ELECTRIC DOUBLE LAYER CAPACITOR AND MANUFACTURING METHOD THEREFOR

An electric double layer capacitor that includes a first electrode having a first polarizable electrode on a first collector electrode; a second electrode having a second polarizable electrode on a second collector electrode; and a separator interposed between the first polarizable electrode and the second polarizable electrode. The separator includes a bonding part filled with a resin. The bonding part extends to a surface of the separator closer to the first polarizable electrode, and the separator and the first polarizable electrode are bonded to each other by the bonding part.

FIELD OF THE INVENTION

The present invention relates to an electric double layer capacitor and a manufacturing method therefor.

BACKGROUND OF THE INVENTION

Conventionally, capacitors are widely used in various electronic devices such as mobile phones. Electric double layer capacitors (EDLC) are a known type of capacitor. Electric double layer capacitors have no chemical reaction upon charging and discharging, unlike secondary batteries, and thus have advantages such as having a long product life and being able to charge/discharge a large current in a short period of time. Accordingly, attempts have been made to apply electric double layer capacitors to intended uses which require a long product life, intended uses which require a large current, and the like.

For example, Patent Document 1 mentions an example of an electric double layer capacitor. For the electric double layer capacitor described in Patent Document 1, an electrode and a separator are integrated by applying an adhesive to the protruded surface of an electrode end and attaching a separator to that part.

SUMMARY OF THE INVENTION

When the separator is attached after applying the adhesive onto the electrode, an adhesive layer is formed between the electrode and the separator. Therefore, the electric double layer capacitor described in Patent Document 1 has an adhesive layer that bonds the electrode and the separator. For this reason, due to the presence of the adhesive layer, the electric double layer capacitor described in Patent Document 1 has a problem of difficulty reducing thickness.

A main object of the present invention is to provide a thin electric double layer capacitor.

An electric double layer capacitor according to the present invention includes a first electrode, a second electrode, and a separator. The first electrode has a first collector electrode and a first polarizable electrode. The first polarizable electrode is provided on the first collector electrode. The second electrode has a second collector electrode and a second polarizable electrode. The second polarizable electrode is provided on the second collector electrode. The separator is interposed between the first polarizable electrode and the second polarizable electrode. The separator is impregnated with an electrolyte. The separator is provided with a bonding part filled with a resin. The bonding part extends to a surface of the separator closer to the first polarizable electrode.

The separator and the first polarizable electrode are bonded to each other by the bonding part. In the electric double layer capacitor according to the present invention, the separator and the first polarizable electrode are bonded to each other by the bonding part composed of the resin filling the separator. For this reason, the gap can be reduced between the separator and the polarizable electrode, for example, as compared with a case of bonding the separator and the polarizable electrode with an adhesive layer provided between the separator and the polarizable electrode. Therefore, the thickness of the electric double layer capacitor can be reduced.

In the electric double layer capacitor according to the present invention, the separator and the first polarizable electrode preferably make contact with each other in a region provided with the bonding part. In this case, the thickness of the electric double layer capacitor can be further reduced.

In the electric double layer capacitor according to the present invention, the bonding part preferably extends to the surface closer to the second polarizable electrode, and the separator and the second polarizable electrode are bonded by the bonding part. In this case, it is not always necessary to provide an adhesive layer between the separator and the second polarizable electrode, and the thickness of the electric double layer capacitor can be reduced.

In the electric double layer capacitor according to the present invention, the entire surface of the separator closer to the first polarizable electrode preferably makes contact with the first polarizable electrode. In this case, the thickness of the electric double layer capacitor can be further reduced.

In the electric double layer capacitor according to the present invention, the bonding part preferably does not extend to the first collector electrode. In this case, the flow of the electrolyte, gas, or the like is less likely to be blocked by the bonding part, and the electric characteristics of the electric double layer capacitor is thus less likely to be deteriorated.

