JP2009016441A - Nonaqueous electrolyte for electrochemical capacitor, and electrochemical capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical capacitor having high withstand voltage, that is, high energy density. <P>SOLUTION: The electrochemical capacitor includes an electrode element comprising a separator, and a pair of electrodes arranged oppositely to each other through the separator. The nonaqueous electrolyte is contained in the electrode element of the electrochemical capacitor. The nonaqueous electrolyte is characterized by containing 10 wt.% or more of 4-fluoro-1, 3-dioxolan-2-on. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrochemical capacitor, and more particularly to an electrochemical capacitor using a non-aqueous electrolyte.

  An electrochemical capacitor is an electricity storage device based on the accumulation of electric charge by electrostatic capacity, compared to a battery that stores electric power by a reaction involving electrochemical oxidation-reduction, and in recent years it behaves more like a capacitor than a battery. It often includes a power storage mechanism with a fast redox reaction.

  Compared with power storage devices that are classified as batteries, electrochemical capacitors have a lower energy density, but they can be charged and discharged at high speed. In recent years, studies have been actively made to improve the energy density while taking advantage of the feature that high-speed charging / discharging is possible, and its applications are expanding.

  An electrochemical capacitor usually includes a pair of electrodes and an electrolyte. When the electrode is a polarizable electrode, it becomes an electric double layer capacitor that stores electricity in the electric double layer generated at the interface with the electrolyte. In addition, there is a pseudocapacitor (redox capacitor) using a pseudocapacitance due to oxidation and reduction of a non-polarizable electrode together with an electric double layer capacitance (Non-patent Document 1). Furthermore, in recent years, for example, an electrode of a secondary battery such as a lithium secondary battery is used as one electrode, an electrode of an electrochemical capacitor is used as the other electrode, one electrode is a secondary battery, and one electrode is an electric battery. Hybrid capacitors that operate as chemical capacitors have also been studied.

  For the polarizable electrode of an electric double layer capacitor, a molded body or a coating film of activated carbon fiber or activated carbon particles is generally used. For example, it is formed by press molding activated carbon fibers or activated carbon particles, or by applying a kneaded material with a suitable binder onto a current collector metal. In addition, the polarizable electrode may be formed by plasma spraying aluminum on activated carbon fiber.

  On the other hand, a non-polarizable electrode of a pseudocapacitor uses a metal oxide such as ruthenium oxide, iridium oxide, nickel oxide or lead oxide, or a conductive polymer such as polypyrrole or polythiophene. In addition to using electrodes prepared by the method, individual electrode preparation methods adapted to the characteristics of each material are also used.

  The hybrid capacitor uses these electrodes on one side and the electrodes of the secondary battery on the other side.

The electrolyte used in the electrochemical capacitor includes an aqueous electrolyte such as an aqueous solution of sulfuric acid or potassium hydroxide, a non-aqueous electrolyte obtained by dissolving a quaternary ammonium salt or quaternary phosphonium salt in an organic solvent such as propylene carbonate, There are solid electrolytes such as ethylene oxide-alkali metal salt complexes and RbAg ₄ I ₅ (Non-patent Document 2).

  Electrochemical capacitors that use non-aqueous electrolytes have the advantage of higher energy density than electrochemical capacitors that use aqueous electrolytes because they can increase the withstand voltage, and backup power supplies for consumer electronic devices that require miniaturization. In addition to being used for driving power sources for mobile devices and the like, development aimed at use in power applications such as electric vehicles, hybrid vehicles, and power storage has been carried out using non-aqueous electrolytes.

The energy W stored in the electrochemical capacitor is expressed by the following equation when discharging from a voltage Vi to Vf with a constant current I.
W = 1/2 · C (Vi ² −Vf ² )
(In the above formula, C represents capacitance (F).)

  From the above formula, it is desirable to increase C and Vi in order to further increase the energy density. Electrochemically, Vi is the difference between the positive electrode potential and the negative electrode potential, and it is desirable to make the oxidation resistance potential more noble and the reduction resistance potential lower. These oxidation resistance / reduction resistance can be improved by using a more noble or base electrolyte having a decomposition potential.

  C is determined by the area of the electrode surface area. Therefore, an electrode having a large surface area per unit volume such as activated carbon is used as the electrode (Non-patent Document 3). However, if the surface area is too large to have a structure with pores that are too fine on the surface, solvated ions cannot enter the pores and cannot contact the electrode surface, so the capacitance of the capacitor may decrease. Therefore, it is desirable that the solvated ion has a smaller radius.

  By the way, since the electronegativity of a fluorine atom is large, it is generally reported that the oxidation resistance potential of an electrolytic solution can be improved by introducing a fluorine atom into a compound used as a solvent (Non- Patent Document 4). Specifically, by using a compound having two or more fluorine atoms in a cyclic carbonate solvent, an electric double layer capacitor or a hybrid capacitor using activated carbon as a positive electrode and a graphite negative electrode for a lithium secondary battery as a negative electrode. It has been reported that the characteristics can be improved (Patent Document 1).

  In addition, the fluorine atom has an advantage that the van der Waals radius is small and the molecular size hardly changes even when the hydrogen atom is substituted. Furthermore, it is known that the surface tension generally decreases by replacing hydrogen atoms with fluorine atoms, and the possibility of a decrease in the surface directivity of the electrolyte with respect to the electrode can also be expected (Non-patent Document 4). ).

  However, there is a concern that the reduction resistance may be lowered by introducing fluorine atoms, and attention must be paid to the number of introduced fluorine atoms.

  On the other hand, it is known that the characteristics of hybrid capacitors are improved by adding a small amount of monofluoroethylene carbonate, which uses a negative electrode for a lithium secondary battery, and monofluoroethylene carbonate is a negative electrode coating. It is only used as a forming additive (Patent Document 2).

  In addition, a lithium secondary battery or an electric double layer capacitor using fluoroethylene carbonate in combination with a gel electrolyte has been reported, but this is also used as an additive for forming a negative electrode film in a lithium secondary battery. Only experimental examples have been described in which characteristics are improved when used in small amounts (Patent Documents 3 and 4).

B. E. Conway, J. et al. Electrochem. Soc. , 138, 1539 (1991) Ue Makoto, Electrochemistry, 66, 904, 1998 Functional chemistry series of electrons and ions, Volume 2, Frontiers of large-capacity electric double layer capacitors, 16 pages, 2002, NTS Introduction to Fluorochemistry, 6, 306, 1997, Nikkan Kogyo Shimbun Japanese Patent No. 3541476 JP 2006-286926 A International Publication No. 2002/093678 Pamphlet International Publication No. 2002/093679 Pamphlet

  The present invention has been made in view of the above problems, and an object thereof is to provide an electrochemical capacitor having a high energy density.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors include a compound in which one fluorine atom is introduced into 1,3-dioxolan-2-one in a non-aqueous electrolyte solution of 10% by weight or more. It has been found that an electrochemical capacitor having a high withstand voltage, that is, a high energy density can be realized as a result of reducing the reduction resistance within an allowable range while improving the oxidation resistance and further improving the capacitance. Completed the invention.

  That is, the gist of the present invention is a non-aqueous electrolyte solution contained in the electrode element of an electrochemical capacitor, which includes an electrode element composed of a separator and a pair of electrodes opposed to each other with the separator interposed therebetween, The non-aqueous electrolyte contains 10% by weight or more of 4-fluoro-1,3-dioxolan-2-one, and exists in a non-aqueous electrolyte for electrochemical capacitors (Claim 1).

  The nonaqueous electrolytic solution preferably contains one or more electrolytes selected from the group consisting of organic onium salts and alkali metal salts (Claim 2).

  Further, the organic onium salt is preferably a quaternary ammonium salt and / or a quaternary phosphonium salt.

  The alkali metal salt is preferably a lithium salt.

The non-aqueous electrolyte solution is bonded with an organic onium cation and one or more anions selected from the group consisting of BF ₄ anion, PF ₆ anion, bis (oxalato) borate anion, and difluorooxalatoborate anion. It is preferable to contain one or more compounds (claim 5).

