JP3151941B2 - Electric double layer capacitor - Google Patents

Abstract

PURPOSE:To obtain an electric double layer capacitor excellent in long term reliability wherein stable characteristics can be continuously obtained for a long time without decreasing the applied voltage under a high temperature condition. CONSTITUTION:The capacitor is provided with the following; a sheath case 16 composed of an anode member 14 constituted of stainless having a clad- bonded aluminum layer 13 and a cathode member 15 constituted of stainless, a pair of polarizable electrodes 11a, 11b arranged in the sheath case 16 so as to be in contact with the aluminum layer 13, and a separator 12 which is interposed between a pair of the polarizable electrodes 11a, 11b and impregnated with electrolyte. A layer containing phosphorus elements is formed on the surface or in the inside of the aluminum layer 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor used as a memory backup for various electronic devices.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional electric double layer capacitor of this type is formed by press-forming activated carbon particles or kneading an activated carbon particle with a suitable binder on a current collector metal. A sprayed layer of aluminum on fibers is formed to form polarizable electrodes 1a and 1b, and an aluminum layer 2 in which the polarizable electrodes 1a and 1b are clad bonded to the inner surface.
The metal case 3 is housed so as to serve as an anode, and the separator 4 is interposed between the polarizable electrodes 1a and 1b and impregnated with an organic electrolytic solution. Is sealed with a metal lid 6 via a gasket 5.

[0003]

In recent years, in the electronics industry, particularly in the field of industrial equipment, high temperature and long life are desired. Here, in the above-described conventional configuration, 7
A device that can be used continuously for 2,000 hours by applying 2.8 V per unit cell at an environmental temperature of 0 ° C., when 2.8 V is applied under a high temperature condition of 85 ° C., characteristic degradation occurs in a short time. This is because a concerted reaction between oxide film formation and metal dissolution occurs on the anode side, and a solvent decomposition reaction occurs on the cathode side. In particular, the metal dissolution reaction on the anode side was a major cause of characteristic deterioration. Therefore, in order to use the conventional product under a high temperature condition of 85 ° C., unless the applied voltage per cell is reduced to 1.8 V, stable characteristics cannot be obtained continuously for 2,000 hours. was there.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides an electric double layer excellent in long-term reliability that can obtain stable characteristics continuously for a long time without lowering the applied voltage even under high temperature conditions. It is an object to provide a capacitor.

[0005]

In order to achieve the above object, an electric double layer capacitor according to the present invention comprises an anode member made of stainless steel having an aluminum layer or an aluminum layer clad and bonded to a cathode member made of stainless steel. And a pair of polarizable electrodes provided in the outer case such that one of them is in contact with the aluminum or the aluminum layer, and is interposed between the pair of polarizable electrodes and impregnated with the electrolytic solution. And a layer containing a phosphorus element provided on the surface or inside of an aluminum layer clad with aluminum or stainless steel constituting the anode member.

[0006]

According to the above structure, the layer containing the phosphorus element is provided on the surface or inside of the aluminum layer clad with aluminum or stainless steel constituting the anode member. It is possible to suppress the metal dissolution reaction on the anode side, and thereby, it is possible to obtain stable characteristics continuously for a long time without lowering the applied voltage even under a high temperature condition of, for example, 85 ° C., and it is excellent in long-term reliability. The resulting electric double layer capacitor is obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an electric double layer capacitor according to one embodiment of the present invention. In FIG. 1, reference numerals 11a and 11b denote sheet-like activated carbon made of activated carbon fiber or activated carbon powder in the form of a disk having a diameter of 2 cm. It is a pair of polarizable electrodes obtained by extracting with a punching die.

Between the pair of polarizable electrodes 11a and 11b, a separator 12 impregnated with an electrolytic solution in which 10% by weight of tetraethylammonium tetrafluoroborate is dissolved in propylene carbonate is interposed, and these are clad-joined. It is provided in an outer case 16 composed of an anode member 14 made of a dish-shaped metal case made of stainless steel having an aluminum layer 13 inside and a cathode member 15 made of a metal lid made of stainless steel.

In this case, a pair of polarizable electrodes 11a, 11
b is one side of the aluminum layer 13 of the anode member 14
Will be equipped to touch. Further, the anode member 14 and the cathode member 15 are connected to the peripheral edge of the opening of the dish-shaped metal case constituting the anode member 14 through the gasket 17.
The exterior case 16 is formed by sealing and sealing with a metal lid constituting the above.

