JP2010182922A - Electric double layer capacitor and method of manufacturing electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an electric double layer capacitor used for an automobile etc., compact and large in capacity. <P>SOLUTION: A first electrode 10 is formed by forming polarizable electrode layers 10b on a current collector 10a made of metal foil, and depositing an insulating fiber layer 10c comprising a three-dimensional structure having a plurality of superfine fibers bonded to resin particles on surfaces of the polarizable electrode layers 10b. A second electrode 11 is formed by forming a polarizable electrode layer 11b on a current collector 11a made of metal foil. At least a pair of capacitive elements 15 is formed by stacking the first electrode 10 and second electrode 11. The capacitive elements 15 are impregnated with an electrolyte for driving and are sealed with a housing body 12. Consequently, the insulating fiber layer 10c is greatly reduced in thickness to make the capacitive elements 15 compact, thereby reducing the size and increasing the capacity. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electric double layer capacitor used for backup power source, regeneration, or power storage of various electronic devices, hybrid vehicles and fuel cell vehicles.

  Conventionally, electric double layer capacitors have attracted attention and are used in many fields because of their high withstand voltage, large capacity, and high reliability of rapid charge / discharge. Such an electric double layer capacitor has a configuration in which a polarizable electrode mainly composed of activated carbon is used as an electrode for both the positive electrode and the negative electrode, and is stacked or wound through a separator between them, and withstand voltage as an electric double layer capacitor Is 1.2 V when an aqueous electrolyte is used, and 2.5 to 3.3 V when an organic electrolyte is used.

  Since the energy of an electric double layer capacitor is proportional to the square of the withstand voltage, an organic electrolyte with a higher withstand voltage has a higher energy than an aqueous electrolyte, but even with an electric double layer capacitor using an organic electrolyte And the energy density is 1/10 or less of secondary batteries, such as a lead acid battery, and the further improvement of an energy density is required.

  Furthermore, it is also known to use a separator such as polyethylene or polypropylene in order to improve the durability of such an electric double layer capacitor.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2001-185455 A

  However, in the conventional electric double layer capacitor, since the separator for insulation disposed between the positive electrode and the negative electrode has an independent sheet-like configuration, a thickness of about 25 μm is necessary in consideration of the manufacturing surface and strength. Therefore, there is a problem that it is difficult to further reduce the thickness.

  Therefore, it is difficult to reduce the size of an element formed by laminating or winding the positive electrode and the negative electrode with a separator interposed therebetween, and there is a problem that it is difficult to realize a small size and large capacity.

  On the other hand, electric double layer capacitors used for backup power sources, regenerative power storage, etc. for hybrid vehicles and fuel cell vehicles are required to have high energy density. Since the volume ratio of the polarizable electrode that can be stored in the electrode is reduced, the capacitance of the electric double layer capacitor is reduced and the contact area between the polarizable electrode and the current collector is also reduced. In this case, the current density per unit area of the polarizable electrode is increased, the internal resistance of the electric double layer capacitor is increased, and there is a problem in reliability such as life.

  Furthermore, in the laminated type, a current collector is disposed outside the polarizable electrode through a separator between a pair of polarizable electrodes, and the current collector is pressurized to thereby form the polarizable electrode and the driving electrolyte. Although the contact is improved and the internal resistance is kept low, there is a problem that the pressure is weakened by gas generation, and the separator impregnated with the driving electrolyte deteriorates the contact with the polarizable electrode layer and affects the life characteristics. is doing.

  An object of the present invention is to solve such a conventional problem and to provide a highly reliable electric double layer capacitor while reducing the size and increasing the capacity by reducing the thickness of the separator.

  In order to solve the above problems, the present invention provides a three-dimensional structure in which a polarizable electrode layer is formed on a current collector made of metal foil, and a plurality of ultrafine fibers are bonded to resin particles on the surface of the polarizable electrode layer. A first electrode on which an insulating fiber layer having the structure described above is deposited, a second electrode in which a polarizable electrode layer is formed on a current collector made of metal foil, and the first electrode and the second electrode are stacked. The capacitor element is configured to be impregnated with a driving electrolyte solution, and the capacitor element is sealed with an exterior body.

