JP2001217154A - Nonaqueous electrolytic solution electric double-layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution electric double-layer capacitor which can keep an electric characteristic, such as electrical conductivity, etc., and has superior deterioration resistance and a low interface resistance of a nonaqueous electrolytic, solution and is superior in low-temperature characteristic. SOLUTION: This nonaqueous electrolytic solution electric double-layer capacitor is provided with a positive electrode, a negative electrode, and a nonaqueous electrolytic solution containing a supporting salt and a phosphagen derivative of >=2 vol.% and <20 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte electric double layer capacitor used for various types of energy storage, such as a backup power supply and an auxiliary power supply, and more particularly to a non-aqueous electrolyte having excellent deterioration resistance. The present invention relates to an electric double layer capacitor.

[0002]

2. Description of the Related Art A non-aqueous electrolyte electric double layer capacitor is a capacitor utilizing an electric double layer formed between a polarizable electrode and an electrolyte, and was developed and commercialized in the 1970s, and in its infancy in the 1980s. Is a product that has entered a period of growth and development since the 1990s.

Such a non-aqueous electrolyte electric double layer capacitor is characterized in that the cycle of electrically adsorbing ions from the electrolyte on the electrode surface is a charge / discharge cycle, and the cycle of the oxidation-reduction reaction involving mass transfer is a charge / discharge cycle. Battery. For this reason, the nonaqueous electrolyte electric double layer capacitor has excellent instantaneous charge / discharge characteristics as compared with a battery, and the instantaneous charge / discharge characteristics hardly deteriorate even when charge / discharge is repeated. Further, in the non-aqueous electrolyte electric double layer capacitor, since there is no charge / discharge overvoltage at the time of charge / discharge, a simple and inexpensive electric circuit is sufficient. Furthermore, the remaining capacity is easy to understand,
It has durability characteristics over a wide temperature range of -30 to 90 ° C., and has many advantages compared to batteries, such as being non-polluting. It is in the spotlight.

[0004] The non-aqueous electrolyte electric double layer capacitor comprises:
An energy storage device having a positive / negative polarizable electrode and an electrolyte.At a contact interface between the polarizable electrode and the electrolyte, positive / negative charges are arranged facing each other at a very short distance, and Form a double layer. The electrolyte plays an important role as an ion source for forming the electric double layer, and thus is an important substance that determines the basic characteristics of the energy storage device, like the polarizable electrode.

[0005] As the electrolyte, a conventional aqueous electrolyte,
Non-aqueous electrolytes and solid electrolytes are known, but from the viewpoint of improving the energy density of the non-aqueous electrolyte electric double layer capacitor, non-aqueous electrolytes that can set a high operating voltage have been particularly spotlighted. , Practical use is progressing. Examples of such a non-aqueous electrolyte include (C ₂ H ₅ ) ₄ P.BF ₄ and (C ₂ ) in a high dielectric constant organic solvent such as carbonate carbonate (ethylene carbonate, propylene carbonate, etc.) and gamma-butyrolactone. H _5)
4 N · BF _4, etc. of the solute non-aqueous electrolytic solution obtained by dissolving the (supporting salt) is currently commercialized.

[0006] However, these non-aqueous electrolyte electric double layer capacitors have high performance, but are liable to deteriorate.
High performance could not be maintained over a long period of time, which was a problem. Therefore, there has been a strong demand for the development of a technology that can prevent deterioration and maintain various characteristics of the nonaqueous electrolyte electric double layer capacitor at high levels over a long period of time.

[0007] In recent years, particularly with the practical use of nonaqueous electrolyte electric double layer capacitors, the development of nonaqueous electrolyte electric double layer capacitors in electric vehicles, hybrid vehicles, and the like has been expected. Demands are increasing.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention provides a non-aqueous electrolyte electric double layer capacitor having excellent deterioration resistance, low interfacial resistance of a non-aqueous electrolyte, and excellent low-temperature characteristics while maintaining sufficient electric properties such as electric conductivity. The purpose is to provide.

[0009]

Means for solving the above problems are as follows: the present invention provides <1> a positive electrode, a negative electrode, a supporting salt, and 2% by volume or more.
A non-aqueous electrolyte containing less than% by volume of a phosphazene derivative.

