JP4821161B2 - Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte for a lithium secondary battery and a lithium secondary battery using the non-aqueous electrolyte for a lithium secondary battery. Specifically, the use of a specific non-aqueous solvent suppresses battery deterioration when the battery is used at a high voltage, and also has a high capacity and high energy density lithium secondary that has excellent storage characteristics and cycle characteristics. The present invention relates to a non-aqueous electrolyte for a lithium secondary battery capable of realizing a battery, and a lithium secondary battery using the non-aqueous electrolyte for a lithium secondary battery.

  With the recent reduction in weight and size of electrical products, development of lithium secondary batteries having a high energy density is in progress. In addition, with the expansion of the application field of lithium secondary batteries, improvement of battery characteristics is also demanded.

  As the negative electrode of the lithium secondary battery, metallic lithium, a metallic compound capable of inserting and extracting lithium (metal simple substance, oxide, alloy with lithium, etc.) and a carbonaceous material are used. In particular, as a carbonaceous material, for example, a nonaqueous electrolyte secondary battery using a carbonaceous material capable of inserting and extracting lithium such as coke, artificial graphite, and natural graphite has been proposed. In such a non-aqueous electrolyte secondary battery, since lithium does not exist in a metal state, dendrite formation is suppressed, and battery life and safety can be improved. In particular, non-aqueous electrolyte secondary batteries using graphite-based carbonaceous materials such as artificial graphite and natural graphite are attracting attention as meeting the demand for higher capacity.

  In lithium secondary batteries using the above carbonaceous materials, cyclic carbonates such as propylene carbonate and ethylene carbonate are usually widely used as high dielectric constant solvents for non-aqueous electrolytes, and in particular, non-graphitic carbonaceous materials such as coke. In the non-aqueous electrolyte secondary battery using the material, a solvent containing propylene carbonate is suitably used.

  However, in a non-aqueous electrolyte secondary battery using a graphite-based carbonaceous material alone or mixed with another negative electrode material capable of occluding and releasing lithium as a negative electrode, a solvent containing propylene carbonate is used. When charging, the decomposition reaction of propylene carbonate proceeds vigorously on the electrode surface, making it impossible to smoothly occlude and release lithium into the graphite-based carbonaceous negative electrode.

  On the other hand, since ethylene carbonate has little such decomposition, ethylene carbonate is frequently used as a high dielectric constant solvent for an electrolyte in nonaqueous electrolyte secondary batteries using a graphite-based carbonaceous negative electrode. However, even when ethylene carbonate is used as the main solvent, the electrolyte solution decomposes on the surface of the electrode during the charge / discharge process, resulting in problems such as a decrease in charge / discharge efficiency, a decrease in cycle characteristics, and an increase in battery internal pressure due to gas generation.

  Therefore, electrolytic solutions containing various additives have been proposed in order to improve the characteristics of the nonaqueous electrolytic secondary battery. For example, in order to suppress the decomposition of the electrolyte solution of a non-aqueous electrolyte battery using a graphite-based negative electrode, an electrolyte solution containing vinylene carbonate and its derivative (Patent Document 1) or a non-conjugated unsaturated bond in the side chain An electrolytic solution containing an ethylene carbonate derivative (Patent Document 2) has been proposed. In the electrolytic solution containing these compounds, the compound is reduced and decomposed on the negative electrode surface to form a film, and the excessive decomposition of the electrolytic solution is suppressed by this film.

  However, these compounds are not always satisfactory in terms of storage characteristics in a high temperature environment. In addition, the vinylene carbonate-based compound easily reacts with the positive electrode material in a charged state, and the storage characteristics tend to be further lowered as the addition amount increases.

  Suppressing the oxidation reactivity between vinylene carbonate and derivatives thereof disclosed in Patent Documents 1 and 2 and ethylene carbonate derivatives having a non-conjugated unsaturated bond in the side chain, or the positive electrode material in a charged state with the solvent itself is The improvement of battery characteristics and the suppression of gas generation during storage at high temperatures is realized, and its development is desired.

On the other hand, an electrolytic solution containing an ester derivative having an unsaturated bond as an additive for forming a reductive decomposition film on the negative electrode surface, in place of ethylene carbonate having a non-conjugated unsaturated bond in its side chain or a derivative thereof, or a derivative thereof. (Patent Document 3) has been proposed, and it is disclosed that reductive decomposition of a solvent during charging can be suppressed to a low level even in an electrolyte solution containing these compounds. However, this Patent Document 3 does not describe battery characteristics or gas generation under high temperature conditions and high voltage conditions when these compounds are used.
JP-A-8-45545 Japanese Patent Laid-Open No. 2000-40526 JP 2000-299127 A

  The present invention has been made in view of the above-described conventional situation, suppresses the decomposition of the non-aqueous electrolyte solution, suppresses deterioration when the battery is used at a high voltage, and has high capacity, storage characteristics, and cycle characteristics. An object of the present invention is to provide an excellent lithium secondary battery with high energy density.

As a result of repeating various studies to achieve the above object, the present inventors have used a specific dicarboxylic acid ester compound to add a specific negative electrode film-forming additive to a non-aqueous electrolyte or non-aqueous electrolyte. When added, it has been found that the oxidative decomposition of the additive can be minimized to improve the charge / discharge efficiency and the storage characteristics and cycle characteristics of the lithium secondary battery can be improved, and the present invention has been completed. It was.
That is, the gist of the present invention is as follows.

(1) A nonaqueous electrolytic solution for a lithium secondary battery, comprising a nonaqueous solvent containing a dicarboxylic acid ester compound represented by the following general formula [1] and an electrolyte.
R ¹ (COOR ² ) (COOR ³ ) [1]
(In the formula, R ¹ is a divalent saturated hydrocarbon group having 2 to 20 carbon atoms which may be substituted with a fluorine atom and / or a chlorine atom, and R ² and R ³ are each independently A hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a fluorine atom and / or a chlorine atom and may contain a carbon-carbon unsaturated bond, but at least one of R ² and R ³ Is a hydrocarbon group represented by the following general formula [2].
-CR ⁴ R ⁵ -CR ⁶ = CR ⁷ R ⁸ ... [2]
(Wherein R ^{4 to} R ⁸ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a fluorine atom and / or a chlorine atom, and includes a carbon-carbon unsaturated bond). Or a hydrocarbon group having 1 to 10 carbon atoms, and any two groups of R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be linked to form a ring. .) )

(2 ) The lithium according to (1 ), wherein the dicarboxylic acid ester compound represented by the general formula [1] is contained in the nonaqueous electrolytic solution in a proportion of 0.01 to 10% by weight. Non-aqueous electrolyte for secondary batteries.

( 3 ) The non-aqueous electrolyte for a lithium secondary battery according to (1) or (2) , further comprising a cyclic ester carbonate having a carbon-carbon unsaturated bond.

（式中、Ｒ^９〜Ｒ^１６は、それぞれ独立に、水素原子、フッ素原子、塩素原子、或いはフッ素原子および／または塩素原子で置換されていてもよく、また炭素−炭素不飽和結合を含んでいてもよい、炭素数１〜６の炭化水素基である。） ( 4 ) The nonaqueous system for a lithium secondary battery according to ( 3 ), wherein the cyclic carbonate having a carbon-carbon unsaturated bond is represented by the following general formula [3] or the following general formula [4] Electrolytic solution.

(Wherein R ^{9 to} R ¹⁶ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a fluorine atom and / or a chlorine atom, and includes a carbon-carbon unsaturated bond). It may be a hydrocarbon group having 1 to 6 carbon atoms.)

( 5 ) The cyclic carbonate having a carbon-carbon unsaturated bond is contained in the nonaqueous electrolytic solution in a proportion of 0.01 to 10% by weight, as described in ( 3 ) or ( 4 ) Non-aqueous electrolyte for lithium secondary batteries.

