JP2007157811A - Winding electric double-layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable winding electric double-layer capacitor having less deterioration in characteristics by suppressing an electrochmeical reaction on the surface of a polarizable electrode layer. <P>SOLUTION: The capacitor is provided with a capacitor element 1 wound with a separator 4 interposed between an anode electrode 2 and a cathode electrode 3 to which an anode lead 8 and a cathode lead 9 are connected, while exposing one part of a current collector having a polarizable electrode layer formed on both surfaces; a metallic case for housing the capacitor element 1 together with a driving electrolyte; and an opening member for sealing an opening of the metallic case. In addition, at least one turn is wound from the winding end of the anode electrode 2 of the capacitor element 1, thereby providing a portion where the polarizable electrode layers formed on the cathode electrode 3 oppose with each other via the separator 4 on an outermost circumference of the capacitor element 1. This configuration can form the highly reliable winding electric double layer capacitor having less deterioration in characteristics. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  4 (a) and 4 (b) are an exploded perspective view showing the configuration of a conventional wound electric double layer capacitor of this type and a developed perspective view showing the configuration of a capacitor element used in the capacitor, In FIG. 4, reference numeral 31 denotes a capacitor element. The capacitor element 31 is constituted by winding an anode electrode 34 and a cathode electrode 35 with a separator 36 interposed therebetween.

  The anode electrode 34 and the cathode electrode 35 are configured by forming polarizable electrode layers (not shown) on both sides of a current collector (not shown) made of a metal foil, respectively. The anode lead wire 32 and the cathode lead wire 33 are connected to the anode electrode 34 and the cathode electrode 35, respectively.

  The capacitor element 31 configured in this manner is impregnated with a driving electrolyte solution (not shown) and then inserted into the bottomed cylindrical metal case 38, and the hole through which the anode lead wire 32 and the cathode lead wire 33 are inserted. After the rubber sealing member 37 having the above is disposed in the opening of the metal case 38, the outer periphery of the opening of the metal case 38 is drawn inward to perform sealing.

  The polarizable electrode layer formed on the anode electrode 34 and the cathode electrode 35 is composed of activated carbon powder, carbon black as a conductivity-imparting agent, and water-soluble polytetrafluoroethylene and carboxymethylcellulose (hereinafter abbreviated as CMC) as a binder. A paste was prepared by mixing a functional binder and sufficiently kneading with a kneader, and this paste was applied to the front and back surfaces of a current collector made of aluminum foil and dried. Both electrodes 35 are formed to have substantially the same dimensions.

  Also, the anode lead wire 32 and the cathode lead wire 33 are current collectors in which the polarizable electrode layer is partially removed at the connection portions in order to improve the connection with the aluminum foil as the current collector. The aluminum foil is exposed.

As prior art document information related to the invention of this application, for example, Patent Document 1 and Patent Document 2 are known.
Japanese Patent Laid-Open No. 10-270293 Japanese Patent Laid-Open No. 9-17695

  However, in the above-described conventional wound electric double layer capacitor, the capacity of the anode electrode 34 and the capacity of the cathode electrode 35 are designed to be the same, so that when the voltage is applied to the electric double layer capacitor, the anode electrode 34 and the cathode The electrode 35 is polarized by the same width as the natural potential, and as a result, an electrochemical reaction occurs on the surface of the polarizable electrode layer of each electrode, resulting in characteristics deterioration such as gas generation, resistance increase, and capacity decrease. It had the subject of doing.

Further, when the anode electrode 34 and the cathode electrode 35 are wound with the separator 36 interposed therebetween, the anode electrode 34 may be slightly longer than the cathode electrode 35, and the anode electrode 34 may protrude, and thus the anode electrode When used for a long time with the protrusion 34 protruding, the driving electrolyte solution causes a chemical reaction between the tip of the cathode electrode 35 and the anode electrode 34, and the electrolyte anions BF ₄ ⁻ , PF ₆ ^{− and the} like are attracted to the anode side. There is a problem that the peripheral portion becomes acidic and deteriorates the separator 36, resulting in deterioration of characteristics.

