JP2005317764A - Electric double-layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric double-layer capacitor in which internal resistance is reduced without increasing an area in the electric double-layer capacitor structured such that a planar capacitor element is sealed by using an exterior material for which metal foil and a polymeric material layer are laminated. <P>SOLUTION: By executing corrugating work or embossing work to the capacitor element 10; a recessed and projected structure is imparted, the opposing area of a positive pole electrode body 12a and a negative pole electrode body 12b is increased, the internal resistance is reduced, and the characteristics of the electric double-layer capacitor due to the internal resistance are improved. Also, by eliminating a part of the first polymeric material layer 14 and second polymeric material layer 16 of the exterior material 13, the metal foil 15 is electrically connected with a collector and turned to a terminal for external connection. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a capacitor element comprising a pair of positive and negative electrode bodies in which a polarizable electrode layer is formed on the surface of a current collector made of a conductor and a separator interposed between the positive and negative electrode bodies. The present invention relates to an electric double layer capacitor having a structure coated with a packaging material laminated with foil.

The electric double layer capacitor uses an electric double layer having a thickness of about several nanometers, which is formed at the interface between a charged solid and an electrolyte solution in contact therewith, as a dielectric. The capacity of the electric double layer is several tens of μF per 1 cm ² , but it is possible to obtain an extremely large capacity of several hundred to several thousand F by using activated carbon having a surface area of several thousand m ² as an electrode. is there.

The electric double layer capacitor has the following characteristics and is put into practical use, and studies for further performance improvement have been made.
(1) There is little deterioration of the capacity accompanying a charge / discharge cycle.
(2) Compared with a general battery, a large output can be taken out instantly after startup.

  Current electric double layer capacitors have various shapes such as a cylindrical shape and a coin shape depending on the application. Among them, when it is necessary to make it particularly thin, a polypropylene nonwoven fabric is formed between a pair of positive and negative electrode bodies in which a polarizable electrode layer mainly composed of activated carbon is formed on the surface of a current collector made of a sheet-like conductor. A capacitor element is formed by interposing a separator made of, etc., and the capacitor element is impregnated with an electrolytic solution and covered with an exterior material in which a polymer and a metal foil are laminated.

  Patent Document 1 discloses a technique related to an electric double layer capacitor having the above exterior structure. FIG. 4 is a diagram schematically showing a cross section of an example of an electric double layer capacitor according to a known technique disclosed in Patent Document 1. As shown in FIG.

  In FIG. 4, 41 is a separator, 42a is a positive polarizable electrode layer, 42b is a negative polarizable electrode layer, 43 is a current collector, 44 is a laminate film, and 45 is a window formed by perforating the laminate film. . The laminate film 44 used here is, for example, a laminate of polymer material layers on both sides of an aluminum foil, and the polymer material layer on the side in contact with the current collector 43 is composed of a thermoplastic polymer with high adhesiveness. The capacitor element can be sealed by heat-bonding the outer part of the capacitor element constituted by the separator 41, the positive polarizable electrode layer 42a and the negative polarizable electrode layer 42b by hot pressing.

  In the electric double layer capacitor shown here, a window 45 is provided in the laminate film 44 and a portion where the current collector is exposed is formed. Therefore, a terminal can be attached to this portion, and a current collector is separately provided. It is characteristic that there is no need to provide a terminal connected to the body.

Japanese Patent Laid-Open No. 2002-343681

  Generally, in an electric double layer capacitor, it is desired that the internal resistance is as small as possible for reasons such as suppressing a voltage drop during charging and discharging. In order to reduce the internal resistance, it is effective to increase the facing area between the positive electrode body and the negative electrode body constituted by the current collector and the polarizable electrode layer.

  However, in the thin electric double layer capacitor having the above-described structure, increasing the area of the electrode body immediately leads to an increase in area and size of the electric double layer capacitor itself. It has been a problem that the occupied area is large.

  Accordingly, an object of the present invention is to increase the internal resistance without increasing the area in an electric double layer capacitor having a structure in which a flat capacitor element is sealed using an exterior material in which a metal foil and a polymer material layer are laminated. It is to provide a reduced electric double layer capacitor.

  The present invention has been made by paying attention to the fact that the area of the joint surface when two flat members are joined increases by providing an uneven structure on the joint surface.

  That is, the present invention provides a positive electrode body and a negative electrode body formed by forming a polarizable electrode layer on the surface of a current collector made of a sheet-like conductor, with the polarizable electrode layer facing each other with a separator interposed therebetween. In an electric double layer capacitor having a structure in which a capacitor element formed by coating a metal foil on both sides of a multilayer material with a polymer material layer formed thereon, the capacitor element is provided with an uneven structure by bending. It is an electric double layer capacitor characterized by being formed.

  The present invention is the above electric double layer capacitor, wherein the bending process is a corrugated process.

  The present invention is the above electric double layer capacitor, wherein the bending is embossing.

