyclic carbonate and a non-fluorinated chain carbonate. By further containing these carbonates, battery characteristics can be improved.

Examples of the non-fluorinated cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, vinyl ethylene carbonate, and the like.

Among these, the non-fluorinated cyclic carbonate is at least one compound selected from the group consisting of ethylene carbonate, propylene carbonate, and butylene carbonate in that the dielectric constant is high and the viscosity is suitable. Is preferred.
As said non-fluorinated cyclic carbonate, 1 type of the compound mentioned above may be used, and 2 or more types may be used together.

Examples of the non-fluorinated chain carbonate include CH ₃ OCOOCH ₃ (dimethyl carbonate: DMC), CH ₃ CH ₂ OCOOCH ₂ CH ₃ (diethyl carbonate: DEC), CH ₃ CH ₂ OCOOCH ₃ (ethyl methyl carbonate: EMC). ), CH ₃ OCOOCH ₂ CH ₂ CH ₃ (methylpropyl carbonate), methyl butyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, and other hydrocarbon-based chain carbonates.

Among these, as the non-fluorinated chain carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl butyl carbonate, ethyl are high in boiling point, low viscosity, and good low temperature characteristics. It is preferably at least one compound selected from the group consisting of propyl carbonate and ethyl butyl carbonate.
As said non-fluorinated chain carbonate, 1 type of the compound mentioned above may be used, and 2 or more types may be used together.

The content of the non-fluorinated cyclic carbonate and non-fluorinated chain carbonate is a total amount, and is preferably 50 to 90% by volume in the non-aqueous solvent. If the content is too small, battery characteristics may be impaired. The content is more preferably 60 to 90% by volume.

The content ratio of the non-fluorinated cyclic carbonate to the non-fluorinated chain carbonate (non-fluorinated cyclic carbonate / non-fluorinated chain carbonate) is preferably 1/15 to 2/1 in volume ratio.
If the proportion of the non-fluorinated cyclic carbonate is too small, the dielectric constant of the entire solvent is lowered, and battery characteristics may be impaired.

In the non-aqueous electrolyte solution of the present invention, the content of the amine hydrofluoric acid addition salt, non-fluorinated cyclic carbonate and non-fluorinated chain carbonate is 20 to 90% by mass in the non-aqueous electrolyte solution in a total amount. Preferably, it is 50-90 mass%.

The nonaqueous electrolytic solution of the present invention contains an electrolyte salt.
As the electrolyte salt, any salt that can be used for an electrolytic solution for a secondary battery can be used, and among them, a lithium salt is preferable.
Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiPF ₆ and LiBF ₄ ; LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF _{3 SO 2) (C 4 F} 9 SO 2), LiC (CF 3 SO 2) 3, LiPF 4 (CF 3) 2, LiPF 4 (C 2 F 5) 2, LiPF 4 (CF 3 SO 2) 2, LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) _2, lithium difluoro (oxalato) borate [LiFOB], lithium bis (oxalato) borate [LiBOB], _{wherein: LiPF a (C n F 2n} + 1 _{6-a (wherein,} a is an integer of 0 to 5, n is an is an integer from 1 to 6) include fluorine-containing organic lithium salts such as salt represented by. These can be used alone or in combination of two or more.

Among these, the lithium salt is capable of suppressing deterioration after the non-aqueous electrolyte is stored at a high temperature, so that LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN ( C ₂ F ₅ SO ₂ ) ₂ , lithium difluoro (oxalate) borate, lithium bis (oxalate) borate, and formula: LiPF _a (C _n F _{2n + 1} ) _{6-a where} a is an integer of 0-5. And n is an integer of 1 to 6, and is preferably at least one selected from the group consisting of salts represented by:

As the salt represented by the formula: LiPF _a (C _n F _{2n + 1} ) _6-a , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (C ₃ F ₇ ) ₃ , LiPF ₃ (C ₄ F ₉ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (C ₃ F ₇ ) ₂ , LiPF ₄ (C ₄ F ₉ ) ₂ The alkyl group represented by C ₃ F ₇ and C ₄ F ₉ in the chain may be either a straight chain or a branched structure.