In the electric double layer capacitor according to the present invention, the first electrode has an opposed part that is opposed to the second electrode in the thickness direction, and a non-opposed part that is not opposed to the second electrode in the thickness direction, and the bonding part preferably bonds the non-opposed part and the separator to each other. In this case, the area of the opposed part which functions as a capacitor can be further increased, for example, as compared with a case of bonding the opposed part and the separator by the bonding part. Therefore, the capacitance of the electric double layer capacitor can be prevented from being decreased. In addition, the internal resistance of the electric double layer capacitor can be reduced.

In the electric double layer capacitor according to the present invention, the first electrode has an opposed part that is opposed to the second electrode in the thickness direction, and a non-opposed part that is not opposed to the second electrode in the thickness direction, and the bonding part is preferably provided to have an overlap with a central part of the opposed part. In this case, the gap between the first electrode and the second electrode is less likely to be increased. Therefore, the capacitance can be prevented from being decreased due to the increase in the gap between the first electrode and the second electrode. In addition, the internal resistance of the electric double layer capacitor is less likely to be increased.

In the electric double layer capacitor according to the present invention, the first electrode has an opposed part that is opposed to the second electrode in the thickness direction, and an extended part that is extended from the opposed part, and the opposed part has a rectangular shape with first and second sides extending in a first direction and third and fourth sides extending in a second direction perpendicular to the first direction, the extended part is extended from a part on one side with respect to the center of the opposed part in the second direction, and as viewed from the thickness direction, the bonding part is preferably provided such that at least a part of the bonding part has an overlap with a part located on the other side in the second direction with respect to the center of the opposed part in the second direction. In this case, the gap between the first electrode and the second electrode can be prevented in a more effective manner from being increased. Therefore, the capacitance can be prevented in a more effective manner from being decreased due to the increase in the gap between the first electrode and the second electrode. In addition, the internal resistance of the electric double layer capacitor can be prevented in a more effective manner from being increased.

In the electric double layer capacitor according to the present invention, the extended part is extended from a part on one side with respect to the center of the opposed part in the second direction and on one side with respect to the center thereof in the first direction, and as viewed from the thickness direction, the bonding part is preferably provided such that at least a part of the bonding part has an overlap with a part located on the other side in the second direction with respect to the center of the opposed part in the second direction and on the other side in the first direction with respect to the center thereof in the first direction. In this case, the gap between the first electrode and the second electrode can be prevented in a further effective manner from being increased. Therefore, the capacitance can be prevented in a further effective manner from being decreased due to the increase in the gap between the first electrode and the second electrode. In addition, the internal resistance of the electric double layer capacitor can be prevented in a further effective manner from being increased.

In the method for manufacturing the electric double layer capacitor according to the present invention, it is preferable to form the bonding part by impregnating the separator with an adhesive including a resin, after stacking the separator on the first polarizable electrode. The foregoing method can manufacture an electric double layer capacitor with the separator and the first polarizable electrode in contact with each other. In other words, an electric double layer capacitor can be manufactured, where there is substantially no gap between the separator and the first polarizable electrode. Therefore, high-capacitance electric double layer capacitors can be manufactured.

According to the present invention, a thin electric double layer capacitor can be provided.

DETAILED DESCRIPTION OF THE INVENTION

An example of a preferred embodiment of the present invention will be described below. However, the following embodiment is considered by way of example only. The present invention is not limited to the following embodiment in any way.

The drawings referenced in the embodiment and the like are schematically made. The ratios between the dimensions of objects drawn in the drawings, and the like may, in some cases, differ from the ratios between the dimensions of actual objects, or the like. The dimensional ratios of objects, and the like may differ between the drawings as well in some cases. The specific dimensional ratios of objects, and the like should be determined in view of the following description.

First Embodiment

FIG. 1is a schematic cross-sectional view of an electric double layer capacitor according to the present embodiment.FIG. 2is a schematic plan view of a main part of the electric double layer capacitor according to the present embodiment. InFIG. 2, the illustration of an exterior body10and a separator13is omitted.

As shown inFIG. 1, the electric double layer capacitor1includes a first electrode11, a second electrode12, a separator13, a bonding part14, and the exterior body10.

The first electrode11and the second electrode12are opposed to each other with the separator13interposed therebetween. Specifically, a plurality of first electrodes11and a plurality of second electrodes12are alternately stacked with separators13interposed therebetween. The respective first electrodes11are electrically connected by a first extension terminal (not shown), and extended to the exterior body10. The respective second electrodes12are electrically connected by a second extension terminal (not shown), and extended to the exterior body10.