  Further, the present invention provides the first polymeric material layer, wherein the first polymeric material layer is the side contacting the capacitor element and the second polymeric material layer is the opposite side of the polymeric material layer. Is a thermoplastic polymer, provided at least in part with a first open portion where the metal foil is exposed, and a connection portion is formed to ensure electrical connection between the current collector and the metal foil, In addition, a second open portion where the metal foil is exposed is provided on at least a part of the second polymer material layer, and the metal foil of the second open portion forms a connection terminal. The electric double layer capacitor described above is characterized.

  In the electric double layer capacitor according to the present invention, the capacitor element is provided with an uneven structure by corrugating or embossing, so that the area of the interface between the current collector and the polarizable electrode is larger than in the case of a flat structure. Is getting bigger. Along with this, the internal resistance is reduced, and the characteristics of the electric double layer capacitor as a whole are improved.

  In addition, corrugation and embossing for imparting a concavo-convex structure can be easily performed using a general shaping machine such as a roll or a press, so that the manufacturing cost is not greatly increased. This is also a feature of the present invention.

  Furthermore, in the electric double layer capacitor of the present invention, a portion electrically connected to the current collector is formed on at least a part of the metal foil constituting the exterior material, and the polymer material layer formed on the outside is formed. By removing a part, a portion where the metal foil is exposed to the outside can be formed, and the exposed portion can be used as a terminal for connecting the electric double layer capacitor to an external circuit.

  Next, embodiments of the present invention will be described with reference to the drawings.

  First, an example of corrugating will be shown. FIG. 1 is a diagram schematically showing a cross section of an electric double layer capacitor subjected to corrugation processing according to the first embodiment of the present invention. In FIG. 1, 10 is a capacitor element, 11 is a separator, 12a is a positive electrode body, and 12b is a negative electrode body. For the positive electrode body 12a and the negative electrode body 12b, for example, a conductive auxiliary agent typified by ketjen black and a binder typified by polytetrafluoroethylene are added to the activated carbon powder on the surface of a current collector made of aluminum foil. It is obtained by forming a polarizable electrode layer by film-forming the kneaded mixture.

  The separator 11 is a porous film made of a polymer material having chemical resistance typified by polyolefin. Then, with the polarizable electrode layer side of the positive electrode body 12a and the negative electrode body 12b facing each other, the separator 11 is disposed and bonded therebetween, whereby the capacitor element 10 is obtained. The capacitor element 10 is impregnated with an electrolytic solution, but a conventional electrolytic solution typified by a propylene carbonate solution of tetraethylammonium tetrafluoroborate is used.

  In FIG. 1, reference numeral 13 denotes an exterior material, which has a configuration in which a first polymer material layer 14 and a second polymer material layer 16 are laminated on both surfaces of a metal foil 15. The first polymer material layer 14 on the side in contact with the capacitor element 10 is made of a thermoplastic polymer rich in adhesiveness. Therefore, the capacitor element can be sealed by heat-sealing the portion extended from the outer edge (not shown) of the capacitor element 10 by heat pressing or ultrasonic heating.

  Specifically, for example, aluminum is used for the metal foil, ethylene-vinyl acetate copolymer is used for the first polymer material layer 14, and polyethylene terephthalate is used for the second polymer material layer 16, for example. Can be used. Of course, the material is not limited to these as long as it has the same characteristics as those of these materials.

  Thus, after sealing a capacitor element with an exterior material, corrugation processing can be performed by a method such as passing between twin rolls with grooves provided on the surface, and a corrugated shape can be imparted to the cross section.

  Moreover, in FIG. 1, 17a is a connection part of metal foil and a positive electrode body, 17b is a connection part of metal foil and a negative electrode body. As shown here, in the exterior material 13 used in the present invention, the outer edge portion of the first polymer material layer 14 is shortened, or an open portion is provided at an appropriate location, so that the current collector and A portion where the metal foil 15 is electrically connected can be provided. Thus, if the metal foil and the current collector are electrically connected, the metal foil of the exterior material can be used as a terminal for connecting the electric double layer capacitor to an external circuit or the like.

  FIG. 2 is a cross-sectional view schematically showing an example in which a terminal is formed using a metal foil. In FIG. 2, 20 is a capacitor element, 21 is a separator, 22a is a positive polarizable electrode layer, 22b is a negative polarizable electrode layer, 23a is a positive current collector, 23b is a negative current collector, and 24 is a first polymer. The material layer, 25a is a positive electrode metal foil, 25b is a negative electrode metal foil, 26 is a second polymer material layer, 27a is a positive electrode side connection portion, 27b is a negative electrode side connection portion, 28a is a positive electrode terminal, and 28b is a negative electrode terminal. .

  As shown here, an appropriate portion of the first polymer material layer 24 is perforated to form an open portion, and the positive electrode side connection portion 27a in which the positive electrode current collector 23a and the positive electrode metal foil 25a are in direct contact with each other. The positive electrode terminal 28a can be formed by removing the required portion of the second polymer material layer 26. Similarly, the negative electrode terminal 28b can be formed on the negative electrode side.

