JP4839807B2 - Winding type 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 electrochmeical reaction on the surface of a polarizable electrode. <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 this configuration, a portion where a polarizable electrode layer does not exist on the opposite other electrode is provided via the lead connected to at least one electrode of the wound capacitor element 1 and the separator 4. Thus, the highly reliable winding electric double-layer capacitor having less deterioration in characteristics can be formed. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

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

  5 (a) and 5 (b) are an exploded perspective view showing the structure of a conventional wound electric double layer capacitor of this type and a developed perspective view showing the structure of a capacitor element used in the capacitor, In FIG. 5, 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 type electric double layer capacitor, the anode lead wire 32 and the cathode lead wire 33 are made of a polarizable electrode layer in order to improve the connection between the current collector and the aluminum foil. Since this is a configuration in which the aluminum foil is removed and connected to the exposed portion of the aluminum foil (the polarizable electrode layer exists on the other electrode side facing the lead wire through the separator), When a battery is used for a long time, the potential difference between the connecting portion of the cathode lead wire 33 connected to the cathode electrode 35 and the anode electrode 34 facing through the separator 36 is different between the other anode electrode 34 and the cathode electrode 35. for greater than the potential difference, BF electrolyte anions driving electrolyte is chemically react therebetween ₄ ^-, PF ₆ ^- and the like are attracted to the anode side, becomes its periphery acidic Would be to degrade the separator 36, there is a problem that characteristic deteriorates.

  On the other hand, the alkaline component is attracted to the cathode side even between the connecting portion of the anode lead wire 32 connected to the anode electrode 34 and the cathode electrode 35 facing through the separator 36, but the separator 36 does not deteriorate. There was a problem that characteristic deterioration occurred.

  Further, since the capacity of the anode electrode 34 and the capacity of the cathode electrode 35 are designed to be the same capacity, when a voltage is applied to the electric double layer capacitor, the anode electrode 34 and the cathode electrode 35 are polarized by the same width from the natural potential. As a result, an electrochemical reaction occurs on the surface of the polarizable electrode layer of each electrode, and there is a problem that characteristic deterioration such as gas generation, resistance increase, and capacity decrease occurs.

  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 forms a polarizable electrode layer on both surfaces of a current collector made of a metal foil, and leads to an exposed portion of the current collector provided on a part of the polarizable electrode layer. A capacitor element formed by winding an anode electrode connected to each other and a cathode electrode formed in the same manner as the anode electrode with a separator interposed therebetween, and the capacitor element is housed together with a driving electrolyte In a wound electric double layer capacitor comprising a bottomed cylindrical metal case and an opening member sealing the opening of the metal case, leads connected to the anode electrode and the cathode electrode constituting the capacitor element, respectively provided an exposed portion of the current collector to the anode electrode and the cathode electrode opposed to each other via a connecting portion and the separator lines, the exposed area of the current collector of the electrode the lead wire is connected to the (A1), and this When the exposed area of the current collector of the electrode toward the (B1), is obtained by the structure in which the (A1) ≦ (B1).

  Further, 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 The surface is provided with a portion where polarizable electrode layers formed on a cathode electrode face each other with a separator interposed therebetween.

As described above, the wound electric double layer capacitor according to the present invention includes an anode electrode that constitutes a wound capacitor element , a lead wire connected to each of the anode electrode and the cathode electrode, and an anode electrode that is opposed via the separator, and An exposed portion of the current collector is provided on the cathode electrode, and the exposed area of the current collector of the electrode to which the lead wire is connected is defined as (A1), and the exposed area of the current collector of the electrode facing this is defined as (B1) When (A1) ≦ (B1), the electrolysis for driving between the portions where the polarizable electrode layer provided on the anode electrode facing the connecting portion of the lead wire connected to the cathode electrode does not exist Electrolyte anions such as BF ₄ ⁻ and PF ₆ ⁻ are not attracted to the anode side due to the chemical reaction of the liquid, and the deterioration of the separator can be prevented. Further, the alkaline component is not attracted to the cathode side even between the portions where the polarizable electrode layer provided on the cathode electrode facing the connecting portion of the lead wire connected to the anode electrode does not exist, and the deterioration of the separator is prevented. be able to.

  Further, 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 of the capacitor element, Electrochemistry in which members such as the driving electrolyte and current collectors that make up each electrode do not cause an electrochemical reaction due to the configuration in which the polarizable electrode layers formed on the cathode electrode face each other with a separator interposed therebetween. Because it is possible to set the potential of the polarizable electrode layer in a stable region, there is no gas generation caused by electrochemical reaction, no increase in resistance or a decrease in capacity, and highly reliable winding with little characteristic deterioration The effect that a type electric double layer capacitor can be realized is obtained.

