JP2007080845A - Electric double layer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin and compact electric double layer capacitor that has a high degree of freedom in a shape to be manufactured, and has low internal resistance by using a coating type electrode. <P>SOLUTION: The electrodes comprise an active material layer and a collector layer by coating one surface of the collector layer with a coating liquid containing an active substance. The electrodes are allowed to oppose each other while sandwiching a separator so that the active material layers oppose each other. An electrolyte is contained in the electrodes and the separator to compose one cell, a conductor that is larger than a cell and is nearly plane is arranged on the uppermost and lowermost layers of the cell, a heat-bonding seal member is held between the opposing surfaces of the conductor projecting from the cell, and the entire periphery is adhered and sealed under a pressure-reduced environment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric double layer capacitor, and more particularly to a manufacturing method and a structure of a small and thin capacitor used for backup of a memory power source of a portable device.

  The electric double layer capacitor is charged and discharged by adsorption and desorption of ions, and unlike a secondary battery, it does not involve a chemical reaction, so that the electrolyte solution is hardly deteriorated and has a very long life.

  The physical adsorption / desorption by the movement of ions is faster than the chemical reaction, and the internal resistance is lower than that of the secondary battery, so that instantaneous charging and discharging of a large current are possible.

  At present, electric double layer capacitors are used for power backup of portable devices, power backup for memory and clock functions of printers, remote controllers, memory cards, game machines, etc., and instantaneous voltage drop compensation devices. Expectation is also expected in applications such as power supply and cogeneration.

  The structure of an electric double layer capacitor is such that a separator is sandwiched between electrodes in which an activated carbon sheet is in close contact with an aluminum foil current collector. In general, in the case of an electric double layer capacitor having a square structure, a stacked structure is used. In the case of an electric double layer capacitor having a cylindrical structure, the structure is wound.

  The electrode is manufactured by pasting a sheet of aluminum foil and activated carbon with a conductive resin, or by mixing activated carbon, a binder, and a solvent to produce a paint, and then applying it to an aluminum foil current collector. There are things to do.

  In the case of an electric double layer capacitor with a cylindrical structure, the cell cannot be made thin, and because of its round shape, when it is incorporated in an electronic device, a wasteful space is generated and used for a small electronic device. Not suitable for.

  In the case of an electric double layer capacitor having a square structure, a cell is fabricated by storing at least one pair of stacked electrodes sandwiching a separator together with an electrolyte in a metal can or aluminum laminate outer package.

  When manufacturing an electric double layer capacitor having a square structure, when a metal can is used as an exterior body, there is a drawback that it is excellent in strength and reliability, but is expensive. Further, when an aluminum laminate outer package is used, the cost is excellent, but there is a problem that the strength is weak and the sealing performance of the heat seal portion is low (particularly the lead wire drawing portion). Several methods for solving these problems have been proposed (see, for example, Patent Document 1 and Patent Document 2).

  This aluminum laminate has a three-layer structure in which resin films are bonded to both sides of an aluminum foil. Nylon or polyethylene terephthalate (PET) is used for the film on the front side of the bag, and polypropylene (PP) or polyethylene (PE) is used for the inner film.

  The shape of the outer package that has been sealed with the laminated body (see, for example, Patent Document 3) has a large space on the outer periphery of the bag and is excellent in thinness, but has a problem in size. . Moreover, in order to eliminate this defect, the thing of the structure which bends the outer peripheral part of a bag is shown (for example, refer patent document 4). However, in this structure, stress is applied to the bag of an aluminum laminate at the time of bending, Pinholes may occur. If there is a hole in the bag, moisture in the atmosphere will intrude into the bag, hindering its function as a battery or capacitor.

  Therefore, a capacitor that can be made thin and small without using a metal can or an aluminum laminate bag has been introduced (for example, see Patent Document 5). In the case of this structure, it seems that there is no problem in the manufacturing process with the type in which the aluminum foil as the current collector and the activated carbon sheet are bonded with a conductive resin, but the capacitor of this structure using coated electrodes In the case of trying to make a coating process, the electrode paint cannot be applied to the entire surface of the current collector of the aluminum foil, so the manufacturing process is limited to methods such as applying after masking or forming a coating film by printing. The problem is pointed out. Further, in the case of the electric double layer capacitor having this structure, since the electrode is sealed after being impregnated with the electrolytic solution, it is necessary to take measures to prevent the electrolytic solution from adhering to the sealing surface, and the manufacturing process becomes complicated as a whole.

