JP2009064931A - Winding-on type electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a winding-on type electric double layer capacitor which is used for various electronic apparatuses, does not lose a potential balance of an anode and cathode even if a charge and discharge are swiftly carried out at a large current, and has a high reliability and an excellent long lifetime. <P>SOLUTION: This winding-on type electric double layer capacitor comprises: a capacitor element 1 in which an anode electrode 5 and a cathode electrode 6 formed with polarized electrode layers 3, 4 on both faces of a collector 2 are wound via a separator 7 therebetween with the cathode electrode 6 being disposed outside; a metal case 10 which accommodates this capacitor element 1 together with a driving electrolyte; and a sealing member 9 for sealing this metal case 10. An unformed part where the polarized electrode layer 4 is not formed is provided in at least a part of a portion where the polarized electrode layer 4 of the cathode electrode 6 on the outermost periphery of the capacitor element 1 is not opposed to the polarized electrode layer 3 of the anode electrode 5, whereby even if the charge and discharge are swiftly carried out at a large current, a characteristic deterioration is suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wound electric double layer capacitor used in various electronic devices.

  FIG. 7 is a partially cutaway perspective view showing the configuration of this type of conventional wound electric double layer capacitor, and FIG. 8 is a winding end portion of a capacitor element used in the wound electric double layer capacitor. It is sectional drawing which showed. 7 and 8, reference numeral 101 denotes a capacitor element. The capacitor element 101 is formed by winding an anode electrode 105 and a cathode electrode 106 with a separator 104 interposed therebetween.

  The anode electrode 105 and the cathode electrode 106 are configured by forming polarizable electrode layers 103 on both surfaces of a current collector 102 made of a metal foil (the back side is not shown). Further, lead wires 107 are connected to the anode electrode 105 and the cathode electrode 106, respectively.

  The capacitor element 101 configured in this manner is inserted into a bottomed cylindrical metal case 109 after impregnating a driving electrolyte solution (not shown), and is made of rubber having a hole through which each lead wire 107 is inserted. After the sealing member 108 is disposed in the opening of the metal case 109, the opening of the metal case 109 is curled to perform sealing.

  Further, for the purpose of suppressing the deterioration of characteristics of the conventional wound electric double layer capacitor configured as described above, a structure in which the cathode electrode is wound by one turn more than the anode electrode of the capacitor element has been proposed. .

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2007-157811 A

  However, in the above-described conventional wound electric double layer capacitor, the polarizable electrode layer 103 is formed on both surfaces of the current collector 102 on each of the anode electrode 105 and the cathode electrode 106, and the cathode electrode 106 is disposed outside and wound. Therefore, the polarizable electrode layer 103 formed on the outer peripheral surface side of the cathode electrode 106 does not face the polarizable electrode layer 103 of the anode electrode 105 in the outermost peripheral portion of the capacitor element 101. For this reason, if it is used in such a manner that charging and discharging are repeated rapidly with a maximum current within the allowable range, the polarizable electrode layer 103 of the cathode electrode 106 faces the polarizable electrode layer 103 of the anode electrode 105. There is a problem in that the potential balance is lost, the anode electrode 105 is burdened, an overcurrent is generated, and the driving electrolyte is decomposed to generate gas, which causes capacity reduction and deteriorates characteristics. It was happening.

  The present invention solves such a conventional problem, and does not disturb the potential balance between the anode and the cathode even when charging and discharging are repeated rapidly with a large current, and has a high performance and long life winding with little deterioration in characteristics. It is an object of the present invention to provide an electric double layer capacitor.

  In order to solve the above problems, the present invention provides a pair of an anode electrode and a cathode electrode in which a polarizable electrode layer is formed on both sides of a current collector made of a metal foil, and the cathode electrode is placed outside with a separator interposed therebetween. A wound-type electric circuit comprising: a capacitor element that is wound in an overlapping manner; a bottomed cylindrical metal case that contains the capacitor element together with a driving electrolyte; and a sealing member that seals the opening of the metal case In the double-layer capacitor, an unformed portion where the polarizable electrode layer is not formed is provided in at least a part of the portion where the polarizable electrode layer of the cathode electrode which is the outermost periphery of the capacitor element does not face the polarizable electrode layer of the anode electrode It is a configuration.

