JP2010282760A - Nonaqueous electrolyte, nonaqueous electrolyte secondary battery, and vinylene carbonate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery superior in high temperature preservation characteristics. <P>SOLUTION: In the nonaqueous electrolyte secondary battery structured of a negative electrode and a positive electrode containing a material capable of occluding and emitting lithium, and nonaqueous electrolyte containing a nonaqueous solvent and Li salt, the nonaqueous electrolyte contains 0.1 to 10 weight% of carbonate having an unsaturated bond, with a content of a compound shown in formula (1) to be ≤10 ppm. In the formula (1), R<SB>1</SB>to R<SB>8</SB>show chlorine atom or hydrogen atom. Also, at least one of R<SB>1</SB>to R<SB>8</SB>is chlorine. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte used therein, and vinylene carbonate. More specifically, the present invention relates to a high energy density non-aqueous electrolyte secondary battery having excellent high-temperature storage characteristics by using a specific non-aqueous electrolyte.

  In the manufacturing method of vinylene carbonate, several methods have been reported so far. For example, Non-Patent Document 1, Non-Patent Document 2, Patent Document 1 and the like are known as methods for dehydrochlorination of chloroethylene carbonate obtained by chlorination of ethylene carbonate. In addition, vinylene carbonate used as a solvent for the electrolytic solution is required to have a high quality. For example, vinylene carbonate using chloroethylene carbonate as a raw material has a large variety of organic chlorine compounds and inorganic chlorine compounds as impurities. Contained and removal of impurities is under consideration. For example, distillation under reduced pressure conditions (Non-Patent Document 1, Non-Patent Document 2), a method in which vinylene carbonate is partially crystallized by a melt liquid crystal deposition method (Patent Document 2) and a method by zone melting (Non-patent Document 3) and a method of performing a dehydrochlorination reaction of chloroethylene carbonate in a high-boiling solvent such as dibutyl carbonate and then distilling (Patent Document 3) have been proposed.

  In addition, as an example of applying vinylene carbonate to a solvent of a non-aqueous electrolyte solution, in a lithium storage battery having a carbon anode, by containing vinylene carbonate in an amount of 0.01 wt% or more and less than 10 wt%, mass and capacity energy can be increased stably. It has been reported that it can be maintained (Patent Document 4), and that a secondary battery with good coulomb efficiency and cycle characteristics can be obtained by setting the chlorine content in vinylene carbonate to 100 ppm or less (Patent Document 5).

Japanese Patent Laid-Open No. 11-180974 British Patent 899205 JP 2000-26449 A Japanese Patent No. 3813953 Japanese Patent No. 3438636

J. et al. Am. Chem. Soc. , 75, 1263 (1953) J. et al. Am. Chem. Soc. , 77, 3789 (1955) J. et al. Chem. Education, 40, 351 (1963)

  However, the non-aqueous electrolyte as described above cannot be said to have sufficient high-temperature storage characteristics, and has not been able to satisfy the recent demand for higher performance of batteries. Accordingly, it is an object of the present invention to provide a non-aqueous electrolyte secondary battery excellent in high-temperature storage characteristics, a non-aqueous electrolyte used therein, and vinylene carbonate that provides the same.

  As a result of various studies to achieve the above-mentioned object, the present inventors have found that a carbonate having an unsaturated bond such as vinylene carbonate (hereinafter abbreviated as a specific carbonate) and a chlorine-containing chain having an unsaturated bond. By using an electrolytic solution in which the content of ether (hereinafter abbreviated as “specific ether”) is not more than a specific amount, the high-temperature storage characteristics are compared with the case of using an electrolytic solution in which the amount of the above compound is out of the range. As a result, the present invention has been completed.

That is, the gist of the present invention resides in the following (1) to (5).
(1) Contains at least metallic lithium, a lithium alloy or a negative electrode containing a material capable of inserting and extracting lithium, a positive electrode containing a material capable of inserting and extracting lithium, a non-aqueous solvent and a lithium salt In the non-aqueous electrolyte solution used for the non-aqueous electrolyte secondary battery composed of the non-aqueous electrolyte solution, the non-aqueous electrolyte solution contains 0.1 to 10% by weight of carbonate having an unsaturated bond, and A nonaqueous electrolytic solution, wherein the content of the compound represented by the following formula (1) is 10 ppm or less.