The concentration of the electrolyte salt in the nonaqueous electrolytic solution is preferably 0.5 to 3 mol / liter. Outside this range, the electrical conductivity of the electrolytic solution tends to be low, and the battery performance tends to deteriorate.
The concentration of the electrolyte salt is more preferably 0.9 mol / liter or more, and more preferably 1.5 mol / liter or less.

The nonaqueous electrolytic solution of the present invention preferably further contains a polyethylene oxide having a weight average molecular weight of 2000 to 4000 and having —OH, —OCOOH, or —COOH at the terminal.
By containing such a compound, the stability of the electrode interface can be improved and the battery characteristics can be improved.

Examples of the polyethylene oxide include polyethylene oxide monool, polyethylene oxide carboxylic acid, polyethylene oxide diol, polyethylene oxide dicarboxylic acid, polyethylene oxide triol, and polyethylene oxide tricarboxylic acid. These may be used alone or in combination of two or more.
Of these, a mixture of polyethylene oxide monool and polyethylene oxide diol, and a mixture of polyethylene carboxylic acid and polyethylene dicarboxylic acid are preferable in terms of better battery characteristics.

If the weight average molecular weight of the polyethylene oxide is too small, it may be easily oxidized and decomposed. The weight average molecular weight is more preferably 3000 to 4000.
The said weight average molecular weight can be measured by polystyrene conversion by the permeation gel chromatography (GPC) method.

The polyethylene oxide content is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / kg in the non-aqueous electrolyte. When there is too much content of the said polyethylene oxide, there exists a possibility that a battery characteristic may be impaired.
The polyethylene oxide content is more preferably 5 × 10 ⁻⁶ mol / kg or more.

The nonaqueous electrolytic solution of the present invention may further contain at least one selected from the group consisting of unsaturated cyclic carbonates, fluorinated cyclic carbonates, and cyclic sulfonic acid compounds. By containing these compounds, deterioration of battery characteristics can be suppressed.

The unsaturated cyclic carbonate is a cyclic carbonate containing an unsaturated bond, and specific examples include vinylene carbonate, 1-methyl vinylene carbonate, 1,2-dimethyl vinylene carbonate, and the like.
The fluorinated cyclic carbonate is a cyclic carbonate to which a fluorine atom is added, and specific examples thereof include fluoroethylene carbonate and difluoroethylene carbonate.
Examples of the cyclic sulfonic acid compound include 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone, and the like.
Especially, it is preferable that the non-aqueous electrolyte of this invention contains a 1, 3- propane sultone and a 1, 4- butane sultone from the point which can improve a high temperature characteristic.

The content of these compounds is preferably 0.1 to 10% by mass in the nonaqueous electrolytic solution, more preferably 1% by mass or more, and more preferably 5% by mass or less.

The non-aqueous electrolyte of the present invention is an incombustible (flame retardant) agent, a surfactant, a high dielectric additive, a cycle characteristic and a rate characteristic improver, or an overcharge prevention as long as the effects of the present invention are not impaired. You may further contain other additives, such as an agent.

Examples of the incombustible (flame retardant) agent include phosphate esters. Examples of the phosphate ester include fluorine-containing alkyl phosphate esters, non-fluorinated alkyl phosphate esters, and aryl phosphate esters. Especially, it is preferable that it is a fluorine-containing alkyl phosphate ester at the point which can exhibit a nonflammable effect in a small quantity.

Specific examples of the fluorine-containing alkyl phosphate ester include fluorine-containing dialkyl phosphate esters described in JP-A No. 11-233141 and cyclic alkyl phosphate esters described in JP-A No. 11-283669. Or fluorine-containing trialkyl phosphate ester etc. are mentioned.

Examples of the flame retardant include (CH ₃ O) ₃ P═O, (CF ₃ CH ₂ O) ₃ P═O, and the like.

The surfactant may be any of a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant. From the viewpoint of good cycle characteristics and rate characteristics, a fluorine atom It is preferable that it contains.

