JP2005166553A - Nonaqueous electrolytic for lithium ion secondary battery, and the lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery restraining expansion of sheath material, by restraining generation of gas at continuous charging, and superior in discharging properties, after continuous charging. <P>SOLUTION: The nonaqueous electrolytic solution for the lithium ion secondary battery, containing an electrolyte and a nonaqueous solvent, contains at least a kind of vinylene carbonate compound expressed by general Formula (I) and at least a kind of vinyl ethylene sulfite compound expressed by general Formula (II). In the general Formula (I), R<SB>1</SB>and R<SB>2</SB>are respectively independent and they are 1-4C alkyl groups in which either a hydrogen atom, a halogen atom or one or more hydrogen atoms may be substituted by halogen atom. In the general Formula (II), R<SB>3</SB>, R<SB>4</SB>, R<SB>5</SB>, R<SB>6</SB>, R<SB>7</SB>, and R<SB>8</SB>are respectively independent, and they are 1-4C alkyl groups which may contain hydrogen atoms or substituted groups. The lithium ion secondary battery uses the nonaqueous lithium ion secondary electrolyte. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte for a lithium ion secondary battery and a lithium ion secondary battery using the same. Specifically, a non-aqueous electrolyte for a lithium ion secondary battery capable of producing a lithium ion secondary battery that suppresses gas generation during continuous charging and has excellent discharge characteristics after continuous charging, and the lithium ion secondary battery The present invention relates to a lithium ion secondary battery using a non-aqueous electrolyte for a battery.

  Currently, lithium ion secondary batteries are commercialized as non-aqueous electrolyte secondary batteries for portable devices such as mobile phones and notebook computers. In recent years, as portable devices have been made thinner, it has been desired to further reduce the thickness of batteries built into these devices. For this purpose, it is necessary to reduce the thickness of the battery outer packaging material. However, when the thickness of the battery outer packaging material is reduced, phenomena such as gas generation inside the battery and temperature rise directly cause deformation of the battery, gas ejection. In order to ensure safety, it is necessary to suppress gas generation and temperature rise inside the battery as much as possible. In particular, suppression of gas generation when the charged state continues for a long time is important.

In Patent Document 1, in a lithium ion secondary battery, for the purpose of improving flame retardancy and cycle characteristics, triphenyl phosphate and diphenyl monobutyl phosphate as flame retardant imparting agents, and further as a negative electrode interface film forming agent An example using three compounds such as vinyl ethylene carbonate (VEC) as an additive is shown. Further, it has been suggested that two kinds of compounds, monoamyl diphenyl phosphate as a flame retardant imparting agent and vinyl ethylene sulfite as a negative electrode interface film forming agent, are used as additives.
US2003 / 0157413A1

  However, when the additive of Patent Document 1 is used, the flame retardancy and cycle characteristics are effective, but the battery characteristics after continuous charging are not sufficient.

  The present invention has been made in view of such problems, and suppresses gas generation during continuous charging, thereby suppressing swelling of the outer packaging material and excellent discharge characteristics after continuous charging. The purpose is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors, as additives for a non-aqueous electrolyte for a lithium ion secondary battery, include a vinylene carbonate compound and a vinyl ethylene sulfite compound, which are negative electrode interface film forming agents. It has been found that by using in combination, it is possible to produce a lithium ion secondary battery that suppresses gas generation during continuous charging and has excellent discharge characteristics after continuous charging, and has completed the present invention.

  That is, the gist of the present invention is that in a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent, at least one vinylene carbonate compound represented by the following general formula (I) and at least represented by the following general formula (II): It exists in the non-aqueous electrolyte solution for lithium ion secondary batteries containing 1 type of vinyl ethylene sulfite compound.

（式中、Ｒ₁、Ｒ₂は、それぞれ独立して、水素原子、ハロゲン原子、又は１個以上の水素原子がハロゲン原子で置換されていても良い炭素数１〜４のアルキル基である。）

Wherein R ₁ and R ₂ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms in which one or more hydrogen atoms may be substituted with a halogen atom. )

（式中、Ｒ₃、Ｒ₄、Ｒ₅、Ｒ₆、Ｒ₇及びＲ₈は、それぞれ独立して、水素原子又は置換基を有していても良い炭素数１〜４のアルキル基である。）

Wherein R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent. .)

  Another gist of the present invention resides in a lithium ion secondary battery using such a non-aqueous electrolyte for a lithium ion secondary battery of the present invention.