The first electrode11includes a first collector electrode11a. The first collector electrode11acan be made of, for example, aluminum foil or the like. The thickness of the first collector electrode11acan be, for example, about 10 μm or more and 30 μm or less.

On the first collector electrode11a, a first polarizable electrode11bis provided. Specifically, among the second electrodes12and the first electrodes11, the first collector electrode11alocated outermost in the thickness direction (lamination direction) has the first polarizable electrodes11bprovided only on the inner principal surface, and no first polarizable electrodes11bprovided on the outer principal surface. In the case of the other first electrodes11, the first polarizable electrode11bis provided on both principal surfaces of the first collector electrodes11a. In other words, the first polarizable electrode11bis provided, among the principal surfaces of the first collector electrodes11a, only on the principal surfaces opposed to the second electrodes12. The thickness of the first polarizable electrode11bcan be, for example, about 10 μm or more and 30 μm or less.

As shown inFIG. 1andFIG. 4, the first electrode11has a rectangular opposed part11A, an extended part11B, and a non-opposed part11C. The opposed part11A is opposed to the second electrode12. As shown inFIG. 4, the opposed part11A has a first side11A1and a second side11A2extending in the y-axis direction (first direction). The opposed part11A has a third side11A3and a fourth side11A4extending along the x-axis direction (second direction). More specifically, the y-axis direction which is the first direction is a direction along the first and second sides11A1and11A2which are short sides. The x-axis direction which is the second direction is a direction along the third and fourth sides11A3,11A4which are long sides.

The extended part11B is connected to the opposed part11A. Specifically, according to the present embodiment, the extended part11B extends from a part of the opposed part11A on the y1 side in the y-axis direction perpendicular to the x-axis direction, to the x1 side. The non-opposed part11C is connected to the opposed part11A. The non-opposed part11C extends from the opposed part11A to the x2 side in the x-axis direction. The non-opposed part11C extends from a part of the opposed part11A on the y2 side in the y-axis direction, to the x2 side. The first polarizable electrode11bis provided only at the opposed part11A, and not provided at the extended part11B or the non-opposed part11C. The extended part11B and the non-extended part11C are composed of the first collector electrode11a.

According to the present embodiment, the plurality of extended parts11B is, for example, fixed by being integrated with, for example, a solder or the like. However, the plurality of extended parts11B may be fixed by being connected to a first extension terminal, not shown, without being integrated.

It is to be noted that according to the present embodiment, an example of providing the non-opposed part11C has been described, but the present invention is not limited to this configuration. For example, the first electrode may be composed of an opposed part and an extended part.

As shown inFIG. 1, the second electrode12includes a second collector electrode12a. The second collector electrode12acan be made of, for example, aluminum foil or the like. The thickness of the second collector electrode12acan be, for example, about 10 μm or more and 30 μm or less.

On the second collector electrode12a, a second polarizable electrode12bis provided. Specifically, among the second electrodes12and the first electrodes11, the second collector electrode12alocated outermost in the thickness direction (lamination direction) has the second polarizable electrodes12bprovided only on the inner principal surface, and no second polarizable electrodes12bprovided on the outer principal surface. In the case of the other second electrodes12, the second polarizable electrode12bis provided on both principal surfaces of the second collector electrodes12a. In other words, the second polarizable electrode12bis provided, among the principal surfaces of the second collector electrodes12a, only on the principal surfaces opposed to the first electrodes11. The thickness of the second polarizable electrode12bcan be, for example, about 10 μm or more and 30 μm or less.

As shown inFIG. 1andFIG. 5, the second electrode12has a rectangular opposed part12A, an extended part12B, and a non-opposed part12C. The opposed part12A is opposed to the first electrode11. The extended part12B is connected to the opposed part12A. Specifically, according to the present embodiment, the extended part12B extends from a part of the opposed part12A on the y2 side in the y-axis direction, to the x1 side. The non-opposed part12C is connected to the opposed part12A. The non-opposed part12C extends from the opposed part12A to the x2 side in the x-axis direction. Specifically, according to the present embodiment, the non-opposed part12C extends from a part of the opposed part12A on the y1 side in the y-axis direction, to the x2 side. The second polarizable electrode12bis provided only at the opposed part12A, and not provided at the extended part12B or the non-opposed part12C. The extended part12B and the non-extended part12C are composed of the second collector electrode12a.

