JP2019201110A - Electric double layer capacitor - Google Patents

Abstract

To provide an electric double layer capacitor that prevents alkalinization of an electrolyte and does not increase contact resistance between a tab terminal and a current collector.SOLUTION: An electric double layer capacitor includes a capacitor element having a pair of electrode bodies 23, a bottomed cylindrical metal case that houses the capacitor element, a sealing body that seals the opening of the metal case, and a tab terminal 10 bonded to each of the pair of electrode bodies 23 and extending to the outside of the sealing body through a terminal lead-out hole of the sealing body. The tab terminal 10 includes a penetrating portion 12 penetrating the sealing body and a flat portion 13 having a joint portion 14 with the electrode body 23. An insulating layer 15 is formed on the surface of the penetrating portion 12 and on the surface of a flat portion 13 excluding the joint portion 14 with the electrode body 23, and therefore the alkalinization of the electrolyte near the negative electrode tab terminal is prevented, and the contact resistance between the tab terminal 10 and the electrode body 23 is reduced.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electric double layer capacitor, and more particularly, to a wound electric double layer capacitor that reduces liquid leakage caused by a gap between a tab terminal and a sealing body.

  The electric double layer capacitor is a capacitor based on the principle of storing electricity in an electric double layer generated at the interface between the electrolyte and the electrode body.

  As an example, an electric double layer capacitor includes a capacitor element, an electrolytic solution impregnated in the capacitor element, a bottomed cylindrical metal case that houses the capacitor element together with the electrolytic solution, and an elastic material that seals an opening of the metal case. And a sealing body. Here, the capacitor element is configured by winding a current collector made of metal foil with a separator interposed between a pair of electrode bodies in which a polarizable electrode layer made of a carbon-containing porous material is formed. .

  A tab terminal having a flat portion, a penetrating portion, and a lead line is joined to each electrode body at at least one joining portion of the flat portion. The sealing body is provided with at least two terminal lead holes, and the through portions of the tab terminals are inserted into the terminal lead holes of the sealing body and led out to the outside, and the through portions of the tab terminals are sealed. The sealing performance is maintained in close contact with the inner wall of the terminal lead hole.

  In the electric double layer capacitor, the influence of moisture is significant as compared with the aluminum electrolytic capacitor. That is, when moisture enters the electric double layer capacitor, problems such as deterioration of life characteristics and case expansion due to gas generation occur. In particular, there is a problem of liquid leakage due to alkalinization of the electrolyte near the negative electrode side tab terminal due to water electrolysis.

  Patent Document 1 provides an electric double layer capacitor having a high energy density and a low internal resistance by using an electrolyte obtained by dissolving diethyldimethylammonium tetrafluoroborate, which is one of quaternary ammonium salts, in propylene carbonate. Is disclosed.

  In Patent Document 2, in an electric double layer capacitor using a quaternary ammonium salt electrolyte, a polyamide compound, which is an electrically insulating resin, is provided between a tab terminal and a terminal lead hole of a sealing body, and alkalized. It has been proposed to prevent the electrolyte solution from coming into contact with the terminal lead hole of the sealing body.

JP 2004-193508 A Japanese Patent No. 3405003

  In an electric double layer capacitor, when a voltage is applied in a high-temperature environment or a high-humidity environment, for example, a small amount of moisture originally present in the electric double layer capacitor or the electric double layer capacitor penetrates into the sealing body from the outside. Electrolysis of moisture that enters the inside of the battery or moisture that may enter from between the tab terminal and the sealing body from the outside causes the electrolyte near the negative electrode side tab terminal to become alkaline and deteriorate the sealing body. There is a problem in that electrolyte leakage occurs due to erosion or erosion of the tab terminal.

  As described in Patent Document 2, liquid leakage is suppressed by forming an electrically insulating resin between the penetrating portion of the tab terminal penetrating the sealing body and the terminal lead hole of the sealing body. be able to. However, in order to further improve the reliability of the electric double layer capacitor, further improvement in the effect of preventing the deterioration of the sealing body and the tab terminal is required.

  On the other hand, when an electrically insulating resin is formed on the entire surface of the flat portion of the tab terminal of the electric double layer capacitor, the internal resistance of the electric double layer capacitor is increased due to an increase in contact resistance between the tab terminal and the electrode body. There is a problem of end.

  The present invention has been made in view of the circumstances as described above, and by minimizing the electrical contact between the tab terminal and the electrolyte, in the vicinity of the terminal lead hole of the sealing body and the penetrating portion of the tab terminal. An object of the present invention is to provide an electric double layer capacitor that prevents alkalinization of the electrolyte and does not increase the contact resistance between the tab terminal and the electrode body.