  Furthermore, the organic onium cation is preferably a tetraalkylammonium cation.

  Another gist of the present invention resides in an electrochemical capacitor having the non-aqueous electrolyte.

  At this time, it is preferable to provide a polarizable electrode containing activated carbon (claim 8).

  According to the present invention, an electrochemical capacitor having a high energy density can be provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description described below is an example of embodiments of the present invention, and the present invention is limited to these contents without departing from the gist thereof. is not.

[I. Overview of electrochemical capacitors]
The electrochemical capacitor of the present invention comprises at least a non-aqueous electrolyte for an electrochemical capacitor of the present invention (hereinafter referred to as “the non-aqueous electrolyte of the present invention” as appropriate) and a pair of electrodes. To do. The electrochemical capacitor of the present invention usually includes a separator. When the electrochemical capacitor of the present invention includes a separator, a pair of the electrodes are disposed to face each other via the separator, and an electrode element is configured by the separator and the electrode. Furthermore, when the electrode and the separator have a structure that can be impregnated with the non-aqueous electrolyte solution, the non-aqueous electrolyte solution is preferably held in a state of being impregnated in the electrode element. The electrochemical capacitor of the present invention may include other members as long as the effects of the present invention are not significantly impaired. Moreover, it is preferable that all the constituent materials are housed in a sealed exterior body.

[II. Non-aqueous electrolyte]
[II-1. Overview]
The non-aqueous electrolyte solution of the present invention is a non-aqueous electrolyte solution that includes an electrode element composed of a separator and a pair of electrodes opposed to each other via the separator, and is contained in the electrode element of an electrochemical capacitor. The non-aqueous electrolyte solution for electrochemical capacitors is characterized in that it contains 10% by weight or more of 4-fluoro-1,3-dioxolan-2-one.

  The non-aqueous electrolyte of the present invention usually comprises at least one non-aqueous solvent and at least one electrolyte dissolved therein as the main components. The non-aqueous electrolyte of the present invention does not impair the effect obtained by containing 10% by weight or more of 4-fluoro-1,3-dioxolan-2-one, 4-fluoro-1,3-dioxolane-2 -Can be used in combination with any non-aqueous solvent other than ON. In addition, a non-aqueous solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations. In addition, the nonaqueous electrolytic solution of the present invention may optionally contain other substances such as additives as long as the effects of the present invention are not significantly impaired.

[II-2. Nonaqueous solvent]
The non-aqueous solvent for dissolving the electrolyte is not particularly limited as long as the effect of the present invention is not significantly impaired.
Cyclic carbonate chain carbonate ester,
Cyclic carboxylic acid ester,
Chain carboxylic acid ester,
Phosphorus-containing organic solvent,
Sulfur-containing organic solvents,
Etc.

The type of the cyclic carbonate is not particularly limited as long as the effect of the present invention is not significantly impaired, but as a specific example of what is usually used,
Ethylene carbonate,
Propylene carbonate,
Butylene carbonate,
Etc.
Among these, ethylene carbonate and / or propylene carbonate have a high dielectric constant, so that the solute is easily dissolved, and various characteristics of the capacitor used are good when it is used as a component of the non-aqueous electrolyte solution of the electrochemical capacitor. Is preferable. Moreover, cyclic carbonate may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

The type of chain carbonate ester is not particularly limited as long as the effects of the present invention are not significantly impaired.
Dimethyl carbonate,
Ethyl methyl carbonate,
Diethyl carbonate,
Methyl-n-propyl carbonate,
Ethyl-n-propyl carbonate,
Di-n-propyl carbonate,
Etc.
Among these, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are particularly preferable from the balance of dielectric constant and viscosity. Moreover, chain | strand-shaped carbonate ester may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

The type of cyclic carboxylic acid ester is not particularly limited as long as the effects of the present invention are not significantly impaired.
γ-butyrolactone,
γ-valerolactone,
δ-valerolactone,
Etc.
Among these, γ-butyrolactone is preferable from the balance of boiling point, melting point, dielectric constant, and viscosity. Moreover, cyclic carboxylic acid ester may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

Furthermore, the type of chain carboxylic acid ester is not particularly limited as long as it does not significantly impair the effects of the present invention,
Methyl acetate,
Ethyl acetate,
Acetic acid-n-propyl,
Acetic acid-i-propyl,
N-butyl acetate,
I-butyl acetate,
Tert-butyl acetate,
Methyl propionate,
Ethyl propionate,
N-propyl propionate,
Propionate-i-propyl,
Propionate-n-butyl,
Propionate-i-butyl,
Propionate-t-butyl,
Etc.
Among these, ethyl acetate, methyl propionate, and ethyl propionate are preferable from the balance of dielectric constant and viscosity. Moreover, chain | strand-shaped carboxylic acid ester may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

The type of the phosphorus-containing organic solvent is not particularly limited as long as the effects of the present invention are not significantly impaired.
Trimethyl phosphate,
Triethyl phosphate,
Phosphate esters such as triphenyl phosphate;
Trimethyl phosphite,
Triethyl phosphite,
Phosphites such as triphenyl phosphite;
Trimethylphosphine oxide,
Triethylphosphine oxide,
Phosphine oxides such as triphenylphosphine oxide;
Etc.
Among these, trimethyl phosphate and triethyl phosphate are preferable from the balance of oxidation-reduction resistance, dielectric constant, and viscosity. Moreover, a phosphorus-containing organic solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

In addition, the type of the sulfur-containing organic solvent is not particularly limited as long as the effect of the present invention is not significantly impaired,
Ethylene sulfite,
1,3-propane sultone,
1,4-butane sultone,
Methyl methanesulfonate,
Busulfan,
Sulfolane,
Sulfolene,
Dimethyl sulfone,
Etc.
Among these, sulfolane is preferable from the balance of boiling point, melting point, dielectric constant, and viscosity. Moreover, a sulfur-containing organic solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Among the non-aqueous solvents, ethylene carbonate, propylene carbonate, methyl carbonate, ethyl methyl carbonate and / or diethyl carbonate are particularly preferable.

  When two or more kinds of non-aqueous solvents are used, the non-aqueous solvents are not necessarily used after being mixed in advance unless the effects of the present invention are significantly impaired. Also, when mixing the non-aqueous solvent and 4-fluoro-1,3-dioxolan-2-one, the order of mixing is arbitrary as long as the effects of the present invention are not significantly impaired.

  In mixing, the mixing ratio can be arbitrarily determined as long as the effects of the present invention are not significantly impaired. However, the content of 4-fluoro-1,3-dioxolan-2-one is preferably 10% by weight or more, more preferably 30% by weight or more, and particularly preferably 50% by weight or more. If the content is too low, the effect of improving the oxidation resistance and the effect of improving the capacitance of 4-fluoro-1,3-dioxolan-2-one may not be sufficiently exhibited.

[II-3. Electrolytes]
The electrolyte used in the present invention is not particularly limited as long as it is a compound that does not significantly impair the effects of the present invention and acts as an electrolyte. However, since the solubility in an organic solvent, the dissociation property in the organic solvent, and the oxidation-reduction resistance are good, the electrolyte is one or two electrolytes selected from the group consisting of organic onium salts and alkali metal salts. Preferably there is.
Among these, the organic onium salt is preferably a quaternary ammonium salt and / or a quaternary phosphonium salt.
The alkali metal salt is preferably a lithium salt.

[II-3-1. Cation]
The organic onium salt used in the present invention is composed of an arbitrary organic onium cation and an arbitrary anion. Among these, the organic onium cation is preferably a quaternary onium cation.

  Specific examples of the quaternary onium cation include compounds represented by the following general formula (I).

In the general formula (I), R ^{1 to} R ⁴ each independently represents a hydrocarbon group. Unless the effect of this invention is impaired remarkably, the kind of hydrocarbon group is not restrict | limited, but is arbitrary. That is, it may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, or may be a hydrocarbon group to which those groups are bonded. In the case of an aliphatic hydrocarbon group, it may be a chain or a ring, and may have a structure in which a chain and a ring are combined. In the case of a chain hydrocarbon group, it may be linear or branched. Moreover, it may be a saturated hydrocarbon group and may have an unsaturated bond.