According to the present embodiment, the plurality of extended parts12B is, for example, fixed by being integrated with, for example, a solder or the like. However, the plurality of extended parts12B may be fixed by being connected to a second extension terminal, not shown, without being integrated.

It is to be noted that according to the present embodiment, an example of providing the non-opposed part12C has been described, but the present invention is not limited to this configuration. For example, the second electrode may be composed of an opposed part and an extended part.

In addition, the first electrode11and the second electrode12may have the same size or different sizes.

The separator13is interposed between the first electrode11and second electrode12adjacent to each other. The separator13has substantially the same shape as the first electrode11and the second electrode12, or has a larger flat plate shape than the first electrode11and the second electrode12. The separator13separates the first electrode11and the second electrode12from each other. The separator13can be composed of, for example, a porous sheet with a plurality of open cells.

The first electrodes11, the second electrodes12, and the separators13are housed in the exterior body10. The first electrodes11are connected to a first extension terminal (not shown) provided outside the exterior body10. The second electrodes12are connected to a second extension terminal (not shown) provided outside the exterior body10. The exterior body10can be composed of, for example, a laminate sheet made of aluminum whose both surfaces are covered with a resin layer.

The electrolyte is interposed between the first electrode11and the second electrode12. Specifically, the separator interposed between the first polarizable electrode11bof the first electrode11and the second polarizable electrode12bof the second electrode12is impregnated with the electrolyte.

The electrolyte includes a cation, an anion, and a solvent. Preferably used cations include, for example, tetraethylammonium salts. Preferably used anions include, for example, tetrafluoroborate ions (BF4−) and bistrifluoromethylsulfonylimide ((CF3SO2)2N−). Preferably used solvents include carbonate compounds such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, nitrile compounds, and aqueous solvents such as water.

The electrolyte may be, for example, a crosslinkable gel electrolyte or an ionic liquid composed of an imidazole compound.

As shown inFIG. 1andFIG. 3, the separator13is provided with a bonding part14filled with a resin. The bonding part14extends to a surface of the separator13closer to the first polarizable electrode11b. The separator13and the first polarizable electrode11bare bonded to each other by the bonding part14. According to the present embodiment, the separator13and the first polarizable electrode11bmake contact with each other in the region provided with the bonding part14. For this reason, it is not always necessary to provide a bonding layer between the separator13and the first polarizable electrode11b. More specifically, the separator13can be attached to the first polarizable electrode11bwithout providing any bonding layer. Therefore, the gap can be reduced between the separator13and the first polarizable electrode11b. As a result, the gap can be reduced between the first electrode11and the second electrode12. Therefore, the thickness of the electric double layer capacitor1can be reduced.

From the viewpoint of further reducing the thickness of the electric double layer capacitor1, as shown inFIG. 3, it is preferable for the bonding part14to also extend to the surface closer to the second polarizable electrode12b, and for the bonding part14to connect the separator13and the second polarizable electrode12bto each other. In this case, it is not always necessary to provide a bonding layer between the separator13and the second polarizable electrode12b. More specifically, the separator13can be attached to the second polarizable electrode12bwithout providing any bonding layer. Therefore, the gap can be made smaller between the first polarizable electrode11band the second polarizable electrode12b. Therefore, the thickness of the electric double layer capacitor1can be further reduced.

From the same viewpoint, in the electric double layer capacitor1, the entire surface of the separator13closer to the first polarizable electrode preferably makes contact with the first polarizable electrode11b.