  In the first aspect of the present invention, a capacitor element in which a pair of electrode bodies each composed of a current collector and a polarizable electrode layer are wound through a separator and impregnated with an electrolytic solution, and the capacitor element is accommodated A bottomed cylindrical metal case, a sealing body that seals the opening of the metal case, and each of the pair of electrode bodies, and is extended to the outside of the sealing body through a terminal lead hole of the sealing body An electric double layer capacitor having a tab terminal, wherein the tab terminal includes a penetrating portion that penetrates the sealing body, and a flat portion having a joint portion with the electrode body. Provided is an electric double layer capacitor in which an insulating layer is formed on a surface and a surface of the flat portion excluding a joint portion with the electrode body.

  According to the present invention, even when a voltage is applied to the electric double layer capacitor, the alkaline solution of the electrolyte near the tab terminal is prevented, the deterioration of the tab terminal and the sealing body rubber due to the alkaline solution is prevented, A highly reliable electric double layer capacitor is provided.

It is sectional drawing which shows the structure of the electrical double layer capacitor which concerns on 1st Embodiment. The figure (a) which looked at the tab terminal and the electrode body from the side which joined the tab terminal, and the figure (b) seen from the opposite side are shown. It is sectional drawing which shows the junction part of a tab terminal and an electrode body. It is a figure which shows the example of the exclusion part by which the insulating layer is not formed in the surface of a tab terminal. It is a figure which shows the structure of the electrical double layer capacitor which concerns on 2nd Embodiment. It is a figure which shows the structure of the electric double layer capacitor of the modification of 2nd Embodiment. It is data which shows the result of a liquid leak evaluation test.

A preferred embodiment of an electric double layer capacitor according to the present invention will be described with reference to FIGS. 1 to 7.
(1) Outline of the embodiment

The electric double layer capacitor includes a capacitor element having a pair of electrode bodies 23, a bottomed cylindrical metal case that houses the capacitor elements, a sealing body that seals an opening of the metal case, and the pair of electrode bodies 23. A tab terminal 10 that extends through the terminal lead hole of the sealing body and extends to the outside of the sealing body, and the tab terminal 10 has a through-hole 12 that penetrates the sealing body, A flat portion 13 having a joint portion 14 with the electrode body 23, and an insulating layer 15 is formed on the surface of the through portion 12 and on the surface of the flat portion 13 excluding the joint portion 14 with the electrode body 23. By doing so, the alkaline solution of the electrolyte solution in the vicinity of the negative electrode tab terminal is prevented, and the contact resistance between the tab terminal 10 and the electrode body 23 is reduced.
(2) Details of the embodiment (first embodiment)

  FIG. 1 is a cross-sectional view showing the configuration of the electric double layer capacitor 1 according to the first embodiment. The electric double layer capacitor 1 includes tab terminals 10a and 10b, a capacitor element 20, a sealing body 30, a metal case 40, and the like. The capacitor element 20 impregnated with the electrolytic solution is housed in a bottomed cylindrical metal case 40 made of aluminum. The opening part of the metal case 40 is sealed by pressing and deforming the sealing body 30 made of elastic rubber from the lateral diaphragm part 41 and the upper diaphragm part 42.

  One end of each of the positive electrode tab terminal 10 a and the negative electrode tab terminal 10 b is joined to the positive electrode and the negative electrode of the capacitor element 20. The terminal lead hole 31 is a through hole provided in the sealing body 30. The tab terminals 10 a and 10 b pass through the terminal lead hole 31, and the other end extends to the outside of the electric double layer capacitor 1. The tab terminals 10a and 10b are terminals that connect the positive electrode and the negative electrode of the capacitor element 20 to an external circuit.

  The insulating layer 15 is formed between the penetrating portion 12 which is a part of the tab terminals 10a and 10b and the inner surface of the terminal lead hole 31 and on the surface of the tab terminals 10a and 10b joined to the capacitor element 20. An insulating layer 15 is shown. The insulating layer 15 formed on the tab terminals 10a and 10b joined to the capacitor element 20 will be described in detail later with reference to FIGS.

  These insulating layers 15 are formed for the following purposes, for example. That is, the gap between the tab terminals 10a, 10b and the terminal lead-out hole 31 is filled to improve the adhesion between the tab terminals 10a, 10b and the sealing body 30, and in the process of manufacturing the capacitor element 20, the capacitor element The purpose is to make it difficult for the electrolytic solution to adhere to the tab terminals 10a and 10b even when the electrolytic solution is impregnated into the tab 20, and to prevent moisture from the outside from entering the tab terminals 10a and 10b. .

