JP2007208103A - Method for manufacturing electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a further reduced resistance is required for an electric double layer capacitor used for a hybrid car or the like, and to provide a method for manufacturing the electric double layer capacitor capable of providing its reduced resistance. <P>SOLUTION: The method for manufacturing the electric double layer capacitor comprises the steps of forming a capacitor element by winding a pair of positive and negative electrodes with a polarizable electrode layer formed on a power collecting body comprising a metal foil formed through a separator between them, housing the capacitor element in a case together with an electrolytic solution, taking out the positive and negative electrodes of the capacitor element, and sealing the case. The separator comprises a polyvinylidene fluoride or its polymer; and providing a pretreatment process for preliminarily immersing the separator in an alkaline solution, pulling out, water washing, and drying it reduces the resistance value of the separator to reduce the resistance of the electric double layer capacitor. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a method of manufacturing an electric double layer capacitor used for regeneration of various electronic devices, hybrid cars, fuel cell cars, or power storage.

  FIGS. 5A and 5B are an exploded perspective view showing the structure of this type of electric double layer capacitor and a developed perspective view showing the structure of the capacitor element used in the capacitor. Indicates a capacitor element. The capacitor element 1 is constituted by winding an anode electrode 2 and a cathode electrode 3 with a separator 4 interposed therebetween.

  The anode electrode 2 and the cathode electrode 3 are configured by forming polarizable electrode layers (not shown) on both surfaces of a current collector (not shown) made of metal foil, An anode lead wire 5 and a cathode lead wire 6 are connected to the anode electrode 2 and the cathode electrode 3, respectively.

  The capacitor element 1 configured in this manner is inserted into the bottomed cylindrical metal case 7 after impregnating a driving electrolyte solution (not shown), and a hole through which the anode lead wire 5 and the cathode lead wire 6 are inserted. After the rubber sealing member 8 having the above is disposed in the opening of the metal case 7, the outer periphery of the opening of the metal case 7 is drawn into an annular shape and sealed.

  The polarizable electrode layer formed on the anode electrode 2 and the cathode electrode 3 is prepared by mixing activated carbon powder, carbon black as a conductivity-imparting agent, and a water-soluble binder of polytetrafluoroethylene and carboxymethylcellulose as a binder. A paste is prepared by sufficiently kneading with a machine, and this paste is formed by applying and drying the paste on the front and back surfaces of a current collector made of aluminum foil.

  Since the conventional electric double layer capacitor configured as described above can be charged and discharged rapidly, it can be used for various electronic devices, power storage, and other applications such as regenerative use of hybrid cars and fuel cell vehicles. It was something that has come to be used.

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

  However, in recent market demands, a reduction in size and capacity is strongly desired, and this tendency is particularly remarkable in applications for automobiles. In order to meet such a demand, in the conventional electric double layer capacitor, studies are being made to reduce the resistance value and to increase the size and capacity by devising the electrode extraction method of the capacitor element 1 or the like. However, there is a problem that it is indispensable to reduce the resistance value of the capacitor element 1 itself because there is a limit only by such a device.

  An object of the present invention is to solve such a conventional problem and to provide a method for manufacturing an electric double layer capacitor capable of realizing a small size and a large capacity by reducing the resistance value of the capacitor element itself. Is.

  In order to solve the above problems, the present invention provides a capacitor element by winding or laminating a pair of positive and negative electrodes, each having a polarizable electrode layer formed on a current collector made of metal foil, with a separator interposed therebetween. Forming the capacitor element together with the driving electrolyte solution, housing the capacitor element in the case, extracting the positive and negative electrodes constituting the capacitor element to the outside, sealing the case opening and sealing the case In the method for producing an electric double layer capacitor having a step, the separator constituting the capacitor element is composed of polyvinylidene fluoride or the polymer, and the separator is previously immersed in an alkaline aqueous solution, pulled up and washed with water. The method is provided with a pretreatment step for drying.

