JP2008171766A - Non-aqueous electrolytic solution, secondary battery using this, and capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolytic solution which realizes an electrochemical capacitor such as a battery and an electric double layer capacitor, in particular, a non-aqueous electrolytic solution secondary battery, which gives improvement in discharge characteristics at a low-temperature and improvement in discharge characteristics at high output, and a power storage device (battery, capacitor) using the same. <P>SOLUTION: The non-aqueous electrolytic solution has a non-aqueous solvent, an electrolyte salt, and a denatured silane having acetylene group as shown in the formula (1) and/or (2) as the essential component. In the formula, R<SP>1</SP>, R<SP>2</SP>, and R<SP>3</SP>are the same or a different kind of organic group selected from alkyl group having a carbon number 1-30 which may be substituted by halogen atom, aryl group, aralkyl group, amino-substituted alkyl group, carboxyl substituted alkyl group, alkoxy group, and aryloxy group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nonaqueous electrolytic solution containing a modified silane having an acetylene group, and various energy devices using the electrolytic solution, in particular, secondary batteries, electrochemical capacitors, particularly lithium ions between a positive electrode and a negative electrode. Non-aqueous electrolyte containing modified silane having acetylene group effective as non-aqueous electrolyte used for lithium ion secondary battery that is moved and charged, and secondary battery and electric double layer using the electrolyte The present invention relates to an electrochemical capacitor such as a capacitor. Energy devices such as batteries and capacitors using the electrolytic solution of the present invention have excellent temperature characteristics and high output characteristics.

  In recent years, the use of lithium ion secondary batteries having a high energy density as portable power sources that can be charged for notebook computers, mobile phones, digital cameras, or digital video cameras is increasing. In addition, in consideration of the environment, lithium-ion secondary batteries or non-aqueous batteries using non-aqueous electrolytes are also used as auxiliary power sources for electric vehicles and hybrid vehicles that are being put to practical use as vehicles that do not release exhaust gas into the atmosphere. Multilayer capacitors are being considered.

  However, although lithium-ion secondary batteries have high performance, they are not sufficient for discharge characteristics under harsh environments (especially in low-temperature environments) and discharge characteristics under high output that require a large amount of electricity in a short time. I can not say. On the other hand, the electric double layer capacitor has a problem that its withstand voltage is insufficient and the electric capacity decreases with time, and further improvement of the electrolytic solution is required.

In addition, the following are mentioned as prior literature relevant to the present invention.
Japanese Patent Laid-Open No. 11-214032 JP 2000-58123 A JP 2001-110455 A JP 2003-142157 A

  The present invention has been made in view of the above circumstances, and provides an improvement in discharge characteristics at low temperatures, an improvement in discharge characteristics under high output, and an electrochemical capacitor such as an electric double layer capacitor, particularly a non-aqueous electrolyte. It aims at providing the nonaqueous electrolyte which enables a secondary battery, and the electrical storage device (battery, capacitor) using the same.

［式中、Ｒ¹、Ｒ²及びＲ³は、ハロゲン原子で置換されていてもよい炭素数１〜３０のアルキル基、アリール基、アラルキル基、アミノ置換アルキル基、カルボキシル置換アルキル基、アルコキシ基、アリーロキシ基から選択される同一又は異種の有機基である］
［ＩＩ］前記アセチレン基を有する変性シラン中のＲ¹、Ｒ²及びＲ³が炭素数１〜６のアルキル基、又はフッ素置換アルキル基、又はフェニル基である［Ｉ］記載の非水電解液。
［ＩＩＩ］前記アセチレン基を有する変性シランの含有量が非水電解液全体の０．００１体積％以上であることを特徴とする［Ｉ］又は［ＩＩ］記載の非水電解液。
［ＩＶ］前記電解質塩がリチウム塩であることを特徴とする［Ｉ］〜［ＩＩＩ］のいずれか１項記載の非水電解液。
［Ｖ］［Ｉ］〜［ＩＶ］のいずれか１項記載の非水電解液を含むことを特徴とする二次電池。
［ＶＩ］［Ｉ］〜［ＩＶ］のいずれか１項記載の非水電解液を含むことを特徴とする電気化学キャパシタ。
［ＶＩＩ］［Ｉ］〜［ＩＶ］のいずれか１項記載の非水電解液を含むことを特徴とするリチウムイオン二次電池。 As a result of intensive studies to achieve the above object, the present inventors have shown a nonaqueous solvent, an electrolyte salt, and the following formula (1) and / or (2) as a nonaqueous electrolytic solution for an electricity storage device. By using a non-aqueous electrolyte containing an acetylene-modified silane having an acetylene group (that is, HC≡C-structure) at the molecular chain end as an essential component, the discharge characteristics at low temperatures can be improved and the output can be increased under high output. It has been found that discharge characteristics can be improved, and the present invention has been made.
Accordingly, the present invention provides the following non-aqueous electrolyte, a secondary battery including the non-aqueous electrolyte, an electrochemical capacitor, and a lithium ion secondary battery.
[I] A nonaqueous electrolytic solution comprising as essential components a nonaqueous solvent, an electrolyte salt, and a modified silane having an acetylene group represented by the following formula (1) and / or (2).

