WO2004093110A1 - Nonaqueous electrolyte and electric double-layer capacitor provided with it - Google Patents

Abstract

A nonaqueous electrolyte being excellent in performance of penetrating into an electric double-layer capacitor-use electrode and capable of reducing the internal resistance of a capacitor, and a nonaqueous electrolyte double-layer capacitor provided with the nonaqueous electrolyte and having a small internal resistance; especially a nonaqueous electrolyte characterized in that time required for the contact angle θ of the nonaqueous electrolyte (1) with respect to an electrode (2) of the capacitor to reach up to 2˚ is less than 0.5 sec after the nonaqueous electrolyte (1) is dripped onto the electrode (2), and a nonaqueous electrolyte double-layer capacitor provided with this nonaqueous electrolyte, an anode and a cathode.

Description

 Technical Field

 TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte and an electric double layer capacitor provided with a non-aqueous electrolyte, and more particularly to a non-aqueous electrolyte having excellent permeability to electrodes of an electric double layer capacitor. Background art

 The non-aqueous electrolyte electric double layer capacitor is a capacitor that uses an electric double layer formed between the electrode and telegraph solution, was developed and commercialized in the 1970s, It is a product that has reached its infancy and has entered a period of growth and development since the 1990s. Such a non-aqueous electrolyte electric double layer capacitor has a charge / discharge cycle in which a cycle for electrically adsorbing ions from the electrolyte on the electrode surface is a charge / discharge cycle. It is different from a battery that is a discharge cycle. Therefore, the non-aqueous electrolyte electric double layer capacitor has excellent instantaneous charge / discharge characteristics as compared to a battery and does not involve a chemical reaction. Therefore, even if charge / discharge is repeated, the instant charge / discharge characteristics hardly deteriorate. In addition, a simple and inexpensive electric circuit is sufficient for a non-aqueous electrolyte electric double layer capacitor since there is no charge / discharge overvoltage during charge / discharge. In addition, the battery has many outstanding features compared to batteries, such as easy-to-understand remaining capacity, durability temperature characteristics over a wide temperature range of -30 to 90 ° C, and no pollution. It is in the spotlight as a new energy storage product that is environmentally friendly. Because of these features, they have come to the limelight as a power source for electric vehicles, fuel cell vehicles, and hybrid electric vehicles when regenerating energy or starting engines.

The electric double layer capacitor is an energy storage device having positive and negative electrodes and an electrolyte, and has an extremely short distance at a contact interface between the electrode and the electrolyte. Positive and negative charges are arranged to face each other to form an electric double layer. Electrolyte plays an important role as an ion source for forming an electric double layer, and thus is an important substance that determines the basic characteristics of energy storage devices, like electrodes. As the electrolyte, an aqueous electrolyte, a non-aqueous electrolyte, a solid electrolyte, and the like are conventionally known. However, from the viewpoint of improving the energy density of an electric double layer capacitor, a non-aqueous electrolyte capable of setting a high operating voltage is used. The liquid has been particularly spotlighted, and its practical use is progressing. Such non-aqueous electrolytes include, for example, organic solvents having a high dielectric constant such as carbonate carbonate (ethylene carbonate, propylene carbonate, etc.), γ-petit mouth rataton, and the like, such as (C ₂ H ₅ ) ₄ P ■ BF ₄ , Non-aqueous electrolytes in which solutes (supporting salts) such as (C ₂ H ₅ ) ₄ N ■ BF ₄ are dissolved are currently in practical use.

 However, in the conventional non-aqueous electrolyte electric double layer capacitor, since the electrolyte does not penetrate well into the electrode of the capacitor and other capacitor members, the electrodes and other capacitor members are placed in the capacitor container. After filling, it was necessary to inject the electrolyte into the container while evacuating the container. For this reason, the conventional non-aqueous electrolyte electric double-layer capacitor had a complicated manufacturing process and low productivity. On the other hand, when the non-aqueous electrolyte was injected without evacuating the container, it was necessary to leave the capacitor until the non-aqueous electrolyte permeated the electrodes.

 Further, the conventional nonaqueous electrolyte has a problem that the internal resistance is large because of poor permeability to the electrode. Here, assuming that the internal resistance of the capacitor is R, the current value that can be extracted from the capacitor is I, and the voltage drop value is E, the voltage drops according to E = IR according to Ohm's law. That is, by suppressing the internal resistance of the capacitor, the voltage drop of the capacitor can be suppressed, and as a result, the capacity that can be taken out of the capacitor is increased to improve the efficiency of the capacitor, and to improve the pulse discharge characteristics ゃ large current discharge characteristics. be able to.

On the other hand, in “Electric Double Layer Capacitors and Energy Storage System” published by Okamura Dio and published by Nikkan Kogyo Shimbun, in order to reduce the internal resistance of the capacitor, the electrode material is devised by adding a conductive agent and controlling the electrode material particle size. Etc. are introduced. In addition, the capacity of the separator Various developments have been introduced from the viewpoint of optimizing the material for the control of separator pores, etc., as the wettability of the electrolytic solution is also an important factor in improving the characteristics of the capacitor in the case of Sita members. There is no mention of efforts to improve wettability by improving the electrolyte itself. Disclosure of the invention

 On the other hand, in large electric double layer capacitors, which are recently required as main power supply or auxiliary power supply for electric vehicles and fuel cell vehicles, pulse discharge characteristics ゃ large current discharge and charging characteristics are extremely important. There is an urgent need for a technology to reduce the internal resistance of the capacitor, in order to improve the characteristics.

 Accordingly, an object of the present invention is to provide a non-aqueous electrolyte solution which solves the above-mentioned problems of the prior art, has excellent permeability to an electrode for an electric double layer capacitor, and can reduce the internal resistance of a capacitor. It is in. Another object of the present invention is to provide a non-aqueous electrolyte electric double layer capacitor having a low internal resistance, comprising the non-aqueous electrolyte. The present inventors have conducted intensive studies to achieve the above object, and as a result, added a specific compound to a conventional non-aqueous electrolyte for an electric double layer capacitor. The present inventors have found that the configuration makes it possible to improve the permeability of the non-aqueous electrolyte into the electrodes and to reduce the internal resistance of the electric double layer capacitor.

