JP4158939B2 - Electrolyte material and electrolyte - Google Patents

Description

  The present invention relates to an electrolytic solution material and an electrolytic solution. More specifically, the present invention relates to an electrolytic solution material and an electrolytic solution that have excellent ionic conductivity and excellent pH stability.

  It is desired that an electrolytic solution used in an electrochemical device such as a lithium secondary battery, an electrolytic capacitor, or an electric double layer capacitor is excellent in ionic conductivity and electrochemically stable at a high potential. Specifically, as an electrolytic solution for electrolytic capacitors, for example, a salt (tertiary salt) of triethylamine or the like with maleic acid or phthalic acid or the like is dissolved in a solvent such as γ-butyrolactone, N, N-dimethylformamide, or ethylene glycol. What was made to use is used (refer patent document 1). However, when a tertiary salt is used in this way, there is a problem that conductivity is low.

Therefore, a solvent in which a salt (quaternary salt) of tetraalkylammonium and maleic acid, phthalic acid or the like is dissolved in a solvent is used (see Patent Document 2). When a quaternary salt is used, the conductivity is higher than when a quaternary salt is used, but there is a problem that the pH in the system increases. As a result, there is a problem that the sealing rubber of the capacitor is deteriorated, the liquid leaks from the cathode portion, adheres to the surface of the printed circuit board, and causes problems such as corrosion and disconnection. Further, although the conductivity is improved as compared with the case of using a tertiary salt, further improvement is desired.
JP 54-7564 A Japanese Patent Laid-Open No. 62-264615

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide an electrolytic solution material and an electrolytic solution that have excellent ionic conductivity and excellent pH stability. There is.

（式（１）中のＸはＣ，Ｓｉ，Ｎ，Ｐ，ＳまたはＯを表す。Ｒはハロゲン原子、官能基または有機基を表す。ｓは３，４または５である。）
下記一般式（２）で表される電解質塩とを含み、

（式（２）中のＹはＣ，Ｓｉ，Ｎ，Ｐ，ＳまたはＯを表す。Ｒ’は水素原子、ハロゲン原子、官能基または有機基を表す。ｔは２，３または４である。）
該式（１）中のＡ⁻および／または該式（２）中のＢ⁻が下記一般式（３）で表される。

（式（３）中のＺはＢ，Ｃ，Ｓ，Ｎ，Ｏ，Ａｌ，Ｓｉ，Ｐ，ＡｓまたはＳｅを表す。Ｍ^１およびＭ^２は連結基を表す。Ｑは水素原子、ハロゲン原子、官能基または有機基を表す。ａは１以上の整数である。ｂ，ｃ，ｄおよびｅは０以上の整数である。） The electrolyte material of the present invention includes an electrolyte salt represented by the following general formula (1),

(X in the formula (1) represents C, Si, N, P, S or O. R represents a halogen atom, a functional group or an organic group. S is 3, 4 or 5.)
An electrolyte salt represented by the following general formula (2),

(Y in Formula (2) represents C, Si, N, P, S or O. R ′ represents a hydrogen atom, a halogen atom, a functional group or an organic group. T is 2, 3 or 4. )
A ⁻ in the formula (1) and / or B ⁻ in the formula (2) is represented by the following general formula (3).

(Z in Formula (3) represents B, C, S, N, O, Al, Si, P, As, or Se. M ¹ and M ² represent a linking group. Q represents a hydrogen atom, a halogen atom, Represents a functional group or an organic group, a is an integer of 1 or more, and b, c, d, and e are integers of 0 or more.)

  In a preferred embodiment, X in the above formula (1) and / or Y in the above formula (2) is N.

  In a preferred embodiment, the cation in the above formula (2) is a tertiary ammonium cation.

  In a preferred embodiment, Z in the above formula (3) is C or N.

  According to another aspect of the present invention, an electrolytic solution is provided. This electrolytic solution is obtained by dissolving the electrolyte material in a solvent.

  According to still another aspect of the present invention, a lithium secondary battery is provided. This lithium secondary battery uses the above electrolytic solution.

  According to still another aspect of the present invention, an electrolytic capacitor is provided. This electrolytic capacitor uses the above electrolytic solution.

