JP2006032874A - Electrochemical device and manufacturing method for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical device which has such a structure that allows a metal foil having active material layers on both sides faces thereof to be used as a rolled material and enables quick output of a large quantity of currents. <P>SOLUTION: According to the electrochemical device, a pair of electrodes, each made by forming the active materials on both side faces of the metal foil, are superposed via an insulating separator, and are folded zigzag to form a lamination. The lamination has folded ends on the opposite side faces thereof, and the active material layers of the folded ends are eliminated to expose metal foil surfaces, respectively. The metal foil exposed part at each side face is joined electrically to a conductive plate that corresponds to each side face. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention particularly relates to an electrochemical device such as a lithium ion secondary battery and an electric double layer capacitor, and a method for producing the same. More specifically, the present invention relates to an electrochemical device characterized by a laminated structure of an electrode portion, and a method for manufacturing the electrochemical device.

  In recent years, secondary batteries are often used as power sources mounted on electronic devices, and electric double layer capacitors are being used for applications such as backup power sources. These electronic devices are being added with various functions at the same time as being miniaturized, and the power source used is also required to be miniaturized, lightened, and improved in performance. As a form of a battery or a capacitor corresponding to the request, an electrode laminate type is given. The electrode laminate type has a higher degree of freedom in shape than the so-called wound type, and can increase the storage efficiency.

  It is known that an electric double layer capacitor is charged and discharged by adsorption / desorption of ions, and therefore, unlike a secondary battery with a chemical reaction, there is no deterioration of an electrolyte and a very long life. In addition, the physical adsorption and desorption of ions is faster than the chemical reaction, and the internal resistance is small compared to the secondary battery due to the structure. Therefore, the electric double layer capacitor can be charged instantaneously or discharged with a large current. Make it possible. For this reason, the electric double layer capacitor is used for a backup of a portable device power supply, a memory of a printer or the like, a backup of a clock function, a compensation device for an instantaneous voltage drop, or the like. There are also expectations for applications such as auxiliary power and cogeneration for hybrid vehicles.

  The electric double layer capacitor also has an electrode winding type and an electrode laminated type, and the cell structure is similar to that of a lithium ion secondary battery. In the electrode winding type, a cylindrical can made of metal is generally used as an exterior body. Therefore, while the strength of the exterior body is high and the resistance to the use environment is high, there is a drawback in that volume efficiency is poor such that a dead space is generated when the exterior body is incorporated inside the apparatus. The electrode stack type uses a rectangular metal can, resin housing, aluminum laminate material, etc. for the exterior body, has a small dead space when incorporated into other devices, and has a high volumetric efficiency, making the entire device thinner and smaller. Can contribute.

  Here, the structure of the multilayer electric double layer capacitor will be described. Both the positive electrode and the negative electrode are obtained by forming an activated carbon layer on one or both sides of a foil made of a metal such as aluminum. The metal foil also has a portion where no activated carbon layer exists. This portion is called a tab portion, a lead portion, or an external terminal connection portion, is related to electrical conduction during charging / discharging, and is used by being connected to an external terminal directly or via a conductive additional member. Such an electrode is obtained by punching a desired region including a non-formed portion of the activated carbon layer from a metal foil.

JP 2003-157835 A Japanese Patent Laid-Open No. 10-214616 Japanese Patent Application Laid-Open No. 07-094374 Japanese Patent Laid-Open No. 11-274004 Japanese Patent Laid-Open No. 06-140077 JP 2003-100350 A

  Thus, when a layer made of an active substance is formed on a long metal foil, for example, when the layer is formed by a coating process, a desired electrode is obtained at the time of punching, and a coating portion and a non-coating portion are separated. It is necessary to make the boundary substantially linear. Since the coating material containing the active substance is in a liquid state and needs to be applied to the traveling metal foil, it is extremely difficult to obtain a boundary according to the required accuracy. Furthermore, when this is applied to both sides, it is necessary to make the boundary coincide on both sides, and it becomes more difficult to satisfy the requirement.

