JPH0982572A - Electric double layer capacitor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce inner resistance without increasing the capacity of an electric double layer capacitor. SOLUTION: As a separator, a separator made of porous ceramic better in wettability to electrolytic solution than a conventional porous film made of polypropylene is used. Moreover, the opposite area of the fellow activated carbon electrodes 1A and 1B is increased by meandering this. At the time of manufacture, a stacked pressed body is manufactured by repeating the operation of pressing activated carbon electrode material where a binder and activated carbon powder are kneaded into plate form, and pressing ceramic powder into plate form on the plate, and then it is baked in steam atmosphere at high temperature. The binder in the activated carbon electrode material becomes porous activated carbon, being carbonated and is activated by steam, and at the same time, the ceramic powder for a separator becomes porous, being sintered, so production efficiency is high.

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 and a method for manufacturing the same, and more particularly to a technique for reducing the internal resistance of the capacitor.

[0002]

2. Description of the Related Art As one of means for obtaining a large-capacity capacitor using an electric double layer, as disclosed in US Pat. No. 3,536,963, activated carbon powder and an electrolyte solution are brought into contact with each other to form a solid capacitor. There is a technique for forming an electric double layer at the liquid interface.

FIG. 3 (a) is a sectional view of an example of a conventional electric double layer capacitor realized using the above-mentioned activated carbon powder and electrolyte solution. As will be described later, a practical electric double layer capacitor often has a structure in which the capacitors shown in FIG. 3 (a) are pressed individually or in a state in which a plurality of capacitors are vertically stacked. In that sense, the structure having no pressing structure as shown in FIG. 3A is hereinafter referred to as an electric double layer capacitor element. FIG.
With reference to (a), in this capacitor element, the upper and lower sides of the cylinder composed of the upper and lower cylindrical gaskets 4A and 4B are
The upper and lower current collectors 3A and 3B are respectively blocked.
The gaskets 4A and 4B are made of an insulating material such as butyl rubber. On the other hand, the current collectors 3A and 3B are made of a conductive material such as butyl rubber in which carbon is kneaded so as to have conductivity. The space inside the bottomed cylinder composed of the gasket and the current collector is divided into upper and lower two spaces by a separator 22 sandwiched between the two gaskets 4A and 4B, and an activated carbon electrode is provided in each space. 21A and 21B are filled. The activated carbon electrodes 21A and 21B are in the form of paste obtained by kneading activated carbon powder and an electrolyte solution such as an aqueous sulfuric acid solution. The separator 22 prevents the activated carbon powder in the upper and lower activated carbon electrodes 21A and the activated carbon powder in the activated carbon electrode 21B from directly contacting each other so that the two activated carbon electrodes 21A and 21B are not electrically short-circuited by electron conduction. It is made of a non-electroconductive and ion-permeable material such as a porous film made of polypropylene so that cations or anions in the activated carbon electrode can pass through.

The capacitor element shown in FIG. 3A is generally manufactured by the following manufacturing process. First, a gasket 4A obtained by punching a butyl rubber plate into a ring shape and a current collector 3A made of a conductive butyl rubber plate are bonded together. Next, the concave portion formed by the bonding is filled with a paste-like activated carbon electrode material prepared by kneading activated carbon powder and a sulfuric acid aqueous solution in advance to obtain the gasket 4A filled with the activated carbon electrode 21A. Similarly, gasket 4
The activated carbon electrode 21B is filled in the recess formed by bonding B and the current collector 3B to obtain the gasket 24B filled with the activated carbon electrode 21B. After that, the two gaskets filled with the activated carbon electrodes are opposed to each other with the separator 22 interposed therebetween, and the two gaskets 4A and 4B are adhered by, for example, vulcanization pressure bonding or the like to complete a capacitor element.

