JP2009065074A - Electrolyte for pseudocapacitor, and pseudocapacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for a pseudocapacitor that has a superior impregnation properties to an electrode and a separator, shows a low viscosity coefficient, high electric conductivity, and a wide potential window, and has excellent electrochemical stability, and to provide the pseudocapacitor that has high capacity, low internal resistance, a small leakage current, superior breakdown voltage characteristics and superior reflow characteristics by using the electrolyte. <P>SOLUTION: As the electrolyte for the pseudocapacitor prepared by incorporating an electrolyte and an additive in a solvent, an electrolyte containing a siloxane derivative as the additive is used for the pseudocapacitor. Consequently, the impregnation properties to the electrode and separator is improved, and then the obtained pseudocapacitor has larger capacity and lower internal resistance to have, especially, a smaller leakage current during voltage application and improved reflow characteristics. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an electrolytic solution for a pseudocapacitor, and more particularly, an electrolytic solution for a pseudocapacitor containing a specific additive, which is an electrolytic solution for a pseudocapacitor that has improved impregnation into a polarizable electrode sheet and a separator nonwoven fabric. The present invention relates to a liquid capacitor and a pseudocapacitor using the electrolytic solution, having a high capacity, a low internal resistance, and having excellent electrical characteristics.

  In recent years, pseudocapacitors have been attracting attention as next-generation power storage devices to replace electric double layer capacitors and lithium secondary batteries because of their high safety and high energy density. Research into the field of power electronics such as uninterruptible power supplies and auxiliary power supplies for electric vehicles is underway.

  The pseudocapacitor in the present invention is also called a redox capacitor, and utilizes an electrochemical reaction involving an Faraday current accompanying an oxidation-reduction reaction at an electrode interface and an electrochemical ion adsorption / desorption reaction at an electrode. More specifically, an electrode comprising an electrode active material such as a conductive metal oxide, a π-conjugated conductive polymer, a lithium ion intercalate compound, an ultrafine metal oxide, and an organic supramolecule in an electrode constituent material; An electrochemical capacitor comprising a liquid and a separator.

  In addition to improving energy density, pseudocapacitors are required to have improved cycle characteristics and low internal resistance to improve output density. Electrolytic solutions used in pseudocapacitors are electrochemically stable and have high electrical properties. Characteristics such as conductivity are required. In addition, low leakage current is required from the viewpoint of malfunction of digital equipment and low power consumption.

  In addition, pseudo capacitors are assumed to be used under harsh conditions, and as an electrolyte, characteristics that enable the pseudo capacitors to operate stably over a wide temperature range from low to high are also important. is there.

Electrolytic solutions used in conventional pseudocapacitors are roughly classified into aqueous electrolytic solutions and non-aqueous electrolytic solutions.
The aqueous electrolyte is generally an aqueous solution containing an inorganic acid, an organic acid or an alkali metal salt as an electrolyte, and the non-aqueous electrolyte is an aprotic organic solvent such as propylene carbonate, ethylene carbonate or vinylene carbonate, and an alkaline as an electrolyte. A solution in which a metal salt, a quaternary ammonium salt or a mixture thereof is dissolved is often used.

  The electrolytic solution is usually impregnated into the electrode by a step of repeating pressure reduction or pressurization or pressure reduction and pressurization by pouring the sheet-like electrode and separator containing the active material. However, when the electrolyte does not sufficiently reach the pores inside the electrode, or when an unimpregnated portion such as not sufficiently impregnated in the separator occurs, the capacity is reduced, the internal resistance is increased, and the current rate characteristics are deteriorated. In particular, the variation in capacitance and internal resistance after reflow increases, resulting in the disadvantage of being unstable.

  On the other hand, if the pressure is excessively reduced in the impregnation step for the purpose of improving the impregnation property, water used in the electrolyte or an aprotic organic solvent such as propylene carbonate or γ-butyrolactone evaporates and becomes an inorganic solute. The concentration of the salt or the aliphatic quaternary ammonium salt may change, and the electrical characteristics that can be originally expressed may be impaired.