  Furthermore, it is known that the internal resistance increases when the adhesion of the active material layer, the separator, and the current collector in the electric double layer capacitor is weak. Further, when gas is generated inside the container and the container swells, there is a problem that the adhesion between the electrodes deteriorates and the internal resistance increases. As a method for solving this problem, a decompression method (for example, see Patent Document 6) for moving the gas generated by the decomposition of the electrolytic solution to largely suppress the decrease in the capacitance, and an external device such as a bolt or a spring are used. There has been proposed a method of generating pressure and applying pressure to the cell to press the cell or electrode (see, for example, Patent Document 7 and Patent Document 8).

  In the case of these methods, the mechanism for pressurization becomes large, which is not suitable when an electric double layer capacitor is to be downsized.

JP 2003-157810 A JP 2001-148234 A JP 2000-58014 A JP 2000-138040 A JP 2002-313679 A JP-A-9-162082 JP 2002-289485 JP 2001-284176 A

  As described above, various improvements have been made to the structure and manufacturing method of the electric double layer capacitor, but all have advantages and disadvantages. In particular, the current collector aluminum foil and the activated carbon sheet are bonded with a conductive resin. In the case of an electric double layer capacitor manufactured in this manner, there is a certain limit to the thinness and miniaturization of the capacitor due to the manufacturing process. In addition, there are certain limits to the shapes that can be produced, and it is extremely difficult to produce complex shapes. In particular, in recent small electronic devices, the space for storing the electric double layer capacitor as a part is extremely small, and it is required to be stored in a small space, and the space is not only a simple shape such as a rectangle, There are many complicated shapes such as irregular shapes, and the electric double layer capacitor is also required to have a complicated shape, and the internal resistance is also required to be reduced. However, it is difficult to satisfy these requirements.

  The present invention has been made to eliminate the drawbacks of the prior art described above. An electric double layer capacitor that uses a coating electrode and does not use an external mechanism such as a bolt or a spring and meets the demand for space saving is provided. An object of the present invention is to provide an electric double layer capacitor that uses a coated electrode, is thin and small, has a high degree of freedom in manufacturing shape, and has a low internal resistance. To do.

  In order to achieve the above object, the present invention provides, as one aspect thereof, an electrode comprising an active material layer and a current collector layer by applying a coating liquid containing an active material to one surface of the current collector layer. The two electrodes are made to face each other across the separator so that the active material layers face each other, and an electrolyte is contained in the electrode and the separator to form one cell, and the uppermost layer and the lowermost layer of the cell A substantially planar conductor having a shape larger than that of the cell is disposed, and a heat bonding seal member is sandwiched between the opposing surfaces of the conductor protruding from the cell, and the entire periphery is adhered and sealed in a reduced pressure environment. An electric double layer capacitor is provided.

  In another aspect of the present invention, an electrode comprising an active material layer and a current collector layer is formed by applying a coating solution containing an active material to one surface of the current collector layer, Two electrodes are opposed to each other with a separator sandwiched so that the active material layers face each other, an electrolyte is contained in the electrode and the separator to form one cell, and two or more of the cells are stacked, A substantially planar conductor is disposed between the uppermost layer and the lowermost layer of the stacked laminate and between the cells, and a heat bonding seal member is sandwiched between the opposing surfaces of the conductor protruding from the laminate, and the pressure is reduced. Provided is an electric double layer capacitor characterized in that it is adhered and sealed all around in an environment.

  Furthermore, as another aspect of the present invention, an electrode composed of an active material layer and a current collector layer is formed by applying a coating solution containing an active material to one surface of the current collector layer, and the electrode 2 The cells are made to face each other with the separator sandwiched so that the active material layers face each other, and an electrolyte is contained in the electrode and the separator to form one cell, and the uppermost layer and the lowermost layer of the cell are larger than the cell. Convex and concave conductors are placed so that the protrusions face each other, and a heat bonding seal member is sandwiched between the opposing surfaces of the conductors protruding from the cell, and bonded over the entire circumference in a reduced pressure environment or atmospheric pressure. An electric double layer capacitor characterized by being sealed.

  In another aspect of the present invention, an electrode comprising an active material layer and a current collector layer is formed by applying a coating solution containing an active material to one surface of the current collector layer, The two electrodes are opposed to each other with a separator sandwiched so that the active material layers face each other, an electrolyte is contained in the electrode and the separator to form one cell, and two or more of the cells are arranged in a stack. A conductor with protrusions and recesses larger than the cells is placed on the top and bottom layers of the stacked body so that the protrusions face each other. A conductive conductor is arranged, a heat-adhesive seal member is sandwiched between opposing surfaces of each conductor protruding from the laminated body, and is adhered and sealed over the entire circumference in a reduced pressure environment or atmospheric pressure. An electric double layer capacitor is provided.