  Although the details of the effects of the present invention are not clear, by using the vinylene carbonate compound and the vinyl ethylene sulfite compound in combination, the vinylene carbonate compound and the vinyl ethylene sulfite compound that are relatively stable even during continuous charging. It is considered that a composite coating is formed on the negative electrode surface, thereby suppressing gas generation during continuous charging and improving discharge characteristics after continuous charging.

  In the present invention, the content of the vinyl ethylene sulfite compound is 0.01 to 5% by weight with respect to the total weight of the non-aqueous electrolyte solution, and the content of the vinylene carbonate compound is equal to the total weight of the non-aqueous electrolyte solution. The content ratio of the vinylene carbonate compound and the vinyl ethylene sulfite compound in the nonaqueous electrolytic solution is preferably 99: 1 to 1:99.

  As the vinylene carbonate compound, vinylene carbonate is particularly preferable, and as the vinyl ethylene sulfite compound, 4-vinyl ethylene sulfite is particularly preferable.

  According to the non-aqueous electrolyte solution for a lithium ion secondary battery of the present invention, it is possible to produce a lithium ion secondary battery that suppresses gas generation during continuous charging and has excellent discharge characteristics after continuous charging.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following descriptions, and various modifications can be made within the scope of the gist.

  The non-aqueous electrolyte for a lithium ion secondary battery of the present invention is a non-aqueous electrolyte containing an electrolyte and a non-aqueous solvent, and includes at least one vinylene carbonate compound represented by the following general formula (I), It contains at least one vinylethylene sulfite compound represented by the general formula (II).

（式中、Ｒ₁、Ｒ₂は、それぞれ独立して、水素原子、ハロゲン原子、又は１個以上の水素原子がハロゲン原子で置換されていても良い炭素数１〜４のアルキル基である。）

Wherein R ₁ and R ₂ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms in which one or more hydrogen atoms may be substituted with a halogen atom. )

（式中、Ｒ₃、Ｒ₄、Ｒ₅、Ｒ₆、Ｒ₇及びＲ₈は、それぞれ独立して、水素原子又は置換基を有していても良い炭素数１〜４のアルキル基である。）

Wherein R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent. .)

  First, the vinylene carbonate compound and the vinyl ethylene sulfite compound contained in the non-aqueous electrolyte solution of the present invention will be described.

In the general formula (I), R ₁ and R ₂ are each independently a hydrogen atom, a halogen atom, or an alkyl having 1 to 4 carbon atoms in which one or more hydrogen atoms may be substituted with a halogen atom. As the halogen atom for R ₁ and R _2, a fluorine atom, a chlorine atom and the like are particularly preferable. When R ₁ and R ₂ are an alkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group, An n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group are exemplified, and a methyl group and an ethyl group are particularly preferable. In addition, when these alkyl groups are substituted with a halogen atom, there are no particular restrictions on the number of substitutions and the substitution position. Examples of such haloalkyl groups include monofluoromethyl groups, difluoromethyl groups, and trifluoromethyl groups. And a trifluoroethyl group.

  Examples of the vinylene carbonate compound represented by the general formula (I) include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, fluoro vinylene carbonate, Trifluoromethyl vinylene carbonate and the like can be mentioned, but vinylene carbonate, 4,5-dimethyl vinylene carbonate, fluoro vinylene carbonate and trifluoromethyl vinylene carbonate are preferable, and vinylene carbonate is particularly preferable. These vinylene carbonate compounds may be used alone or in combination of two or more.

  The content of the vinylene carbonate compound is usually 0.01% by weight or more, preferably 0.1% by weight or more, usually 10% by weight or less, preferably 5% by weight or less based on the total weight of the non-aqueous electrolyte solution. . If the lower limit is not reached, a film at the negative electrode interface is not sufficiently formed, and various characteristics of the battery are liable to be reduced. If the upper limit is exceeded, the amount of gas generated due to decomposition increases, resulting in other battery characteristics. It is easy to invite a decline.

  In addition, the vinylene carbonate compound can be used in combination of two or more kinds as long as the range of the effect of the present invention is not exceeded, but even when two or more kinds are used in combination, the total amount of the vinylene carbonate compound is The total amount of 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 5% by weight or less.