■ ~ f ^ .tsu / o

 That is, the non-aqueous electrolyte of the present invention has a time of 0.5 after the non-aqueous electrolyte is dropped on the electrode for an electric double layer capacitor until the contact angle of the non-aqueous electrolyte with respect to the electrode becomes 2 ° or less. Less than a second.

 In a preferred example of the non-aqueous electrolyte according to the present invention, the active material of the electrode is porous carbon. Here, activated carbon is particularly preferred as the porous carbon.

In another preferred embodiment of the non-aqueous electrolyte according to the present invention, the non-aqueous electrolyte contains a compound having at least one of phosphorus and nitrogen in a molecule. Where the compound In this case, a compound having phosphorus and nitrogen in the molecule is preferable, and a compound having phosphorus-nitrogen double bond is more preferable. It is preferable that the non-aqueous electrolyte further contains an aprotic organic solvent.

 Further, a non-aqueous electrolyte electric double layer capacitor of the present invention includes the non-aqueous electrolyte, a positive electrode, and a negative electrode. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a schematic view of a non-aqueous electrolyte dropped on a capacitor electrode.

 FIG. 2 is a graph showing the change over time of the contact angle of the electroporous solution of Example 1 and Comparative Example 1 with respect to the electrode of the capacitor. BEST MODE FOR CARRYING OUT THE INVENTION

<Non-aqueous electrolyte>

 Hereinafter, the non-aqueous electrolyte of the present invention will be described in detail with reference to FIG. The non-aqueous electrolyte 1 of the present invention is obtained by dropping the non-aqueous electrolyte 1 on the electrode 2 of the electric double layer capacitor, and then adjusting the contact angle の of the non-aqueous electrolyte 1 to the electrode 2 to 2 ° or less. It is characterized in that the time until it becomes less than 0.5 seconds.

 Since the conventional nonaqueous electrolyte for electric double layer capacitors dropped on the capacitor electrodes, the time required for the contact angle of the nonaqueous electrolyte to the electrodes to become 2 ° or less exceeded 0.5 seconds, Although the permeability to the electrodes is poor and the internal resistance is increased, the electrolyte of the present invention has a very good permeability to the electrodes, so that the internal resistance of the capacitor can be suppressed to a low level. Therefore, the non-aqueous electrolyte electric double layer capacitor provided with the non-aqueous electrolyte of the present invention has a significantly improved pulse discharge characteristic ゃ large current discharge and charging characteristic as compared with the conventional non-aqueous electrolyte electric double layer capacitor. It is particularly suitable as a large electric double layer capacitor for electric vehicles and fuel cell vehicles.

The non-aqueous electrolyte solution of the present invention preferably has a viscosity at 25 ° C. of 10 OmPa-s (10 cP) or less. Good. Non-aqueous electrolytic solution whose liquid occupancy at 25 ° C exceeds 10 mPa's (10 cP) is dropped on the electrode of the capacitor, and the time until the contact angle of the non-aqueous electrolytic solution to the electrode becomes 2 ° or less However, the effect of reducing the internal resistance of the capacitor is insufficient. From the viewpoint of further improving the permeability to the electrode, the nonaqueous electrolyte of the present invention more preferably has a viscosity at 25 ° C. of 5 mPa's (5 cP) or less.

 The nonaqueous electrolytic solution of the present invention is not particularly limited as long as it satisfies the above-mentioned properties relating to the permeability to the electrode, and is a compound containing at least a supporting salt and containing at least one of phosphorus and nitrogen in a molecule. Is preferable. In addition, the non-aqueous electrolyte may contain an aprotic organic solvent such as a carbonate or a nitrile / Reich compound, if necessary.

 Examples of the compound having phosphorus in the molecule that can be suitably used in the nonaqueous electrolyte of the present invention include a phosphate compound, a polyphosphate compound, a condensed phosphate compound, and the like.

 Examples of the compound having nitrogen in the molecule that can be suitably used in the non-aqueous electrolyte of the present invention include cyclic nitrogen-containing compounds such as triazine compounds, guanidine compounds, and pyrrolidine compounds.

Further, the compound having phosphorus and nitrogen in the molecule which can be suitably used in the non-aqueous electrolyte of the present invention includes a phosphazene compound, an isomer of the phosphazene compound, a phosphazene compound, and a compound having phosphorus in the molecule. And the compound exemplified as the compound having nitrogen in the molecule. Note that these compounds having phosphorus and nitrogen in the molecule are naturally examples of the compound having phosphorus in the molecule and the compound having nitrogen in the molecule. Among the compounds containing at least one of phosphorus and nitrogen in the molecule, compounds having phosphorus and nitrogen in the molecule are preferable from the viewpoint of cycle characteristics. In addition, among the above compounds having phosphorus and nitrogen in the molecule, compounds having a phosphorus-nitrogen double bond, such as a phosphazene compound, are preferred from the viewpoint of improving thermal stability and high-temperature storage characteristics. Compounds are particularly preferred.

 Specific examples of the phosphazene include a chain phosphazene compound represented by the following formula (I) and a cyclic phosphazene compound represented by the following formula (II).