  The insulating layer 15 is a layer that is insoluble in the electrolytic solution used in the electric double layer capacitor 1 and electrically insulates the tab terminal 10 from the electrolytic solution. When the insulating layer 15 is formed by covering the surface of the tab terminal 10 with an insulating resin, the insulating resin 15 is made of, for example, an epoxy resin, a polyamide resin, a polyimide resin, a polyethylene resin, a polypropylene resin, or a fluorine resin. Use. In addition to the insulating resin, the insulating layer 15 may be formed of a ceramic thin film, an electrically insulating oxide film, or the like that is insoluble in the electrolytic solution and has an electrical insulating property.

For example, when the insulating layer 15 is formed of an insulating resin, the thickness of the insulating layer 15 is preferably as follows. The thinner the insulating layer 15 is, the easier the insertion into the terminal lead hole 31 becomes. On the other hand, if the thickness is too thin, sufficient effects of the present invention may not be obtained. Therefore, for example, the thickness of the insulating layer 15 is set to 0.1 μm or more. The thickness of the insulating layer 15 is preferably 1 μm or more, more preferably 3 μm or more.
Further, the strength of the insulating layer 15 increases as the thickness thereof increases. On the other hand, if the thickness is too thick, the ease of insertion into the terminal lead hole 31 may be reduced. Therefore, for example, the thickness of the insulating layer 15 is set to 500 μm or less. The thickness of the insulating layer 15 is preferably 100 μm or less, more preferably 50 μm or less.

  The sealing body 30 is made of a substance having a predetermined flexibility as well as chemical resistance and electrical insulation with respect to the electrolytic solution. The sealing body 30 is made of, for example, butyl rubber, ethylene propylene rubber, or the like.

  FIG. 2 shows a view (a) of the electrode body 23 of the capacitor element 20 as viewed from the side where the tab terminal 10 is joined, and a view (b) as viewed from the opposite side. The electrode body 23 of the capacitor element 20 in the electric double layer capacitor 1 includes a current collector 21 made of aluminum foil for both the positive electrode and the negative electrode, and a carbon-containing porous material formed on the surface of the aluminum foil of the current collector 21. It is comprised from the polarizable electrode layer 22 which consists of (activated carbon material). The capacitor element 20 is formed by impregnating an electrolytic solution in a state in which a polarizable electrode layer 22 on the positive electrode side and a polarizable electrode layer 22 on the negative electrode side are opposed to each other with a separator interposed therebetween.

  As the electrolytic solution, for example, an electrolytic solution in which an electrolyte composed of a quaternary ammonium salt, an amidine salt, or the like is dissolved in a predetermined solvent is used. The cation of the quaternary ammonium salt is, for example, any one of triethylmethylammonium cation, ethyltrimethylammonium cation, diethyldimethylammonium cation, tetraethylammonium cation, 5-azoniaspiro [4.4] nonane cation, or the like. A combination of multiple cations is used. Examples of the cation of the amidine salt include 1,2,3,4-tetramethylimidazolinium cation, 1-ethyl-2,3-dimethylimidazolinium cation, 1-ethyl-3-methylimidazolium cation, 1- Any one of ethyl-2,3-dimethylimidazolium cation or the like or a combination of a plurality of these cations is used.

  As the anion in the electrolyte, for example, any one of tetrafluoroborate anion, hexafluorophosphate anion, or a combination of these anions is used. As the solvent for dissolving the electrolyte, for example, any one of acetonitrile, propylene carbonate, ethylene carbonate, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, or a combination thereof is used.

  Both the positive electrode and the negative electrode of the capacitor element 20 have an electrode body 23 composed of a current collector 21 and a polarizable electrode layer 22, and are joined to tab terminals 10a and 10b having substantially the same shape. In the following description, the tab terminal 10 will be described without distinguishing between the positive electrode tab terminal 10 a bonded to the positive electrode body 23 and the negative electrode tab terminal 10 b bonded to the negative electrode body 23.

  The tab terminal 10 includes a through portion 12 made of aluminum, a lead wire 11 welded to the through portion 12, and a flat portion 13 obtained by processing the through portion 12 into a flat shape. A part of the flat portion 13 is joined to the electrode body 23 of the capacitor element 20. The through portion 12 is a portion that penetrates the terminal lead hole 31 of the sealing body 30. The lead wire 11 is a conducting wire made of a CP-coated copper wire, for example. The surface of the lead wire 11 may be subjected to solder plating or tin plating.

  In FIG. 2, the lead wire 11 and the penetrating portion 12 are welded. However, the present invention is not limited to this. For example, the lead wire 11 and the penetration part 12 may be pressure-bonded, may be cast as an integral object, or may be cut from one metal body. Moreover, the lead wire 11 is not limited to the conducting wire which consists of CP wire etc. of a copper covering steel wire. For example, the lead wire 11 may be a screw terminal type metal terminal. In FIG. 2, the flat portion 13 has a shape in which the penetrating portion 12 is processed into a flat shape, but is not limited thereto. For example, the flat portion 13 made of a strip-shaped metal member may be welded to the through portion 12.