(In Formula (1), R < ₁ > -R < ₈ > shows a chlorine atom or a hydrogen atom. Moreover, at least one is a chlorine atom among R < ₁ > -R < ₈ >.)
(2) The nonaqueous electrolytic solution according to (1) above, wherein the carbonate having an unsaturated bond is vinylene carbonate.
(3) A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte according to (1) or (2).
(4) The negative electrode material is at least one selected from the group consisting of a carbonaceous material having a d-value of 0.335 to 0.34 nm and / or Sn, Si and Al in the lattice plane (002 plane) in X-ray diffraction The non-aqueous electrolyte secondary battery according to (3) above, comprising an oxide of a metal and / or a lithium alloy.
(5) A purified vinylene carbonate, wherein the content of the compound represented by the following formula (1) is 100 ppm or less.

(In Formula (1), R < ₁ > -R < ₈ > shows a chlorine atom or a hydrogen atom. At least one is a chlorine atom among R < ₁ > -R < ₈ >.)

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous electrolyte secondary battery excellent in the high temperature storage characteristic, the non-aqueous electrolyte used for it, and the vinylene carbonate which gives it can be provided.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not specified by these contents. .
<Non-aqueous electrolyte>
The non-aqueous electrolyte solution of the present invention contains an electrolyte and a non-aqueous solvent that dissolves the electrolyte, as is the case with conventional non-aqueous electrolyte solutions. The nonaqueous electrolytic solution of the present invention contains a specific amount of the specific carbonate and the specific ether.

(Specific carbonate)
The feature of the specific carbonate defined in the present invention is that the raw material contains chlorine, and as a result, the specific ether in the present invention is contained as an impurity. Specific examples of such compounds include vinylene carbonate derivatives such as vinylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate, ethyl vinylene carbonate, and diethyl vinylene carbonate. Among these, vinylene carbonate is preferable.
The production method of vinylene carbonate used in the present invention is not limited, but synthesis of chloroethylene carbonate obtained by chlorination of ethylene carbonate described in Non-Patent Document 1 and Non-Patent Document 2 by dehydrochlorination. The method etc. are mentioned. The vinylene carbonate in the present invention is then subjected to a purification step. The purification method is not particularly limited as long as it can be purified to 10 ppm or less when a specific ether is dissolved in a non-aqueous solvent to form a non-aqueous electrolyte solution. For example, unit operations such as adsorption, precision distillation, and crystallization are performed. Use a combination-purified product.

In addition, it is preferable that the purification operation is performed twice or more, or two or more different purification operations are performed. Examples thereof include crystallization after precision distillation, precision distillation after crystallization, precision distillation twice, crystallization twice, and the like.
The purified vinylene carbonate of the present invention contains 100 ppm or less of the compound represented by the following formula (1).

(In Formula (1), R < ₁ > -R < ₈ > shows a chlorine atom or a hydrogen atom. At least one is a chlorine atom among R < ₁ > -R < ₈ >.)

The content of the compound represented by the formula (1) in the purified vinylene carbonate is more preferably 50 ppm or less, and further preferably 10 ppm or less.
When there is too much content of the compound represented by Formula (1), there exists a possibility that a battery characteristic may deteriorate.
As impurities in the purified vinylene carbonate, it is preferable that the water content is 100 ppm or less and the organic chlorine impurity is 1000 ppm or less, more preferably 500 ppm or less.
The non-aqueous electrolyte solution of the present invention contains 0.1 to 10% by weight of a specific carbonate, preferably 0.5 to 6% by weight, and more preferably 0.5 to 4% by weight.
If the content of the specific carbonate is too large, the battery characteristics may be deteriorated. If the content is too small, the characteristics improving effect may not be exhibited.

(Specific ether)
The specific ether defined in the present invention is represented by the following formula (1).

(In the formula (1), R ₁ to R _8, at least one of .R ₁ to R ₈ which represents a chlorine atom, or a hydrogen atom a chlorine atom.)

The specific ether defined in the present invention is characterized by having both a double bond and a chlorine element in its structure.
Specific examples of the specific ether include:

Is mentioned.
The specific ether is preferably contained in the electrolytic solution in an amount of 10 ppm or less, more preferably 7 ppm or less, more preferably 5 ppm or less because of its effect on storage characteristics. When the amount is larger than this range, various characteristics such as storage characteristics are deteriorated.
A high-purity specific carbonate that does not substantially contain the specific ether may be used, but from the viewpoint of purification cost and the like, it is preferable to use one that usually contains 1 ppb or more.

  Among the specific ethers, the ethers shown below are particularly preferable when they are contained in a specific amount in the non-aqueous electrolyte because the secondary battery has good storage characteristics.

(Electrolytes)
As the electrolyte, a lithium salt is usually used. The lithium salt is not particularly limited as long as it is known to be used for this purpose, and any lithium salt can be used. Specific examples include the following.
For example, inorganic lithium salts such as LiPF ₆ and LiBF ₄ ; LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide , Lithium cyclic 1,3-perfluoropropanedisulfonylimide, 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 ( Examples thereof include organic lithium salts such as CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ , lithium difluorooxalatoborate and lithium bis (oxalato) borate.