<2> Non-aqueous electrolyte contains 2% by volume or more and 20% or more
<1> containing less than% by volume of a phosphazene derivative
3. The non-aqueous electrolyte electric double layer capacitor described in 1. above.

<3> The non-aqueous electrolyte electric double layer capacitor according to <1> or <2>, wherein the supporting salt is a quaternary ammonium salt.

<4> The non-aqueous electrolyte electric double layer capacitor according to any one of <1> to <3>, wherein the non-aqueous electrolyte contains an aprotic organic solvent.

<5> The nonaqueous electrolyte electric double layer capacitor according to <4>, wherein the aprotic organic solvent contains a cyclic or chain ester compound.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The non-aqueous electrolyte electric double layer capacitor of the present invention, a positive electrode,
It has a negative electrode and a non-aqueous electrolyte, and has other members as necessary.

[Positive Electrode] The positive electrode is not particularly limited, but is usually preferably a carbon-based polarizable electrode. Usually, the polarizable electrode has a large specific surface area and a large specific gravity,
Electrodes that are electrochemically inert and have characteristics such as low resistance are preferred.

The polarizable electrode is not particularly limited, but generally contains activated carbon and, if necessary, other components such as a conductive agent and a binder.

-Activated carbon-The raw material of the activated carbon is not particularly limited.
In addition to the phenol resin, various heat-resistant resins, pitches, and the like are preferably exemplified. As the heat resistant resin, for example,
Preferable examples include resins such as polyimide, polyamide, polyamide imide, polyether imide, polyether salsaphone, polyether ketone, bismaleimide triazine, aramid, fluororesin, polyphenylene, and polyphenylene sulfide. These may be used alone or in combination of two or more.

The form of the activated carbon used for the positive electrode is preferably in the form of powder, fiber cloth, or the like, from the viewpoint of increasing the specific surface area and increasing the charging capacity of the nonaqueous electrolyte electric double layer capacitor. . Further, these activated carbons may be subjected to a treatment such as a heat treatment, a stretch molding, a vacuum high-temperature treatment, and a rolling, for the purpose of further increasing the charge capacity of the nonaqueous electrolyte electric double layer capacitor.

-Other components (conductive agent, binder)-The conductive agent is not particularly limited, and examples thereof include graphite and acetylene black. The material of the binder is not particularly limited, and examples thereof include resins such as polyvinylidene fluoride and tetrafluoroethylene.

[Negative electrode] As the negative electrode, a polarizable electrode similar to the positive electrode is preferably used.

[Non-Aqueous Electrolyte] The non-aqueous electrolyte contains a supporting salt, 2% by volume or more and less than 20% by volume of a phosphazene derivative, and, if necessary, other components such as an organic solvent.

-Supporting salt- The supporting salt can be selected from conventionally known ones, but a quaternary ammonium salt is preferable in that it exhibits good electrical properties such as electrical conductivity in a non-aqueous electrolyte.

The quaternary ammonium salt is a solute that plays a role as an ion source for forming an electric double layer in the non-aqueous electrolyte, and effectively improves the electrical conductivity of the non-aqueous electrolyte. In order to be able to do so, a quaternary ammonium salt capable of forming a multivalent ion is required.

