JP3422406B2 - Electric double layer capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric double layer capacitor, and more particularly, to a plurality of capacitor elements connected in series in an outer shell case made of synthetic resin. The present invention relates to an electric double layer capacitor. [0002] When a solid surface comes into contact with an electrolyte solution, selective adsorption of positive or negative ions on the solid surface occurs,
While the solid surface is charged positively or negatively, counter ions of opposite charges increase on the solution side, and an electric double layer in which positive and negative charges are arranged opposite to each other is formed at the interface between the solid surface and the electrolyte solution. It is known that the electric double layer can be used as a capacitor by using the solid surface as a solid electrode, and such a capacitor is called an electric double layer capacitor. In the electric double layer capacitor, the capacitance when an electric field is applied to the solid electrode is proportional to the surface area of the solid electrode. Therefore, in general, a material having a large specific surface area such as activated carbon is used as the solid electrode. This is impregnated with an electrolytic solution, separated by a separator, and a current collecting member is attached to each of the solid electrodes on both sides of the separator. The electric double layer capacitor has a farad class large capacity and is excellent in charge / discharge cycle characteristics, and is therefore used for applications such as a backup power supply for electric equipment. It has been studied to use it as an in-vehicle battery by increasing the voltage and energy by connecting to a battery. As an electric double layer capacitor in which a plurality of capacitor elements are connected in series, for example, Japanese Patent Application Laid-Open No. 4-206
No. 809 is disclosed. The electric double layer capacitor described in the above publication has a plurality of capacitor elements connected in series accommodated in a metal outer case. However, as in the electric double layer capacitor described in the above publication, there is a problem that when the outer case is made of metal and the electric double layer capacitor is further enlarged, the weight of the outer case itself increases. Further, when the electric double layer capacitor is mounted on a vehicle, it is desired that the shape is adjusted to the place where the electric double layer capacitor is mounted. However, the metal outer shell case has low moldability and a desired shape may not be obtained. is there. Therefore, in order to reduce the weight of the electric double layer capacitor and improve the moldability of the outer shell case, a plurality of capacitor elements connected in series as described in Japanese Utility Model Laid-Open No. 6-55238, for example. May be housed in a synthetic resin outer case. The electric double-layer capacitor described in the above publication is a synthetic resin gasket provided with a plurality of steps having a smaller diameter toward the lower side on the inner surface as an outer shell case, in which a plurality of capacitor elements are sequentially accommodated from the smaller diameter one. is there. However, in the electric double layer capacitor described in the above publication, since the capacitor element is directly accommodated in the synthetic resin gasket, the electrolytic solution of the capacitor element contacts the gasket and corrodes the synthetic resin. There is a fear. Further, in the electric double-layer capacitor described in the above publication, since the step is provided on the inner surface side of the synthetic resin gasket, there is a disadvantage that a space that should be originally used for accommodating the capacitor element cannot be effectively used. SUMMARY OF THE INVENTION An object of the present invention is to provide an electric double layer capacitor which is excellent in durability, is small in size, and can be easily operated at high voltage and high energy. I do. In order to achieve the above object, an electric double layer capacitor according to the present invention comprises a plurality of serially connected capacitor elements housed in an outer shell case made of synthetic resin. In the electric double layer capacitor, each capacitor element is made of a conductive material having corrosion resistance to an electrolytic solution and is housed in a bottomed cylindrical element case having one end as an open end, and the element case is insulated. The capacitor element is laminated by interposing the material, and the opening end of one element case is closed with the bottom of the other element case to seal the capacitor element, and one of the capacitor elements housed in the element case is sealed. An electrode and the other electrode of the capacitor element adjacent to the capacitor element via the bottom of the element case are connected in series via the element case. In the electric double layer capacitor according to the present invention, the capacitor element is housed in an element case made of a material having corrosion resistance to an electrolytic solution, and the entire element case is housed in the outer case made of synthetic resin. The element case is a bottomed cylindrical shape having one end as an open end, and when a capacitor element is accommodated in the element case, the capacitor element is closed by closing the open end with the bottom of another element case. Sealed and laminated. As a result, the capacitor element is hermetically sealed by the element case accommodating itself and another element case for closing the opening end of the element case. The contact with the outer shell case can be prevented, and the durability of the outer shell case can be improved. Further, according to the electric double layer capacitor of the present invention, since a plurality of element cases having the same shape are stacked on each other and housed in the outer case, the inner volume of the outer case is effectively used. be able to. According to the present invention having the above structure, one electrode of the capacitor element is connected to the element case,
Since the other electrode is connected to another element case laminated on the element case via an insulating material, the element case itself made of a conductive material can be used as a connecting member between the capacitor elements, so that a simple configuration is provided. Thereby, a plurality of capacitor elements can be connected to each other in series, and the capacitor can be easily reduced in size with a large capacity. Next, an embodiment of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory sectional view showing the overall configuration of the electric double layer capacitor of the present invention, FIG. 2 is an explanatory sectional view showing a method for manufacturing the capacitor element shown in FIG. 1, and FIG. FIG. 3 is an explanatory cross-sectional view showing a configuration of the capacitor element and the element case of FIG. In the electric double layer capacitor according to the present embodiment, as shown in FIG. 1, an aluminum element case 2 for accommodating a capacitor element 1 is provided with an open end 2a of one element case 2.