In the said general formula (II), R < ₃ >, R < ₄ >, R < ₅ >, R < ₆ >, R < ₇ > and R <_8> are each independently C1-C4 which may have a hydrogen atom or a substituent. It is an alkyl group. When R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are alkyl groups having 1 to 4 carbon atoms, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl Group, sec-butyl group, and tert-butyl group are preferable, and methyl group and ethyl group are particularly preferable. Examples of the substituent that these alkyl groups may have include an ether group, a carbonyl group, a carboxyl group, and a carbamoyl group, and particularly preferably a methoxy group, an ethoxy group, an acetyl group, a methoxycarbonyloxy group, a methoxycarbonyl group, N, N-dimethylcarbamoyl group may be mentioned.

  Examples of the vinyl ethylene sulfite compound represented by the general formula (II) include 4-vinyl ethylene sulfite, 4- (1-propenyl) -ethylene sulfite, and 4- (2-propenyl) -ethylene sulfite. Phyto, 4- (2-methyl-2-propenyl) -ethylene sulfite, 4- (1-butenyl) -ethylene sulfite, 4-methyl-4-vinylethylene sulfite, 4-ethyl-4-vinylethylenesulfite Phyto, 4-n-propyl-4-vinylethylene sulfite, 5-methyl-4-vinylethylene sulfite and the like are mentioned, but 4-vinylethylene sulfite, 4-methyl-4-vinylethylene sulfite are preferable. 4-vinylethylene sulfite is particularly preferred. These vinylethylene sulfite compounds may be used alone or in combination of two or more.

  The content of the vinyl ethylene sulfite compound is usually 0.01% by weight or more, preferably 0.1% by weight or more, usually 5% by weight or less, preferably 3% by weight, based on the total weight of the non-aqueous electrolyte. It is as follows. If the lower limit is not reached, the effect of suppressing gas generation after continuous charging tends to be low, and if the upper limit is exceeded, film formation proceeds excessively, which tends to adversely affect other characteristics of the battery.

  Also, the vinyl ethylene sulfite compound can be used in combination of two or more kinds as long as the range of the effect of the present invention is not exceeded. The total amount of the compound is usually 0.01% by weight or more, preferably 0.1% by weight or more, usually 5% by weight or less, preferably 3% by weight or less based on the total weight of the non-aqueous electrolyte solution. To do.

  Furthermore, the total content of the vinylene carbonate compound and the vinyl ethylene sulfite compound is usually 0.02% by weight or more, preferably 0.2% by weight or more, and usually 15% by weight, based on the total weight of the non-aqueous electrolyte. Hereinafter, it is preferably 8% by weight or less. If the total content of the vinylene carbonate compound and the vinyl ethylene sulfite compound is within this range, it is considered that a composite coating derived from the vinylene carbonate compound and the vinyl ethylene sulfite compound is formed on the negative electrode surface from the initial charging. The composite coating is presumed to be relatively stable even during continuous charging. As a result, gas generation during continuous charging is suppressed, and discharge characteristics after continuous charging can be improved. It is done.

  Further, the content ratio of the vinylene carbonate compound and the vinylethylene sulfite compound in the non-aqueous electrolyte is usually 99.9: 0.1 to 0.1: 99.9, preferably 99: 1 to 1:99. . If the relative proportion of the vinylene carbonate compound exceeds this range, there is a risk that suppression of gas generation and continuous improvement of discharge characteristics during continuous charging with the vinylethylene sulfite compound may not be observed. Although suppression of this is recognized, there is a possibility that the discharge characteristics after continuous charging may deteriorate.

  Next, the nonaqueous solvent used in the present invention will be described.

  There is no restriction | limiting in particular in the kind of nonaqueous solvent used by this invention, Arbitrary nonaqueous solvents can be used. Specific examples include cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, cyclic esters such as γ-butyrolactone and γ-valerolactone, methyl acetate, and propionic acid. Examples include chain esters such as methyl, cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and tetrahydropyran, chain ethers such as dimethoxyethane and dimethoxymethane, and sulfur-containing organic solvents such as sulfolane and diethylsulfone. It is done. These non-aqueous solvents may be used alone or in combination of two or more in any combination and ratio.

As a non-aqueous solvent,
(1) Combination of cyclic carbonate and chain carbonate
(2) Combination of cyclic carbonate and cyclic ester
(3) Combination of cyclic ester and chain ester
(4) A combination of a cyclic carbonate and a cyclic carbonate is preferable from the viewpoint of dissociation of lithium salt of the electrolyte and electrical conductivity. Preferably, the combination is mixed so that the volume of the nonaqueous solvent is 70% by volume or more. A non-aqueous solvent is preferable from the viewpoint of improving overall battery performance such as charge / discharge characteristics and battery life.

