JP2005340689A - Electrochemical device, its manufacturing method, and electrode used for the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical device having a constitution wherein metal foil in which an active material layer is formed on the whole surface can be used as a rolled material, and to provide its manufacturing method. <P>SOLUTION: As a method for manufacturing the electrochemical device, the end of an electrode bit is turned up first, the active material layer on the turned-up portion is removed, and a state that metal foil is exposed is obtained. The lamination of the electrode bit of this state is performed by a separator, and an exposed part of the metal foil and a conductor plate are joined. By these processes, a principal part in the electrochemical device is constituted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to electrochemical devices such as lithium ion secondary batteries and electric double layer capacitors, and methods for producing the same, and electrodes used in these devices. More specifically, the present invention relates to an electrochemical device characterized by a laminated structure of electrode portions, an electrochemical device manufacturing method characterized by the lamination method, and an electrode used in the electrochemical device.

  Secondary batteries are often used as power sources mounted on IT devices such as mobile phones and laptop computers, and electric double layer capacitors are being used for applications such as backup power sources. These IT devices are being reduced in size and added with various functions, and the power source used is also required to be reduced in size, thickness, and weight. As a form of a battery or a capacitor corresponding to the request, an electrode stack type battery can be given. The electrode-stacked battery can be easily reduced in thickness as compared with a so-called wound battery, and a metal can is unnecessary, so that the cost and weight can be easily reduced.

  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 this is incorporated into 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 2001-157835 A Japanese Patent Laid-Open No. 10-214616 Japanese Patent Application Laid-Open No. 07-094374 Japanese Patent Laid-Open No. 11-274004

  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.

  In the above-described laminate, conductive shims, which are also called electrodes, separators, and spacers, 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. In addition, since the tab portion is not so strong, it is not easy to suitably place the spacer on the tab portion, and from this point of view, it is difficult to improve the production efficiency of the laminate. It is.

  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 such a configuration using an aluminum foil, it is considered that 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 surface film. From this point of view, it seems difficult to simply improve the electrical connection using a welding method.

  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. Another object of the present invention is to provide an electrochemical device that can suitably perform electrical connection from a metal foil to a conductor plate and can extract a large current.

  In order to solve the above problems, an electrochemical device according to the present invention includes a laminate in which an electrode made of a metal foil having an active material layer formed on at least one surface and a non-conductive separator are laminated, An electrochemical device having a conductive plate electrically connected to a metal foil, wherein the electrode has a part that is partially folded, and the active material layer is not present at the folded end and the metal foil is exposed. And an electrical connection between the conductor plate and the metal foil is made through an exposed region of the metal foil.

  In the above-described electrochemical device, the electrodes are alternately stacked such that the electrode having one polarity and the electrode having the opposite polarity are alternately arranged via the separator, and the folded portions are alternately positioned. The folded portions of the electrodes having the same polarity are stacked so as to overlap, and the portions other than the folded portions of the electrodes having one polarity are other than the folded portions of the electrodes having the opposite polarity via the separator. It is laminated so as to overlap the part. In the electrochemical device described above, the electrode has a substantially rectangular shape, and the conductor plate is disposed at the folded end and joined to the electrode. Alternatively, the electrode has a substantially L shape, and has a portion that is folded back at a part of the L-shaped protruding portion, and the conductor plate is disposed at the folded end of the folded portion and joined to the electrode.

  In addition, in order to solve the above-described problem, an electrochemical device manufacturing method according to the present invention obtains an electrode having a predetermined shape from an electrode raw material made of a metal foil having an active material layer formed on at least one surface. A step of folding a predetermined portion of the electrode, a step of forming a metal foil exposed region where the active material layer is removed at the folded end of the electrode, and a plurality of electrodes electrically connected to the metal foil exposed region And a step of electrically connecting the conductor plate.

  In the above-described method for manufacturing an electrochemical device, the electrodes are alternately arranged so that the electrode having one polarity and the electrode having the opposite polarity are alternately arranged via the separators, and the folded portions are at alternate positions. It is a step of alternately laminating, and at the time of the lamination, the folded portions of the electrodes having the same polarity are overlapped, and the portions other than the folded portion of one electrode are opposed to each other through the separator. It further has the process of laminating | stacking on parts other than the folded part. Further, in the above-described electrochemical device manufacturing method, the folding step is performed on the metal foil original fabric, and the step of obtaining an electrode having a predetermined shape is performed on the partially folded metal foil raw fabric. The Further, in the method for manufacturing an electrochemical device described above, there is a step of alternately stacking a plurality of electrodes and non-conductive separators after the folding step to form a laminate, and then forming a metal foil exposed region. This is performed on the laminate.