  As described above, the wound electric double layer capacitor according to the present invention has a polarizable electrode on at least a part of a portion where the polarizable electrode layer of the cathode electrode which is the outermost periphery of the capacitor element does not face the polarizable electrode layer of the anode electrode. By providing a non-formed portion where no layer is formed, the non-opposing portions of the polarizable electrode layer of the anode electrode and the polarizable electrode layer of the cathode electrode are reduced, and the potential balance of the current flowing through the anode and the cathode is maintained. Therefore, even if charging and discharging are repeated rapidly with a large current, gas generation due to decomposition of the driving electrolyte can be suppressed, so that it has a highly reliable and long life with little characteristic deterioration. The electric double layer capacitor can be realized.

(Embodiment 1)
Hereinafter, the first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a partially cutaway perspective view showing a configuration of a wound electric double layer capacitor according to Embodiment 1 of the present invention, and FIG. 2 is a winding of a capacitor element used in the wound electric double layer capacitor. It is sectional drawing which showed the end part.

  1 to 2, reference numeral 1 denotes a capacitor element. The capacitor element 1 includes an anode electrode 5 having a polarizable electrode layer 3 formed on both surfaces of a current collector 2 made of a metal foil such as aluminum, and aluminum. A lead wire 8 is connected to a cathode electrode 6 having a polarizable electrode layer 4 formed on both surfaces of a current collector 2 made of a metal foil by cold pressure welding, ultrasonic welding or the like, and the anode electrode 5 and the cathode electrode 6 are connected to each other. A separator 7 for preventing a short circuit is interposed therebetween, and the cathode electrode 6 is placed outside and wound in a superposed state.

  Accordingly, the cathode electrode 6 is disposed on the outermost periphery of the capacitor element 1, and the polarizable electrode layer 4 on the outer peripheral side of the cathode electrode 6 does not face the polarizable electrode layer 3 of the anode electrode 5. The non-formed portion 4a where the polarizable electrode layer 4 is not formed is provided on at least a part of the outermost periphery of the cathode electrode 6.

  The capacitor element 1 thus configured is impregnated with a driving electrolyte solution (not shown) and then inserted into a bottomed cylindrical metal case 10, and a pair of lead wires 8 are inserted into holes provided in the sealing member 9. The sealing member 9 is inserted, and the outer periphery of the metal case 10 is drawn inward, and the opening is curled to compress the sealing member 9 and seal the metal case 10. ing.

  The polarizable electrode layers 3 and 4 formed on the anode electrode 5 and the cathode electrode 6 are composed of a mixture of activated carbon powder, carbon black and a binder, and the activated carbon powder includes wood powder and coconut shell systems. , Phenol resin-based, petroleum coke-based, coal coke-based, and pitch-based raw materials are used. As the binder, a mixture of a water-soluble binder of polytetrafluoroethylene and carboxymethyl cellulose (hereinafter referred to as CMC) is used.

As the solvent for the driving electrolyte, propylene carbonate, γ-butyrolactone, ethylene carbonate, sulfolane, acetonitrile, dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate is used, or a mixture of two or more. Yes. In addition, quaternary ammonium, quaternary sulfonium, and imidazolium salts are used as electrolyte cations, while BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ or N are used as electrolyte anions. (CF ₃ SO ₂ ) ₂ ^- is used.

  In the wound electric double layer capacitor according to the first embodiment of the present invention configured as described above, the polarizable electrode layer 4 of the cathode electrode 6 which is the outermost periphery of the capacitor element 1 is the polarizable electrode layer 3 of the anode electrode 5. Since the non-formed portion 4a where the polarizable electrode layer 4 is not formed is provided in at least a part of the portion that does not face the electrode, the potential balance of the currents flowing through the anode electrode 5 and the cathode electrode 6 is maintained, and charging is rapidly performed with a large current. Even if the discharge is repeated, the capacity deterioration can be suppressed.

  Specific examples will be described below.

Example 1
A high-purity aluminum foil (Al: 99.99% or more) having a thickness of 30 μm was used as a current collector made of metal foil, and the surface of the aluminum foil was roughened by electrolytic etching in a chlorine-based etching solution.