  An object of the present invention is to solve such a conventional problem and to provide a high-performance wound electric double layer capacitor that suppresses an electrochemical reaction on the surface of a polarizable electrode layer and has little characteristic deterioration. Is.

  In order to solve the above problems, the present invention provides an anode electrode in which a polarizable electrode layer is formed on both sides of a current collector made of metal foil and a lead wire is connected, and a cathode electrode formed in the same manner as the anode electrode. A capacitor element formed by winding a separator between them, a cylindrical metal case with a bottom containing the capacitor element together with a driving electrolyte, and an opening of the metal case sealed In the wound electric double layer capacitor comprising the opening member, a polarizable electrode layer formed on the cathode electrode at least one turn from the winding end portion of the polarizable electrode layer formed on the anode electrode constituting the capacitor element is provided. A structure in which a portion where polarizable electrode layers formed on the cathode electrode face each other via a separator is provided on the outermost peripheral surface of the capacitor element by winding. A.

As described above, the wound electric double layer capacitor according to the present invention winds the polarizable electrode layer formed on the cathode electrode at least one turn from the winding end portion of the polarizable electrode layer formed on the anode electrode of the capacitor element. By rotating the outermost peripheral surface of the capacitor element, a portion where the polarizable electrode layers formed on the cathode electrode face each other with a separator interposed therebetween is used, so that the driving electrolyte and each current collector constituting each electrode are configured. It is possible to set the potential of the polarizable electrode layer in an electrochemically stable region where a member such as a body does not cause an electrochemical reaction, and BF ₄ ⁻ , which are electrolyte anions on the surface of the anode electrode, PF ₆ ^- like without deterioration of the separator for it not become acidic and concentrated, Thus, the gas generation caused by the electrochemical reaction, eliminating the resistance increases and the capacitance decreases, less characteristic degradation In which there is an advantage that it is possible to realize a winding type electric double layer capacitor reliability.

(Embodiment)
Hereinafter, the invention described in the entire claims of the present invention will be described using embodiments.

  FIG. 1 is an exploded perspective view showing a configuration of a capacitor element used in a wound electric double layer capacitor according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a capacitor element. Is constituted by winding the anode electrode 2 and the cathode electrode 3 with a separator 4 interposed therebetween.

  The anode electrode 2 and the cathode electrode 3 are formed by forming polarizable electrode layers 6 or 7 on both surfaces of a current collector 5 made of a metal foil, which will be described later. The cathode lead wire 8 and the cathode lead wire 9 are connected to the cathode electrode 3 and the connection between the anode lead wire 8 and the cathode lead wire 9 is shown in detail in FIGS. 2 (a) and 2 (b). As described above, a part of the polarizable electrode layer 6 formed on the anode electrode 2 (the same applies to the polarizable electrode layer 7 formed on the cathode electrode 3) was removed to expose the current collector 5, and this was exposed. The anode lead wire 8 is connected to the portion by cold welding, ultrasonic welding or the like.

  Further, the polarizable electrode layer 7 formed on the cathode electrode 3 is wound around one turn from the end of winding of the polarizable electrode layer 6 formed on the anode electrode 2 (in FIG. 1). By making the cathode electrode 3 longer than the anode electrode 2 by L1, the outermost peripheral surface faces the polarizable electrode layers 7 formed on the cathode electrode 3 through the separator 4).

  The thus configured capacitor element 1 has the anode lead wire 8 and the cathode lead wire 9 inserted through holes provided in a rubber sealing member (not shown) and is attached with a sealing member, and driving electrolytics (not shown). After impregnating with the liquid, it is inserted into a bottomed cylindrical metal case (not shown) and the sealing member is disposed in the opening of the metal case, and the opening of the metal case is subjected to lateral drawing and curling. The sealing is performed through the sealing member.