(Embodiment)
Hereinafter, the invention described in the entire claims of the present invention will be described by 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. A cathode lead wire 8 and a cathode lead wire 9 are connected to the cathode electrode 3 and the cathode lead wire 9, respectively. The connection between the anode lead wire 8 and the cathode lead wire 9 is shown in FIGS. 2 (a) and 2 (b). As shown in detail, the collector 5 is exposed by removing a part of the polarizable electrode layer 7 formed on the cathode electrode 3 (the same applies to the polarizable electrode layer 6 formed on the anode electrode 2). The cathode lead wire 9 is connected to the exposed part by cold welding, ultrasonic welding or the like.

  Further, as shown in FIG. 3, the anode electrode 2 facing the connecting portion of the cathode lead wire 9 of the cathode electrode 3 is previously provided with a portion where the polarizable electrode layer 6 does not exist.

  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, the polarizable electrode layer 6 is present on the anode electrode 2 facing the connecting portion of the cathode lead wire 9 connected to the current collector 5 of the cathode electrode 3 of the wound capacitor element 1 via the separator 4. By providing a portion that does not, the electrolyte anions BF ₄ ⁻ , PF ₆ ^{− and the} like due to the chemical reaction of the driving electrolyte solution are not attracted to the anode side, and the deterioration of the separator 4 can be prevented. As a result, gas generation due to the electrochemical reaction, resistance increase, and capacity decrease are eliminated, and a highly reliable wound electric double layer capacitor with little characteristic deterioration can be obtained.

  As shown in FIG. 4, the cathode electrode 3 facing the anode lead wire 8 connected to the anode electrode 2 via the separator 4 is also provided with a portion where the polarizable electrode layer 7 does not exist partially. The alkali component is not attracted to the cathode side, and the deterioration of the separator 4 can be suppressed.

  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 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 the polarizable electrode layer was formed was cut into dimensions of 40 × 475 mm as the anode electrode and 40 × 500 mm as the 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 (3.5 × 20 mm) 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. And when these are wound, the polarizable electrode layer exists by removing a part (3.5 × 20 mm) of the polarizable electrode layer also on the anode electrode facing the connecting portion of the cathode lead wire through the separator A portion not to be provided was provided (Al: 70 mm ² , B1: 70 mm ² ).

  Subsequently, a capacitor element (winding diameter: φ18 mm) was obtained by winding a separator having a thickness of 35 μm between the anode electrode and the cathode electrode.

  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, except that the area of the polarizable electrode layer provided on the anode electrode facing the connecting portion of the cathode lead wire connected to the cathode electrode through the separator is 4.0 × 25 mm. A wound electric double layer capacitor was produced in the same manner as in Example 1 (Al: 70 mm ² , B1: 100 mm ² ).

(Example 3)
In Example 1 above, except that the area of the polarizable electrode layer provided on the anode electrode facing the connecting portion of the cathode lead wire connected to the cathode electrode through the separator was set to 5.0 × 28 mm. A wound electric double layer capacitor was produced in the same manner as in Example 1 (Al: 70 mm ² , B1: 140 mm ² ).

Example 4
In Example 1 above, except that the area of the polarizable electrode layer provided on the anode electrode facing the connecting portion of the cathode lead wire connected to the cathode electrode through the separator was changed to 3.5 × 20 mm. A wound electric double layer capacitor was produced in the same manner as in Example 1 (Al: 70 mm ² , B1: 70 mm ² ).

(Example 5)
In Example 1 above, the dimensions of the cathode electrode were set to 30 × 535 mm (the cathode electrode was set to be 60 mm longer than the anode electrode, so one round from the end of winding of the polarizable electrode layer formed on the anode electrode ( 53.38 mm) is wound by the polarizable electrode layer formed on the cathode electrode, so that the polarizable electrode layers formed on the cathode electrode face each other via a separator) A wound electric double layer capacitor was produced in the same manner as in Example 1 except for the above.

(Comparative Example 1)
In Example 1 above, the wound shape is the same as in Example 1 except that the polarizable electrode layer is present on the anode electrode facing the connecting portion of the cathode lead wire connected to the cathode electrode through the separator. An electric double layer capacitor was produced.

  For the wound electric double layer capacitors of Examples 1 to 5 and Comparative Example 1 thus obtained, the initial characteristics (capacitance, DC capacitor resistance (hereinafter abbreviated as DCR) and 2 at 85 ° C. were obtained. Table 1 shows the results of the characteristic degradation test when .3 V was applied, and the number of tests was 20, and the average value was written.The DCR was discharged after being charged. The slope between 0.5 to 2.0 seconds at the start is calculated.