  Next, polarizable electrode layers were formed on both sides of the aluminum foil. The polarizable electrode layer is formed by using a phenol resin activated carbon powder having an average particle diameter of 5 μm, a carbon black having an average particle diameter of 0.05 μm as a conductivity imparting agent, and a water-soluble binder solution in which CMC is dissolved in 10: 2: 1. After mixing in a weight ratio of the above and sufficiently kneading with a kneader, methanol and water dispersion solvents were added little by little and further kneaded to prepare a paste having a predetermined viscosity. Then, this paste was apply | coated to the surface of aluminum foil, and it dried in 100 degreeC air | atmosphere for 1 hour, and formed the polarizable electrode layer.

  Next, the aluminum foil on which this polarizable electrode is formed is cut into dimensions of 39 × 475 mm as the anode side electrode and 39 × 495 mm as the cathode side electrode, and the anode and cathode lead wires are connected to the electrodes, respectively. did. Each lead wire was connected by removing a part of the polarizable electrode layer formed on the surface of the aluminum foil and joining each lead wire to the removed portion by cold welding.

  Subsequently, the cathode electrode is disposed outside, and these are wound in a state where a separator having a thickness of 35 μm, an anode electrode, and a separator having a thickness of 35 μm are sequentially disposed. At this time, the polarizable electrode layer of the cathode electrode at the end of winding has an unformed portion of 50.24 mm. Thus, a capacitor element (winding diameter: φ16 mm) having no portion where the polarizable electrode layer of the cathode electrode and the polarizable electrode layer of the anode electrode do not face each other was obtained.

  Subsequently, after impregnating the capacitor element with a driving electrolyte, the capacitor element is inserted into a bottomed cylindrical aluminum metal case, and a rubber sealing member having a hole through which a pair of lead wires is inserted is inserted into the metal case. Then, sealing was performed by drawing the outer peripheral portion and the opening of the metal case, and a φ18 × 50 mm wound electric double layer capacitor according to Example 1 was produced.

In addition, as a solvent for the driving electrolyte, a mixed solvent of propylene carbonate and dimethyl carbonate in a ratio of 7: 3 is used, and in the electrolyte, a 1 mol / l mixture of ethyl-dimethyl-imidazolium and BF ₄ ⁻ is dissolved. Was used.

(Example 2)
A wound electric double layer capacitor was produced in the same manner as in Example 1 except that the unformed portion of the polarizable electrode layer of the cathode electrode at the end of winding was changed to 80%.

(Example 3)
A wound electric double layer capacitor was fabricated in the same manner as in Example 1 except that the unformed portion of the polarizable electrode layer of the cathode electrode at the end of winding was changed to 500%.

Example 4
A wound electric double layer capacitor was produced in the same manner as in Example 1 except that the unformed portion of the polarizable electrode layer of the cathode electrode at the end of winding was changed to 40%.

(Example 5)
A wound electric double layer capacitor was produced in the same manner as in Example 1, except that the unformed portion of the polarizable electrode layer of the cathode electrode at the end of winding was changed to 20%.

(Example 6)
A wound electric double layer capacitor was produced in the same manner as in Example 1 except that the unformed portion of the polarizable electrode layer of the cathode electrode at the end of winding was changed to 10%.

(Comparative example)
A wound electric double layer capacitor was fabricated in the same manner as in Example 1 except that the unformed portion of the polarizable electrode layer of the cathode electrode at the end of winding was set to 0%.

  Table 1 shows the results of a large current charge / discharge test performed on the wound electric double layer capacitors (2.3V70F) of Examples 1 to 6 and Comparative Example of the present invention thus obtained.

  Here, the large current charge / discharge test is performed under the condition of 10000 cycles under the environment of 25 ° C., with the charge / discharge current value of the lower limit voltage 1.25V, the upper limit voltage 2.5V, 10A, constant voltage, and no pause. The capacitance after the test was compared. The number of tests was five, and the average value was described.

  As is clear from (Table 1), the wound electric double layer capacitors according to Examples 1 to 6 of the present invention have a higher capacity retention rate after the continuous charge / discharge test than the comparative examples, and are excellent in durability. I understand that. Moreover, since the capacity | capacitance change rate will be -5.5% or less when the non-formation part of the polarizable electrode layer of a cathode electrode is 25.12 mm (50%) or more, a longer life electric double layer capacitor is obtained.