  The insulating layer 15 is formed so as to cover not only the through portion 12 of the tab terminal 10 but also the surface of the flat portion 13. However, as will be shown later, in order to reduce the contact resistance between the tab terminal 10 and the electrode body 23 and to obtain good conductivity therebetween, an insulating layer is formed on a part of the surface of the flat portion 13. 15 is not formed. That is, the insulating layer 15 is not formed on the surface of the flat portion 13 and in a predetermined range including the bonding portion 14 between the flat portion 13 and the electrode body 23 or the bonding portion 14. In the example of FIG. 2, the insulating layer 15 is formed on the flat portion 13 in the portion from one third to one half of the length of the flat portion 13 on the upper side of the drawing near the penetrating portion 12. However, an example is shown in which the insulating layer 15 is not formed in a portion from the two-thirds to one-half of the length of the flat portion 13 on the lower side of the drawing, which is far from the penetration portion 12.

  For the purpose of preventing the surface of the flat portion 13 from contacting the electrolytic solution, it is best to form the insulating layer 15 on the entire surface of the flat portion 13 in order to form the insulating layer 15 of the flat portion 13. In order to improve the efficiency of the process of forming the insulating layer 15 while maintaining the conductivity between the flat portion 13 and the electrode body 23, the formation range of the insulating layer 15 can be selected within a certain range. In that case, for example, the flat portion 13 is formed from the processing method of forming the insulating layer 15 on the surface of the flat portion 13 except for the joint portion 14 with the electrode body 23 or the electrode body 23 of the wound capacitor element 20. An insulating layer is formed on the surface of the flat portion 13 in the range protruding in the direction of the sealing body 30 (that is, the range in which the flat portion 13 protrudes from the upper side 212 of the current collector 21 toward the penetrating portion 12 in FIG. 2A). 15 may be used.

  The joint 14 between the flat portion 13 of the tab terminal 10 and the electrode body 23 of the capacitor element 20 is formed by caulking, a cold weld method, an ultrasonic method, or the like. For example, in the case of caulking, the joining portion 14 is formed by superposing the flat portion 13 on the aluminum foil of the current collector 21 constituting the electrode body 23, and then from the surface side of the flat portion 13 (from the front side of the paper surface of FIG. 2A). ) A needle is pierced, and the flat portion 13 and the aluminum foil of the electrode body 23 are protruded together to the polarizable electrode layer 22 side (the front side of the drawing in FIG. 2B). The joining portion 14 has a force so as to sandwich and crush it together with the aluminum foil of the flat portion 13 and the electrode body 23 from the direction perpendicular to the paper surface of FIG. 2 while expanding the tip portion projected to the polarizable electrode layer 22 side. To be joined. FIG. 2 shows an example in which the needle holes are joined by caulking in which needle holes remain in three places. The joint portion 14 is formed such that the flat portion 13 and the electrode body 23 are fixed to each other, and the contact resistance therebetween is sufficiently reduced.

  When electric charge is accumulated in the electric double layer capacitor 1 having the above configuration, a charging voltage of, for example, approximately 2.5 V is applied between the positive side tab terminal 10a and the negative side tab terminal 10b. The electrode bodies 23 on the positive electrode side and the negative electrode side of the capacitor element 20 connected to the tab terminal 10 attract the anions and cations of the electrolyte dissolved in the solvent, respectively. These attracted electrolyte ions gather on the positive electrode side and the negative electrode side in the very vicinity of the surface of the porous polarizable electrode layer 22 with their polarization directions substantially matched. The electric double layer capacitor 1 is a capacitor having a large capacitance due to the short distance between the polarizable electrode layer 22 and the electrolyte ions and the large surface area of the polarizable electrode layer 22 made of activated carbon. It becomes.

The conventional electric double layer capacitor has the following problems related to moisture in the electrolyte. When a voltage is applied to the conventional electric double layer capacitor and the voltage of the tab terminal 10 or the electrode body 23 becomes equal to or higher than the water electrolysis voltage, the water contained in the electrolytic solution is electrolyzed, and hydroxide ions OH ⁻ Will occur. The generated hydroxide ion OH ⁻ alkalizes the electrolyte near the negative electrode side tab terminal 10. This electrolytic solution may corrode aluminum constituting the tab terminal 10 or deteriorate the rubber of the sealing body 30, which causes liquid leakage.