The carbon number of the hydrocarbon group of R ^{1 to} R ⁴ is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 or more, usually 20 or less, preferably 10 or less, more preferably 5 or less. . If the amount is too large, the number of moles per weight decreases, and various effects may be reduced. In addition, when the hydrocarbon group of R < ¹ > -R < ⁴ > has a substituent, carbon number of the substituted hydrocarbon group also including those substituent shall satisfy | fill the said range.

Each hydrocarbon group of R ^{1 to} R ⁴ may be substituted with one or more substituents. The kind of the substituent is arbitrary as long as the effects of the present invention are not significantly impaired. Specific examples include a halogen atom, a hydroxyl group, an amino group, a nitro group, a cyano group, a carboxyl group, an alkoxyl group, and an aldehyde group. In the case where the hydrocarbon group of R ¹ to R ⁴ have two or more substituents, these substituents may be mutually the same or may be different.

The hydrocarbon groups of R ^{1 to} R ⁴ may be the same as or different from each other when any two or more hydrocarbon groups are compared. When the hydrocarbon groups of R ^{1 to} R ⁴ have a substituent, the substituted hydrocarbon groups including those substituents may be the same as or different from each other.

Further, any two or more hydrocarbon groups of R ^{1 to} R ⁴ may be bonded to each other to form a cyclic structure.

Specific examples of the hydrocarbon group for R ^{1 to} R ⁴ include an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, and the like.

Specific examples of the alkyl group include
Methyl group,
Ethyl group,
1-propyl group,
1-methylethyl group,
1-butyl group,
1-methylpropyl group,
2-methylpropyl group,
1,1-dimethylethyl group,
Etc.
Among these,
Methyl group,
Ethyl group,
1-propyl group,
1-butyl group,
Is preferable from the viewpoint of ease of production and appropriate molecular weight.

Specific examples of the cycloalkyl group include
A cyclopentyl group,
2-methylcyclopentyl group,
3-methylcyclopentyl group,
2,2-dimethylcyclopentyl group,
2,3-dimethylcyclopentyl group,
2,4-dimethylcyclopentyl group,
2,5-dimethylcyclopentyl group,
3,3-dimethylcyclopentyl group,
3,4-dimethylcyclopentyl group,
2-ethylcyclopentyl group,
3-ethylcyclopentyl group,
A cyclohexyl group,
2-methylcyclohexyl group,
3-methylcyclohexyl group,
4-methylcyclohexyl group,
2,2-dimethylcyclohexyl group,
2,3-dimethylcyclohexyl group,
2,4-dimethylcyclohexyl group,
2,5-dimethylcyclohexyl group,
2,6-dimethylcyclohexyl group,
3,4-dimethylcyclohexyl group,
3,5-dimethylcyclohexyl group,
2-ethylcyclohexyl group,
3-ethylcyclohexyl group,
4-ethylcyclohexyl group,
A bicyclo [3,2,1] oct-1-yl group,
A bicyclo [3,2,1] oct-2-yl group,
Etc.
Among these,
A cyclopentyl group,
2-methylcyclopentyl group,
3-methylcyclopentyl group,
A cyclohexyl group,
2-methylcyclohexyl group,
3-methylcyclohexyl group,
4-methylcyclohexyl group,
Is preferable from the viewpoint of ease of production and appropriate molecular weight.

Specific examples of the aryl group include
Phenyl group,
2-methylphenyl group,
3-methylphenyl group,
4-methylphenyl group,
2,3-dimethylphenyl group,
Etc.
Among these, a phenyl group is preferable from the viewpoint of ease of production and appropriate molecular weight.

Specific examples of aralkyl groups include
Phenylmethyl group,
1-phenylethyl group,
2-phenylethyl group,
Diphenylmethyl group,
Triphenylmethyl group,
Etc.
Among these, a phenylmethyl group and a 2-phenylethyl group are preferable because of ease of production and appropriate molecular weight.

In the general formula (I), Q represents any atom that does not significantly impair the effects of the present invention. However, Q is preferably an atom belonging to Group 15 of the periodic table, and among them, a nitrogen atom or a phosphorus atom is preferable.

From the above, preferred examples of the quaternary onium cation represented by the general formula (I) include an aliphatic chain quaternary cation, an aliphatic cyclic ammonium cation, an aliphatic cyclic phosphonium cation, and a nitrogen-containing heterocyclic aromatic. And cations.

  Of the aliphatic quaternary cations, tetraalkylammonium cations, tetraalkylphosphonium cations, and the like are particularly preferable.

Specific examples of tetraalkylammonium cations include
Tetramethylammonium cation,
Ethyltrimethylammonium cation,
Diethyldimethylammonium cation,
Triethylmethylammonium cation,
Tetraethylammonium cation,
Tetra-n-butylammonium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

Specific examples of tetraalkylphosphonium cations include:
Tetramethylphosphonium cation,
Ethyltrimethylphosphonium cation,
Diethyldimethylphosphonium cation,
Triethylmethylphosphonium cation,
Tetraethylphosphonium cation,
Tetra-n-butylphosphonium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

  Among the aliphatic cyclic ammonium cations, pyrrolidinium cations, morpholinium cations, imidazolinium cations, tetrahydropyrimidinium cations, piperazinium cations, piperidinium cations, and their spirocyclic compound cations are ions. It is preferable from the viewpoint of size and solubility.

As a specific example of the pyrrolidinium cation,
N, N-dimethylpyrrolidinium cation,
N-ethyl-N-methylpyrrolidinium cation,
N, N-diethylpyrrolidinium cation,
Spiro- (N, N ′)-bipyrrolidinium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

As a specific example of the morpholinium cation,
N, N-dimethylmorpholinium cation,
N-ethyl-N-methylmorpholinium cation,
N, N-diethylmorpholinium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

As a specific example of the imidazolinium cation,
N, N′-dimethylimidazolinium cation,
N-ethyl-N′-methylimidazolinium cation,
N, N′-diethylimidazolinium cation,
1,2,3-trimethylimidazolinium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

As a specific example of the tetrahydropyrimidinium cation,
N, N′-dimethyltetrahydropyrimidinium cation,
N-ethyl-N′-methyltetrahydropyrimidinium cation,
N, N′-diethyltetrahydropyrimidinium cation,
1,2,3-trimethyltetrahydropyrimidinium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

Specific examples of piperazinium cations include:
N, N, N ′, N′-tetramethylpiperazinium cation,
N-ethyl-N, N ′, N′-trimethylpiperazinium cation,
N, N-diethyl-N ′, N′-dimethylpiperazinium cation,
N, N, N′-triethyl-N′-methylpiperazinium cation,
N, N, N ′, N′-tetraethylpiperazinium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

Specific examples of piperidinium cations include
N, N-dimethylpiperidinium cation,
N-ethyl-N-methylpiperidinium cation,
N, N-diethylpiperidinium cation,
Piperidine-1-spiro-1′-piperidinium cation spiro- (1,1 ′)-bipiperidinium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

  As the nitrogen-containing heterocyclic aromatic cation, a pyridinium cation, an imidazolium cation and the like are particularly preferable from the viewpoint of ion size and solubility.

Specific examples of pyridinium cations include
An N-methylpyridinium cation,
N-ethylpyridinium cation,
1,2-dimethylpyridinium cation,
1,3-dimethylpyridinium cation,
1,4-dimethylpyridinium cation,
1-ethyl-2-methylpyridinium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

As a specific example of an imidazolium cation,
N, N′-dimethylimidazolium cation,
N-ethyl-N′-methylimidazolium cation,
N, N′-diethylimidazolium cation,
1,2,3-trimethylimidazolium cation,
Etc. are preferable from the viewpoint of ion size and solubility.

  In the nonaqueous electrolytic solution of the present invention, cations constituting the electrolyte can be used in any ratio and combination, but usually one kind is used. However, when it is preferable to use a mixture of two or more cations when a non-aqueous electrolyte is used, two or more cations may be mixed and used in any ratio and combination.