[Wherein R ¹ , R ² and R ³ are each an alkyl group having 1 to 30 carbon atoms which may be substituted with a halogen atom, an aryl group, an aralkyl group, an amino-substituted alkyl group, a carboxyl-substituted alkyl group, or an alkoxy group. Are the same or different organic groups selected from aryloxy groups]
[II] The nonaqueous electrolytic solution according to [I], wherein R ¹ , R ^2, and R ³ in the modified silane having an acetylene group are an alkyl group having 1 to 6 carbon atoms, a fluorine-substituted alkyl group, or a phenyl group. .
[III] The non-aqueous electrolyte according to [I] or [II], wherein the content of the modified silane having an acetylene group is 0.001% by volume or more of the whole non-aqueous electrolyte.
[IV] The non-aqueous electrolyte according to any one of [I] to [III], wherein the electrolyte salt is a lithium salt.
[V] A secondary battery comprising the nonaqueous electrolytic solution according to any one of [I] to [IV].
[VI] An electrochemical capacitor comprising the nonaqueous electrolytic solution according to any one of [I] to [IV].
[VII] A lithium ion secondary battery comprising the nonaqueous electrolytic solution according to any one of [I] to [IV].

  The electricity storage device using the nonaqueous electrolytic solution containing the modified silane having an acetylene group of the present invention has excellent temperature characteristics and high output characteristics.

  The modified silane having an acetylene group used in the non-aqueous electrolyte of the present invention is an acetylene modified having an acetylene group (that is, HC≡C-structure) at the molecular chain end represented by the following formula (1) and / or (2). It is a silane compound (hereinafter sometimes simply referred to as a modified silane having an acetylene group or a modified silane).

In the above formulas, R ^1, R ² and R ³ may be the same or different, 1 to 30 carbon atoms which may be partially substituted with a halogen atom, preferably 1 to 12, more preferably 1 to 6 An organic group selected from an alkyl group, an aryl group, an aralkyl group, an amino-substituted alkyl group, a carboxyl-substituted alkyl group, an alkoxy group, and an aryloxy group. Specific examples thereof include methyl group, ethyl group, propyl group, butyl group, pentyl group, cyclopentyl group, cyclohexyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and other alkyl groups, phenyl group, An aryl group such as a tolyl group, an aralkyl group such as a benzyl group and a phenethyl group, and the like, an amino-substituted alkyl group such as a 3-aminopropyl group, a 3-[(2-aminoethyl) amino] propyl group, Examples include carboxy-substituted alkyl groups such as 3-carboxypropyl group. Moreover, the halogenated alkyl group by which some hydrogen atoms were substituted by halogen atoms, such as a fluorine atom, like a trifluoropropyl group, a nonafluorooctyl group, etc. is mentioned. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and an isopropoxy group. An aryloxy group includes a phenyloxy group. Among these, an alkyl group having 1 to 6 carbon atoms and a fluorine-substituted alkyl group are preferable, and a methyl group or an ethyl group is most preferable. In particular, the total of R ¹ and R ² , particularly 80 mol% or more (that is, 80 to 100 mol%) of the total of R ^{1 to} R ³ is preferably a methyl group or an ethyl group.

  The modified silane having an acetylene group of the present invention includes 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, It can be obtained by dehydrochlorination reaction of acetylene alcohol such as ethynyl-1-cyclohexanol and silane such as trimethylchlorosilane and dimethyldichlorosilane. For example, the following compound [I] is reacted with 3-methyl-1-butyn-3-ol and trimethylchlorosilane, and compound [II] is converted into 3-methyl-1-butyn-3-ol and dimethyldichlorosilane. It can obtain by reaction of.

  Specific examples of the modified silane having an acetylene group of the present invention include the following compounds.