  According to still another aspect of the present invention, an electric double layer capacitor is provided. This electric double layer capacitor uses the above electrolytic solution.

  According to the present invention, by using a combination of two types of electrolyte salts having specific anions, an electrolyte material and an electrolyte that can achieve excellent ionic conductivity and excellent pH stability are provided. be able to.

A. Electrolyte Material The electrolyte material of the present invention includes an electrolyte salt represented by the following general formula (1) and an electrolyte salt represented by the following general formula (2).

  X in the above formula (1) represents C, Si, N, P, S or O. R in the above formula (1) represents a halogen atom, a functional group or an organic group. The Rs may be the same or different from each other. The Rs may be bonded to each other. s is 3, 4 or 5. Note that s is a value determined by the valence of X.

  In the present specification, the “organic group” means a group having at least one carbon atom. That is, the “organic group” in this specification includes those having a functional group such as an amino group and a carboxyl group, and other groups and atoms such as a halogen atom, as long as it has at least one carbon atom. .

Preferable specific examples of the cation in the above formula (1) include an onium cation represented by the following general formula (4).

（Ｒ^１〜Ｒ^７は、水素原子、ハロゲン原子、官能基、炭化水素基または置換炭化水素基を表す。Ｒ^１〜Ｒ^７は、互いに同一であっても異なっていてもよい。Ｒ^１〜Ｒ^７は、互いに結合していてもよい。）
で表される複素環オニウムカチオン；
（ＩＩ）下記一般式

（Ｒ^１〜Ｒ^８は、水素原子、ハロゲン原子、官能基、炭化水素基または置換炭化水素基を表す。Ｒ^１〜Ｒ^８は、互いに同一であっても異なっていてもよい。Ｒ^１〜Ｒ^８は、互いに結合していてもよい。）
で表される不飽和オニウムカチオン；
（ＩＩＩ）下記一般式

（Ｒ^１〜Ｒ^１２は、水素原子、ハロゲン原子、官能基、炭化水素基または置換炭化水素基を表す。Ｒ^１〜Ｒ^１２は、互いに同一であっても異なっていてもよい。Ｒ^１〜Ｒ^１２は、互いに結合していてもよい。）
で表される飽和環オニウムカチオン；
（ＩＶ）下記一般式

（Ｒは、Ｃ_１〜Ｃ_８のアルキル基を表す。）
で表される鎖状オニウムカチオンがさらに好ましい。 Among the above onium cations,
(I) The following general formula

^(R 1 to R ⁷ is a hydrogen atom, a halogen atom, a functional group, ^.R 1 to R ⁷ representing a hydrocarbon group or a substituted hydrocarbon group to each other may be different even in the same ^.R 1 ~ R ⁷ may be bonded to each other.)
A heterocyclic onium cation represented by:
(II) The following general formula

^(R 1 to R ⁸ is a hydrogen atom, a halogen atom, a functional group, ^.R 1 to R ⁸ representing a hydrocarbon group or a substituted hydrocarbon group to each other may be different even in the same ^.R 1 ~ R ⁸ may be bonded to each other.)
An unsaturated onium cation represented by:
(III) The following general formula

^(R 1 ^{to R 12} is a hydrogen atom, a halogen atom, a functional group, ^.R 1 ^{to R 12} representing a hydrocarbon group or a substituted hydrocarbon group to each other may be different even in the same ^.R 1 ~ R ¹² may be bonded to each other.)
A saturated ring onium cation represented by:
(IV) The following general formula

(R _represents an alkyl group of C 1 ~C _8.)
The chain onium cation represented by the formula is more preferable.

R ^{1 to} R ¹² in the above (I) to (III) are preferably a hydrogen atom, a fluorine atom, an amino group, an imino group, an amide group, an ether group, an ester group, a hydroxyl group, a carboxyl group, a carbamoyl group, Examples thereof include a cyano group, a sulfone group, a sulfide group, a straight chain, branched chain, or cyclic hydrocarbon group having 1 to 18 carbon atoms that may contain a nitrogen atom, an oxygen atom, a sulfur atom, and the like, a fluorine group, and the like. Among these, a hydrogen atom, a fluorine atom, a cyano group, a sulfone group, a hydrocarbon group having 1 to 8 carbon atoms, and a fluorocarbon group are more preferable.