Usually, the above capacitor element has a structure in which a plurality of capacitors are laminated in series in order to have a withstand voltage against the working voltage of the circuit when used in an electronic circuit. The withstand voltage of the capacitor element is determined by the electrolysis voltage of the electrolyte solution, since the capacity of this type of capacitor is obtained by solid-liquid contact in principle. The electrolysis voltage depends on the type of electrolyte solution, but the withstand voltage of a capacitor element using an aqueous electrolyte solution such as an aqueous solution of sulfuric acid is about 1.2 V which is the electrolysis voltage of water. On the other hand, for example, most semiconductor integrated circuits (LSIs) use a power supply voltage of 5.0V. Therefore, in order to use the electric double layer capacitor for backing up an LSI, it is necessary to stack five or more capacitor elements shown in FIG. 3A in series. As the electrolyte solution of the electric double layer capacitor, there is an organic solvent-based electrolyte solution in addition to the above-mentioned aqueous solution-based one, and if this is used, a higher withstand voltage can be obtained than a capacitor element using an aqueous solution-based electrolyte solution. However, in any case, when the electric double layer capacitor is put to practical use, it is generally necessary to stack the electric double layer capacitors so as to have a withstand voltage commensurate with the working voltage of the electronic circuit.

FIG. 3B shows a sectional view of a capacitor in which eight capacitor elements shown in FIG. 3A are laminated as an example of the electric double layer capacitor having the above-mentioned laminated structure.
Referring to FIG. 33 (b), the element laminated body 5 is housed in a cylindrical metal case 8 whose one surface is open. Laminate 5
Shows that eight capacitor elements having the structure shown in FIG. 3A are stacked. On the open side of the case 8 of the laminated body 5,
The electrode plate 7B with lead terminals is addressed. Electrode plate 7
Further, an electrode plate 7A with lead terminals is attached to B by sandwiching the insulating case 6, and the electrode plate 7A closes the open surface of the metal case 8. Insulation case 6 is laminated body 5
To prevent the side surface of the laminated body 5 and the inner side wall of the case 8 from being short-circuited. Also, it is interposed between the two electrode plates 7A and 7B to prevent the two electrode plates from being short-circuited. The edge 9 on the open surface side of the metal case 8 is bent inward in a curled shape and is in contact with the outer electrode plate 7A. Due to this structure, the current collector on the uppermost surface of the laminated body 5 is eventually
It is connected to the electrode plate 7A through the metal case 8.

Here, in the electric double layer capacitor having the laminated structure shown in FIG. 3B, the edge 9 on the open side of the metal case 8 is bent in a curl shape as described above. 5 is for electrically connecting the electrode plate 7A,
Another purpose is to lower the internal resistance of the capacitor. In other words, it is well known that an electric double layer capacitor generally has a large capacity but a relatively large internal resistance, and a device for reducing the internal resistance as much as possible is indispensable for expanding applications. The curled portion of the open edge 9 of the case 8 in the capacitor shown in FIG. 3B is for reducing the internal resistance of the capacitor from the viewpoint of the structure, and the laminated body 5 is housed in the case 8 during manufacturing. When the pressure is applied between the closed bottom surface of the case 8 and the outermost electrode plate 7A, and the open edge 9 of the case is bent under the pressure, the pressure applied to the laminated body 5 is maintained even after the manufacturing. It is also for holding with the rigidity of.
By applying such a vertical pressure to the laminated body 5,
Since the contact resistance between the activated carbon powders forming the activated carbon electrodes in each capacitor element is small and the contact resistance between the capacitor elements forming the laminated body 5 is also small, the internal resistance of the entire capacitor is reduced. It gets smaller.

As described above, it is important to devise to reduce the internal resistance of the electric double layer capacitor, and various techniques have been proposed so far for the purpose of reducing the internal resistance. As a technique for reducing the internal resistance from the viewpoint of the structure of the capacitor, there is an electric double layer capacitor having a structure shown in FIG. 4 in addition to the capacitor in which the edge of the metal case is curled inward. The capacitor shown in this figure is
This is disclosed in Japanese Patent Application Laid-Open No. 4-240708, and the internal resistance is lowered while the volume of the capacitor remains the same by increasing the facing area of the activated carbon electrode. That is, referring to FIG. 4, between the two activated carbon electrodes 31A and 31B which are made into a cloth by adding a binder or the like,
After preliminarily sandwiching the porous separator 22 made of a band-shaped polypropylene film, these are folded in a zigzag form and impregnated with a sulfuric acid aqueous solution as an electrolyte solution. The zigzag-folded separator sandwiching activated carbon electrode is housed in a non-conductive gasket 4 made of butyl rubber, and the upper and lower parts of the gasket are made of conductive butyl rubber current collectors 3A and 3B.
1A is in contact with the current collector 3A and the activated carbon electrode 31B is in the current collector 3
By closing so as to contact B, the facing area between the electrodes is increased. An electric double layer capacitor having a similar structure is disclosed in Japanese Patent Laid-Open No. 4-75313. The capacitor described in this publication is intended not for the purpose of directly lowering the internal resistance but for increasing the electrostatic capacitance, but it may be effective for lowering the internal resistance.