  Specific examples of the cyclic carbonate, the chain carbonate, the cyclic ester, and the chain ester used in the above combinations (1) to (4) include the following.

[Cyclic carbonate]
An alkylene carbonate having 2 to 4 carbon atoms in the alkylene group is preferred. Specific examples thereof include ethylene carbonate, propylene carbonate, butylene carbonate and the like. Of these, ethylene carbonate and propylene carbonate are preferable. One of these may be used alone, or a plurality of these may be used in any combination and ratio.

[Chain carbonate]
A chain carbonate (dialkyl carbonate) having 1 to 4 carbon atoms in the alkyl group is preferred. Specific examples thereof include dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, ethyl methyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate and the like. Of these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable. One of these may be used alone, or a plurality of these may be used in any combination and ratio.

[Cyclic ester]
Cyclic esters having 5 to 7-membered rings are preferred. Specific examples thereof include γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone, α-acetyl-γ-butyrolactone, and the like. Of these, γ-butyrolactone and γ-valerolactone are preferable. One of these may be used alone, or a plurality of these may be used in any combination and ratio.

[Chain esters]
A chain ester having an alkyl group with a total carbon number of 3 to 8 is preferred. Specific examples thereof include methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, methyl propionate, ethyl propionate, n-propyl propionate, isopropyl propionate, n-butyl propionate, butyric acid. Examples thereof include methyl, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, and n-butyl butyrate. Of these, ethyl acetate, methyl propionate, and ethyl propionate are preferable. One of these may be used alone, or a plurality of these may be used in any combination and ratio.

  In the example (1), the combination of the cyclic carbonate and the chain carbonate is each alone, and contains 10% by volume or more with respect to the total volume of the non-aqueous electrolyte, and the total of these volumes is the non-aqueous electrolyte. A mixed non-aqueous solvent mixed so as to be 70% by volume or more with respect to the total volume is preferable from the viewpoint of improving overall battery performance such as charge / discharge characteristics and battery life.

  The mixed nonaqueous solvent may contain a solvent other than the cyclic carbonate and the chain carbonate as long as the battery performance of the manufactured lithium ion secondary battery is not deteriorated. The ratio of the solvent other than the cyclic carbonate and the chain carbonate in the nonaqueous electrolytic solution is usually 30% by volume or less, preferably 10% by volume or less.

  In the example (2), the combination of the cyclic carbonate and the cyclic ester is a simple substance, and it contains 10% by volume or more based on the total volume of the non-aqueous electrolyte, and the content of the cyclic ester is that of the non-aqueous electrolyte. It is preferable that it is 50 volume% or more with respect to the total volume. Moreover, the mixed non-aqueous solvent mixed so that the sum total of those volumes may be 70 volume% or more with respect to a non-aqueous electrolyte is preferable from a viewpoint of improving battery performance in general, such as a charge / discharge characteristic and battery life.

  The mixed non-aqueous solvent may contain a solvent other than the cyclic carbonate and the cyclic ester as long as the battery performance of the manufactured lithium ion secondary battery is not deteriorated. Specific examples thereof include the chain carbonates exemplified above. The proportion of the solvent other than the cyclic carbonate and cyclic ester in the nonaqueous electrolytic solution is usually 30% by volume or less, preferably 10% by volume or less.

  In the example (3), the combination of the cyclic carbonate and the chain ester is each alone, and it contains 10% by volume or more with respect to the total volume of the non-aqueous electrolyte, and the total of these volumes is the non-aqueous electrolyte. A mixed non-aqueous solvent mixed so as to be 70% by volume or more with respect to the total volume is preferable from the viewpoint of improving overall battery performance such as charge / discharge characteristics and battery life.

  The mixed non-aqueous solvent may contain a solvent other than the cyclic carbonate and the chain ester as long as the battery performance of the manufactured lithium ion secondary battery is not deteriorated. The ratio of the solvent other than the cyclic carbonate and the chain ester in the nonaqueous electrolytic solution is usually 30% by volume or less, preferably 10% by volume or less.

  In the combination of cyclic carbonate and cyclic carbonate in the above example (4), each is contained alone, containing 10% by volume or more with respect to the total volume of the non-aqueous electrolyte solution, and the total of these volumes is that of the non-aqueous electrolyte solution. A mixed non-aqueous solvent mixed so as to be 70% by volume or more of the total volume is preferable from the viewpoint of improving overall battery performance such as charge / discharge characteristics and battery life.