As the quaternary ammonium salt, for example,
If (CH_Three)_FourN ・ BF_Four, (CH_Three) _ThreeC_TwoH_FiveNB
F_Four, (CH_Three)_Two(C_TwoH_Five)_TwoN ・ BF_Four, CH_Three(C
_TwoH_Five)_ThreeN ・ BF_Four, (C_TwoH_Five)_FourN ・ BF_Four, (C_ThreeH₇)
_FourN ・ BF_Four, CH_Three(C_FourH₉)_ThreeN ・ BF_Four, (C_FourH₉)_Four
N ・ BF_Four, (C₆H₁₃)_FourN ・ BF_Four, (C_TwoH_Five)_FourN
ClO_Four, (C_TwoH_Five)_FourN ・ BF_Four, (C_TwoH_Five)_FourN ・ PF
₆, (C_TwoH_Five)_FourN ・ AsF₆, (C_TwoH_Five)_FourN ・ Sb
F₆, (C_TwoH_Five)_FourN ・ CF_ThreeSO_Three, (C_TwoH_Five)_FourNC_Four
F₉SO_Three, (C_TwoH_Five)_FourN ・ (CF_ThreeSO_Two)_TwoN, (C_Two
H_Five)_FourN ・ BCH_Three(C_TwoH_Five)_Three, (C_TwoH_Five)_FourNB
(C_TwoH_Five)_Four, (C_TwoH_Five)_FourNB (C_FourH₉)_Four, (C_TwoH
_Five) _FourNB (C₆H_Five)_FourAnd the like. Also,
These anions (eg, BF_Four, ・ ClO_Four, A
sF₆Etc.) ・ PF₆Phosphazene induction
From the viewpoint that the effect of preventing body deterioration works effectively,
It is. Hexafluroate of these quaternary ammonium salts
Oroline phosphate may be used. Furthermore, large polarizability
Can improve the solubility,
Ammonium salt having an alkyl group bonded to an N atom
May be used.

Further, as the quaternary ammonium salt,
For example, compounds represented by the following structural formulas (1) to (10) are preferable. In addition, structural formulas (1) to (1)
The one in which the anion part (.BF ₄ ) in 0) is replaced with .PF ₆ is also preferably mentioned from the viewpoint that the effect of preventing the deterioration of the phosphazene derivative works effectively.

[0026]

Embedded image In the above structural formula, Me represents a methyl group;
Et represents an ethyl group.

Among these quaternary ammonium salts, (CH ₃ ) ₄ N ⁺ , (C ₂ H ₅ ) ₄ N ^{+ and the} like are generated as cations, particularly from the viewpoint of securing high electric conductivity. The resulting salts are preferred. Further, a salt capable of generating an anion having a small formula weight is preferable. These quaternary ammonium salts may be used alone or in combination of two or more.

The amount of the supporting salt is preferably 0.2 to 1.5 mol, more preferably 0.5 to 1.0 mol, per 1 kg of the nonaqueous electrolyte (solvent component). When the amount is less than 0.2 mol, sufficient electric conductivity of the non-aqueous electrolyte may not be secured. On the other hand, when the amount exceeds 1.5 mol, the non-aqueous The viscosity of the liquid may increase, and electrical characteristics such as electrical conductivity may decrease.

-Phosphazene derivative- The reason why the non-aqueous electrolyte contains the phosphazene derivative is presumed as follows. In a non-aqueous electrolyte electric double layer capacitor, a compound generated by the decomposition or reaction of the electrolyte or the supporting salt in the non-aqueous electrolyte corrodes the electrode and its peripheral members, and is supported by the decomposition or reaction. Since the amount of the salt itself is reduced, it is considered that the electric characteristics are hindered and the performance of the capacitor is deteriorated.

On the other hand, the phosphazene derivative suppresses the decomposition or reaction of the electrolytic solution or the supporting salt and contributes to stabilization (particularly, it works effectively with PF ₆ salt). Therefore,
By containing the phosphazene derivative in the conventional non-aqueous electrolyte, it becomes possible to prevent deterioration while maintaining the electrical characteristics.

The content of the phosphazene derivative in the non-aqueous electrolyte must be 2% by volume or more and less than 20% by volume, and preferably 3% by volume or more and less than 20% by volume. When the content is within the numerical range, the deterioration can be suitably suppressed. In the present invention, the term “deterioration” refers to corrosion of an electrode and its surrounding members due to decomposition of an electrolytic solution and a supporting salt and generation of a compound accompanying the reaction, and a reduction in the concentration of a supporting salt accompanying the electrode. Was evaluated by the following “stability evaluation method”.

—Method of Evaluating Stability— (1) First, after preparing a non-aqueous electrolyte solution containing a supporting salt, the moisture content is measured. Next, the concentration of hydrogen fluoride in the non-aqueous electrolyte is measured by NMR and GC-MS. Furthermore, after observing the color tone of the non-aqueous electrolyte visually, the electrical conductivity is measured. (2) After leaving the non-aqueous electrolyte in the glove box for two months, the moisture content and the concentration of hydrogen fluoride were measured again,
The color tone is observed, the electric conductivity is measured, and the stability is evaluated by the change in the obtained numerical value.