( 6 ) The cyclic carbonate having a carbon-carbon unsaturated bond is vinylene carbonate, 4-methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4-vinyl ethylene carbonate, and 5-methyl-4-vinyl ethylene carbonate. The non-aqueous electrolyte solution for a lithium secondary battery according to any one of ( 3 ) to ( 5 ), wherein the nonaqueous electrolyte solution is one or more selected from the group consisting of:

( 7 ) A lithium secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is a lithium secondary battery according to any one of (1) to ( 6 ) A lithium secondary battery characterized by being a non-aqueous electrolyte solution.

  According to the present invention, when a specific negative electrode film forming additive is added to a non-aqueous electrolyte or a non-aqueous electrolyte by blending a specific dicarboxylic acid ester compound in the non-aqueous electrolyte, the additive The charge / discharge efficiency can be improved by minimizing the oxidative decomposition of the battery, which suppresses the deterioration of the battery when the battery is used at a high voltage, and has a high capacity and excellent storage characteristics and cycle characteristics. A high energy density lithium secondary battery can be realized.

  Although the details of the action and effect of the present invention are not clear, the dicarboxylic acid ester compound represented by the general formula [1] used in the present invention suppresses the oxidative decomposition of the non-aqueous electrolyte during high-temperature storage. This is considered to be due to the improvement in battery characteristics during high-temperature storage.

  Hereinafter, embodiments of the non-aqueous electrolyte for a lithium secondary battery and the lithium secondary battery of the present invention will be described in detail. However, the present invention is not limited to the following description and is within the scope of the gist thereof. It can be implemented with any modification.

[I] Non-aqueous electrolyte for lithium secondary battery First, the non-aqueous electrolyte for lithium secondary battery of the present invention will be described.
The non-aqueous electrolyte for a lithium secondary battery of the present invention contains an electrolyte as a main component and a non-aqueous solvent for dissolving the same as a general non-aqueous electrolyte. It contains at least one dicarboxylic acid ester compound represented by the general formula [1] to be described later (hereinafter sometimes referred to as “specific dicarboxylic acid ester compound”).

[Electrolytes]
There is no restriction | limiting in particular about electrolyte, If it is used as the electrolyte of the target secondary battery, a well-known thing can be used arbitrarily. In the lithium secondary battery of the present invention, a lithium salt is usually used as an electrolyte.

Specific examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , Li ₂ CO ₃ and LiBF ₄ ; LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,3-perfluoropropane disulfonylimide, 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 and the like fluorine-containing organic lithium salt; lithium bis (oxalato) Rate, and the like oxalatoborate salts such as lithium difluoro oxalatoborate is. Among these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiN (C ₂ F ₅ SO ₂ ) ₂ are preferable, and LiPF ₆ or LiBF ₄ is particularly preferable.

Any one of the above lithium salts may be used alone, or two or more of them may be used in any combination and ratio, but a combination of two or more inorganic lithium salts, or an inorganic lithium salt and The combined use with the fluorine-containing organic lithium salt is preferable because gas generation during continuous charging is suppressed or deterioration after high-temperature storage is suppressed. In particular, the combination and the LiPF ₆ and LiBF _4, and an inorganic lithium salt such as _{LiPF 6, LiBF 4, LiCF 3} SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) _2, etc. The combined use with a fluorine-containing organic lithium salt is preferred. When LiPF ₆ and LiBF ₄ are used in combination, it is preferable that LiBF ₄ is usually contained at a ratio of 0.01 wt% or more and 20 wt% or less with respect to the entire lithium salt. When an inorganic lithium salt such as LiPF ₆ or LiBF ₄ and a fluorine-containing organic lithium salt such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , or LiN (C ₂ F ₅ SO ₂ ) ₂ are used in combination, lithium The proportion of the inorganic lithium salt in the total salt is preferably in the range of usually 70% by weight or more and 99% by weight or less.

When the non-aqueous solvent contains γ-butyrolactone in a proportion of 55% by volume or more, it is preferable that LiBF ₄ is contained in a proportion of 40 mol% or more with respect to the entire lithium salt. Among them, LiBF ₄ is contained in a proportion of 40 mol% or more and 95 mol% or less with respect to the entire lithium salt, and the remainder is LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ is more preferably selected from the group consisting of ₂ .

  The concentration of the lithium salt in the non-aqueous electrolyte is usually 0.5 mol / liter or more, preferably 0.6 mol / liter or more, more preferably 0.8 mol / liter or more, and usually 3 mol / liter or less. The range is preferably 2 mol / liter or less, more preferably 1.5 mol / liter or less. If this concentration is too low, the electrical conductivity of the electrolyte is insufficient, and if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, and battery performance may decrease.

[Nonaqueous solvent]
<Nonaqueous solvent other than specific dicarboxylic acid ester compound>
As the non-aqueous solvent, conventionally known solvents can be arbitrarily used as the solvent for the non-aqueous electrolyte solution, but an organic solvent is usually used. Examples of the organic solvent include linear and cyclic carbonates, linear and cyclic carboxylic acid esters, linear and cyclic ethers, and phosphorus-containing organic solvents.

  Examples of the cyclic carbonates include alkylene carbonates having an alkylene group having 2 to 4 carbon atoms such as ethylene carbonate, propylene carbonate, butylene carbonate, and fluoroethylene carbonate. Among these, ethylene carbonate and propylene carbonate are preferable.

  Examples of chain carbonates include dialkyl carbonates having 1 to 4 carbon atoms such as dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methyl n-propyl carbonate, ethyl n-propyl carbonate, and the like. Is mentioned. Among these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable.

  Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone.

  Examples of the chain carboxylic acid esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, and methyl butyrate.

  Examples of cyclic ethers include tetrahydrofuran and 2-methyltetrahydrofuran.

  Examples of the chain ethers include diethoxyethane, dimethoxyethane, dimethoxymethane and the like.

  Examples of the phosphorus-containing organic solvent include trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, and the like.

  Any one of these non-aqueous solvents may be used alone, or two or more thereof may be used in combination with any composition and combination, but it is preferable to use two or more compounds in combination. For example, it is preferable to use a high dielectric constant solvent such as cyclic carbonates or cyclic carboxylic acid esters in combination with a low viscosity solvent such as chain carbonates or chain carboxylic acid esters.

  When the chain carboxylic acid ester is used as a non-aqueous solvent, the proportion of the chain carboxylic acid ester in the non-aqueous solvent is usually 50% by weight or less, preferably 30% by weight or less, more preferably 20% by weight or less. Range. If this upper limit is exceeded, the electrical conductivity may be reduced. Note that the chain carboxylic acid esters are not essential components of the non-aqueous solvent, and the non-aqueous solvent may not contain the chain carboxylic acid esters.

  In the case where cyclic carboxylic acid esters are used as the non-aqueous solvent, the ratio of the cyclic carboxylic acid esters in the non-aqueous solvent is usually 60% by weight or less, preferably 55% by weight or less, more preferably 50% by weight or less. Range. When this upper limit is exceeded, there is a possibility that the liquid injection property is lowered or the output characteristics at a low temperature are deteriorated. Note that the cyclic carboxylic acid esters are not essential components of the non-aqueous solvent, and the non-aqueous solvent may not contain the cyclic carboxylic acid esters.

  Further, when the chain ether is used as the non-aqueous solvent, the proportion of the chain ether in the non-aqueous solvent is usually 60% by weight or less, preferably 40% by weight or less, more preferably 30% by weight or less. It is. If this upper limit is exceeded, the electrical conductivity may be reduced. The chain ether is not an essential component of the non-aqueous solvent, and the non-aqueous solvent may not contain the chain ether.

  In the case where cyclic ethers are used as the non-aqueous solvent, the ratio of the cyclic ethers in the non-aqueous solvent is usually 60% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less. . If this upper limit is exceeded, there is a risk that the storage characteristics will be degraded. Note that the cyclic ethers are not essential components of the non-aqueous solvent, and the non-aqueous solvent may not contain the cyclic ethers.