  Alternatively, in order to solve the above problems, an electrode according to the present invention is an electrode constituting a stacked electrochemical device, and has a metal foil and an active substance layer formed on at least one surface, One end thereof is folded over a predetermined range. The electrode further has a metal foil exposed region where no active material layer is present at the folded end of the electrode.

  According to the present invention, it is possible to use, as an electrode, a metal foil in which an active substance (coating containing activated carbon) is applied on substantially the entire surface of one side or both sides. Accordingly, the coating, rolling, and punching steps can be greatly simplified, and the manufacturing cost can be reduced. Also, with respect to the apparatus that performs each of these steps, unlike the above-described conventional technique, it is possible to construct a production line without requiring much operational accuracy of each apparatus, and in this respect also reduction of manufacturing cost is expected. It is.

  Here, in the case of an electric double layer capacitor used for an auxiliary power supply for a hybrid vehicle, for example, where a large current flows, if the tab portion is small, power concentration occurs in this portion, heat is generated, and the electrolytic solution is decomposed in this portion. May occur. Patent Document 3 discloses a configuration that avoids such power concentration by using an electrode having a tab having the same width as the active material application region. In Patent Document 4, a spacer made of a conductive material is sandwiched between such tabs, and the tabs are directly welded to cope with a large current, and even when the number of stacked layers is increased, the tabs are welded together. A configuration that facilitates connection and further lamination of electrodes is disclosed.

  According to the present invention, an energization region having the same width as the active material application region is formed without providing a non-application region, and a large current is instantaneously passed (taken out) by connecting a conductive plate to this portion. It becomes possible to cope with a large current as in Patent Document 3 or 4. Furthermore, by using the bent portion of the metal foil as a spacer in Patent Document 4, even when the number of electrode stacks is increased, it is possible to easily and reliably connect the current-carrying region to the conductive plate, The stacking operation can be facilitated. Therefore, unlike the configuration disclosed in Patent Document 4, the number of parts as an electric double layer capacitor does not increase. In addition, an electric double layer capacitor can be obtained without going through a complicated process of sandwiching the spacer between the tabs. Further, for example, an electrode foil original fabric on which a long active material layer has been formed may be formed into a region that is folded back to a predetermined width in the length direction, and then an electrode having a predetermined dimension may be punched from the original fabric. In this case, it is possible to manage the thickness of the folded portion constant by rolling the folded portion with a predetermined thickness, and it is possible to manage the stacking thickness with a precision equal to or higher than when the spacer is sandwiched. .

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a main part of a cross section of an electric double layer capacitor according to an embodiment of the present invention. An electric double layer capacitor 1 according to the present invention includes a conductive metal foil 3 such as aluminum having activated carbon layers 5 and 7 formed on both surfaces thereof, an insulating paper disposed between electrodes described later, and the like. And a conductor plate 11 connected to the metal foil 3 as main components. The metal foil 3 forms the electrode 13 together with the activated carbon layers 5 and 7. One end of the electrode 13 is folded back by a predetermined length to form a double portion 13a.

  The activated carbon layer 7 is removed from the folded end portion outer side 13 b, and the metal foil 3 is exposed and is in contact with the conductor plate 11. Therefore, the electrical connection between the electrode 13 and the conductor plate 11 is performed by joining the exposed portion of the metal foil to the conductor plate 11 by welding or the like. The conductor plate 11 is further connected to an external terminal (not shown) directly or via another conductive member. In the present embodiment, the electrode 13 has a substantially square shape, and the folding is performed around a straight line that is substantially parallel to the opposite sides of the square and that is separated from the side by a predetermined distance. The conductor plate 11 is disposed corresponding to the opposing sides. At the time of lamination, the electrode 13 thereon is arranged and laminated while avoiding the double portion 13a. Usually, in the laminated body, the positive electrode and the negative electrode are alternately stacked via separators, but only the same polarity of the double portion 13a is stacked.