Is closed by the bottom 2b of the other element case 2, thereby sealing the capacitor element 1 and being laminated via the packing 3 made of an insulating material attached to the open end 2a. Is housed. The outer shell case 4
A case main body 4a made of polypropylene resin and having an opening at the bottom, and a lid 4b for closing the bottom of the case main body 4a housing the element case 2, and a moisture blocking film 5a on its outer surface for preventing moisture from entering. , 5b are attached. In the electric double layer capacitor shown in FIG. 1, the opening end 2 of the uppermost element case 2 laminated as described above is formed.
a is closed by an end plate 7 laminated via the packing 3, and a socket 8 a penetrating through the case body 4 a is connected to the end plate 7. In the uppermost element case 2 stacked as described above, the socket 8b penetrating the lid 4b
Are connected to the bottom 2b of the element case 2. The electric double layer capacitor can be connected to an external circuit via sockets 8a and 8b. As shown in FIG. 2, the capacitor element 1 has long separators 9 impregnated with an electrolyte solution alternately folded in different directions at predetermined intervals, and the separators 9 are provided between the bellows-shaped separators 9. A plurality of electrode plates 10 are stacked so that different poles face each other with the separator 9 interposed therebetween. A flexible current collecting member 11 having substantially the same width as the electrode plate 10 is connected to an end of each electrode plate 10, and the current collecting member 11 is embedded over the entire length of the electrode plate 10. As a material for forming the separator 9, polyolefins such as polyethylene and polypropylene and polyolefins such as polyethylene and polypropylene are used because they are insoluble in organic solvents such as ester, ketone and ether used in ordinary secondary batteries. Any resin material that is commercially available as an ordinary filtration membrane, such as a resin comprising a copolymer of the above, polyamide, polycarbonate, aromatic polyamide, fluororesin, etc., can be used widely. The electrolyte solution impregnated in the separator 9 includes, for example, acetonitrile, propylene carbonate (PC), gamma-butyrolactone (GB)
L) and gamma valerolactone (GVL) in a solvent such as tetraethylammonium tetrafluoroboron salt (TEATFB)
And the like are used. The concentration of the electrolyte solution is, for example, when PCAT is used as a solvent and TEATFB is dissolved, the higher the concentration of TEATFB, the higher the conductivity is expected. However, in order to obtain stable solubility, the concentration is about 1 mol / liter. Is preferred. The concentration of the electrolyte solution may be 1 mol / liter or less, and the concentration of the electrolyte solution does not limit the characteristics of the electric double layer capacitor of the present invention. The electrode plate 10 is made of powdered, granular, fibrous, etc. activated carbon made of polytetrafluoroethylene (PTF).