で表されるオニウムカチオン；トリエチルメチルアンモニウム、ジメチルエチルプロピルアンモニウム、ジエチルメチルメトキシエチルアンモニウム、トリメチルプロピルアンモニウム、トリメチルブチルアンモニウム、トリメチルヘキシルアンモニウム等の鎖状オニウムカチオン；等である。 Among the above onium cations, particularly preferred is an onium cation in which X in the above formula (1) is N, and most preferred is the following general formula

A chain onium cation such as triethylmethylammonium, dimethylethylpropylammonium, diethylmethylmethoxyethylammonium, trimethylpropylammonium, trimethylbutylammonium, trimethylhexylammonium; and the like.

Y in the above formula (2) represents C, Si, N, P, S or O. Preferably Y is N. R ′ in the above formula (2) represents a hydrogen atom, a halogen atom, a functional group or an organic group.
The R ′ may be the same as or different from each other. The R ′ may be bonded to each other. t is 2, 3 or 4. Note that t is a value determined by the valence of Y.

  Preferable specific examples of the cation in the above formula (2) include cations represented by the above (I) to (III) (cations in which R in the above formula (4) is replaced with R ′); methylammonium, ethyl Ammonium, propyl ammonium, butyl ammonium, hexyl ammonium, dimethyl ammonium, diethyl ammonium, dipropyl ammonium, dibutyl ammonium, dihexyl ammonium, ethyl methyl ammonium, butyl methyl amine trimethyl ammonium, trimethyl ammonium, triethyl ammonium, tripropyl ammonium, tributyl ammonium, Alkylammonium cations such as dimethylethylammonium and diethylmethylammonium; trimethylethylenediamine, diazabicyclooctane, Triamine, cationic ammonium in molecule such as hexamethylene tetramine having two or more tertiary amines; guanidinium and alkyl substitution products; and the like. Among these, tertiary ammonium cations such as trimethylammonium, triethylammonium, tripropylammonium, tributylammonium, dimethylethylammonium, and diethylmethylammonium are preferable.

A ⁻ in the above formula (1) and / or B ⁻ in the above formula (2) is represented by the following general formula (3). By setting it as such a structure, the outstanding ion conductivity can be achieved and it can be excellent in pH stability.

Z in the above formula (3) represents B, C, S, N, O, Al, Si, P, As, or Se. Preferably it is C, N or S, more preferably C or N. M ¹ and M ² in the formula (3) each represent any suitable linking group. The linking groups may be the same or different from each other. The linking group is preferably —S—, —O—, —SO ₂ — or —CO—, and more preferably —SO ₂ — or —CO—. Q in the above formula (3) represents a hydrogen atom, a halogen atom, a functional group or an organic group. Examples of the halogen atom include a fluorine atom and a chlorine atom. Examples of the functional group include a cyano group, a thiocyanate group, an amide group, and a nitro group. As the organic _{group, C p F (2p + 1} -q) H q, OC p F (2p + 1-q) H q, SO 2 C p F (2p + 1-q) H q, CO 2 C p F (2p + 1-q) H _q , SO ₃ C ₆ F _5-r H _r (wherein 1 ≦ p ≦ 6, 0 <q ≦ 13, 0 <r ≦ 5) and the like. Among them, preferably, a cyano group, a thiocyanate group, an amide _{group, C p F (2p + 1} -q) H q, SO 2 C p F (2p + 1-q) H q. A in the formula (3) is an integer of 1 or more. b, c, d and e are integers of 0 or more. Here, a, d, and e are determined by the valence of Z.

  Preferable specific examples of the anion represented by the above formula (3) include dicyanoamide anion (DCA), thiocyanate anion, tricyanomethide anion (TCM), cyanooxy anion (CYO) and the like. This is because they can be excellent in corrosion resistance of electrodes and the like.