Among these, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ or LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium difluorooxalatoborate, lithium bis (oxalate) borate are battery performances. From the viewpoint of improvement, LiPF ₆ or LiBF ₄ is particularly preferable.
These lithium salts may be used alone or in combination of two or more.
A preferred example in the case of using two or more types in combination is the combined use of LiPF ₆ and LiBF ₄ , which has an effect of improving cycle characteristics. In this case, the proportion of LiBF _{4 in} the total of both is preferably 0.01% by weight or more, particularly preferably 0.1% by weight or more, preferably 20% by weight or less, particularly preferably 5% by weight or less. is there. If the lower limit is not reached, it may be difficult to obtain the desired effect. If the upper limit is exceeded, battery characteristics after high-temperature storage may be deteriorated.

Another example is the combined use of an inorganic lithium salt and an organic lithium salt. In this case, the proportion of the inorganic lithium salt in the total of both is 70% by weight or more and 99% by weight or less. desirable. Examples of the organic lithium salt include LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium cyclic 1,2-perfluoroethanedisulfonylimide, lithium cyclic 1,3-perfluoropropane disulfonyl. It is preferably any of imide, lithium difluorooxalatoborate, and lithium bis (oxalato) borate. The combined use of both has the effect of suppressing deterioration due to high temperature storage.

When the nonaqueous solvent contains 55% by volume or more of γ-butyrolactone, the lithium salt is preferably LiBF ₄ or LiBF ₄ in combination with another. In this case, LiBF ₄ preferably accounts for 40 mol% or more of the lithium salt. Particularly preferably, the proportion of LiBF _{4 in} the lithium salt is 40 mol% or more and 95 mol% or less, and the remainder is LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium difluorooxalatoborate, and a combination selected from the group consisting of lithium bis (oxalato) borate.

  The concentration of these electrolytes in the non-aqueous electrolyte solution is not particularly limited in order to exhibit the effects of the present invention, but is usually 0.5 mol / liter or more, preferably 0.6 mol / liter or more, more Preferably it is 0.7 mol / liter or more. The upper limit is usually 3 mol / liter or less, preferably 2 mol / liter or less, more preferably 1.8 mol / liter or less, and still more preferably 1.5 mol / liter or less. If the concentration is too low, the electrical conductivity of the electrolyte solution may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, and the battery performance may decrease. .

(Non-aqueous solvent)
The non-aqueous solvent can also be appropriately selected from conventionally known solvents for non-aqueous electrolyte solutions. Examples thereof include cyclic carbonates having no unsaturated bond, chain carbonates, cyclic ethers, chain ethers, cyclic carboxylic acid esters, chain carboxylic acid esters, and phosphorus-containing organic solvents.
Examples of the cyclic carbonates having no carbon-carbon unsaturated bond include alkylene carbonates having an alkylene group having 2 to 4 carbon atoms such as ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate, From the viewpoint of improving battery characteristics, propylene carbonate is preferable, and ethylene carbonate is particularly preferable.

  As the chain carbonates, dialkyl carbonates are preferable, and the number of carbon atoms of the alkyl group constituting each is preferably 1 to 5, particularly preferably 1 to 4. Specifically, for example, symmetric chain alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; asymmetric chain alkyls such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate Examples thereof include dialkyl carbonates such as carbonates. Among these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable from the viewpoint of improving battery characteristics (particularly, high load discharge characteristics).

Examples of cyclic ethers include tetrahydrofuran and 2-methyltetrahydrofuran.
Examples of chain ethers include dimethoxyethane and dimethoxymethane.
Examples of cyclic carboxylic acid esters include γ-butyrolactone and γ-valerolactone.
Examples of chain carboxylic acid esters include methyl acetate, methyl propionate, ethyl propionate, and methyl butyrate.

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.
These may be used alone or in combination of two or more, but it is preferable to use in combination of two or more. For example, it is preferable to use a high dielectric constant solvent such as alkylene carbonates or cyclic carboxylic acid esters in combination with a low viscosity solvent such as dialkyl carbonates or chain carboxylic acid esters.