  More specifically, the length of the electrode 13 in the bent state is connected to the conductor plate 11 with a predetermined distance from the distance between the opposing conductor plates 11. Since the overlapping portion of the double portion 13a is accommodated in the space spaced by a predetermined interval, the thickness of the double portion 13a at the time of stacking can be effectively eliminated. As a result, the electrode 13 and the separator 9 can be laminated so as to be substantially flat up to the contact point with the conductor plate 11, and the contact point between the metal foil 3 and the conductor plate 11 can be stably fixed.

  Next, an embodiment of the method for producing an electrochemical device according to the present invention will be described with reference to the flowchart shown in FIG. 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. In step 2, the long electrode original fabric obtained in step 1 is rolled to bring the active material layer into a state having a desired thickness and coating film density. Further, in Step 3, the electrode raw material is punched into electrode pieces having a predetermined size by using a press machine to obtain an electrode 13 shown in FIG.

  The obtained electrode 13 has its end folded back at a predetermined length in step 4 to form a double portion 13a. The electrodes after the formation of the double portion 13a are laminated together with the separator 9 in the arrangement shown in FIG. 1 (step 5). The laminated body obtained in step 5 is fixed and integrated with a temporary holding jig or the like (not shown), and in step 6, the active substance is removed from both side surfaces corresponding to the electrode end portion outer side 13b. This removal operation is performed by sandblasting, laser beam irradiation, scraping with a wire brush, or the like. Further, in step 6, the main part as the electric double layer capacitor is obtained by fixing and attaching the conductor plate 11 to the exposed surface of the metal foil in the laminated body by welding or the like to the laminated body from which the metal foil 3 is exposed by the removing operation. Complete.

  In addition, although the case where a conductor plate is arrange | positioned at the side surfaces which oppose here was illustrated here, the structure of the electric double layer capacitor concerning this invention is not limited to the said arrangement | positioning. As a specific modification, FIG. 3 shows a configuration in which conductor plates on the positive electrode side and the negative electrode side are arranged on one side surface. In this configuration, the electrode shape is different from the electrode shape shown in FIG. Specifically, a region 13c protruding from one side of the electrode 13 is provided, and the shape of the electrode 13 is L-shaped. An end portion of the protruding region 13c is folded to form a double portion 13a. In this case, the folding is performed around a straight line that is parallel to the side forming the top of the L-shape and that is separated from the side by a predetermined distance.

  For example, when the protruding region 13c of the electrode serving as the positive electrode is formed on the right side of a predetermined side, the protruding region 13 on the negative electrode side is formed on the left side. Therefore, the conductor plate 11 is disposed corresponding to this protruding portion. By setting it as the said structure, the double part 13a will be piled up every other layer, and the planarization as a laminated body is achieved. In this case, the conductor plate 11 is connected and fixed to the two rows of protruding portions formed on one side surface of the multilayer body. The manufacturing process of the main part of the electric double layer capacitor having the structure is the same as that for manufacturing the structure shown in FIG. 1 except that the shape of the punched electrode is different. Detailed description here is omitted.

In addition, the manufacturing method concerning this invention illustrated the process of performing the exposure operation | work of metal foil, after laminating | stacking an electrode and a separator and fixing a conductor board after that. However, the embodiment of the present invention is not limited to this. For example, as will be described later, a U-shaped conductor plate that can sandwich the laminate and having a slit on its side surface is used, and the laminate may be sandwiched between two surfaces facing each other vertically. good.
You may weld a metal foil and a conductor board in this slit.

  Further, the order of the steps 3 and 4 described above may be changed, and a predetermined end of the long electrode raw material may be folded back and then punched into a small electrode piece. In this case, a step of rolling the folded portion in the state of the long original fabric may be added following the original fabric folding. By rolling the folded portion to a predetermined thickness, the thickness of the folded portion can be managed to be constant, and the stacking thickness can be managed with the same accuracy as when the spacer is sandwiched. Further, the order of the steps 5 and 6 described above may be changed, and the active material layer at a predetermined position may be removed before stacking.