    The modified silane having an acetylene group of the present invention is required to be contained in a non-aqueous electrolyte solution by 0.001% by volume or more. If it is less than 0.001% by volume, the effects of the present invention may not be sufficiently exerted. Preferably it is 0.1 volume% or more. Further, the upper limit of the content varies depending on the solvent for the non-aqueous electrolyte to be used, but the content is such that the movement of Li ions in the non-aqueous electrolyte does not become a practical level or less. Usually, it is 50 volume% or less, Preferably it is 20 volume% or less, More preferably, it is 10 volume% or less.

The nonaqueous electrolytic solution of the present invention contains an electrolyte salt and a nonaqueous solvent. Examples of the electrolyte salt include light metal salts. Light metal salts include alkali metal salts such as lithium salt, sodium salt or potassium salt, alkaline earth metal salts such as magnesium salt or calcium salt, or aluminum salt, and one or more are selected according to the purpose. Is done. For example, in the case of a lithium salt, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, C ₄ F ₉ SO ₃ Li, CF ₃ CO ₂ Li, ( CF ₃ CO ₂ ) ₂ NLi, C ₆ F ₅ SO ₃ Li, C ₈ F ₁₇ SO ₃ Li, (C ₂ F ₅ SO ₂ ) ₂ NLi, (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) NLi , (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) NLi, ((CF ₃ ) ₂ CHOSO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, (3,5- (CF ₃ ) ₂ C ₆ F ₃ ) ₄ BLi, LiCF ₃ , LiAlCl _4, or C ₄ BO ₈ Li may be used, and any one or two of these may be used in combination.

  The concentration of the electrolyte salt in the nonaqueous electrolytic solution is preferably 0.5 to 2.0 mol / L from the viewpoint of electrical conductivity. The conductivity of the electrolyte at 25 ° C. is preferably 0.01 S / m or more, and is adjusted by the type of electrolyte salt or its concentration.

The solvent for non-aqueous electrolyte used in the present invention is not particularly limited as long as it can be used for non-aqueous electrolyte. Generally, aprotic high dielectric constant solvents such as ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, dipropyl carbonate, diethyl ether, tetrahydrofuran, 1,2, -Aprotic low viscosity such as acetate ester or propionate ester such as dimethoxyethane, 1,2-diethoxyethane, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, methyl acetate A solvent is mentioned. It is desirable to use these aprotic high dielectric constant solvents and aprotic low viscosity solvents in combination at an appropriate mixing ratio. Furthermore, ionic liquids using imidazolium, ammonium, and pyridinium type cations can be used. The counter anion is not particularly limited, and examples thereof include BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ^{− and the} like. The ionic liquid can be used by mixing with the aforementioned non-aqueous electrolyte solvent.

  In the case of a solid electrolyte or gel electrolyte, it is possible to contain silicone gel, silicone polyether gel, acrylic gel, acrylonitrile gel, poly (vinylidene fluoride) and the like as a polymer material. These may be polymerized in advance or may be polymerized after injection. These can be used alone or as a mixture.

  Furthermore, you may add various additives in the non-aqueous electrolyte of this invention as needed. For example, vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4-vinylethylene carbonate and the like for the purpose of improving cycle life, biphenyl, alkylbiphenyl, cyclohexylbenzene, t-butylbenzene, diphenyl ether for the purpose of preventing overcharge, Examples include benzofuran, various carbonate compounds for the purpose of deoxidation and dehydration, various carboxylic acid anhydrides, various nitrogen-containing compounds, and sulfur-containing compounds.

  The nonaqueous electrolytic solution according to the present invention can be used in a power storage device such as a positive battery, a negative electrode, a separator, a secondary battery including an electrolytic solution, and an electrochemical capacitor.

Examples of the positive electrode active material include oxides or sulfides capable of inserting and extracting lithium ions, and any one or more of these are used. Specifically, for example, TiS ₂ , MoS ₂ , NbS ₂ , ZrS ₂ , VS ₂ , V ₂ O ₅ , MoO ₃ , Mg (V ₃ O ₈ ) ₂ or other metal sulfides or oxides that do not contain lithium Or a lithium composite oxide containing lithium and lithium, and a composite metal such as NbSe ₂ . Among these, in order to increase the energy density, a lithium composite oxide mainly composed of Li _p MetO ₂ is preferable. In this case, specifically, Met is preferably at least one of cobalt, nickel, iron and manganese, and p is usually a value in the range of 0.05 ≦ p ≦ 1.10. Specific examples of the lithium composite _{oxide, LiCoO 2, LiNiO 2, LiFeO} 2, Li q Ni r Co 1-r O 2 ( where, the values of q and r is a charge-discharge state of the battery having the layer structure Usually, 0 <q <1, 0.7 <r ≦ 1), spinel-structured LiMn ₂ O ₄ and orthorhombic LiMnO ₂ may be mentioned. Furthermore, LiMet _s Mn _1-s O ₄ (0 <s <1) is also used as a substituted spinel manganese compound as a high-voltage compatible type, where Met is titanium, chromium, iron, cobalt, nickel, copper and zinc. Etc.