  One preferable combination of the non-aqueous solvents is a combination mainly composed of alkylene carbonates and dialkyl carbonates. Among them, the total of alkylene carbonates and dialkyl carbonates in the nonaqueous solvent is 70% by volume or more, preferably 80% by volume or more, more preferably 90% by volume or more, and the alkylene carbonates and dialkyl carbonates. The proportion of alkylene carbonate with respect to the sum of the above is 5% or more, preferably 10% or more, more preferably 15% or more, usually 50% or less, preferably 35% or less, more preferably 30% or less, and still more preferably 25 % Or less. Use of a combination of these non-aqueous solvents is preferable because the balance between the cycle characteristics and high-temperature storage characteristics (particularly, the remaining capacity and high-load discharge capacity after high-temperature storage) of a battery produced using the non-aqueous solvent is improved.

  Specific examples of preferable combinations of alkylene carbonates and dialkyl carbonates include 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, Examples include ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, and ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

A combination in which propylene carbonate is further added to a combination of these ethylene carbonate and dialkyl carbonates is also mentioned as a preferable combination.
In the case of containing propylene carbonate, the volume ratio of ethylene carbonate to propylene carbonate is preferably 99: 1 to 40:60, particularly preferably 95: 5 to 50:50. Further, the proportion of propylene carbonate in the whole non-aqueous solvent is usually 0.1% by volume or more, preferably 1% by volume or more, more preferably 2% by volume or more, and the upper limit is usually 20% by volume or less, preferably 8% by volume. The volume% or less, more preferably 5 volume% or less. It is preferable to contain propylene carbonate in this concentration range, since the low temperature characteristics are further excellent while maintaining the combination characteristics of ethylene carbonate and dialkyl carbonates.
Among the combinations of ethylene carbonate and dialkyl carbonates, those containing asymmetric chain alkyl carbonates as dialkyl carbonates are more preferred, especially ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, ethylene carbonate, diethyl carbonate and ethyl. Methyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, which contain ethylene carbonate, symmetric chain alkyl carbonates, and asymmetric chain alkyl carbonates, have a good balance between cycle characteristics and large current discharge characteristics. preferable. Among them, the asymmetric chain alkyl carbonate is preferably ethyl methyl carbonate, and the alkyl group of the alkyl carbonate preferably has 1 to 2 carbon atoms.
Further, the proportion of dimethyl carbonate in the total non-aqueous solvent is usually 10% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, still more preferably 30% by volume or more, and the upper limit is Usually, it is contained in the range of 90% by volume or less, preferably 80% by volume or less, more preferably 75% by volume or less, and still more preferably 70% by volume or less, since the load characteristics of the battery are improved.

The proportion of ethyl methyl carbonate in the total non-aqueous solvent is usually 10% by volume or more, preferably 20% by volume or more, more preferably 25% by volume or more, more preferably 30% by volume or more, and the upper limit is In general, when it is contained within the range of 90% by volume or less, preferably 80% by volume or less, more preferably 75% by volume or less, and further preferably 70% by volume or less, the balance between the cycle characteristics and storage characteristics of the battery is good. Therefore, it is preferable.
In addition, in the combination mainly composed of the alkylene carbonates and dialkyl carbonates, other solvents may be mixed, and in order to exhibit the effects of the present invention, there is no particular limitation, but load characteristics are emphasized. In some cases, it is preferable not to contain cyclic carboxylic acid esters.

Other examples of preferable non-aqueous solvents include one organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, γ-butyrolactone and γ-valerolactone, or two or more organic solvents selected from the group The mixed solvent becomes 60% by volume or more of the whole. The non-aqueous electrolyte using this mixed solvent is less likely to evaporate or leak when used at high temperatures.
Among them, the total of ethylene carbonate and γ-butyrolactone in the nonaqueous solvent is preferably 80% by volume or more, more preferably 90% by volume or more, and the volume ratio of ethylene carbonate and γ-butyrolactone is 5: 95-45: 55, or the total of ethylene carbonate and propylene carbonate in the non-aqueous solvent is preferably 80% by volume or more, more preferably 90% by volume or more, and the capacity of ethylene carbonate and propylene carbonate. When a material having a ratio of 30:70 to 60:40 is used, the balance between cycle characteristics and high-temperature storage characteristics is generally improved.

(Additive)
The nonaqueous electrolytic solution of the present invention preferably contains various additives as long as the effects of the present invention are not significantly impaired. As the additive, conventionally known additives can be arbitrarily used, and one kind may be used alone, or two or more kinds may be used in any combination and ratio. Examples of the additive include an overcharge inhibitor and an auxiliary agent for improving capacity maintenance characteristics and cycle characteristics after high-temperature storage.

