JP2007201118A5 - - Google Patents

Description

Winding type electric double layer capacitor

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

4 (a) to 4 (c) are cross-sectional views showing the configuration of a conventional wound electric double layer capacitor of this type, a developed perspective view showing the configuration of a capacitor element used in the capacitor, and the capacitor element. In FIG. 4 , reference numeral 31 denotes a capacitor element. The capacitor element 31 is accommodated in a metal case 38 together with a metal plate 37 and a driving electrolyte (not shown), and the opening of the metal case 38 is sealed. A wound electric double layer capacitor is configured by sealing with a terminal plate 40 via a stop rubber 39.

  Here, the capacitor element 31 will be described in detail. Capacitor element 31 is formed by laminating and winding strip-shaped anode foil 32 and cathode foil 33 via strip-shaped separator 34, and anode foil 32 is provided with an extraction electrode 35 on one end surface orthogonal to the longitudinal direction, The cathode foil 33 is configured to have an extraction electrode 36 on the other end surface orthogonal to the longitudinal direction.

  Further, the anode foil 32 and the cathode foil 33 will be described in detail. Both the anode foil 32 and the cathode foil 33 are electrodes formed by forming a polarizable electrode layer on the surface of a metal foil (not shown) and having substantially the same dimensions. This polarizable electrode layer was prepared by mixing activated carbon powder, carbon black as a conductivity-imparting agent, and a water-soluble binder of polytetrafluoroethylene and carboxymethylcellulose (hereinafter abbreviated as CMC) as a binder and kneading them thoroughly with a kneader. The paste is applied to the surface of the metal foil and dried.

  The extraction electrodes 35 and 36 are joined to the inner bottom surface of the metal case 38 and the inner surface of the metal plate 37 by welding, respectively. The metal case 38 and the metal plate 37 are connected to external terminals 41 and 42, respectively.

  Further, in order to improve the connection between the metal case 38 and the metal plate 37, a polarizable electrode layer is formed on the surface of the anode foil 32 and the cathode foil 33 excluding the end of the metal foil, or the end of the metal foil By removing the polarization electrode layer formed on the surface of the portion, the end portions where the polarizable electrode layer is not formed may be used as the extraction electrodes 35 and 36.

  Further, as the conventional example, the outermost periphery of the capacitor element 31 is shown to be composed of the cathode foil 33. However, when the polarizable electrode layers are formed on both surfaces of the metal foil, the metal case 38 and the polarizable electrode layers are formed. You may comprise so that the separator 34 may become an outermost periphery so that a contact may be avoided.

As prior art document information relating to this application, for example, Patent Document 1 is known.
JP 2000-315632 A

In the above-described conventional wound electric double layer capacitor, the anode foil 32 and the cathode foil 33 are designed to have the same electrostatic capacity, and have the same size and shape. When a voltage is applied to the capacitor, the anode foil 32 and the cathode foil 33 are polarized at the same potential as the natural potential, and electric charges are formed on the surfaces of the respective electrodes. Deterioration of characteristics such as generation, resistance increase, and capacity decrease has occurred.

In particular, when the anode foil 32 and the cathode foil 33 are wound with the separator 34 interposed, the anode foil 32 is longer than the cathode foil 33 and the anode foil 32 protrudes at the end of winding of the capacitor element 31. When used for a long time, the driving electrolyte causes a chemical reaction between the end of winding of the cathode foil 33 and the anode foil 32, and the electrolyte anions BF ₄ ⁻ , PF ₆ ^{− and the} like are attracted to the anode foil 32 side, There was a possibility that the separator 34 would be deteriorated due to the peripheral portion becoming acidic.

  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 an electrode and has little characteristic deterioration. is there.

In order to solve the above problems, the present invention comprises a metal case containing a capacitor element together with a driving electrolyte, and a terminal plate for sealing an opening of the metal case. The capacitor element includes a strip-shaped separator. The anode foil is configured to be wound with the anode foil on the inside by overlapping the strip-like anode foil and the cathode foil, and the anode foil is a first extraction electrode on one end surface orthogonal to the longitudinal direction, the cathode foil is In the wound electric double layer capacitor having the second lead electrode on the other end surface orthogonal to the longitudinal direction, the cathode foil is wound at least longer than the end of the anode foil. is there.

As described above, the wound electric double layer capacitor according to the present invention has a longer cathode foil of the capacitor element and is wound so as to be longer than at the end of winding of the anode foil. It is possible to set the potential of the electrode in an electrochemically stable region where members such as foil and cathode foil do not cause an electrochemical reaction. In addition, since the cathode foil is provided on the outermost peripheral surface of the capacitor element, the electrolyte anions such as BF ₄ ⁻ and PF ₆ ⁻ are not concentrated on the surface of the anode foil, so that the separator becomes acidic. There is no risk of deterioration. As a result, gas generation due to electrochemical reaction, resistance increase and capacity decrease are eliminated, and an effect of realizing a highly reliable wound type electric double layer capacitor with little characteristic deterioration can be obtained. is there.