  One preferred combination of non-aqueous solvents is a combination mainly composed of cyclic carbonates and chain carbonates. Among them, the total ratio of the cyclic carbonates and the chain carbonates in the non-aqueous solvent is usually 85% by volume or more, preferably 90% by volume or more, more preferably 95% by volume or more, and the cyclic carbonates. And the chain carbonates have a volume ratio of 5:95 or more, preferably 10:90 or more, more preferably 15:85 or more, and usually 45:55 or less, more preferably 40:60 or less. .

  It is preferable to use a nonaqueous electrolytic solution in which a lithium salt and a specific dicarboxylic acid ester compound are contained in such a mixed solvent because the balance between cycle characteristics, large current discharge characteristics, and gas generation suppression of a lithium secondary battery is improved.

  Examples of preferred combinations of cyclic carbonates and chain carbonates include combinations of ethylene carbonate and dialkyl carbonates. Specifically, ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate and ethyl methyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate and diethyl carbonate and ethyl Examples include methyl carbonate, a combination of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

A combination in which propylene carbonate is further added to these ethylene carbonate and dialkyl carbonate is also mentioned as a preferable combination. In this case, the volume ratio of ethylene carbonate to propylene carbonate is usually 99: 1 or less, preferably 95: 5 or less, and usually 1:99 or more, preferably 20:80 or more.
A combination of propylene carbonate and the above-mentioned dialkyl carbonates is also preferable.

  Other preferable examples of the non-aqueous solvent include those containing 60% by volume or more of an organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, γ-butyrolactone, and γ-valerolactone. A lithium secondary battery using a non-aqueous electrolyte solution containing a lithium salt and a specific dicarboxylic acid ester compound in the mixed solvent is less likely to evaporate or leak even when used at a high temperature. Among these, the total of ethylene carbonate and γ-butyrolactone in the nonaqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate and γ-butyrolactone is 5:95 to 45%. : 55, or the total of ethylene carbonate and propylene carbonate in the non-aqueous solvent is 80% by volume or more, preferably 90% by volume or more, and the volume ratio of ethylene carbonate to propylene carbonate is 30:70 to Those that are 80:20 are preferred. A lithium secondary battery using a nonaqueous electrolytic solution in which a lithium salt and a specific dicarboxylic acid ester compound are contained in such a mixed solvent is preferable because the balance between storage characteristics and gas generation suppression is improved.

  It is also preferable to use a phosphorus-containing organic solvent as the non-aqueous solvent. When the phosphorus-containing organic solvent is contained in the non-aqueous solvent so as to be in the range of usually 10% by volume or more, preferably 10 to 80% by volume, the flammability of the electrolytic solution can be lowered. In particular, when a phosphorus-containing organic solvent is used in combination with one or more nonaqueous solvents selected from the group consisting of ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, and dialkyl carbonate, it is obtained. This is preferable because the balance between the cycle characteristics and large current discharge characteristics of the lithium secondary battery is improved.

  In this specification, the capacity of the non-aqueous solvent is a measured value at 25 ° C., but for a solid at 25 ° C. such as ethylene carbonate, the measured value at the melting point is used.

<Specific dicarboxylic acid ester compound>
The non-aqueous electrolyte solution for a lithium secondary battery of the present invention further contains a specific dicarboxylic acid ester compound, that is, a dicarboxylic acid ester compound represented by the following general formula [1], in addition to the above-described electrolyte and non-aqueous solvent. The feature is to do.
R ¹ (COOR ² ) (COOR ³ ) [1]
(In the formula, R ¹ is a divalent hydrocarbon group having 2 to 20 carbon atoms which may be substituted with a fluorine atom and / or a chlorine atom and may contain a carbon-carbon unsaturated bond. R ² and R ³ are each independently a hydrocarbon having 1 to 20 carbon atoms which may be substituted with a fluorine atom and / or a chlorine atom, and may contain a carbon-carbon unsaturated bond Although it is a group, at least one of R ² and R ³ is a hydrocarbon group represented by the following general formula [2].
-CR ⁴ R ⁵ -CR ⁶ = CR ⁷ R ⁸ ... [2]
(Wherein R ^{4 to} R ⁸ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a fluorine atom and / or a chlorine atom, and includes a carbon-carbon unsaturated bond). Or a hydrocarbon group having 1 to 10 carbon atoms, and any two groups of R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be linked to form a ring. .))

In the general formula [1], R ¹ may be substituted with a fluorine atom and / or a chlorine atom, and may contain a carbon-carbon unsaturated bond, and is a divalent carbon atom having 2 to 20 carbon atoms. Although it is a hydrogen group, the carbon number is 2 or more and 20 or less normally, Preferably it is 2 or more and 10 or less, More preferably, it is 2 or more and 6 or less.
Such divalent dicarboxylic acid having a hydrocarbon group ^(R 1 _(COOH) 2) as succinic acid as R ^1, maleic acid, acetylene dicarboxylic acid, fumaric acid, methyl succinic acid, citraconic acid, itaconic acid, mesaconic acid Glutaric acid, 2-butene-1,4-dicarboxylic acid, adipic acid, 2,3-dimethylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, 2,2-dimethylglutaric acid, 2,3- Dimethyl glutaric acid, pimelic acid, isophthalic acid, phthalic acid, terephthalic acid, cis-4-cyclohexene-1,2-dicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 3-ethyl-3 -Methylglutaric acid, suberic acid, azelaic acid, homophthalic acid, methylphthalic acid, sebacic acid, ginger Acid, phenylene diacetic acid, and the like phenyl succinic acid.

R ¹ is particularly preferably a divalent saturated hydrocarbon group which may be substituted with a fluorine atom and / or a chlorine atom, and such a divalent saturated hydrocarbon group is preferably represented as R ^1. Examples of the dicarboxylic acid (R ¹ (COOH) ₂ ) include succinic acid, methyl succinic acid, glutaric acid, adipic acid, 2,3-dimethyl succinic acid, 2-methyl glutaric acid, 3- Methyl glutaric acid, 2,2-dimethyl glutaric acid, 2,3-dimethyl glutaric acid, pimelic acid, 1,2-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 3-ethyl-3-methylglutaric acid, suberin Examples include acids, azelaic acid, sebacic acid, and camphoric acid.

Further, some or all of the hydrogen atoms of the hydrocarbon group of R ¹ may be substituted with a fluorine atom and / or a chlorine atom. In this case, it is obtained that the hydrocarbon group is particularly substituted with a fluorine atom. This is more preferable from the viewpoint of the electrochemical stability of the non-aqueous electrolyte.

In the general formula [1], R ² and R ³ may each independently be substituted with a fluorine atom and / or a chlorine atom, and may contain a carbon-carbon unsaturated bond. a C 1 -C 20 hydrocarbon group, but at least one of R ² and R ³ is a hydrocarbon group represented by the following general formula [2].
-CR ⁴ R ⁵ -CR ⁶ = CR ⁷ R ⁸ ... [2]
(Wherein R ^{4 to} R ⁸ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a fluorine atom and / or a chlorine atom, and includes a carbon-carbon unsaturated bond). Or a hydrocarbon group having 1 to 10 carbon atoms, and any two groups of R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be linked to form a ring. .)

Examples of the hydrocarbon groups of R ² and R ³ represented by the general formula [2] include allyl group, 3-buten-2-yl group, 2-methyl-2-propenyl group, crotyl group, 3- Methyl-2-butenyl group, 1-penten-3-yl group, trans-2-hexen-1-yl group, cis-2-hexen-1-yl group, benzyl group, 1-cyclohexenylmethyl group, cinnamyl group Etc.

Examples of the hydrocarbon groups of R ² and R ³ that are not hydrocarbon groups represented by the general formula [2] include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, A sec-butyl group, an isobutyl group, a tert-butyl group, a cyclohexyl group, etc. are mentioned.