(Embodiment 2)
Hereinafter, the second aspect of the present invention will be described with reference to the drawings.

  In this embodiment, the configuration of the capacitor element used in the wound electric double layer capacitor described in the first embodiment with reference to FIGS. 1 and 2 is partially different. Since the configuration is the same as that of the first embodiment, the same reference numerals are given to the same parts and the detailed description thereof is omitted, and only different parts will be described below with reference to the drawings.

  FIG. 3 is a cross-sectional view showing a winding start portion of a capacitor element used in the wound electric double layer capacitor according to the second embodiment of the present invention.

  In FIG. 3, 15 is an anode electrode, 16 is a cathode electrode, and 17 is a separator. The cathode electrode 16 is arranged outside, and the position is shifted in the winding direction so that the cathode electrode 16 protrudes from the anode electrode 15. Arranged and wound. Therefore, the cathode electrode 16 is disposed on the innermost periphery of the capacitor element, and the polarizable electrode layer 14 on the inner peripheral side of the cathode electrode 16 is not opposed to the polarizable electrode layer 13 of the anode electrode 15. Become. Therefore, the non-formed portion 14a where the polarizable electrode layer 14 is not formed is provided on at least a part of the innermost periphery of the cathode electrode 16.

  The wound electric double layer capacitor according to the second embodiment of the present invention configured as described above includes a portion where the polarizable electrode layer 14 of the cathode electrode 16 of the capacitor element does not face the polarizable electrode layer 13 of the anode electrode 15; Since the non-formed portion 14a where the polarizable electrode layer 14 is not formed is provided at least at a part of the innermost periphery of the cathode electrode 16 to be formed, the potential balance of the currents flowing through the anode electrode 15 and the cathode electrode 16 is balanced even in the innermost periphery. Thus, even if charging and discharging are repeated rapidly with a large current, an effect that capacity deterioration can be suppressed is obtained.

  In the second embodiment of the present invention, the polarizability of at least a part of the polarizable electrode layer 14 of the cathode electrode 16 that is the innermost periphery of the capacitor element is not opposed to the polarizable electrode layer 13 of the anode electrode 15. Although the description has been given using the wound electric double layer capacitor provided with the non-formed portion 14a where the electrode layer 14 is not formed, the polarizability of the cathode electrode 6 serving as the outermost periphery of the capacitor element 1 described in the first embodiment. In addition to the configuration in which the electrode layer 4 is provided with the non-formed portion 4a where the polarizable electrode layer 4 is not formed in at least a part of the portion of the anode electrode 5 not facing the polarizable electrode layer 3, both configurations are provided in one capacitor element. By forming the film, a better effect can be obtained.

(Embodiment 3)
The third embodiment of the present invention will be described below with reference to the drawings.

  4A is a plan view showing a configuration of a wound electric double layer capacitor according to Embodiment 3 of the present invention, FIG. 4B is a front sectional view thereof, FIG. 4C is a bottom view thereof, and FIG. ) Is a cross-sectional view showing a winding end portion of a capacitor element used in the wound electric double layer capacitor, and (b) is a cross-sectional view showing a winding start portion of the capacitor element.

  4 to 5, reference numeral 31 denotes a capacitor element. The capacitor element 31 is an anode in which a polarizable electrode layer 33 is formed on both surfaces of a current collector 32 made of a metal foil such as aluminum except for one end in the width direction. An electrode 35 and a cathode electrode 36 on which a polarizable electrode layer 34 is formed except for one end in the width direction of the current collector 32 are arranged in positions opposite to each other, and a short-circuit preventing separator 37 is interposed therebetween. In this configuration, an anode lead portion 35a and a cathode lead portion 36a are provided on both end surfaces (vertical direction in FIG. 4B) of the capacitor element 31, and the respective electrodes are taken out. is there.

  In addition, since the capacitor element 31 is wound with the cathode electrode 36 disposed outside, the cathode electrode 36 is disposed on the outermost periphery of the capacitor element 31, and the polarizable electrode on the outer periphery side of the cathode electrode 36. Since the layer 34 is not opposed to the polarizable electrode layer 33 of the anode electrode 35, an unformed portion 34 a that does not form the polarizable electrode layer 34 is provided on at least a part of the outermost periphery of the cathode electrode 36. Is.