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

FIGS. 1A and 1B are a developed 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, and a configuration at the end of winding. In FIG. 1 , reference numeral 1 denotes a capacitor element. The capacitor element 1 includes a metal case (not shown, for example, a cylindrical shape whose upper surface is open) that is accommodated together with a driving electrolyte, and the metal case. This is for forming a wound electric double layer capacitor composed of a disk-shaped terminal plate whose opening is sealed with a sealing rubber.

The capacitor element 1 will be described in detail. In the capacitor element 1, the strip-like anode foil 2 and the cathode foil 3 are overlapped with each other via the strip-like separator 4 and wound with the anode foil 2 inside. Winding is longer than the end of winding of the anode foil 2 (in FIG. 1 , the cathode foil 3 is made longer than the anode foil 2 by L2 so that the outermost peripheral surface is formed by the cathode foil 3), and the end of winding is illustrated. The configuration is such that it is stopped by a tape that does not.

  The anode foil 2 has an extraction electrode 7 which is an end portion of the anode foil 2 on one end surface orthogonal to the longitudinal direction. Similarly, the cathode foil 3 has an end portion of the cathode foil 3 on the other end surface orthogonal to the longitudinal direction. A certain extraction electrode 8 is provided. The anode foil 2 and the cathode foil 3 are obtained by forming polarizable electrode layers 5 and 6 to be described later on both surfaces of a metal foil excluding the end portions to be the extraction electrode 7 and the extraction electrode 8, respectively.

  Then, after the capacitor element 1 thus configured is impregnated with the driving electrolyte and inserted into the bottomed cylindrical metal case, the terminal plate is opened through the sealing rubber through the opening of the metal case. The opening of the metal case is sealed by performing lateral drawing and curling, and the extraction electrode 7 and the extraction electrode 8 are welded to the inner bottom surface of the metal case and the inner surface of the terminal plate, respectively. By connecting, a wound electric double layer capacitor is configured.

Incidentally, the metal foil, driving electrolyte, a metal case, none of the sealing rubber and the terminal plate is not shown, is similar to the conventional example of FIG.

  Further, as the activated carbon powder constituting the polarizable electrode layers 5 and 6 formed on the anode foil 2 and the cathode foil 3, respectively, charcoal, coconut shell, phenol resin, petroleum coke, coal coke, pitch Those obtained by activating these raw materials are used.

Further, 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.

In this way, the cathode foil 3 of the capacitor element 1 is wound longer than the winding end of the anode foil 2 and the outermost periphery of the capacitor element 1 is formed by the cathode foil 3, so that the driving electrolyte or anode foil is formed. 2. The potential of the anode foil 2 and the cathode foil 3 is set in an electrochemically stable region where members such as the cathode foil 3 do not cause an electrochemical reaction. Further, since electrolyte anions such as BF ₄ ⁻ and PF ₆ ⁻ are not concentrated on the surface of the anode foil 2 and become acidic, the separator 4 is not deteriorated, and as a result, an electrochemical reaction occurs. Gas generation, resistance increase, and capacity decrease are eliminated, and a highly reliable wound electric double layer capacitor with little characteristic deterioration can be obtained.

Further, FIG. 2 shows a configuration of the winding start of the capacitor element 1 used in the wound electric double layer capacitor according to the embodiment of the present invention. The anode foil 2 and the cathode foil 3 are overlapped to form the anode foil. When winding with the inner side 2 facing, at least one portion of the cathode foil 3 is wound first by the innermost circumferential diameter L3 first, whereby the anode foil 2 and the cathode foil at the innermost circumference of the capacitor element 1 are started. By setting the potential of 3 in an electrochemically stable region, characteristic deterioration is further reduced.

Further, FIG. 3 shows a configuration at the end of winding of the capacitor element 1 used in the wound electric double layer capacitor according to the embodiment of the present invention. The width perpendicular to the longitudinal direction of the cathode foil 3 is set as the anode. By making it wider than the width orthogonal to the longitudinal direction of the foil 2, the capacitor element is configured such that the end portion orthogonal to the longitudinal direction of the anode foil 2 on the end surface of the capacitor element 1 is opposed to the cathode foil 3. It is possible to set the potential of the anode foil 2 and the cathode foil 3 at the end face of 1 to a more electrochemically stable region, and the characteristic deterioration is further reduced.