[II-3-2. Anion]
Moreover, the said cation can be combined with arbitrary anions, unless the effect of this invention is impaired remarkably. However, because of its good solubility in organic solvents, dissociation in organic solvents, and redox resistance,
ClO ₄ anion,
AsF ₆ anion,
PF ₆ anion,
BF ₄ anion,
Inorganic anions such as
CF ₃ SO ₃ anion,
N (CF ₃ SO ₂ ) ₂ anion,
N (C ₂ F ₅ SO ₂ ) ₂ anion,
1,3-hexafluoropropane disulfonylimide anion,
1,2-tetrafluoroethanedisulfonylimide anion,
N (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) anion,
C (CF ₃ SO ₂ ) ₃ anion,
PF ₄ (CF ₃ ) ₂ anion,
PF ₄ (C ₂ F ₅ ) ₂ anion,
PF ₄ (CF ₃ SO ₂ ) ₂ anion,
PF ₄ (C ₂ F ₅ SO ₂ ) ₂ anion BF ₂ (CF ₃ ) ₂ anion,
BF ₂ (C ₂ F ₅ ) ₂ anion,
BF ₂ (CF ₃ SO ₂ ) ₂ anion,
BF ₂ (C ₂ F ₅ SO ₂ ) ₂ anion,
Fluorine-containing organic anions such as
Bis (oxalato) borate anion,
Tris (oxalato) phosphate anion,
Difluorooxalatoborate anion;
Dicarboxylic acid complex anions such as are preferred.

Among these, PF ₆ anion, BF ₄ anion, N (CF ₃ SO ₂ ) ₂ anion, N (C ₂ F ₅ SO ₂ ) ₂ anion, 1,2-tetrafluoroethanedisulfonylimide anion, bis (oxalato) A borate anion and a difluorooxalatoborate anion are more preferable, and a PF ₆ anion, a BF ₄ anion, a bis (oxalato) borate anion, and a difluorooxalatoborate anion are particularly preferable from the viewpoints of redox resistance and solubility.

  Moreover, in the non-aqueous electrolyte solution of this invention, the 1 type, or 2 or more types of anion which comprises electrolyte can be used by arbitrary ratios and combinations. However, normally, one type is used from the viewpoint of operating the electrochemical capacitor efficiently.

[II-3-3. Combination of cation and anion]
Any electrolyte can be used as long as the effects of the present invention are not significantly impaired. However, a salt composed of a combination of the preferred cation and the preferred anion is preferred.

Specific examples of preferred combinations include
Tetramethylammonium BF ₄ ,
Ethyltrimethylammonium BF ₄ ,
Diethyldimethylammonium BF ₄ ,
Triethylmethylammonium BF ₄ ,
Tetraethylammonium BF ₄ ,
N, N-dimethylpyrrolidinium BF ₄ ,
N-ethyl-N-methylpyrrolidinium BF ₄ ,
N, N-diethylpyrrolidinium BF ₄ ,
Spiro- (N, N ′)-bipyrrolidinium BF ₄ ,
N, N-dimethylpiperidinium BF ₄ ,
N-ethyl-N-methylpiperidinium BF ₄ ,
N, N-diethylpiperidinium BF ₄ ,
N, N′-dimethylimidazolinium BF ₄ ,
N-ethyl-N′-methylimidazolinium BF ₄ ,
N, N′-diethylimidazolinium BF ₄ ,
1,2,3-trimethylimidazolinium BF ₄ ,
N, N′-dimethyltetrahydropyrimidinium BF ₄ ,
N-ethyl-N′-methyltetrahydropyrimidinium BF ₄ ,
N, N′-diethyltetrahydropyrimidinium BF ₄ ,
1,2,3-trimethyltetrahydropyrimidinium BF ₄ ,
N-methylpyridinium BF ₄ ,
N-ethylpyridinium BF ₄ ,
1,2-dimethylpyridinium BF ₄ ,
1,3-dimethylpyridinium BF ₄ ,
1,4-dimethylpyridinium BF ₄ ,
1-ethyl-2-methylpyridinium BF ₄ ,
N, N′-dimethylimidazolium BF ₄ ,
N-ethyl-N′-methylimidazolium BF ₄ ,
N, N′-diethylimidazolium BF ₄ ,
1,2,3-trimethylimidazolium BF ₄ ,
Tetramethylammonium PF ₆ ,
Ethyltrimethylammonium PF ₆ ,
Diethyldimethylammonium PF ₆ ,
Triethylmethylammonium PF ₆ ,
Tetraethylammonium PF ₆ ,
N, N-dimethylpyrrolidinium PF ₆ ,
N-ethyl-N-methylpyrrolidinium PF ₆ ,
N, N-diethylpyrrolidinium PF ₆ ,
Spiro- (N, N ′)-bipyrrolidinium PF ₆ ,
N, N-dimethylpiperidinium PF ₆ ,
N-ethyl-N-methylpiperidinium PF ₆ ,
N, N-diethylpiperidinium PF ₆ ,
N, N′-dimethylimidazolinium PF ₆ ,
N-ethyl-N′-methylimidazolinium PF ₆ ,
N, N′-diethylimidazolinium PF ₆ ,
1,2,3-trimethylimidazolinium PF ₆ ,
N, N′-dimethyltetrahydropyrimidinium PF ₆ ,
N-ethyl-N′-methyltetrahydropyrimidinium PF ₆ ,
N, N′-diethyltetrahydropyrimidinium PF ₆ ,
1,2,3-trimethyltetrahydropyrimidinium PF ₆ ,
N-methylpyridinium PF ₆ ,
N- ethyl-pyridinium PF _6,
1,2-dimethylpyridinium PF ₆ ,
1,3-dimethylpyridinium PF ₆ ,
1,4-dimethylpyridinium PF ₆ ,
1-ethyl-2-methylpyridinium PF ₆ ,
N, N′-dimethylimidazolium PF ₆ ,
N-ethyl-N′-methylimidazolium PF ₆ ,
N, N′-diethylimidazolium PF ₆ ,
1,2,3-trimethylimidazolium PF ₆ ,
Tetramethylammonium bis (oxalato) borate,
Ethyltrimethylammonium bis (oxalato) borate,
Diethyldimethylammonium bis (oxalato) borate,
Triethylmethylammonium bis (oxalato) borate,
Tetraethylammonium bis (oxalato) borate,
N, N-dimethylpyrrolidinium bis (oxalato) borate,
N-ethyl-N-methylpyrrolidinium bis (oxalato) borate,
N, N-diethylpyrrolidinium bis (oxalato) borate,
Spiro- (N, N ′)-bipyrrolidinium bis (oxalato) borate,
N, N-dimethylpiperidinium bis (oxalato) borate,
N-ethyl-N-methylpiperidinium bis (oxalato) borate,
N, N-diethylpiperidinium bis (oxalato) borate,
N, N′-dimethylimidazolinium bis (oxalato) borate,
N-ethyl-N′-methylimidazolinium bis (oxalato) borate,
N, N′-diethylimidazolinium bis (oxalato) borate,
1,2,3-trimethylimidazolinium bis (oxalato) borate,
N, N′-dimethyltetrahydropyrimidinium bis (oxalato) borate,
N-ethyl-N′-methyltetrahydropyrimidinium bis (oxalato) borate,
N, N′-diethyltetrahydropyrimidinium bis (oxalato) borate,
1,2,3-trimethyltetrahydropyrimidinium bis (oxalato) borate,
N-methylpyridinium bis (oxalato) borate,
N-ethylpyridinium bis (oxalato) borate,
1,2-dimethylpyridinium bis (oxalato) borate,
1,3-dimethylpyridinium bis (oxalato) borate,
1,4-dimethylpyridinium bis (oxalato) borate,
1-ethyl-2-methylpyridinium bis (oxalato) borate,
N, N′-dimethylimidazolium bis (oxalato) borate,
N-ethyl-N′-methylimidazolium bis (oxalato) borate,
N, N′-diethylimidazolium bis (oxalato) borate,
1,2,3-trimethylimidazolium bis (oxalato) borate,
Tetramethylammonium difluorooxalatoborate,
Ethyltrimethylammonium difluorooxalatoborate,
Diethyldimethylammonium difluorooxalatoborate,
Triethylmethylammonium difluorooxalatoborate,
Tetraethylammonium difluorooxalatoborate,
N, N-dimethylpyrrolidinium difluorooxalatoborate,
N-ethyl-N-methylpyrrolidinium difluorooxalatoborate,
N, N-diethylpyrrolidinium difluorooxalatoborate,
Spiro- (N, N ′)-bipyrrolidinium difluorooxalatoborate,
N, N-dimethylpiperidinium difluorooxalatoborate,
N-ethyl-N-methylpiperidinium difluorooxalatoborate,
N, N-diethylpiperidinium difluorooxalatoborate,
N, N′-dimethylimidazolinium difluorooxalatoborate,
N-ethyl-N′-methylimidazolinium difluorooxalatoborate,
N, N′-diethylimidazolinium difluorooxalatoborate,
1,2,3-trimethylimidazolinium difluorooxalatoborate,
N, N′-dimethyltetrahydropyrimidinium difluorooxalatoborate,
N-ethyl-N′-methyltetrahydropyrimidinium difluorooxalatoborate,
N, N′-diethyltetrahydropyrimidinium difluorooxalatoborate,
1,2,3-trimethyltetrahydropyrimidinium difluorooxalatoborate,
N-methylpyridinium difluorooxalatoborate,
N-ethylpyridinium difluorooxalatoborate,
1,2-dimethylpyridinium difluorooxalatoborate,
1,3-dimethylpyridinium difluorooxalatoborate,
1,4-dimethylpyridinium difluorooxalatoborate,
1-ethyl-2-methylpyridinium difluorooxalatoborate,
N, N′-dimethylimidazolium difluorooxalatoborate,
N-ethyl-N′-methylimidazolium difluorooxalatoborate,
N, N′-diethylimidazolium difluorooxalatoborate,
1,2,3-trimethylimidazolium difluorooxalatoborate,
LiBF ₄ ,
LiPF ₆ ,
Lithium bis (oxalato) borate,
Lithium difluorooxalatoborate,
Etc.