  Further, according to another aspect of the present invention, in the electric double layer capacitor, the electrode composed of the active material layer and the current collector layer is folded in a zigzag manner via a separator. An electric double layer capacitor is provided.

  The electric double layer capacitor of the present invention was able to produce a thin, small and free-shaped capacitor with low internal resistance by using a coated electrode without using an outer bag such as a metal can or an aluminum laminate. . As a result, it is possible to satisfy the requirements for the shape and capacity increase required for the electric double layer capacitor as a component used in recent small electronic devices.

The configuration of the electric double layer capacitor of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of the electric double layer capacitor of the present invention.
As shown in FIG. 1, the electric double layer capacitor is an electric double layer capacitor having a square structure and is a flat plate type. In this electric double layer capacitor, an electrode composed of an active material layer 1 and a current collector layer 2 is produced by applying a coating solution containing an active material to one surface of the current collector layer 2. The cells are made to face each other with the separator 3 sandwiched so that the active material layers 1 face each other, and an electrode and the separator are mixed with an electrolyte to form a single cell. A substantially planar conductor 4 is arranged between the uppermost layer and the lowermost layer of the laminated body and between the cells, and a heat bonding seal member 5 is sandwiched between the opposing surfaces of the conductor 4 protruding from the laminated body. , Bonded and sealed over the entire circumference in a reduced pressure environment.

  Here, in the present invention, it is possible to provide a thin and small electric double layer capacitor without using an outer package such as a metal can and an aluminum laminate, and further, using a coating type electrode and punching with a press as desired. By forming the electrode shape, a complicated shape, for example, a round shape, a rectangular shape such as a square shape, or an irregular shape can be obtained. In particular, in the present invention, by performing thermocompression bonding in a reduced pressure environment, The internal resistance of the multilayer capacitor is greatly reduced.

  With regard to the pressure reduction condition when producing the electric double layer capacitor of the present invention, the effect of reducing the increase in internal resistance of the electric double layer capacitor, which is the object of the present invention, is sufficiently exhibited if the pressure reduction condition is lower than −40.0 kpa. There is no particular limitation.

  Moreover, what was shown with the dotted line of the conductor 4 in FIG. 1 shows another aspect of the electric double layer capacitor of this invention. That is, in this embodiment, a conductor 4 provided with a dome-shaped dimple is used with its convex portions facing each other, and an electric double layer capacitor is manufactured by the same method as in the above embodiment. In this embodiment, it is not always necessary to perform thermocompression bonding under a reduced pressure environment, but it is more preferable to perform thermocompression bonding under a reduced pressure environment.

  When a conductor provided with a dome-shaped dimple is used, since the convex portions are opposed to each other, a force for pressing the electrode with an elastic force is applied, and the internal resistance can be reduced. Further, in addition to the use of the conductor provided with the dome-shaped dimple, if thermocompression bonding is performed in a reduced pressure environment, a further significant effect of reducing the internal resistance can be obtained.

  In FIG. 1, an electric double layer capacitor having a configuration in which two cells are stacked is shown. However, an electric double layer capacitor having a configuration in which one cell is used, that is, two electrodes are used, or a configuration in which three or more cells are stacked. The electric double layer capacitor can be manufactured by the same method, and the electrodes constituting the electric double layer capacitor can also be configured to have a structure folded in a zigzag manner with the separator interposed therebetween.

Hereinafter, preferred embodiments of the present invention will be described by way of specific examples.
The electrode and capacitor according to the present invention were produced by the following method.

(1) Production of electrode An electrode to be a polarizable electrode was produced by the following procedure. The activated carbon material (particle size: 5 to 10 μm) subjected to the activation treatment, the binder (fluororubber), and the conductive auxiliary agent (acetylene black) have a mass ratio of carbon material: binder: conductive auxiliary agent = 80. : 10:10, blended into MIBK (methyl isobutyl ketone) as solvent, (activated carbon, binder, conductive aid): MIBK is 100: 270, kneaded Thus, a coating solution for forming an electrode (viscosity: 3000 to 5000 cps) was prepared.

  Next, this coating solution was uniformly applied on one surface of a current collector (thickness: 50 μm) made of an aluminum foil. Thereafter, MIBK is removed from the coating film by drying treatment, and further rolled using a calender roll (for the purpose of increasing the density of the coating film and improving the adhesiveness) on one surface of the current collector. An electrode on which an electron conductive porous layer (thickness: 37 μm) was formed was produced.