The phosphazene derivative is not particularly limited as long as it is a liquid at ordinary temperature (25 ° C.). For example, a chain phosphazene derivative represented by the following general formula (1) or the following general formula (2) Suitable examples include a cyclic phosphazene derivative represented by

General formula (1)

Embedded image However, in the general formula (1), R ¹ , R ² , and R
³ represents a monovalent substituent or a halogen element. X is carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic,
Represents an organic group containing at least one element selected from the group consisting of antimony, bismuth, oxygen, sulfur, selenium, tellurium, and polonium. Y ¹ , Y ² and Y
³ represents a divalent linking group, a divalent element, or a single bond.

Formula (2) (PNR ⁴ ₂ ) _{n In} the above formula (2), R ⁴ represents a monovalent substituent or a halogen element. n represents 3 to 15.

In the general formula (1), R ¹ , R ² and R ³ are not particularly limited as long as they are a monovalent substituent or a halogen element. , An alkyl group, a carboxyl group, an acyl group, an aryl group and the like. Further, as the halogen element, for example, the above-mentioned halogen elements are preferably exemplified. Among these, an alkoxy group is particularly preferred in that the viscosity of the non-aqueous electrolyte can be reduced. R ^{1 to} R ³ may all be the same type of substituent, or some of them may be different types of substituents.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group and the like, and an alkoxy-substituted alkoxy group such as a methoxyethoxy group and a methoxyethoxyethoxy group. Among these, as R ^{1 to} R ³ , all methoxy groups, ethoxy groups, methoxyethoxy groups, or methoxyethoxyethoxy groups are preferable, and from the viewpoints of low viscosity and high dielectric constant, all methoxy groups, ethoxyethoxy groups, or methoxyethoxyethoxy groups are preferable. Particularly preferred is a group or an ethoxy group.

Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and the like. As the acyl group, a formyl group, an acetyl group,
Examples include a propionyl group, a butyryl group, an isobutyryl group, and a valeryl group. Examples of the aryl group include a phenyl group, a tolyl group, and a naphthyl group.

The hydrogen element in these substituents is preferably substituted with a halogen element as described above.

In the general formula (1), the groups represented by Y ¹ , Y ² and Y ³ include, for example, CH ₂ group, oxygen, sulfur, selenium, nitrogen, boron, aluminum, scandium , Gallium, yttrium, indium, lanthanum, thallium, carbon, silicon, titanium, tin, germanium, zirconium, lead, phosphorus, vanadium, arsenic, niobium, antimony, tantalum, bismuth,
Examples include groups containing elements such as chromium, molybdenum, tellurium, polonium, tungsten, iron, cobalt, and nickel. Among these, a CH ₂ group, and a group containing elements such as oxygen, sulfur, selenium, and nitrogen are preferable. , Especially sulfur,
Groups containing the element selenium are preferred. Y ^{1 to} Y ³ may be all the same type or some may be different types.

In the general formula (1), X is
From the viewpoint of harmfulness and environmental considerations, carbon, silicon,
An organic group containing at least one element selected from the group consisting of nitrogen, phosphorus, oxygen, and sulfur is preferable, and an organic group having a structure represented by the following general formula (3) is more preferable.

General formula (3)

Embedded image However, in the general formula (3), R ^{5 to} R ⁹ represent a monovalent substituent or a halogen element. Y ^{5 to} Y ⁹ represent a divalent linking group, a divalent element, or a single bond, and Z represents a divalent group or a divalent element.