  Also, a polarizable electrode layer is formed on a current collector made of metal foil, and an insulating fiber layer having a three-dimensional structure composed of a plurality of ultrafine fibers bonded to resin particles is deposited on the surface of the polarizable electrode layer. Forming at least a pair of capacitor elements by superimposing a second electrode having a polarizable electrode layer on a current collector made of a metal foil on an insulating fiber layer of the first electrode. An electric double layer capacitor manufacturing method includes a forming step and a step of impregnating the capacitor element with a driving electrolyte and sealing the capacitor element with an exterior body.

  As described above, the electric double layer capacitor according to the present invention includes a first electrode in which an insulating fiber layer having a three-dimensional structure in which a plurality of ultrafine fibers are bonded to resin particles is deposited on the surface of a polarizable electrode layer. Thus, the driving electrolyte in which the polarizable electrode layer and the insulating fiber layer are integrated and impregnated in the insulating fiber layer is always in contact with the polarizable electrode layer, and a plurality of ultrafine fibers are in contact with the resin particles. Since it has a fiber layer consisting of a combined three-dimensional structure, it has a high mechanical strength and can hold a large amount of driving electrolyte, so it can maximize the double layer capacity and keep the internal resistance low. Can do. As a result, the charge / discharge characteristics and life characteristics of the electric double layer capacitor can be improved.

  In addition, compared to conventional electrodes and separators that are configured separately, the thickness of the separator can be significantly reduced and the mechanical strength is strong, so the elements can be downsized and the capacity can be increased. The effect that it can be realized is obtained.

  Furthermore, the insulating fiber layer deposited on the first electrode is formed by applying a voltage between the current collector of the first electrode and a nozzle for injecting a solution in which a resin is dissolved, whereby a plurality of ultrafine fibers are formed. Can form an insulating fiber layer composed of a three-dimensional structure in which the resin particles are bonded to the resin particles, so that the density of the insulating fiber layer can be made uniform and thin, and the internal resistance of the electric double layer capacitor can be reduced. Thus, the lifetime can be extended and a highly reliable electric double layer capacitor can be obtained.

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

  FIG. 1 is a cross-sectional view showing a configuration of an electric double layer capacitor according to Embodiment 1 of the present invention. In FIG. 1, 15 is a capacitor element, and includes a first electrode 10 (positive electrode) and a second electrode 11 ( Negative electrode). The first electrode 10 has a polarizable electrode layer 10b mainly composed of activated carbon formed on the upper and lower surfaces of an aluminum foil current collector 10a, and a plurality of ultrafine fibers are resin particles on the surface of the polarizable electrode layer 10b. Insulating fiber layer 10c having a three-dimensional structure structure bonded to is deposited. The second electrode 11 is formed by forming a polarizable electrode layer 11b mainly composed of activated carbon on one surface of an aluminum foil current collector 11a, and is disposed above and below the first electrode 10.

  Then, the external terminal 13 is connected to the current collector 10 a of the first electrode 10, and the external terminal 14 is also connected to each second electrode 11. Subsequently, the driving electrolyte is applied to the capacitor element 15. The electric double layer capacitor is constructed by impregnating and then covering with the outer package 12 so that the external terminals 13 and 14 are partially exposed.

  Next, a method for manufacturing the electric double layer capacitor will be described.

  First, as the first electrode 10, a high-purity aluminum foil (Al: 99.99% or more) having a thickness of 22 μm is used as the current collector 10 a, and the surface is roughened by electrolytic etching in a hydrochloric acid-based etching solution. Turn into.

  Subsequently, a phenol resin activated carbon powder having an average particle size of 5 μm, acetylene black having an average particle size of 0.05 μm as a conductivity-imparting agent, and water-soluble in which carboxymethyl cellulose (CMC) and polytetrafluoroethylene (PTFE) are dissolved as a binder. After the binder solution is mixed at a weight ratio of 10: 2: 1 and sufficiently kneaded with a kneader, methanol and water dispersion solvent is added little by little, and further kneaded to prepare a paste with a predetermined viscosity. Was applied to the upper and lower surfaces excluding one end of the current collector 10a and dried in the atmosphere at 85 ° C. for 5 minutes to form the polarizable electrode layer 10b.

  An insulating fiber layer 10c is deposited on the surface of the polarizable electrode layer 10b. The present invention is most characterized by depositing the insulating fiber layer 10c directly on the surface of the polarizable electrode layer 10b.