  Next, vacuum drying is performed at a temperature of 150 ° C. to 175 ° C. for 12 hours or more to remove moisture adsorbed on the surface and inside of the electron conductive porous layer, and an electrode used for an electric double layer capacitor is produced. did. This electrode was punched out with a press to obtain a desired shape.

  In the case of the present invention, the electrode and the cell shape can be produced in a round shape or an irregular shape in addition to the rectangular shape.

  Small electronic devices in recent years have a small space, and when storing parts such as secondary batteries and capacitors, it is required to fit in a small space, and the space is often not a rectangular shape but is often required to have an irregular shape. .

(2) Production of Capacitor First, the coated electrodes of the produced electrode are opposed to each other, and a separator (thickness: 0.03 mm, manufactured by Nippon Kogyo Paper Industries Co., Ltd., trade name: “TF4030”) is formed between them. A cell (element body) was formed by placing and thermocompression bonding. This cell was pressed into a substantially planar shape.

Example 1
The cell is immersed in an electrolytic solution (solvent: propylene carbonate; electrolyte: triethylmethylammonium tetrafluoroborate; 1.2 to 1.8 mol / liter used per liter of electrolytic solution; manufactured by Toyama Pharmaceutical Co., Ltd.) Soak the electrolyte in the separator, remove it, wipe off the electrolyte attached to the aluminum current collector, place two cells in series, and then place a conductor larger than the laminate in the upper, lower, and intermediate layers. (Al) is disposed, and a cylindrical heat-bonding seal member (modified PP) with both end surfaces open is sandwiched between opposing surfaces of the conductor protruding from the laminated body, and under reduced pressure (-92.0 to -93. The electric double layer capacitor of the present invention was manufactured by thermally bonding to the conductor over the entire circumference at 0 kpa) and sealing.
At this time, the upper and lower conductors were provided with projections and depressions so that the projections face each other so as to contact the cell side, and a force to push the electrode by the pressing force of the projections was generated.

(Example 2)
This cell is immersed in the electrolytic solution, soaked in the coating film or separator, and the electrolytic solution attached to the aluminum current collector is removed, and two cells are arranged in series, and the upper layer In addition, a conductor (Al) larger than the laminated body is disposed in the lower layer and the intermediate layer, and a cylindrical heat-bonding seal member (modified PP) having both ends open is sandwiched between the opposing surfaces of the conductor protruding from the laminated body. Then, the electric double layer capacitor of the present invention was produced by thermally bonding and sealing the conductor over the entire circumference in a reduced pressure environment (-92.0 to -93.0 kpa).
At this time, the upper and lower conductors were not provided with irregularities, and those having a substantially planar shape were used.

(Example 3)
This cell was immersed in an electrolytic solution so that the electrolytic solution was soaked into a coating film or a separator, taken out, and attached to the aluminum current collector portion.
The electrolyte is wiped off, two cells are placed in series, and a conductor (Al) larger than the laminate is placed in the upper, lower, and intermediate layers, and the opposing surface of the conductor protruding from the laminate A cylindrical heat-adhesive seal member (modified PP) with both end faces open was sandwiched between them, thermally bonded to the conductor over the entire circumference under an atmosphere of 1 atm, and sealed to produce the electric double layer capacitor of the present invention. .
At this time, the upper and lower conductors were provided with projections and depressions so that the projections face each other so as to contact the cell side, and a force to push the electrode by the pressing force of the projections was generated.

(Comparative Example 1)
Immerse this cell in the electrolytic solution, soak the electrolytic solution in the coating film or separator, take it out, wipe off the electrolytic solution adhering to the aluminum current collector, place two cells in series, and then upper In addition, a conductor (Al) larger than the laminated body is disposed in the lower layer and the intermediate layer, and a cylindrical heat-bonding seal member (modified PP) having both ends open is sandwiched between the opposing surfaces of the conductor protruding from the laminated body. The electric double layer capacitor of the present invention was manufactured by thermally bonding and sealing the conductor over the entire circumference under an atmosphere of 1 atm.
At this time, the upper and lower conductors were not provided with irregularities, and those having a substantially planar shape were used.
The reduction effect of the increase in internal resistance in the electric double layer capacitors produced in the above examples and comparative examples was compared by the resistance value increase rate. The results are shown in Table 1.