A ⁻ in the above formula (1) and / or B ⁻ in the above formula (2) may be an anion other than the anion represented by the above formula (3). Specific examples of the anion include dicarboxylic acid anions (mono or dianion) such as phthalic acid and maleic acid; sulfate anions such as methyl sulfate and ethyl sulfate; hexafluorophosphate ion, hexafluoroarsenate ion, hexafluoroantimony Fluorine-containing inorganic ions such as acid ions, hexafluoroniobate ions, hexafluorotantalate ions; carboxylate ions such as salicylate ions, benzoate ions, and adipate ions; benzenesulfonate ions, toluenesulfonate ions, dodecylbenzenesulfone Sulfonic acid ions such as acid ions, trifluoromethanesulfonic acid ions and perfluorobutanesulfonic acid; inorganic oxoacid ions such as boric acid ions and phosphate ions; bis (trifluoromethanesulfonyl) imide ions (T SI), imide ions such as bis (pentafluoroethanesulfonyl) imide ion; methide ions such as tris (trifluoromethanesulfonyl) methide ion; tetrafluoroborate anion, perfluoroalkylfluoroborate ion, borodicatecholate, borodiglycolate, boro Examples thereof include boron ions such as disalicylate, borotetrakis (trifluoroacetate) and bis (oxalato) borate; phosphate ions such as perfluoroalkylfluorophosphate ions; and the like.

  In addition to the above, the electrolytic solution material of the present invention may contain an alkali metal salt and / or an alkaline earth metal salt. By including such a metal salt, it can be particularly suitable as a battery electrolyte. As the alkali metal salt, a lithium salt, a sodium salt, or a potassium salt is preferable. As the alkaline earth metal salt, calcium salt and magnesium salt are preferable. Lithium salts are particularly preferably used when used in lithium secondary batteries described later.

Any appropriate anion can be adopted as the anion of the alkali metal salt and / or alkaline earth metal salt. Therefore, it may be an anion represented by the above formula (3) or an anion other than that. An anion capable of forming a metal salt having a large dissociation constant is preferable. Specifically, alkali metal salts or alkaline earth metal salts of trifluoromethanesulfonic acid such as LiCF ₃ SO ₃ , NaCF ₃ SO ₃ , KCF ₃ SO ₃ ; LiN (CF ₃ SO ₃ ) ₃ , LiN (CF ₃ CF ₃ SO ₂ ) ₂ alkali metal salt or alkaline earth metal salt of perfluoroalkanesulfonic acid imide; LiPF ₆ , NaPF ₆ , alkali metal salt or alkaline earth metal salt of hexafluorophosphoric acid such as KPF ₆ ; LiClO _4, perchloric acid alkali metal salts and alkaline earth metal salts of NaClO ₄ and the _like; LiBF 4, tetrafluoroborate of NaBF _{4 such; LiAsF 6, LiI, NaI,} NaAsF 6, alkali metal salts of KI and the like; etc. Is preferred. Among these, from the viewpoint of solubility and ionic conductivity, LiPF ₆ , LiBF ₄ , LiAsF ₆ , and alkali metal salts or alkaline earth metal salts of perfluoroalkanesulfonic acid imide are preferable.

The electrolyte material may contain other electrolyte salts. Specific examples include quaternary ammonium salts of perchloric acid such as tetraethylammonium perchlorate; quaternary ammonium salts of tetrafluoroboric acid such as (C ₂ H ₅ ) ₄ NBF ₄ ; (C ₂ H ₅ ) ₄ NPF ₆ Quaternary ammonium salts such as (CH ₃ ) ₄ P · BF ₄ , quaternary phosphonium salts such as (C ₂ H ₅ ) ₄ P · BF _4, etc. are preferred, from the viewpoint of solubility and ionic conductivity. A quaternary ammonium salt is preferred.

