JP2013045887A - Electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device which suppresses deterioration in characteristics of an electrochemical cell caused by decomposition of an electrolyte solvent and corrosion of a collector due to hydrogen fluoride generated by decomposition of an electrolyte.SOLUTION: Provided is an electrochemical device using an electrolytic solution containing an electrolyte and a nonaqueous solvent. An anion component of the electrolyte is a boron-containing anion represented by the general formula (1): B(CN)R(In the formula, each of R independently represents a perfluoroalkyl group with the carbon number of 1 to 4, and n represents an integer of 1 to 3. When n is 1 or 2, two R may couple to each other to form a ring.)

Description

  The present invention relates to electrochemical devices such as electrochemical capacitors and secondary batteries.

  Electrochemical devices such as electrochemical capacitors and secondary batteries using a non-aqueous electrolyte can increase the withstand voltage because of the high electrolysis voltage of the solvent, and can store a large amount of energy. The water content of the electrolytic solution is strictly controlled, and an electrolytic solution having a water content of several tens of ppm or less is usually used. However, deterioration of the cell characteristics due to moisture adsorbed on the pores of the active material is a problem. For example, in electrochemical devices such as electrochemical capacitors and secondary batteries, tetrafluoroborate, hexafluorophosphate, etc. are used as the electrolyte of the electrolytic solution, but these electrolytes react with water and become fluorinated. It is known to produce hydrogen fluoride. The generated hydrogen fluoride causes corrosion of the current collector, decomposition of the electrolyte solvent, and the like, and thus deteriorates various characteristics of the electrochemical device. In addition, since decomposition | disassembly of these electrolytes is notably caused when heat is added, generation | occurrence | production of hydrogen fluoride becomes a big problem especially when developing the electrochemical device corresponding to reflow, for example.

In Patent Document 1, a kind of boron compound (X ⁺ [(Rf) _n BF _4-n ] ⁻ (where X ⁺ is an alkali metal ion or onium), which is an electrolyte having a small tendency to generate hydrogen fluoride by hydrolysis. Represents an ion, Rf represents a perfluoroalkyl group, and n represents an integer of 1 to 4. When n is 2 or more, a plurality of Rf may be different from each other. It has been proposed to use an electrolytic solution in which Rf is bonded to each other to form a ring structure with boron. However, when n is 1 to 3, generation of hydrogen fluoride cannot be completely suppressed, and it is necessary to prepare a large facility in order to synthesize a compound with n of 4. Further, in Patent Document 2, it is proposed to add lithium borate that reacts with hydrogen fluoride to the electrolytic solution in order to remove hydrogen fluoride generated by decomposition of the electrolyte (LiPF ₆ ). In Patent Document 2, the reaction between hydrogen fluoride and lithium borate is considered as follows.
Li ₂ B ₄ O ₇ .10H ₂ O + 12HF → Li ₂ O.4BF ₃ + 16H ₂ O
Although hydrogen fluoride is removed by this reaction, lithium borate added to the electrolytic solution is decahydrate, and in addition, water is generated by the reaction, so that the generated water further decomposes the electrolyte. A new problem caused by water occurs. In addition, Patent Document 3 describes a boron-containing organic acid and a salt thereof as an acid and a salt for synthesizing an ionic liquid or a catalyst, but these acids and salts are described here. However, the physical properties of the salt and the properties when applied to a device are not described at all.

JP 2002-63934 A JP 2005-71617 A JP 2008-517002 A

  An object of the present invention is to provide an electrochemical device that suppresses deterioration of characteristics caused by corrosion of a current collector due to hydrogen fluoride generated by decomposition of an electrolyte, decomposition of an electrolyte solvent, and the like.

As a result of intensive studies by the present inventors, it has been found that the above-mentioned problems can be solved by using a specific boron-containing anion as the anion component of the electrolyte dissolved in the electrolytic solution, and the present invention has been completed. That is, the present invention provides an electrochemical device using an electrolytic solution containing a nonaqueous solvent and an electrolyte, wherein the anion component of the electrolyte is a boron-containing anion represented by the following general formula (1). provide.
^{_{B - (CN) n R 4}} -n (1)
(In the formula, R independently represents a perfluoroalkyl group having 1 to 4 carbon atoms, n represents an integer of 1 to 3, and when n is 1 or 2, two R's are bonded to each other. To form a ring.)

According to the present invention, by using a specific boron-containing anion as the anion component of the electrolyte dissolved in the electrolytic solution, hydrogen fluoride is not generated due to decomposition of the electrolyte even in the presence of water. Deterioration is suppressed, and deterioration of electrical characteristics such as electrostatic capacity and charge / discharge efficiency of the electrochemical device can be prevented. In addition, decomposition of the electrolytic solution due to the acid is suppressed, and expansion of the electrochemical device and increase in internal resistance can be prevented. Furthermore, since the specific boron-containing anion used in the present invention is bulkier than BF ₄ ⁻ , the interaction with the cation is weak, the solubility is higher than that of an ammonium salt using BF ₄ ⁻ as an anion component, and the low temperature Can be used in a wide temperature range from high to high.