  Further, as the activated carbon powder constituting the polarizable electrode layers 6 and 7 formed on the anode electrode 2 and the cathode electrode 3, respectively, wood powder type, coconut shell type, phenol resin type, petroleum coke type, coal coke type, pitch What activated the raw material of the system is used.

In addition, as a solvent for the driving electrolyte, one or a mixture of two or more of propylene carbonate, γ-butyrolactone, ethylene carbonate, sulfolane, acetonitrile, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate is used. In addition, quaternary ammonium, quaternary phosphonium, 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.

  Thus, by winding the polarizable electrode layer 7 formed on the cathode electrode 3 at least one turn from the winding end portion of the polarizable electrode layer 6 formed on the anode electrode 2 of the capacitor element 1, a capacitor is obtained. In the configuration in which the polarizable electrode layer 7 formed on the cathode electrode 3 is opposed to the element 1 through the separator 4 on the outermost peripheral surface of the element 1, the drive electrolyte solution and the electrodes 2 and 3 are formed. It becomes possible to set the potential of the polarizable electrodes 6 and 7 in an electrochemically stable region where the member such as the electric body 5 does not cause an electrochemical reaction, thereby generating gas due to the occurrence of the electrochemical reaction. Further, since there is no increase in resistance and no decrease in capacity, a highly reliable wound electric double layer capacitor with little deterioration in characteristics can be obtained.

Further, by forming the polarizable electrode layer 6 on the surface of the anode lead wire 8 connected to the anode electrode 2, BF ₄ ⁻ , PF ₆ ^{− and the} like which are electrolyte anions due to the chemical reaction of the driving electrolyte solution. Therefore, the separator 4 can be prevented from being deteriorated.

  Specific examples will be described below.

Example 1
As a current collector made of metal foil, a high-purity aluminum foil (AL: 99.99% or more) having a thickness of 30 μm was used, and the surface of the aluminum foil was roughened by electrolytic etching in a hydrochloric acid-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 size of 5 μm, carbon black having an average particle size 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 the polarizable electrode layer was formed was cut into dimensions of 40 × 475 mm as an anode electrode and 40 × 535 mm as a cathode electrode, thereby producing an anode electrode and a cathode electrode, respectively.

  Next, an anode lead wire and a cathode lead wire were connected to the anode electrode and the cathode electrode, respectively. 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, these are wound in a state where a separator having a thickness of 35 μm is interposed between the anode electrode and the cathode electrode. At this time, since the cathode electrode was set to be 60 nm longer than the anode electrode, it was formed on the cathode electrode by winding the cathode electrode at least one turn from the winding end portion (56.52 mm) of the anode electrode. A capacitor element (winding diameter: φ18 mm) having a portion where the polarizable electrode layers face each other with a separator interposed therebetween was obtained.

  Next, this capacitor element was impregnated with a driving electrolyte. This driving electrolyte was prepared by dissolving 4 ethylammonium boron tetrafluoride in propylene carbonate.

  Subsequently, the capacitor element is inserted into a bottomed cylindrical aluminum metal case, and the opening of the metal case is sealed with a rubber sealing member, whereby the winding according to the present embodiment is performed. An electric double layer capacitor was produced (capacitor dimension: φ20 × 45 mm).

(Example 2)
In Example 1 above, the anode electrode and the cathode electrode were arranged as shown in FIG. 3, and the cathode electrode width W2 was set to 44 mm with respect to the anode electrode width W1 (40 mm). A wound electric double layer capacitor was produced.

(Example 3)
In the above Example 1, a wound electric double layer was formed in the same manner as in Example 1 except that a polarizable electrode layer was formed on the surface of the anode lead wire connected to the anode electrode so that the anode lead wire was not exposed. A capacitor was produced.

(Comparative Example 1)
In Example 1 above, the dimensions of the cathode electrode are 30 × 495 mm (20 mm longer than the anode electrode, but since the separator is interposed between the anode electrode and the cathode electrode, the winding end of the anode electrode and the cathode electrode is substantially A wound electric double layer capacitor was produced in the same manner as in Example 1 except that the same was applied.