  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 foil, 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 surfaces excluding the end of the aluminum foil. The polarizable electrode layer is formed by using a phenol resin-based activated carbon powder having an average particle size of 5 μm, a 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: After mixing at a weight ratio of 1 and sufficiently kneading with a kneader, methanol and water dispersion solvent was added little by little to further knead to produce a paste having a predetermined viscosity, and this paste was then added to the aluminum foil. The film was applied to the surface of the film and dried in the air at 100 ° C. for 1 hour to form.

Next, an aluminum foil having a polarizable electrode layer having a thickness of 60 μm formed on both surfaces except for the upper end 5 mm was cut into dimensions of 45 × 475 mm on the anode side and 45 × 510 mm on the cathode side, and the anode foil 2 and the cathode foil 3 was obtained. The upper ends where the polarizable electrode layers are not formed are the extraction electrodes 7 and 8, respectively.

Thereafter, the anode foil 2 and the cathode foil 3 are overlapped with each other via a separator 4 having a width of 42 mm and a thickness of 35 μm between the anode foil 2 and the cathode foil 3, and the anode foil 2 is placed inside by using a φ6.0 mm core. Wrap it like this. At this time, the cathode foil 3 was 35 mm longer than the anode foil 2, but because of the thickness of the electrode and the separator, the cathode foil 3 was wound 8 mm longer than the end of the winding of the anode foil 2 and had a portion where the cathode foil 3 overlapped. Capacitor element 1 (winding diameter: φ16.5 mm) could be obtained.

  Next, the capacitor element 1 was impregnated with a driving electrolyte. As the driving electrolyte, a solution obtained by dissolving tetraethylammonium fluoroborate in propylene carbonate was used.

  Thereafter, the capacitor element 1 is inserted into a bottomed cylindrical aluminum case, sealed with a terminal plate through a sealing rubber, and the capacitor element 1 is placed in a recess provided on the inner bottom surface of the aluminum case and the inner surface of the terminal plate. Each of the lead electrodes 7 and 8 on the end face was connected by welding to produce a wound electric double layer capacitor (capacitor dimension: φ20 × 50 mm).

In order to improve the bonding between the extraction electrodes 7 and 8, recesses are provided on the inner bottom surface of the aluminum case and the inner surface of the terminal plate. However, the inner surfaces of the extraction electrodes 7 and 8 and the aluminum case and the inner surface of the terminal plate are good. In the case where easy joining is obtained, the concave portion need not be provided.

  Even when the lead electrode of the cathode foil 3 is joined to the aluminum case in order to prevent peeling of the polarizable electrode layer due to contact between the polarizable electrode layer and the aluminum case, and to improve productivity, the capacitor element 1 can have the highest capacity. It is better to configure the outer periphery with a separator 4.

  A wound electric double layer capacitor was manufactured using the capacitor element 1 thus obtained (capacitor dimension: φ20 × 50 mm).

(Example 2 )
In Example 1 , only the cathode foil 3 is wound at least one turn at the beginning of winding, and then the cathode foil 3 and the anode foil 2 are wound together, so that the innermost circumference of the capacitor element 1 is the cathode foil 3. The configuration and manufacturing method other than the configuration described above were obtained by using the description of Example 1 to produce a wound electric double layer capacitor.

Specifically, as shown in FIG. 2 , an anode foil 2 and a cathode foil 3 obtained by cutting an aluminum foil having a polarizable electrode layer into a dimension of 45 × 475 mm on the anode side and 45 × 525 mm on the cathode side are used. A capacitor element in which the cathode foil 3 is placed 19 mm longer than the anode foil 2 at the beginning of winding and wound using a φ6.0 mm core so that only the cathode foil 3 is wound first. 1 was used to produce a wound electric double layer capacitor (capacitor dimension: φ20 × 50 mm).

  In the present embodiment, the cathode foil 3 was wound in the drawn-out state, but the same effect can be obtained by placing the cathode foil 3 and the anode foil 2 at the same position and winding the cathode foil 3 inside. It is what

(Example 3 )
In Example 1 , by making the width orthogonal to the longitudinal direction of the cathode foil 3 wider than the width orthogonal to the longitudinal direction of the anode foil 2, the end surface portion of the capacitor element 1 is orthogonal to the longitudinal direction of the anode foil 2. The configuration and the manufacturing method except that the end portion increases the portion facing the cathode foil 3 were used to make the wound electric double layer capacitor by using the description of Example 1 .

Specifically, as shown in FIG. 3 , the aluminum foil on which the polarizable electrode layer is formed is used as the anode foil 2, the width W1 of the polarizable electrode layer 5 is 40 mm, the width W3 of the extraction electrode 7 is 7 mm, and the cathode foil 3 The separator 4 having a width W2 of the polarizable electrode layer 6 of 42 mm and a width W4 of the extraction electrode 8 of 5 mm and a separator 4 having a width of 43 mm and a thickness of 35 μm were used.