Next, Japanese Unexamined Patent Publication (Kokai) No. 5-159972 discloses a technique for reducing the internal resistance of an electric double layer capacitor in terms of its constituent members. That is, it is a capacitor that uses a ceramic separator mainly containing silica fiber containing no binder, instead of the polypropylene separator. Since the above-mentioned ceramic separator has better wettability with the electrolyte solution than the polypropylene separator, an electric double layer capacitor having a low internal resistance can be obtained by using this.

[0010]

In recent years, electric double layer capacitors have come to be used as an auxiliary energy source for an electro-mechanical energy conversion mechanism, such as current supply at the time of starting a motor, by taking advantage of its large capacity. Is coming. Further, since it is necessary to instantaneously supply a large current in such an application, there is an increasing need to significantly reduce the internal resistance more than ever before. In order to reduce the internal resistance, as described above, in order to reduce the resistance of each constituent member and the contact resistance between each constituent member, conventionally, the specific resistance of the member itself is lowered or the structure is improved. Things are being done. However, in consideration of the above expansion of applications, the internal resistance of the capacitor must be further reduced. In addition, in that case, the volume of the capacitor should not be increased in view of the strong demand for miniaturization of components with the recent miniaturization of electronic devices.

Therefore, an object of the present invention is to further reduce the internal resistance of the electric double layer capacitor without increasing the volume.

Another object of the present invention is to provide a method of manufacturing the above electric double layer capacitor having a low internal resistance.

[0013]

The electric double layer capacitor of the present invention comprises a tubular gasket made of a non-conductive material and having both open ends, and a gasket made of a material impermeable to ions and having an electronic conductivity. It consists of two current collectors that close one open end face and a porous ceramic plate that is ion-permeable and non-electroconductive.The space surrounded by the gasket and two conductive separators is divided into two spaces in a zigzag pattern. In the separator, one space after being divided is closed by one of the two current collectors, and the other space is divided so as to be closed by the other current collector, and the separator And two activated carbon electrode layers separated by means of one of them, one of the two activated carbon electrodes being in contact with the one current collector and the other being arranged so as to be in contact with the other current collector. An electric double layer capacitor comprising an electrode.

The above-mentioned electric double layer capacitor has an operation of press-molding an activated carbon electrode material, which is a mixture of activated carbon powder and a binder, into a flat plate having projections for vertical connection on one surface, and the result of the operation. On the flat plate thus obtained, the operation of press-molding the raw material ceramic powder to be the separator into a flat plate having projections for vertical connection on one surface is repeated, and the flat plate made of the activated carbon electrode material and the ceramic powder are formed. Flat plates are alternately laminated, and flat plates made of the ceramic powder are connected in a zigzag shape vertically, and flat plates made of the activated carbon electrode material are formed to form a laminate having a structure in which they are vertically connected to each other, When the laminated body is fired in a high-temperature steam atmosphere to carbonize and activate the binder in the flat plate made of the activated carbon electrode material to make it porous, A step of sintering a flat plate made of the ceramic powder to make it porous, a step of impregnating the porous body with an electrolyte solution, and a laminate impregnated with the electrolyte solution in the gasket. It is manufactured by a manufacturing method of an electric double layer capacitor including a step of housing and enclosing with a current collector.

The electric double layer capacitor of the present invention has a structure in which the above electric double layer capacitor is used as a unit and a plurality of electric double layer capacitors of the unit are laminated so as to be electrically connected in series. This is an electric double layer capacitor having a characteristic laminated structure.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an electric double layer capacitor element according to an embodiment of the present invention. FIG. 2 is a diagram showing a cross section of the capacitor element shown in FIG. 1 in the order of manufacturing steps.