γ2— p ₌ Ν— X ¹ … (I)

Y ³ R ³ (wherein, RR ² and R ³ each independently represent a monovalent substituent or a halogen element; X ¹ represents carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic, antimony , Bismuth, oxygen, sulfur, selenium, tellurium, and polonium represent a substituent containing at least one element selected from the group consisting of; Y ² and ³ each independently represent a divalent linking group, (NPR ⁴ ₂ ) _n · ■ ■ (II)

(Wherein, R ⁴ represents a monovalent substituent or a halogen element. N represents 3 to 15.) Among the phosphazene compounds represented by the formula (I) or (II), 25 ° C ( (Room temperature) is preferred. The viscosity of the liquid phosphazene compound at 25 ° C. is preferably 300 mPa's (300 cP) or less, more preferably 20 mPa · s (20 cP) or less, and particularly preferably 5 mPa-s (5 cP) or less. The viscosity in the present宪明uses a viscosity meter (R-type viscometers Mo del RE500- SL, manufactured by Toki Sangyo (Ltd.)), lrpm, 2rpm, 3rpra s 5rpm, 7rpm, 10rpm, 20rpm, and The measurement was carried out for 120 seconds at each rotation speed of 50 rpm, and the rotation speed when the indicated value became 50 to 60% was used as an analysis condition, and the viscosity at that time was measured. When the viscosity at 25 ° C greater than 300mPa's ⁽³ 00cP), supporting salt is less soluble, electrodes, wettability is lowered into the separator or the like, significantly reduced Ion conductivity by increasing the viscosity resistance of the electrolyte However, the performance is insufficient especially when used under low temperature conditions such as below the freezing point. In addition, these phosphazene compounds are liquid As a result, it has the same conductivity as ordinary liquid electrolytes, and exhibits excellent cycle characteristics when used in electrolytes for capacitors.

In the formula (I), RR ² and R ³ are not particularly limited as long as they are —valent substituents or halogen elements. Examples of the monovalent substituent include an alkoxy group, an alkyl group, a hydroxyl group, an acyl group, an aryl group, and the like. Among them, an alkoxy group is preferable because the viscosity of the electrolytic solution can be reduced. On the other hand, as the halogen element, fluorine, chlorine, bromine and the like are preferably mentioned. 1 ^ to 1 ³ may be the same type of substituents, may be some of them are different types of substituents.

Here, 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 methoxetoxy group and a methoxetoxetoxy group. Among them, R ¹ ! ^ ³ is preferably a methoxy group, an ethoxy group, a methoxyethoxy group, or a methoxyethoxy group, all of which are preferable from the viewpoint of low viscosity and high dielectric constant. Particularly preferred is a methoxy or 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. Examples of the acyl group include a formyl group, an acetyl group, a propionyl group, a butyryl group, an isopropylinole group, and a valeryl group. Examples of aryl groups include a fuel group, a tolyl group, and a naphthyl group. The hydrogen element in these monovalent substituents is preferably substituted with a halogen element, and as the halogen element, fluorine, chlorine, and bromine are preferable. Among them, fluorine is particularly preferable, and then chlorine is preferable. Those in which the hydrogen element in the monovalent substituent is replaced by fluorine tend to have a greater effect of improving the cycle characteristics of the capa than those in which the hydrogen element is replaced by chlorine.

In the formula (I), examples of the divalent linking group represented by Y ² and ³ include, in addition to CH ₂ group, oxygen, sulfur, selenium, nitrogen, boron, aluminum, scandium, gallium, and yttrium. , Indium, lanthanum, thallium, carbon, silicon, titanium, tin, gemium, dinoreconium, mouth, phosphorus, vanadium, arsenic, osonn

Divalent linking groups containing at least one element selected from the group consisting of copper, antimony, tantalum, bismuth, chromium, molybdenum, tellurium, holmium, tungsten, iron, cobalt, and nickel. Of these, a CH ₂ group and a divalent linking group containing at least one element selected from the group consisting of oxygen, sulfur, selenium, and nitrogen are preferable, and a divalent linking group containing an element of sulfur and Z or selenium is preferable. Are particularly preferred. Further, Y ² and ³ may be a divalent element such as oxygen, sulfur, selenium, or a single bond.丫¹ ~? All ³ may be of the same type, or some may be of different types.

In the formula (I), X ¹ represents at least one element selected from the group consisting of carbon, silicon, nitrogen, phosphorus, oxygen, and sulfur from the viewpoint of harmfulness and environmental considerations. Substituents containing species are preferred. Among these substituents, a substituent having a structure represented by the following formula (ΠΙ), (IV) or (V) is more preferable.

Y ⁵ R ⁵

 1 p 2 z (m)

Y ⁶ R ⁶

Y ⁷ R ⁷

—… (V)

但し、 式 (111)、 (IV)ヽ (V)において、 R⁵~R⁹は、 独立に一価の置換基又はノ、 ロゲン元素を表す。 Y⁵〜Y⁹は、 独立に 2価の連結基、 2価の元素、 又は単結合 を表し、 Zは 2価の基又は 2価の元素を表す。

However, in the formulas (111) and (IV) ヽ (V), R ⁵ to R ⁹ independently represent a monovalent substituent or a rho element. Y ^{5 to} Y ⁹ are independently a divalent linking group, a divalent element, or a single bond And Z represents a divalent group or a divalent element.

In the formulas (111) and (IV) ヽ (V), as R ^{5 to} R ⁹ , any of the same monovalent substituents or halogen elements as described with respect to ^ in the formula (I) are preferable. No. Further, these may be of the same type within the same substituent, or may be of different types. R ⁵ and R ^{6 in} the formula (III) and R ⁸ and R ^{9 in} the formula (V) may be bonded to each other to form a ring.

In the formulas (111), (IV) and (V), the group represented by Y ^{5 to} Y ⁹ may be the same divalent linking group or divalent group as described for γ ³ in the formula (I). Similarly, a group containing an element of sulfur, Ζ, or selenium is particularly preferable because the risk of ignition and ignition of the electrolytic solution is reduced. These may be of the same type within the same substituent, or may be of different types.

In the formula (III), Ζ 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), an NR group, oxygen, sulfur, and the like. , Selenium, boron, anoremium, scandium, gallium, yttrium, indium, lanthanum, thallium, carbon, silicon, titanium, tin, tin, germanium, dinoreconium, mouth, phosphorus, vanadium, arsenic, niobium, antimony, tantalum, bismuth, bismuth , Moripuden, Tenorenore, polonium, tungsten, iron, edge Noreto, and a divalent group containing at least one element selected from the group consisting of nickel. among them, CH ₂ group, CHR group, NR group And a divalent group containing at least one element selected from the group consisting of oxygen, sulfur, and selenium Masui. In particular, a divalent group containing elements of sulfur and Z or selenium is preferable because the risk of ignition of the electrolyte solution I is reduced. Z may be a divalent element such as oxygen, sulfur, and selenium.