As such a surfactant containing a fluorine atom, for example, the following formula (4):
Rf ¹ COO ⁻ M ⁺ (4)
(In the formula, Rf ¹ is a fluorine-containing alkyl group which may contain an ether bond having 3 to 10 carbon atoms; M ⁺ is Li ⁺ , Na ⁺ , K ⁺ or NHR ′ ₃ ⁺ (R ′ is the same or different; , Each of which is H or an alkyl group having 1 to 3 carbon atoms),
_{^{Rf 2 SO 3 - M + (}} 5)
(In the formula, Rf ² is a fluorine-containing alkyl group which may contain an ether bond having 3 to 10 carbon atoms; M ⁺ is Li ⁺ , Na ⁺ , K ⁺ or NHR ′ ₃ ⁺ (R ′ is the same or different. These are preferably fluorine-containing sulfonates represented by H) or an alkyl group having 1 to 3 carbon atoms.

The content of the surfactant is preferably 0.01 to 2% by mass in the nonaqueous electrolytic solution from the viewpoint that the surface tension of the electrolytic solution can be reduced without reducing the charge / discharge cycle characteristics.

Examples of the high dielectric additive include sulfolane, methyl sulfolane, γ-butyrolactone, γ-valerolactone, acetonitrile, propionitrile and the like.

Examples of the cycle characteristic and rate characteristic improving agent include methyl acetate, ethyl acetate, tetrahydrofuran, 1,4-dioxane and the like.

Examples of the overcharge preventing agent include cyclohexylbenzene, biphenyl, alkylbiphenyl, terphenyl, terphenyl partial hydride, t-butylbenzene, t-amylbenzene, diphenyl ether, benzofuran, dibenzofuran, hexafluorobenzene, and fluorobenzene. Aromatic compounds such as cyclohedichloroaniline and toluene; partially fluorinated products of the aromatic compounds such as 2-fluorobiphenyl; 2,4-difluoroanisole, 2,5-difluoroanisole and 2,6-difluoroanisole And fluorine-containing anisole compounds.
The content of the overcharge inhibitor is preferably 0.1 to 5% by mass in the non-aqueous electrolyte from the viewpoint that the battery can be prevented from being ruptured or ignited in the case of overcharging or the like.

The nonaqueous electrolytic solution of the present invention preferably contains 0.5 to 70 ppm of hydrofluoric acid. By containing hydrofluoric acid, the film formation of the additive can be promoted.
The content of hydrofluoric acid is more preferably 0.5 ppm or more, more preferably 50 ppm or less, and further preferably 30 ppm or less.
The content of hydrofluoric acid can be measured by a neutralization titration method.

The nonaqueous electrolytic solution of the present invention may be prepared by any method using the above-described components.

Thus, the nonaqueous electrolytic solution of the present invention contains a specific amine hydrofluoric acid addition salt. For this reason, the battery excellent in the storage characteristic in high temperature and the high voltage cycling characteristic can be manufactured using the non-aqueous electrolyte of this invention. The nonaqueous electrolytic solution of the present invention can be suitably applied to a battery such as a lithium ion secondary battery.
Below, a lithium ion secondary battery is demonstrated as an example of the battery using the non-aqueous electrolyte of this invention. Such a lithium ion secondary battery provided with the non-aqueous electrolyte of the present invention is also one aspect of the present invention.

The lithium ion secondary battery of the present invention includes a positive electrode, a negative electrode, and the non-aqueous electrolyte described above.

A positive electrode is comprised from the positive electrode mixture containing the positive electrode active material which is a material of a positive electrode, and a collector.

The positive electrode active material is particularly preferably a lithium-containing transition metal composite oxide that produces a high voltage.
Examples of the lithium-containing transition metal composite oxide include:
Formula (6): Li _a Mn _2-b M ¹ _b O ₄ (where 0.9 ≦ a; 0 ≦ b ≦ 1.5; M ¹ is Fe, Co, Ni, Cu, Zn, Al, Sn) , Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge, at least one metal selected from the group consisting of lithium and manganese spinel composite oxides,
Formula (7): LiNi _1-c M ² _c O ₂ (where 0 ≦ c ≦ 0.5; M ² is Fe, Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg) , At least one metal selected from the group consisting of Ca, Sr, B, Ga, In, Si and Ge), or
Formula (8): LiCo _1-d M ³ _d O ₂ (where 0 ≦ d ≦ 0.5; M ³ is Fe, Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg , Ca, Sr, B, Ga, In, Si, and Ge, at least one metal selected from the group consisting of lithium and cobalt composite oxides.

Among them, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ can be provided because the lithium ion secondary battery with high energy density and high output can be provided. Or LiNi _1/3 Co _1/3 Mn _1/3 O ₂ is preferred.