  The insulating fiber layer 10c is deposited by the method shown in FIG. That is, a current collector 10a in which a resin made of polybutylene terephthalate (PBT) is dissolved in an organic solvent, this solution is poured into a solution tank 18, and a nozzle 16 connected to the solution tank 18 and a polarizable electrode layer 10b are formed. Insulating fiber layer 10c having a three-dimensional structure in which a plurality of ultrafine fibers are bonded to resin particles by applying a high voltage of 10 to 50 kV between the two and spraying the solution from nozzle 16. Is deposited. A surface SEM photograph of the insulating fiber layer 10c is shown in FIG.

  The resin concentration is preferably in the range of 3 to 10% by weight, and if it is less than 3% by weight, the resin particles are large and the number of ultrafine fibers is reduced, which deteriorates the characteristics of the electric double layer capacitor. On the other hand, if the resin concentration exceeds 10% by weight, the three-dimensional structure is not formed, only the ultrafine fibers are deposited, the density of the insulating fiber layer is increased, and the internal resistance of the electric double layer capacitor cannot be reduced.

  The insulating fiber layer 10c has a thickness of 5 to 20 [mu] m, preferably 5 to 15 [mu] m.

  In addition to the polybutylene terephthalate (PBT), the resin used for the insulating fiber layer 10c is polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), aramid, polyimide. , Nylon, modified PP, modified PE, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) resin and cellulose can be used, but these resins cause hydrogen bonding with the polarizable electrode layer 10b. It is a preferable material because high bond strength can be obtained. Further, from the viewpoint of heat resistance, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), aramid, polyimide, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE) are more preferable.

  In addition, although resin is melt | dissolved in the organic solvent and it is set as the solution, it does not necessarily need to melt | dissolve in the solvent. For example, a fine resin dispersed in a solvent or an emulsion can be used.

  Next, the surface of the second electrode 11 is roughened by electrolytic etching in a hydrochloric acid-based etching solution using a high-purity aluminum foil (Al: 99.99% or more) having a thickness of 22 μm as a current collector 11a. Face. Subsequently, a phenol resin activated carbon powder having an average particle size of 5 μm, acetylene black having an average particle size of 0.05 μm as a conductivity-imparting agent, and water-soluble in which carboxymethyl cellulose (CMC) and polytetrafluoroethylene (PTFE) are dissolved as a binder. After the binder solution is mixed at a weight ratio of 10: 2: 1 and sufficiently kneaded with a kneader, methanol and water dispersion solvent is added little by little, and further kneaded to prepare a paste with a predetermined viscosity. Is applied to the surface of the current collector 11a and dried in the air at 85 ° C. for 5 minutes to form the polarizable electrode layer 10b.

  Next, the external terminal 13 is connected to the current collector 10 a of the first electrode 10, and the external terminal 14 is also connected to each second electrode 11. Subsequently, the overlapping capacitor element 15 is formed so that the second electrode 11 is disposed above and below the first electrode 10. The capacitor element 15 is impregnated with a driving electrolyte solution in which propylene carbonate is dissolved in 4-ethylammonium tetrafluoride, and then covered with an exterior body 12 made of an exterior resin so as to partially expose the external terminals 13 and 14. Thus, an electric double layer capacitor can be obtained.

  Here, a comparison between the initial characteristics and life characteristics of the electric double layer capacitor of the first embodiment and the electric double layer capacitor using a conventional separator as a comparative example is shown in (Table 1) (capacitor element size: 10). × 20 mm).

  In addition, as a forming condition of the insulating fiber layer 10c, a solution in which polybutylene terephthalate (PBT) resin is changed to 1, 3, 5, 8, 10, 12% by weight and dissolved in an organic solvent is used as a nozzle 16 and a current collector. A voltage of 20 kV was applied to 10a, and the distance was 20 cm. The thickness was adjusted by applying voltage. Further, an insulating fiber layer using polyphenylene sulfide (PPS), polyethylene terephthalate (PET), and polyvinylidene fluoride (PVDF) as a resin to be dissolved in an organic solvent was also produced. The comparative example was produced in the same manner as in Embodiment 1 except that solvent-spun recycled cellulose (thickness 25 μm) separators were arranged above and below the polarizable electrode layer.

  As can be seen from Table 1, the electric double layer capacitor of the insulating fiber layer deposited at a resin concentration of 3 to 10% by weight can draw out the maximum capacitance and keep the internal resistance low, so that the lifetime Also in the characteristics, the capacity change rate is reduced and the change in ESR is small.