Referring to FIG. 1, in the electric double layer capacitor element shown in this figure, upper and lower open surfaces of a cylindrical gasket 4 made of insulating butyl rubber are covered with current collectors 3A, 3B made of conductive butyl rubber. I'm out. The space inside the gasket 4 is divided into two spaces by a serpentine porous ceramic separator. One space is collector 3A
It is covered with and the inside is filled with the activated carbon electrode 1A. The activated carbon electrode 1A is in contact with the current collector 3A. The other space is covered with a current collector 3B, and the activated carbon electrode 1B is filled inside. The activated carbon electrode 1B is in contact with the current collector 3B. In this embodiment, eight electric capacitor elements shown in FIG. 1 are laminated to form an electric double layer capacitor having a laminated structure shown in FIG.

The capacitor element shown in FIG. 1 is manufactured as follows. Referring to FIG. 2, first, 40% phenol resin as a binder and activated carbon powder (specific surface area: 1
500 m ² / g) was kneaded with the activated carbon electrode material and press-formed on a disk 1B ₁ having a diameter of 18 mm (pressure: 100 kg).
/ Cm ² ) (FIG. 2 (a)). _On the peripheral portion of the disc 1B _1, the upper layer activated carbon electrode 1B to be laminated in the subsequent process.
₂ to connect to (see FIG. 2 (e) see), previously provided with projections.

Next, a ceramic powder containing silica fibers as a main component is press-molded into a disk shape on the disk 1B ₁ for an activated carbon electrode to form a disk 2 ₁ which will later become a separator (see FIG. 2 ( b)). This separator 2 ₁ has a diameter of 17.8 m.
m. Similar to the disk 1B ₁ for the activated carbon electrode, an upper layer separator 2 ₂ (FIG.
(See (d)). This projection is also for preventing the short circuit due to the contact between the activated carbon electrode 1B ₁ of the first layer and the activated carbon electrode 1A ₁ of the third layer (see FIG. 2C).

Furthermore, on the separator 2 _1, the disc 1A ₁ for activated carbon electrode facing the activated carbon electrode 1B ₁ of the first layer across the separator 2 _1, press molding (FIG. 2 (c )). In this disk 1A ₁ as well as its peripheral part,
Disk 1A for the upper layer of activated carbon electrode to be laminated in the subsequent steps
₂ Provide a protrusion for connection with (see FIG. 2 (f)). The thickness of the disc 1A ₁ is twice that of the disc 1B ₁ of the first layer.

Thereafter, in the same manner as above, the ceramic powder and the activated carbon electrode material are alternately press-molded, and the ceramic powder disk 2 ₂ and the activated carbon electrode disk 1B ₂ are sequentially laminated (FIG. 2 (d). ), (E)). The laminated press body (FIG. 2 (f)) thus obtained was prepared by the above laminating operation.
It has been repeated over and over. The final 11th layer of the thickness of the activated carbon electrode disc 1A _3, in the same as the first layer of the disk 1B ₁ thickness, the thickness of the activated carbon electrode is set to be equal across the separator.

The mass obtained by press molding in this manner is
Baking is performed in a steam atmosphere of 0 to 900 ° C. As a result, the phenol resin mixed with the activated carbon powder as a binder is carbonized and simultaneously activated by steam to become activated carbon, which becomes porous. On the other hand, the ceramic powder is sintered into a porous ceramic separator.

Next, the porous mass is vacuum impregnated with a 30 wt% dilute sulfuric acid aqueous solution, and the air in the pores in the activated carbon electrodes 1A and 1B and the porous ceramic separator 2 is replaced with the dilute sulfuric acid aqueous solution.

Thereafter, the activated carbon electrode / separator integrated product impregnated with the dilute sulfuric acid aqueous solution is housed in a cylindrical gasket 4 made of insulating butyl rubber. Further, the gasket 4 is covered with butyl rubber-based current collectors 3A and 3B to which conductivity is imparted by kneading carbon, and the inside of the gasket is shielded from the outside air and sealed to form a capacitor element.