It is side surface sectional drawing of the electrochemical device of one Embodiment of this invention. It is a top view of the electrochemical device of one embodiment of the present invention. It is side surface sectional drawing of the electrochemical device of one Embodiment of this invention. It is side surface sectional drawing of the electrochemical device of the state which the capacitor container expanded.

（１−１） （１−２） （１−３）

（１−４） （１−５） （１−６）

（１−７） （１−８） （１−９） The electrochemical device of the present invention uses an electrolytic solution containing a nonaqueous solvent and an electrolyte, and uses a boron-containing anion represented by the following general formula (1) as the anion component of the electrolyte.
^{_{B - (CN) n R 4}} -n (1)
(In the formula, R independently represents a perfluoroalkyl group having 1 to 4 carbon atoms, n represents an integer of 1 to 3, and when n is 1 or 2, two R's are bonded to each other. To form a ring.)
By making n an integer of 1 to 3 and making the structure of the boron-containing anion asymmetric, the solubility of the electrolyte can be enhanced.
Examples of the perfluoroalkyl group having 1 to 4 carbon atoms represented by R include trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, heptafluoroisopropyl group, nonafluorobutyl group, nonafluoroisobutyl group, nonafluorotert. -A butyl group etc. are mentioned.
Specific examples of the boron-containing anion include the following.

(1-1) (1-2) (1-3)

(1-4) (1-5) (1-6)

(1-7) (1-8) (1-9)

（２）
（式中、Ｒ₁〜Ｒ₄はそれぞれ炭素数が１〜６の１価の飽和炭化水素基又は１価のヘテロ原子含有飽和炭化水素基を示す。）
Ｒ₁〜Ｒ₄によって表される炭素数が１〜６の１価の飽和炭化水素基又は１価のヘテロ原子含有飽和炭化水素基としては、例えばメチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｓｅｃ−ブチル基、ｔｅｒｔ−ブチル基、ｎ−ペンチル基、２−ペンチル基、３−ペンチル基、イソペンチル基、ｔｅｒｔ−ペンチル、ネオペンチル基、ｎ−ヘキシル基、イソヘキシル基などの炭素数が１〜６のアルキル基、メトキシメチル基、エトキシメチル基、メトキシエチル基、エトキシエチル基などの炭素数が１〜６のアルコキシアルキル基などが挙げられる。Ｒ₁〜Ｒ₄は、好ましくはメチル基、エチル基などの炭素数が１〜３のアルキル基である。 The cation component of the electrolyte can be used as the cation component of the electrolyte for an electrochemical device of the present invention as long as it is a cation component of an electrolyte that is usually used in an electrochemical device. For example, as the cation component, cations of the following general formulas (2) to (4) may be mentioned.

(2)
(Wherein R _{1 to} R ₄ each represent a monovalent saturated hydrocarbon group having 1 to 6 carbon atoms or a monovalent heteroatom-containing saturated hydrocarbon group.)
Examples of the monovalent saturated hydrocarbon group having 1 to 6 carbon atoms represented by R _{1 to} R ₄ or the monovalent heteroatom-containing saturated hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, and isopropyl. Group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-pentyl group, 3-pentyl group, isopentyl group, tert-pentyl, neopentyl group, n-hexyl group, Examples thereof include an alkyl group having 1 to 6 carbon atoms such as an isohexyl group, an alkoxyalkyl group having 1 to 6 carbon atoms such as a methoxymethyl group, an ethoxymethyl group, a methoxyethyl group and an ethoxyethyl group. R _{1 to} R ₄ are preferably alkyl groups having 1 to 3 carbon atoms such as a methyl group and an ethyl group.

（３）
（式中、Ｒ₅及びＲ₆はそれぞれ炭素数が１〜６の１価の飽和炭化水素基又は１価のヘテロ原子含有飽和炭化水素基を示し、Ｘは二価の飽和炭化水素基又は二価のヘテロ原子含有飽和炭化水素基であって、結合している窒素原子と共にヘテロ環を形成する。）
Ｒ₅及びＲ₆によって表される炭素数が１〜６の１価の飽和炭化水素基又は１価のヘテロ原子含有飽和炭化水素基としては、例えばメチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｓｅｃ−ブチル基、ｔｅｒｔ−ブチル基、ｎ−ペンチル基、２−ペンチル基、３−ペンチル基、イソペンチル基、ｔｅｒｔ−ペンチル、ネオペンチル基、ｎ−ヘキシル基、イソヘキシル基などの炭素数が１〜６のアルキル基、メトキシメチル基、エトキシメチル基、メトキシエチル基、エトキシエチル基などの炭素数が１〜６のアルコキシアルキル基などが挙げられる。Ｒ₅及びＲ₆は、好ましくはメチル基、エチル基などの炭素数が１〜３のアルキル基である。
Ｘによって表される二価の飽和炭化水素基又は二価のヘテロ原子含有飽和炭化水素基としては、例えばブタン−１，４−ジイル基、２−メチルブタン−１，４−ジイル基、２，３−ジメチルブタン−１，４−ジイル基、ペンタン−１，４−ジイル基、ペンタン−１，５−ジイル基、ヘキサン−１，６−ジイル基、ヘキサン−１，５−ジイル基、ヘキサン−２，５−ジイル基、ヘプタン−２，６−ジイル基などの炭素数が４〜７のアルキレン基、３−オキサペンタン−１，５−ジイル基、１，４−ジメチル−３−オキサペンタン−１，５−ジイル基などの炭素数が３〜４のオキサアルキレン基、３−アザ−３−メチルペンタン−１，５−ジイル基などの炭素数が３〜４のアザアルキレン基などが挙げられる。Ｘは、好ましくはブタン−１，４−ジイル基、ペンタン−１，５−ジイル基などの炭素数が４〜５のアルキレン基である。

