JP2011077377A - Electric double-layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor that is usable above 85°C and can have a longer life. <P>SOLUTION: This invention provides the electric double-layer capacitor that is usable above 85°C and can have a longer life by suppressing deterioration of an electrolyte and a current collector by suppressing reaction between the electrolyte or water in an electrode and the current collector since the current collector is made of aluminum having a reactive chemical conversion coating formed on a surface. Then there is no increase in internal resistance since the reactive chemical conversion coating has high conductivity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electric double layer capacitor using a non-aqueous electrolyte.

    An electric double layer capacitor is formed by winding or laminating a separator between a polarizable electrode in which a polarizable electrode layer (for example, a carbon layer) is provided on the surface of a metal foil made of aluminum, for example. It has a structure in which an electrolytic solution is impregnated and the capacitor element is housed in a metal case, and the open end is sealed or sealed with a laminate film.

  The electric double layer capacitor described above is required to have a high capacity and excellent long-term reliability, and a carbonate-based solvent such as propylene carbonate is used as an electrolytic solution of a conventional electric double layer capacitor. According to this, an electric double layer capacitor having a high capacity and excellent high temperature load characteristics can be obtained.

  However, in an electrolytic solution using a carbonate-based solvent, carbon monoxide (CO) gas is generated due to decomposition of the solvent at a high temperature, so that the internal pressure of the container containing the polarizable electrode, the electrolytic solution, etc. increases. Problems arise. For this reason, the use temperature of the electric double layer capacitor is limited to 60 ° C., and there is a problem that it cannot cope with use at a higher temperature of 70 to 85 ° C. On the other hand, there is an attempt to enable use at 70 ° C. using γ-butyrolactone (Patent Document 1).

JP 2001-217150 A

  However, if further use at 85 ° C. is attempted, deterioration of characteristics cannot be suppressed. In addition, an improvement in life characteristics has been demanded for an electrolytic solution using a carbonate-based solvent. Accordingly, an object of the present invention is to solve this problem and to provide an electric double layer capacitor that can be used at 85 ° C. or higher and can have a longer life.

  In order to solve the above-mentioned problems, the present invention provides an electric double layer capacitor using a non-aqueous electrolyte and an electrode composed of a current collector and a polarizable electrode on both electrodes. It consists of aluminum which formed the type | mold chemical conversion film.

The reactive chemical conversion film is formed by a chromate treatment.

The chromate treatment is a phosphate chromate treatment.

  In the present invention, since the current collector is made of aluminum having a reactive chemical conversion film formed on the surface, the reaction between the electrolyte or the water in the electrode and the current collector is suppressed, thereby Deterioration is suppressed, use at 85 ° C. or higher is possible, and long-life characteristics are achieved. And since the reactive chemical film has high conductivity, there is no increase in internal resistance.

It is a figure which shows the lifetime characteristic of the capacity | capacitance which concerns on Example 1 and Comparative Example 1 of this invention. It is a figure which shows the lifetime characteristic of the internal resistance which concerns on Example 1 and Comparative Example 1 of this invention. It is a figure which shows the lifetime characteristic of the capacity | capacitance which concerns on Example 2 and Comparative Example 2 of this invention. It is a figure which shows the lifetime characteristic of the internal resistance which concerns on Example 2 and Comparative Example 2 of this invention. It is a figure which shows the lifetime characteristic of the capacity | capacitance which concerns on Example 3 and Comparative Example 3 of this invention. It is a figure which shows the lifetime characteristic of the internal resistance which concerns on Example 3 and Comparative Example 3 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the present invention, an electric double layer capacitor is manufactured by making a capacitor cell by facing a metal current collector foil made of aluminum with a polarizable electrode layer facing through a separator, and impregnating the capacitor cell with an electrolyte. An electric double layer capacitor is obtained.

  A reactive chemical conversion film is formed on the surface of the current collector of the electric double layer capacitor. Examples of the reactive chemical conversion film include a film formed by a phosphate chromate treatment, a chromate chromate treatment, or a film formed by a so-called non-chromate treatment such as a reactive zirconium phosphate treatment or a titanium phosphate treatment. it can. Of these, phosphoric acid chromate treatment is preferred from the viewpoint of cost and productivity.

  As the metal current collector foil used for the electrode, an aluminum foil or an aluminum etching foil is used. As the aluminum foil, high-purity aluminum having a purity of 99.9% or more is used. As the thickness, an aluminum foil having a thickness of about 10 to 50 μm is usually used.

  For example, a paste obtained by mixing activated carbon powder, a conductive additive, a binder, and a solvent such as an organic solvent or water is applied to the metal current collector foil. Alternatively, the paste is formed into a sheet shape, and this sheet is pressed against a current collector to form a polarizable electrode.

The raw material of the activated carbon is plant-based wood, sawdust, coconut husk, pulp waste liquid, fossil fuel-based coal, petroleum heavy oil, or coal and petroleum-based pitch, petroleum coke obtained by pyrolyzing them. Activated carbon is obtained by carbonizing these raw materials and then activating them.
As the conductive assistant, carbon black or graphite, which is a carbon material having conductivity, can be used. Examples of the carbon black include acetylene black, ketjen black, channel black, furnace black, and thermal black. Among these, ketjen black is preferable. Examples of graphite include natural graphite and artificial graphite.
Any binder may be used as long as it is usually used, for example, rubbers such as fluorine rubber, diene rubber and styrene rubber, fluorine-containing polymers such as polytetrafluoroethylene and polyvinylidene fluoride, and the like. , Polyolefin resin, acrylic resin, nitrile resin, polyester resin, phenol resin, polyvinyl acetate resin, polyvinyl alcohol resin, epoxy resin and the like.
A capacitor element is produced by making this electrode face each other with a separator interposed therebetween, and the capacitor element is impregnated with an electrolytic solution to obtain an electric double layer capacitor.