  Therefore, there is a demand for an electrolyte solution that has superior impregnation into electrodes and separators and superior electrical characteristics than the conventionally known electrolyte solutions.

  There is known a method for improving various characteristics of an electrochemical capacitor such as an electric double layer capacitor by adding an additive to an electrolytic solution. For example, phosphazenes and their derivatives are listed as substances that have been proposed as additives for electrolytic solutions for electric double layer capacitors. (For example, see Patent Document 1 and Patent Document 2)

  However, the above phosphazenes and their derivatives are mainly aimed at imparting flame retardancy to electric double layer capacitors and improving characteristics at low temperatures, and the effects of improving the impregnation properties and reducing leakage current of pseudo capacitors are unknown. there were.

  By adding polyether-modified siloxane as an electrolyte solution additive for a negative electrode such as a lithium ion battery to Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, and Non-Patent Document 1, a conductive thin film on the negative electrode It is disclosed that the thin film suppresses the decomposition of the solvent and the electrolyte and improves the withstand voltage and the accompanying charge / discharge cycle characteristics.

  However, the charging / discharging mechanism and electrode reaction of the pseudocapacitor are different from those of the lithium ion battery, and the effect of adding the above additive to the electrolytic solution for the pseudocapacitor is unknown.

  Patent Document 7 discloses that the temperature characteristics and output characteristics are improved by adding a carbonate-modified silane and a siloxane-based silicon compound to an electrochemical capacitor such as a lithium ion battery or an electric double layer capacitor.

  However, the leakage current reduction effect, large current response, and capacitance development rate at low temperatures in a pseudo capacitor using the electrolytic solution are unknown.

  Patent Document 8 and Patent Document 9 disclose that excellent input / output characteristics and cycle characteristics can be obtained even when a cyclic siloxane is added and the size is increased as an additive for an electrolytic solution of a lithium secondary battery. .

  However, the charging / discharging mechanism and electrode reaction of the pseudocapacitor are different from those of the lithium secondary battery, and the effect of adding the above additive to the electrolytic solution for the electric double layer capacitor is unknown. In addition, the leakage current reduction effect, large current response, and capacitance development rate at low temperatures in a pseudo capacitor that actually uses the electrolyte are unknown.

International Publication No. WO2002 / 021631 Pamphlet JP 2001-217152 A Japanese Patent Laid-Open No. 11-214032 JP 2004-235141 A JP 2006-49266 A JP 2006-66095 A JP 2006-137741 A JP 2004-71458 A JP 2006-165301 A Takeshi Hirose, Satoru Tada, Naoyuki Yamada, Hideyuki Morimoto, Shinichi Kajishima, “The 46th Battery Discussion Meeting Proceedings”, November 16-18, 2005, p. 442

  The present invention provides an electrolytic solution for a pseudocapacitor that is excellent in impregnation into electrodes and separators, has a low viscosity, high electrical conductivity, a wide potential window, and is excellent in electrochemical stability. The object is to provide a pseudocapacitor having both high capacity, low internal resistance, low leakage current, excellent withstand voltage characteristics and excellent reflow characteristics.

  As a result of intensive studies in view of the above problems, the present inventors have used an electrolytic solution containing a siloxane derivative represented by the following formula as an additive for a pseudocapacitor. As a result, the capacitance of the obtained pseudo capacitor is increased, the internal resistance can be lowered, the leakage current during voltage application can be reduced, and the reflow characteristics can be improved, and the present invention has been completed.

  That is, the present invention provides an electrolytic solution for a pseudocapacitor in which an electrolyte and an additive are contained in a solvent, wherein the additive is a compound represented by the following general formula (1): It is a liquid.