Among these, it is a compound comprising an organic onium cation and one or more anions selected from the group consisting of BF ₄ anion, PF ₆ anion, bis (oxalato) borate anion and difluorooxalatoborate anion. Is more preferable.

  The organic onium cation is preferably a tetraalkylammonium cation.

  In the nonaqueous electrolytic solution of the present invention, the electrolyte may be used alone or in combination of two or more in any ratio and combination.

  Moreover, there is no restriction | limiting in the molecular weight of electrolyte, Although it is arbitrary unless the effect of this invention is impaired remarkably, it is 150 or more normally. Moreover, although there is no restriction | limiting in particular in an upper limit, In view of the reactivity of this reaction, 1000 or less normally, Preferably 500 or less is practical and preferable.

  Moreover, there is no restriction | limiting in particular also in the manufacturing method of electrolyte, It is possible to select and manufacture a well-known method arbitrarily.

The concentration of the electrolyte in the nonaqueous electrolytic solution is preferably 0.01 mol · dm ⁻³ or more, more preferably 0.1 mol · dm ⁻³ or more, and particularly preferably 0.5 mol · dm ⁻³ or more. The upper limit thereof is preferably 10 mol · dm ⁻³ or less, more preferably 5 mol · dm ⁻³ or less, and particularly preferably 3 mol · dm ⁻³ or less. When the concentration is too low, the resistance of the electrolytic solution increases, and there is a possibility that the amount of ions sufficient for the operation of the electrochemical capacitor is insufficient. On the other hand, if the concentration is too high, the viscosity increases and precipitation may easily occur.

[II-4. Other electrolyte materials]
The nonaqueous electrolytic solution of the present invention may contain an electrolytic solution material other than the nonaqueous solvent and the electrolyte as long as the effects of the present invention are not significantly impaired. For example, when preparing a non-aqueous electrolyte solution using an electrolyte solution material other than these non-aqueous solvent and electrolyte, a conventionally known material can be arbitrarily used as the electrolyte material. In addition, only 1 type may be used for electrolyte solution materials other than these nonaqueous solvents and electrolytes, and 2 or more types may be used together by arbitrary ratios and combinations.

[III. electrode]
The electrode used for the electrochemical capacitor of the present invention is not particularly limited as long as it does not significantly impair the effects of the present invention and operates as an electrochemical capacitor. However, examples of the non-aqueous electrolyte include an electric double layer capacitor and a hybrid capacitor of an electric double layer capacitor and a secondary battery.

[III-1. Electrode material]
Generally, any electrode can be used for the polarizable electrode of the electric double layer capacitor as long as the effects of the present invention are not significantly impaired. However, it is preferable to use carbon in that it is inert to the electrolytic solution and has an appropriate electrical conductivity. Among them, it is preferable to use activated carbon and / or activated carbon fibers such as carbon nanotubes having a large electrode interface for accumulating charges, porous diamond produced by physical vapor deposition (PVD) method, and the like. In addition, the said material may use only 1 type and may use 2 or more types together by arbitrary ratios and combinations.

Any activated carbon can be used as long as the effects of the present invention are not significantly impaired. However, it is preferable that the specific surface area per volume is large because the capacitance is large, and the specific surface area measured by the BET method by nitrogen adsorption is usually 500 m ² / g or more, preferably 1000 m ² / g or more. . Moreover, as the upper limit, it is 2500 m < ² > / g or less normally, Preferably it is 2000 m < ² > / g or less.

  There is no restriction | limiting in the manufacturing method of the said electrode material. For example, activated carbon spun wood, sawdust, coconut husk, pulp waste liquor, coal, petroleum heavy oil, or coal and / or petroleum-based pitch, petroleum coke, carbon aerogel, tarpitch pyrolyzed from them. A wide variety of raw materials such as fiber, synthetic polymer, phenol resin, furan resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyimide resin, polyamide resin, polyacene, ion exchange resin, liquid crystal polymer, plastic waste, waste tire, etc. After carbonization, it is activated and manufactured. In addition, only 1 type of the said raw material may be used for manufacture of activated carbon, and 2 or more types may be used together by arbitrary ratios and combinations.

  The activated carbon activation method is not limited, but the carbonized raw material is contacted with water vapor, carbon dioxide gas, oxygen, other oxidizing gas, etc. at a high temperature by a gas activation method, and the carbonized raw material is zinc chloride, Inactive by evenly impregnating phosphoric acid, sodium phosphate, calcium chloride, potassium sulfide, potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium sulfate, potassium sulfate, calcium carbonate, boric acid, nitric acid, etc. There is a chemical activation method in which activated carbon is obtained by heating in a gas atmosphere and dehydrating and oxidizing the chemical. As an activation method of activated carbon, it can carry out either one or combining both. Furthermore, the gas and / or component to be used may use only 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  In addition, unless activated carbon significantly impairs the effects of the present invention, activated carbon is subjected to heat treatment in an inert atmosphere such as nitrogen and argon prior to use to remove unnecessary surface functional groups and / or develop a crystal structure to conduct electricity. May be improved. The temperature during the heat treatment is usually 500 ° C. or higher, preferably 700 ° C. or higher. Moreover, the upper limit is 2500 degrees C or less normally, Preferably it is 1500 degrees C or less. If the temperature is too low, the activated carbon may not be able to perform the desired treatment, and if the temperature is too high, the activated carbon may not function as an electrode. In addition, only 1 type may be used for an inert gas and it may use 2 or more types together by arbitrary ratios and combinations.

  In addition, when the electrochemical capacitor of the present invention is a hybrid capacitor, the secondary battery electrode is not particularly limited, and any electrode used for the secondary battery can be used. Among these, since it is possible to use the same non-aqueous electrolyte solution, it is preferable to use a secondary battery electrode (hereinafter referred to as “lithium secondary battery electrode” as appropriate) used for a lithium secondary battery. .