B. Electrolytic Solution The electrolytic solution of the present invention can be obtained by dissolving the above electrolytic solution material in a solvent. Any appropriate solvent can be adopted as the solvent. Preferably, the solvent includes an organic solvent. This is because the ionic conductivity can be further improved. Specific examples of the organic solvent include 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, crown ether, triethylene glycol methyl ether, tetraethylene glycol dimethyl ether, dioxane and other ethers; ethylene carbonate, propylene carbonate Carbonates such as diethyl carbonate and methyl ethyl carbonate; chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diphenyl carbonate and methyl phenyl carbonate; ethylene carbonate, propylene carbonate, 2,3-dimethyl ethylene carbonate, Cyclic carbonates such as butylene carbonate, vinylene carbonate, 2-vinylethylene carbonate; methyl formate, methyl acetate, propionic acid, methyl propionate, ethyl acetate, propyl acetate, Aliphatic carboxylic acid esters such as ruthenium and amyl acetate; Aromatic carboxylic acid esters such as methyl benzoate and ethyl benzoate; Carboxylic acid esters such as γ-butyrolactone, γ-valerolactone and δ-valerolactone; Phosphate esters such as trimethyl acid, ethyldimethyl phosphate, diethylmethyl phosphate, triethyl phosphate; nitriles such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, etc. Amides such as N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidinone, N-methylpyrrolidone, N-vinylpyrrolidone; dimethylsulfone, ethylmethylsulfone , Diethyls Sulfur compounds such as Hong, sulfolane, 3-methylsulfolane, 2,4 dimethylsulfolane: alcohols such as ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, Ethers such as 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran; sulfoxides such as dimethyl sulfoxide, methylethyl sulfoxide, diethyl sulfoxide; benzonitrile, Aromatic nitriles such as tolunitrile; nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4, Examples include 5,6-tetrahydro-2 (1H) -pyrimidinone, 3-methyl-2-oxazolidinone, and the like. These can be used alone or in combination of two or more. Among these, carbonate esters, aliphatic esters, and ethers are more preferable, carbonates are more preferable, and cyclic esters such as γ-butyrolactone and γ-valerolactone are particularly preferable.

  When preparing the electrolytic solution, the blending amount of the electrolyte salt represented by the formula (1) and the electrolyte salt represented by the formula (2) can be set to any appropriate value depending on the purpose. . The amount is preferably 1 to 900 parts by weight, more preferably 10 to 400 parts by weight, and particularly preferably 30 to 100 parts by weight with respect to 100 parts by weight of the solvent. By setting the blending amount of the electrolyte salt in such a range, excellent ionic conductivity can be achieved. Furthermore, precipitation of the electrolyte salt can be suppressed.

  The blending ratio of the electrolyte salt represented by the above formula (1) and the electrolyte salt represented by the above formula (2) can be set to any appropriate value. The ratio is preferably 95: 5 to 5:95, more preferably 90:10 to 50:50, and particularly preferably 90:10 to 55:45. The ratio is a weight ratio.

  The electrolytic solution of the present invention may contain water. The water content in the electrolytic solution is preferably 0.01 to 10% by weight, more preferably 0.01 to 5% by weight, and particularly preferably 0.01 to 2% by weight. By setting the water content in such a range, the voltage resistance, heat resistance, and life of the electrochemical device can be stabilized. Furthermore, it can be excellent in chemical conversion when repairing the anodized film.

  The electrolyte solution material of the present invention may contain other optional components in addition to the above. Examples of other optional components include inorganic oxide fine particles and additives.

  As the inorganic oxide fine particles, those having non-electron conductivity and electrochemical stability are preferable, and those having ion conductivity are more preferable. Examples of such inorganic oxide fine particles include ceramic fine particles such as α, β, γ-alumina, silica, titania, zirconia, magnesia, barium titanate, and hydrotalcite.