As these substituents, a phosphorus-containing substituent represented by the formula (III) is particularly preferable in that the risk of ignition and ignition can be reduced particularly effectively. In addition, when the substituent is a sulfur-containing substituent represented by the formula (IV), the electrolyte has a small interface resistance. 4950

It is particularly preferable in view of the above.

In the formula (II), 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, an acyl group, an aryl group, and the like. Among these, an anolexoxy group is preferable in that the viscosity of the electrolytic solution can be reduced. On the other hand, preferred examples of the halogen element include fluorine, chlorine, and bromine. Examples of the alkoxy group include a methoxy group, an ethoxy group, a methoxetoxy group, a propoxy group, a phenoxy group and the like. Among them, a methoxy group, an ethoxy group, a methoxyethoxy group and a phenoxy group are particularly preferable. The hydrogen element in these monovalent substituents is preferably substituted with a halogen element. Examples of the halogen element include fluorine, chlorine, and bromine, and the substituent substituted with a fluorine atom is preferred. Examples thereof include a trifluoroethoxy group.

~ In formula (I) ~ (V), Υ ^ Υ 3 Υ 5 ~Υ 9, Ri by the appropriate selection of the Zeta, preparation of the electrolyte solution having a more preferable viscosity, additives' suitable for mixing and dissolving, etc. Is possible. These phosphazene compounds may be used alone or in a combination of two or more.

Among the phosphazene compounds of the formula (II), from the viewpoint of improving the low-temperature characteristics of the capacitor by lowering the viscosity of the electrolytic solution, and further improving the deterioration resistance and safety of the electrolytic solution, the following formula (VI) is used. Phosphazene compounds are preferred. (NPF ₂ ) _n ■ ■ '' (VI) (where n represents 3 to 13)

The phosphazene compound represented by the formula (VI) is a low-viscosity liquid at room temperature (25 ° C.) and has a freezing point depressing action. Therefore, by adding the phosphazene compound to the electrolytic solution, it is possible to impart excellent low-temperature characteristics to the electrolytic solution, and a low viscosity of the electrolytic solution is achieved, and low internal resistance and high conductivity Non-aqueous electrolyte An air double layer capacitor can be provided. For this reason, it is possible to provide a non-aqueous electrolyte electric double layer capacitor exhibiting excellent discharge characteristics over a long period of time even when used under low temperature conditions, particularly in low temperature areas and at low temperatures.

 In the formula (VI), n is preferably from 3 to 5, more preferably from 3 to 4, because it can impart excellent low-temperature properties to the electrolytic solution and can reduce the viscosity of the electrolytic solution. It is good. When the value of n is small, the boiling point is low, and the ignition prevention characteristics at the time of flame contact can be improved. On the other hand, as the value of n increases, the boiling point increases, so that it can be used stably even at high temperatures. It is also possible to select and use multiple phosphazenes in a timely manner to obtain the desired performance using the above properties.

 By appropriately selecting the value of n in the formula (VI), it becomes possible to prepare an electrolyte having more favorable viscosity, solubility suitable for mixing, low-temperature characteristics, and the like. These phosphazene compounds may be used alone or in a combination of two or more.

 The viscosity of the phosphazene compound represented by the formula (VI) is not particularly limited as long as it is 20 raPa-s (20 cP) or less, but from the viewpoint of improving conductivity and improving low-temperature characteristics, lOmPa's ( lOcP) or less, and more preferably 5 mPa's (5cP) or less.

 Among the phosphazene compounds of the formula (II), a phosphazene compound represented by the following formula (VII) is preferable from the viewpoint of improving the deterioration resistance and safety of the electrolyte.

(NPR ¹⁰ ₂ ) _n . ■ '(VII)

(Wherein, R ^w are independently a substituent or fluorine monovalent, both Tsu one less of the total R ^ie is a substituent group or a fluorine containing monovalent fluorine, n represents a 3 to 8 However, not all R ¹⁰ is fluorine.)

When the phosphazene compound of the above formula (II) is contained, the phosphazene compound is given by a formula (VII) that can impart excellent self-extinguishing properties or flame retardancy to the electrolyte to improve the safety of the electrolyte. All R ¹ . If at least one of these contains a phosphazene compound that is a monovalent substituent containing fluorine, it is possible to impart more excellent safety to the electrolytic solution. You. Furthermore, represented by the formula (VII), all R ¹ . If at least one of them contains a phosphazene compound in which at least one of them is fluorine, it is possible to impart even more excellent safety. That is, compared to a phosphazene compound containing no fluorine, the phosphazene compound represented by the formula (VII), wherein at least one of all R ¹⁰ is a monovalent substituent containing fluorine or fluorine, the electrolytic solution is It has the effect of making it more difficult to burn, and can provide more excellent safety to the electrolyte.

In the formula (VII), all R ¹ . Is a non-flammable compound, and the effect of preventing ignition when a flame approaches is large, but since the boiling point is extremely low, they are If it volatilizes, the remaining aprotic organic solvent will burn.

 Examples of the monovalent substituent in the formula (VII) include an alkoxy group, an alkyl group, an acyl group, an aryl group, a carboxyl group, and the like.The alkoxy group is particularly excellent in improving the safety of the electrolytic solution. Groups are preferred. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, a butoxy group, and an alkoxy-substituted alkoxy group such as a methoxyethoxy group. A methoxy group, an ethoxy group, and an n-propoxy group are particularly preferred in that they are excellent in improving the performance. Further, a methoxy group is preferable from the viewpoint of reducing the viscosity of the electrolytic solution.

 In the formula (VII), η is 3 to 3 in that it can impart excellent safety to the electrolytic solution.

5 is preferred, and 3-4 are more preferred.

The monovalent substituent is preferably substituted with fluorine. When R ^{w in} the formula (VII) is not fluorine, at least one monovalent substituent contains fluorine. The content of the fluorine in the phosphazene compound is preferably from 3 to 70% by weight, and more preferably from 7 to 45% by weight. When the content is within the above range, excellent safety can be particularly preferably imparted to the electrolytic solution.