On the other hand, in the case of the electric double layer capacitor 1 of the present embodiment, the tab terminal 10 is covered with the insulating layer 15 in the range of the flat portion 13 close to the through portion 12 as well as the through portion 12. Since the surface is covered with the insulating layer 15, even if a voltage is applied to the electric double layer capacitor 1 and the voltage of the tab terminal 10 becomes equal to or higher than the electrolysis voltage of water, the through portion 12 and the through portion 12 The generation of hydroxide ions OH ⁻ is suppressed in the vicinity of the flat portion 13 close to. That is, this embodiment can prevent the alkalinization of the electrolytic solution, which is one of the causes of leakage of the electrolytic solution.

In order to prevent the deterioration of the rubber around the terminal lead hole 31 and the erosion to the tab terminal 10 due to the alkalinization of the electrolytic solution, at least the through part 12 of the negative electrode side tab terminal 10 and the flat part close to the through part 12 The insulating layer 15 may be formed on the surface 13. In the case of FIG. 2, the flat part 13 in the range of, for example, about two-thirds of the lower part of the flat part 13 away from the penetrating part 12 is not covered with the insulating layer 15, so in the vicinity of the flat part 13 in this range. Alkalineization of the electrolyte can occur. However, even if the electrolytic solution is alkalized in the vicinity of the flat portion 13 away from the penetration portion 12, the hydroxide ions OH ⁻ are present in the electrolytic solution before reaching the penetration portion 12 or the terminal extraction hole 31 of the sealing body 30. And the concentration of hydroxide ions OH ⁻ decreases. Therefore, even if the alkalinization of the electrolyte occurs in the vicinity of the flat part 13 away from the penetration part 12, the deterioration of the rubber around the terminal lead hole 31 of the sealing body 30 and the erosion of the tab terminal 10 on the penetration part 12 are caused by It hardly occurs.

  Further, conventionally, there is a technique for forming the insulating layer 15 in the gap between the terminal lead hole 31 of the sealing body 30 and the through portion 12 of the tab terminal 10. In this prior art, the alkalinization of the electrolytic solution itself is not prevented, but the alkaline electrolyte is brought into contact with the terminal lead hole 31 and the through-hole 12 by the insulating layer 15 formed in the gap between the terminal lead holes 31. It is intended to suppress. In contrast, in the present embodiment, the insulating layer 15 is formed not only on the surface of the penetrating part 12 but also on the surface of the flat part 13, thereby alkalizing the electrolyte near the penetrating part 12 and the terminal lead hole 31. This suppresses the deterioration of the sealing body 30 and the corrosion of the penetrating portion 12, and more fundamentally copes with the cause of leakage of the electrolyte.

  FIG. 3 is a cross-sectional view showing the AA ′ cross section of FIG. 2 and showing the joint portion 14 between the flat portion 13 of the tab terminal 10 and the electrode body 23 of the capacitor element 20. The same parts as those in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted. The joining part 14 of FIG. 3 shows an example in which the flat part 13 and the electrode body 23 including the current collector 21 and the polarizable electrode layer 22 are joined by caulking.

  Caulking joins the flat part 13 and the electrode body 23 by the following method, for example. After the flat portion 13 is overlaid on the aluminum foil of the current collector 21 constituting the electrode body 23, a needle is inserted from the surface side of the flat portion 13 (from the left side in FIG. 3), and the aluminum of the flat portion 13 and the electrode body 23. Together with the foil, it protrudes to the polarizable electrode layer 22 side (right side in FIG. 3). While spreading the tip portion protruding toward the polarizable electrode layer 22 side, pressure is applied to the aluminum foil of the flat portion 13 and the electrode body 23 such that the flat portion 13 and the electrode body 23 are crushed from the left and right directions in FIG. And join.

  The insulating layer 15 is not formed in advance in a predetermined range including the bonding portion 14 on the surface of the flat portion 13 facing the current collector 21 constituting the electrode body 23. The exclusion portion 16 in FIG. 3 shows a portion where the insulating layer 15 is not formed. Since the insulating layer 15 is not attached, the surface of the flat portion 13 is in direct contact with the aluminum foil of the current collector 21 when bonded. The joint portion 14 not only mechanically joins the flat portion 13 and the electrode body 23 but also realizes a joint having low contact resistance and sufficiently high conductivity between the flat portion 13 and the electrode body 23. .

  FIG. 4 shows an example of the exclusion portion 16 where the insulating layer 15 is not formed on the surface of the tab terminal 10 facing the current collector 21 with respect to the same arrangement of the joint portion 14 as in FIG. FIG. 4A shows an example in which the exclusion unit 16 is provided in the same range as in FIG. FIG. 4B shows an example in which an exclusion portion 16 is provided so as to include the joint portion 14 and surround the entire joint portion 14. FIG. 4C shows an example in which an exclusion portion 16 having a width of about 1.5 mm is provided for each of the three needle hole positions. For example, when the insulating layer 15 is formed by applying a resin, the exclusion portion 16 is formed by masking the exclusion portion 16 that is a part of the flat portion 13 in advance and applying a resin, and then removing the masking. The exclusion part 16 is formed.