(3)
(In the formula, R ₅ and R ₆ each represent a monovalent saturated hydrocarbon group having 1 to 6 carbon atoms or a monovalent heteroatom-containing saturated hydrocarbon group, and X represents a divalent saturated hydrocarbon group or a divalent saturated hydrocarbon group. A valent heteroatom-containing saturated hydrocarbon group that forms a heterocycle with the nitrogen atom to which it is attached.
Examples of the monovalent saturated hydrocarbon group having 1 to 6 carbon atoms or the monovalent heteroatom-containing saturated hydrocarbon group represented by R ₅ and R ₆ include a methyl group, an ethyl group, an n-propyl group, and isopropyl. Group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-pentyl group, 3-pentyl group, isopentyl group, tert-pentyl, neopentyl group, n-hexyl group, Examples thereof include an alkyl group having 1 to 6 carbon atoms such as an isohexyl group, an alkoxyalkyl group having 1 to 6 carbon atoms such as a methoxymethyl group, an ethoxymethyl group, a methoxyethyl group and an ethoxyethyl group. R ₅ and R ₆ are preferably alkyl groups having 1 to 3 carbon atoms such as a methyl group and an ethyl group.
Examples of the divalent saturated hydrocarbon group or divalent heteroatom-containing saturated hydrocarbon group represented by X include a butane-1,4-diyl group, a 2-methylbutane-1,4-diyl group, and 2,3. -Dimethylbutane-1,4-diyl group, pentane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, hexane-1,5-diyl group, hexane-2 , 5-diyl group, heptane-2,6-diyl group and the like, an alkylene group having 4 to 7 carbon atoms, 3-oxapentane-1,5-diyl group, 1,4-dimethyl-3-oxapentane-1 Oxaalkylene groups having 3 to 4 carbon atoms such as 1,5-diyl group, and azaalkylene groups having 3 to 4 carbon atoms such as 3-aza-3-methylpentane-1,5-diyl group. X is preferably an alkylene group having 4 to 5 carbon atoms such as a butane-1,4-diyl group or a pentane-1,5-diyl group.

（４）
（式中、Ｘは二価の飽和炭化水素基又は二価のヘテロ原子含有飽和炭化水素基であって、結合している窒素原子と共にヘテロ環を形成し、Ｙは二価の飽和炭化水素基又は二価のヘテロ原子含有飽和炭化水素基であって、結合している窒素原子と共にヘテロ環を形成する。）
Ｘによって表される二価の飽和炭化水素基又は二価のヘテロ原子含有飽和炭化水素基としては、例えばブタン−１，４−ジイル基、２−メチルブタン−１，４−ジイル基、２，３−ジメチルブタン−１，４−ジイル基、ペンタン−１，４−ジイル基、ペンタン−１，５−ジイル基、ヘキサン−１，６−ジイル基、ヘキサン−１，５−ジイル基、ヘキサン−２，５−ジイル基、ヘプタン−２，６−ジイル基などの炭素数が４〜７のアルキレン基、３−オキサペンタン−１，５−ジイル基、１，４−ジメチル−３−オキサペンタン−１，５−ジイル基などの炭素数が３〜４のオキサアルキレン基、３−アザ−３−メチルペンタン−１，５−ジイル基などの炭素数が３〜４のアザアルキレン基などが挙げられる。Ｘは、好ましくはブタン−１，４−ジイル基、ペンタン−１，５−ジイル基などの炭素数が４〜５のアルキレン基である。
Ｙによって表される二価の飽和炭化水素基又は二価のヘテロ原子含有飽和炭化水素基としては、例えばブタン−１，４−ジイル基、２−メチルブタン−１，４−ジイル基、２，３−ジメチルブタン−１，４−ジイル基、ペンタン−１，４−ジイル基、ペンタン−１，５−ジイル基、ヘキサン−１，６−ジイル基、ヘキサン−１，５−ジイル基、ヘキサン−２，５−ジイル基、ヘプタン−２，６−ジイル基などの炭素数が４〜７のアルキレン基、３−オキサペンタン−１，５−ジイル基、１，４−ジメチル−３−オキサペンタン−１，５−ジイル基などの炭素数が３〜４のオキサアルキレン基、３−アザ−３−メチルペンタン−１，５−ジイル基などの炭素数が３〜４のアザアルキレン基などが挙げられる。Ｙは、好ましくはブタン−１，４−ジイル基、ペンタン−１，５−ジイル基などの炭素数が４〜５のアルキレン基である。