In the general formula (3), R ^{5 to} R ⁹ are preferably the same monovalent substituents or halogen elements as described for R ^{1 to} R ³ in the general formula (1). No. Further, these may be of the same type within the same organic group, or some may be of different types. R ⁵ and R ⁶ , and R ⁸ and R ⁹ may combine with each other to form a ring. In the general formula (3), as the group represented by Y ^{5 to} Y ⁹ , the same divalent linking group as described for Y ^{1 to} Y ³ in the general formula (1) or 2
Similarly, a group containing an element of sulfur or selenium is particularly preferable. These may be of the same type or different from each other in the same organic group. In the general formula (3), Z represents, for example, a CH ₂ group, a CHR (R represents an alkyl group, an alkoxyl group, a phenyl group, etc .; the same applies hereinafter);
In addition to NR groups, oxygen, sulfur, selenium, boron, aluminum, scandium, gallium, yttrium, indium, lanthanum, thallium, carbon, silicon, titanium, tin, germanium, zirconium, lead, phosphorus, vanadium, arsenic, niobium, antimony , Tantalum, bismuth,
Examples include groups containing elements such as chromium, molybdenum, tellurium, polonium, tungsten, iron, cobalt, and nickel. Among these, in addition to the CH ₂ group, CHR group, and NR group, include the elements of oxygen, sulfur, and selenium. Groups are preferred, and groups containing elements of sulfur and selenium are particularly preferred.

In the general formula (3), as the organic group, a phosphorus-containing organic group represented by the organic group (A) is particularly preferable in that it can particularly effectively impart deterioration resistance. Further, when the organic group is an organic group containing sulfur as represented by the organic group (B), it is particularly preferable in terms of reducing the interface resistance of the non-aqueous electrolyte.

In the general formula (2), R ⁴ is not particularly limited as long as it is a monovalent substituent or a halogen element. Examples of the monovalent substituent include an alkoxy group, an alkyl group, a carboxyl group and an acyl group. Group, aryl group and the like. Further, as the halogen element, for example, the above-mentioned halogen elements are preferably exemplified. Among these, an alkoxy group is particularly preferred in that the viscosity of the non-aqueous electrolyte can be reduced. Examples of the alkoxy group include a methoxy group, an ethoxy group, a methoxyethoxy group, a propoxy group,
Phenoxy groups and the like. Among these, a methoxy group, an ethoxy group and a methoxyethoxy group are particularly preferred. The hydrogen element in these substituents is preferably substituted with a halogen element as described above.

In the general formulas (1) to (3), R ¹ to
By appropriately selecting R ⁹ , Y ^{1 to} Y ³ , Y ^{5 to} Y ⁹ , and Z, it becomes possible to synthesize a nonaqueous electrolyte having more favorable viscosity and solubility. These phosphazene derivatives may be used alone or in combination of two or more.

The flash point of the phosphazene derivative is not particularly limited.
C. or higher, and more preferably 150 C. or higher.

-Organic solvent- As the organic solvent, an aprotic organic solvent is particularly preferred from the viewpoint of safety. When the non-aqueous electrolyte contains the aprotic organic solvent, it is easy to lower the viscosity of the non-aqueous electrolyte and improve the electrical conductivity of the non-aqueous electrolyte.

The aprotic organic solvent is not particularly restricted but includes, for example, ether compounds and ester compounds. Specifically, 1,2-dimethoxyethane, tetrahydrofuran, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, γ-butyrolactone, γ-valerolactone, and the like are preferable. Among these, ethylene carbonate, propylene carbonate, cyclic ester compounds such as γ-butyrolactone, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate,
A chain ester compound such as ethyl methyl carbonate is preferred. Cyclic ester compounds are particularly suitable from the viewpoint of high relative dielectric constant and excellent dissolving ability of the supporting salt, and chain ester compounds are low in viscosity and very effective in lowering the viscosity. . These may be used alone or in combination of two or more.

The viscosity of the aprotic organic solvent at 25 ° C. is not particularly limited, but may be 10 mPa · s.
(10 cP) or less is preferable.

[Other members] Examples of the other members include a separator, a current collector, a container, and the like. The separator is interposed between the positive and negative electrodes for the purpose of, for example, preventing short circuit of the non-aqueous electrolyte electric double layer capacitor. The separator is not particularly limited, and a known separator that is usually used as a separator for a non-aqueous electrolyte electric double layer capacitor is preferably used. Preferred examples of the material include a microporous film, a nonwoven fabric, and paper. Specifically, a nonwoven fabric, a thin film, and the like made of a synthetic resin such as polytetrafluoroethylene, polypropylene, and polyethylene are preferably used. Among these, a polypropylene or polyethylene microporous film having a thickness of about 20 to 50 μm is particularly preferable.