E), cellulose, pullulan, gum arabic, PVA,
It is composed of a plate-like activated carbon or the like obtained by mixing with a binder such as PVDF, acrylic curdlan, or bulletin, and forming into a sheet or belt shape. Ketjen black, acetylene black,
Graphite, metal powder and the like can be appropriately mixed as a conductive agent. In addition, the electrode plate 10 may be made of fibrous activated carbon in a close shape. The activated carbon can be produced by carbonizing raw materials such as coconut shell, pitch, petroleum coke, phenol, and sawdust, and then activating with steam or KOH. In addition, as a raw material of the fibrous activated carbon, a phenol-based material is preferable from the viewpoint of, for example, ease of production when forming into a closed state. These activated carbons are 100
It has a specific surface area of ３3000 m ² / g. The flexible current collecting member 11 has a thickness of 0.0
An aluminum foil of about 1 to 0.1 mm is used. Current collecting member 11
As the material, aluminum or an aluminum-based metal such as an aluminum alloy is preferably used because it can operate in a wide voltage range, is lightweight, and has excellent workability. Although limited by the operating voltage, a metal such as nickel, titanium, copper, iron, or an alloy thereof can be used. In the capacitor element 1, as shown in FIG. 2, an electrode plate 10 provided with a current collecting member 11 is disposed on a separator 9 drawn from a coil 12, and the separator 9 is attached to the electrode plate 10. It can be easily manufactured by repeating the operation of folding back the electrode plate 10 at the tip and arranging the electrode plate 10 again on the folded separator 9. As shown in FIG. 3, one end of the capacitor element 1 manufactured as described above is wrapped by the separator 9 in which each electrode plate 10 is folded in a bellows shape as described above. The end that is not wrapped in the separator 9 is exposed on the side surface, and
1 is pulled out from between the separators 9 at the exposed end. Since the end portions of the respective electrode plates 10 are alternately exposed on the opposite side surfaces, the current collecting member 11 is pulled out to the same side with respect to the electrode plate 10 in a direction parallel to the electrode plate 10 for each same pole. Will be. As a result, the drawn out current collecting members 11 are grouped for each same pole and are welded to the current collecting plates 13a and 13b made of a conductive member. As shown in FIG. 3, the capacitor element 1 has a bottomed cylindrical element case 2 having an open end 2a at one end.
To be housed. Then, one current collecting plate 13a is attached to the bottom 2b of the element case 2, and the other current collecting plate 13b is exposed from the opening end 2a. In the electric double layer capacitor of the present embodiment,
As described above, the bottom 2b of one element case 2 closes the open end 2a of the other element case 2 to seal the capacitor element 1. At this time, the current collecting plate 11b exposed from the opening end 2a is connected to the bottom 2b of the element case 2 that closes the opening end 2a, so that the stacked capacitor elements 1, 1 are connected to the element case 2. Are connected in series. Note that the element case 2 has a packing 3 fitted to the upper end edge thereof, and by stacking via the packing 3, conduction between the stacked element cases 2 can be avoided. The material of the element case 2 may be any material as long as it has corrosion resistance to the electrolytic solution. Examples of the material include metals such as aluminum-based metals and SUS. Aluminum or an aluminum-based metal such as an aluminum alloy is preferred because of its superiority. Examples of the material of the outer shell case 4 include polyethylene resin and ABS resin in addition to the polypropylene resin. Further, moisture blocking films 5a, 5b attached to the outer surfaces of the case body 4a and the lid 4b.
Is for preventing external moisture from penetrating through the resin and entering the interior of the electric double layer capacitor, and is made of a metal or a material that does not transmit moisture. When the moisture barrier films 5a and 5b are formed of metal, arc spraying, plasma spraying, plating,
Physical vapor deposition, methods such as chemical vapor deposition can be used,
Arc spraying is preferred in terms of processing temperature. For the arc spraying, a low melting point metal such as aluminum, copper, tin, nickel, zinc, and lead can be used. However, the resin is thermally expanded so as to be hardly peeled off when attached to the case body 4a and the lid 4b. Aluminum is preferred because of its closeness and good compatibility with the electrolytic solution. In the electric double layer capacitor of the present embodiment, the moisture barrier films 5a and 5b are attached to the outer surfaces of the case body 4a and the lid 4b, but may be attached to the inner surface. Alternatively, it may be attached to both inside and outside surfaces. Further, an overmold layer made of a synthetic resin may be further provided outside the moisture blocking films 5a and 5b.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory sectional view showing the overall configuration of an electric double layer capacitor according to the present invention. FIG. 2 is an illustrative sectional view showing a method for manufacturing the capacitor element shown in FIG. FIG. 3 is an explanatory sectional view showing the configuration of the capacitor element and the element case shown in FIG. 1; [Description of Signs] 1 ... Capacitor element, 2 ... Element case, 2a ... Open end, 2b ... Bottom, 3 ... Insulating material, 4 ... Outer shell case.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 9/155

Claims (1)

(57) [Claims] [Claim 1] In an electric double layer capacitor in which a plurality of capacitor elements connected in series are housed in an outer shell case made of synthetic resin, each capacitor element is connected to an electrolyte. Conductive with corrosion resistance
Ri Do from sexual material, housed in <br/> element case is a bottomed cylindrical shape that one end and the open end, the element case, through the insulating material
The capacitor element is sealed by closing the opening end of one element case with the bottom of the other element case, and the capacitor element accommodated in the element case is sealed.
Of the element case and one electrode of the element
With the other electrode of the capacitor element adjacent via the bottom
Are connected in series via the element case .