  In addition, here, an example in which the terminal is formed on the outer edge portion of the electric double layer capacitor has been shown. However, it is also possible to form the terminal in another location, and the connection portion between the current collector and the metal foil is, for example, The area of one polymer material layer can be made smaller than that of the metal foil and formed on the outer edge.

  Next, an example of embossing is shown. FIG. 3 is a diagram showing an example of an embossed electric double layer capacitor according to the second embodiment of the present invention, in which FIG. 3 (a) is a plan view and FIG. 3 (b) is FIG. It is the figure which showed typically the AA cross section in (a). In addition, since the process until embossing is the same as that of 1st embodiment, description is abbreviate | omitted.

  In FIG. 3, 30 is a capacitor element, 31 is a separator, 32a is a positive electrode body, 32b is a negative electrode body, 33 is an exterior material, 34 is a first polymer material layer, 35 is a metal foil, and 36 is a second electrode. A polymer material layer, 37a is a positive electrode side connecting portion, 37b is a negative electrode side connecting portion, 38 is a convex portion, and 39 is a concave portion.

  Here, as shown in the figure, circular embossing is regularly applied, but irregular irregularities can be provided irregularly. The depth of the irregularities is not particularly limited as long as the capacitor element is not broken.

  Embossing is usually carried out by passing an electric double layer capacitor between twin rolls having irregularities on the surface. Generally, it is carried out by passing between a metal embossing roll having an embossed pattern on the surface and a roll made of a relatively soft material such as paper or urethane rubber. Alternatively, it can be performed by pressing with a mold having an uneven structure.

  Since the terminal formation method in this case is not particularly different from that of the first embodiment, the description thereof is omitted. In the above example, the corrugating process and the embossing process are performed on the electric double layer capacitor sealed with the exterior material. However, the same effect can be obtained even if the process is performed only on the capacitor element. .

  Next, 50 electrical double layer capacitors each subjected to corrugation and embossing were prepared, and the electrode body area and electrical characteristics were measured. At that time, as a comparative example, the same evaluation was performed for an electric double layer capacitor that does not have an uneven structure. Table 1 summarizes the average values of the measurement results. The numerical values shown in Table 1 are relative values with the comparative example as 100.

  As shown in Table 1, in the electric double layer capacitor by any processing method, an increase in the electrode body area was observed, and accordingly, all of the equivalent series resistance, internal resistance, and capacitance were improved as compared with the comparative example. did. From this result, it is clear that the present invention contributes to the improvement of the characteristics of the electric double layer capacitor.

The figure which showed typically the cross section of the electric double layer capacitor which gave the corrugated process. Sectional drawing which showed typically the example which forms a terminal using metal foil. The figure which shows the example of the electrical double layer capacitor which gave embossing. FIG. 3A is a plan view. FIG. 3B is a diagram schematically showing an AA cross section in FIG. The figure which shows typically the cross section of an example of an electrical double layer capacitor by a well-known technique.

Explanation of symbols

10, 20, 30 Capacitor elements 11, 21, 31, 41 Separator 12a, 32a Positive electrode body 12b, 32b Negative electrode body 13, 33 Exterior materials 14, 24, 34 First polymer material layer 15, 35 Metal foil 16 , 26, 36 Second polymer material layer 17a Metal foil-positive electrode body connection portion 17b Metal foil-negative electrode body connection portion 22a, 42a Positive polarizable electrode layers 22b, 42b Negative polarizable electrode layer 23a Positive electrode collection Electrode 23b Negative electrode current collector 25a Positive electrode metal foil 25b Negative electrode metal foils 27a, 37a Positive electrode side connection portions 27b, 37b Negative electrode side connection portion 28a Positive electrode terminal 28b Negative electrode terminal 38 Convex portion 39 Concave portion 43 Current collector 44 Laminating film 45 Window

Claims (4)

  A capacitor formed by forming a polarizable electrode layer on the surface of a current collector made of a sheet-like conductor, and arranging a positive electrode body and a negative electrode body with the polarizable electrode layer facing each other with a separator interposed therebetween In the electric double layer capacitor having a structure in which the element is covered with an outer packaging material in which a polymer material layer is formed on both sides of a metal foil, the capacitor element is provided with an uneven structure by bending. Electric double layer capacitor.   The electric double layer capacitor according to claim 1, wherein the bending process is a corrugating process.   The electric double layer capacitor according to claim 1, wherein the bending process is an embossing process.   In the polymer material layer, when the first polymer material layer is the side in contact with the capacitor element and the opposite side is the second polymer material layer, the first polymer material layer is a thermoplastic polymer. A first open part where the metal foil is exposed is provided at least in part, and a connection part for securing an electrical connection between the current collector and the metal foil is formed, and the second The second open portion where the metal foil is exposed is provided in at least a part of the polymer material layer, and the metal foil of the second open portion forms a connection terminal. The electric double layer capacitor according to any one of claims 1 to 3.

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