  The mixed non-aqueous solvent may contain a solvent other than the cyclic carbonate as long as the battery performance of the manufactured lithium ion secondary battery is not deteriorated. The ratio of the solvent other than the cyclic carbonate in the total volume of the nonaqueous electrolytic solution is usually 30% by volume or less, preferably 10% by volume or less.

  Next, the electrolyte used in the present invention will be described.

The electrolyte is not particularly limited as long as it is a lithium salt, and various electrolytes can be used. Examples of those usually _{used, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiSbF inorganic lithium salt such as _{6, LiCF 3 SO 3, LiN} (CF 3 SO 2) 2, LiN (CF 3 CF 2 Fluorine-containing organic lithium salts such as SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , Li [PF ₅ (CF ₂ CF ₂ CF ₃ )] Li [PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [PF ₃ (CF ₂ CF ₃ ) ₃ ], Li [PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], Li [PF ₄ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ], etc. Lithium fluorofluorophosphate, lithium fluoroalkylborate such as Li [BF ₃ (CF ₃ CF)], Li [BF ₃ (CF ₂ CF ₃ )], Li [BF ₃ (CF ₂ CF ₃ )], LiB (CF ₃ COO) ₄ , LiB (OCOCF ₂ COO) ₂ , LiB (OCOC ₂ H ₄ COO) ₂ , LiB (C ₂ O ₄ ) and the like. These lithium salts may be used alone or in combination of any number and ratio. Of these, LiPF ₆ and LiBF ₄ are preferably used.

  The concentration of the electrolyte lithium salt in the non-aqueous electrolyte solution is not particularly limited, but the electrolyte lithium salt concentration suitable as the non-aqueous electrolyte solution of the present invention is usually 0.5 mol or more per liter of the non-aqueous electrolyte solution, preferably Is in the range of 0.7 mol or more and usually 2 mol or less, preferably 1.5 mol or less. If the concentration of the electrolyte lithium salt is outside this range, the electrical conductivity of the non-aqueous electrolyte of the present invention may be deteriorated or the viscosity may be affected, thereby reducing the performance of the lithium ion secondary battery. is there.

  The non-aqueous electrolyte of the present invention includes trioctyl phosphate, polyoxyethylene ethers having a perfluoroalkyl group, perfluoro, in order to improve the coatability with the separator described later in addition to the above non-aqueous solvent and electrolyte. Surfactants such as octane sulfonates may be added in the range of 0.01 to 1% by weight based on the total weight of the non-aqueous solvent.

  Furthermore, in the non-aqueous electrolyte of the present invention, various additives, for example, other film forming agents that are considered to generate a film on the surface of the electrode and prevent decomposition of the solvent in the electrode, an overcharge preventing agent, You may mix and use a dehydrating agent, a deoxidizing agent, etc.

  As other film forming agents, it is preferable to use cyclic sultone such as propane sultone, phenylethylene carbonate, cyclic carboxylic acid anhydride and the like. As the cyclic carboxylic acid anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, trimellitic anhydride, phthalic anhydride and the like are used. When the film forming agent is contained in a non-aqueous solvent in an amount of 0.1 to 10% by weight, preferably 0.1 to 8% by weight, the battery capacity retention characteristics and cycle characteristics are improved.

  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 its derivatives described in JP-A-106835, JP-A-9-171840, JP-A-10-32258, JP-A-7-302614, JP-A-11-162512, JP-A-2939469, JP-A-2963898, etc. Partially hydrogenated terphenyl compounds and derivatives thereof described in 2003-100344, JP2003-100345, JP2003-100346, JP2003-115325, etc., and JP2003-77536A 2-oxazolidone derivatives described in JP-A-9-45369, 10 No. 321258, etc., pyrrole derivatives described in JP-A-7-320778, JP-A-7-302614, etc., aromatic compounds such as aniline derivatives, patent 2983205, etc. And other compounds such as those described in JP-A-2001-15158 can be contained. The overcharge inhibitor is preferably contained in the nonaqueous solvent so as to be 0.1 to 5% by weight.

  Next, the lithium ion secondary battery of the present invention using such a nonaqueous electrolytic solution of the present invention will be described.

  The lithium ion secondary battery of the present invention includes a non-aqueous electrolyte solution, a negative electrode and a positive electrode capable of occluding and releasing lithium ions, and the lithium ion secondary battery of the present invention described above as the non-aqueous electrolyte solution. A non-aqueous electrolyte for a battery is used.