Now, from the viewpoint of firmly bonding the first electrode11and the separator13, the bonding part14is believed to be preferably provided so as to extend to the first collector electrode11a. However, as a result of earnest researches made by the inventors, it has been found that the electric characteristics of the electric double layer capacitor deteriorate when the bonding part is provided so as to extend to the collector electrode. From the viewpoint of suppressing the deterioration of electric characteristics of the electric double layer capacitor, the bonding portion14preferably does not extend to the first collector electrode11a. In this case, the flow of the electrolyte in the first polarizable electrode11b, and of the gas generated in the electric double layer capacitor1can be prevented from being blocked and interrupted by the bonding part14. For this reason, the internal resistance in the electric double layer capacitor1can be prevented from being increased.

The bonding part14may be provided at the opposed part11A or in the non-opposed part11C.

When the bonding part14is provided at the opposed part11A, the gap between the first electrode11and the second electrode12can be prevented in a more effective manner from being increased at the opposed part11A which functions as a capacitor. Therefore, the decrease in capacitance and the increase in internal resistance can be suppressed.

From the viewpoint of further effectively preventing the gap between the first electrode11and the second electrode12from being increased, the bonding part14is preferably provided so as to have an overlap with a central part of the opposed part11A as viewed from the thickness direction.

In addition, from the viewpoint of preventing the gap between the first electrode11and the second electrode12from being increased, the first electrode11and the second electrode12are preferably fixed at both one side and the other side in the x-axis direction which is a longitudinal direction. According to the present embodiment, the plurality of extended parts11B positioned on the x1 side in the x-axis direction is fixed, and the plurality of extended parts12B is fixed. For this reason, as shown inFIG. 2, the bonding part14is preferably provided such that at least a part of the bonding part14has an overlap with a region A (a hatched region inFIG. 2) located on the x2 side in the x-axis direction with respect to the center of the opposed part11A in the x-axis direction. Furthermore, in the present embodiment in which the extended part11B is provided on the y1 side in the y-axis direction, whereas the extended part12B is provided on the y2 side in the y-axis direction, the bonding portion14is preferably provided such that a part of the bonding part14has an overlap with a center line L extending in the x-axis direction through the center of the opposed part11A in the y-axis direction.

The area of the bonding part14is not particularly limited as long as it is enough to fix the separator13and the electrodes11,12with sufficient strength. From the viewpoint of firmly bonding the separator13and the electrodes11,12, the proportion of the area occupied by the bonding part14is preferably 1% or higher, more preferably 2% or higher, and further preferably 3% or higher at a part of the separator13opposed to the first polarizable electrode11b. However, if the proportion of the area occupied by the bonding part14is excessively high at the part of the separator13opposed to the first polarizable electrode11b, the capacitance of the electric double layer capacitor1may be decreased in some cases. Therefore, the proportion of the area occupied by the bonding part14is preferably 30% or lower, more preferably 20% or lower, and further preferably 10% or lower at the part of the separator13opposed to the first polarizable electrode11b.

The adhesive for use in the formation of the bonding part14is not particularly limited, but it is preferable to use a resin adhesive that is low in adhesiveness, electrolytic solution resistance, moisture resistance, or viscosity in a liquid state as a simple substance, or in an adjusted solution or dispersion state.

It is to be noted that an example in which the bonding part14is provided for each of the separators13has been described in the present embodiment. However, the present invention is not limited to this configuration. For example, each separator may be provided with a plurality of bonding parts.

(Method for Manufacturing Electric Double Layer Capacitor1)

FIGS. 6 to 11are schematic cross-sectional views illustrating a process for manufacturing the electric double layer capacitor1according to the present embodiment. An example of a method for manufacturing the electric double layer capacitor1according to the present embodiment will be described below with reference toFIGS. 6 to 11.

As shown inFIG. 6, the first or second polarizable electrode11b,12bis formed on the first or second collector electrode11a,12a. The polarizable electrodes11b,12bcan be formed by, for example, screen printing or the like.

Next, the separator13is stacked on the first or second polarizable electrode11b,12b. Thereafter, as shown inFIG. 7, a resin (adhesive) is applied from above the separator13to impregnate the separator13with the adhesive including the resin, thereby forming an adhesive impregnated part14a. Specifically, the separator13is impregnated with the adhesive including the resin, with the separator13and the first or second polarizable electrode11b,12bin close contact with each other.