  In the above formula (1), R1 to R6 each represents an organic group which may be the same or different, and those capable of bonding a substituent may be substituted. More preferably, the organic group is a hydrogen atom, halogen atom, chain alkyl group, chain ether group, cyclic alkyl group, alkoxy group, benzylalkoxy group, phenylalkoxy group, phenyl group, benzyl group, amino group, epoxy. A group, a carboxyl group, a hydroxyl group, a styryl group, a fluorine-containing alkyl group, and an ester group, each of which can be bonded to a substituent, may be substituted. n represents an integer of 1 to 10.

  The present invention also provides an electrolytic solution for a pseudocapacitor comprising an electrolyte and an additive contained in a solvent, wherein the additive is a compound represented by the following general formula (2): It is a liquid.

  In the above formula (2), R7 and R8 each represents an organic group which may be the same or different, and those capable of binding a substituent may be substituted. More preferably, the organic group is a hydrogen atom, halogen atom, chain alkyl group, chain ether group, cyclic alkyl group, alkoxy group, benzylalkoxy group, phenylalkoxy group, phenyl group, benzyl group, amino group, epoxy. A group, a carboxyl group, a hydroxyl group, a styryl group, a fluorine-containing alkyl group, and an ester group, each of which can be bonded to a substituent, may be substituted. n represents an integer of 2 or more and 10 or less.

  The present invention also provides an electrolytic solution for a pseudocapacitor, wherein the content of the additive is 0.001 to 10% by weight.

  Furthermore, the present invention is a pseudocapacitor obtained by impregnating a polarizable electrode sandwiching a separator with the above-described electrolyte solution and sealing it in a container.

  The electrolytic solution for pseudocapacitors of the present invention to which the above siloxane derivative is added exhibits high electrical conductivity, a wide potential window, and high electrochemical stability.

  By adding the above additives to the electrolyte, it improves the impregnation of the electrolyte into the sheet-like electrode and separator due to its action as a surfactant, and accordingly, increases the capacity, reduces internal resistance, and reduces leakage current. An effect and an effect of improving current rate characteristics can be obtained.

  In addition, there is a function of lowering the surface tension of the electrolytic solution, and the use of the electrolytic solution to which the above-mentioned additive is added provides an effect of improving handling due to an increase in the impregnation property of the electrode during the manufacturing process of the pseudocapacitor.

  Hereinafter, the electrolytic solution for pseudocapacitors of the present invention will be described in detail.

  The additive added to the electrolytic solution for pseudocapacitors of the present invention is a chain siloxane derivative represented by the following general formula (1). By adding the additive to the electrolytic solution for a pseudocapacitor containing an electrolyte in a solvent, the impregnation of the electrode and separator of the pseudocapacitor is improved, and exhibits a low viscosity and high electrical conductivity. In addition, an electrolytic solution having a wide potential window and high electrochemical stability can be obtained.

  In the above formula (1), R1 to R6 each represents an organic group which may be the same or different, more preferably a hydrogen atom, a halogen atom, a chain alkyl group, a chain ether group, a cyclic alkyl group, An alkoxy group, a benzylalkoxy group, a phenylalkoxy group, a phenyl group, a benzyl group, an amino group, an epoxy group, a carboxyl group, a hydroxyl group, a styryl group, a fluorine-containing alkyl group, or an ester group, each of which can be bonded to a substituent is substituted May be. N represents an integer of 1 to 10, more preferably 1 to 5. When n exceeds 10, the viscosity is remarkably increased, and it is difficult to dissolve in the electrolytic solution, or the characteristics of the capacitor deteriorate when dissolved in the electrolytic solution.

More preferable examples of the organic group represented by R1 to R6 include any one selected from the group consisting of a hydrogen atom, a saturated hydrocarbon group having 1 to 4 carbon atoms, and an unsaturated hydrocarbon group having 2 to 4 carbon atoms. is there.
Examples of the saturated hydrocarbon group having 1 to 4 carbon atoms include methyl group, ethyl group, propyl group, butyl group, 1-methylethyl group (i-propyl group), 1,1-dimethylethyl group (t-butyl group). ), 1-methylpropyl group (sec-butyl group).
Examples of the unsaturated hydrocarbon group having 2 to 4 carbon atoms include alkenyl groups such as vinyl group, 1-propenyl group, allyl group, isopropenyl group, 1-butenyl group and 2-butenyl group.