  Any appropriate additive can be adopted as the additive depending on the purpose. Examples of the purpose of adding the additive include improvement of electrical conductivity, improvement of thermal stability, suppression of electrode deterioration due to hydration and dissolution, suppression of gas generation, improvement of withstand voltage, improvement of wettability, and the like. . Examples of such additives include nitro compounds such as p-nitrophenol, m-nitroacetophenone, and p-nitrobenzoic acid, dibutyl phosphate, monobutyl phosphate, dioctyl phosphate, monooctyl phosphonate, monophosphate Boron compounds such as phosphorus compounds such as boric acid or boric acid and polyhydric alcohols (ethylene glycol, glycerin, mannitol, polyvinyl alcohol, etc.) and polysaccharides, nitroso compounds, urea compounds, arsenic compounds, titanium compounds, Silicic acid compounds, aluminate compounds, nitric acid and nitrous acid compounds, 2-hydroxy-N-methylbenzoic acid, benzoic acids such as di (tri) hydroxybenzoic acid, gluconic acid, dichromic acid, sorbic acid, dicarboxylic acid, EDTA , Fluorocarboxylic acid, picric acid, suberic acid, adipine , Sebacic acid, heteropolyacid (tungstic acid, molybdic acid), gentisic acid, borodigentisic acid, salicylic acid, N-aminosalicylic acid, borodiprotocatechuic acid, borodipyrocatechol, bamonic acid, boric acid, borodiresorcylic acid, resorcylic acid, Borodiprotocaquelic acid, glutaric acid, acids such as dithiocarbamic acid, esters thereof, amides and salts thereof, silane coupling agents, silicon compounds such as silica and aminosilicate, amine compounds such as triethylamine and hexamethylenetetramine, L- Amino acids, benzool, polyhydric phenol, 8-oxyquinoline, hydroquinone, N-methylpyrocatechol, quinoline and thioanisole, thiocresol, thiobenzoic acid and other sulfur compounds, sorbitol, L-histidine and the like It is.

The ionic conductivity of the electrolytic solution of the present invention is typically 10 mS / cm or more, preferably 15 mS / cm or more, and more preferably 20 mS / cm or more. In the present specification, “ion conductivity” refers to a value measured at 25 ° C.
The pH change amount of the electrolytic solution of the present invention is typically 6 or less, preferably 5.5 or less, and more preferably 5 or less. By providing such pH stability, corrosion of various members of the electrochemical device can be suppressed. A method for measuring the amount of change in pH will be described later.
Thus, the electrolytic solution of the present invention can simultaneously achieve excellent ionic conductivity and excellent pH stability.

C. Applications The electrolyte material and electrolyte of the present invention can be used in any electrochemical device. Typically, it is suitably used for lithium secondary batteries, electrolytic capacitors, electric double layer capacitors and the like. Each will be described below.

C-1. Lithium Secondary Battery The lithium secondary battery of the present invention is typically composed of a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the above electrolyte as basic components. As described above, when the electrolytic solution material of the present invention is used for a lithium secondary battery, the electrolytic solution material may contain a lithium salt as an electrolyte.

C-2. Electrolytic Capacitor The electrolytic capacitor of the present invention typically has an anode foil 1, a cathode foil 2, and a separator (electrolytic paper) 3 sandwiched between the anode foil and the cathode foil, as shown in FIG. And a capacitor element 10 having lead wires 4 and 4; the electrolyte; a bottomed cylindrical outer case; and a sealing body for sealing the outer case. More specifically, in the electrolytic capacitor of the present invention, the capacitor element is impregnated with the electrolytic solution, the capacitor element is housed in a bottomed cylindrical outer case, and a sealing body is attached to the opening of the outer case. It can be obtained by drawing the end of the outer case and sealing the outer case.

  As the material for forming the anode foil and / or the cathode foil, aluminum, tantalum, niobium and the like are suitable. As a specific example, one embodiment of an aluminum electrolytic capacitor is shown in a schematic cross-sectional view of FIG.

  As the anode foil 1, for example, an aluminum foil having a purity of 99% or more is subjected to surface expansion treatment by etching chemically or electrochemically in an acidic solution, and thereafter, ammonium borate, ammonium phosphate, ammonium adipate, or the like is used. A chemical conversion treatment performed in an aqueous solution and an anodized film layer formed on the surface thereof can be used. Examples of the cathode foil 2 include one or more metal nitrides selected from titanium nitride, zirconium nitride, tantalum nitride, and niobium nitride, and / or titanium, zirconium, tantalum, and niobium on part or all of the surface. An aluminum foil in which a film composed of one or more metals selected from the above can be used. Examples of the method for forming the film include a vapor deposition method, a plating method, a coating method, and the like. As a portion for forming the film, the entire surface of the cathode foil may be coated, or if necessary, one of the cathode foils may be coated. A part, for example, only one surface of the cathode foil may be coated with metal nitride and / or metal.