Examples of the ring formed by connecting any two groups of R ^{4 to} R ⁸ include cyclopentane, cyclohexane, cyclopentene, and cyclohexene. Two or more of these rings may be present in the specific dicarboxylic acid ester compound represented by the general formula [1].

Some or all of the hydrogen atoms of the hydrocarbon group of R ² and R ³ may be substituted with a fluorine atom and / or a chlorine atom. In this case, in particular, the hydrogen atom must be substituted with a fluorine atom. Is more preferable from the viewpoint of electrochemical stability of the obtained nonaqueous electrolytic solution.

  The specific dicarboxylic acid ester compound represented by the general formula [1] is preferably diallyl succinate, diallyl maleate, diallyl acetylenedicarboxylate, diallyl fumarate, diallyl methyl succinate, diallyl citraconic acid, diallyl itaconate, Diallyl mesaconic acid, diallyl glutarate, diallyl 2-butene-1,4-dicarboxylate, diallyl adipate, diallyl 2,3-dimethylsuccinate, diallyl 2-methylglutarate, diallyl 3-methylglutarate, 2, 2 -Diallyl dimethyl glutarate, diallyl 2,3-dimethyl glutarate, diallyl pimelate, diallyl isophthalate, diallyl phthalate, diallyl terephthalate, cis-4-cyclohexene-1,2-dicarboxylate diallyl, 1,2-cyclohexane Zikal Diallyl acid, diallyl 1,4-cyclohexanedicarboxylate, diallyl 3-ethyl-3-methylglutarate, diallyl suberate, diallyl azelate, diallyl homophthalate, diallyl methylphthalate, diallyl sebacate, diallyl oxalate, Diallylphenylene diacetate, diallyl phenyl succinate, di-3-buten-2-yl succinate, di-3-buten-2-yl maleate, di-3-buten-2-yl acetylenedicarboxylate, di-3-butene fumarate -2-yl, di-3-buten-2-yl glutarate, di-3-buten-2-yl 2-butene-1,4-dicarboxylate, di-3-buten-2-yl adipate, di-3 phthalate -Buten-2-yl, di-3-buten-2-yl terephthalate, cis-4-cyclohexene-1,2-dicarboxylic acid Di-3-buten-2-yl, 1,3-cyclohexanedicarboxylic acid di-3-buten-2-yl, 1,4-cyclohexanedicarboxylic acid di-3-buten-2-yl, succinic acid di-2-methyl-2- Propenyl, di-2-methyl-2-propenyl maleate, di-2-methyl-2-propenyl acetylenedicarboxylate, di-2-methyl-2-propenyl fumarate, di-2-methyl-2-propenyl glutarate, 2-butene -1,4-dicarboxylic acid di-2-methyl-2-propenyl, di-2-methyl-2-propenyl adipate, di-2-methyl-2-propenyl phthalate, di-2-methyl-2-propenyl terephthalate, cis -4-cyclohexene-1,2-dicarboxylic acid di-2-methyl-2-propenyl, 1,2-cyclohexanedicarboxylic acid di-2-methyl-2-propenyl Nyl, 1,2-cyclohexanedicarboxylic acid di-2-methyl-2-propenyl, succinic acid dicrotyl, maleic acid dicrotyl, acetylenedicarboxylic acid dicrotyl, fumarate dicrotyl, glutaric acid dicrotyl, 2-butene-1,4-dicarboxylic acid dicrotyl , Dicrotyl adipate, dicrotyl phthalate, dicrotyl terephthalate, cis-4-cyclohexene-1,2-dicarboxylate dicrotyl, 1,2-cyclohexanedicarboxylate dicrotyl, 1,4-cyclohexanedicarboxylate dicrotyl, succinate dibenzyl, malein Dibenzyl acid, dibenzyl acetylenedicarboxylate, dibenzyl fumarate, dibenzyl glutarate, dibenzyl 2-butene-1,4-dicarboxylate, dibenzyl adipate, dibenzyl phthalate, terephthalic acid Benzyl, cis-4-cyclohexene-1,2-dicarboxylate, dibenzyl 1,2-cyclohexanedicarboxylate, dibenzyl 1,4-cyclohexanedicarboxylate, dicinnamyl succinate, dicinnamyl maleate, dicinnamyl acetylenedicarboxylate, dicinnamyl fumarate Dicinnamyl glutarate, dicinnamyl 2-butene-1,4-dicarboxylate, dicinnamyl adipate, dicinnamyl phthalate, dicinnamyl terephthalate, cis-4-cyclohexene-1,2-dicarboxylic acid dicinnamyl, 1,2-cyclohexanedicarboxylic acid Examples include dicinnamyl and dicinnamyl 1,4-cyclohexanedicarboxylate.

  Among them, diallyl succinate, diallyl maleate, diallyl fumarate, diallyl glutarate, diallyl adipate, diallyl phthalate, diallyl terephthalate, di-3-buten-2-yl succinate, di-3-butene-2 maleate -Il, di-3-buten-2-yl glutarate, di-3-buten-2-yl adipate, di-3-buten-2-yl phthalate, di-3-buten-2-yl terephthalate, di-succinate 2-methyl-2-propenyl, di-2-methyl-2-propenyl maleate, di-2-methyl-2-propenyl glutarate, di-2-methyl-2-propenyl adipate, di-2-methyl-2-phthalate Propenyl, di-2-methyl-2-propenyl terephthalate, dicrotyl succinate, dicrotyl maleate, dicrotyl glutarate, dicrotate adipate Dicrotyl phthalate, dicrotyl terephthalate, dibenzyl succinate, dibenzyl maleate, dibenzyl glutarate, dibenzyl adipate, dibenzyl phthalate, dibenzyl terephthalate, dicinnamyl succinate, dicinnamyl maleate, dicinnamyl acetylenedicarboxylate, dicinnamyl fumarate , Dicinnamyl glutarate, dicinnamyl adipate, dicinnamyl phthalate, and dicinnamyl terephthalate. Furthermore, diallyl succinate, diallyl maleate, fumarate from the viewpoint of availability of raw materials for producing these compounds and cost. Particularly preferred are diallyl acid, diallyl glutarate, diallyl adipate, diallyl phthalate and diallyl terephthalate.

In particular, as the specific dicarboxylic acid ester compound in which R ¹ is a divalent saturated hydrocarbon group in the general formula [1], which is suitable as the specific dicarboxylic acid ester compound, preferably diallyl succinate, methyl succinic acid Diallyl, diallyl glutarate, diallyl adipate, diallyl 2,3-dimethyl succinate, diallyl 2-methyl glutarate, diallyl 3-methyl glutarate, diallyl 2,2-dimethyl glutarate, diallyl 2,3-dimethyl glutarate 1,2-cyclohexanedicarboxylate diallyl, 1,4-cyclohexanedicarboxylate diallyl, 3-ethyl-3-methylglutarate diallyl, diallyl suberate, diallyl azelate, diallyl sebacate, diallyl oxalate, succinic acid Di-3-buten-2-yl, adipine Di-3-buten-2-yl acid, di-2-buten-2-yl 1,2-cyclohexanedicarboxylate, di-3-buten-2-yl 1,4-cyclohexanedicarboxylate, di-2-methyl-2 succinate -Propenyl, di-2-methyl-2-propenyl glutarate, di-2-methyl-2-propenyl adipate, di-2-methyl-2-propenyl 1,2-cyclohexanedicarboxylate, di-2-methyl 1,4-cyclohexanedicarboxylate -Methyl-2-propenyl, dicrotyl succinate, dicrotyl glutarate, dicrotyl adipate, dicrotyl 1,2-cyclohexanedicarboxylate, dicrotyl 1,4-cyclohexanedicarboxylate, dibenzyl succinate, dibenzyl glutarate, dibenzyl adipate, 1 2,2-cyclohexanedicarboxylate dibenzyl, 1,4-cycl Dibenzyl hexanedicarboxylate, dicinnamyl succinate, dicinnamyl glutarate, dicinnamyl adipate, dicinnamyl 1,2-cyclohexanedicarboxylate, dicinnamyl 1,4-cyclohexanedicarboxylate, among them diallyl succinate, diallyl glutarate, adipine Diallyl acid, di-3-buten-2-yl succinate, di-3-buten-2-yl glutarate, di-3-buten-2-yl adipate, di-2-methyl-2-propenyl succinate, diglutarate 2-methyl-2-propenyl, di-2-methyl-2-propenyl adipate, dicrotyl succinate, dicrotyl glutarate, dicrotyl adipate, dibenzyl succinate, dibenzyl glutarate, dibenzyl adipate, dicinnamyl succinate, dicinnamic glutarate , Jishin'namiru adipic acid are preferable, further, ease of availability of raw materials in the production of these compounds, the cost standpoint from diallyl succinate, glutaric acid, diallyl adipate is particularly preferable.