The molecular structure of the phosphazene compound represented by the formula (VII) may contain halogen elements such as chlorine and bromine in addition to the above-mentioned fluorine. However, fluorine is the most preferred And then chlorine is preferred. Those containing fluorine tend to have a greater effect of improving the cycle characteristics of the capaci- tor than those containing chlorine.

By appropriately selecting the values of R ¹⁰ and 11 in the formula (VII), it becomes possible to prepare an electrolyte having more suitable safety, viscosity, solubility suitable for mixing, and the like. These phosphazene compounds may be used alone or in a combination of two or more. The viscosity of the phosphazene compound represented by the formula (VII) is not particularly limited as long as it is 20 mPa's (20 cP) or less, but from the viewpoint of improving conductivity and low-temperature characteristics, (10 cP) or less, more preferably 5 mPa's (5 cP) or less.

 Among the phosphazene compounds of the formula (II), from the viewpoint of improving the deterioration resistance and safety of the electrolytic solution while suppressing the increase in the viscosity of the electrolytic solution, it is a solid at 25 ° C. (room temperature), A phosphazene compound represented by the following formula (VIII) is also preferable.

(NPR ^u ₂ ) _n · ■ ■ (VIII)

(Wherein, R ¹¹ each independently represents a monovalent substituent or a halogen element; n represents 3 to 6.)

 Since the phosphazenic compound represented by the formula (VIII) is a solid at room temperature (25 ° C.), when added to the electrolyte, it dissolves in the electrolyte and increases the viscosity of the electrolyte. However, if the addition amount is a predetermined amount, a non-aqueous electrolyte electric double layer capacitor having a low rate of increase in viscosity of the electrolyte, a low internal resistance and a high conductivity is obtained. In addition, since the phosphazene compound represented by the formula (VIII) dissolves in the electrolyte, the electrolyte has excellent long-term stability.

In the formula (VIII), R ¹¹ 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 carboxy group, an acyl group and an aryl group. And the like. Further, as the halogen element, for example, a halogen element such as fluorine, chlorine, bromine, and iodine is preferably exemplified. Among these, an alkoxy group is particularly preferred in that the increase in the viscosity of the electrolytic solution can be suppressed. Examples of the alkoxy group include a methoxy group, an ethoxy group, a methoxyethoxy group, Poxy group (isopropoxy group, n-propoxy group), phenoxy group, trifluorophenol ethoxy group, etc. are preferable, and methoxy group, ethoxy group, propoxy group (isopropoxy group, _n -Propoxy group), phenoxy group, trifluoroethoxy group and the like. The monovalent substituent preferably contains the halogen element described above.

 In the formula (VIII), 11 is particularly preferably 3 or 4, since the increase in the viscosity of the electrolytic solution can be suppressed.

Wherein the phosphazene compound represented by (VIII), for example, the formula structure R ¹¹ to have contact in (VIII) is a methoxy group and n is 3, R ¹¹ turtles butoxy group in the formula (VIII) A structure in which n is 4 in at least one of a phenyl group and a phenoxy group; a structure in which R ¹¹ is an ethoxy group in the formula (VIII) and n is 4; and a structure in which R ^{11 is} an isopropoxy group in the formula (VIII). Wherein _n is 3 or 4; R ¹¹ in the formula (VII I) is an n-propoxy group; and n is 4; R ¹¹ is a trifluoroethoxy group in the formula (VIII). A structure in which n is 3 or 4 and a structure in which R ¹¹ in the formula (VIII) is a phenoxy group and n is 3 or 4 are particularly preferred in that the increase in the viscosity of the electrolytic solution can be suppressed.

 By appropriately selecting the substituents and the n value in the formula (VIII), it becomes possible to prepare an electrolyte having more suitable viscosity, solubility suitable for mixing, and the like. These phosphazene compounds may be used alone or in a combination of two or more. Specific examples of the isomer of the phosphazene compound include a compound represented by the following formula (IX). The compound of the formula (IX) is an isomer of the phosphazene compound represented by the following formula (X).

0 R ¹⁴

R ¹² Y ¹² — P— N— X ² · '· (K)

Y ¹³ R ¹³ 04 004950

OR ¹⁴

R ¹² Y ¹² — P = N— X ² … (X)

_Y 13 _R 13

(In the formulas (IX) and (X), R ¹² , R ¹³ and R ¹⁴ each independently represent a monovalent substituent or a halogen element; X ² represents carbon, silicon, germanium, tin, nitrogen , Phosphorus, arsenic, antimony, bismuth, oxygen, sulfur, selenium, tellurium and porodium represent a substituent containing at least one element selected from the group consisting of: Y ¹² and Y ¹³ each independently represent a divalent Represents a linking group, a divalent element or a single bond.)

R ¹² , R ¹³ and R ¹⁴ in the formula (IX) are not particularly limited as long as they are a monovalent substituent or a halogen element, and are the same as those described in the above formula (I) for scale ¹ to! ^. Preferred are both monovalent substituents and halogen elements. In the formula (II), as the divalent linking group or the divalent element represented by Y ¹² and Y ¹³ , the same divalent group as described for Y ¹ to Y ³ in the formula (I) is used. A linking group, a divalent element, and the like are all preferably exemplified. Further, in the formula (IX), as the substituent represented by X ² , any of the same substituents as described for X ¹ in the formula (I) are preferably exemplified.

 The isomer of the phosphazene compound represented by the formula (IX) and the formula (X) can exert extremely excellent low-temperature characteristics on the electrolytic solution when added to the electrolytic solution. The deterioration resistance and safety of the liquid can be improved.

 The isomer represented by the formula (IX) is an isomer of the phosphazene compound represented by the formula (X), for example, the degree of vacuum and / or Alternatively, it can be produced by adjusting the temperature, and the content (% by volume) of the isomer can be measured by the following measuring method.