As other positive electrode active materials, LiFePO ₄ , LiNi _0.8 Co _0.2 O ₂ , Li _1.2 Fe _0.4 Mn _0.4 O ₂ , LiNi _0.5 Mn _0.5 O ₂ , LiV ₃ O ₆ etc. are mentioned.

When the lithium ion secondary battery of the present invention is used as a large-sized lithium ion secondary battery for a hybrid vehicle or a distributed power source, high output is required. Therefore, the positive electrode active material particles are mainly secondary particles. It is preferable that
The positive electrode active material particles preferably include 0.5 to 7.0% by volume of fine particles having an average secondary particle size of 40 μm or less and an average primary particle size of 1 μm or less. By containing fine particles having an average primary particle size of 1 μm or less, the contact area with the electrolytic solution is increased, and the diffusion of lithium ions between the electrode and the electrolytic solution can be further accelerated. Output performance can be improved.

The content of the positive electrode active material is preferably 50 to 99% by mass, more preferably 80 to 99% by mass of the positive electrode mixture, in view of high battery capacity.

The positive electrode mixture preferably further contains a binder, a thickener, and a conductive material.
As the above-mentioned binder, any material can be used as long as it is a material that is safe with respect to the solvent and the electrolyte used in the production of the electrode. For example, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene Styrene-butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, and the like.

Examples of the thickener include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein.

Examples of the conductive material include carbon materials such as graphite and carbon black.

Examples of the material for the positive electrode current collector include metals such as aluminum, titanium, and tantalum, and alloys thereof. Of these, aluminum or an alloy thereof is preferable.

The positive electrode may be manufactured by a conventional method. For example, the above-mentioned positive electrode active material is added with the above-mentioned binder, thickener, conductive material, solvent, etc. to form a slurry-like positive electrode mixture, which is applied to a current collector, dried and then pressed. A method of densification is mentioned.

The negative electrode is composed of a negative electrode mixture containing a negative electrode material and a current collector.

As the negative electrode material, carbonaceous materials capable of occluding and releasing lithium such as organic pyrolysates and artificial graphite and natural graphite under various pyrolysis conditions; lithium such as tin oxide and silicon oxide can be occluded and released Metal oxide materials; lithium metal; various lithium alloys and the like. These negative electrode materials may be used in combination of two or more.

As a carbonaceous material capable of occluding and releasing lithium, artificial graphite or purified natural graphite produced by high-temperature treatment of graphitizable pitch obtained from various raw materials, or surface treatment with pitch or other organic substances on these graphites What is obtained by carbonizing after applying is preferred.

The negative electrode mixture preferably further contains a binder, a thickener, and a conductive material.
As said binder, the thing similar to the binder which can be used for a positive electrode mentioned above is mentioned.
As said thickener, the thing similar to the thickener which can be used for a positive electrode mentioned above is mentioned.

Examples of the conductive material for the negative electrode include metal materials such as copper and nickel; carbon materials such as graphite and carbon black.

Examples of the material of the negative electrode current collector include copper, nickel, and stainless steel. Of these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost.

The negative electrode may be manufactured by a conventional method. For example, the above-described negative electrode material is added with the above-mentioned binder, thickener, conductive material, solvent, etc. to form a slurry, which is applied to a current collector, dried, pressed and densified. .

The lithium ion secondary battery of the present invention preferably further includes a separator.
The material and shape of the separator are not particularly limited as long as they are stable to the electrolytic solution and excellent in liquid retention, and known ones can be used.
Especially, it is preferable that the said separator is the porous sheet | seat or nonwoven fabric etc. which use polyolefin, such as polyethylene and a polypropylene, from the point that the permeability of an electrolyte solution and a shutdown effect are favorable.

The shape of the lithium ion secondary battery of the present invention is arbitrary, and examples thereof include a cylindrical shape, a square shape, a laminate shape, a coin shape, and a large shape. In addition, the shape and structure of a positive electrode, a negative electrode, and a separator can be changed and used according to the shape of each battery.

Moreover, the module provided with the lithium ion secondary battery of this invention is also one of this invention.

As described above, when the non-aqueous electrolyte of the present invention is used, a battery excellent in high temperature storage characteristics and high voltage cycle characteristics and a module using the battery can be suitably obtained.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited only to such examples.