  These specific dicarboxylic acid ester compounds may be used alone or in combination of two or more.

  The content of the specific dicarboxylic acid ester compound represented by the general formula [1] in the nonaqueous electrolytic solution is usually 0.001% by weight or more, preferably 0.01% with respect to the total weight of the nonaqueous electrolytic solution. % By weight or more, more preferably 0.1% by weight or more, usually 10% by weight or less, preferably 5% by weight or less, more preferably 2% by weight or less. When the content of the specific dicarboxylic acid ester compound is less than the above lower limit, the effect of suppressing the oxidative decomposition of other non-aqueous electrolyte components that proceed on the surface of the positive electrode is not acted as desired, and the effect of the present invention is exhibited. You may not be able to do it. On the other hand, when the above upper limit is exceeded, the reaction on the surface of the positive electrode proceeds excessively, which may deteriorate various characteristics of the battery.

  The specific dicarboxylic acid ester compound represented by the general formula [1] can be used in combination of two or more, so long as it does not exceed the scope of the effect of the present invention. Even in this case, the total content in the non-aqueous electrolyte is usually 0.001% by weight or more, preferably 0.01% by weight or more, more preferably 0.1% by weight or more, usually 10% by weight. Hereinafter, it is preferably 5% by weight or less, more preferably 2% by weight or less.

<Cyclic carbonate ester having carbon-carbon unsaturated bond>
The non-aqueous electrolyte for a lithium secondary battery of the present invention is a cyclic carbonate having a carbon-carbon unsaturated bond together with the specific dicarboxylic acid ester compound represented by the general formula [1] in the non-aqueous electrolyte. (That is, it preferably contains an unsaturated cyclic carbonate).

  Examples of the cyclic carbonate having a carbon-carbon unsaturated bond include vinylene carbonate compounds, vinyl ethylene carbonate compounds, methylene ethylene carbonate compounds, and the like. Examples of the methylene ethylene carbonate compound include methylene ethylene carbonate, 4,4-dimethyl-5-methylene ethylene carbonate, 4,4-diethyl-5-methylene ethylene carbonate, and the like.

  Preferable examples of the cyclic carbonate having a carbon-carbon unsaturated bond include those represented by the following general formula [3] or the following general formula [4].

（式中、Ｒ^９〜Ｒ^１６は、それぞれ独立に、水素原子、フッ素原子、塩素原子、或いはフッ素原子および／または塩素原子で置換されていてもよく、また炭素−炭素不飽和結合を含んでいてもよい、炭素数１〜６の炭化水素基である。）

(Wherein R ^{9 to} R ¹⁶ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a fluorine atom and / or a chlorine atom, and includes a carbon-carbon unsaturated bond). It may be a hydrocarbon group having 1 to 6 carbon atoms.)

Here, examples of the hydrocarbon group of R ^{9 to} R ¹⁶ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, and a cyclohexyl group. Etc. Some or all of the hydrogen atoms of the hydrocarbon groups of R ^{9 to} R ¹⁶ may be substituted with a fluorine atom and / or a chlorine atom. In this case, it is particularly preferable that the hydrocarbon group is substituted with a fluorine atom. It is more preferable from the viewpoint of electrochemical stability of the non-aqueous electrolyte solution.

  Examples of the unsaturated cyclic carbonate represented by the general formula [3] or [4] include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, and fluoro vinylene. Carbonate, trifluoromethyl vinylene carbonate, vinyl ethylene carbonate, 4-methyl-4-vinyl ethylene carbonate, 4-ethyl-4-vinyl ethylene carbonate, 4-n-propyl-4-vinyl ethylene carbonate, 5-methyl-4- Examples include vinyl ethylene carbonate, 4,4-divinyl ethylene carbonate, 4,5-divinyl ethylene carbonate, and the like.

  Among these unsaturated cyclic carbonates, vinylene carbonate, 4-methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4-vinyl ethylene carbonate and 5-methyl-4-vinyl ethylene carbonate are preferred, vinylene carbonate, 4-vinyl ethylene Carbonate is more preferred.

  In addition, these unsaturated cyclic carbonates may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  When the non-aqueous electrolyte for a lithium secondary battery of the present invention contains the unsaturated cyclic carbonate as described above, the proportion in the non-aqueous electrolyte is usually 0.01% by weight or more, preferably 0.1% by weight. % Or more, usually 10% by weight or less, preferably less than 5% by weight, more preferably 4% by weight or less. If the content is too small, the negative electrode film based on these reductive decompositions may not be sufficiently formed, and battery characteristics may not be sufficiently developed. On the other hand, if the content is too large, an excess amount There is a risk of generation of decomposition gas based on the oxidative decomposition of and degradation of battery characteristics.

[Other additives]
The non-aqueous electrolyte for a lithium secondary battery of the present invention is a polyoxyethylene having a trioctyl phosphate and a perfluoroalkyl group in order to improve the paintability with a separator described later in addition to the non-aqueous solvent and the electrolyte. You may contain 1 type (s) or 2 or more types of surfactants, such as ethers and perfluorooctane sulfonate ester, in 0.01-1 weight% with respect to non-aqueous electrolyte solution.

  Furthermore, the non-aqueous electrolyte for lithium secondary batteries of the present invention may contain various overcharge inhibitors and other auxiliaries.

Examples of the overcharge inhibitor include benzene derivatives described in JP-A-8-203560, JP-A-7-302614, JP-A-9-50822, JP-A-8-273700, JP-A-9-17447, and the like; Biphenyl and derivatives thereof described in JP-A Nos. 106,835, 9-171840, 10-32258, 7-302614, 11-162512, 2939469, and 2963898; Partially hydrogenated terphenyl compounds and derivatives thereof described in JP 2003-100344, JP 2003-100345, JP 2003-100346, JP 2003-115325, and the like; JP 2003-77536 A 2-oxazolidone derivatives described in JP-A-9-45369, the same Pyrrole derivatives described in JP-A Nos. 0-32258 and the like; aromatic compounds such as aniline derivatives described in JP-A Nos. 7-320778 and 7-302614; and Japanese Patent No. 2983205 In addition, compounds such as those described in JP-A-2001-15158 can be contained. Any one of these may be used alone, or two or more may be used in any combination and ratio.
The overcharge inhibitor is preferably contained in a proportion of 0.1 to 5% by weight with respect to the non-aqueous electrolyte.

As other film forming agents, it is preferable to use fluorine-substituted carbonates, aryl-substituted carbonates, cyclic carboxylic acid anhydrides, sulfonic acid derivatives, sulfone compounds, sulfite compounds, and the like.
As the fluorine-substituted carbonate compound, fluoroethylene carbonate, 4-trifluoromethylethylene carbonate, or the like is used.
As the aryl-substituted carbonate, 4-phenylethylene carbonate, methylphenyl carbonate, or the like is used.
As the cyclic carboxylic acid anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, trimellitic anhydride, phthalic anhydride and the like are used.
As the sulfonic acid derivative, propane sultone, methyl methanesulfonate, ethyl methanesulfonate, dimethylmethanesulfonate amide, or the like is used.
As the sulfone compound, dimethyl sulfone, sulfolane, 3-sulfolene and the like are used.
Examples of the sulfite compound include ethylene sulfite, trimethylene sulfite, erythritan sulfite, vinyl ethylene sulfite, dimethyl sulfite, ethyl methyl sulfite, and diethyl sulfite.
Any one of these may be used alone, or two or more may be used in any combination and ratio.
These film forming agents are preferably contained in an amount of 0.01 to 10% by weight, preferably 0.1 to 8% by weight, based on the non-aqueous electrolyte, because the battery capacity maintenance characteristics and cycle characteristics are improved.