[Positive electrode and negative electrode]
The active material of the negative electrode constituting the lithium ion secondary battery of the present invention is arbitrary and is not particularly limited as long as it contains a material capable of occluding and releasing lithium. Specific examples thereof include various pyrolysiss, for example. Examples thereof include pyrolysates of organic matter, artificial graphite, and natural graphite. Preferably, artificial graphite and purified natural graphite produced by high-temperature heat treatment of graphitizable pitch obtained from various raw materials, or graphite materials obtained by subjecting these graphite to various surface treatments containing pitch are mainly used.

  These graphite materials have a d-value (interlayer distance) of a lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of usually 0.335 nm or more and 0.34 nm or less, preferably 0.337 nm or less. Is desirable.

  The graphite material preferably has an ash content of 1% by weight or less, more preferably 0.5% by weight or less, and most preferably 0.1% by weight or less.

  The crystallite size (Lc) obtained by X-ray diffraction of the above graphite material by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more.

  The median diameter of the above graphite 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, further preferably 7 μm or more, and usually 100 μm or less, preferably It is 50 μm or less, more preferably 40 μm or less, and still more preferably 30 μm or less.

Further, the BET specific surface area of the above graphite material is usually 0.5 m ² / g or more, preferably 0.8. m ² / g or more, more preferably 1.0 m ² / g or more, still more preferably 1.5 m ² / g or more, and usually 25.0 m ² / g or less, preferably 20.0 m ² / g More preferably, it is 15.0 m < ² > / g or less, More preferably, it is 10.0 m < ² > / g or less.

Further, the above graphite material has a peak PA (peak intensity IA) in the range of 1580 to 1620 cm ⁻¹ and a peak PB (peak intensity IB) in the range of 1350 to 1370 cm ⁻¹ in Raman spectrum analysis using an argon ion laser beam. ) of the intensity ratio R = IB / IA is 0 or more and 0.5 or less, the half width of the peak in the range of 1580～1620Cm ^-1 is 26cm ^-1 or less, a half value width of the peak in the range of 1580～1620Cm ^-1 is 25 cm ^- It is preferably ¹ or less.

  Further, these carbonaceous materials can be used by mixing other negative electrode materials capable of inserting and extracting lithium. Examples of other negative electrode materials include metal oxide materials such as tin oxide and silicon oxide, lithium metal, and various lithium alloys.

  These negative electrode materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

The active material of the positive electrode constituting the lithium ion secondary battery of the present invention is arbitrary and is not particularly limited, but a lithium transition metal composite oxide is preferably used. Examples of such materials include lithium cobalt composite oxides such as LiCoO ₂ , lithium nickel composite oxides such as LiNiO ₂ , lithium manganese composite oxides such as LiMnO _{2, and the} like. In these lithium transition metal composite oxides, some of the main transition metal elements are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, etc. It can also be stabilized by replacing with other metal species, and is preferred.

  These positive electrode active materials may be used alone or in combinations of two or more in any combination.

  The method for producing the positive electrode and the negative electrode is not particularly limited. For example, it can be produced by adding a binder, a thickener, a conductive material, a solvent or the like to the above active material as necessary to form a slurry, applying the slurry to a substrate of a current collector, and drying. . Further, the active material can be roll-formed as it is to obtain a sheet electrode, or a pellet electrode by compression molding.

  The binder is not particularly limited as long as it is a material that is stable with respect to the solvent and electrolyte used in electrode production. Specific examples include polyvinylidene fluoride, polytetrafluoroethylene, styrene / butadiene rubber, and isoprene rubber. And butadiene rubber.

  Examples of the thickener include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, 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. In particular, the positive electrode preferably contains a conductive material.

  The solvent used for manufacturing the positive electrode or the negative electrode may be aqueous or organic. Examples of the aqueous solvent include water and alcohol, and examples of the organic solvent include N-methylpyrrolidone (NMP) and toluene.

  As the material for the current collector for the negative electrode, metals such as copper, nickel, and stainless steel are used, and among these, copper foil is preferable from the viewpoint of easy processing into a thin film and cost. The positive electrode current collector is made of a metal such as aluminum, titanium, or tantalum. Among these, aluminum foil is preferable from the viewpoint of easy processing into a thin film and cost.