  In addition, the thickness of the separator can be significantly reduced compared to the comparative example in which the electrode and the separator are separately configured, so that the element can be downsized and the capacity can be increased. The effect that it can be obtained.

  As described above, in the electric double layer capacitor according to the first embodiment, the insulating fiber layer having the configuration of the three-dimensional structure in which a plurality of ultrafine fibers are bonded to the resin particles is deposited on the surface of the polarizable electrode layer. With this electrode, the driving electrolyte in which the polarizable electrode layer and the insulating fiber layer are integrated and impregnated in the insulating fiber layer is always in contact with the polarizable electrode layer, and a plurality of ultrafine fibers are made of resin. Since it has a fiber layer composed of a three-dimensional structure bonded to the particles, it has a high mechanical strength and can hold a large amount of driving electrolyte, so that it can maximize the double layer capacity and reduce the internal resistance. Can be suppressed. As a result, the charge / discharge characteristics and life characteristics of the electric double layer capacitor can be improved.

  In the first embodiment, the configuration using one first electrode 10 of the capacitor element 15 has been described. However, as shown in FIG. 4, the capacitor element 15 using two first electrodes 10 is used. With the configuration, an electric double layer capacitor having a larger electrostatic capacity can be obtained.

  In the first embodiment, the exterior resin is used for the exterior body 12, but the capacitor element 15 can be sealed using a laminate resin film.

  Further, in the first embodiment, the structure using the laminated type is described, but the present invention is not limited to this, and can be used as a wound type capacitor element.

(Embodiment 2)
In the first embodiment, the first electrode (positive electrode) and the second electrode (negative electrode) on which the insulating fiber layer is formed are changed to the first electrode (negative electrode) and the second electrode (positive electrode). An electric double layer capacitor was fabricated in the same manner as in Embodiment 1.

  FIG. 5 is a cross-sectional view showing the configuration of the electric double layer capacitor according to the second embodiment of the present invention. In FIG. 5, reference numeral 25 denotes a capacitor element, which includes a first electrode 20 (negative electrode) and a second electrode 21 (positive electrode). In the first electrode 20, a polarizable electrode layer 20b mainly composed of activated carbon is formed on one surface of an aluminum foil current collector 20a, and a plurality of ultrafine fibers are formed on resin particles on the surface of the polarizable electrode layer 20b. Insulating fiber layer 20c having a combined three-dimensional structure is deposited and formed. The second electrode 21 is obtained by forming a polarizable electrode layer 21b mainly composed of activated carbon on both surfaces of an aluminum foil current collector 21a.

  Then, the external terminal 24 is connected to the current collector 20 a of the first electrode 20, the external terminal 23 is also connected to each second electrode 21, and the first electrode is formed above and below the second electrode 21. 20 are arranged to overlap.

  Thereafter, the capacitor element 25 is impregnated with a driving electrolyte, and the external terminals 23 and 24 are covered with the outer package 22 so as to expose part of the external terminals 23 and 24, thereby forming an electric double layer capacitor.

  The insulating fiber layer 20c is obtained by dissolving a fiber made of polyvinylidene fluoride (PVDF) in an organic solvent in the same manner as the forming method of FIG. 2 of the first embodiment, and this solution (PVDF concentration 8 wt%) 18, by applying a high voltage of 20 kV between the nozzle 16 connected to the solution tank 18 and the current collector 21 a on which the polarizable electrode layer 21 b is formed, and spraying the solution from the nozzle 16. Then, an insulating fiber layer 20c having a three-dimensional structure in which a plurality of ultrafine fibers are bonded to resin particles is deposited.

  A comparison of the initial characteristics and life characteristics of this electric double layer capacitor is shown in Table 1.

  As in the first embodiment, the electric double layer capacitor according to the second embodiment has a structure in which the polarizable electrode layer 20b and the insulating fiber layer 20c are integrated, so that the density of the insulating fiber layer 20c is uniform and thin. Since it can be formed and the internal resistance of the electric double layer capacitor can be reduced, the life can be extended and a highly reliable electric double layer capacitor can be obtained.

(Embodiment 3)
In the first embodiment, an electric double layer capacitor was fabricated in the same manner as in the first embodiment except that the insulating fiber layer was formed by the method shown in FIG.

  That is, a solution having a concentration of 8% by weight of polyvinylidene fluoride (PVDF) is injected into the solution tank 18, a solution having a concentration of 15% by weight of polyvinylidene fluoride (PVDF) is injected into the solution tank 19, and the nozzles 16 and 17 are collected. A voltage (20 kV) was applied between the electric body 10a and fibers were deposited on the surface of the polarizable electrode layer 10b.