The current collector is not particularly limited, and a known one which is usually used as a current collector for a nonaqueous electrolyte electric double layer capacitor is preferably used. As the current collector, those having excellent electrochemical corrosion resistance, chemical corrosion resistance, workability, mechanical strength, and low cost are preferable, for example,
A current collector layer of aluminum, stainless steel, conductive resin or the like is preferable.

The container is not particularly limited, and a well-known container usually used as a container for a non-aqueous electrolyte electric double layer capacitor is preferably exemplified. As the material of the container, for example, aluminum, stainless steel, conductive resin and the like are preferable.

As the other members in addition to the separator, the current collector, and the container, well-known members usually used for a non-aqueous electrolyte electric double layer capacitor are preferably exemplified.

[Non-Aqueous Electrolyte Electric Double Layer Capacitor] The form of the non-aqueous electrolyte electric double layer capacitor described above is not particularly limited, and may be a cylinder type (cylindrical type, square type) or a flat type (coin type). And other known forms. These non-aqueous electrolyte electric double layer capacitors, for example, various electronic equipment, industrial equipment, for memory backup of aircraft equipment, toys, cordless equipment,
It is suitably used as a power source for electromagnetic devices such as gas appliances and instant water heaters, and as a power source for watches such as watches, wall clocks, solar clocks, and AGS watches.

The non-aqueous electrolyte electric double layer capacitor of the present invention described above has excellent deterioration resistance, low interfacial resistance of the non-aqueous electrolyte, low temperature while maintaining sufficient electric characteristics such as electric conductivity. Excellent characteristics.

[0057]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. Example 1 [Preparation of Nonaqueous Electrolyte] A phosphazene derivative (chain EO) was added to 49 ml of γ-butyrolactone (aprotic organic solvent).
Type phosphazene derivative (in the general formula (1), X
Is the structure of the organic group (A) represented by the general formula (3), wherein Y ^{1 to} Y ³ and Y ^{5 to} Y ⁶ are all single bonds,
^{1 to} R ³ and R ^{5 to} R ⁶ are all ethoxy groups;
Is oxygen)), 1 ml is added (2% by volume),
Further, 1 mol / kg of tetraethylammonium hexafluorophosphate (C ₂ H ₅ ) ₄ N.PF ₆ (supporting salt)
To obtain a non-aqueous electrolyte.

—Evaluation of Deterioration— The obtained non-aqueous electrolyte was subjected to electric conductivity immediately after preparation of the non-aqueous electrolyte and after leaving it in a glove box for 2 months in the same manner as in the above-mentioned “stability evaluation method”. Was measured and calculated, and the deterioration was evaluated. Further, the color tone change of the non-aqueous electrolyte immediately after preparation of the non-aqueous electrolyte and after leaving it in the glove box for 2 months was visually observed. Table 1 shows the results.
Further, when the color tone change of the non-aqueous electrolyte immediately after preparation of the non-aqueous electrolyte and after being left in the glove box for 2 months was visually observed, no change was observed.

-Measurement of Electric Conductivity- Using the obtained non-aqueous electrolyte, a non-aqueous electrolyte electric double layer capacitor was prepared as described below, and a conductivity meter (commercially available) was applied while applying a constant current of 5 mA. Name: CDM210, manufactured by Radiometer Trading Co., Ltd.) was used to measure the electrical conductivity. The electric conductivity of the non-aqueous electrolyte at 25 ° C. is at a level having no practical problem if it is 5.0 mS / cm or more.

-Preparation of Nonaqueous Electrolyte Electric Double Layer Capacitor- [Preparation of Positive Electrode / Negative Electrode (Polarizable Electrode)] Activated carbon (trade name:
Kuractive-1500, manufactured by Kuraray Chemical Co., Ltd.), acetylene black (conductive agent) and tetrafluoroethylene (PTFE) (binder), respectively.
8 by mass ratio (activated carbon / acetylene black / PTFE)
/ 1/1 to obtain a mixture. 100 mg of the obtained mixture was collected and placed in a pressure-resistant carbon container having a diameter of 20 mm, and a pressure of 150 kgf / cm ² ,
Powder compaction was performed under normal temperature conditions to produce a positive electrode and a negative electrode (polarizable electrode).