  The additive for the pseudocapacitor electrolyte of the present invention is at least one cyclic siloxane derivative represented by the following general formula (2).

  In the formula (2), R7 and R8 each represents an organic group which may be the same or different, more preferably a hydrogen atom, a halogen atom, a chain alkyl group, a chain ether group, a cyclic alkyl group, An alkoxy group, a benzylalkoxy group, a phenylalkoxy group, a phenyl group, a benzyl group, an amino group, an epoxy group, a carboxyl group, a hydroxyl group, a styryl group, a fluorine-containing alkyl group, or an ester group, each of which can be bonded to a substituent is substituted May be. N represents an integer of 2 to 10, more preferably 3 to 8. When n exceeds 10, the viscosity becomes remarkably high and does not dissolve in the electrolytic solution, or when dissolved in the electrolytic solution, the characteristics of the capacitor deteriorate.

  More preferable as the organic group is a chain alkyl group having 1 to 4 carbon atoms. Specifically, methyl group, ethyl group, propyl group, butyl group, 1-methylethyl group (i-propyl group), 1,1-dimethylethyl group (t-butyl group), 1-methylpropyl (sec-butyl) Group).

  Moreover, it is preferable that content of the polysiloxane derivative shown by the said General formula (1) or (2) is 0.001 to 10 weight%, More preferably, it is 0.01 to 1 weight%.

The electrolyte to be dissolved in the solvent is not particularly limited as long as it is an electrolyte capable of releasing lithium ions, and can be arbitrarily selected from conventionally known lithium salts. Specifically, as a cation, a lithium cation, and as an anion, ClO ₄ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , N (C ₂ F ₅ SO ₂ ) ₂ ^— , N (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) ⁻ , C (CF ₃ SO ₂ ) ₃ ^— and C (C ₂ F ₅ SO ₂ ) ₃ ^— It is preferable. In addition, 2 or more types of these anions may be mixed.

  Moreover, in order to improve the electrical conductivity of electrolyte solution with the said electrolyte, you may contain the electrolyte which consists of a quaternary ammonium salt. The quaternary ammonium salt can be arbitrarily selected from conventionally known quaternary ammonium salts, and is not particularly limited. Specifically, the cation includes a quaternary ammonium cation such as tetraethylammonium ion or triethylmethylammonium ion, a quaternary imidazolium cation such as 1-ethyl-3-methylimidazolium ion or diethylimidazolium ion, propyl It is preferably selected from the group consisting of quaternary pyridinium cations such as pyridinium ions and isopropylpyridinium ions, and pyrrolidinium cations such as spiro- (1,1 ′)-bipyrrolidinium ions. In addition, 2 or more types of these cations may be mixed. The anion is not particularly limited, but an anion composed only of a nonmetallic element is preferable.

  Examples of the solvent for the non-aqueous electrolyte include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone; dimethyl carbonate, diethyl carbonate Chain carbonates such as ethyl methyl carbonate; chain esters such as methyl formate, methyl acetate, methyl butyrate; tetrahydrofuran or derivatives thereof; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, Ethers such as 1,4-dibutoxyethane and methyldiglyme; Nitriles such as acetonitrile and benzonitrile; Dioxolane or derivatives thereof; Ethylene sulfide, sulfolane, sultone or derivatives thereof; 4 -Fluorine solvents such as ethylfluorobenzene and (trifluoromethyl) ethyl carbonate may be used alone or as a mixture of two or more thereof, but are not limited thereto.

  The electrolytic solution for pseudocapacitors of the present invention can be prepared by the following manufacturing method.