(4)
(In the formula, X is a divalent saturated hydrocarbon group or a divalent heteroatom-containing saturated hydrocarbon group, which forms a heterocycle together with the nitrogen atom bonded thereto, and Y is a divalent saturated hydrocarbon group. Or a divalent heteroatom-containing saturated hydrocarbon group that forms a heterocycle with the nitrogen atom to which it is attached.)
Examples of the divalent saturated hydrocarbon group or divalent heteroatom-containing saturated hydrocarbon group represented by X include a butane-1,4-diyl group, a 2-methylbutane-1,4-diyl group, and 2,3. -Dimethylbutane-1,4-diyl group, pentane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, hexane-1,5-diyl group, hexane-2 , 5-diyl group, heptane-2,6-diyl group and the like, an alkylene group having 4 to 7 carbon atoms, 3-oxapentane-1,5-diyl group, 1,4-dimethyl-3-oxapentane-1 Oxaalkylene groups having 3 to 4 carbon atoms such as 1,5-diyl group, and azaalkylene groups having 3 to 4 carbon atoms such as 3-aza-3-methylpentane-1,5-diyl group. X is preferably an alkylene group having 4 to 5 carbon atoms such as a butane-1,4-diyl group or a pentane-1,5-diyl group.
Examples of the divalent saturated hydrocarbon group or divalent heteroatom-containing saturated hydrocarbon group represented by Y include a butane-1,4-diyl group, a 2-methylbutane-1,4-diyl group, and 2,3. -Dimethylbutane-1,4-diyl group, pentane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, hexane-1,5-diyl group, hexane-2 , 5-diyl group, heptane-2,6-diyl group and the like, an alkylene group having 4 to 7 carbon atoms, 3-oxapentane-1,5-diyl group, 1,4-dimethyl-3-oxapentane-1 Oxaalkylene groups having 3 to 4 carbon atoms such as 1,5-diyl group, and azaalkylene groups having 3 to 4 carbon atoms such as 3-aza-3-methylpentane-1,5-diyl group. Y is preferably an alkylene group having 4 to 5 carbon atoms such as a butane-1,4-diyl group or a pentane-1,5-diyl group.

（２−１）

（２−２）
一般式（３）のカチオンの具体例としては、例えば下記カチオンなどが挙げられる。

（３−１）
一般式（４）のカチオンの具体例としては、例えば下記カチオンなどが挙げられる。

（４−１） Specific examples of the cation of the general formula (2) include the following cations.

(2-1)

(2-2)
Specific examples of the cation of the general formula (3) include the following cations.

(3-1)
Specific examples of the cation of the general formula (4) include the following cations.

(4-1)

The content of the anion component and cation component of the electrolyte in the electrolytic solution is preferably 0.8 mol or more and 3.0 mol or less, and 1.0 mol or more and 2.5 mol or less with respect to 1 liter of the nonaqueous electrolytic solution. Is more preferable.
Moreover, it is also possible to improve the high temperature reliability of a secondary battery or a hybrid capacitor by using an electrolyte comprising a salt of the boron-containing anion and alkali metal ion. The alkali metal ion is preferably lithium ion. The content of the electrolyte composed of a salt of the boron-containing anion and the alkali metal ion in the electrolytic solution is, for example, 0.8 mol to 3.0 mol with respect to 1 liter of the nonaqueous electrolytic solution, and 1.0 The molar amount is preferably from 2.0 to 2.0 mol.

Any non-aqueous solvent that is usually used in electrochemical devices can be used as the non-aqueous solvent for the electrochemical device of the present invention. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, cyclic esters, chain esters, cyclic ethers, chain ethers, nitrile compounds, and sulfur-containing compounds. These nonaqueous solvents can be used alone or in combination of two or more.
Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate (PC), butylene carbonate, vinylene carbonate and the like.
Examples of the chain carbonate include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, and methyl isopropyl carbonate.
Examples of the cyclic ester include γ-butyrolactone (GBL), γ-valerolactone, 3-methyl-γ-butyrolactone, 2-methyl-γ-butyrolactone, δ-valerolactone (DVL), and the like.
Examples of the chain ester include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, methyl butyrate, and methyl valerate.
Examples of the cyclic ether include 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane, 2-methyl-1,3-dioxolane and the like.
Examples of the chain ether include 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl 2,5-dioxahexanedioate, dipropyl ether and the like.
Examples of the nitrile compound include acetonitrile, propanenitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile and the like.
Examples of the sulfur-containing compound include sulfolane (SL), dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone (EMS), ethyl propyl sulfone (EPS), dimethyl sulfoxide and the like.
Among the above non-aqueous solvents, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate; γ-butyrolactone, γ-valerolactone, 3-methyl-γ-butyrolactone, 2-methyl-γ-butyrolactone, Cyclic esters such as δ-valerolactone; nitrile compounds such as glutaronitrile and adiponitrile; sulfur-containing compounds such as sulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, and ethylpropylsulfone are preferred. In recent years, reflow furnaces are increasingly used for soldering electronic components to circuit boards. There are various temperature profiles in the reflow furnace, but there are many cases where the temperature profile is about 250 ° C. Many electrochemical devices attached to the circuit board also exist, and when reflow soldering is performed, the inside of the film package 40 becomes a temperature close to the temperature in the reflow furnace. Therefore, when the boiling point of the non-aqueous solvent of the non-aqueous electrolyte is low, the non-aqueous solvent is vaporized during soldering using a reflow furnace, and the shape of the film package 40 and the characteristics of the electrochemical device may be deteriorated. is there. From the viewpoint of improving heat resistance and increasing the boiling point of the non-aqueous electrolyte, the non-aqueous solvent is preferable.