  The lithium composite oxide is obtained by, for example, grinding lithium carbonate, nitrate, oxide or hydroxide, and transition metal carbonate, nitrate, oxide or hydroxide according to a desired composition. It is prepared by mixing and baking at a temperature in the range of 600 ° C. to 1,000 ° C. in an oxygen atmosphere.

  Furthermore, an organic substance can also be used as the positive electrode active material. Illustrative examples include polyacetylene, polypyrrole, polyparaphenylene, polyaniline, polythiophene, polyacene, polysulfide compound and the like.

  Examples of the negative electrode material capable of inserting and extracting lithium ions include carbon materials, metal elements or similar metal elements, metal composite oxides, polymer materials such as polyacetylene and polypyrrole, and the like.

  The carbon material is synthesized by a liquid phase method including carbons synthesized by a gas phase method such as acetylene black, pyrolytic carbon, natural graphite, etc., artificial graphites, coke such as petroleum coke or pitch coke by a carbonization process. And carbons synthesized by a solid phase method such as pyrolytic carbon obtained by firing a carbon film, polymer, wood raw material, phenol resin, and carbon film, charcoal, glassy carbon, and carbon fiber.

  Examples of the negative electrode material capable of inserting and extracting lithium include a single element, an alloy, or a compound of a metal element or a similar metal element capable of forming an alloy with lithium. The form includes a solid solution, a eutectic, an intermetallic compound, or those in which two or more of them coexist. Any one of these or a mixture of two or more may be used.

  Examples of such metal elements or similar metal elements include tin, lead, aluminum, indium, silicon, zinc, copper, cobalt, antimony, bismuth, cadmium, magnesium, boron, gallium, germanium, arsenic, selenium, tellurium, Silver, hafnium, zirconium and yttrium are mentioned. Among these, a single element, alloy or compound of Group 4B metal element or similar metal element is preferable, and silicon or tin, or an alloy or compound thereof is particularly preferable. These may be crystalline or amorphous.

Specific examples of such alloys or compounds include LiAl, AlSb, CuMgSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi _{2. , CaSi 2, CrSi 2, Cu} 5 Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si / SiC _{composite, Si 3 N 4, Si 2} N 2 O , SiO _v (0 <v ≦ 2), SiO / C composite, SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO or LiSnO.

  There is no restriction | limiting in particular about the preparation methods of a positive electrode and a negative electrode. In general, an active material, a binder, a conductive agent or the like is added to a solvent to form a slurry, which is applied to a current collector sheet, dried and pressed.

Examples of the binder generally include polyvinylidene fluoride, polytetrafluoroethylene, styrene / butadiene rubber, isoprene rubber, various polyimide resins, and the like.
Examples of the conductive agent generally include carbon-based materials such as graphite and carbon black, and metal materials such as copper and nickel.
Examples of the current collector include aluminum or an alloy thereof for the positive electrode, and a metal such as copper, stainless steel, nickel, or an alloy thereof for the negative electrode.

  The separator used between the positive electrode and the negative electrode is not particularly limited as long as it is stable with respect to the electrolytic solution and has excellent liquid retention, but is generally a polyolefin-based porous sheet or nonwoven fabric such as polyethylene and polypropylene. Is mentioned. Moreover, porous glass, ceramics, etc. are also used.

  The shape of the secondary battery is arbitrary and is not particularly limited. In general, a coin type in which an electrode punched into a coin shape and a separator are stacked, a cylindrical shape in which an electrode sheet and a separator are spiraled, and the like are listed.

  The nonaqueous electrolytic solution according to the present invention can be used for an electrode, a separator, an electrochemical capacitor provided with an electrolytic solution, particularly an electric double layer capacitor, a pseudo electric double layer capacitor, an asymmetric capacitor, a redox capacitor, or the like.