Other auxiliary agents include carbonate compounds such as fluoroethylene carbonate, 4-trifluoropropylene carbonate, 4-phenylethylene carbonate, methylphenyl carbonate, erythritan carbonate, spiro-bis-dimethylene carbonate, methoxyethyl methyl carbonate; Succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, trimellitic anhydride, phthalic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic acid Carboxylic anhydrides such as anhydrides and phenylsuccinic anhydrides; ethylene sulfite, trimethylene sulfite, erythritan sulfite, vinyl ethylene sulfite, dimethyl sulfa , Ethyl methyl sulfite, diethyl sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone and tetramethyl thiuram monosulfide, N, N-dimethylmethane Sulfur-containing compounds such as sulfonamide and N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazo Nitrogen-containing compounds such as ridinone and N-methylsuccinimide; hydrocarbon compounds such as heptane, octane and cycloheptane; fluorine-containing aromatic compounds such as fluorobenzene, difluorobenzene, hexafluorobenzene and benzotrifluoride Et That.
Any one of these may be used alone, or two or more may be used in any combination and ratio.
When the non-aqueous electrolyte solution for lithium secondary batteries of the present invention contains these auxiliaries, the proportion is usually 0.01% by weight or more and usually 10% by weight or less based on the total amount of the non-aqueous electrolyte solution. Range. By containing these auxiliary agents in the non-aqueous electrolyte for lithium secondary batteries of the present invention, capacity maintenance characteristics and cycle characteristics after high-temperature storage of lithium secondary batteries can be improved.

[Method for producing non-aqueous electrolyte for lithium secondary battery]
The nonaqueous electrolytic solution for a lithium secondary battery of the present invention contains the above-mentioned electrolyte, the specific dicarboxylic acid ester compound represented by the general formula [1], and the nonaqueous solvent other than the specific dicarboxylic acid ester compound described above, and It can be prepared by adding and dissolving the above-mentioned unsaturated cyclic carbonate used as necessary, other auxiliary agents, and the like.

  In preparing the non-aqueous electrolyte solution, it is preferable to dehydrate each component such as a non-aqueous solvent in advance. Specifically, it is preferable to dehydrate until the water content is usually 50 ppm or less, particularly 20 ppm or less. The method of dehydration can be arbitrarily selected, and examples thereof include a method of heating under reduced pressure or passing through a molecular sieve.

  Note that the non-aqueous electrolyte solution for a lithium secondary battery of the present invention may be used in a semi-solid state by gelation with a gelling agent such as a polymer. The proportion of the non-aqueous electrolyte in the semi-solid electrolyte is usually 30% by weight or more, preferably 50% by weight or more, more preferably 75% by weight or more, and usually 99% by weight with respect to the total amount of the semi-solid electrolyte. .95% by weight or less, preferably 99% by weight or less, more preferably 98% by weight or less. If the ratio of the non-aqueous electrolyte is too large, it will be difficult to hold the non-aqueous electrolyte and liquid leakage will easily occur. Conversely, if the ratio of the non-aqueous electrolyte is too small, the charge / discharge efficiency and capacity will be reduced. May be insufficient.

[II] Lithium Secondary Battery Next, the lithium secondary battery of the present invention will be described.
The lithium secondary battery of the present invention comprises at least a negative electrode and a positive electrode capable of inserting and extracting lithium, and the above-described non-aqueous electrolyte for a lithium secondary battery of the present invention.
That is, the lithium secondary battery of the present invention is the same as the conventionally known lithium secondary battery except for the non-aqueous electrolyte, and is usually porous with the non-aqueous electrolyte for the lithium secondary battery of the present invention impregnated. A positive electrode and a negative electrode are laminated via a membrane (separator), and these are housed in a case. Therefore, the shape of the lithium secondary battery of the present invention is not particularly limited, and may be any of a cylindrical shape, a square shape, a laminate shape, a coin shape, a large size, and the like.

[Positive electrode active material]
Examples of the positive electrode active material include transition metal oxides, composite oxides of transition metals and lithium (lithium transition metal composite oxides), transition metal sulfides, inorganic compounds such as metal oxides, lithium metals, lithium alloys or These complexes are mentioned. Specifically, transition metal oxides such as MnO, V ₂ O ₅ , V ₆ O ₁₃ , and TiO ₂ ; lithium cobalt composite oxide having a basic composition of LiCoO ₂ , lithium nickel composite oxide having LiNiO ₂ , LiMn Lithium transition metal composite oxides such as lithium manganese composite oxide, lithium nickel manganese cobalt composite oxide and lithium nickel cobalt aluminum composite oxide which are ₂ O ₄ or LiMnO ₂ ; transition metal sulfides such as TiS and FeS; SnO ₂ And metal oxides such as SiO ₂ . Among them, lithium transition metal composite oxides, specifically lithium cobalt composite oxide, lithium nickel composite oxide, lithium cobalt nickel composite oxide, lithium nickel manganese cobalt composite oxide, lithium nickel cobalt aluminum composite oxide, The high capacity and the high cycle characteristics can be achieved at the same time. In addition, lithium transition metal composite oxide is a part of cobalt, nickel or manganese other than Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, etc. Substitution with a metal is preferable because the structure can be stabilized.
Any one of these positive electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.

[Negative electrode active material]
As the negative electrode active material, a carbonaceous material or a metal compound capable of inserting and extracting lithium, lithium metal, a lithium alloy, and the like can be used. Among these, a carbonaceous material, in particular, graphite or a surface of graphite coated with amorphous carbon as compared with graphite is preferable. Any one of these negative electrode active materials may be used alone, or two or more thereof may be used in any combination and ratio.

  Graphite used as the negative electrode active material has a lattice plane (002 plane) d value (interlayer distance) of 0.335 to 0.340 nm, particularly 0.335 to 0, as determined by X-ray diffraction by the Gakushin method. It is preferable that the thickness is 338 nm, particularly 0.335 to 0.337 nm. The crystallite size (Lc) determined by X-ray diffraction by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, particularly preferably 100 nm or more. The ash content is usually 1% by weight or less, preferably 0.5% by weight or less, particularly preferably 0.1% by weight or less.

  The graphite surface coated with amorphous carbon is preferably graphite having a d-value of 0.335 to 0.338 nm on the lattice plane (002 plane) in X-ray diffraction as a core material. A carbonaceous material having a larger d-value on the lattice plane (002 plane) in X-ray diffraction than the core material is attached, and the d-value on the lattice plane (002 plane) in X-ray diffraction is greater than that of the core material and the core material The ratio with respect to the carbonaceous material having a large is 99/1 to 80/20 by weight. When this is used, a negative electrode having a high capacity and hardly reacting with the electrolytic solution can be produced.

  The particle size of the carbonaceous material is a median diameter measured by a laser diffraction / scattering method, and is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, most preferably 7 μm or more, and usually 100 μm or less, preferably 50 μm or less. More preferably, it is 40 micrometers or less, Most preferably, it is 30 micrometers or less.

The specific surface area of the carbonaceous material by the BET method is usually 0.3 m ² / g or more, preferably 0.5 m ² / g or more, more preferably 0.7 m ² / g or more, and most preferably 0.8 m ² / g. These are usually 25 m ² / g or less, preferably 20 m ² / g or less, more preferably 15 m ² / g or less, and most preferably 10 m ² / g or less.