  Examples of the electrochemical device of the present invention include an electrochemical capacitor and a secondary battery. Examples of the electrochemical capacitor include an electric double layer capacitor, a lithium ion capacitor, a redox capacitor, and a hybrid capacitor.

  The electrochemical capacitor is formed of, for example, a positive electrode 10, a negative electrode 20, a power storage element B having a separator 30 between the positive electrode 10 and the negative electrode 20, a nonaqueous electrolytic solution in which an electrolyte is dissolved in a nonaqueous solvent, and a laminate film. (See FIG. 1). In addition, the electrochemical capacitor has a terminal 50 having one end connected to the electricity storage element B and the other end derived from the film package 40 (with the electricity storage element B and the non-aqueous electrolyte sealed). Polarizable electrode layers 12 and 22 are formed on the surfaces of current collectors 11 and 21 made of metal foil via a conductive adhesive (not shown), respectively. For example, the positive electrode 10 and the negative electrode 20 are disposed so that the polarizable electrode layer 12 of the positive electrode 10 and the polarizable electrode layer 22 of the negative electrode 20 face each other. The separator is formed from a material that can be impregnated with a nonaqueous electrolytic solution, such as cellulose, polypropylene, polyethylene, and fluorine resin. The separator 30 is disposed between the polarizable electrode layers 12 and 22 of the positive electrode 10 and the negative electrode 20 facing each other. A known structure used in a film package type electrochemical capacitor can be applied to the storage element B and the film package 40.

As the polarizable electrode layers 12 and 22, those having a known material and structure used in the polarizable electrode layer of an electrochemical capacitor can be used. For example, polyacene (PAS), polyaniline (PAN), activated carbon, carbon black, It contains an active material such as graphite and carbon nanotube, and may contain other components such as a conductive agent and a binder used for the polarizable electrode layer of the electrochemical capacitor as required.
Examples of the activated carbon material include sawdust, coconut shell, phenol resin, various heat-resistant resins, and pitch. Examples of the heat resistant resin include polyimide, polyamide, polyamideimide, polyetherimide, polyethersulfone, polyetherketone, bismaleimide triazine, aramid, fluororesin, polyphenylene, polyphenylene sulfide and the like. These can be used alone or in combination of two or more.

  The lithium ion capacitor includes, for example, a positive electrode 10, a negative electrode 20, a power storage element B having a separator 30 between the positive electrode 10 and the negative electrode 20, a nonaqueous electrolytic solution in which an electrolyte is dissolved in a nonaqueous solvent, and a laminate film. (See FIG. 3). Further, the lithium ion capacitor has a terminal 50 having one end connected to the electricity storage element B and the other end derived from the film package 40 (with the electricity storage element B and the non-aqueous electrolyte sealed). For example, a polarizable electrode layer 12 is formed on the surface of the current collector 11 of the positive electrode 10 made of an aluminum metal foil via a conductive adhesive (not shown). As the polarizable electrode layer 12, one having the same material and structure as those used in the electrochemical capacitor can be used. Moreover, what has the well-known material and structure used with the polarizable electrode layer of the positive electrode of a lithium ion capacitor can be used. In addition, an active material layer 23 is formed on the surface of the negative electrode current collector 21 made of, for example, a copper metal foil. For example, the positive electrode 10 and the negative electrode 20 are disposed so that the polarizable electrode layer 12 of the positive electrode 10 and the active material layer 23 of the negative electrode 20 face each other. A lithium metal sheet is disposed in the vicinity of the negative electrode 20. As a result, lithium in the lithium metal sheet is dissolved in the non-aqueous electrolyte, and the lithium ions are pre-doped in the active material layer of the negative electrode 20, so that the potential of the negative electrode 20 is higher than the potential of the positive electrode 10 before charging. For example, it is about 3V lower. The separator is formed from a material that can be impregnated with a nonaqueous electrolytic solution, such as cellulose, polypropylene, polyethylene, and fluorine resin. The separator 30 is disposed between the polarizable electrode layer 12 of the positive electrode 10 and the active material layer 23 of the negative electrode 20 facing each other. A known structure used in a film package type lithium capacitor can be applied to the storage element B and the film package 40.

  As the negative electrode active material layer 23, a material having a known material and structure used in an active material layer of a lithium ion capacitor can be used. For example, active materials such as non-graphitizable carbon, graphite, tin oxide, and silicon oxide can be used. Containing substances, conductive assistants such as carbon black and metal powder, and binders such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and styrene butadiene rubber (SBR) may be included as required. Good.