  Examples of the overcharge inhibitor include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran; 2-fluoro Partially fluorinated products of the aromatic compounds such as biphenyl, 2,4-difluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2-fluoroanisole, 3-fluoroanisole, 2,4-difluoroanisole, 2, Fluorinated anisole compounds such as 5-difluoroanisole and 2,6-difluoroaniol; carbonates having a phenyl group such as methylphenyl carbonate, ethylphenyl carbonate and diphenyl carbonate; acetic acid Phosphoric acid esters having a phenyl group such as triphenyl phosphate; Eniru, phenyl propionate, methyl benzoate, carboxylic acid ester having a phenyl group such as ethyl benzoate.

In addition, an overcharge inhibiting agent may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
Further, when the non-aqueous electrolyte contains an overcharge inhibitor, the concentration thereof is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.1% by weight to 5% by weight with respect to the whole non-aqueous electrolyte. %. By including an overcharge inhibitor in the non-aqueous electrolyte, it is possible to suppress rupture and ignition of the non-aqueous electrolyte secondary battery due to overcharge, and the safety of the non-aqueous electrolyte secondary battery is improved. preferable.

  On the other hand, as an auxiliary for improving capacity retention characteristics and cycle characteristics after high temperature storage, for example, carbonate compounds other than those corresponding to specific carbonates such as erythritan carbonate and spirobisdimethylene carbonate; succinic anhydride , Such as glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, diglycolic anhydride, cyclohexanedicarboxylic anhydride, cyclopentanetetracarboxylic dianhydride, phenylsuccinic anhydride Anhydrides: ethylene sulfite, 1,3-propane sultone, 1,4-butane sultone, methyl methanesulfonate, busulfan, sulfolane, sulfolene, dimethyl sulfone, diphenyl sulfone, methyl phenyl sulfone, dibutyl disulfide, dicyclo Sulfur-containing compounds such as xyldisulfide, tetramethylthiuram monosulfide, N, N-dimethylmethanesulfonamide and N, N-diethylmethanesulfonamide; 1-methyl-2-pyrrolidinone, 1-methyl-2-piperidone, Nitrogen-containing compounds such as 3-methyl-2-oxazolidinone, 1,3-dimethyl-2-imidazolidinone and N-methylsuccinimide; hydrocarbon compounds such as heptane, octane and cycloheptane, fluorobenzene, difluorobenzene, And fluorine-containing aromatic compounds such as benzotrifluoride.

In addition, an auxiliary agent may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
The ratio of these auxiliaries in the non-aqueous electrolyte solution is not particularly limited in order to exhibit the effects of the present invention, but is usually 0.01% by weight or more, preferably 0.1% by weight or more, particularly preferably. Is 0.2% by weight or more, and the upper limit is usually 5% by weight or less, preferably 3% by weight or less, and particularly preferably 1% by weight or less. By adding these auxiliaries, capacity maintenance characteristics and cycle characteristics after high temperature storage can be improved. If the concentration is lower than this lower limit, the effect of the auxiliary agent may be hardly exhibited. On the other hand, if the concentration is too high, battery characteristics such as high load discharge characteristics may deteriorate.

(Preparation of electrolyte)
The non-aqueous electrolyte solution according to the present invention can be prepared by dissolving an electrolyte and, if necessary, other compounds in a non-aqueous solvent. In preparing the non-aqueous electrolyte solution, each raw material is preferably dehydrated in advance in order to reduce the water content when the electrolyte solution is used. Usually, it is good to dehydrate to 50 ppm or less, preferably 30 ppm or less, particularly preferably 10 ppm or less. Moreover, you may implement dehydration, a deoxidation process, etc. after electrolyte solution preparation.
The non-aqueous electrolyte of the present invention is suitable for use as a secondary battery among non-aqueous electrolyte batteries, that is, as an electrolyte for a non-aqueous electrolyte secondary battery, for example, a lithium secondary battery. Hereinafter, a non-aqueous electrolyte secondary battery using the electrolyte of the present invention will be described.

<Non-aqueous electrolyte secondary battery>
The non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte battery including a negative electrode and a positive electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte, and the non-aqueous electrolyte is the above-described electrolyte. It is characterized by being.
(Battery configuration)
The non-aqueous electrolyte secondary battery according to the present invention is the same as the conventionally known non-aqueous electrolyte secondary battery except that it is produced using the electrolyte of the present invention, and a negative electrode capable of inserting and extracting lithium ions and A non-aqueous electrolyte battery including a positive electrode and a non-aqueous electrolyte solution, usually obtained by housing the positive electrode and the negative electrode in a case through a porous membrane impregnated with the non-aqueous electrolyte solution according to the present invention. . Therefore, the shape of the secondary battery according to 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.