4 (a), 4 (b) and 4 (c) all show a low contact resistance between the tab terminal 10 and the electrode body 23 after the flat portion 13 and the electrode body 23 are joined. It was possible to obtain sufficiently high conductivity. Moreover, since the exclusion part 16 is not covered with the insulating layer 15, the alkalinization of electrolyte solution can occur in the vicinity of this part. However, the hydroxide ions OH ⁻ generated in the vicinity of the exclusion portion 16 diffuse and decrease in concentration before reaching the penetration portion 12 or the terminal lead hole 31 of the sealing body 30. The alkalinization of the electrolyte hardly causes erosion of the through portion 12 and deterioration of the rubber around the terminal lead hole 31.

As described above, the electric double layer capacitor 1 according to the present embodiment prevents the alkalinization of the electrolytic solution by forming the insulating layer 15 in a predetermined range of the surface of the through portion 12 and the flat portion 13 constituting the tab terminal 10. Further, it is possible to prevent the deterioration of rubber around the terminal lead hole 31 and the erosion of the through portion 12 and the flat portion 13 due to alkalinization. Further, the insulating layer 15 is formed on the side close to the sealing body 30, for example, in the range of about one third of the length of the flat portion 13, and the exclusion portion 16 in which the insulating layer 15 is not formed on the other flat portions 13. By providing this, the contact resistance between the flat portion 13 and the electrode body 23 can be set to a sufficiently low value.
(Second Embodiment)

  FIG. 5 shows a configuration of the electric double layer capacitor according to the second embodiment. FIG. 6 shows a configuration of an electric double layer capacitor according to a modification of the second embodiment. As in the first embodiment, the tab terminal 10 of the electric double layer capacitor shown in FIGS. 5 and 6 has not only the penetration part 12 but also the surface of the flat part 13 covered with the insulating layer 15. 12 is prevented from being alkalized, which causes erosion of 12 and deterioration of the sealing body 30.

  The electric double layer capacitor shown in FIGS. 5 and 6 is different from the electric double layer capacitor 1 according to the first embodiment in the shape of the sealing body 30. FIG. 5A is a view of the sealing body 30 of the electric double layer capacitor according to the second embodiment as viewed from the capacitor element 20 side accommodated in the metal case 40 (see also FIG. 1). The sealing body 30 is provided with a protruding portion 32 that protrudes toward the capacitor element 20 in the same direction as the penetration direction of the terminal lead hole 31 of the sealing body 30. FIG. 5B shows an AA ′ cross section including the protrusion 32. FIG. 5C shows a BB ′ cross section including the protrusion 32. The height of the protrusion 32 (the length of the protrusion 32 in the penetrating direction of the terminal lead hole 31) is preferably 0.2 mm or more and 1.5 mm or less, for example.

  The protrusion 32 includes an elongated rectangular opening 33 that passes through the penetrating portion 12 of the tab terminal 10 and has a longitudinal direction in the diameter direction of the round hole, for example (see FIG. 5A )reference). The length and width of the rectangular opening 33 in the in-plane direction of FIG. 5A correspond to the lateral width and thickness of the flat portion 13 of the tab terminal 10. Accordingly, as can be seen from the cross-sectional views of FIGS. 5B and 5C and the plan view of FIG. 5A, when the tab terminal 10 is inserted into the sealing body 30, the rectangular opening 33 is formed into the tab terminal 10. The flat portion 13 is fixed so as to be sandwiched from the thickness direction of the flat portion.

  Since the protrusion 32 of the sealing body 30 has such an opening 33, at least the following effects can be expected. One effect is that when the flat portion 13 of the tab terminal 10 is fixed by the opening 33, the through portion 12 rotates around the central axis in the terminal lead hole 31 or moves in the through direction. It is an effect to prevent. When the penetrating part 12 moves in the terminal lead hole 31, a gap is generated between the insulating layer 15 formed on the surface of the penetrating part 12 and the terminal lead hole 31, and the electrolyte leaks from there. There can be. If the penetration part 12 is fixed to the sealing body 30, the leakage of the electrolyte solution due to the above factors can be prevented.

  Another effect is that the protrusion 32 is present between the capacitor element 20 and the sealing body 30, so that the distance between the capacitor element 20 impregnated with the electrolyte and the sealing body 30 is increased. is there. By widening this interval, it is difficult for leakage of the electrolyte due to the electrolyte to rise, and there is an effect of extending the time until the leakage of the electrolyte occurs. In order to obtain this effect more reliably, the height of the protruding portion 32 in the same direction as the penetrating direction of the terminal lead hole 31 is preferably 0.2 mm or more, and more preferably 0.5 mm or more. However, since the product size (height) of the electric double layer capacitor is increased and the commercial value may be impaired, the height of the protrusion 32 is preferably 1.5 mm or less, and more preferably 1 mm or less.