The lead wire 4 is preferably composed of a connection part (not shown) in contact with the anode foil and the cathode foil, a round bar part 4a, and an external connection part 4b. Typically, the lead wire 4 is electrically connected to the anode foil and the cathode foil by means such as stitching or ultrasonic welding at the connection portion. The connecting portion and the round bar portion 4a are preferably formed from high-purity aluminum. The external connection portion 4b is preferably formed from a copper-plated steel wire subjected to solder plating. In addition, an aluminum oxide layer may be formed on a part of or the whole surface of the connecting portion with the cathode foil 2 and the round bar portion 4a by anodizing treatment with an ammonium borate aqueous solution, an ammonium phosphate aqueous solution, an ammonium adipate aqueous solution, or the like. An insulating layer such as a ceramic coating layer made of Al ₂ O ₃ , SiO ₂ , ZrO ₂ or the like can be formed.

  The outer case is preferably made of aluminum. The sealing body typically includes through holes for leading out lead wires. The sealing body is preferably made of an elastic rubber such as butyl rubber. Specifically, raw rubber made of a copolymer of isobutylene and isoprene is added to a reinforcing agent (carbon black, etc.), a filler (clay, talc, calcium carbonate, etc.), a processing aid (stearic acid, zinc oxide, etc.), After adding a kneading agent and kneading, a rubber elastic body rolled and molded can be used. Examples of vulcanizing agents include alkylphenol formalin resins; peroxides (dicumyl peroxide, 1,1-di- (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5- Di- (t-butylperoxy) hexane etc.); quinoids (p-quinone dioxime, p, p'-dibenzoylquinone dioxime etc.); sulfur etc. can be used. It is more preferable to coat the surface of the sealing body with a resin such as Teflon (registered trademark) or to attach a plate such as bakelite because the permeability of the solvent vapor can be reduced. As the separator 3, as described above, paper such as manila paper or kraft paper is usually used, but non-woven fabric such as glass fiber, polypropylene, and polyethylene can also be used.

  The electrolytic capacitor of the present invention may have a hermetic seal structure or a structure sealed in a resin case (for example, described in JP-A-8-148384). In the case of an aluminum electrolytic capacitor with a rubber seal, gas permeates through rubber to some extent, so that the solvent evaporates from the inside of the capacitor to the atmosphere in a high temperature environment, and from the atmosphere to the inside of the capacitor in a high temperature and high humidity environment Moisture may be mixed into the capacitor, and under these harsh environments, the capacitor may cause undesirable characteristic changes such as a decrease in capacitance. On the other hand, in a capacitor having a hermetic seal structure or a structure sealed in a resin case, since the amount of gas permeation is extremely small, stable characteristics can be exhibited even in such a severe environment.

C-3. Electric Double Layer Capacitor The electric double layer capacitor of the present invention is typically composed of a negative electrode, a positive electrode and the above electrolyte as basic constituent elements. As a preferred embodiment, the above electrolytic solution is contained in an electrode element composed of a positive electrode and a negative electrode arranged to face each other.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. Unless otherwise specified, parts and% in the examples are based on weight.

(Example 1)
N-ethyl-N′-methylimidazolium tricyanomethide (hereinafter referred to as EMImTCM) 30 parts, triethylammonium tricyanomethide (hereinafter referred to as TEATCM) 5 parts, γ-butyrolactone (hereinafter referred to as GBL) 65 parts And 2 parts of water were mixed to obtain an electrolytic solution.

(Example 2)
25 parts of EMImTCM, 10 parts of TEATCM, 65 parts of GBL, and 2 parts of water were mixed to obtain an electrolytic solution.

(Example 3)
20 parts of EMImTCM, 15 parts of TEATCM, 65 parts of GBL, and 2 parts of water were mixed to obtain an electrolytic solution.

Example 4
30 parts of EMImTCM, 5 parts of triethylammonium phthalate (hereinafter referred to as TEAPh), 65 parts of GBL, and 2 parts of water were mixed to obtain an electrolytic solution.

(Example 5)
30 parts of N-ethyl-N′-methylimidazolium phthalate, 5 parts of TEATCM, 65 parts of GBL, and 2 parts of water were mixed to obtain an electrolytic solution.