  Therefore, in the electrochemical capacitor of the present invention, when the capacitor electrode is used as the positive electrode, the secondary battery electrode used as the negative electrode in the lithium secondary battery (hereinafter referred to as “lithium secondary battery negative electrode” as appropriate). In contrast, when the capacitor electrode is used as a negative electrode, a secondary battery electrode used as a positive electrode in a lithium secondary battery (hereinafter referred to as a “lithium secondary battery positive electrode” as appropriate). It is preferable to use it.

  In addition, as long as the effect of this invention is not impaired remarkably, another substance can be mixed with an electrode by arbitrary ratios and combinations.

[III-2. Negative electrode active material]
The negative electrode active material of the lithium secondary battery negative electrode is not particularly limited as long as it does not significantly impair the effects of the present invention and can electrochemically occlude and release lithium ions. Specific examples thereof include metallic lithium, a carbonaceous material, and an alloy material. In addition, these negative electrode active materials may use only 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Among these, as a specific example of the carbonaceous material, at least one of carbonaceous materials selected from the group consisting of natural graphite, artificial carbonaceous material, and artificial graphite material is 1 to 400 ° C to 3200 ° C. Carbonaceous material that has been heat-treated more than once; an interface in which the negative electrode active material layer is composed of at least two types of carbonaceous materials having different crystallinity and / or orientation and / or the different crystalline and / or oriented carbonaceous materials are in contact with each other The carbonaceous material which has these. These are preferable in terms of a good balance between initial irreversible capacity and high current density charge / discharge characteristics. In addition, the said carbonaceous material may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Specific examples of artificial carbonaceous material and artificial graphite material include coal-based coke, petroleum-based coke, coal-based pitch, petroleum-based pitch, or those obtained by oxidizing these pitches, needle coke, pitch coke, and some of these. Graphitized carbon materials, furnace black, acetylene black, organic pyrolysis products such as pitch-based carbon fibers, carbonizable organic materials, and these carbides or carbonizable organic materials are converted into benzene, toluene, xylene, quinoline, n- Examples include solutions dissolved in low molecular organic solvents such as hexane, and carbides thereof. In addition, the said artificial carbonaceous material and artificial graphite material may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Alloy materials include metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, metals that can be alloyed with lithium such as tin and silicon, and compounds thereof. That is. The above alloy materials may be used alone or in combination of two or more in any ratio and combination.

  As an alloy material used as the negative electrode active material, as long as lithium can be occluded / released, simple metals and alloys that form a lithium alloy, or oxides, carbides, nitrides, silicides, sulfides, phosphorus, and the like thereof. Any compound such as a compound is not particularly limited. Among these, it is the metal simple substance and alloy which form a lithium alloy, and it is preferable that it is a material containing elements other than carbon in 13 group and 14 group elements. Further, it is more preferable that the metal is a simple substance of aluminum, silicon, and tin (these metal elements are hereinafter referred to as “specific metal elements” as appropriate) and a material containing these atoms. In addition, the said metal simple substance and / or compound may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Examples of the negative electrode active material having at least one kind of atom selected from a specific metal element include a single metal of any one specific metal element, an alloy composed of two or more specific metal elements, and one or more specific Alloys composed of metal elements and one or more other metal elements, compounds containing one or more specific metal elements, and oxides, carbides, nitrides, silicides, sulfides, phosphides of the compounds And the like. By using these simple metals, alloys and / or metal compounds as the negative electrode active material, the capacity of the battery can be increased. The above metal simple substance and / or compound may be used alone or in combination of two or more in any ratio and combination.

  In addition, compounds in which these complex compounds are complexly bonded to several elements such as simple metals, alloys, and / or non-metallic elements can also be exemplified. Specifically, an alloy of silicon or tin and a metal that does not operate as a negative electrode can be used. In addition, a complex compound containing four or more elements can be used in combination of tin, a metal that acts as a negative electrode other than tin and silicon, a metal that does not operate as a negative electrode, and a nonmetallic element. . In addition, these compounds may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Among these negative electrode active materials, since the capacity per unit weight is large when a battery is formed, any one metal selected from a specific metal element, two or more alloys selected from a specific metal element, specific Metal element oxides, carbides, nitrides and the like are preferable. In particular, simple metals, alloys, oxides, carbides, nitrides, and the like of silicon and / or tin are preferable from the viewpoint of capacity per unit weight and environmental load. In addition, the said metal simple substance and / or compound may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  In addition, when compared with a single metal or an alloy, the capacity per unit weight is inferior, but since the cycle characteristics are excellent, a compound of silicon and / or tin and one or more elements selected from oxygen, nitrogen or carbon is used. preferable. The content of the metal element in this compound is usually 0.5 mol times or more, preferably 0.7 mol times or more, more preferably 1 mol or more selected from the group consisting of oxygen, nitrogen or carbon. Is 0.9 mole times or more. Moreover, the upper limit is 1.5 mol times or less normally, Preferably it is 1.3 mol times or less, More preferably, it is 1.1 mol times or less. When the amount of the metal element is too small, the capacity per unit weight may be excessively decreased, and when the amount is too large, the superiority over the simple metal or the alloy may be reduced. In addition, these compounds may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations. Further, when an element selected from the group consisting of two or more kinds of oxygen, nitrogen, and carbon is used, the total content of the metal element is within the above range with respect to the total number of moles of the elements included in the group. It is preferable to be within.

  Further, among the alloy-based materials, when a lithium-containing metal composite oxide is used, the lithium-containing metal composite oxide is not particularly limited as long as the effect of the present invention is not significantly impaired and lithium can be occluded / released. However, it is preferable that titanium and / or lithium is contained as a constituent component from the viewpoint of high current density charge / discharge characteristics. Moreover, a lithium containing metal complex oxide may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

Preferred examples of the compound include Li _4/3 Ti _5/3 O ₄ , Li ₁ Ti ₂ O ₄ , Li _4/5 Ti _11/5 O ₄ , Li _4/3 Ti _4/3 Al _1/3 O _4. Is mentioned.

  Furthermore, other materials can be mixed in the negative electrode active material in any ratio and combination as long as the effects of the present invention are not significantly impaired.

[III-3. Cathode active material]
The positive electrode active material of the lithium secondary battery positive electrode is not particularly limited as long as it does not significantly impair the effects of the present invention and can electrochemically occlude and release lithium ions. Among these, a substance containing lithium and at least one transition metal is preferable. Specific examples include lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds. In addition, these positive electrode active materials may use only 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  As the transition metal contained in the lithium transition metal composite oxide, for example, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable from the viewpoint of performance as a positive electrode for a lithium secondary battery. In addition, these transition metals may contain only 1 type and may contain 2 or more types by arbitrary ratios and combinations.

Specific examples of lithium transition metal composite oxides containing these transition metals include lithium-cobalt composite oxides such as LiCoO ₂ , lithium-nickel composite oxides such as LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li ₂ Lithium-manganese composite oxides such as MnO ₄ , and some of the transition metal atoms that are the main components of these lithium transition metal composite oxides are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu , Compounds substituted with other metals such as Zn, Mg, Ga, Zr and Si. In addition, these oxides may use only 1 type and may use 2 or more types together by arbitrary ratios and combinations.

Specific examples of the substituted compound include LiNi _0.5 Mn _0.5 O ₂ , LiNi _0.85 Co _0.10 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , LiMn _1.8 Al _0.2 O ₄ , LiMn _1.5 Ni _0.5 O _{4 and the} like. Can be mentioned. In addition, these compounds may use only 1 type and may use 2 or more types together by arbitrary ratios and combinations.

  As the transition metal of the lithium-containing transition metal phosphate compound, for example, V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable. In addition, these transition metals may contain only 1 type and may contain 2 or more types by arbitrary ratios and combinations.

Specific examples of lithium-containing transition metal phosphate compounds containing these transition metals include iron phosphates such as LiFePO ₄ , Li ₃ Fe ₂ (PO ₄ ) ₃ , and LiFeP ₂ O ₇ , and phosphoric acids such as LiCoPO _4. Cobalt, a part of transition metal atoms that are the main components of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Examples include compounds substituted with other metals such as Nb and Si. In addition, these compounds may use only 1 type and may use 2 or more types together by arbitrary ratios and combinations.