That is, an electrolyte salt composed of a lithium salt and optionally a quaternary ammonium salt is added to the solvent at an arbitrary concentration, and after stirring to confirm that the salt is completely dissolved, the siloxane derivative is used as an additive. Is preferably added in an amount of 0.001 to 10% by weight, more preferably 0.01 to 1% by weight. In the case of 0.01% by weight or less, the effect of lowering the surface tension due to the addition and the accompanying improvement in electrical conductivity and lowering the viscosity may not be exhibited. In the case of 10% by weight or more, the viscosity of the electrolyte The rate, electrical conductivity, and voltage holding characteristics may be extremely inferior, and the economy may be inferior.
In the case of adjusting the non-aqueous electrolyte solution, when the obtained electrolyte solution is dehydrated and the water in the electrolyte solution is reduced to 100 ppm or less, preferably 20 ppm or less, the target electrolyte solution for a pseudo capacitor is obtained.

  The concentration of the electrolyte salt in the electrolytic solution of the present invention is preferably 0.5 to 3 mol / L with respect to the entire electrolytic solution. If the concentration of the lithium salt is less than 0.5 mol / L, the electrical conductivity may be insufficient, and if it is more than 3 mol / L, the electrochemical stability may be lowered and the economy may be inferior.

  A pseudocapacitor can be produced using the electrolytic solution thus adjusted. The pseudocapacitor of the present invention can be manufactured by a general method of manufacturing a pseudocapacitor, that is, a pseudocapacitor in which a polarizable electrode sandwiching a separator contains the additive of the present invention as a driving electrolyte. It is carried out by impregnating with an electrolytic solution and sealing it in a container.

  There are no particular restrictions on the polarizable electrode used for the pseudocapacitor electrode, porous carbon materials such as activated carbon powder and activated carbon fiber, noble metal oxide materials, conductive polymer materials, lithium ion intercalating materials, organic super Molecular materials are used. Moreover, as a separator, the separator which consists of raw materials, such as polyethylene and a polypropylene-type nonwoven fabric, can be used.

  The shape of the pseudocapacitor of the present invention is not particularly limited, and the pseudocapacitor can be formed into a film shape, a coin shape, a cylindrical shape, a box shape or the like.

  FIG. 1 is a schematic cross-sectional view showing an example of a coin-type pseudocapacitor among the above shapes, and showing an example of the configuration of the pseudocapacitor of the present invention.

  In FIG. 1, it has a negative electrode part composed of a negative electrode cap 1, a negative electrode 2 and a current collector 3, and a positive electrode part composed of a current collector 3, a positive electrode 6 and a positive electrode case 7. It arrange | positions so that it may oppose. The electrolytic solution 4 is impregnated and filled in electrodes, separators, and containers. The negative electrode cap 1 and the positive electrode case 7 are insulated and fitted by a gasket 8.

  The pseudocapacitor of the present invention has a very high withstand voltage and exhibits stable charge / discharge characteristics in a range including at least 2.8V to 4.5V.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited at all by the Example.

Example 1
Preparation of electrolytic solution for pseudocapacitor LiPF ₆ was added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate was 1: 1 so that the concentration was 1.0 mol / L, and hexamethylcyclotrisiloxane (cyclic siloxane) Tokyo Chemical Industry Co., Ltd .: 0.1% by weight of a reagent, the following formula No. 1) was added and dehydrated to obtain an electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less (hereinafter referred to as this electrolytic solution and electrolysis). A pseudocapacitor using a liquid is referred to as “Invention 1”).

Similarly, LiPF ₆ is added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate is 1: 1 so that the concentration becomes 1.0 mol / L, and octamethylcyclotetrasiloxane (Tokyo Chemical Industry Co., Ltd.), which is a cyclic siloxane, is added. Company: Reagent, 0.1 wt% of the following formula No. 2) was added and dehydrated to obtain an electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less (same as above, “Invention 2”) .

Similarly, LiPF ₆ was added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate was 1: 1 so that the concentration was 1.0 mol / L, and decamethylcyclopentasiloxane (Tokyo Chemical Industry Co., Ltd.), which is a cyclic siloxane. Company: Reagent, 0.1 wt% of the following formula No. 3) was added and dehydrated to obtain an electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less (same as above, “Invention 3”) .