  Further, at the beginning of winding, the cathode electrode 36 is disposed at the innermost periphery of the capacitor element 31 because the cathode electrode 36 is disposed while being shifted in the winding direction so as to protrude from the anode electrode 35. As a result, the innermost polarizable electrode layer 34 of the cathode electrode 36 does not face the polarizable electrode layer 33 of the anode electrode 35. Therefore, the cathode electrode 36 is provided with a non-formed portion 34b where the polarizable electrode layer 34 is not formed at least in part.

  The thus configured capacitor element 31 is inserted into a bottomed cylindrical metal case 38 together with a driving electrolyte (not shown), and the terminal plate 39 is inserted into the opening of the metal case 38 via a sealing rubber 41. Then, the opening of the metal case 38 is sealed by subjecting it to lateral drawing and curling, and the anode lead portion 35a is placed on the inner surface of the terminal plate 39, and the cathode lead portion 36a is placed on the inner bottom surface of the metal case. By connecting by welding or the like, the wound electric double layer capacitor according to the present embodiment is configured.

  The materials for the driving electrolyte and the polarizable electrode layer are the same as those used in the first embodiment, and a description thereof is omitted here.

  In the wound electric double layer capacitor according to the third embodiment of the present invention configured as described above, the polarizable electrode layer 34 of the cathode electrode 36 which is the outermost periphery of the capacitor element 31 is the polarizable electrode layer 33 of the anode electrode 35. An unformed portion 34 a where the polarizable electrode layer 34 is not formed is provided in at least a part of the portion that does not face the electrode, and the polarizable electrode layer 34 of the cathode electrode 36 that is the innermost periphery of the capacitor element 31 is the polarizability of the anode electrode 35. Since the non-formed portion 34b where the polarizable electrode layer 34 is not formed is provided in at least a part of the portion not facing the electrode layer 33, the potential of the current flowing in the anode electrode 35 and the cathode electrode 36 in the outermost periphery and the innermost periphery. Even if the balance is maintained and charging and discharging are repeated rapidly with a large current, the capacity deterioration can be suppressed.

(Embodiment 4)
The fourth embodiment of the present invention will be described below with reference to the drawings.

  In this embodiment, the configuration of the capacitor element used in the wound electric double layer capacitor described in the first embodiment with reference to FIGS. 1 and 2 is partially different. Since the configuration is the same as that of the first embodiment, the same reference numerals are given to the same parts and the detailed description thereof is omitted, and only different parts will be described below with reference to the drawings.

  6A is a cross-sectional view showing a winding end portion of a capacitor element used in the wound electric double layer capacitor according to Embodiment 4 of the present invention, and FIG. 6B is a winding start portion of the capacitor element. It is sectional drawing which showed.

  6 (a) and 6 (b), 45 is an anode electrode, 46 is a cathode electrode, 47 is a separator, and the capacitor element has the cathode electrode 46 arranged outside, and the cathode electrode 46 is more than the anode electrode 45. Also, the winding is shifted and arranged in the winding direction so as to protrude. Therefore, the cathode electrode 46 is disposed on the outermost and innermost circumferences of the capacitor element, and the polarizable electrode layer 44 on the outer peripheral side of the cathode electrode 46 and the polarizable electrode layer 44 on the inner peripheral side cathode electrode 46. Does not face the polarizable electrode layer 43 of the anode electrode 45, respectively. Therefore, at least a part of the polarizable electrode layer 44 on the outermost periphery and innermost periphery of the cathode electrode 46 is covered with the insulating materials 44a and 44b, respectively.

  In addition, as the material of the insulating materials 44a and 44b, for example, modified polypropylene, polyamideimide and the like can be used, and the polarizable electrode layer 44 can be covered uniformly and does not dissolve or swell in the driving electrolyte. Anything is acceptable.