(Negative electrode)
As the negative electrode active material, a carbonaceous material or metal compound capable of inserting and extracting lithium, lithium metal, lithium alloy, and the like can be used. These negative electrode active materials may be used alone or in combination of two or more. Among these, a carbonaceous material and a metal compound capable of occluding and releasing lithium are preferable.
Among the carbonaceous materials, graphite and graphite whose surface is coated with amorphous carbon as compared with graphite are particularly preferable.
Graphite preferably has a lattice plane (002 plane) d value (interlayer distance) of 0.335 to 0.338 nm, particularly 0.335 to 0.337 nm, as determined by X-ray diffraction using the Gakushin method. 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. or more, usually 25.0 m ² / g or less, preferably 20.0 m ² / g, more preferably 15.0 m ² / g or less, and most preferably 10.0 m ² / g or less.

Further, the carbonaceous material is analyzed by Raman spectrum using argon ion laser light, the peak of the peak PB in the peak intensity of the peak PA in the range of 1570~1620cm ^-1 IA, a range of 1300～1400Cm ^-1 When the strength is IB, it is preferable that the R value (= IB / IA) represented by the ratio of IB and IA is in the range of 0.01 to 0.7. Further, the half-value width of the peak in the range of 1570～1620Cm ^-1 is typically 26cm ^-1 or less, are preferred in particular 25 cm ^-1 or less.

  Examples of metal compounds capable of inserting and extracting lithium include compounds containing metals such as Ag, Zn, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi, Cu, Ni, Sr, and Ba. These metals are used as simple substances, oxides, alloys with lithium, and the like. In the present invention, those containing an element selected from Si, Sn, Ge and Al are preferred, and oxides or lithium alloys of metals selected from Si, Sn and Al are more preferred. These may be in the form of powder or thin film, and may be crystalline or amorphous.

Lithium is a metal compound that can occlude and release lithium, or its oxides and alloys with lithium generally have higher capacity per unit weight than carbonaceous materials typified by graphite. It is suitable for a secondary battery.
The average particle size of the metal compound capable of occluding and releasing lithium or the oxide or an alloy thereof with lithium is not particularly limited to express the effect of the present invention, but is usually 50 μm or less, preferably 20 μm or less, Particularly preferably, it is 10 μm or less, usually 0.1 μm or more, preferably 1 μm or more, particularly preferably 2 μm or more. When this upper limit is exceeded, the expansion of the electrode increases, and the cycle characteristics may deteriorate. Moreover, when less than this minimum, it becomes difficult to collect current and there is a possibility that the capacity is not sufficiently developed.

(Positive electrode)
Examples of the positive electrode active material include materials capable of inserting and extracting lithium, such as lithium transition metal composite oxide materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide. These compounds are Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _{1 -y My} O ₂ , Li _x Ni _{1 -y My} O ₂ , Li _x Mn _{1 -y My} O ₂ etc., where M is usually at least one selected from Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, V, Sr, Ti, 0.4 and what is ≦ x ≦ 1.2,0 ≦ y ≦ 0.6 , Li X Mn a Ni b Co c O 2 ( where, 0.4 ≦ x ≦ 1.2, a + b + c = 1) is Can be mentioned.
Especially represented by _{Li X Co 1-y M y} O 2, Li X Ni 1-y M y O 2, Li X Mn 1-y M y O 2 , etc., cobalt, nickel, and other part of manganese The structure replaced with a metal or Li _x Mn _a Ni _b CocO ₂ (where 0.4 ≦ x ≦ 1.2, a + b + c = 1, | ab | <0.1) It is preferable because it can be stabilized.

The positive electrode active materials may be used alone or in combination.
In addition, a material in which a substance having a composition different from that of the substance constituting the main cathode active material is attached to the surface of the cathode active material can be used. Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate And sulfates such as aluminum sulfate and carbonates such as lithium carbonate, calcium carbonate and magnesium carbonate.

  The amount of the surface adhering substance is not particularly limited in order to exhibit the effects of the present invention, but is preferably 0.1 ppm or more, more preferably 1 ppm or more as a lower limit in terms of mass with respect to the positive electrode active material. The upper limit is preferably 10 ppm or more, preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less. The surface adhering substance can suppress the oxidation reaction of the non-aqueous electrolyte solution on the surface of the positive electrode active material, and can improve the battery life. However, when the amount of the adhering quantity is too small, the effect is not sufficiently exhibited. If the amount is too large, the resistance may increase in order to inhibit the entry and exit of lithium ions.

(electrode)
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 electrolytic solution used during electrode production. For example, fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene, polyolefins such as polyethylene and polypropylene, polymers having unsaturated bonds such as styrene / butadiene rubber, isoprene rubber and butadiene rubber, and copolymers thereof, ethylene / acrylic Examples thereof include acrylic acid polymers such as acid copolymers and ethylene / methacrylic acid copolymers, and copolymers thereof.