[Preparation of Nonaqueous Electrolyte Electric Double Layer Capacitor] The obtained positive electrode and negative electrode, an aluminum metal plate (current collector) (thickness: 0.5 mm), and a polypropylene / polyethylene plate (separator) (thickness: (25 μm), and was sufficiently dried by vacuum drying.

The above-mentioned cell was impregnated with the above-mentioned non-aqueous electrolyte to produce a non-aqueous electrolyte electric double layer capacitor.

Example 2 In “Preparation of Nonaqueous Electrolyte Solution” in Example 1, the phosphazene derivative (chain EO-type phosphazene derivative (in the above formula (1), X is represented by the formula (3)) a structure of the organic group (a) is, Y ¹ ~
Y ³ and Y ^{5 to} Y ⁶ are all single bonds, and R ^{1 to} R ³ ,
And a non-aqueous electrolyte solution similar to that of Example 1 except that the addition amount of R ^{5 to} R ⁶ is an ethoxy group and Z is oxygen)) is changed to 50% by volume. Was prepared and the deterioration was evaluated. Table 1 shows the results. Further, when the color tone change of the non-aqueous electrolyte immediately after preparation of the non-aqueous electrolyte and after being left in the glove box for 2 months was visually observed, no change was observed.

(Comparative Example 1) In “Preparation of Nonaqueous Electrolyte Solution” of Example 1, a phosphazene derivative (a chain EO-type phosphazene derivative (in the above general formula (1), X is represented by the general formula (3)) a structure of the organic group (a) is, Y ¹ ~
Y ³ and Y ^{5 to} Y ⁶ are all single bonds, and R ^{1 to} R ³ ,
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that R ^{5 to} R ⁶ were all ethoxy groups, and Z was oxygen. Was. Table 1 shows the results
Shown in Also, the color tone change of the non-aqueous electrolyte immediately after preparation of the non-aqueous electrolyte and after being left in the glove box for 2 months was visually observed. Was observed.

(Comparative Example 2) In "Preparation of non-aqueous electrolyte" in Example 1, ethylene carbonate / diethyl carbonate (volume ratio: 1/1) was used instead of γ-butyrolactone (aprotic organic solvent). Using an aprotic organic solvent, a phosphazene derivative (a chain EO-type phosphazene derivative (in the general formula (1), X is a structure of the organic group (A) represented by the general formula (3)); ¹ to
Y ³ and Y ^{5 to} Y ⁶ are all single bonds, and R ^{1 to} R ³ ,
A non-aqueous electrolyte was prepared in the same manner as in Example 1 except that R ^{5 to} R ⁶ were all ethoxy groups, and Z was oxygen. Was. Table 1 shows the results
Shown in Also, the color tone change of the non-aqueous electrolyte immediately after preparation of the non-aqueous electrolyte and after being left in the glove box for 2 months was visually observed. Was observed.

[0066]

[Table 1]

[0067]

As described above, according to the present invention, while maintaining sufficient electrical characteristics such as electrical conductivity, excellent in degradation resistance,
It is possible to provide a nonaqueous electrolyte electric double layer capacitor having a low interface resistance of the nonaqueous electrolyte and excellent low-temperature characteristics.

Claims (5)

[Claims] 1. A non-aqueous electrolyte electric double layer capacitor comprising: a positive electrode; a negative electrode; and a non-aqueous electrolyte containing a supporting salt and a phosphazene derivative in an amount of 2% by volume or more and less than 20% by volume. 2. The method according to claim 1, wherein the non-aqueous electrolyte contains 3% by volume or more and 20% by volume.
2. The non-aqueous electrolyte electric double layer capacitor according to claim 1, wherein the non-aqueous electrolyte contains less than 2 phosphazene derivatives. 3. The non-aqueous electrolyte electric double layer capacitor according to claim 1, wherein the supporting salt is a quaternary ammonium salt. 4. The non-aqueous electrolyte electric double layer capacitor according to claim 1, wherein the non-aqueous electrolyte contains an aprotic organic solvent. 5. The non-aqueous electrolyte electric double layer capacitor according to claim 4, wherein the aprotic organic solvent contains a cyclic or chain ester compound.