Finally, eight capacitor elements are vertically laminated, a pressure of 1 to 100 kg / cm ² is applied to the laminated body, and the opening edge 9 of the metal case 8 is bent inward while the pressure is maintained. By caulking and sealing, Fig. 3
The laminated electric double layer capacitor having the structure shown in (b) is completed.

In the electric double layer capacitor element obtained by the present embodiment, the activated carbon electrodes 1A and 1B are folded in a zigzag shape, so that the facing area can be widened even with the same volume,
Further, since the separator made of ceramic, which has better wettability with respect to the electrolyte solution than the polypropylene film, is used as the separator, the internal electrode resistance can be made lower than that of the electric double layer capacitors used so far.

Moreover, since the active carbonization by the carbonization and activation of the binder in the activated carbon electrode and the porosification of the ceramic separator are simultaneously performed by a single operation by high temperature firing in a steam atmosphere, mass productivity is improved. Rich in.

[0028]

As described above, in the electric double layer capacitor of the present invention, the activated carbon electrode and the separator are folded in a zigzag pattern to increase the facing area of the electrode,
Further, as the separator, a porous ceramic separator having better wettability with an electrolyte solution than a conventional polypropylene film is used. Thus, according to the present invention, it is possible to provide an electric double layer capacitor having a lower internal resistance than ever before.

Further, in the method for producing an electric double layer capacitor of the present invention, activated carbonization by carbonization and activation of the binder in the activated carbon electrode and porosification by sintering the ceramic separator are performed at high temperature in a steam atmosphere. It is done at the same time by firing. Thus, according to the present invention, an electric double layer capacitor having a low internal resistance can be efficiently manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electric double layer capacitor element according to an embodiment of the present invention.

FIG. 2 is a view showing a cross section of the electric double layer capacitor element shown in FIG. 1 in the order of manufacturing steps.

FIG. 3 is a sectional view of an example of a conventional electric double layer capacitor element and a sectional view of a laminated electric double layer capacitor in which the elements are laminated.

FIG. 4 is a cross-sectional view of another example of a conventional laminated electric double layer capacitor.

[Explanation of symbols]

 1A, 1B Activated carbon electrode 2 Separator 3A, 3B Current collector 4, 4A, 4B Gasket 5 Element laminate 6 Insulation case 7A, 7B Electrode plate 8 Metal case 9 Case open edge 21A, 21B Activated carbon electrode 22 Separator 31A, 31B Activated carbon electrode

Claims (3)

[Claims] 1. A tubular gasket made of a non-conductive material and having both open ends, two current collectors made of a material impermeable to ions and having an electronic conductivity, and closing two open end surfaces of the gasket, and ions. A separator made of a permeable, non-electroconductive porous ceramic plate, which divides the space surrounded by the gasket and two conductive separators into two spaces in a zigzag manner, one of which is divided. The space is divided by one of the two current collectors, and the other space is divided by the other current collector, and two activated carbon electrode layers separated by the separator. And an activated carbon electrode arranged such that one of the two activated carbon electrodes is in contact with the one current collector and the other is in contact with the other current collector. 2. A laminated structure comprising the electric double layer capacitor according to claim 1 as a unit, and a plurality of electric double layer capacitors of the unit are laminated so as to be electrically connected in series. Electric double layer capacitor with structure. 3. An operation of press-molding an activated carbon electrode material, which is a mixture of activated carbon powder and a binder, into a flat plate having protrusions for vertical connection on one surface, and the flat plate obtained as a result of the operation. In the above, the operation of press-molding the raw material ceramic powder to be the separator into a flat plate having projections for vertical connection on one surface is repeated, and flat plates made of activated carbon electrode material and flat plates made of ceramic powder are alternately laminated. In addition, the flat plate made of the ceramic powder is vertically connected in a zigzag manner, and the flat plate made of the activated carbon electrode material is formed in a layered structure so that the flat plate is vertically connected. By firing in an atmosphere to carbonize and activate the binder in the flat plate made of the activated carbon electrode material to make it porous, at the same time, from the ceramic powder Sintering the flat plate to make it porous, impregnating the porous body with an electrolyte solution, storing the laminate impregnated with the electrolyte solution in the gasket, and collecting the current. The method for manufacturing an electric double layer capacitor according to claim 1, further comprising the step of encapsulating the body.