  In addition, the coated electrode is generally rolled from the viewpoint of improving the density of the coating film. When a metal foil with or without such a coating film is rolled, the strength rolling is applied only to the portion where the coating film exists, resulting in uneven stretching of the metal foil as a whole. As a result, it is conceivable that the metal foil is bent, the metal foil is wrinkled, and further the metal foil is cut. In order to deal with such a phenomenon, Patent Document 1 or 2 discloses a technique of rolling a metal foil while making the non-application area as small as possible. However, in these techniques, it is necessary to form a non-coating region with respect to a predetermined place on a long metal foil that travels, and in the implementation, the coating process is complicated or highly precise. With deployment.

  Moreover, in the laminated body mentioned above, an electrode, a separator, and a conductive shim must be sequentially laminated in each layer. This configuration is intended for the case where the number of stacked electrodes is several tens or several hundreds, but when there are a large number of configurations to be stacked in this way, the time required for the production of the stacked body becomes longer and the production There is a high possibility of causing a decrease in efficiency. Further, since the tab portion is not so strong, it is not easy to suitably place a conductive shim on the tab portion, and it is difficult to improve the production efficiency of the laminate also from this viewpoint. I think that the.

  Further, although aluminum foil is often used as the metal foil, it is generally known that aluminum easily forms a strong insulating oxide film on its surface. Therefore, in the case of the configuration using such an aluminum foil, it is difficult to obtain electrical continuity when an electrical connection with the spacer is obtained by simple surface contact. In addition, if the tab portion having a small thickness is simply accessed from the end face after the laminated body and is simply welded to the spacer, the welding may be incomplete. In particular, it is difficult to weld an aluminum foil having an insulating oxide film. From this point of view, it seems difficult to simply improve the electrical connection using a welding method.

  Further, the above-described tab portion controls conduction of current from the electrode to the outside. When this tab portion is small, excessive current concentration occurs when a large current is passed through this portion, which may cause problems such as heat generation in the tab portion and decomposition of the electrolyte accompanying this. Even when the spacer is used as described above, a substantial conduction region is not sufficiently secured. Specifically, it is conceivable that there is a portion that causes poor conduction on the circuit from the electrode to the external terminal. In this case as well, power concentration may occur on the circuit. Patent Documents 3 and 4 disclose methods for coping with such a situation, but these methods do not take into account the problems that occur when the electrodes are punched. Patent Document 5 proposes a method in which a long positive electrode, a separator, and a negative electrode are stacked and then folded to create a cell. In this case, although the problem due to the above-described punching is solved, current extraction is performed only from the uppermost and lowermost electrodes, and the problem due to power concentration is not solved. Patent Document 6 discloses a method of forming a multilayered battery by providing an electrode with an applied portion and an uncoated portion of an active material, and bending the electrode at the uncoated portion. However, in the case of this method, there is a problem that actual electrode preparation is complicated.

  The present invention has been made in view of the above situation, and an electric double layer using an electrode that suppresses the occurrence of bending, wrinkles and the like by using a metal foil original fabric in which an active material is applied to the entire surface of the metal foil. An object of the present invention is to provide a capacitor and a manufacturing method thereof. Another object of the present invention is to provide an electrochemical device having a small number of components without spacers. Furthermore, the present invention provides an electrochemical device capable of suitably performing electrical connection from a metal foil existing in a circuit from an electrode to an external terminal to a conductor plate and capable of taking out a large current. Also aimed.

  In order to solve the above-described problems, an electrochemical device according to the present invention includes a pair of electrodes each having an active material layer formed on both sides of a metal foil, and is folded several times with a sheet-like separator made of an insulating material. And a pair of conductive plates made of a conductive material arranged on both side surfaces of the multilayer body formed by arranging the folded end portions of the zigzag folds, on both side surfaces of the multilayer body The active material layer at the bent end is removed to expose the surface of the metal foil, and the pair of conductor plates are bonded to the exposed surface of the metal foil.

  In the above-described electrochemical device, the pair of conductor plates each have a through hole in a surface in contact with the laminate, and the conductor plate is a metal foil at least on the inner periphery of the through hole or the outer periphery of the conductor plate. It is good also as joining with the exposed part.

  In addition, in order to solve the above-described problem, an electrochemical device manufacturing method according to the present invention creates a pair of electrodes in which an active material layer is formed on both surfaces of a metal foil, and the pair of electrodes is made of an insulating material. A part where the stacked electrode is formed via a sheet-like separator and the laminated electrode and separator are folded in a plurality of times to form a laminated body, and the active material layer is removed at the end of the zigzag folding to expose the surface of the metal foil. And a conductive plate made of a conductive material is bonded to each of both side surfaces of the laminated body in which the portions where the metal foil is exposed are formed side by side.