Similarly, LiPF ₆ was added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate was 1: 1 to a concentration of 1.0 mol / L, and hexamethyldisiloxane, a chain siloxane (Tokyo Chemical Industry Co., Ltd.). Company: Reagent, 0.1 wt% of the following formula No. 4) was added and dehydrated to obtain an electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less (same as above, “Invention 4”) .

Similarly, LiPF ₆ was added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate was 1: 1 so that the concentration was 1.0 mol / L, and octamethyltrisiloxane (Tokyo Chemical Industry Co., Ltd.), which is a chain siloxane. Company: Reagent, 0.1 wt% of the following formula No. 5) was added and dehydrated to obtain an electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less (same as above, “Invention 5”) .

Similarly, LiPF ₆ was added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate was 1: 1 so that the concentration was 1.0 mol / L, and decamethyltetrasiloxane (Tokyo Chemical Industry Co., Ltd.), which is a chain siloxane. Company: Reagent, 0.1 wt% of the following formula No. 6) was added and dehydrated to obtain an electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less (same as above, “Invention 6”) .

Similarly, LiPF ₆ is added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate is 1: 1 to a concentration of 1.0 mol / L, and spiro- ( 1,1) -bipyrrolidinium hexafluorophosphoric acid (SBPPF ₆ ) was added and hexamethylcyclotrisiloxane (manufactured by Tokyo Kasei Kogyo Co., Ltd .: reagent, the following formula No. 1), which is a cyclic siloxane, was further reduced to 0. 1 wt% was added and dehydrated to obtain an electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less (same as above, “Invention 7”).

Similarly, LiPF ₆ is added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate is 1: 1 so that the concentration is 1.0 mol / L, and further, triethylmethylammonium hexahexadium is added so that the concentration becomes 0.5 mol / L. Add fluorophosphoric acid (TEMMAPF ₆ ), add 0.1 wt% of hexamethylcyclotrisiloxane (Tokyo Kasei Kogyo Co., Ltd .: reagent, lower formula No. 1), which is a cyclic siloxane, dehydrate, An electrolytic solution for a pseudocapacitor having a moisture value of 100 ppm or less was obtained (same as above, “Invention 8”).

As a comparison, LiPF ₆ was added to a mixed solvent in which the weight ratio of ethylene carbonate and diethyl carbonate was 1: 1 so as to have a concentration of 1.0 mol / L and dehydrated to prepare an electrolytic solution having a moisture value of 100 ppm or less. (Same as above, “Comparative product 1”).

  In addition, the cyclic siloxanes “hexamethylcyclotrisiloxane (No. 1)”, “octamethylcyclotetrasiloxane (No. 2)”, “decamethylcyclopentanesiloxane (No. 3)” and the chain siloxane “hexamethyl” used this time. The chemical structural formulas of disiloxane (No. 4), “octamethyltrisiloxane (No. 5)” and “decamethyltetrasiloxane (No. 6)” are shown in the following formula.

  Table 2 shows the viscosity and electrical conductivity measurement results of these electrolyte solutions at 25 ° C.

As shown in Table 1, in the comparison of the system using only LiPF _{6 as} the electrolyte (Invention products 1 to 6, Comparative product 1), Invention products 1 to 6 added with a siloxane derivative as an additive use the additive. Compared with comparative product 1 that does not, the results are excellent in viscosity and electrical conductivity. Specifically, an effect of reducing the viscosity by about 12.2 to 4.1% and increasing the electric conductivity by about 10.0 to 3.3% was obtained. Further, it was confirmed that the more preferable additive was “hexamethylcyclotrisiloxane” used in “Invention Product 1”.

Example 2
Production of Pseudocapacitor Pseudocapacitors were produced using the electrolyte solution of Example 1 (Inventions 1 to 8 and Comparative Product 1).