Example 1
In 1 liter of a non-aqueous solvent composed of propylene carbonate (PC), 1.5 mol of an electrolyte in which the anion component is a boron-containing anion of formula (1-3) and the cation component is a cation of formula (2-1) A dissolved electrolyte was prepared. A thin electrochemical capacitor was produced by the following method. The electrodes (positive electrode 10 and negative electrode 20) using PAS as the polarizable electrode material and the separator made of cellulose were cut and then alternately laminated, and the lead terminals were attached by ultrasonic welding (FIG. 1). The prepared device is vacuum-dried at about 180 ° C., then the device is put into a sealing material cut into an electrode size, an electrolyte is injected, and the sealing material is heat-sealed using a sealing material, about 20 mm × 26 mm. A cell of the size was prepared. As a sealing material, a laminate film of nylon / aluminum / CPP (unstretched polypropylene) was used.

(Example 2)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the anion component of the electrolyte was changed to the boron-containing anion of formula (1-6).

(Example 3)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the anion component of the electrolyte was changed to the boron-containing anion of formula (1-7).

Example 4
An electric double layer capacitor was produced in the same manner as in Example 1 except that the anion component of the electrolyte was changed to the boron-containing anion of formula (1-8).

(Example 5)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the cation component of the electrolyte was changed to the cation of formula (2-2).

(Example 6)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the cation component of the electrolyte was changed to the cation of formula (3-1).

(Example 7)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the cation component of the electrolyte was changed to the cation of formula (4-1).

(Example 8)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the nonaqueous solvent was changed to γ-butyrolactone (GBL).

Example 9
An electric double layer capacitor was produced in the same manner as in Example 1 except that the nonaqueous solvent was changed to δ-valerolactone (DVL).

(Example 10)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the non-aqueous solvent was changed to sulfolane (SL).

(Example 11)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the nonaqueous solvent was changed to ethylpropylsulfone (EPS).

(Example 12)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the non-aqueous solvent was changed to a mixed solvent composed of 80% by weight of sulfolane (SL) and 20% by weight of ethyl methyl sulfone (EMS).

(Example 13)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the non-aqueous solvent was changed to a mixed solvent composed of 50% by weight of γ-butyrolactone (GBL) and 50% by weight of ethylpropylsulfone (EPS).

(Example 14)
An electric double layer capacitor was produced in the same manner as in Example 11 except that the cation component of the electrolyte was changed to Me ₄ N ⁺ .

(Comparative Example 1)
An electric double layer capacitor was produced in the same manner as in Example 1 except that the anion component of the electrolyte was changed to tetrafluoroborate (BF ₄ ⁻ ).

(Comparative Example 2)
An electric double layer capacitor was produced in the same manner as in Comparative Example 1 except that the non-aqueous solvent was changed to γ-butyrolactone (GBL).

(Comparative Example 3)
An electric double layer capacitor was produced in the same manner as in Comparative Example 1 except that the non-aqueous solvent was changed to δ-valerolactone (DVL).

(Comparative Example 4)
An electric double layer capacitor was produced in the same manner as in Comparative Example 1 except that the non-aqueous solvent was changed to sulfolane (SL).

(Comparative Example 5)
An electric double layer capacitor was produced in the same manner as in Comparative Example 1 except that the nonaqueous solvent was changed to ethylpropylsulfone (EPS).

(Comparative Example 6)
An electric double layer capacitor was produced in the same manner as in Comparative Example 1 except that the non-aqueous solvent was changed to a mixed solvent composed of 80% by weight of sulfolane (SL) and 20% by weight of ethyl methyl sulfone (EMS).

(Comparative Example 7)
An electric double layer capacitor was produced in the same manner as in Comparative Example 1 except that the non-aqueous solvent was changed to a mixed solvent composed of 50% by weight of γ-butyrolactone (GBL) and 50% by weight of ethylpropylsulfone (EPS).

(Comparative Example 8)
An electric double layer capacitor was produced in the same manner as in Comparative Example 5 except that the electrolyte was an electrolyte having an anion component of B (CF ₃ ) ₄ ⁻ ) and a cation component of Me ₄ N ⁺ .

(Reliability test)
The electrochemical capacitors prepared in Examples 1 to 14 and Comparative Examples 1 to 7 were each left in a 25 ° C. atmosphere for 12 hours, and then measured for capacitance and DC resistance in the same atmosphere to obtain these initial values. It was. In addition, the electrostatic capacity was obtained by using a charge / discharge tester (TOSCAT-3200 manufactured by Toyo System Co., Ltd.) and charging a cell discharged for 30 minutes at room temperature to 2.5 V at 100 mA for 10 minutes and then discharging to 0 V at 10 mA. It was calculated from the slope of the discharge curve. DC resistance is a voltage drop when a charge / discharge tester (TOSCAT-3200 manufactured by Toyo System Co., Ltd.) is used and a cell discharged at room temperature for 30 minutes is charged at 100 mA to 2.5 V for 10 minutes and then discharged at 2 A to 0 V. Calculated from
In addition, a process of putting in a reflow furnace having a temperature profile from 150 ° C. to 250 ° C. over 5 minutes for 5 minutes is repeated 5 times, and a voltage of 2.5 V is continuously applied for 1000 hours in an atmosphere of 60 ° C., and then 25 Capacitance and DC resistance were measured in an atmosphere at 0 ° C. The measurement results were divided by the initial measurement results of capacitance and DC resistance, and the capacitance change rate and DC resistance change rate were expressed as percentages (after reflow + float test). The results are summarized in Tables 1 and 2 below.