The electrode may contain a thickener, a conductive material, a filler and the like in order to increase 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 a metal material such as copper or nickel, and a carbon material such as graphite or carbon black.

The electrode may be manufactured by 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.
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, more preferably 1.60 g. / Cm ³ or more, particularly preferably 1.65 g / cm ³ or more.

The density of the positive electrode active material layer after drying and pressing is usually 2.0 g / cm ³ or more, preferably 2.5 g / cm 3 or more, more preferably 3.0 g / cm ³ or more.
Various types of current collectors can be used, but metals and alloys are usually used. Examples of the current collector for the negative electrode include copper, nickel, and stainless steel, and copper is preferred. Examples of the positive electrode current collector include metals such as aluminum, titanium, and tantalum, and alloys thereof, and aluminum or an alloy thereof is preferable.

(Separator, exterior body)
A porous film (separator) is interposed between the positive electrode and the negative electrode to prevent a short circuit. In this case, the electrolytic solution is used by impregnating the porous membrane. The material and shape of the porous film are not particularly limited as long as it is stable to the electrolytic solution and excellent in liquid retention, and a porous sheet or nonwoven fabric made of a polyolefin such as polyethylene or polypropylene is preferable.
The material of the battery casing used in the battery according to the present invention is also arbitrary, and nickel-plated iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, a laminate film, or the like is used.
The operating voltage of the non-aqueous electrolyte secondary battery of the present invention described above is usually in the range of 2V to 6V.

Hereinafter, specific examples of the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless it exceeds the gist.
[Detection of specific ethers]
Analysis of the total of the specific ethers represented by the formula (1) (hereinafter abbreviated as specific ether group) was performed by gas chromatography (GC2014, manufactured by Shimadzu Corporation; column TC5HT; manufactured by GL Sciences; 50 ° C to 10 ° C / min 250 The temperature was raised to 0 ° C. and held for 3 minutes; both injection and detector (FID) were 250 ° C.). The detection limit of the specific ether group is 0.5 GC area ppm.

[Synthesis of vinylene carbonate]
According to the method described in Non-Patent Document 1 and Non-Patent Document 2, vinylene carbonate represented by the following formula (2) was produced (crude vinylene carbonate 10.0 kg).
1 kg of crude vinylene carbonate was subjected to precision distillation (3 theoretical plates, reflux ratio 10) twice to obtain 850 g (VC-1) of purified vinylene carbonate. The purity of the obtained purified vinylene carbonate was 98.88 area%, the total chlorine was 2916 ppm by weight, and the specific ether group was 597 GC area ppm.

  1 kg of crude vinylene carbonate was charged with MTBE / hexane = 1/1 wt ratio (2 kg), cooled and stirred for crystallization, the precipitated solid was filtered off, and precision distilled (3 theoretical plates, reflux ratio 10). The crystallization solvent was distilled off and the vinylene carbonate was distilled to obtain 905 g (VC-2) of purified vinylene carbonate. The purity of the obtained purified vinylene carbonate was 99.97 area%, the total chlorine was 29 ppm by weight, and the specific ether group was 6 GC area ppm.

1 kg of crude vinylene carbonate was charged with MTBE / hexane = 1/1 wt ratio (2 kg), cooled with stirring, crystallized, the precipitated solid was filtered off, and the crystallization operation was repeated twice, followed by precision distillation (Theoretical plate number: 3 and reflux ratio: 10), the crystallization solvent was distilled off, and vinylene carbonate was distilled to obtain 810 g of vinylene carbonate (VC-3). The purity of the obtained purified vinylene carbonate was 99.99 area% or more, the total chlorine was 1 ppm by weight or less, and the specific ether group was 0.5 GC area ppm or less.
The purified vinylene carbonates (VC-1 to VC-3) obtained above were mixed to prepare vinylene carbonates (VC-4 to VC-7) having different specific ether contents.
The analysis results of VC-1 to VC-7 are shown in Table 1.

[Capacity evaluation]
A lithium secondary battery is charged to 4.2 V at a constant current corresponding to 0.2 C at 25 ° C. in a state of being sandwiched between glass plates in order to enhance adhesion between electrodes, and then a constant current of 0.2 C Was discharged to 3V. This is done for 3 cycles to stabilize the battery. In the 4th cycle, after charging to 4.2V with a constant current of 0.5C, charging is performed until the current value reaches 0.05C with a constant voltage of 4.2V. The initial discharge capacity was determined by discharging to 3 V at a constant current of 0.2C.
Here, 1C represents a current value for discharging the reference capacity of the battery in one hour, and 0.2C represents a current value of 1/5 thereof.