  A comparison of the initial characteristics and life characteristics of this electric double layer capacitor is shown in Table 1.

  The electric double layer capacitor according to the third embodiment has a three-dimensional structure in which long fibers having a fiber diameter of 1 μm or less are entangled and deposited on a three-dimensional structure in which a plurality of ultrafine fibers are bonded to resin particles. The strength of the three-dimensional structure can be increased and the life characteristics of the electric double layer capacitor can be further improved.

  In addition, by using the solution with the same concentration of the resin concentration in the solution tanks 18 and 19 of 8% by weight, the fibers to be deposited are more entangled and the density for the same thickness can be increased. Can be achieved.

  The electric double layer capacitor according to the present invention has an effect that the separator can be thinned to reduce the size of the element and realize a small size and large capacity. In particular, the backup power source and regenerative power of a hybrid vehicle and a fuel cell vehicle can be realized. It is useful for use.

Sectional drawing which shows the structure of the electrical double layer capacitor by Embodiment 1 of this invention Schematic showing the method of forming the insulating fiber layer Surface SEM photo of the insulating fiber layer Sectional view showing examples of other capacitor elements Sectional drawing which shows the structure of the electrical double layer capacitor by Embodiment 2 of this invention Schematic which shows the formation method of the insulating fiber layer in Embodiment 3 of this invention

DESCRIPTION OF SYMBOLS 10 1st electrode 10a Current collector 10b Polarization electrode layer 10c Insulating fiber layer 11 2nd electrode 11a Current collector 11b Polarization electrode layer 12 Exterior body 13, 14 External terminal 15 Capacitor element

Claims (8)

A polarizable electrode layer is formed on a current collector made of metal foil, and an insulating fiber layer having a three-dimensional structure in which a plurality of ultrafine fibers are bonded to resin particles is deposited on the surface of the polarizable electrode layer. A first electrode; a second electrode in which a polarizable electrode layer is formed on a current collector made of a metal foil; and at least a pair of capacitor elements by overlapping the first electrode and the second electrode; and the capacitor element An electric double layer capacitor in which a driving electrolyte is impregnated and the capacitor element is sealed with an exterior body. 2. The electric double layer capacitor according to claim 1, wherein the insulating fiber layer is formed by entangled long fibers having a fiber diameter of 1 μm or less in a three-dimensional structure in which a plurality of ultrafine fibers are bonded to resin particles. The insulating fiber layer is composed of cellulose and polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), aramid, polyimide, nylon, modified PP, modified PE, polyfluoride. The electric double layer capacitor according to claim 1 or 2, comprising at least one selected from vinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). A polarizable electrode layer was formed on a current collector made of metal foil, and an insulating fiber layer having a three-dimensional structure composed of a plurality of ultrafine fibers bonded to resin particles was deposited on the surface of the polarizable electrode layer. A step of forming the first electrode and an insulating fiber layer of the first electrode are overlapped with a second electrode having a polarizable electrode layer formed on a current collector made of a metal foil to form at least a pair of capacitor elements. A method for producing an electric double layer capacitor comprising: a step; and a step of impregnating the capacitor element with a driving electrolyte and sealing the capacitor element with an exterior body. The insulating fiber layer is made of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), aramid, polyimide, nylon, modified PP, modified PE, polyvinylidene fluoride. (PVDF) or at least one resin selected from polytetrafluoroethylene (PTFE) is dissolved in an organic solvent, and a DC voltage is applied between the nozzle for injecting the solution and the current collector, and The method for manufacturing an electric double layer capacitor according to claim 4, wherein the electric double layer capacitor is deposited on a polar electrode. 6. The method for producing an electric double layer capacitor according to claim 5, wherein the concentration of the resin dissolved in the organic solvent is in the range of 3 to 10% by weight. 5. The electric double layer capacitor according to claim 4, wherein the insulating fiber layer is deposited by intertwining long fibers having a fiber diameter of 1 μm or less in a three-dimensional structure in which a plurality of ultrafine fibers are bonded to resin particles. Production method. 8. The method of manufacturing an electric double layer capacitor according to claim 7, wherein the insulating fiber layer is deposited by using at least two nozzles for injecting a solution in which a resin is dissolved in a solvent, and the resin concentration of the solution is different. .