Comparison between Examples 1 to 7 and Comparative Example 1, Comparison between Example 8 and Comparative Example 2, Comparison between Example 9 and Comparative Example 3, Comparison between Example 10 and Comparative Example 4, Example 11 and From the comparison with Comparative Example 5, the comparison between Example 129 and Comparative Example 6, and the comparison between Example 13 and Comparative Example 7, the boron-containing anion represented by the general formula (1) is used as the anion component of the electrolyte. In some cases, it was found that the rate of decrease in capacitance and the rate of increase in DC resistance after the reflow + float test were smaller than when tetrafluoroborate was used as the anion component of the electrolyte. Thus, in the electrochemical device of this invention, the characteristic deterioration after reflow is suppressed.
The reason why this effect is obtained is not clear, but when tetrafluoroborate is used as the electrolyte anion component, the tetrafluoroborate anion reacts with moisture in the non-aqueous electrolyte under high heat of reflow to produce hydrogen fluoride, The generated hydrogen fluoride causes corrosion of the current collector metal and decomposition of non-aqueous solvents such as propylene carbonate. Therefore, the rate of decrease in capacitance and the rate of increase in DC resistance after the reflow + float test are large. Presumed. On the other hand, in Experimental Examples 1 to 13, since hydrogen fluoride is not generated from the anion component in the electrolyte, corrosion of the current collector metal by hydrogen fluoride and decomposition of a non-aqueous solvent such as propylene carbonate are prevented, and reflow + float It is estimated that the rate of decrease in capacitance and the rate of increase in DC resistance after the test are small.
Further, when the initial capacitance values of Example 14 and Comparative Example 8 are compared, Example 14 is larger than Comparative Example 8. This is presumably because the anion used in Example 14 is asymmetric, and therefore the solubility of the electrolyte in the solvent is higher than that of the anion used in Comparative Example 8 which is symmetrical.
In this embodiment, a film package type electric double layer capacitor in which the storage element B and the non-aqueous electrolyte are enclosed in a film package 40 made of a laminate film is used, but a button type using a metal can or the like is used. It is also possible to include a fluorine-containing anion represented by the general formula (1) as an electrolyte anion component in a nonaqueous electrolytic solution of other types of electric double layer capacitors such as a cylindrical type and a square type. However, it is possible to achieve the same effect as described above.

(Example 15)
An electrolyte solution is prepared by dissolving 1.2 mol of an electrolyte in which the anion component is a boron-containing anion of formula (1-3) and the cation component is lithium ion in 1 liter of a non-aqueous solvent made of propylene carbonate (PC). did. Moreover, the lithium ion capacitor was produced by the following method. A positive electrode 10 using PAS as a polarizable electrode material, a negative electrode 20 using a non-graphitizable carbon made of a phenol resin material, and a separator made of cellulose are cut and laminated alternately, and the lead terminals are ultrasonically welded. (Fig. 3). The prepared device is vacuum-dried at about 180 ° C., then a lithium foil is applied to the negative electrode, the device is put into a sealing material cut to an electrode size, an electrolytic solution is injected, and the sealing material is thermally melted using a sealing material. A cell having a size of about 20 mm × 26 mm was prepared. As a sealing material, a laminate film of nylon / aluminum / CPP (unstretched polypropylene) was used.

(Example 16)
A lithium ion capacitor was produced in the same manner as in Example 15 except that the anion component of the electrolyte was changed to the boron-containing anion of formula (1-6).

(Example 17)
A lithium ion capacitor was produced in the same manner as in Example 15 except that the anion component of the electrolyte was changed to the boron-containing anion of formula (1-7).

(Example 18)
A lithium ion capacitor was produced in the same manner as in Example 15 except that the anion component of the electrolyte was changed to the boron-containing anion of formula (1-8).

(Example 19)
A lithium ion capacitor was produced in the same manner as in Example 15 except that the non-aqueous solvent was changed to a mixed solvent having a mixing ratio of propylene carbonate (PC) and ethyl methyl carbonate (EMC) of 2: 1.

(Example 20)
The same method as in Example 15 except that the non-aqueous solvent was changed to a mixed solvent in which the mixing ratio of propylene carbonate (PC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) was a ratio of 3: 1: 4. A lithium ion capacitor was produced.

(Example 21)
The same method as in Example 15 except that the nonaqueous solvent was changed to a mixed solvent in which the mixing ratio of propylene carbonate (PC), ethylene carbonate (EC) and γ-butyrolactone (GBL) was a ratio of 3: 1: 2. A lithium ion capacitor was produced.