  As is clear from Table 1, the wound electric double layer capacitors according to Examples 1 to 4 of the present invention include a cathode lead wire connection portion and a separator connected to the cathode electrode of the wound capacitor element. Comparative Example 1 was obtained by providing each of the anode electrode opposed to the anode electrode, and the anode electrode wire connected to the anode electrode and the cathode electrode opposed to the anode electrode via the separator without the polarizable electrode layer. It can be seen that the change in capacity is smaller than that of ΔC, and ΔC, ΔDCR, and product blistering by the characteristic deterioration test can be greatly improved.

  Further, in the wound electric double layer capacitor according to Example 5, the polarizable electrode layer formed on the cathode electrode is wound for one turn from the winding end portion of the polarizable electrode layer formed on the anode electrode of the capacitor element. By providing a configuration in which the polarizable electrode layers formed on the cathode electrode are opposed to each other with a separator provided on the outermost peripheral surface, the driving electrolyte, the current collector constituting the polarizable electrode, etc. Since it becomes possible to set the potential of the polarizable electrode layer in an electrochemically stable region where the member does not cause an electrochemical reaction, gas generation caused by the electrochemical reaction, increase in resistance and decrease in capacity are eliminated, The characteristic deterioration can be further reduced.

As described above, the wound electric double layer capacitor according to the present invention has a polarizable electrode layer on the other electrode facing the connecting portion of the lead wire connected to at least one electrode of the wound capacitor element via the separator. By providing a portion that does not exist, the electrolyte is generated by a chemical reaction of the driving electrolyte between the portion of the cathode lead wire connected to the cathode electrode and the portion where the polarizable electrode layer provided on the opposite anode electrode does not exist. Anions such as BF ₄ ⁻ and PF ₆ ⁻ are not attracted to the anode side, and the separator can be prevented from deteriorating. Further, the alkaline component is not attracted to the cathode side even between the portions where the polarizable electrode layer provided on the cathode electrode facing the connecting portion of the anode lead wire connected to the anode electrode does not exist, and the deterioration of the separator is prevented. be able to.

  Further, by winding 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, the cathode electrode is formed on the outermost peripheral surface. The structure in which the formed polarizable electrode layers are opposed to each other with the separator interposed therebetween, so that the members such as the driving electrolyte and the current collector constituting the polarizable electrode do not cause an electrochemical reaction. Since it is possible to set the potential of the polarizable electrode in a stable region, gas generation caused by electrochemical reaction, increase in resistance, and decrease in capacity are eliminated, and highly reliable wound-type electric circuits with little characteristic deterioration are eliminated. A multilayer capacitor can be realized.

  The wound electric double layer capacitor according to the present invention has an effect that the characteristic deterioration is small and the reliability is excellent, 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 cathode lead wire to the cathode electrode which comprises the same capacitor | condenser element, (b) AA sectional drawing of the same figure (a) Cross-sectional view of the principal part showing a portion where the cathode lead wire is connected to the cathode electrode constituting the capacitor element Cross-sectional view of the principal part showing the part where the anode lead wire is connected to the anode electrode constituting the capacitor element (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 (3)

An anode electrode having a polarizable electrode layer formed on both sides of a current collector made of metal foil and having a lead wire connected to an exposed portion of the current collector provided on a part of the polarizable electrode layer; A capacitor element formed by winding a cathode electrode formed in the same manner with a separator interposed therebetween, a bottomed cylindrical metal case containing the capacitor element together with a driving electrolyte, and in the wound-type electric double layer capacitor comprising an opening of the metal case from the sealed opening member, opposed to each other via a connecting portion and the separator of the lead wires connected to the respective anode and cathode electrodes constituting the capacitor element It provided an exposed portion of the current collector to the anode electrode and the cathode electrode, the exposed area of the current collector of the electrode the lead wire is connected to the (A1), the exposed area of the collector of which facing the electrode ( 1) and the case, (A1) ≦ (B1) and the wound-type electric double layer capacitor. The winding according to claim 1, wherein the exposed area (B1) of the current collector of the electrode opposite to the exposed area (A1) of the current collector of the electrode to which the lead wire is connected is two times or less. Rotary electric double layer 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, on the outermost peripheral surface of the capacitor element, The wound electric double layer capacitor according to claim 1, wherein a portion where polarizable electrode layers formed on the cathode electrode face each other with a separator interposed therebetween is provided.

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