Next, as shown inFIG. 8, the first or second collector electrode11a,12awith the first or first polarizable electrode11b,12bformed on both surfaces of the collector electrode is stacked on the separator13.

Next, as shown inFIG. 9, the separator13is stacked on the first or second polarizable electrode11b,12b. Thereafter, as shown inFIG. 10, the separator13is impregnated with the adhesive including the resin, thereby forming an adhesive impregnated portion14a.

The foregoing steps are repeated, and as shown inFIG. 11, the first or second collector electrode11a,12awith the first or second polarizable electrode11b,12bformed on one surface of the collector electrode is stacked on the separator13, thereby preparing a laminated body.

The prepared laminated body is pressed and thermocompression-bonded to form the bonding part14from the adhesive impregnated part14a. Next, the laminate is put in an exterior body. Thereafter, the electric double layer capacitor1can be fabricated by injecting an electrolyte into the exterior body and sealing the exterior pair.

As described above, the formation of the bonding part14through the impregnation with the resin, with the polarizable electrodes11b,12band the separator13stacked on one another, makes it possible to manufacture an electric double layer capacitor with the electrodes11,12and the separators in contact with each other in the region provided with the bonding part14.

It is to be noted that examples of the adhesive including the resin (resin adhesive) include, for example, an adhesive including a monomer, an oligomer, or the like for a resin that is cured by polymerization.

Other examples of preferred embodiments of the present invention will be described below. In the following description, members that have substantially the same functions as those in the first embodiment will be referred to with common reference numerals, and description thereof will be omitted.

Second Embodiment

FIG. 12is a schematic cross-sectional view of an electric double layer capacitor1aaccording to the second embodiment.FIG. 13is a schematic plan view of the main part of the electric double layer capacitor1aaccording to the second embodiment. InFIG. 13, the illustration of an exterior body10and the separator13is omitted.

In the first embodiment, an example in which the bonding part14is provided at the opposed part as viewed from the thickness direction has been described. However, the present invention is not limited thereto.

According to the second embodiment, a bonding part is provided at non-opposed parts11C and12C. In this case, it is not always necessary to provide the bonding part14at the opposed part11A, the effective area of the opposed part11A is thus not decreased. Therefore, the decrease in the capacitance of the electric double layer capacitor1, and the decrease in ESR can be prevented from being caused.

Third Embodiment

FIG. 14is a schematic plan view of an electric double layer capacitor1baccording to the present embodiment.

According to the present embodiment, the electric double layer capacitor1bincludes a first electric double layer capacitor element31aand a second electric double layer capacitor element31benclosed in a package31c. Each of the first and second electric double layer capacitor elements31aand31bhas a rectangular shape whose longitudinal direction is parallel to the x-axis direction (second direction). The first electric double layer capacitor element31aand the second electric double layer capacitor element31bare arranged in the x-axis direction. For this reason, the package31calso has a rectangular shape whose longitudinal direction is parallel to the x-axis direction.

The package31cis provided with a rectangular first cell31c1and a rectangular second cell31c2adjacent to the first cell31c1in the x-axis direction. The first electric double layer capacitor element31ais sealed in the first cell31c1. The second electric double layer capacitor element31bis sealed in the second cell31c2.

Each cell31c1,31c2is filled with an electrolytic solution. The electrolytic solution includes a cation, an anion, and a solvent. Preferably used cations include, for example, tetraethylammonium salts. Preferably used anions include, for example, tetrafluoroborate ions (BF4−) and bistrifluoromethylsulfonylimide ((CF3SO2)2N−). Preferably used solvents include carbonate compounds such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, nitrile compounds, and aqueous solvents such as water.

The electrolytic solution may be, for example, a crosslinkable gel electrolytic solution or an ionic liquid composed of an imidazole compound.

According to the present embodiment, the first electric double layer capacitor element31aand the second electric double layer capacitor element31bare composed of the same electric double layer capacitor element32.

FIG. 15shows a schematic cross-sectional view of a main part of the electric double layer capacitor element32. As shown inFIG. 15, the electric double layer capacitor element32includes a first electrode311, a second electrode312, and a separator313.