[Others]
In a lithium ion secondary battery, a separator is usually interposed between a positive electrode and a negative electrode in order to prevent a short circuit between the electrodes. The material and shape of the separator used in the lithium ion secondary battery of the present invention are not particularly limited, but it is preferable to select from materials that are stable with respect to the non-aqueous electrolyte solution of the present invention and have excellent liquid retention properties. It is preferable to use a porous sheet or nonwoven fabric made of polyolefin such as polyethylene and polypropylene.

  The lithium ion secondary battery of the present invention is manufactured by assembling the above-described nonaqueous electrolytic solution of the present invention, a positive electrode, a negative electrode, and a separator used as necessary into an appropriate shape. Furthermore, other components such as an outer case can be used as necessary. The method for assembling the battery is not particularly limited, and may be appropriately selected from methods usually employed.

  Also, the shape of the battery is not particularly limited, and a cylinder type in which a sheet electrode and a separator are spiraled, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are stacked, and the like are applied. Is possible.

  The use of the lithium ion secondary battery of the present invention is not particularly limited, and can be used for various known uses. Specific examples include notebook computers, pen input computers, mobile computers, electronic book players, mobile phones, mobile faxes, mobile copy, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, minidiscs, and transceivers. Electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, lighting equipment, toys, game machines, watches, strobes, cameras, etc. In particular, since the lithium ion secondary battery of the present invention is excellent in cycle characteristics, excellent effects can be obtained in any of these applications.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples unless it exceeds the gist.

(Example 1)
[Production of negative electrode]
X-ray diffraction lattice plane (002 plane) d value is 0.336 nm, crystallite size (Lc) is 652 nm, ash content is 0.07 wt%, median diameter by laser diffraction / scattering method is 12 μm, BET specific surface area There 7.5 m ² / g, a peak PA (peak intensity IA) in the range of 1570～1620Cm ^-1 in the Raman spectrum analysis using an argon ion laser beam and scope of 1300～1400Cm ^-1 peak PB (peak intensity IB) intensity ratio R = IB / IA of the half width of the peak in the range of 0.12,1570～1620Cm ^-1 was used natural graphite powder is 19.9Cm ^-1 as the negative electrode active material. 94 parts by weight of this graphite powder was mixed with 6 parts by weight of polyvinylidene fluoride and dispersed with N-methyl-2-pyrrolidone to form a slurry. This was uniformly applied to one side of a 18 μm-thick copper foil as a negative electrode current collector, dried, and then pressed by a press machine so that the density of the negative electrode layer was 1.5 g / cm ³ to obtain a negative electrode.

[Production of positive electrode]
LiCoO ₂ was used as the positive electrode active material. To 85 parts by weight of this active material, 6 parts by weight of carbon black and 9 parts by weight of polyvinylidene fluoride KF-1000 (trade name, manufactured by Kureha Chemical Co., Ltd.) are added and mixed, and dispersed in N-methyl-2-pyrrolidone to form a slurry. Was applied uniformly on both sides of a 20 μm-thick aluminum foil as a positive electrode current collector, dried, and then pressed by a press machine so that the density of the positive electrode layer was 3.0 g / cm ^3. It was.

[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. Subsequently, 2 parts by weight of vinylene carbonate and 1 part by weight of 4-vinylethylene sulfite were added to 97 parts by weight of this blank electrolyte to prepare a desired electrolyte.

[Production of battery]
A battery element is produced by laminating the above-described positive electrode, negative electrode, and polyethylene separator in the order of the negative electrode, separator, positive electrode, separator, and negative electrode. After taking out the terminal of the positive electrode and the negative electrode in the film, the electrolytic solution was injected and vacuum-sealed to produce a sheet battery.

[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. Further, continuous charging at 60 ° C. and 4.2 V-CCCV was performed for 2 weeks.

  Before and after the continuous charge test at 60 ° C. and 4.2 V-CCCV, the sheet battery was immersed in an ethanol bath, and the amount of gas generated from the change in volume was determined. After measuring the volume, the battery was once discharged to a final discharge voltage of 3 V at a constant current of 0.2 C at 25 ° C., then charged again with 4.2 V-CCCV (0.05 C cut), and again with a constant current of 0.2 C. Then, the discharge capacity was discharged to 3 V to measure the recovery capacity after continuous charging. Next, the battery was charged under the same CCCV conditions, and discharged to 3 V at a current value corresponding to 1 C, and the discharge characteristics were measured. Here, 1C represents a current value that can be fully charged in one hour.

  Table 1 shows the amount of generated gas, the recovery capacity (%) after continuous charging, and the 1C capacity (%) when the discharge capacity before continuous charging is 100.