  In addition, in order to solve the above-described problems, an electrochemical device manufacturing method according to the present invention creates a pair of electrodes in which an active material layer is formed on both surfaces of a metal foil, and the active material layer of each of the electrodes is disposed in a predetermined region. A portion where the surface of the metal foil is exposed is removed, and the surface of the electrode is exposed through a sheet-like separator made of an insulating material so that a surface different from the surface where the exposed portion of the metal foil is formed faces each other. The electrodes are overlapped, and the stacked electrodes and separators are folded into a plurality of spells to form a laminate in which the exposed portions of the metal foil are opposite sides, and the exposed portions of the metal foil are formed side by side. And a step of joining each of a pair of conductive plates made of a conductive material to each side surface of the laminate.

  According to the present invention, after a long positive electrode, a separator, and a negative electrode are stacked, they are folded in a zigzag manner and used as a cell of an electrochemical device. Therefore, unlike the conventional cell, the number of parts is greatly reduced, and the manufacturing cost is reduced. In addition, the number of steps can be greatly reduced because there is no need to stack components such as spacers and there is no need to sequentially stack electrodes, separators, and the like. In addition, the process itself is simplified, and the number of robots used for actual manufacturing is reduced, and the performance and the like may not be as accurate as those of the conventional apparatus. Therefore, from this point, improvement of production efficiency and reduction of manufacturing cost are expected.

  Further, according to the present invention, an electrode having an active material layer formed on the entire surface can be used, and the process is greatly simplified as compared with conventional processes such as rolling and punching. Therefore, various problems that have occurred through these steps are solved. Furthermore, unlike the configuration disclosed in Patent Document 5, in the present invention, it is possible to take out the current for each bent portion of the spelled electrode. Further, the extraction portion is formed to have a width substantially equal to the width of each electrode. Therefore, the current can be taken out at a level almost equal to that when the spacer is used. Further, in Patent Document 5, the active material layer forming region is limited to one side of the metal foil. However, according to the present invention, the active material layer can be formed on both sides of the metal foil, It is possible to greatly increase the capacity of.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the main part of the cross section of an electrochemical device according to an embodiment of the present invention, specifically, an electric double layer capacitor. The electric double layer capacitor according to the present invention includes an electrode (hereinafter referred to as a positive electrode) 3, a sheet-like separator 9 made of an insulating material, and an electrode (hereinafter referred to as a negative electrode) that functions as a positive electrode in the cell 1 that is the main part. 6) and a pair of conductor plates 11 and 12 joined to the positive electrode 3 and the negative electrode 6, respectively. The positive electrode 3 includes a conductive metal foil 4 such as aluminum, and active material layers 5a and 5b formed on both sides thereof. Similarly, the negative electrode 6 also has a metal foil 7 and active material layers 8a and 8b formed on both surfaces thereof. A separator 9 made of insulating paper or the like is disposed between the positive electrode 3 and the negative electrode 6 to prevent contact between these electrodes.

  The positive electrode 3 and the negative electrode 6 are overlapped with each other via a separator 9, and are further folded in a zigzag manner to form a laminate 10. In the laminated body, the end portions 10a of the bent portions are aligned in substantially the same plane extending in the lamination (folding) direction. In other words, the bent end portion 10 a constitutes opposite side surfaces of the stacked body 10. In the end portion 10a existing in substantially the same plane, an electrode having the same polarity is always located outside the bent portion. In the end portion 10a according to the present invention, the outermost active material layers 5a and 8b are removed, and the metal foils 4 and 7 are exposed toward the outside of the laminate 10. The conductor plates 11 and 12 are joined to these exposed portions by welding or the like. Specifically, the positive electrode conductor plate 11 is joined to the metal foil 4 (4a) exposed by partially removing the active material layer 5a in the positive electrode 3. Also, the negative electrode conductor plate 12 is bonded to the metal foil 7 (7a) exposed by partially removing the active material layer 8b in the negative electrode 4.