  FIG. 6 shows a modification of the electric double layer capacitor according to the second embodiment shown in FIG. FIG. 6A is a view of the sealing member 30 of the modification as viewed from the capacitor element 20 side, and FIG. 6B shows a cross-section AA ′ including the protruding portion 32, and FIG. Shows a BB 'cross section. 6 includes an elongated rectangular opening 33 as the opening 33. The length and width of the rectangular opening are substantially the same as the width and thickness of the flat portion 13 of the tab terminal 10.

  In the case of FIG. 6, the opening 33 has a shape that sandwiches the through portion 12 and the flat portion 13 in accordance with the outer shape of the portion where the tab terminal 10 transitions from the through portion 12 to the flat portion 13. In order to insert the tab terminal 10 having the penetrating portion 12 into the opening 33 of the protruding portion 32, the opening 33 is expanded by using the fact that the protruding portion 32 is made of a flexible material, for example, The penetrating part 12 having a round bar shape is passed.

  In the example of FIG. 6, the opening length and the opening width of the opening 33 in the in-plane direction of FIG. 6A are substantially the same as the lateral width and thickness of the flat portion 13 of the tab terminal 10, respectively. . On the other hand, the opening width of the opening 33 may be made slightly larger than the example of FIG. 6 in order to facilitate the insertion of the penetrating portion 12 of the tab terminal 10 into the opening 33. The opening width of the opening 33 may be set to such a width that the penetration part 12 can be easily inserted while the opening part 33 is expanded when the penetration part 12 of the tab terminal 10 is inserted. In addition, the opening 33 may be easily passed through the through-hole 12 by performing a taper process in the insertion direction of the through-hole 12 or by forming the opening into a shape other than the elongated rectangle.

  When the tab terminal 10 is inserted through the sealing body 30, the protruding portion 32 of FIG. 6 is in a state of sandwiching the entire outer shape of the portion of the tab terminal 10 that has transitioned from the through portion 12 to the flat portion 13. 10 is strongly fixed to the sealing body 30. Further, the protrusion 32 widens the gap between the capacitor element 20 impregnated with the electrolyte and the sealing body 30, and the transition portion from the penetrating portion 12 of the tab terminal 10 to the flat portion 13 and the opening of the protrusion 32. The insulating layer 15 is provided between the portion 33 (see FIGS. 6B and 6C). Accordingly, the modification shown in FIG. 6 more effectively realizes the effect obtained by adding the protruding portion 32 to the sealing body 30 described with reference to FIG.

As described above, in the electric double layer capacitor shown in FIGS. 5 and 6, the tab terminal 10 and the sealing body 30 are formed in addition to preventing the alkalinization of the electrolyte by forming the insulating layer 15 on the surface of the tab terminal 10. And an interval between the sealing body 30 and the capacitor element 20 is expanded to provide an electric double layer capacitor that more reliably reduces liquid leakage.
(Leakage evaluation test)
・ Summary of evaluation test

A pair of electrode bodies each joined with a tab terminal on which an insulating layer is formed in accordance with individual specifications described later are wound through a separator to prepare a capacitor element impregnated with an electrolytic solution described in the common specifications described later. . The capacitor element impregnated with the electrolytic solution is housed in a bottomed cylindrical aluminum case, and the opening of the aluminum case is sealed using a sealing body described in the individual specification described later. Here, each tab terminal extends outward through the terminal lead hole of the sealing body. In this way, samples of the following four types of electric double layer capacitors are actually produced, and the number of liquid leaks when used under high temperature and high humidity conditions is evaluated.
・ Common sample specifications

Electric double layer capacitor with rated voltage 2.5V and capacitance 1F Electrolyte; propylene carbonate 75 mass percent
Triethylmethylammonium tetrafluoroborate 25 mass percent Sealant material; Butyl rubber Resin material that forms insulating layer 15; Polypropylene Thickness that forms insulating layer 15; 10 microns

