Capacitor Module

Abstract

To provide an electric double layer capacitor having a simple structure and in which a current collector does not peel off even when a high voltage is applied. [Solution] The capacitor component 10 of this electric double layer capacitor 30 comprises a separator 12, two polarizable electrodes 14, one on each side of the separator 12, two current collectors 16, one on each side of the two polarizable electrodes 14, and an electrolyte in contact with the two polarizable electrodes 14, and the current collector 16 has a liquid-permeable reinforcing sheet 26 and an expanded graphite sheet 24 laminated thereon.

Description

[Technical field]

[0001] The present invention relates to an electric double layer capacitor capable of being charged and discharged. Equipped The present invention relates to a capacitor module. [Background technology]

[0002] Electric double layer capacitors are used in various electronic devices due to their advantages of being able to store a large amount of charge due to their large capacitance, being able to charge and discharge quickly due to their low internal resistance, and having a long charge and discharge cycle life due to little deterioration due to charging and discharging. Electric double layer capacitors have polarizable electrodes on both sides of a separator, the separator and polarizable electrodes are impregnated with an electrolyte, and a current collector is provided on the outside of each polarizable electrode. The polarizable electrodes are granular porous materials (usually activated carbon) with a large surface area bound together with a binder to increase the capacitance. At the interface between the polarizable electrodes and the electrolyte on both sides of the separator, the charges in the polarizable electrodes and the ions in the electrolyte form an electric double layer, and charges are accumulated. Metal foil (usually aluminum foil) is used as the current collector.

[0003] For rapid charging and discharging of a large amount of charge, it is preferable that the internal resistance between the current collector and the polarizable electrode is small and stable. For this purpose, various technologies have been proposed in the past. Patent Document 1 describes a conductive intermediate layer containing synthetic rubber and two or more types of carbon materials with different particle sizes interposed between the current collector and the polarizable electrode. Patent Document 2 describes a conductive adhesive layer containing carbon particles and a polymer not containing epoxy groups as a binder interposed between the current collector and the polarizable electrode. Patent Document 3 describes a layer made of a material showing an immersion potential that is more base than activated carbon and more noble than aluminum, provided on the surface of an aluminum foil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-136401 A [Patent Document 2] JP 2010-171212 A [Patent Document 3] JP 2008-91563 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the current collector is made of aluminum, applying a high voltage of about 2.4 V or more during charging can cause the current collector to peel off from the polarizable electrode due to oxidation of the current collector, etc., so it was necessary to keep the voltage that could be applied low.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric double layer capacitor that has a simple structure and is capable of increasing the voltage that can be applied. Particularly useful for To provide a capacitor module. [Means for solving the problem]

[0007] In order to achieve the above object, the capacitor module described in claim 1 includes an electric double layer capacitor and a case for housing the electric double layer capacitor, the case including an inner expanded graphite sheet for the case which is press-formed into a sheet shape, an outer liquid-permeable reinforcing sheet for the case which reinforces the expanded graphite sheet for the case so as not to break, It is composed of . Effect of the Invention

[0008] The present invention provides an electric double layer capacitor that has a simple structure and can increase the voltage that can be applied. Particularly useful for It becomes possible to provide a capacitor module. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of an electric double layer capacitor according to an embodiment of the present invention. [Diagram 2] 2A and 2B are schematic cross-sectional views showing a capacitor configuration of the electric double layer capacitor of FIG. 1, in which (a) shows the configuration and (b) shows an enlarged view of the vicinity of the lower current collector in (a). [Diagram 3] FIG. 2 is a diagram showing a process for producing the electric double layer capacitor of FIG. 1, in which (a) is a schematic cross-sectional view showing a process for coating activated carbon particles, and (b) is a schematic cross-sectional view showing a process for assembling current collectors. [Figure 4] 2 is a schematic cross-sectional view showing a capacitor module including the electric double layer capacitor of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 30 denotes a The capacitor module may include 1 shows an electric double layer capacitor 30. The electric double layer capacitor 30 has a plurality of capacitor components 10.

[0011] (composition) As shown in FIG. 2(a), the capacitor component 10 is composed of a separator 12, two polarizable electrodes 14, 14, one on each side of the separator 12, two current collectors 16, 16, one on each side of the two polarizable electrodes 14, 14, and an electrolyte in contact with the two polarizable electrodes 14, 14.