Further, the carbonaceous material is analyzed by Raman spectrum using argon ion laser light, the peak is the peak intensity of the peak _{P A} in the range of 1570~1620cm ^-1 _I A, in the range of 1300~1400cm ^-1 P If the peak intensity of the _B was _{I B,} R value represented by the ratio of _{I B} and _{I a (= I B / I} a) is what is preferably in the range of 0.01 to 0.7. Further, the half width of the peak in the range of 1570～1620Cm ^-1 usually 26cm ^-1 or less, are preferred in particular 25 cm ^-1 or less.

  Examples of metal compounds capable of inserting and extracting lithium as the negative electrode active material include Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, and Zn. The compound containing metals, such as these, is mentioned. These metals may be used in any form such as a simple substance, an oxide, or an alloy with lithium. In the present invention, those containing an element selected from Al, Ge, Si and Sn are preferable, and an oxide or lithium alloy of a metal selected from Al, Si and Sn is more preferable.

  A metal compound capable of occluding and releasing lithium, or an oxide thereof or an alloy with lithium generally has a larger capacity per unit weight than a carbon material typified by graphite, and therefore requires a higher energy density. It is suitable for a secondary battery.

[Electrode manufacturing method]
The electrode may be manufactured according to a conventional method. For example, it can be formed by adding a binder, a thickener, a conductive material, a solvent or the like to a negative electrode or a positive electrode active material to form a slurry, applying the slurry to a current collector, drying it, and then pressing it.
In addition, a material obtained by adding a binder or a conductive material to an active material is roll-formed as it is to form a sheet electrode, a pellet electrode is formed by compression molding, and an electrode is formed on the current collector by a technique such as vapor deposition, sputtering, or plating. A thin film of material can also be formed.
As the binder for binding the active material, any material can be used as long as it is a material that is stable with respect to the solvent and the electrolyte used in manufacturing the electrode. For example, fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene, polyolefins such as polyethylene and polypropylene, unsaturated polymers such as styrene / butadiene rubber, isoprene rubber and butadiene rubber, and copolymers thereof, ethylene-acrylic acid copolymer Examples thereof include acrylic acid-based polymers such as polymers, ethylene-methacrylic acid copolymers, and copolymers thereof.

The electrode may contain a thickener, a conductive material, a filler and the like for the purpose of increasing mechanical strength and electrical conductivity.
Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein.
Examples of the conductive material include metal materials such as copper and nickel, and carbon materials such as graphite and carbon black.

When graphite is used as the negative electrode active material, the density of the negative electrode active material layer after drying and pressing is usually 1.45 g / cm ³ or more, preferably 1.55 g / cm ³ or more, particularly preferably 1.60 g. / Cm ³ or more.
The density of the positive electrode active material layer after drying and pressing is usually 3.0 g / cm ³ or more.

  As the current collector, a metal or an alloy is usually used. Specifically, examples of the negative electrode current collector include copper and its alloys, nickel and its alloys, stainless steel and the like, and copper and its alloys are particularly preferable. Examples of the positive electrode current collector include aluminum, titanium, tantalum, and alloys thereof, among which aluminum and alloys thereof are preferable.

  In order to improve the binding effect with the active material layer formed on the surface, it is preferable that the surface of these current collectors is roughened in advance. Surface roughening methods include blasting, rolling with a rough roll, polishing cloth with a fixed abrasive particle, grinder, emery buff, wire brush equipped with steel wire, etc. Examples thereof include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.

  Further, in order to reduce the weight of the current collector and improve the energy density per weight of the battery, a perforated current collector such as an expanded metal or a punching metal can be used. This type of current collector can be freely changed in weight by changing its aperture ratio. Further, when an active material layer is formed on both surfaces of this type of current collector, the active material layer is further less likely to peel due to the rivet effect through the hole. However, when the aperture ratio becomes too high, the contact area between the active material layer and the current collector becomes small, so that the adhesive strength may be lowered.

  The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and is usually 100 μm or less, preferably 50 μm or less. If the thickness of the current collector is too thick, the capacity of the entire battery will be too low, and conversely if it is too thin, handling may be difficult.

[Separator]
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the separator is typically impregnated with the non-aqueous electrolyte solution for a lithium secondary battery of the present invention.

  There are no particular restrictions on the material and shape of the separator, but it is possible to use a porous sheet or nonwoven fabric that is formed of a material that is stable with respect to the non-aqueous electrolyte for a lithium secondary battery of the present invention and has excellent liquid retention. preferable. As a material for the separator, polyolefin such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone and the like can be used, and polyolefin is preferable.

  The thickness of the separator is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin, the insulation and mechanical strength may be deteriorated. If the separator is too thick, not only the battery performance such as the rate characteristic is deteriorated, but also the energy density of the whole battery is lowered.

  The porosity of the separator is usually 20% or more, preferably 35% or more, more preferably 45% or more, and usually 90% or less, preferably 85% or less, more preferably 75% or less. If the porosity is too small, the membrane resistance increases and the rate characteristics tend to deteriorate. On the other hand, if it is too large, the mechanical strength of the separator is lowered and the insulating property tends to be lowered.

  The average pore diameter of the separator is usually 0.5 μm or less, preferably 0.2 μm or less, and usually 0.05 μm or more. If the average pore diameter is too large, short circuits are likely to occur, and if it is too small, the membrane resistance increases and the rate characteristics may deteriorate.

[Exterior body]
The material of the battery case used in the lithium secondary battery of the present invention is also arbitrary, and nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like is used.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples, unless the summary is exceeded.

[Example 1]
<Manufacture of positive electrode>
85 parts by weight of LiCoO ₂ , 6 parts by weight of carbon black and 9 parts by weight of polyvinylidene fluoride (made by Kureha Chemical Co., Ltd., trade name “KF-1000”) are mixed, and N-methyl-2-pyrrolidone is added to form a slurry. After uniformly applying and drying on both surfaces of an aluminum foil having a thickness of 15 μm, the positive electrode active material layer was pressed to a density of 3.0 g / cm ³ to obtain a positive electrode.

<Manufacture of negative electrode>
The d-value of the lattice plane (002 plane) in X-ray diffraction is 0.336 nm, the crystallite size (Lc) is 652 nm, the ash content is 0.07 wt%, the median diameter by laser diffraction / scattering method is 12 μm, and the ratio by BET method The half-value width of a peak whose surface area is 7.5 m ² / g and the R value (= I _B / I _A ) determined from Raman spectrum analysis using an argon ion laser beam is in the range of 0.12, 1570 to 1620 cm ^−1. Was mixed with 94 parts by weight of natural graphite powder having a weight of 19.9 cm ⁻¹ and 6 parts by weight of polyvinylidene fluoride, and N-methyl-2-pyrrolidone was added to form a slurry. This slurry was uniformly applied to one side of a 12 μm thick copper foil and dried, and then pressed so that the density of the negative electrode active material layer was 1.6 g / cm ³ to obtain a negative electrode.

<Preparation of electrolyte>
Under a dry argon atmosphere, LiPF ₆ sufficiently dried in a mixture of ethylene carbonate and ethyl methyl carbonate (volume ratio 3: 7) was dissolved to 1.0 mol / liter to obtain a blank electrolyte. Next, 1 part by weight of diallyl succinate was added to 99 parts by weight of this blank electrolyte to prepare a desired electrolyte.

<Manufacture of lithium secondary batteries>
The positive electrode, the negative electrode, and the polyethylene separator were laminated in the order of the negative electrode, the separator, the positive electrode, the separator, and the negative electrode to produce a battery element. The battery element was inserted into a bag made of a laminate film in which both surfaces of aluminum (thickness: 40 μm) were coated with a resin layer while projecting positive and negative terminals, and the non-aqueous electrolyte prepared in the above procedure was then bagged. The sheet-like battery was manufactured by injecting the film into the inside and vacuum-sealing it.