(Example 6)
30 parts of triethylmethylammonium tricyanomethide, 5 parts of TEATCM, 65 parts of GBL, and 2 parts of water were mixed to obtain an electrolytic solution.

(Comparative Example 1)
An electrolytic solution was obtained by mixing 35 parts of EMImTCM, 65 parts of GBL, and 2 parts of water.

(Comparative Example 2)
20 parts of TEAPh, 65 parts of GBL, and 0.5 part of water were mixed to obtain an electrolytic solution.

The pH and ionic conductivity of the obtained electrolytic solution were measured by the following methods. The measurement results are summarized in Table 1.
<PH measurement>
30 mL of the electrolytic solution obtained above is put into an H-type cell with a glass diaphragm, a platinum electrode is immersed, and electricity is used at 20 mA using a DC power supply (manufactured by Matsusada Precision Co., Ltd., product number: PL-650-0.1). Degradation was carried out for 4 hours. The pH of the electrolytic solution before and after electrolysis was measured with a pH meter (IQ Scientific Instruments, Inc., product number: IQ150). The amount of change in pH was calculated from the obtained value.
<Ionic conductivity>
The ionic conductivity of the electrolytic solution obtained above was measured at 25 ° C. by a complex impedance method using a SUS electrode. As a measuring device, an impedance analyzer SI1260 (manufactured by Solartron) was used.

  As is clear from Table 1, the electrolytic solutions of the examples of the present invention were excellent in ionic conductivity and pH stability. On the other hand, although the electrolytic solution of Comparative Example 1 was excellent in ionic conductivity, it was inferior in pH stability. Moreover, although the electrolytic solution of Comparative Example 2 was excellent in pH stability, it was inferior in ionic conductivity. From this, by dissolving two kinds of electrolyte salts having anions represented by the above formula (3) in a solvent, an electrolytic solution capable of simultaneously achieving excellent ionic conductivity and excellent pH stability is obtained. You can get.

  Electrolyte materials and electrolytes of the present invention include primary batteries, batteries having a charging / discharging mechanism such as secondary batteries and fuel cells, electrolytic capacitors, electric double layer capacitors, solar cells, and electrochemical devices such as electrochromic display elements. Can be suitably used. Among these, it can be particularly suitably used for lithium secondary batteries, electrolytic capacitors, and electric double layer capacitors.

(A) is a schematic perspective view which shows one form of the capacitor | condenser element of an electrolytic capacitor, FIG.1 (b) is a cross-sectional schematic diagram which shows one form of an aluminum electrolytic capacitor.

Explanation of symbols

1 Anode foil 2 Cathode foil 3 Separator (electrolytic paper)
4 Lead wire 10 Capacitor element

Claims (5)

An electrolyte material comprising an electrolyte salt represented by the general formula (1) and an electrolyte salt represented by the general formula (2),

The cation in the general formula (1) is represented by the following general formula:

An onium cation represented by ¹ ~ R ¹² Is a hydrogen atom, fluorine atom, amino group, imino group, amide group, ether group, ester group, hydroxyl group, carboxyl group, carbamoyl group, cyano group, sulfone group, sulfide group, linear, branched or cyclic Any one of a hydrocarbon group having 1 to 18 carbon atoms and a fluorine group that may contain a nitrogen atom, an oxygen atom, a sulfur atom, etc., and is not a hydrogen atom when directly connected to the N atom of the cation center), Any of triethylmethylammonium, dimethylethylpropylammonium, diethylmethylmethoxyethylammonium, trimethylpropylammonium, trimethylbutylammonium, trimethylhexylammonium,
The cation in the general formula (2) is a tertiary ammonium cation,
A in the general formula (1) ⁻ And / or B in the general formula (2) ⁻ Is a tricyanomethide anion,
Electrolyte material. Electrolyte the electrolyte material obtained by dissolving in a solvent of claim 1. A lithium secondary battery using the electrolytic solution according to claim 2 . An electrolytic capacitor using the electrolytic solution according to claim 2 . An electric double layer capacitor using the electrolytic solution according to claim 2 .

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