  In the wound electric double layer capacitor according to the fourth embodiment of the present invention configured as described above, the polarizable electrode layer 44 of the cathode electrode 46 on the outermost periphery of the capacitor element faces the polarizable electrode layer 43 of the anode electrode 45. An insulating material 44 a that covers the polarizable electrode layer 44 is provided on at least a part of the unpolarized portion, and the polarizable electrode layer 44 of the cathode electrode 46 that is the innermost periphery of the capacitor element is the polarizable electrode layer 43 of the anode electrode 45. Since the insulating material 44b that covers the polarizable electrode layer 44 is provided on at least a part of the portion that does not face the electrode, the potential balance of the current flowing through the anode electrode 45 and the cathode electrode 46 is maintained in the outermost periphery and the innermost periphery, Even when rapid charge / discharge is repeatedly performed with a large current, the capacity deterioration can be suppressed.

  As described above, according to the wound electric double layer capacitor of the present invention, even if charging and discharging are repeated rapidly with a large current, it has the effect of being excellent in high reliability and long life with little characteristic deterioration, It is effective as a wound electric double layer capacitor for in-vehicle use.

1 is a partially cutaway perspective view showing a configuration of a wound electric double layer capacitor according to Embodiment 1 of the present invention. Sectional view showing the end of winding of the capacitor element used in the same wound type electric double layer capacitor Sectional drawing which showed the winding start part of the capacitor | condenser element used for the winding type electric double layer capacitor by Embodiment 2 of this invention (A) The top view which showed the structure of the winding type electric double layer capacitor in Embodiment 3 of this invention, (b) The front sectional view, (c) The bottom view (A) Cross-sectional view showing a winding end portion of a capacitor element used in the same-winding electric double layer capacitor, (b) Cross-sectional view showing the same winding start portion (A) Sectional drawing which showed the winding end part of the capacitor | condenser element used for the winding type electric double layer capacitor in Embodiment 4 of this invention, (b) Sectional drawing which showed the winding start part Partially cutaway perspective view showing the configuration of a conventional wound electric double layer capacitor Sectional view showing the end of winding of the capacitor element used in the same wound type electric double layer capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Current collector 3, 4 Polarization electrode layer 5 Anode electrode 6 Cathode electrode 7 Separator 8 Lead wire 9 Sealing member 10 Metal case

Claims (5)

A capacitor element in which a pair of an anode electrode and a cathode electrode each having a polarizable electrode layer formed on both sides of a current collector made of a metal foil, with the separator interposed therebetween, and wound with the cathode electrode facing outside In a wound electric double layer capacitor comprising a bottomed cylindrical metal case containing the capacitor element together with a driving electrolyte and a sealing member sealing the opening of the metal case, the outermost periphery of the capacitor element A wound electric double layer capacitor in which the polarizable electrode layer of the cathode electrode is provided with a non-formed portion where the polarizable electrode layer is not formed at least in a portion of the anode electrode not facing the polarizable electrode layer. The wound electric double layer capacitor according to claim 1, wherein 50% or more of the non-formed portion where the polarizable electrode of the cathode electrode is not formed is provided. A cathode which is the innermost circumference of this capacitor element is wound with one of the anode electrode and the cathode electrode overlapped with a separator interposed therebetween so that the cathode electrode protrudes from the winding start position. The wound electric double layer capacitor according to claim 1, wherein an unformed portion where the polarizable electrode layer is not formed is provided in at least a part of a portion where the polarizable electrode layer of the electrode does not face the polarizable electrode layer of the anode electrode. The capacitor element is configured to take out each of the anode / cathode electrodes from both end faces, and by joining one electrode of the capacitor element to the inner bottom surface of the metal case and the other electrode to the inner surface of the sealing member. The wound electric double layer capacitor according to any one of claims 1 to 3, wherein one electrode of the capacitor element is taken out from the metal case and the other electrode is taken out from the sealing member. A capacitor element in which a pair of an anode electrode and a cathode electrode each having a polarizable electrode layer formed on both sides of a current collector made of a metal foil, with the separator interposed therebetween, and wound with the cathode electrode facing outside In a wound electric double layer capacitor comprising a bottomed cylindrical metal case containing the capacitor element together with a driving electrolyte and a sealing member sealing the opening of the metal case, the outermost periphery of the capacitor element A wound electric double layer capacitor in which at least a part of the polarizable electrode layer of the cathode electrode that is not facing the polarizable electrode layer of the anode electrode is covered with an insulating material.

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