  At least one of the electrodes used in the capacitor is a polarizable electrode mainly composed of a carbonaceous material. A polarizable electrode is generally composed of a carbonaceous material, a conductive agent, and a binder, and the method for producing such a polarization positive electrode is prepared in exactly the same manner as the above-described lithium secondary battery. For example, mainly powdered or fibrous activated carbon, carbon black, and conductive agent such as acetylene black are mixed, polytetrafluoroethylene is added as a binder, and this mixture is applied or pressed onto a current collector such as stainless steel or aluminum. Things are used. Similarly, a material having high ion permeability is preferably used for the separator and the electrolytic solution, and materials used in lithium secondary batteries are used in substantially the same manner. Moreover, a coin shape, a cylindrical shape, a square shape etc. are mentioned as a shape.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

    [Examples 1 to 6, Comparative Example]

(Preparation of non-aqueous electrolyte)
The above-mentioned compounds [I] and [II] as modified silanes having an acetylene group were dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) at a ratio shown in Table 1. Next, LiPF ₆ was dissolved at a concentration of 1 mol / L to obtain a non-aqueous electrolyte. Further, as a comparative example, the same evaluation was performed for the case where the non-aqueous electrolyte did not contain a modified silane having an acetylene group.

(Production of battery materials)
As the positive electrode material, a single layer sheet (Pionix Co., Ltd., trade name: Pioxel C-100) using LiCoO ₂ as an active material and an aluminum foil as a current collector was used. Moreover, the single layer sheet | seat (Pionix Co., Ltd. make, brand name; Pioxel A-100) using graphite as an active material and copper foil as a collector was used as negative electrode material.
Next, a glass fiber filter (manufactured by Advantech Toyo Co., Ltd., trade name: GC-50) was used as a separator.

(Battery assembly)
In a dry box under an argon atmosphere, a 2032 coin-type battery was assembled using a stainless steel can serving as the battery material and a positive electrode conductor, a stainless sealing plate serving as a negative electrode conductor, and an insulating gasket.

(Evaluation of battery performance; low temperature characteristics)
10 cycles of charging (up to 4.2 V under a constant current of 0.6 mA) and discharging (up to 2.5 V under a constant current of 0.6 mA) at 25 ° C., and then repeating charging and discharging similarly at 5 ° C. It was. The number of cycles when the discharge capacity at 5 ° C. decreased to 80 was determined by setting the discharge capacity at the 10th cycle at 100 ° C. at 25 ° C. The results are shown in Table 2.

(Evaluation of battery performance; high output characteristics)
After 5 cycles of charging (up to 4.2 V under a constant current of 0.6 mA) and discharging (up to 2.5 V under a constant current of 0.6 mA) at 25 ° C., the current for discharging remains unchanged under the charging conditions. 5 cycles were repeated at 5 mA.
Charging / discharging of these two types of conditions was repeated alternately. The discharge capacity at the fifth cycle in the first 0.6 mA charge / discharge was taken as 100, and the number of cycles when the discharge capacity dropped to 80 was determined.

  As shown in Table 2, it can be seen that when the modified silane having an acetylene group is added, both excellent temperature characteristics and high output characteristics are exhibited as compared with the comparative example without addition.

Claims (7)

A nonaqueous electrolytic solution comprising a nonaqueous solvent, an electrolyte salt, and a modified silane having an acetylene group represented by the following formula (1) and / or (2) as essential components.

[Wherein R ¹ , R ² and R ³ are each an alkyl group having 1 to 30 carbon atoms which may be substituted with a halogen atom, an aryl group, an aralkyl group, an amino-substituted alkyl group, a carboxyl-substituted alkyl group, or an alkoxy group. Are the same or different organic groups selected from aryloxy groups] ^2. The nonaqueous electrolytic solution according to claim ¹ , wherein R ¹ , R ^2, and R ³ in the modified silane having an acetylene group are an alkyl group having 1 to 6 carbon atoms, a fluorine-substituted alkyl group, or a phenyl group.   3. The non-aqueous electrolyte according to claim 1, wherein the content of the modified silane having an acetylene group is 0.001% by volume or more of the whole non-aqueous electrolyte.   The nonaqueous electrolytic solution according to claim 1, wherein the electrolyte salt is a lithium salt.   A secondary battery comprising the nonaqueous electrolytic solution according to claim 1.   An electrochemical capacitor comprising the nonaqueous electrolytic solution according to any one of claims 1 to 4.   A lithium ion secondary battery comprising the non-aqueous electrolyte according to claim 1.