Example 1
(Preparation of electrolyte 1)
First, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed so that the volume ratio was EC / EMC = 3/7, using a vertical mixing tank with a stirring blade. LiPF ₆ is added at 1.0 mol / liter, and triethylamine n hydrofluoric acid addition salt (n is 1) is added at 7.5 × 10 ⁻⁴ mol / kg in terms of moles of HF and mixed to obtain a non-aqueous electrolyte. It was. The content of hydrofluoric acid in the obtained nonaqueous electrolytic solution was 15 ppm.

(Production of coin-type battery)
LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , carbon black, and polyvinylidene fluoride (Kureha Chemical Co., Ltd., trade name: KF-7200) were mixed at 92/3/5 (mass% ratio). A positive electrode mixture slurry was prepared by dispersing the positive electrode active material in N-methyl-2-pyrrolidone to form a slurry. The obtained positive electrode mixture slurry is uniformly applied on an aluminum current collector, dried to form a positive electrode mixture layer (thickness 50 μm), and then compression molded by a roller press machine to form a positive electrode laminate. Manufactured. The positive electrode laminate was punched into a diameter of 1.6 mm with a punching machine to produce a circular positive electrode.

Separately, styrene-butadiene rubber dispersed with distilled water was added to artificial graphite powder so as to have a solid content of 6% by mass, and mixed with a disperser to form a slurry. A negative electrode current collector (thickness 10 μm) On the copper foil) and dried to form a negative electrode mixture layer. After that, compression molding was performed with a roller press machine, and a circular negative electrode was produced with a punching machine having a diameter of 1.6 mm.

The above-mentioned circular positive electrode is opposed to the positive electrode and the negative electrode through a microporous polyethylene film (separator) having a thickness of 20 μm, the electrolytic solution is injected, and the electrolytic solution sufficiently permeates the separator, and then sealed. Precharging and aging were performed to produce a coin-type lithium ion secondary battery.

(Measurement of battery characteristics)
The coin-type lithium ion secondary battery was examined for high voltage cycle characteristics and high temperature storage characteristics as follows.

Charge / Discharge Condition Charging: Holds the charge current at 1 / 10C at 0.5C and 4.3V (CC / CV charge)
Discharge: 0.5C 3.0Vcut (CC discharge)

(High voltage cycle characteristics)
Regarding the cycle characteristics, the charge / discharge cycle performed under the above charge / discharge conditions (charging at 1.0 C at a predetermined voltage until the charging current becomes 1/10 C and discharging to 3.0 V at a current equivalent to 1 C) is 1 The discharge capacity after 5 cycles and the discharge capacity after 100 cycles are measured. For the cycle characteristics, the value obtained by the following formula is used as the capacity retention rate. The capacity retention rate was 95%.

(High temperature storage characteristics)
For high-temperature storage characteristics, charge / discharge is performed under the above charge / discharge conditions (charge at 1.0C at a predetermined voltage until the charge current becomes 1 / 10C and discharge to 3.0V at a current equivalent to 1C). The capacity was examined. Then, it charged again on said charging conditions, and preserve | saved for one day in a 85 degreeC thermostat. The battery after storage was discharged at 25 ° C. under the above discharge conditions to a discharge end voltage of 3 V, and the remaining capacity was measured. After further charging under the above charge conditions, the discharge end voltage at a constant current under the above discharge conditions. The recovery capacity was measured by discharging to 3V. The recovery capacity ratio when the discharge capacity before storage was 100 was 96%.

Example 2
First, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed with each other so that the volume ratio was EC / DEC = 3/7, and then LiPF was added thereto. ₆ was added at 1.0 mol / liter, and pyridine n hydrofluoric acid addition salt (n is 1) was added in an amount of 8.0 × 10 ⁻⁴ mol / kg in terms of the number of moles of HF to obtain a non-aqueous electrolyte. The content of hydrofluoric acid in the obtained nonaqueous electrolytic solution was 16 ppm. The capacity retention rate was 94%, and the recovery capacity rate was 95%.