The first electrode311and the second electrode312are opposed to each other with the separator313interposed therebetween. Specifically, a plurality of first electrodes311and a plurality of second electrodes312are alternately stacked with separators313interposed therebetween.

The first electrode311includes a first collector electrode311a. The first collector electrode311acan be made of, for example, aluminum foil or the like. The thickness of the first collector electrode311acan be, for example, about 10 μm or more and 30 μm or less. On the first collector electrode311a, a first polarizable electrode311bis provided. Specifically, the first polarizable electrode311bis provided, among the principal surfaces of the first collector electrodes311a, only on the principal surfaces opposed to the second electrodes312. The thickness of the first polarizable electrode311bcan be, for example, about 10 μm or more and 30 μm or less. The first polarizable electrode311bcan be made of, for example, carbon or the like.

As shown inFIG. 16, the first electrode311has a rectangular first electrode main body (opposed part)311A. The first electrode main body311A is opposed to the second electrode312with the separator313interposed therebetween. From the corner on the x1 side of the first electrode main body311A in the x-axis direction (first direction) and on the y1 side thereof in the y-axis direction (first direction), a rectangular extended part311B is connected which extends toward the y1 side. On the other hand, a rectangular extended part311C extending toward the y1 side is connected from the corner on the x2 side of the first electrode main body311A in the x axis direction and on the y1 side thereof in the y-axis direction.

The second electrode312shown inFIGS. 14 and 15has a second collector electrode312a. The second collector electrode312acan be made of, for example, aluminum foil or the like. The thickness of the second collector electrode312acan be, for example, about 10 μm or more and 30 μm or less.

On the second collector electrode312a, a second polarizable electrode312bis provided. Specifically, the second polarizable electrode312bis provided, among the principal surfaces of the second collector electrodes312a, only on the principal surfaces opposed to the first electrodes311. The thickness of the second polarizable electrode312bcan be, for example, about 10 μm or more and 30 μm or less. The second polarizable electrode312bcan be made of, for example, carbon or the like.

As shown inFIG. 17, the second electrode312has a rectangular second electrode main body (opposed part)312A. The second electrode main body312A is opposed to the first electrode311with the separator313interposed therebetween. From the corner on the x1 side of the second electrode main body312A in the x-axis direction and on the y1 side thereof in the y-axis direction, a rectangular extended part312B is connected which extends toward the y1 side. On the other hand, a rectangular extended part312C extending toward the y1 side is connected from the corner on the x2 side of the second electrode main body312A in the x axis direction and on the y1 side thereof in the y-axis direction.

The first electrode311and the second electrode312adjacent to each other in the z-axis direction (thickness direction) are bonded to each other with a bonding part314.

As shown inFIG. 15, the separator313is provided between the first electrode311and the second electrode312adjacent to each other. The separator313has substantially the same shape as the first electrode311and the second electrode312, or has a larger flat plate shape than the first electrode311and the second electrode312. The separator313separates the first electrode311and the second electrode312from each other. The separator313can be composed of, for example, a porous sheet with a plurality of open cells. The separator313is impregnated with an electrolytic solution.

As shown inFIG. 14, in the first electric double layer capacitor element31a, the extended part311B of the first electrode311and the extended part312B of the second electrode312are positioned at the first corner31C1. The extended part312B is positioned more outside (x2 side) in the x-axis direction than the extended part311B. The extended part311C of the first electrode311and the extended part312C of the second electrode312are positioned at the second corner31C2. The extended part311C is positioned more inside (x1 side) in the x-axis direction than the extended part312C. The extended parts311B,312B are each integrally fixed.

In the second electric double layer capacitor element31b, the extended part311C of the first electrode311and the extended part312C of the second electrode312are positioned at the second corner31C2. The extended part311C is positioned more outside (x1 side) in the x-axis direction than the extended part312C. The extended part311B of the first electrode311and the extended part312B of the second electrode312are positioned at the first corner31C1. The extended part312B is positioned more inside (x2 side) in the x-axis direction than the extended part311B. The extended parts311C,312C are each integrally fixed.