  The positive electrode is an active material (activated carbon: Nippon Envirochemicals Corporation, Shirasagi KA), conductive material (Ketjen Black: Lion Corporation, ECP-600JD), and binder (PTFE: Mitsui DuPont Fluorochemical Corporation, 30-J). Were prepared. The weight composition ratio was active material: conductive material: binder = 80 parts: 10 parts: 10 parts. These mixtures were sufficiently kneaded while adding ethanol, and rolled to obtain an activated carbon sheet electrode having an average thickness of 0.85 mm. This activated carbon sheet electrode punched out with a φ15 punch is bonded to a case and cap (both made from SUS316) with a current collector (φ17 made of SUS316) with a conductive adhesive, and the positive electrode part is attached Obtained.

  The negative electrode was prepared by mixing polyacene (PAS), a conductive material (Ketjen Black: Lion Corporation, ECP-600JD), and a binder (PTFE: Mitsui DuPont Fluorochemical Co., Ltd., 30-J). The weight composition ratio was PAS: conductive material: binder = 80 parts: 10 parts: 10 parts. These mixtures were sufficiently kneaded while adding ethanol, and rolled to obtain a PAS sheet electrode having an average thickness of 0.80 mm. This activated carbon sheet electrode punched out with a φ15 punch is bonded to a case and cap (both made of SUS316) welded with a current collector (φ17 made of SUS316) with a conductive adhesive, and the negative electrode portion is attached. Obtained.

  Each of these electrodes was injected with the electrolyte solution of Example 1 and impregnated under reduced pressure at 0.010 MPa for 10 minutes, and then assembled by attaching a polypropylene gasket to the cap through a polypropylene non-woven fabric as a separator. The 2032 size coin type pseudo capacitor was completed by fitting.

Evaluation of pseudocapacitors Each pseudocapacitor was subjected to a charge / discharge test at 20 ° C. Each capacitor is allowed to stand at a predetermined measurement temperature for 30 minutes or more, and after the capacitor reaches a predetermined temperature, 4.0 V is applied as a rated voltage for 30 minutes, and then a constant current discharge is performed at a discharge current of 10 mA. The electrostatic capacity was calculated from the time from 3.2 V to 1.6 V. Moreover, the lower limit of the discharge was set to 1.5V. The leakage current was calculated by measuring the voltage between resistors of a precision resistor with a rating of 1 kΩ connected in series in the circuit after applying 3.0 V as a rated voltage for 30 minutes in the same manner as the capacitance measurement. The number of test samples was n = 10. These results are shown in Table 3 below.

As shown in Table 2, invention products 1 to ₆ using LiPF ₆ as the electrolyte salt and having a siloxane derivative added as an additive have a slightly higher capacitance and leakage than the comparative product 1 using no additive. As a result, the current is significantly reduced as compared with the comparative product. Specifically, the capacitance increases by about 2.8 to 6.1%, the internal resistance decreases by about 6.1 to 14.6%, and the leakage current is 57.2 to 45.4%. It was possible to greatly reduce.

  Inventive products 1 to 3 are superior in both capacitance and internal resistance compared to inventive products 4 to 6 to which a chain siloxane derivative is added, and the leakage current is significantly reduced compared to the comparative product. It has become. Specifically, the capacitance increases by about 3.2 to 2.1%, the internal resistance decreases by about 2.3 to 9.1%, and the leakage current value is 21.6% for the inventive product. It could be reduced by ˜12.3%, and it was confirmed that cyclic siloxane was superior to chain siloxane as an additive.

  Further, in comparison between Invention 7 and Invention 8 in which a quaternary ammonium salt was added to the electrolyte, Invention 7 in which spiro- (1,1) -bipyrrolidinium hexafluorophosphoric acid was added, Compared with Invention 8 to which triethylmethylammonium hexafluorophosphoric acid is added, the capacitance is about 3.4%, the internal resistance is 22.8%, and the leakage current is 28.6%. I was able to.