抵抗値上昇率は、（（シール後抵抗値−シール前抵抗値）／シール前抵抗値）×１００により決定した。
減圧環境下で熱接着した場合（実施例１及び２）は上層・下層の導電体が大気圧によってセルを押しつける力が働き、導電体、電極、セパレータの密着がよくなって内部抵抗を低減できる。

The rate of increase in resistance value was determined by ((resistance value after sealing−resistance value before sealing) / resistance value before sealing) × 100.
When heat bonding is performed in a reduced pressure environment (Examples 1 and 2), the force of the upper and lower conductors pressing the cell by atmospheric pressure works, and the close contact between the conductors, electrodes, and separators improves the internal resistance. .

Also, by providing irregularities on the upper and lower conductors, making the projections face each other and sealing (Examples 1 and 3), the force that presses the cells against the projections works, and the conductor, electrode, and separator are in close contact with each other. The internal resistance rise can be reduced.
On the other hand, in the case where the upper and lower conductors were not provided with irregularities and further thermocompression bonding was not performed in a reduced pressure environment (Comparative Example 1), the effect of reducing the increase in internal resistance was not observed.
Although this embodiment is implemented with two series cells, it is obvious to those skilled in the art that the same effect can be expected with a single cell or three series cells.

  The electric double layer capacitor using the coated electrode of the present invention can be produced even if the electrode and cell shape are round or irregular shapes other than rectangular shapes, and accommodates parts such as secondary batteries and capacitors. This is useful for small electronic devices in recent years where space is required to be narrowed. Capacitors can be provided with extremely low internal resistance due to the thermocompression effect in a reduced pressure environment by providing irregularities on the conductor. It can be suitably used for the use of small electronic devices.

It is sectional drawing which shows an example of the electrical double layer capacitor which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Active material layer 2 Current collector layer 3 Separator 4 Conductor 5 Thermal bonding seal member

Claims (5)

  An electrode composed of an active material layer and a current collector layer is formed by applying a coating liquid containing the active material to one surface of the current collector layer, and the two active electrodes are faced to each other. The electrode and the separator are made to face each other with an electrolyte solution, and one cell is formed, and a substantially planar conductor having a shape larger than the cell is disposed on the uppermost layer and the lowermost layer of the cell, An electric double layer capacitor comprising a heat bonding seal member sandwiched between opposing surfaces of a conductor protruding from the cell, and bonded and sealed over the entire circumference in a reduced pressure environment.   An electrode composed of an active material layer and a current collector layer is formed by applying a coating liquid containing the active material to one surface of the current collector layer, and the two active electrodes are faced to each other. The electrode and the separator are made to face each other with an electrolyte, and one cell is formed, and two or more of the cells are stacked, and the uppermost layer, the lowermost layer, and the cell of the stacked body in which the cells are stacked A substantially planar conductor is disposed between the two, and a thermal adhesive seal member is sandwiched between the opposing surfaces of the conductor protruding from the laminate, and the entire circumference is adhered and sealed in a reduced pressure environment. An electric double layer capacitor characterized.   An electrode composed of an active material layer and a current collector layer is formed by applying a coating liquid containing the active material to one surface of the current collector layer, and the two active electrodes are faced to each other. The electrode and the separator are made to face each other with an electrolyte solution, and one cell is formed, and a conductor having protrusions and recesses in a shape larger than the cell on the uppermost layer and the lowermost layer of the cell is formed between the protrusions. Are disposed so as to oppose each other, and a thermoadhesive seal member is sandwiched between opposing surfaces of the conductor protruding from the cell, and is bonded and sealed over the entire circumference in a reduced pressure environment or atmospheric pressure. Multilayer capacitor.   An electrode composed of an active material layer and a current collector layer is formed by applying a coating liquid containing the active material to one surface of the current collector layer, and the two active electrodes are faced to each other. The electrode and the separator are made to face each other with an electrolyte solution, and one cell is formed. Two or more of the cells are stacked, and the uppermost layer and the lowermost layer of the stacked body are the cells. A conductor with projections and recesses with a larger shape is arranged so that the protrusions face each other, and a substantially planar conductor with a shape larger than the cell is placed between the cells, and protrudes from the laminate. An electric double layer capacitor characterized in that a heat bonding seal member is sandwiched between opposing surfaces of each conductor, and is bonded and sealed over the entire circumference in a reduced pressure environment or atmospheric pressure. 5. The electric double layer capacitor according to claim 1, wherein the electrode composed of an active material layer and a current collector layer has a structure folded in a serpentine shape with a separator interposed therebetween.

Images