  Although it does not restrict | limit especially as a manufacturing method of a positive electrode active material in the range which does not exceed the summary of this invention, A general method is used as a manufacturing method of an inorganic compound.

  Note that other materials can be mixed in the positive electrode active material in any ratio and combination as long as the effects of the present invention are not significantly impaired.

[III-4. Electrode manufacturing method]
The lithium secondary battery positive electrode and negative electrode can be produced using any known method as long as the effects of the present invention are not significantly impaired. Specifically, the positive electrode active material and the negative electrode active material (hereinafter referred to as “active material” when both are expressed without particular distinction) are respectively bound with a binder, a conductive material, and the like. Examples include a method in which the added material is directly roll-molded to form a sheet electrode, and a method in which compression-molded is used to form a pellet electrode. However, a method of forming a thin film layer (that is, an active material layer) containing the active material on the current collector by a method such as a coating method, a vapor deposition method, a sputtering method, or a plating method is usually used. In this case, by adding a binder, a thickener, a conductive material, a solvent, etc. to each of the active materials to form a slurry, applying this to a current collector, drying, and pressing to increase the density, A positive electrode active material layer and a negative electrode active material layer (hereinafter sometimes referred to simply as “active material layer” when they are expressed without distinction) are formed on a current collector. In addition, said method may use only 1 type and may use 2 or more types together by arbitrary combinations.

  The material for the current collector is arbitrary as long as the effects of the present invention are not significantly impaired. Specific examples of the current collector material include copper, copper alloy, nickel, nickel alloy, stainless steel, and aluminum. Among these, copper is preferable for the negative electrode and aluminum is preferable for the positive electrode from the viewpoint of easy processing into a thin film and electrochemical stability and cost when used as a current collector for each electrode. In addition, these materials may use only 1 type and may use 2 or more types together by arbitrary ratios and combinations.

  Any material can be mixed in the slurry for forming the active material layer as long as the effects of the present invention are not significantly impaired. However, it is usually produced by adding a conductive agent, a binder and / or a thickener to the active material. In addition, as a substance to mix, only 1 type may be used and 2 or more types may be used together by arbitrary ratios and combinations.

[III-4-1. Conductive agent]
Specific examples of the conductive agent include carbon materials such as graphite and carbon black. Examples of the conductive agent mixed with the negative electrode active material include metal materials such as copper and nickel. In particular, it is preferable to use a carbon material as the conductive agent because it also acts as an active material in the negative electrode. In addition, a electrically conductive agent may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

[III-4-2. Binder]
Any binder can be used as long as it is a material that does not significantly impair the effects of the present invention and is safe with respect to the solvent and electrolyte used in the production of the electrode. Specific examples include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber / isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, ethylene / methacrylic acid copolymer, and the like. In addition, a binder may be used individually by 1 type and may use 2 or more types together by arbitrary ratios and combinations.

[III-4-3. Thickener]
Any thickener can be used as long as the effects of the present invention are not significantly impaired. Specific examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. In addition, a thickener may be used individually by 1 type and may use 2 or more types together by arbitrary ratios and combinations.

[III-4-4. slurry]
[III-4-4-1. Dispersion medium]
The slurry for forming the active material layer is prepared by mixing a conductive agent, a binder and / or a thickener as necessary with the active material, and using an aqueous solvent and / or an organic solvent as a dispersion medium. Is done. As the type of the dispersion medium, an aqueous solvent and / or an organic solvent is usually used. In addition, a dispersion medium may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Any aqueous solvent can be used as long as the effects of the present invention are not significantly impaired. As the aqueous solvent, water is usually used, but a solvent other than water such as alcohols such as ethanol and cyclic amides such as N-methylpyrrolidone should be used in a ratio of about 30% by weight or less with respect to water. You can also. In addition, an aqueous solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Any organic solvent can be used as long as the effects of the present invention are not significantly impaired. Usually, cyclic amides such as N-methylpyrrolidone, linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide, aromatic hydrocarbons such as anisole, toluene and xylene, butanol, cyclohexanol And alcohols. Among these, cyclic amides such as N-methylpyrrolidone, and linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide are preferable. In addition, an organic solvent may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

[III-4-4-2. Other properties]
The viscosity of the slurry is not particularly limited as long as it does not significantly impair the effects of the present invention and can be applied onto the current collector. What is necessary is just to prepare suitably by changing the usage-amount of a solvent etc. at the time of preparation of a slurry so that it may become the viscosity which can be apply | coated.

  The slurry is applied on the current collector, dried, and then pressed to form an active material layer. The coating method is not particularly limited as long as the effects of the present invention are not significantly impaired, and a method known per se can be used. Application may be performed by one method alone, or two or more methods may be arbitrarily combined.

  The drying method is not particularly limited as long as the effects of the present invention are not significantly impaired, and any method such as natural drying, heat drying, and reduced pressure drying can be used. Moreover, drying may be performed independently by one type of method, or two or more types of methods may be arbitrarily combined.

In the case of a hybrid capacitor using a positive electrode and / or a negative electrode of a lithium secondary battery, the non-aqueous electrolyte solution must contain at least one lithium salt as an electrolyte. The concentration of the lithium salt is not particularly limited as long as the hybrid capacitor can operate, but is preferably 0.01 mol · dm ⁻³ or more, more preferably 0.1 mol · dm ⁻³ or more, particularly preferably 0.5 mol · dm ⁻³ or more. The upper limit thereof is preferably 10 mol · dm ⁻³ or less, more preferably 5 mol · dm ⁻³ or less, and particularly preferably 3 mol · dm ⁻³ or less. If the concentration is too low, the resistance of the electrolytic solution increases, and there is a possibility that the amount of ions sufficient for the operation of the electrochemical capacitor is insufficient. On the other hand, if the concentration is too high, the viscosity may become too high, or the lithium salt may precipitate at a low temperature.

  Moreover, there is no restriction | limiting in the dimension of an electrode and it is arbitrary unless the effect of this invention is impaired remarkably. However, since the electrodes are usually provided facing each other via a separator described later, the distance between the electrodes is equal to the thickness of the separator described later.

[IV. Separator]
Usually, a separator is interposed between the electrodes in order to prevent a short circuit. In this case, the nonaqueous electrolytic solution of the present invention is usually used by impregnating the electrode and this separator.

  There is no restriction | limiting in particular about the material and shape of a separator, As long as the effect of this invention is not impaired remarkably, it can install arbitrarily. Among these, a resin, glass fiber, inorganic material, etc., which is formed of a material that is stable with respect to the non-aqueous electrolyte solution of the present invention is used, and a porous sheet or a non-woven fabric in which liquid retention is excellent is used. Is preferred. In addition, a separator may be used individually by 1 type and may use 2 or more types together by arbitrary ratios and combinations.

  The material of the resin and the glass fiber separator is arbitrary as long as the effects of the present invention are not significantly impaired. Examples thereof include polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polyethersulfone, and glass filters. Among these, glass filters and polyolefins are preferable, and polyolefins are more preferable. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Although the thickness of the said separator is arbitrary unless the effect of this invention is impaired remarkably, it is 1 micrometer or more normally, 5 micrometers or more are preferable and 10 micrometers or more are more preferable. Moreover, the upper limit is 50 micrometers or less normally, 40 micrometers or less are preferable and 30 micrometers or less are more preferable. If the separator is too thin, the insulation and mechanical strength may be reduced. Moreover, when too thick, performance, such as a charge / discharge characteristic in a large current, may fall, and / or the energy density as a whole electrochemical capacitor may fall.

  Furthermore, when a porous material such as a porous sheet or a nonwoven fabric is used as the separator, the porosity of the separator is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 20% or more and 35% or more. Is preferable, and 45% or more is more preferable. Moreover, the upper limit is 90% or less normally, 85% or less is preferable and 75% or less is more preferable. If the porosity is too small, the membrane resistance may increase and charge / discharge characteristics at a large current may be deteriorated. Moreover, when too large, the mechanical strength of a separator falls and insulation may fall.