The anode member 14 is provided on the surface or inside of the aluminum layer 13 clad with the inside of a stainless steel dish-shaped metal case constituting the anode member 14.
Is preliminarily boiled in a 2% aqueous solution of phosphoric acid at 75 ° C. to 85 ° C. (Example 1) or a 2% aqueous solution of monoammonium phosphate at 75 ° C. to 85 ° C. (Example 2) for 10 minutes to remove the element of phosphorus. Including a layer.

Table 1 shows conventional characteristics of the electric double layer capacitor according to the embodiment of the present invention (capacitance change rate, internal resistance) after a high temperature load test (at 85 ° C., 2.8 V applied, after 2,000 hours). It is shown in comparison with.

[0012]

[Table 1]

As is apparent from Table 1, the embodiment of the present invention has an excellent effect in that the rate of change in capacitance and the rate of change in internal resistance after a high-temperature load test are smaller than in the conventional example. Have

FIG. 2 is a characteristic diagram showing a current-potential curve in the oxidation direction of untreated aluminum in a non-aqueous electrolyte. When the first sweep shown by a solid line is performed, the breakdown voltage of the natural oxide film is reduced. The current starts to rise from around. As the voltage increases, the current also increases accordingly. Here, when the voltage is held at a certain voltage V ₂ , and then the second sweep indicated by the dashed line is performed again from the natural potential,
With a breakdown voltage of up to V _2. In this state, when the electrode is immersed in the non-aqueous electrolyte for a long time, and the voltage is again swept from the spontaneous potential, a rise in current is observed at a potential lower than V _{2 as} shown by a broken line. This phenomenon occurs because
It is considered that an anion in the electrolytic solution attacks the aluminum oxide film on the anode side to cause a metal dissolution reaction.

On the other hand, as in the embodiment of the present invention, the element of phosphorus is contained on the surface or inside of the aluminum layer 13 which is clad and bonded to the inside of a stainless steel dish-shaped metal case constituting the anode member 14. In those provided with layers,
When the same operation as that shown in FIG. 2 is performed, that is, the first sweep shown by the solid line in FIG. 3 and the second sweep shown by the one-dot chain line, almost the same characteristics as those shown in FIG. 2 are obtained. Was. Then, while maintaining the pressure resistance up to V2 by the _second sweep, immersing in the non-aqueous electrolyte for a long time and again performing the sweep from the natural potential, as shown by the broken line, almost V The pressure resistance of ₂ could be maintained. This is because, on the anode side, the layer containing the phosphorus element provided on the surface or inside of the aluminum layer 13 suppresses the anion in the electrolytic solution from attacking the aluminum oxide film to cause a metal reaction. It is thought that there is.

In the above embodiment, the anode member 1
4 is described in which a layer containing a phosphorus element is provided on the surface or inside of an aluminum layer 13 clad inside a stainless steel dish-shaped metal case constituting the anode member 4. In the case of a metal case, a layer containing a phosphorus element may be provided on the surface or inside of the aluminum constituting the metal case. In this structure, the same operation and effect as those of the above embodiment can be obtained. It is.

[0017]

As described above, according to the present invention, a layer containing a phosphorus element is provided on the surface or inside of the aluminum layer clad with aluminum or stainless steel constituting the anode member. By the function of the layer containing, it is possible to suppress the metal dissolution reaction on the anode side, whereby it is possible to obtain stable characteristics continuously for a long time without lowering the applied voltage even under a high temperature condition of, for example, 85 ° C. An electric double layer capacitor excellent in long-term reliability that can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electric double layer capacitor showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a current-potential curve in the oxidation direction of untreated aluminum in a non-aqueous electrolyte.

FIG. 3 is a characteristic diagram showing a current-potential curve in the oxidation direction of aluminum containing a phosphorus element in a non-aqueous electrolyte.

FIG. 4 is a sectional view of an electric double layer capacitor showing a conventional example.

[Explanation of symbols]

 11a, 11b A pair of polarizable electrodes 12 Separator 13 Aluminum layer 14 Anode member 15 Cathode member 16 Outer case

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-289920 (JP, A) JP-A-63-261815 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 9/016

Claims (1)

(57) [Claims] 1. An outer case comprising an anode member made of stainless steel having an aluminum layer clad with aluminum or aluminum and a cathode member made of stainless steel, and one of the outer case contacts the aluminum or aluminum layer inside the outer case. An aluminum layer comprising a pair of polarizable electrodes equipped as described above and a separator interposed between the pair of polarizable electrodes and impregnated with an electrolyte, and clad to aluminum or stainless steel constituting the anode member An electric double layer capacitor characterized in that a layer containing a phosphorus element is provided on the surface or inside of the electric double layer capacitor.