  As described above, in the method for producing an electric double layer capacitor according to the present invention, the separator is made of polyvinylidene fluoride or a polymer thereof, and the separator is previously immersed in an alkaline aqueous solution, pulled up, washed with water, and then dried. Since a part of the molecular bond of the material constituting the separator is changed by this, and the resistance value of the separator can be reduced, the resistance of the capacitor element itself can be reduced by using this separator. It is possible to obtain an effect that it is possible to realize a reduction in resistance of the electric double layer capacitor by reducing the value.

(Embodiment)
Hereinafter, the invention described in the entire claims of the present invention will be described using embodiments. Note that the configuration of the electric double layer capacitor is the same as that described with reference to FIGS. 5A and 5B in the background art section, and thus the description thereof is omitted to avoid duplication.

  FIG. 1 is a manufacturing process diagram showing a method for manufacturing an electric double layer capacitor according to an embodiment of the present invention, and FIG. 2 is a manufacturing process diagram showing in detail a separator pretreatment process in the manufacturing process. The manufacturing method of the electric double layer capacitor according to the present embodiment will be described with reference to FIG. 2. First, a separator made of polyvinylidene fluoride or this polymer is used, and this separator is immersed in an alkaline aqueous solution. At that time, it is desirable to immerse in ethanol as a pretreatment for improving wettability. Moreover, the said alkaline aqueous solution used the 2.5M density | concentration using sodium hydroxide, made the liquid temperature 25 degreeC, and was immersed in this for 10 minutes.

  Subsequently, the separator was pulled up from the alkaline aqueous solution, washed with water, and then dried in an atmosphere at 60 ° C. for 10 minutes to pretreat the separator.

  Next, an anode electrode and a cathode electrode separately prepared by forming a polarizable electrode layer on a current collector made of metal foil are prepared, and wound with the separator interposed between the pair of electrodes. Thus, a capacitor element was formed.

  Next, the capacitor element is impregnated with a driving electrolyte and accommodated in a bottomed cylindrical metal case, and an anode lead wire and a cathode lead wire connected to a pair of electrodes of the capacitor element and drawn out, respectively. Is inserted into the through hole provided in the rubber sealing member, and the sealing member is fitted into the opening of the metal case, and then the vicinity of the opening end of the metal case is drawn into an annular shape, and the opening end is curled. Sealing was performed by processing to produce an electric double layer capacitor.

  Moreover, about the pre-processing of the said separator, it experimented by changing the kind of alkali aqueous solution, a density | concentration, liquid temperature, and immersion time, and the result of having measured the resistance value of these separators is shown to Fig.3 (a)-(c). The results obtained are shown in Table 1 in comparison with a conventional product as a comparative example (produced using the same material and not pretreated).

  As is clear from Table 1, the separator according to the present embodiment can reduce the comparison value by 12.8% as compared with the conventional product that has not been pretreated.

  Therefore, if a capacitor element is produced using a separator with such a low resistance, it is possible to reduce the resistance of an electric double layer capacitor using this capacitor element. The results of measuring the resistance value of an electric double layer capacitor configured using a separator according to form are compared with a conventional product as a comparative example (using a separator that has not been pretreated using the same material) (Table 2).

  As is clear from Table 2, the electric double layer capacitor according to the present embodiment uses a separator that has been pretreated to reduce the resistance, so that the electric double layer capacitor has a resistance of about 5 as compared with a conventional product that is not pretreated. It is possible to reduce the resistance value by 6%, and it is possible to reduce the resistance of the electric double layer capacitor without making a major structural change or providing a special manufacturing process. is there.

In addition, the reduction of the resistance value by such a pre-treatment of the separator is caused by immersing the separator made of polyvinylidene fluoride or this polymer in an alkaline aqueous solution, so that part of molecular bonds of the material constituting the separator is changed. This is confirmed by Fourier transform infrared spectroscopy, and it is presumed that the resistance value is reduced by the change of the molecular bond. FIG. 4 shows the measurement results obtained by the Fourier transform infrared spectroscopy. As is clear from FIG. 4, the separator according to the present invention has a peak generated in the vicinity of 850 cm ^{−1 of the} conventional product without pretreatment. Can be seen to disappear.