[0012] The separator 12 is not particularly limited as long as it is a liquid-permeable material that is not melted or corroded by the electrolyte, and may be, for example, paper, nonwoven fabric, etc. The thickness of the separator 12 is, for example, 5 to 40 μm.

[0013] The polarizable electrode 14 is generally formed of a number of activated carbon particles 20 (for example, particle size 1 to 10 μm) (see FIG. 2(b)) and a binder, and has electrical conductivity. The activated carbon particles 20 are not particularly limited, but may be made from waste plastic (for example, waste PET (polyethylene terephthalate) is processed into flakes and then carbonized by a carbonizer). A known binder may be used. A conductive assistant, a dispersant, and the like may be added to these as appropriate. A nanomaterial such as nanofiber may also be added. The polarizable electrode 14 has a thickness of, for example, 50 to 500 μm.

[0014] The electrolyte is impregnated into the entire two polarizable electrodes 14 (and the entire separator 12) and is in contact with them. As the electrolyte, for example, a triethylmethylammonium tetrafluoroborate (TEMABF4) / propylene carbonate (PC) solution is used.

[0015] The current collector 16 has a liquid-permeable reinforcing sheet 26 and an expanded graphite sheet 24 laminated on the liquid-permeable reinforcing sheet 26 (see FIG. 2(a)). The liquid-permeable reinforcing sheet 26 reinforces the expanded graphite sheet 24 so that it is not damaged when tension or the like is applied. The expanded graphite sheet 24 has a thickness of, for example, 20 to 100 μm, and the liquid-permeable reinforcing sheet 26 has a thickness of, for example, 20 to 100 μm. The expanded graphite sheet 24 and the liquid-permeable reinforcing sheet 26 are bonded together by, for example, an adhesive or an adhesive sheet. The liquid-permeable reinforcing sheet 26 (and the adhesive or adhesive sheet bonding the liquid-permeable reinforcing sheet 26 to the expanded graphite sheet 24) can be made conductive by adding a conductive assistant or the like.

[0016] The expanded graphite sheet 24 is formed, for example, by subjecting scaly graphite to a high-temperature expansion treatment and then pressing it into a sheet. The thermal conductivity of the expanded graphite sheet 24 in the thickness direction is 5 to 20 W / (m·K), and the thermal conductivity of the expanded graphite sheet 24 in the plane direction is 200 to 350 W / (m·K). The thermal diffusivity of the expanded graphite sheet 24 in the plane direction is approximately 3 cm 2The expanded graphite sheet 24 is conductive, with an electrical resistivity in the thickness direction of about 1000 μΩ·m and an electrical resistivity in the plane direction of about 7 μΩ·m.

[0017] The liquid-permeable reinforcing sheet 26 has liquid permeability and is made of paper, nonwoven fabric, or the like. (Action and Effects)

[0018] In the capacitor component 10, the expanded graphite sheet 24 made of carbon comes into contact with the polarizable electrode 14 made of carbon (activated carbon) in the current collector 16. This provides good affinity between the polarizable electrode 14 and the expanded graphite sheet 24. This prevents the current collector 16 from peeling off from the polarizable electrode 14 due to oxidation of the current collector or the like, even when a high voltage (for example, about 2.4 to about 7 V) is applied, unlike when the current collector 16 is made of aluminum.

[0019] In the capacitor component 10, the current collector 16 is made of an expanded graphite sheet 24 having a high thermal diffusivity in the surface direction (the thermal diffusivity of aluminum in the surface direction is about 0.98 cm 2 / s, the thermal diffusivity of the expanded graphite sheet in the plane direction is about 3 cm 2 / s), the heat generated in the resistance component when a voltage is applied is quickly diffused throughout the current collector 16. This prevents heat from concentrating in one part of the current collector 16, and reduces the thermal stress on the current collector 16.

[0020] In the electric double layer capacitor 30, the capacitor components 10 are multi-layered while sharing the current collector 16. Therefore, the current collector 16 is configured to have two layers of expanded graphite sheets 24 and one layer of liquid-permeable reinforcing sheet 26 sandwiched between the two layers of expanded graphite sheets 24.