[Evaluation of high-temperature storage characteristics]
The battery for which the capacity evaluation test has been completed is charged to 4.2 V at a constant current of 0.5 C at 25 ° C., and then charged to a current value of 0.05 C at a constant voltage of 4.2 V, and then at 85 ° C. Stored for 1 day. Next, after measuring the open circuit voltage (OCV) of the battery, the discharge capacity after storage test was measured by discharging to 25V at a constant current of 0.2 C to 3 V, and the discharge capacity after storage relative to the initial discharge capacity was measured. The ratio was determined, and this was defined as the remaining capacity (%) after high-temperature storage.

Example 1
[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 R value (= I _B / I _A ) determined from Raman spectrum analysis using argon ion laser light is 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, dried, and then pressed to obtain a negative electrode active material layer having a density of 1.65 g / cm ³ to form a negative electrode.

[Production of positive electrode]
90 parts by weight of LiCoO ₂ , 4 parts by weight of carbon black and 6 parts by weight of polyvinylidene fluoride (manufactured 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 a 15 μm thick aluminum foil, the positive electrode active material layer was pressed to a density of 3.0 g / cm ³ to obtain a positive electrode.

[Manufacture of electrolyte]
In a dry argon atmosphere, the vinylene carbonate (VC-2) obtained in the above [Synthesis of vinylene carbonate] was mixed with a mixture of ethylene carbonate, ethylmethyl carbonate and dimethyl carbonate (volume ratio 2: 3: 5). The content was 2% by weight, and then sufficiently dried LiPF ₆ was dissolved at a rate of 1.0 mol / liter to obtain an electrolytic solution.

[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 prepare 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 then the electrolyte was poured into the bag and vacuum sealed. The sheet-shaped battery was manufactured and the high-temperature storage characteristics were evaluated.
The evaluation results are shown in Table-2.

(Examples 2 to 6)
In the electrolytic solution of Example 1, instead of purified vinylene carbonate (VC-2), purified vinylene carbonate (VC-3 to VC-7) was used, respectively. Batteries were prepared and evaluated for high-temperature storage characteristics. The evaluation results are shown in Table-2.

(Comparative Example 1)
In the electrolytic solution of Example 1, a sheet-like lithium secondary battery was produced in the same manner as in Example 1 except that purified vinylene carbonate (VC-1) was used instead of purified vinylene carbonate (VC-2). The high temperature storage characteristics were evaluated. The evaluation results are shown in Table-2.
(Comparative Example 2)
A sheet-like lithium secondary battery was prepared in the same manner as in Example 1 except that vinylene carbonate was not used for the electrolytic solution, and the high-temperature storage characteristics were evaluated. The evaluation results are shown in Table-2.

  As is clear from Table-2, it can be seen that the battery according to the present invention has a high OCV and remaining capacity after high-temperature storage, and excellent storage characteristics.

  The non-aqueous electrolyte solution of the present invention can be applied to a non-aqueous electrolyte secondary battery excellent in high-temperature storage characteristics.

Claims (5)

A negative electrode containing at least metal lithium, a lithium alloy or a material capable of inserting and extracting lithium, a positive electrode containing a material capable of inserting and extracting lithium, a non-aqueous solvent and a lithium salt In a non-aqueous electrolyte solution used for a non-aqueous electrolyte secondary battery composed of a non-aqueous electrolyte solution, the non-aqueous electrolyte solution contains 0.1 to 10% by weight of carbonate having an unsaturated bond, and the following formula A nonaqueous electrolytic solution, wherein the content of the compound represented by (1) is 10 ppm or less.

(In Formula (1), R < ₁ > -R < ₈ > shows a chlorine atom or a hydrogen atom. Moreover, at least one is a chlorine atom among R < ₁ > -R < ₈ >.) The non-aqueous electrolyte solution according to claim 1, wherein the carbonate having an unsaturated bond is vinylene carbonate. A non-aqueous electrolyte secondary battery using the non-aqueous electrolyte according to claim 1. The negative electrode material is a carbonaceous material having a d-value of 0.335 to 0.34 nm on the lattice plane (002 plane) in X-ray diffraction and / or at least one metal selected from the group consisting of Sn, Si and Al The non-aqueous electrolyte secondary battery according to claim 3, comprising an oxide and / or a lithium alloy. A purified vinylene carbonate, wherein the content of the compound represented by the following formula (1) is 100 ppm or less.

(In Formula (1), R < ₁ > -R < ₈ > shows a chlorine atom or a hydrogen atom. At least one is a chlorine atom among R < ₁ > -R < ₈ >.)