(Example 2)
An electrolyte solution was prepared in the same manner as in Example 1, except that 27.9 parts by weight of vinylene carbonate and 0.1 part by weight of 4-vinylethylene sulfite were added to 97.9 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, evaluated in the same manner, and the results are shown in Table 1.

(Example 3)
An electrolytic solution was prepared in the same manner as in Example 1 except that 2 parts by weight of vinylene carbonate and 3 parts by weight of 4-vinylethylene sulfite were added to 95 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, evaluated in the same manner, and the results are shown in Table 1.

Example 4
An electrolytic solution was prepared in the same manner as in Example 1 except that 2 parts by weight of vinylene carbonate and 0.005 parts by weight of 4-vinylethylene sulfite were added to 97.995 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, evaluated in the same manner, and the results are shown in Table 1.

(Example 5)
An electrolytic solution was prepared in the same manner as in Example 1 except that 5 parts by weight of vinylene carbonate and 1 part by weight of 4-vinylethylene sulfite were added to 94 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, evaluated in the same manner, and the results are shown in Table 1.

(Example 6)
An electrolytic solution was prepared in the same manner as in Example 1 except that 0.005 parts by weight of vinylene carbonate and 1 part by weight of 4-vinylethylene sulfite were added to 98.995 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, evaluated in the same manner, and the results are shown in Table 1.

(Example 7)
An electrolytic solution was prepared in the same manner as in Example 1 except that 12 parts by weight of vinylene carbonate and 1 part by weight of 4-vinylethylene sulfite were added to 87 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, evaluated in the same manner, and 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 vinylene carbonate and 4-vinylethylene sulfite were not added and 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 4-vinylethylene sulfite 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.

(Comparative Example 3)
An electrolytic solution was prepared in the same manner as in Example 1 except that 1 part by weight of 4-vinylethylene sulfite was added to 99 parts by weight of the blank electrolytic solution, and vinylene carbonate 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.

  As is apparent from Table 1, in Comparative Examples 1 and 2 that do not contain a vinylethylene sulfite compound, a large amount of gas is generated even when continuously charged. Further, it can be seen that Comparative Example 3 containing a vinylethylene sulfite compound but not containing a vinylene carbonate compound is inferior in residual capacity and discharge characteristics after continuous charging, although generation of gas is suppressed.

  On the other hand, Examples 1-7 containing a vinylene carbonate compound and a vinyl ethylene sulfite compound have little gas generation | occurrence | production, and it turns out that it is excellent in the residual capacity and discharge characteristics after continuous charge.

  According to the present invention, it is possible to achieve a lithium ion secondary battery that suppresses the amount of gas generated during continuous charging and has excellent discharge characteristics after continuous charging, such as an electronic device in which the lithium secondary battery is used. It can be suitably used in various fields.

Claims (7)

In a non-aqueous electrolyte solution containing an electrolyte and a non-aqueous solvent, at least one vinylene carbonate compound represented by the following general formula (I) and at least one vinyl ethylene sulfite compound represented by the following general formula (II) And a non-aqueous electrolyte for a lithium ion secondary battery.

Wherein R ₁ and R ₂ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms in which one or more hydrogen atoms may be substituted with a halogen atom. )

Wherein R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent. .)   2. The non-aqueous electrolysis for a lithium ion secondary battery according to claim 1, wherein the content of the vinyl ethylene sulfite compound is 0.01 to 5% by weight with respect to the total weight of the non-aqueous electrolyte solution. liquid.   3. The non-aqueous electrolysis for a lithium ion secondary battery according to claim 1, wherein the content of the vinylene carbonate compound is 0.01 to 10% by weight with respect to the total weight of the non-aqueous electrolyte. liquid.   The content ratio of the vinylene carbonate compound and the vinyl ethylene sulfite compound in the non-aqueous electrolyte solution according to any one of claims 1 to 3 is 99: 1 to 1:99. Non-aqueous electrolyte for lithium ion secondary batteries.   The non-aqueous electrolyte solution for a lithium ion secondary battery according to any one of claims 1 to 4, wherein the vinylene carbonate compound is vinylene carbonate.   6. The non-aqueous electrolyte for a lithium ion secondary battery according to claim 1, wherein the vinyl ethylene sulfite compound is 4-vinyl ethylene sulfite.   A lithium ion secondary battery using the non-aqueous electrolyte for a lithium ion secondary battery according to any one of claims 1 to 6.