Example 3
First, ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) were mixed in a vertical mixing tank equipped with a stirring blade, and the volume ratio was EC / PC / EMC = 2/1. / 7, LiPF ₆ is 1.0 mol / liter, and polyvinylpyridine n hydrofluoric acid addition salt (n is 1) is 8.0 × 10 ⁻⁴ mol / kg in terms of moles of HF. The mixture was added and mixed to obtain a non-aqueous electrolyte. The content of hydrofluoric acid in the obtained nonaqueous electrolytic solution was 16 ppm.
Using the obtained nonaqueous electrolytic solution, a battery was produced and tested in the same manner as in Example 1. The capacity retention rate was 93%, and the recovery capacity rate was 95%.

Example 4
Using a vertical mixing vessel equipped with a stirring blade, first, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed at a volume ratio of EC / PC / DEC = 2/1 /. 7 to which LiPF ₆ was added at 1.0 mol / liter, and triethylamine n hydrofluoric acid addition salt (n is 1) was added at 7.5 × 10 ⁻⁴ mol / kg in terms of moles of HF. Further, as an additive, a mixture of polyethylene oxide monool and polyethylene oxide diol (mixing ratio 1: 1 (molar ratio), weight average molecular weight 2000) is 2.5 × 10 ⁻⁵ mol / kg, respectively. The mixture was added and mixed to obtain a non-aqueous electrolyte. The content of hydrofluoric acid in the obtained nonaqueous electrolytic solution was 15 ppm.
Using the obtained nonaqueous electrolytic solution, a battery was produced and tested in the same manner as in Example 1. The capacity retention rate was 93% and the recovery capacity rate was 94%.

Comparative Example 1
A battery was produced and tested in the same manner as in Example 1 except that the amine hydrofluoric acid addition salt and the additive were not added. Further, the content of hydrofluoric acid in the non-aqueous electrolyte was 20 ppm. The capacity retention rate was 85%, and the recovery capacity rate was 87%.

The nonaqueous electrolytic solution of the present invention can be suitably applied as an electrolytic solution for lithium ion secondary batteries.

Claims (9)

A non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte salt,
The non-aqueous solvent has the formula (1):

(Wherein R ¹ , R ² and R ³ are the same or different and all are H or an alkyl group having 1 to 4 carbon atoms; n is 1 to 10),
Formula (2):

(In the formula, R ⁴ is a saturated or unsaturated nitrogen-containing heterocycle having 3 to 5 carbon atoms including —N═ or —NH—; n is 1 to 10)
And a compound represented by
Formula (3):

(Wherein R ⁴ is a saturated or unsaturated nitrogen-containing heterocycle having 3 to 5 carbon atoms including —N═ or —NH—; n is 1 to 10; m is 1 to 20)
A nonaqueous electrolytic solution comprising at least one amine hydrofluoric acid addition salt selected from the group consisting of compounds represented by: The nonaqueous electrolytic solution according to claim 1, wherein the nonaqueous solvent further contains a nonfluorinated cyclic carbonate and a nonfluorinated chain carbonate. The nonaqueous electrolytic solution according to claim 2, wherein the non-fluorinated cyclic carbonate is at least one compound selected from the group consisting of ethylene carbonate, propylene carbonate, and butylene carbonate. The non-fluorinated chain carbonate is at least one compound selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, and ethyl butyl carbonate. Item 4. A non-aqueous electrolyte according to item 2 or 3. The electrolyte salts include LiPF ₆ , LiBF ₄ , LiNSO ₃ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , lithium difluoro (oxalate) borate, lithium bis (oxalate) borate, and And selected from the group consisting of salts represented by the formula: LiPF _a (C _n F _{2n + 1} ) _6-a (wherein, a is an integer from 0 to 5 and n is an integer from 1 to 6). The nonaqueous electrolytic solution according to claim 1, 2, 3, or 4, which is at least one lithium salt. The nonaqueous electrolytic solution according to claim 1, containing 0.5 to 70 ppm of hydrofluoric acid. Further comprising at least one compound selected from the group consisting of an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, and a cyclic sulfonic acid compound, and the content thereof is 0.1 to 10% by mass; The nonaqueous electrolytic solution according to 3, 4, 5 or 6. A lithium ion secondary battery comprising the non-aqueous electrolyte according to claim 1, 2, 3, 4, 5, 6 or 7. A module comprising the lithium ion secondary battery according to claim 8.