 [Measuring method]

The peak area of the sample is determined by gel permeation chromatography (GPC) or high performance liquid chromatography, and the peak area is determined beforehand. The molar ratio can be obtained by comparing with the area per mole of the isomer, and it can be measured by converting the volume in consideration of the specific gravity.

 Specific examples of the phosphoric acid ester include alkyl phosphates such as trifenyl phosphate, tritaresyl phosphate, tris (fluoroethyl) phosphate, tris (tripentolene neopentinole) phosphate, and anorecoxy phosphate. And their derivatives.

 The supporting salt to be contained in the non-aqueous electrolyte of the present invention can be selected from conventionally known ones, but a quaternary ammonium salt is preferred in terms of good electric conductivity in the electrolyte. The quaternary ammonium salt is a solute that plays a role as an ion source for forming an electric double layer in the electrolyte, and effectively improves the electrical properties of the electrolyte such as electrical conductivity. A quaternary ammonium salt capable of forming a polyvalent ion is preferable from the viewpoint of being capable of forming a polyvalent ion.

Examples of the quaternary ammonium salts include (CH ₃ ) ₄ N-BF ₄ , (CH ₃ ) ₃ C ₂ H ₅ N-BF ₄ , and (CH ₃ ) ₂ (C ₂ H ₅ ) ₂ N · BF ₄ , CH ₃ (C ₂ H ₅ ) ₃ NBF ₄ , (C ₂ H ₅ ) ₄ NBF ₄ , (C ₃ H ₇ ) ₄ N ■ BF ₄ , CH ₃ (C ₄ H ₉ ) ₃ N ■ BF ₄ , (C ₄ H ₉ ) ₄ N ■ BF ₄ , (C ₆ H ₁₃ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ NC 10 ₄ , (C ₂ H ₅ ) ₄ N _{s F 6, (C 2 H} 5) 4 N ■ S b F 6, (C 2 Η 5) 4 Ν · CF 3 S_〇 _{3, (C 2 H 5)} 4 N. C 4 F 9 S0 3, ( C ₂ H ₅ ) ₄ N (CF ₃ S 0 ₂ ) ₂ N, (C ₂ Η ₅ ) ₄ Ν BCH ₃ (C ₂ H ₅ ) ₃ , (C ₂ H ₅ ) ₄ N 'B (C _{2 H 5) 4, (C 2} H 5) 4 N ■ B (C 4 H 9) 4, (C 2 H 5) 4 N · B (C 6 H 5) 4 and the like are preferably exemplified. Further, the anion portion of these quaternary Anmoniumu salts (e.g., ■ BF _4, ■ C 1_Rei _4, · A s F _6, etc.), preferred Kisafuruororin salt to replaced by ■ PF _6. Among these, a quaternary ammonium salt in which a different alkyl group is bonded to an N atom is preferable because the solubility can be improved by increasing the polarizability. Further, as the quaternary ammonium salt, for example, compounds represented by the following formulas (a) to (j) are also preferably exemplified. Here, in the formulas (a) to (j), Me represents a methyl group and Et represents an ethyl group. C No Me

N BF ₄ (a)

 ヽ Me

C no Me

N BF ₄ (b)

ゝ t BF ₄ (c)

C no Me

N BF ₄ (d)

C no Me

^ BF ₄ (e)

(BF ₄ (f)

し BF₄ (h)

BF ₄ (h)

“ヽ N BF ₄ (j) Among these quaternary ammonium salts, it is particularly important to ensure high electrical conductivity. 04950

Are preferably salts capable of generating (CH ₃ ) ₄ N ⁺ , (C ₂ H ₅ ) ₄ N ^{+ and the} like as cations. 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 nonaqueous electrolytic solution of the present invention can reduce the viscosity of the electrolytic solution in addition to the above-described compound containing at least one of phosphorus and nitrogen in the molecule and the supporting salt, and can be easily used as an electric double layer capacitor. It is preferable to contain a non-protonic organic solvent in that an optimum ionic conductivity can be achieved. The aprotic organic solvent is not particularly limited, and examples thereof include a nitrile compound, an ether compound, and an ester compound. Specifically, nitrile compounds such as acetonitrile, propiono-tolyl, ptyronitrile, isobutyronitrile, and benzonitrile; ether compounds such as 1,2-dimethoxetane and tetrahydrofuran; dimethyl carbonate, dimethylol carbonate, Preferable examples include carbonic acid ester compounds such as ethynolemethinolecarbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, γ-petit mouth rattan, and γ-valero ratatone. Among them, cyclic ester compounds such as ethylene carbonate, propylene carbonate, and γ-petit mouth ratataton; chain carbonate compounds such as dimethyl carbonate, ethynole carbonate, and ethyl methionyl carbonate; Chain ether compounds such as -dimethoxyethane are preferred. The cyclic carbonate compound has a high relative dielectric constant and is excellent in dissolving ability of the supporting salt, and the chain carbonate compound and the ether compound have a low viscosity to reduce the viscosity of the electrolytic solution. Is preferred. These may be used alone or in combination of two or more.

The concentration of the supporting salt in the electrolyte is preferably from 0.2 to 2.5 mol / L (M), more preferably from 0.8 to 1.5 raol / L (M). If the concentration of the supporting salt is less than 0.2 mol / L (M), it may not be possible to secure sufficient electrical properties such as the electrical conductivity of the electrolyte, but it may exceed 2.5 mol / L (M). In such a case, the viscosity of the electrolytic solution may increase, and electrical characteristics such as electrical conductivity may decrease. The content of the compound containing at least one of phosphorus and nitrogen in the molecule in the nonaqueous electrolyte of the present invention is preferably 0.1% by volume or more from the viewpoint of improving the permeability of the electrolyte to the electrode. It is preferably at least 0.5% by volume. Further, from the viewpoint of improving the safety of the electrolytic solution, it is preferably at least 3% by volume, more preferably at least 5% by volume. <Non-aqueous electrolyte electric double layer capacitor>

 Next, the non-aqueous electrolyte electric double layer capacitor of the present invention will be described in detail. The non-aqueous electrolyte electric double layer capacitor of the present invention includes the above-described non-aqueous electrolyte, a positive electrode, and a negative electrode, and is usually used in the technical field of an electric double layer capacitor such as a separator, if necessary. Having a member.