  Next, with respect to the method for manufacturing an electrochemical device according to the present invention, specifically, the method for manufacturing the cell 1, referring to the flow chart shown in FIG. explain. First, in Step 1, an active substance is applied to both sides of a long aluminum foil and dried to form an active substance layer. Furthermore, the obtained long electrode raw material is rolled (step 2) to bring the active material layer into a state having a desired thickness and coating film density. In step 3, the long electrode after the rolling process is cut so as to have a predetermined width and length to obtain the electrodes that become the positive electrode 3 and the negative electrode 6 shown in FIG. 1.

  In step 4, the obtained electrode is superposed in the order of positive electrode 3, separator 9, and negative electrode 6. As the separator 9 made of an insulator, a separator having an outer dimension larger by about 0.5 to 1.0 mm than the outer dimension of the electrode is used in order to prevent both electrodes from contacting and short-circuiting. After these members are overlaid, in step 5, the members are folded into a zigzag shape with a predetermined length to form the laminated body 10. The laminated body 10 obtained in step 5 is fixed and integrated with a temporary holding jig (not shown) or the like, and in step 6, an operation of removing the active substance layer present on the bent end portion 10a is performed. This removal operation is performed until the metal foil existing under the active material layer is exposed by sandblasting, laser beam irradiation, rubbing with a wire brush, or the like.

  By passing through the treatment, portions where the surface of the metal foil is exposed are arranged on opposite side surfaces of the laminate 10. Furthermore, the conductor plates 11 and 12 are joined to the laminate in which the metal foils 4 and 7 are partially exposed by the removal operation in Step 6. The conductor plates 11 and 12 are joined to the exposed surface of the metal foil by welding or the like (step 7). The cell 1 in the electric double layer capacitor is completed through the above steps.

  Note that the partial removal operation of the active material layer is not limited to after the stacked body 10 is formed, and may be performed, for example, as an operation of removing the active material layer in a predetermined region in Step 1 or Step 2. In this case, for example, when the cell 1 shown in FIG. 1 is to be manufactured, the active material layer 5 a in a predetermined region is removed from the positive electrode 3, and the active material layer 8 b in the predetermined region is removed from the negative electrode 6. Further, when laminating with the separator 9, the positive electrode 3 and the negative electrode 6 are arranged and laminated so that these removed portions exist on the front surface and the back surface of the laminated body. In addition, it is necessary to perform an operation of folding the laminate so that these removed portions are arranged on opposite side surfaces of the laminate 10. Through the above steps, the laminate 10 is obtained in which the exposed portions of the metal foil are aligned on opposite side surfaces.

  In the cell shown in FIG. 1, an electric current can be taken out from each bent portion. Therefore, a large current can be instantaneously taken out from each laminated layer, and an electrochemical device having excellent charge / discharge characteristics can be obtained.

  Here, the method of actually joining is not limited to general welding using a laser or the like, but by applying various known joining methods such as ultrasonic joining and using a conductive adhesive, the foil and It is possible to electrically and physically join the conductor plates. Therefore, the joining in the present invention means an electrical and physical joining by these various methods. In addition, although the active material layer is exemplified by the one made of activated carbon, the active material layer is not limited to this as long as it can secure desired electrical characteristics. Further, the foil and the conductor plate are preferably made of aluminum or the like as an extension of the conventional technology, but are not limited thereto as long as they are made of a material having sufficient conductivity and high weldability.

  FIGS. 3A and 3B and FIGS. 4A and 4B schematically show the appearance of the main part 1 of the electric double layer capacitor obtained by carrying out the present invention. FIG. 3A or 3B shows the thing after the process of step 7 in FIG. Also, in the following drawings, the configuration of the laminated body is basically the same, and therefore the description of the configuration of the laminated body is omitted for the following examples. A conductor plate 11 is joined by a welded portion 11c to a side surface of the multilayer body where a bent end portion (a portion where the metal foil is exposed) is aligned in the laminating direction. With such a configuration, a suitable electrical connection is made between each electrode and the conductor plate. In these drawings, the conductor plate 11 has a plate-like shape. However, as shown in FIG. 3C, the back surface is a plate-like body having an arcuate curved surface, or the cross-section of the plate is trapezoidal as shown in FIG. 3D. The thing of various shapes, such as these, can be used, and is not limited to this.

  FIG. 4A shows a configuration in which a more suitable electrode is welded using a conductor plate having a shape different from the configuration shown in FIG. 3A and the like. In this case, a hole 11a is further formed in the vertically extending portion of the conductor plate 11 so as to penetrate the surface in contact with the exposed portion of the metal foil and the opposite surface. Specifically, the exposed portion of the metal foil and the conductor plate 11 are welded at the inner peripheral portion of the hole 11a using the hole 11a. By performing such a welding operation, a wider welding area can be obtained, and the electrical connection between the metal foil and the conductor plate can be made more reliable.