  Polyvinylidene fluoride is presumed that an electron-attracting fluorine atom is bonded to a carbon chain, and intramolecular polarization is caused by the inducing effect of the fluorine atom. Therefore, it is presumed that the electrolyte cation that electrophoreses in the separator is electrically attracted by negatively polarized fluorine atoms, and the electrolyte anion is electrically attracted by positively polarized carbon atoms. .

  However, when the separator is immersed in an alkaline aqueous solution, electron donation to the polyvinylidene fluoride by the base occurs, and the polyvinylidene fluoride is resonance-stabilized, so that intramolecular polarization is suppressed. It is presumed that the electric attractive force received from the separator is reduced and the resistance value is reduced.

  In the present embodiment, the example of using sodium hydroxide as the alkaline aqueous solution used for the pretreatment of the separator has been described. However, the present invention is not limited to this, and potassium hydroxide, aqueous ammonia solution, etc. May be used.

  Also, the concentration of the alkaline aqueous solution is such that the effect of reducing the resistance value is obtained in the range of 0.5 to 8M, and more preferably in the range of 2 to 8M.

  Moreover, if the temperature of aqueous alkali solution is also within the range of 10-50 degreeC, the effect of reducing a resistance value will be acquired.

  Moreover, also about the immersion time in alkaline aqueous solution, the reduction effect of resistance value is acquired in the range for 5 to 30 minutes.

  As described above, the method for manufacturing the electric double layer capacitor according to the present embodiment can reduce the resistance value of the separator by providing a pretreatment step for alkali treatment of the separator. This makes it possible to reduce the resistance of the electric double layer capacitor.

  The method for producing an electric double layer capacitor according to the present invention has an effect that resistance can be reduced by a simple method, and is particularly useful as an electric double layer capacitor used for automobiles.

Manufacturing process diagram showing a method of manufacturing an electric double layer capacitor according to an embodiment of the present invention Manufacturing process diagram showing the separator pretreatment process in detail in the same manufacturing process (A) Characteristic diagram showing resistance value improvement rate due to alkali aqueous solution concentration in separator pretreatment step, (b) Characteristic diagram showing resistance value improvement rate due to liquid temperature, (c) Resistance value improvement due to same immersion time Characteristic chart showing rate Characteristic diagram showing the measurement results of the separator by Fourier transform infrared spectroscopy (A) Exploded perspective view showing configuration of electric double layer capacitor, (b) Exploded perspective view

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Anode electrode 3 Cathode electrode 4 Separator 5 Anode lead wire 6 Cathode lead wire 7 Metal case 8 Sealing member

Claims (4)

A step of forming a capacitor element by winding or laminating a pair of positive and negative electrodes having a polarizable electrode layer formed on a current collector made of metal foil with a separator interposed therebetween, and driving the capacitor element Manufacture of an electric double layer capacitor having a step of housing in a case together with an electrolytic solution, a step of taking out positive and negative electrodes constituting the capacitor element, and a step of sealing and sealing the opening of the case In the method, the separator constituting the capacitor element is made of polyvinylidene fluoride or a polymer thereof, and the separator is preliminarily immersed in an alkaline aqueous solution, pulled up, washed with water, and dried, and then provided with a pretreatment step Capacitor manufacturing method. The method for producing an electric double layer capacitor according to claim 1, wherein sodium hydroxide is used as the alkaline aqueous solution in the pretreatment step applied to the separator, and the concentration thereof is 0.5 to 8M. The method for producing an electric double layer capacitor according to claim 1, wherein the temperature of the alkaline aqueous solution in the pretreatment step applied to the separator is 10 to 50 ° C. The method for producing an electric double layer capacitor according to claim 1, wherein the immersion time of the separator in the alkaline aqueous solution in the pretreatment step applied to the separator is 5 to 30 minutes.

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