 The positive electrode and the negative electrode of the nonaqueous electrolyte electric double layer capacitor of the present invention are not particularly limited, but usually a porous carbon-based polarizable electrode is preferable. As the electrode, those having characteristics such as a large specific surface area and a large specific gravity, being electrochemically inert, and having low resistance are preferable. Activated carbon etc. are mentioned as said porous carbon. The above-mentioned electrode generally contains porous carbon such as activated carbon, and, if necessary, other components such as a conductive agent and a binder. The raw material of the activated carbon that can be suitably used for the electrode is not particularly limited, and examples thereof include various heat-resistant resins and pitches in addition to phenol resin. Examples of the heat-resistant resin include polyimide, polyamide, polyamideimide, polyetherimide, polyethersulfone, polyetherketone, bismaleimidtriazine, aramide, fluorine resin, polyphenylene, and polyphenylene sulfide. Resins are preferred. These may be used alone or in combination of two or more. The activated carbon 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 non-aqueous electric liquid / electric double layer capacitor. Further, these activated carbons may be subjected to a treatment such as heat treatment, stretch molding, vacuum high-temperature treatment, and rolling in order to further increase the charge capacity of the electric double layer capacitor.

The conductive agent used for the above electrodes is not particularly limited, but may be graphite, acetylene bran, or the like. And the like. The binder used for the above electrode is not particularly limited, but polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC ).

The non-aqueous electrolyte electric double layer capacitor of the present invention preferably includes a separator, a current collector, a container, and the like in addition to the above-described positive electrode, negative electrode, and electrolytic solution. Can be provided. Here, the separator is interposed between the positive and negative electrodes for the purpose of preventing short circuit of the non-aqueous electrolyte electric double layer capacitor and the like. The separator is not particularly limited, and a known separator usually used as a separator for a non-aqueous electrolyte electric double layer capacitor is preferably used. Preferred examples of the material of the separator include a microporous film, a nonwoven fabric, and paper. Specifically, a nonwoven fabric and a thin film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, and polyethylene are preferably used. Among them, a microporous film having a thickness of about _20~50 μ ιη polypropylene or made of poly ethylene is particularly preferred.

 The current collector is not particularly limited, and a known current collector 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, current collector layers of aluminum, stainless steel, conductive resin, etc. Is preferred.

 There is no particular limitation on the container, and a well-known container usually used as a container for a nonaqueous electrolyte electric double layer capacitor can be preferably used. As the material of the container, for example, aluminum, stainless steel, conductive resin and the like are suitable.

The form of the non-aqueous electrolyte electric double layer capacitor of the present invention is not particularly limited, and well-known forms such as a cylinder type (cylindrical type, square type) and a flat type (coin type) are preferably exemplified. These non-aqueous electrolyte electric double layer capacitors, for example, For memory backup of equipment, industrial equipment, aviation equipment, etc., for electromagnetic hold of toys, cordless equipment, gas equipment, instantaneous water heaters, etc., and for watches such as watches, wall clocks, solar clocks, AGS watches, etc. It is preferably used as a power supply for the above.

 Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

<Example>

 (Example 1)

Activated carbon (AC, trade name: Kuractive- 1500, manufactured by Kuraray Chemical Co., Ltd.), acetylene black (conductive agent), and poly (vinylidene fluoride) (PVDF) (binder) were mass ratio (active carbon: acetylene black) : PVDF) to give a mixture of 8: 1: 1 to obtain a mixture. 100 mg of the resulting mixture was collected, placed in a 20-φ pressure-resistant mono-bon container and compacted under a pressure of 150 kgfm ² at room temperature to produce a positive electrode and a negative electrode (electrode).

Also, 90% by volume of propylene carbonate (PC) (aprotic organic solvent) contains cyclic phosphazene A (in the formula (II), n is 3 and one of six R ⁴ is a phenoxy group (PhO_), 5 is a cyclic phosphazene compound is a fluorine, viscosity definitive to 25 ° C: 1.7mPa's (l.7cP )) 10 volume _^0/0 was added tetraethyl ammonium Niu arm Tet rough Ruo Robo rate _{(TEATFB, (C Z H 5} ) 4 N-BF ₄ ) (supporting salt) was dissolved at a concentration of lmol / L (M) to prepare an electrolytic solution.

Was added dropwise to the electrolyte solution 5 mu L to the electrode at room temperature, the manner in which the electrolytic solution to penetrate into the electrode was monitored by resolution 360 frames _/ / sec CCD camera, the contact angle with the electrolyte droplet and the electrode Was measured. The contact angle was measured using an automatic contact angle measuring device OCA 20 manufactured by dataphysics. Figure 2 shows the change over time of the contact angle of the electrolyte with the electrode. As a result, the time required for the contact angle of the electrolyte to the electrode to become 2 ° or less was less than 0.1 second.

In addition, the safety of the above-mentioned electrolytes is regulated by UL (Underwriting Laboratory). It was evaluated based on the combustion behavior of a flame ignited under atmospheric conditions using a method adapted from the rated UL94 HB method. At that time, ignitability, flammability, carbide formation, and the phenomenon during secondary ignition were also observed. Specifically, based on UL test standards, a non-combustible quartz fiber was impregnated with 1. OmL of the above electrolyte to prepare a 127 mm x 12.7 mm test piece. Here, the case where the test flame does not ignite the test piece (combustion length: 0 mm) is “non-flammable”, and the case where the ignited flame does not reach the 25 瞧 line and the falling object does not ignite. `` Self-extinguishing '' means `` flame-retardant '', when the ignited flame extinguishes on the 25 to 100 mm line and no ignition is found on the falling object, `` self-extinguishing '' means when the ignited flame exceeds 100 mm It was evaluated as "flammability". Table 1 shows the results.