The first electric double layer capacitor element31ahas a first electrode terminal315connected to the extended part311B of the first electrode311at the first corner31C1of the first cell31c1. The first electrode terminal315extends from the extended part311B toward the y1 side in the y-axis direction. The first electrode terminal315penetrates a sealing part31C3of the package31cto be extended even to the outside of the first cell31c1.

The first electric double layer capacitor element31ahas a second electrode terminal316connected to the extended part312B of the second electrode312at the first corner31C1of the first cell31c1. The second electrode terminal316extends from the extended part312B toward the y1 side in the y-axis direction. The second electrode terminal316penetrates a sealing part31C3of the package31cto be extended even to the outside of the first cell31c1.

The second electric double layer capacitor element31bhas a second electrode terminal317connected to the extended part312C of the second electrode312at the second corner31C2of the second cell31c2. The second electrode terminal317extends from the extended part312C toward the y1 side in the y-axis direction. The second electrode terminal317penetrates a sealing part31C3of the package31cto be extended even to the outside of the first cell31c1. The second electrode terminal317and the first electrode terminal315are electrically connected by a connecting material319.

The second electric double layer capacitor element31bhas a first electrode terminal318extending from the extended part311C of the first electrode311toward the y1 side in the y axis direction at the second corner31C2of the second cell31c2. The first electrode terminal318penetrates a sealing part31C3of the package31cto be extended even to the outside of the first cell31c1.

As shown inFIG. 15, the separator313is provided with a bonding part314filled with a resin. The bonding part314extends to a surface of the separator313closer to the first polarizable electrode311b. The separator313and the first polarizable electrode311bare bonded to each other by the bonding part314. Specifically, according to the present embodiment, the separator313and the first polarizable electrode311bmake contact with each other in the region provided with the bonding part314. For this reason, it is not always necessary to provide a bonding layer between the separator313and the first polarizable electrode311b. Therefore, the thickness of the electric double layer capacitor1bcan be reduced.

As described above, according to the present embodiment, in the first cell31c1, the multiple extended parts311B and312B stacked in the thickness direction are each fixed and integrated. The extended parts311B,312B are extended from the parts, on the x1 side of the rectangular opposed part311A which is a part of the first electrode311opposed to the second electrode312in the x-axis direction (the direction along the long side of the opposed part311A), and on the y1 side in the y-axis direction (the direction along the short side of the opposed part311A). In this case, as shown inFIG. 14, the bonding part314is preferably provided such that at least a part of the bonding part314has an overlap with a region located on the x2 side with respect to the center of the opposed part311A in the x-axis direction (second direction).

Alternatively, the bonding part314is preferably provided such that at least a part of the bonding part314has an overlap with a region located on the y2 side with respect to the center of the opposed part311A in the y-axis direction (first direction). In this case, the electrodes311,312and the separators313can be fixed at a plurality of spaced-apart sites. Therefore, the gap can be reduced between the electrode311and the electrode312. Therefore, the capacitance of the electric double layer capacitor1bcan be increased. In addition, the internal resistance of the electric double layer capacitor1bcan be reduced.

From the same point of view, the bonding part314is preferably provided such that at least a part thereof has an overlap with a part on the y2 side with respect to the center in the y-axis direction (first direction) and on the x2 side with respect to the center in the x-axis direction (second direction).

The adhesive for use in the formation of the bonding part314is not particularly limited, but it is preferable to use a resin adhesive that is low in adhesiveness, electrolytic solution resistance, moisture resistance, or viscosity in a liquid state as a simple substance, or in an adjusted solution or dispersion state.

It is to be noted that an example in which the opposed part311A and the separator313are bonded by the bonding part314has been described in the present embodiment, but the non-opposed part of the first electrode311and the separator313may be bonded by the bonding part314.

In the present embodiment, an example in which the bonding part14is provided for each of the separators13has been described. However, the present invention is not limited to this configuration. For example, each separator may be provided with a plurality of bonding parts.

It is to be noted that the electric double layer capacitor1baccording to the present embodiment can be manufactured, for example, by the same manufacturing method as the method for manufacturing the electric double layer capacitor1according to the first embodiment.

DESCRIPTION OF REFERENCE SYMBOLS