  The average pore diameter of the separator is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.05 μm or more. Moreover, the upper limit is 0.5 micrometer or less normally, and 0.2 micrometer or less is preferable. If the average pore diameter is too short, the membrane resistance may increase and the charge / discharge characteristics at a large current may decrease, and if it is too long, a short circuit may occur easily.

  On the other hand, the inorganic material is arbitrary as long as the effects of the present invention are not significantly impaired. Examples thereof include oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, barium sulfate and calcium sulfate. Sulfates such as are used. In addition, these materials may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios and combinations.

  Also, the shape is arbitrary as long as the effects of the present invention are not significantly impaired, but those having a particle shape or fiber shape are preferably used.

  The form is arbitrary as long as the effect of the present invention is not significantly impaired, but a thin film form such as a nonwoven fabric, a woven fabric, or a microporous film is used. In the case of a thin film shape, the pore diameter is arbitrary, but is usually 0.01 μm or more. The upper limit is usually 1 μm. A material having a thin film shape may be used alone, or two or more materials may be used in any combination.

  Furthermore, although thickness is also arbitrary, it is usually 5 micrometers or more. Moreover, the upper limit is 50 micrometers or less normally.

  In addition to the independent thin film shape, a separator in which a composite porous layer containing the inorganic particles is formed on the surface layer of the electrode using a resin binder can be used. For example, a porous layer is formed by using alumina particles having a 90% particle size of less than 1 μm on both surfaces of a positive electrode and using a fluororesin as a binder.

[V. Other components]
The configuration of the electrochemical capacitor of the present invention is arbitrary as long as the effects of the present invention are not significantly impaired. Usually, the non-aqueous electrolyte solution, the electrode, the separator and the like are housed in an exterior body. There is no restriction | limiting in this exterior body, As long as the effect of this invention is not impaired remarkably, arbitrary things can be used.

  The exterior body may have any shape such as a coin shape, a cylindrical shape, a square shape, and an aluminum laminate shape, and is not limited to these shapes.

  Specifically, iron, stainless steel, aluminum or an alloy thereof, nickel, titanium, or the like whose surface is nickel-plated may be used, but the material is not limited to these materials.

  In addition, the internal elements can be arbitrarily arranged as long as the effects of the present invention are not significantly impaired. However, in the coin type, a pair of electrodes are generally opposed to each other with a separator interposed therebetween. In addition, other exterior bodies generally have a laminated structure including the electrode and the separator, and a structure in which a pair of the electrodes are wound spirally via the separator. Is. However, in any case, the structure is not limited.

  Among these combinations, an electric double layer capacitor using activated carbon as the positive electrode active material and / or the negative electrode active material is preferable. Further, it is preferable to use the electrode in combination with a non-aqueous electrolyte solution in which one or more of the preferable organic onium salts and / or alkali metal salts are dissolved as an electrolyte.

  According to the electrochemical capacitor of the present invention, it is possible to obtain the advantage of having a high voltage resistance, that is, having a high energy density.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

<Adjustment of electrolyte>
Example 1
Tetraethylammonium BF ₄ salt was dissolved in 4-fluoro-1,3-dioxolan-2-one at 25 ° C. to a concentration of 1 mol · dm ⁻³ .

(Comparative Example 1)
An electrolyte solution was prepared in the same manner as in Example 1 except that 4-methyl-1,3-dioxolan-2-one was used instead of 4-fluoro-1,3-dioxolan-2-one.

(Comparative Example 2)
An electrolyte solution was prepared in the same manner as in Example 1 except that 4,5-difluoro-1,3-dioxolan-2-one was used instead of 4-fluoro-1,3-dioxolan-2-one.

(Comparative Example 3)
Tetraethylammonium BF ₄ salt was dissolved in 1,3-dioxolan-2-one melted at a little over 40 ° C., cooled to 25 ° C., and adjusted to a concentration of 1 mol · dm ⁻³ .

(Comparative Example 4)
Tetraethylammonium BF ₄ salt was dissolved in a mixed solvent of 1,3-dioxolan-2-one and dimethyl carbonate in a volume ratio of 7: 3 so as to have a concentration of 1 mol · dm ⁻³ at 25 ° C.

<Capacitance measurement of electric double layer capacitor>
The production of the polarizable electrode was performed according to the method shown below.
Coconut powder based activated carbon (specific surface area: 1700 m ² / g, average particle size: 10 μm, steam activated product): 80% by weight, acetylene black: 10% by weight, and polytetrafluoroethylene: 10% by weight After kneading with water, it was pressure-molded with a pressure of 50 kgf / cm ² to form a plate having a thickness of 0.5 mm, and a disk having a diameter of 13 mmφ was punched from this plate. This disk was held at 300 ° C. for 3 hours in a vacuum of 0.1 torr or less, and then allowed to cool in a nitrogen atmosphere.

  Each of the two polarizable electrodes prepared above was impregnated with each of the non-aqueous electrolytes. The two electrodes are placed in a stainless steel outer case with a polyethylene separator in between, and the outer case is caulked through a polypropylene gasket to produce a coin-type electric double layer capacitor cell. did.

Using this cell, constant current-constant voltage charging (CCCV charging) is performed at a current value of 1 mA · cm ⁻² at a typical withstand voltage of 2.5 V as a withstand voltage of a commercially available electric double layer capacitor. The capacitance per weight (F · g ⁻¹ ) was determined.

  table. From the result of 1, when compared with the most common 4-methyl-1,3-dioxolan-2-one (Comparative Example 1) as an electrolyte solvent for an electric double layer capacitor, 4-fluoro-1,3-dioxolane- When 2-one (Example 1) is used, it turns out that the electrostatic capacitance is improving.

  In addition, the electric double layer capacitor using 4,5-difluoro-1,3-dioxolan-2-one (Comparative Example 2) into which two fluorine atoms were introduced as a solvent did not operate stably. While the oxidation resistance is improved, the reduction resistance is lowered. As a result, the withstand voltage of the capacitor is lowered and the operation becomes unstable.

  Furthermore, the electrolytic solution using 1,3-dioxolan-2-one (Comparative Example 3) is considered to be in a supercooled state at 25 ° C. and solidified in the cell.

  Then, in order to use 1,3-dioxolan-2-one as a liquid, when an electrolytic solution containing dimethyl carbonate as a mixed solvent was used (Comparative Example 4), the capacitor operated, but the capacitance was Comparative Example 1. It was almost the same.

  The present invention can be used in any industrial field using an electrochemical capacitor. For example, it is used as a backup power source for consumer electronic devices that are required to be miniaturized, and as a drive power source for portable devices. Furthermore, it can also be used for power applications such as electric vehicles, hybrid vehicles, and power storage.

Claims (8)

A non-aqueous electrolyte solution contained in the electrode element of an electrochemical capacitor, comprising an electrode element comprising a separator and a pair of electrodes opposed to each other with the separator interposed therebetween,
The nonaqueous electrolytic solution for electrochemical capacitors, wherein the nonaqueous electrolytic solution contains 10% by weight or more of 4-fluoro-1,3-dioxolan-2-one. 2. The non-aqueous electrolyte for an electrochemical capacitor according to claim 1, comprising at least one electrolyte selected from the group consisting of organic onium salts and alkali metal salts. The nonaqueous electrolytic solution for an electrochemical capacitor according to claim 2, wherein the organic onium salt is a quaternary ammonium salt and / or a quaternary phosphonium salt. The non-aqueous electrolyte for an electrochemical capacitor according to claim 2 or 3, wherein the alkali metal salt is a lithium salt. Containing at least one compound formed by combining an organic onium cation with one or more anions selected from the group consisting of a BF ₄ anion, a PF ₆ anion, a bis (oxalato) borate anion, and a difluorooxalatoborate anion. The nonaqueous electrolytic solution for an electrochemical capacitor according to any one of claims 1 to 4, characterized in that 6. The nonaqueous electrolytic solution for an electrochemical capacitor according to claim 5, wherein the organic onium cation is a tetraalkylammonium cation. An electrochemical capacitor comprising the nonaqueous electrolytic solution according to any one of claims 1 to 6. The electrochemical capacitor according to claim 7, further comprising a polarizable electrode containing activated carbon.