  For the wound electric double layer capacitors of Examples 1 to 3 and Comparative Example 1 thus obtained, the initial characteristics (capacitance, DC capacitor resistance (hereinafter abbreviated as DCR)), and 85 ° C. The results of the characteristic deterioration test when 2.3 V is applied are shown in (Table 1). In addition, the number of tests was 20 and the average value was described. Further, the DCR is obtained by discharging after charging and calculating the slope between 0.5 to 2.0 seconds at the start.

As is clear from Table 1, the wound electric double layer capacitor according to the present invention has less capacitance change than Comparative Example 1, and can greatly improve ΔC, ΔDCR, and product blistering in the characteristic deterioration test. It is understood that it can be done.

As described above, the wound electric double layer capacitor according to the present invention winds the polarizable electrode layer formed on the cathode electrode at least one turn from the end of winding of the polarizable electrode layer formed on the anode electrode of the capacitor element. By rotating the outermost peripheral surface of the capacitor element, a portion where the polarizable electrode layers formed on the cathode electrode face each other with a separator interposed therebetween is used, so that the driving electrolyte and each current collector constituting each electrode are configured. It is possible to set the potential of the polarizable electrode layer in an electrochemically stable region where a member such as a body does not cause an electrochemical reaction, and BF ₄ ⁻ , which are electrolyte anions on the surface of the anode electrode, PF ₆ ^- like without deterioration of the separator in order to be free to become acidic concentrated, Thus, the gas generation caused by the electrochemical reaction, eliminating the resistance increases and the capacitance decreases, less high characteristics deteriorate In which there is an advantage that it is possible to realize a winding type electric double layer capacitor of dependability.

  The wound electric double layer capacitor according to the present invention has an effect that the polarizable electrode layer is less deteriorated in characteristics and excellent in reliability, and is particularly useful for an in-vehicle electronic device circuit.

1 is an exploded perspective view showing a configuration of a capacitor element used in a wound electric double layer capacitor according to an embodiment of the present invention. (A) The principal part top view which showed the state which connected the anode lead wire to the anode electrode which comprises the same capacitor | condenser element, (b) AA sectional drawing of the same figure (a) Sectional drawing of the principal part which showed the relationship of the width dimension of the anode electrode and cathode electrode in Example 2 (A) Exploded perspective view showing the configuration of a conventional wound electric double layer capacitor, (b) Exploded perspective view showing the configuration of a capacitor element used in the capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode electrode 3 Cathode electrode 4 Separator 5 Current collector 6,7 Polarization electrode layer 8 Anode lead wire 9 Cathode lead wire

Claims (4)

A polarizing electrode layer is formed on both sides of a current collector made of metal foil, and an anode electrode connected with a lead wire and a cathode electrode formed in the same manner as this anode electrode are wound with a separator interposed therebetween. A wound-type electric double layer comprising a capacitor element constituted by this, a bottomed cylindrical metal case containing the capacitor element together with a driving electrolyte, and an opening member sealing the opening of the metal case In the capacitor, by winding the polarizable electrode layer formed on the cathode electrode at least one turn from the winding end portion of the polarizable electrode layer formed on the anode electrode constituting the capacitor element, the outermost periphery of the capacitor element A wound electric double layer capacitor in which a portion where polarizable electrode layers formed on a cathode electrode face each other via a separator is provided on the surface. The wound electric double layer capacitor according to claim 1, wherein the width of the polarizable electrode layer of the cathode electrode constituting the capacitor element is wider than the width of the polarizable electrode layer of the anode electrode. The wound electric double layer capacitor according to claim 1, wherein an exposed portion of the current collector is provided in a part of the polarizable electrode layer, and a lead wire is connected to the exposed portion of the current collector. 4. The wound electric double layer capacitor according to claim 3, wherein a polarizable electrode layer is formed on at least the surface of the lead wire connected to the anode electrode.

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