  FIG. 4B shows the conductor plate 11 shown in FIG. 4A in which a protrusion 11b is further formed. The main part 1 of the electric double layer capacitor described above is housed in a sealed state inside an unillustrated exterior body, and the conductor plate 11 is connected to a terminal projecting outside from the exterior body. In the present embodiment, the protruding portion 11b can be used as it is as a terminal protruding outside from the exterior body.

  By adopting this configuration, it is possible to manufacture the main part, that is, the cell of the electric double layer capacitor having a small number of parts. In addition, a metal foil coated with an active material layer on the entire surface can be used as an electrode raw material, and various processes of coating, rolling and punching can be greatly simplified. Further, since the electrode and the conductor plate are physically and electrically firmly joined at a number of locations, a large current can be instantaneously extracted from the element.

  The present invention is described by exemplifying an electric double layer capacitor as an application target. However, the application target is not limited to this, and it is considered possible to apply to a secondary battery having a configuration similar to an electric double layer capacitor. Also, it is considered possible to apply the configuration or the manufacturing method according to the present invention to so-called electrochemical devices.

It is a figure which shows schematically the cross-sectional structure of the principal part of the electric double layer capacitor which concerns on one embodiment of this invention. It is a flowchart which shows the principal part regarding the manufacturing process of the electrical double layer capacitor which concerns on this invention. It is a figure which shows the external appearance of the principal part in the electric double layer capacitor which concerns on this invention. It is a figure which shows the external appearance of the principal part in the electric double layer capacitor which concerns on this invention. It is a figure which illustrates the shape of a conductor board. It is a figure which illustrates the shape of a conductor board. It is a figure which shows the external appearance of the principal part in the electric double layer capacitor which concerns on this invention. It is a figure which shows the external appearance of the principal part in the electric double layer capacitor which concerns on this invention.

Explanation of symbols

1: Main part of electric double layer capacitor, 3: Electrode for positive electrode, 4, 7: Metal foil, 5, 8: Active material layer, 6: Electrode for negative electrode, 9: Separator, 10: Laminate, 11: Conductor plate

Claims (4)

  A laminated body in which a pair of electrodes each having an active material layer formed on both surfaces of a metal foil is overlapped via a sheet-like separator made of an insulating material and folded in a plurality of times, and the folded ends of the zigzag are aligned. And a pair of conductive plates made of a conductive material disposed on both side surfaces of the multilayer body formed by the step, the active material layer at the bent end portions on both side surfaces of the multilayer body is removed, and the metal An electrochemical device, wherein a surface of the foil is exposed, and the pair of conductor plates are joined to the exposed surface of the metal foil.   Each of the pair of conductor plates has a through hole in a surface in contact with the laminate, and at least one of an inner peripheral portion of the through hole and an outer periphery of the conductor plate, the conductive plate is an exposed portion of the metal foil. The electrochemical device according to claim 1, wherein the electrochemical device is bonded.   A pair of electrodes in which an active material layer is formed on both surfaces of a metal foil are stacked via a sheet-like separator made of an insulating material, and the stacked electrode and separator are folded into a plurality of times to form a laminate. The active material layer is removed from the folded end portion of the zigzag fold to form a portion where the surface of the metal foil is exposed, and conductive is provided on each side surface of the laminated body where the portions where the metal foil is exposed are formed side by side. A method for producing an electrochemical device, comprising a step of joining conductor plates made of a conductive material. A pair of electrodes each having an active material layer formed on both sides of the metal foil is formed, a predetermined area of the active material layer of each of the electrodes is removed to form a portion where the surface of the metal foil is exposed, and the metal foil in the electrode The electrode is overlapped via a sheet-like separator made of an insulating material so that a surface different from the surface where the exposed portion is formed faces, and the overlapped electrode and the separator are folded in a plurality of times, A conductor made of a pair of conductive materials is formed on each side surface of the laminate in which the exposed portions of the metal foil form side surfaces facing each other, and the exposed portions of the metal foil are formed side by side. A method for producing an electrochemical device comprising the step of joining each of the plates.

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