[0021] The electric double layer capacitor 30 can be manufactured as follows. First, as shown in FIG. 3(a), a large number of activated carbon particles 20 mixed with a binder or the like (not shown) are coated in a predetermined shape on both sides of a material sheet 32 ​​that will later become a current collector 16. At this time, tension is applied to the material sheet 32, but the liquid-permeable reinforcing sheet 26 of the material sheet 32 ​​prevents damage. The coated parts are then dried to form polarizable electrodes 14, and the material sheet 32 ​​is then cut into regions including the coated parts and wiring parts (uncoated parts) described below. Then, a plurality of current collectors 16 with polarizable electrodes 14 attached to both sides are sandwiched between sheets of separator 12 folded in a zigzag shape. When manufactured in this manner, the polarizable electrodes 14 are necessarily attached to both sides of the current collector 16 in the electric double layer capacitor 30, and the polarizable electrodes 14 that do not constitute the capacitor-constituting part 10 are attached to the ends of the electric double layer capacitor 30 (see FIG. 1). In addition, in the electric double layer capacitor 30 shown in FIG. 1, a separator 12 is provided on the outermost side.

[0022] The current collectors 16 are bonded together at their wiring portions (uncoated portions) by a conductive adhesive (an adhesive made conductive by adding a conductive assistant or the like) 34 for each positive electrode or negative electrode. In this case, when the wiring portions of the current collectors 16 are immersed (dipped) in the liquid conductive adhesive 34 and then dried, the current collectors 16 can be electrically connected to each other as shown in FIG. 3(b), and the conductive adhesive 34 permeates the liquid-permeable reinforcing sheet 26 of the current collector 16, and the two layers of expanded graphite sheets 24, 24 of the current collector 16 can be electrically connected to each other well. The wiring portions of the current collectors 16 thus assembled are connected to a positive electrode terminal 44 or a negative electrode terminal 46 of a capacitor module 36 described later, or may be used as the positive electrode terminal 44 or the negative electrode terminal 46 as they are.

[0023] A capacitor module 36 using the electric double layer capacitor 30 is shown in FIG. 4. The capacitor module 36 is configured to include the electric double layer capacitor 30 and a case 38 that houses the electric double layer capacitor 30. The case 38 is configured to include an inner expanded graphite sheet 40 for the case and an outer liquid-permeable reinforcing sheet 42 for the case. A positive electrode terminal 44 and a negative electrode terminal 46 are fixed to the case 38. In FIG. 4, the positive electrode terminal 44 is disposed in front of the negative electrode terminal 46 (shown by a broken line). The positive electrode terminal 44 and the negative electrode terminal 46 are connected to the multiple expanded graphite sheets 24 on the positive electrode side of the electric double layer capacitor 30 or the multiple expanded graphite sheets 24 on the negative electrode side of the electric double layer capacitor 30, respectively, via the wiring portion of the current collector 16. In FIG. 4, the wiring portion of the current collector 16 from the positive electrode terminal 44 is shown by a solid line, and from the negative electrode terminal 46 is shown by a broken line. The expanded graphite sheet 40 for the case can be the same as the expanded graphite sheet 24 described above. The liquid-permeable reinforcing sheet for case 42 can be the same as the liquid-permeable reinforcing sheet 26 described above.

[0024] According to the capacitor module 36, the inside of the case 38 is constructed from the expanded graphite sheet for the case 40, so that even if the electrolyte penetrates into the gap 48 between the electric double layer capacitor 30 and the case 38, the case 38 is prevented from being oxidized and corroded.

[0025] Although the embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to the embodiment shown in the drawings, and various design modifications are possible within the scope of the claims. For example, in the electric double layer capacitor 30, the number of capacitor components 10 is not limited at all. [Explanation of symbols]

[0026] 10: Capacitor component 12: Separator 14: Polarizable electrode 16: Current collector 18: Polarizable electrode 20:Activated carbon particles 24: Expanded graphite sheet 26: Liquid-permeable reinforcement sheet 30: Electric double layer capacitor 32: Material sheet 34: Conductive adhesive 36: Capacitor module 38: Case 40: Expanded graphite sheet for case 42: Liquid-permeable reinforcing sheet for cases 44: Positive terminal 46: Negative terminal

Claims

[Claim 1] An electric double layer capacitor and a case for housing the electric double layer capacitor, The case is a capacitor module composed of an inner case-use expandable graphite sheet pressed into a sheet shape, and an outer case-use liquid-permeable reinforcing sheet that reinforces the case-use expandable graphite sheet so that it does not break.

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