  The anode foil 2 and the cathode foil 3 are overlapped and wound via the separator 4 so that at least the polarizable electrode layer 5 is positioned inside the polarizable electrode layer 6 in a width orthogonal to the longitudinal direction of the anode foil 2. Thus, the capacitor element 1 in which the end of the polarizable electrode layer 5 formed on the anode foil 2 is opposed to the polarizable electrode layer 6 formed on the cathode foil 3 on the end face of the capacitor element 1 is used. Thus, a wound electric double layer capacitor was produced (capacitor dimension: φ20 × 50 mm).

(Comparative Example 1)
In Example 1, the anode side is 46 × 475 mm, the cathode side is 45 × 490 mm, the separator width is 42 mm , and the cathode foil 3 is wound inside (the cathode foil 3 is 15 mm longer than the anode foil 2). However, the outermost periphery (56.55 mm) of the anode foil 2 cannot be surrounded, and the anode foil 2 protrudes) . For other configurations and manufacturing methods, the winding type electric double layer capacitor was manufactured by using the description of Example 1 (capacitor size: φ20 × 50 mm).

Regarding the wound electric double layer capacitors of Examples 1 to 3 and Comparative Example 1, initial characteristics (capacitance, DC capacitor resistance (hereinafter abbreviated as DCR)) and characteristic deterioration test when 2.3 V is applied at 85 ° C. Went. The results are shown in (Table 1). Note that the number of tests was 20.

  The DCR was charged and then discharged, and the slope of 0.5 to 2.0 sec at the start was calculated.

  As apparent from Table 1, the wound electric double layer capacitor of the present invention has a smaller capacity change than Comparative Example 1, and ΔC, ΔDCR, and product swelling in the characteristic deterioration test are significantly larger than those of Comparative Example. It was possible to improve.

Thus, in the present invention, the cathode foil 3 is wound longer than the end of the anode foil 2, so that the outermost periphery of the capacitor element 1 is surrounded by the cathode foil 3. It becomes possible to set the potentials of the anode foil 2 and the cathode foil 3 in an electrochemically stable region where members such as the foil 2 and the cathode foil 3 do not cause an electrochemical reaction.

Moreover, since the electrolyte anions BF ₄ ⁻ , PF ₆ ^−, etc. in the electrolytic solution are not concentrated and become acidic on the surface of the anode foil 2, there is no deterioration of the separator 4. Since gas generation, resistance increase, and capacitance change due to the occurrence are eliminated, a highly reliable wound electric double layer capacitor with little deterioration in characteristics can be obtained.

  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 as an in-vehicle electronic device circuit.

(A) is the expansion | deployment perspective view which showed the structure of the capacitor | condenser element used for the winding type | mold electric double layer capacitor of Example 1 in one embodiment of this invention , (b) is the end of winding of the same capacitor | condenser element. Development of the main part showing the relationship between the longitudinal dimension of the anode foil and the cathode foil The principal part expanded view which showed the positional relationship of the anode foil and cathode foil in the winding start of the capacitor | condenser element in Example 2 The principal part expanded view which showed the relationship of the width dimension of anode foil and cathode foil in the end of winding of the capacitor | condenser element in Example 3 (A) is sectional drawing which showed the structure of the conventional winding type electric double layer capacitor, (b) is the expansion | deployment perspective view which showed the structure of the capacitor | condenser element used for the same figure capacitor, (c) is the capacitor | condenser of the figure The perspective view which showed the capacitor element used for

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode foil 3 Cathode foil 4 Separator 5,6 Polarization electrode layer 7,8 Lead electrode

Claims (3)

A metal case containing the capacitor element together with a driving electrode solution; and a terminal plate for sealing the opening of the metal case. The capacitor element is overlapped with the belt-like anode foil and the cathode foil via a belt-like separator. The anode foil is wound with the anode foil inside, and the anode foil has a first extraction electrode on one end surface orthogonal to the longitudinal direction, and the cathode foil has a second electrode on the other end surface orthogonal to the longitudinal direction. A wound type electric double layer capacitor having a lead electrode, wherein the cathode foil is wound at least longer than the end of the winding of the anode foil. 2. The wound electric double layer capacitor according to claim 1 , wherein the cathode foil and the anode foil are wound together after winding the cathode foil at least one turn at the beginning of winding. The wound electric double layer capacitor according to claim 1 or 2 , wherein a width perpendicular to the longitudinal direction of the cathode foil is wider than a width perpendicular to the longitudinal direction of the anode foil.

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