<Battery evaluation>
The sheet-like battery is sandwiched between glass plates in order to enhance the adhesion between the electrodes, and charged and discharged at a constant current corresponding to 0.2 C at 25 ° C. and a final charge voltage of 4.2 V and a final discharge voltage of 3 V. 3 is performed to stabilize the battery, and the fourth cycle is charged to a charge end voltage of 4.2 V with a current corresponding to 0.5 C, and charging is performed until the charge current value reaches a current value corresponding to 0.05 C. After 2V-constant current constant voltage charge (CCCV charge) (0.05C cut), 3V discharge was performed at a constant current value corresponding to 0.2C, and the discharge capacity before high temperature storage was measured. After 4.2V-CCCV (0.05C cut) charge was performed again, high temperature storage was performed under conditions of 85 ° C. and 72 hours.
Before and after the high-temperature storage at 85 ° C. for 72 hours, the sheet-like battery was immersed in an ethanol bath, and the amount of gas generated from the change in volume was determined.
After measuring this volume, the battery was discharged at a constant current of 0.2 C at 25 ° C. to a discharge end voltage of 3 V, and then charged with 4.2 V-CCCV (0.05 C cut) to a current value corresponding to 1 C up to 3 V. The battery was discharged and the 1C capacity was measured. Here, 1C represents a current value that can be fully charged in one hour.
Table 1 shows the 1 C capacity (%) after high temperature storage when the discharge capacity before high temperature storage is 100.

[Example 2]
An electrolytic solution was prepared in the same manner as in Example 1 except that 2 parts by weight of diallyl succinate was added to 98 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Example 3]
An electrolytic solution was prepared in the same manner as in Example 1 except that 0.1 part by weight of diallyl succinate was added to 99.9 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Example 4]
An electrolytic solution was prepared in the same manner as in Example 1 except that 1 part by weight of diallyl adipate was added to 99 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[ Reference Example 1 ]
An electrolytic solution was prepared in the same manner as in Example 1 except that 1 part by weight of diallyl maleate was added to 99 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[ Reference Example 2 ]
An electrolytic solution was prepared in the same manner as in Example 1 except that 1 part by weight of diallyl phthalate was added to 99 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Example 5 ]
An electrolytic solution was prepared in the same manner as in Example 1 except that 2 parts by weight of vinylene carbonate and 1 part by weight of diallyl succinate were added to 97 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Example 6 ]
An electrolyte solution was prepared in the same manner as Example 1 except that 0.2 part by weight of vinylene carbonate and 1 part by weight of diallyl succinate were added to 98.8 parts by weight of the blank electrolyte. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Example 7 ]
An electrolytic solution was prepared in the same manner as in Example 1 except that 27.5 parts by weight of vinylene carbonate and 0.5 parts by weight of diallyl succinate were added to 97.5 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Example 8 ]
An electrolytic solution was prepared in the same manner as in Example 1 except that 27.8 parts by weight of vinylene carbonate and 0.2 parts by weight of diallyl succinate were added to 97.8 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Example 9 ]
An electrolyte solution was prepared in the same manner as in Example 1 except that 9 parts by weight of the blank electrolyte solution was added with 2 parts by weight of vinylene carbonate and 0.5 part by weight of diallyl adipate. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[ Reference Example 3 ]
An electrolytic solution was prepared in the same manner as in Example 1 except that 27.5 parts by weight of vinylene carbonate and 0.5 parts by weight of diallyl maleate were added to 97.5 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[ Reference Example 4 ]
An electrolytic solution was prepared in the same manner as in Example 1 except that 27.5 parts by weight of vinylene carbonate and 0.5 parts by weight of diallyl phthalate were added to 97.5 parts by weight of the blank electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, and evaluated in the same manner. The results are shown in Table 1.

[Comparative Example 1]
An electrolytic solution was prepared in the same manner as in Example 1 except that only the blank electrolytic solution was used as the electrolytic solution. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, evaluated in the same manner, and the results are shown in Table 1.

[Comparative Example 2]
An electrolytic solution was prepared in the same manner as in Example 1 except that 2 parts by weight of vinylene carbonate was added to 98 parts by weight of the blank electrolytic solution, and diallyl succinate was not added. A sheet-like battery was produced in the same manner as in Example 1 except that this electrolytic solution was used, evaluated in the same manner, and the results are shown in Table 1.

From Table 1, the following is clear.
That is, in Examples 1 to 4 in which the nonaqueous electrolytic solution contains the specific dicarboxylic acid ester compound represented by the general formula [1], the 1C capacity after high temperature storage and It can be seen that the amount of gas generated during high-temperature storage is excellent. Further, when vinylene carbonate is contained as the unsaturated cyclic carbonate in the nonaqueous electrolytic solution, the specific dicarboxylic acid ester compound represented by the general formula [1] is compared with Comparative Example 2 containing only vinylene carbonate. In Examples 5 to 9 in which the coexistence exists, it is understood that the battery characteristics represented by the 1C capacity and the amount of gas generated during high-temperature storage are excellent.

  The high energy density lithium ion secondary battery provided by the present invention having high charge / discharge efficiency and excellent storage characteristics and cycle characteristics even at high temperatures is used in various fields such as electronic devices in which lithium secondary batteries are used. It can be suitably used.

Claims (7)

A nonaqueous electrolyte solution for a lithium secondary battery, comprising a nonaqueous solvent containing a dicarboxylic acid ester compound represented by the following general formula [1] and an electrolyte.
R ¹ (COOR ² ) (COOR ³ ) [1]
(In the formula, R ¹ is a divalent saturated hydrocarbon group having 2 to 20 carbon atoms which may be substituted with a fluorine atom and / or a chlorine atom, and R ² and R ³ are each independently A hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a fluorine atom and / or a chlorine atom and may contain a carbon-carbon unsaturated bond, but at least one of R ² and R ³ Is a hydrocarbon group represented by the following general formula [2].
-CR ⁴ R ⁵ -CR ⁶ = CR ⁷ R ⁸ ... [2]
(Wherein R ^{4 to} R ⁸ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a fluorine atom and / or a chlorine atom, and includes a carbon-carbon unsaturated bond). Or a hydrocarbon group having 1 to 10 carbon atoms, and any two groups of R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be linked to form a ring. .)) 2. The lithium secondary battery according to claim 1, wherein the dicarboxylic acid ester compound represented by the general formula [1] is contained in the nonaqueous electrolytic solution in a proportion of 0.01 to 10 wt%. Non-aqueous electrolyte for use. The non-aqueous electrolyte for a lithium secondary battery according to claim 1 or 2 , further comprising a cyclic carbonate having a carbon-carbon unsaturated bond. The non-aqueous electrolyte solution for a lithium secondary battery according to claim 3 , wherein the cyclic carbonate having a carbon-carbon unsaturated bond is represented by the following general formula [3] or the following general formula [4].

(Wherein R ^{9 to} R ¹⁶ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a fluorine atom and / or a chlorine atom, and includes a carbon-carbon unsaturated bond). It may be a hydrocarbon group having 1 to 6 carbon atoms.) Carbon - carbon cyclic ester carbonate having an unsaturated bond, a lithium secondary battery according to claim 3 or 4, characterized in that it contains a proportion of 0.01 to 10 wt% in the non-aqueous electrolyte solution Non-aqueous electrolyte for use. The cyclic carbonate having a carbon-carbon unsaturated bond is selected from the group consisting of vinylene carbonate, 4-methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4-vinyl ethylene carbonate, and 5-methyl-4-vinyl ethylene carbonate. The non-aqueous electrolyte solution for a lithium secondary battery according to any one of claims 3 to 5 , wherein the non-aqueous electrolyte solution is one or two or more selected. A lithium secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and a non-aqueous electrolyte solution, wherein the non-aqueous electrolyte solution is a lithium secondary battery according to any one of claims 1 to 6. A lithium secondary battery characterized by being a non-aqueous electrolyte solution.