  Next, in order to evaluate the impregnation property of the electrolytic solution to the electrode, the reflow characteristics of the obtained pseudocapacitor were measured. If it can be confirmed that the characteristics of the pseudo capacitor after reflow treatment, in particular, the capacitance and internal resistance are stable and the variation is reduced, it can be determined that the electrolyte is impregnated deeper into the pores of the electrode. .

  As a reflow test condition, it processed at 180 degreeC for 1 minute as a preheating process, and after processing at 260 degreeC for 1 minute as a heating process next, it naturally cooled to 20 degreeC. Thereafter, the capacitance and internal resistance of the cell were measured under the conditions described above. The number of test samples was n = 10. These results are shown in Table 3 (capacitance) and Table 4 (internal resistance) below.

  From Tables 3 and 4, Inventions 1 to 6 using an electrolyte containing siloxane added had a variation in measured values after reflowing of about 30 to 40% compared to before reflowing for both capacitance and internal resistance. Smaller and improved. On the other hand, Comparative Product 1 to which siloxane was not added did not show an effect of improving variation in measured values in terms of capacitance and internal resistance. Therefore, in the inventive products 1 to 6 to which siloxane was added, it was confirmed that the impregnation property of the electrolyte to the electrode was improved.

  Inventive products 1 to 3 have excellent variations in capacitance and internal resistance as compared with comparative products 4 to 6 to which a chain siloxane derivative is added. Specifically, the capacitance can be increased by about 3.1 to 10.5%, and the internal resistance can be reduced by about 26.5 to 40.4%. The cyclic siloxane is more preferable than the chain siloxane. It was confirmed that it was excellent as an additive.

  Further, in comparison between Invention 7 and Invention 8 in which a quaternary ammonium salt was added to the electrolyte, Invention 7 in which spiro- (1,1) -bipyrrolidinium hexafluorophosphoric acid was added, Compared to Invention 8 to which triethylmethylammonium hexafluorophosphoric acid was added, it was found that Invention 7 was better in terms of both capacitance and internal resistance, with less variation.

  From the above results, it can be confirmed that the more preferable additive is “hexamethylcyclotrisiloxane” used in “Invention Product 1”, and spiro- (1,1) which is a quaternary ammonium salt. -It was confirmed that the characteristics of pseudocapacitors were further improved by adding bipyrrolidinium hexafluorophosphoric acid.

  When the siloxane derivative, which is an additive for the electrolytic solution for the pseudocapacitor of the present invention, is used, as described above, the impregnation property when producing a pseudocapacitor is improved even with a very small amount of addition, and accordingly, a high capacity, low Leakage current is possible. Further, by using these additives in combination with a spiro compound in particular in an electrolyte, it is possible to exhibit various characteristics far superior to conventional ones.

The schematic sectional drawing which shows an example of a structure of the pseudocapacitor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Negative electrode cap 2 Negative electrode 3 Current collector 4 Electrolyte 5 Separator 6 Positive electrode 7 Positive electrode case 8 Gasket

Claims (4)

An electrolytic solution for a pseudocapacitor in which an electrolyte and an additive are contained in a solvent, wherein the additive is a compound represented by the following general formula (1).

(In the formula, R1 to R6 each represents an organic group that may be the same or different, and those that can be bonded to each substituent may be substituted. N represents an integer of 1 to 10. ) An electrolytic solution for a pseudocapacitor in which an electrolyte and an additive are contained in a solvent, wherein the additive is a compound represented by the following general formula (2).

(In the formula, R7 and R8 each represents an organic group which may be the same or different, and those capable of binding a substituent may be substituted. N represents an integer of 2 or more and 10 or less. )   The electrolytic solution for pseudocapacitors according to claim 1 or 2, wherein the content of the additive is 0.001 to 10% by weight.   A pseudocapacitor obtained by impregnating a polarizable electrode sandwiching a separator with the electrolytic solution according to any one of claims 1 to 3, and sealing the impregnated electrode in a container.

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