(Comparative Example 9)
A lithium ion capacitor was produced in the same manner as in Example 15 except that the anion component of the electrolyte was changed to hexafluorophosphate (PF ₆ ⁻ ).

(Comparative Example 10)
A lithium ion capacitor was produced in the same manner as in Comparative Example 9, except that the non-aqueous solvent was changed to a mixed solvent in which the mixing ratio of propylene carbonate (PC) and ethyl methyl carbonate (EMC) was 2: 1.

(Comparative Example 11)
The same method as in Comparative Example 9 except that the non-aqueous solvent was changed to a mixed solvent in which the mixing ratio of propylene carbonate (PC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) was a ratio of 3: 1: 4. A lithium ion capacitor was produced.

(Comparative Example 12)
The same method as in Comparative Example 9 except that the non-aqueous solvent was changed to a mixed solvent in which the mixing ratio of propylene carbonate (PC), ethylene carbonate (EC), and γ-butyrolactone (GBL) was a ratio of 3: 1: 2. A lithium ion capacitor was produced.

(Reliability test)
The lithium ion capacitors produced in Examples 15 to 21 and Comparative Examples 9 to 12 were each left in a 25 ° C. atmosphere for 12 hours, and then the capacitance, DC resistance, and capacitor container thickness (T1) were measured in the same atmosphere. These initial values were obtained. In addition, the electrostatic capacity was obtained by using a charge / discharge tester (TOSCAT-3200 manufactured by Toyo System Co., Ltd.) and charging a cell discharged for 30 minutes at room temperature to 2.5 V at 100 mA for 10 minutes and then discharging to 0 V at 10 mA. It was calculated from the slope of the discharge curve. DC resistance is a voltage drop when a charge / discharge tester (TOSCAT-3200 manufactured by Toyo System Co., Ltd.) is used and a cell discharged at room temperature for 30 minutes is charged at 100 mA to 2.5 V for 10 minutes and then discharged at 2 A to 0 V. Calculated from The thickness of the capacitor container (film package 40) was measured with a caliper.
Further, a voltage of 3.8 V was continuously applied for 1000 hours in an atmosphere of 80 ° C., and thereafter, the capacitance, the DC resistance, and the thickness (T2) of the capacitor container (film package 40) were measured in an atmosphere of 25 ° C. The measurement results were divided by the initial measurement results of capacitance, DC resistance, and capacitor container thickness (T1), and the capacitance change rate, DC resistance change rate, and capacitor vessel thickness change rate were expressed as percentages ( After reliability test). The results are summarized in Table 3 below.

  From the comparison between Examples 15 to 21 and Comparative Examples 9 to 12, when the boron-containing anion represented by the general formula (1) is used as the anion component of the electrolyte, hexafluorophosphate is used as the anion component of the electrolyte. It was found that the rate of decrease in capacitance, the rate of increase in direct current resistance, and the rate of increase in capacitor container thickness after the reliability test were smaller than those in FIG. Thus, in the electrochemical device of the present invention, high temperature stability is improved.

Claims (4)

An electrochemical device using an electrolytic solution containing a nonaqueous solvent and an electrolyte, wherein the anion component of the electrolyte is a boron-containing anion represented by the following general formula (1).
^{_{B - (CN) n R 4}} -n (1)
(In the formula, R independently represents a perfluoroalkyl group having 1 to 4 carbon atoms, n represents an integer of 1 to 3, and when n is 1 or 2, two R's are bonded to each other. To form a ring.) The electrochemical device according to claim 1, wherein the cation component of the electrolyte is a cation of the following general formulas (2) to (4).

(2)
(Wherein R _{1 to} R ₄ each represent a monovalent saturated hydrocarbon group having 1 to 6 carbon atoms or a monovalent heteroatom-containing saturated hydrocarbon group.)

(3)
(In the formula, R ₅ and R ₆ each represent a monovalent saturated hydrocarbon group having 1 to 6 carbon atoms or a monovalent heteroatom-containing saturated hydrocarbon group, and X represents a divalent saturated hydrocarbon group or a divalent saturated hydrocarbon group. A valent heteroatom-containing saturated hydrocarbon group that forms a heterocycle with the nitrogen atom to which it is attached.

(4)
(In the formula, X is a divalent saturated hydrocarbon group or a divalent heteroatom-containing saturated hydrocarbon group, which forms a heterocycle together with the nitrogen atom bonded thereto, and Y is a divalent saturated hydrocarbon group. Or a divalent heteroatom-containing saturated hydrocarbon group that forms a heterocycle with the nitrogen atom to which it is attached.)   The electrochemical device according to claim 1, wherein the cation component of the electrolyte is an alkali metal ion.   Non-aqueous solvent is ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, 3-methyl-γ-butyrolactone, 2-methyl-γ-butyrolactone, δ-valerolactone, glutaronitrile The electrochemical device according to any one of claims 1 to 3, which is selected from the group consisting of adiponitrile, sulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, and ethylpropylsulfone.

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