  FIGS. 4A and 4B and FIGS. 5A to 5C schematically show the appearance of the main part 1 of the electric double layer capacitor obtained by the implementation of the present invention. FIG. 4A or 4B 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 portion of the side surface of the multilayer body where the outer end portion 13b of the folded portion (the portion where the metal foil is exposed) is aligned in the stacking 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. 4C, 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. 4D. The thing of various shapes, such as these, can be used, and is not limited to this. In order to make the integration of the laminate and the conductor plate 11 more reliable, as shown in FIG. 5A, sandwich the laminate between the upper and lower surfaces of the conductor plate having a U-shaped longitudinal section, and It is good also as integrating by the rivet 15 and performing processing, such as welding with a conductor plate and metal foil. FIG. 5A shows a case where riveting is applied to the conductor plate. Specifically, through holes are formed in the upper and lower surfaces of the U-shaped conductor plate 11, and through holes are also formed in corresponding portions on the double portion 13 a and the separator 9. After the conductor plate 11 is fixed to the laminated body, the rivets 15 are inserted into the through holes and the both ends thereof are caulked to further strengthen the connection between the laminated body and the conductive plate. The conductor plate 11 has a width smaller than the length of the folded portion, and welding to the metal foil is performed at both side portions thereof. The welded portion is shown in the figure as a weld mark 11c.

  FIG. 5B 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. 5A. In this case, the conductor plate 11 is formed with a slit 11a extending in the vertical direction in a U-shaped vertical surface portion. By welding the metal foil 3 exposed to this portion and the conductor plate 11 in the slit 11a, a wider welding area can be obtained, and these electrical connections can be made more reliable. It becomes possible.

  FIG. 5C shows the conductor plate 11 shown in FIG. 5B 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 with a small number of parts by using the folded portion of the electrode instead of the spacer in Patent Document 4. 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 suitably joined, 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 modification of embodiment shown in FIG. 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. 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: Metal foil 5, 7: Active material layer 9: Separator 11: Conductor plate 13: Electrode 15: Rivet

Claims (10)

An electrochemical system comprising a laminate comprising an electrode made of a metal foil having an active material layer formed on at least one surface and a non-conductive separator, and a conductor plate electrically connected to the metal foil. There is a device,
The electrode has a part that is partially folded, and the folded end has an area where the active material layer is not present and the metal foil is exposed, and the electrical connection between the conductor plate and the metal foil Is made through the exposed region of the metal foil. The electrodes are alternately stacked so that electrodes having one polarity and electrodes having opposite polarities are alternately arranged via the separator, and the folded portions are in alternate positions,
The folded portions of the electrodes having the same polarity are stacked so as to overlap each other, and the portions other than the folded portions of the one electrode having the same polarity are folded on the electrodes having the opposite polarity via the separator. The electrochemical device according to claim 1, wherein the electrochemical device is laminated so as to overlap a portion other than the portion.   The electrochemical device according to claim 1, wherein the electrode has a substantially square shape, and the conductor plate is disposed at the folded end and joined to the electrode.   The electrode has a substantially L shape, and has the folded portion at a part of the L-shaped projecting portion, and the conductor plate is disposed at the folded end in the folded portion. The electrochemical device according to claim 1, wherein the electrochemical device is joined to the electrochemical device. Obtaining an electrode having a predetermined shape from an electrode raw material made of a metal foil having an active material layer formed on at least one surface;
Folding back a predetermined portion of the electrode;
Forming a metal foil exposed region where the active material layer is removed at the folded end of the electrode;
A method for producing an electrochemical device, comprising the step of electrically connecting the exposed region of the metal foil and a conductive plate for electrically connecting the plurality of electrodes. The step of laminating the electrodes alternately so that the electrodes of one polarity and the electrodes of the opposite polarity are alternately arranged via separators, and the folded portions are in alternate positions,
At the time of the lamination, the folded portions of the electrodes having the same polarity are overlapped, and the folded portions of the electrodes of the opposite polarity other than the folded portions of the one electrode via the separator The method for producing an electrochemical device according to claim 5, further comprising a step of stacking the other portions.   The said folding process is performed with respect to the said metal foil original fabric, and the process of obtaining the electrode which has the said predetermined shape is made | formed with respect to the metal foil original fabric partially folded back. The manufacturing method of the electrochemical device in any one.   The step of forming a laminate by alternately laminating the plurality of electrodes and non-conductive separators after the folding step is performed on the laminate after that. The method for producing an electrochemical device according to any one of claims 5 and 6. An electrode constituting a stacked electrochemical device,
Metal foil,
An active material layer formed on at least one surface of the metal foil,
One end of the electrode is folded over a predetermined range. The electrode according to claim 9, further comprising a metal foil exposed region where the active material layer is not present at a folded end portion of the electrode.

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