  In the present invention, γ-butyrolactone, sulfolane or a derivative thereof, and propylene carbonate are used as the main solvent as the electrolytic solution. In addition, as a co-solvent, carbonates such as ethylene carbonate, butylene carbonate, dimethyl carbonate and diethyl carbonate; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran Sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; nitrogen-containing compounds such as acetonitrile and nitromethane; methyl formate, methyl acetate, ethyl acetate, butyl acetate, Organic acid esters such as methyl propionate and ethyl propionate; inorganic acid esters such as phosphoric acid triester and diester carbonate such as dimethyl carbonate, diethyl carbonate and dipropyl carbonate; diglyme ; Triglyme like; oxazolidinones such as 3-methyl-2-oxazolidinone; 1,3-propane sultone, 1,4-butane sultone can be used sultone like such Nafutasuruton.

Examples of the electrolyte dissolved in the organic solvent include metal cations, quaternary ammonium cations, phosphonium, carbonium cations, and the like, BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , A salt of an anion selected from AlCl ₄ ⁻ , RfSO ₃ ⁻ , (RfSO ₂ ) ₂ N ⁻ , RfCO ₂ ⁻ (Rf is a fluoroalkyl group having 1 to 8 carbon atoms) can be mentioned.

  The electric double layer capacitor of the present invention may have any shape such as a coin type, a wound type, and a laminated type. Such an electric double layer capacitor is obtained by, for example, cutting an electrode sheet into a desired size and shape, stacking or winding the separator sheet between both electrodes, inserting the electrolyte into the container, It can be manufactured by caulking the seal using a sealing plate or gasket, or sealing with a laminate film.

The invention according to the embodiment of the present invention will be specifically described.
Example 1
A mixture of activated carbon powder, ketjen black as a conductive aid, and polyterafluorofluoroethylene (PTFE) as a binder was formed into a sheet using a rolling roller, and this was used as a polarizable electrode. An aluminum foil immersed in a phosphoric acid-chromic acid mixed solution and subjected to phosphoric acid chromate treatment was used as a current collector. The sheet-like polarizable electrode was attached to a current collector provided with a lead wire by using a conductive adhesive to obtain an electrode. The produced two electrodes face each other through a cellulose separator to produce an electric double layer capacitor element (electrode area 12 cm ² ). This electric double layer capacitor element was dried under reduced pressure at 150 ° C. for 12 hours or more, and then impregnated with 1M tetraethylammonium tetrafluoroborate (TEABF4) / γ-butyrolactone (GBL) electrolyte under reduced pressure in a dry box under an argon atmosphere. An electric double layer capacitor cell was produced by enclosing in a film. This electric double layer capacitor cell was subjected to a 2.5 V constant voltage load test in an atmosphere of 85 ° C., and the capacity (F) and direct current resistance (DCIR) were measured at an arbitrary time.

(Example 2)
An electric double layer capacitor element was produced in the same manner as in Example 1. This electric double layer capacitor element was dried under reduced pressure at 150 ° C. for 12 hours or more, and then impregnated with 1M triethylmethylammonium tetrafluoroborate (TEMABF4) / sulfolane (SLF) electrolyte under reduced pressure in a dry box under an argon atmosphere, and a laminate film The electric double layer capacitor cell was fabricated by enclosing in This electric double layer capacitor cell was subjected to a 2.5 V constant voltage load test in an atmosphere of 105 ° C., and the capacity (F) and direct current resistance (DCIR) were measured at an arbitrary time.

(Example 3)
An electric double layer capacitor element was produced in the same manner as in Example 1. This electric double layer capacitor element was dried under reduced pressure at 150 ° C. for 12 hours or more, and then impregnated with 1M tetraethylammonium tetrafluoroborate (TEABF4) / propylene carbonate (PC) electrolyte under reduced pressure in a dry box under an argon atmosphere to form a laminate film The electric double layer capacitor cell was fabricated by enclosing in This electric double layer capacitor cell was subjected to a 2.5 V constant voltage load test in an atmosphere of 60 ° C., and the capacity (F) and direct current resistance (DCIR) were measured at an arbitrary time.

(Comparative Example 1)
An electric double layer capacitor cell was produced in the same manner as in Example 1 using an aluminum foil not subjected to the phosphate chromate treatment as a current collector. The same test as in Example 1 was performed on the electric double layer capacitor cell.

(Comparative Example 2)
An electric double layer capacitor cell was produced in the same manner as in Example 2 using an aluminum foil not subjected to the phosphate chromate treatment as a current collector. The same test as in Example 2 was performed on this electric double layer capacitor cell.

Comparative Example 3 An electric double layer capacitor cell was produced in the same manner as in Example 3 using an aluminum foil not subjected to phosphoric acid chromate treatment as a current collector. The same test as in Example 3 was performed on this electric double layer capacitor cell.

(result)
As apparent from FIGS. 1 to 6, the example of the present application is better in both capacitance change and internal resistance change than Comparative Examples 1 to 3 which are conventional current collectors.

Claims (3)

In an electric double layer capacitor using a non-aqueous electrolyte and an electrode made of a current collector and a polarizable electrode on both electrodes, an electric double layer made of aluminum with a positive and / or negative electrode current collector forming a reactive chemical conversion film on the surface Capacitor. The electric double layer capacitor according to claim 1, wherein the reactive chemical conversion film is formed by a chromate treatment. The electric double layer capacitor according to claim 2, wherein the chromate treatment is a phosphoric acid-chromic acid immersion treatment.