Sample 1; Resin application to the tab terminal; On the tab terminal 10, the insulating layer 15 shown in the first embodiment (see FIGS. 2 and 3) is formed. Specifically, the tab terminal 10 is immersed from the flat portion 13 side to the through portion 12 in a solvent solution in which the resin material is dispersed in a state where the flat portion 13 (both sides) is masked so as to cover the joint portion 14 by caulking. Then pull up. Remove the mask after lifting. Thereafter, the insulating layer 15 is formed by heat treatment.
Sealing body; it has a shape having no protrusion 32, and the thickness of the sealing body 30 in the tab terminal 10 penetrating direction is 2.6 mm.
Sample 2; resin application to tab terminal; insulating layer 15 is formed in the same manner as sample 1.
Sealing body: the shape shown in FIG. The thickness of the sealing body 30 other than the protruding portion 32 is 2.6 mm.
Sample 3; resin application to tab terminal; insulating layer 15 is formed in the same manner as sample 1.
Sealing body: It has the shape shown in FIG. The thickness of the sealing body 30 other than the protruding portion 32 is 2.6 mm.
Sample 4; Resin application to tab terminal; Insulating layer 15 is formed only on penetrating portion 12 of tab terminal 10; The solvent liquid in which the resin material is dispersed is applied to the penetrating portion 12 and heat-treated to form the insulating layer 15.
Sealing body: It is a shape which does not have the protrusion part 32 similarly to the sample 1, and the thickness of the sealing body 30 is 2.6 mm.
・ Evaluation test conditions

For each of Sample 1, Sample 2, Sample 3, and Sample 4, a rated voltage of 2.5 V was applied under conditions of a temperature of 60 degrees Celsius and a humidity of 95 percent, and the number of occurrences of liquid leakage after 3000 hours was confirmed. To do.
・ Result of evaluation test

  FIG. 7 shows the results of the evaluation test. In Sample 1, Sample 2, and Sample 3, none of the 20 samples caused liquid leakage. On the other hand, in Sample 4 in which the insulating layer 15 was formed only in the through portion 12 evaluated as a comparative example, liquid leakage occurred in 6 out of 20 samples. Therefore, the resin application (formation of the insulating layer 15 shown in FIGS. 2 and 3) of the sample 1, the sample 2, and the sample 3 in which the insulating layer 15 is formed not only in the through portion 12 but also on the flat portion 13 is as follows. It was found that there was an effect of suppressing leakage of the electrolyte.

  On the other hand, the difference between sample 2 or sample 3 and sample 1 was not detected from the result of this evaluation test. Providing the projecting portion 32 on the sealing body 30 has the effect in principle that the penetrating portion 12 is strongly fixed to the sealing body 30 and prevents the electrolyte from rising from the capacitor element 20 impregnated with the electrolyte. It is believed that there is. However, no difference due to this effect was detected in this evaluation test.

  DESCRIPTION OF SYMBOLS 1 ... Electric double layer capacitor, 10 ... Tab terminal, 10a ... Positive electrode tab terminal, 10b ... Negative electrode tab terminal, 11 ... Lead wire, 12 ... Through part, 13 ... Flat part, 14 ... Junction part, 15 ... Insulating layer, 16 DESCRIPTION OF SYMBOLS ... Exclusion part, 20 ... Capacitor element, 21 ... Current collector, 22 ... Polarizable electrode layer, 23 ... Electrode body, 30 ... Sealing body, 31 ... Terminal extraction hole, 32 ... Projection part, 33 ... Opening part, 40 ... Metal case, 41 ... Horizontal aperture, 42 ... Upper aperture

Claims (5)

  A capacitor element in which a pair of electrode bodies each consisting of a current collector and a polarizable electrode layer are wound through a separator and impregnated with an electrolyte, a bottomed cylindrical metal case that houses the capacitor element, An electrical two comprising: a sealing body that seals the opening of the metal case; and a tab terminal that is joined to each of the pair of electrode bodies and extends to the outside of the sealing body through a terminal lead-out hole of the sealing body. It is a multilayer capacitor, Comprising: The said tab terminal is equipped with the penetration part which penetrates the said sealing body, and the flat part which has a junction part with the said electrode body, The surface of the said penetration part, and junction with the said electrode body An electric double layer capacitor in which an insulating layer is formed on the surface of the flat portion excluding the portion.   The tab terminal is formed on the surface of the penetrating portion that penetrates the sealing body, and at least the surface of the flat portion in a range protruding from the wound electrode body of the capacitor element toward the sealing body. The electric double layer capacitor according to claim 1, wherein a layer is formed.   The sealing body further includes a protruding portion that protrudes toward the capacitor element in the same direction as the penetrating direction of the terminal lead hole, and the protruding portion includes a flat portion of the tab terminal and a thickness of the flat portion. The electric double layer capacitor according to claim 1, further comprising an opening sandwiched from the direction.   The protrusion part of the said sealing body has an opening part of the shape which pinches | interposes the penetration part and flat part of the said tab terminal according to the external shape of the part which the said tab terminal transfers to a flat part from a penetration part. Electric double layer capacitor.   The electric double layer capacitor according to any one of claims 1 to 4, wherein the insulating layer is formed in a penetrating portion and a flat portion of the tab terminal on the negative electrode side.