Next, the electrode (positive electrode and negative electrode), Arumiyuumu metal plate (collector) (thickness: 0. 5mra): assembled and the cell using a polypropylene Z polyethylene plate _(separator) (25 μ ηι thickness) Fully dried by vacuum drying. The cell was impregnated with the electrolytic solution to prepare a non-aqueous electrolytic solution electric double layer capacitor. After discharging and discharging the obtained capacitor for -10000 cycles, the discharge capacity (Α) at the time of 2 C rate discharge (the condition where the whole capacity is discharged in 30 minutes) and the 0.2 C rate discharge (5 hours) The discharge capacity (Β) was measured under the condition that the entire capacity was discharged in step (1). The 2 C capacity (%) after 10,000 cycles was calculated from these measured values and the following formula, and the results shown in Table 1 were obtained.

 Formula: 2 C capacity = ΑΖΒ Χ 100 (%)

 (Examples 2 to 18 and Comparative Examples 1 to 3)

 An electrolytic solution having the formulation shown in Table 1 was prepared, and the permeability and safety of the electrolytic solution to the electrode were evaluated in the same manner as in Example 1. Table 1 shows the results. FIG. 2 shows the change over time of the contact angle of the electrolyte of Comparative Example 1 with the electrode. In Table 1, GB L indicates γ _ petite mouth ratatone, and AN indicates acetonitrile.

In Table 1, cyclic phosphazene B is a compound of the formula (II) wherein n is 3, one of six R ⁴ is an ethoxy group, and five are fluorine (viscosity at 25 ° C .: 1.2 mPa-s (1.2 cP)); the cyclic phosphazene C is represented by the formula (II) wherein n is 4 A compound in which one of eight R ⁴ is an ethoxy group and seven are fluorine (viscosity at 25 ° C .: 1. lniPa-s (l. LcP)); cyclic phosphazene D is represented by the formula (II ) smell Te, n is 3, six 1 Tsugame Toki Chez Toki Chez Toki Chez butoxy group of _{^{R 4 (CH 3 OC 2 H}} 4 OC 2 H 4 OC 2 H 4 0-), five thereof are fluorine A compound (viscosity at 25 ° C: 4.5 mPa-s (4.5 cP)).

Further, the chain phosphazene E is a compound represented by the formula (I), wherein X ¹ is a substituent represented by the formula (III), and Y ¹ , Y ² R ² , Y ³ R ³ , Y ⁵ R ⁵ and Y ⁶ R ⁶ is a compound in which three are ethoxy groups, two are fluorine, and Z is 〇 (oxygen) (viscosity at 25 ° C .: 4.7 mPa's (4.7 cP));

The chain phosphazene F is a compound represented by the following formula (XI) (viscosity at ²⁵ ° C .: 4.9 mPa-s (4.9 cP));

The chain phosphazene G is a compound represented by the following formula (XII) (viscosity at 25 ° C .: 2.8 mPa-s (2.8 cP));

F 0

 I II

F-P = N-S — CH ₃ · · · (ΧΠ)

 II

The chain phosphazene H is a compound represented by the following formula (XIII) (viscosity at 25 ° C .: 3.9 mPa-s (3.9 cP)). F CH ₂ C00CH ₃

F—P = W—P = 0 °°. (2)

 I I

F F

 Further, the phosphate ester X is a compound represented by the following formula (XIV) (viscosity at 25 ° C .: 0.5 raPa-s (2.5 cP)).

0

 II

P-1 0C ₂ H ₅

 / \

 F F Further, phosphazane Y is a compound represented by the following formula (XV) (viscosity at 25 ° C .: 5.0 mPa-s (5. OcP)).

トリアジン Zは、 下記式 (XVI)で表される化合物 (25°Cにおける粘度： 2. IraPa- s(2. lcP)) である

Triazine Z is a compound represented by the following formula (XVI) (viscosity at 25 ° C .: 2. IraPa-s (2.lcP))

 (XVI)

 N N

 c

F In addition, a nonaqueous electrolyte Was prepared, and the 2 C capacity after 100 cycles was measured. Table 1 shows the results.

From Table 1, the contact angle of the non-aqueous electrolyte with the electrode after dropping on the capacitor electrode In the capacitor using the non-aqueous electrolyte in which the time until the temperature becomes 2 ° or less is less than 0.5 seconds, the voltage drop between the electrolyte and the electrode is small, so that the capacitor after 20000 cycles is not used. The capacity was large and the high current discharge characteristics were excellent. On the other hand, the comparative capacitor using the conventional non-aqueous electrolyte had a large voltage drop between the electrolyte and the electrode, so the 2C capacity after 10,000 cycles was small, and the large-current discharge characteristics were inferior. . Industrial applicability

 According to the present invention, it is possible to provide a non-aqueous electrolyte for an electric double layer capacitor which has excellent permeability to an electrode for an electric double layer capacitor and can reduce the internal resistance of the capacitor. Further, since the non-aqueous electrolyte is provided and the internal resistance is small, it is possible to provide a non-aqueous electrolyte electric double layer capacitor excellent in pulse discharge characteristics ゃ large current discharge and charging characteristics.

Claims

The scope of the claims 1. After the non-aqueous electrolyte is dropped on the electrode for electric double layer capacitor, the time required for the contact angle of the non-aqueous electrolyte to the electrode to become 2 ° or less is less than 0.5 seconds. Non-aqueous electrolyte.  2. The non-aqueous electrolyte according to claim 1, wherein the active material of the electrode is porous carbon.  3. The non-aqueous electrolyte according to claim 2, wherein the porous carbon is activated carbon.  4. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte contains a compound having phosphorus in a molecule.  5. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte contains a compound having nitrogen in a molecule. 16. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous electrolyte contains a compound having phosphorus and nitrogen in a molecule.  7. The non-aqueous electrolyte according to claim 6, wherein the compound having phosphorus and nitrogen in the molecule has a phosphorus-nitrogen double bond.  8. The non-aqueous electrolyte according to any one of claims 6 to 6, wherein the non-aqueous electrolyte further contains an aprotic organic solvent.  9. A nonaqueous electrolyte electric double layer capacitor comprising the nonaqueous electrolyte according to any one of claims 1 to 8, a positive electrode, and a negative electrode.