JP2018037338A - Power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage element which is extremely thin and which is unlikely to be deformed or wrinkled in an exterior body. SOLUTION: The electricity storage device 101 comprises an exterior body 111 in which an electrode body 10 in which a sheet-shaped positive electrode 20 and a negative electrode 30 are vertically stacked via a separator 40 is housed together with an electrolytic solution. The body is composed of two flexible printed wiring boards (111a, 111b), and the flexible printed wiring board has convex pieces (113a, 113b) protruding in strips from the flat area (112a, 112b) including the electrode body. A conductor layer (311a, 311b) having an integrally formed planar shape is formed on a surface which is an inner surface of the outer package, and the conductor layer includes a collector portion (which includes planar regions of the positive electrode and the negative electrode). 121, 131) and lead portions (123, 133) extending from the current collecting portion along the convex piece in a strip shape, and the outer peripheral body 12 surrounding the current collecting portion is made of an insulating resin 150. It is sealed by being welded by. [Selection diagram]

Description

  The present invention relates to a power storage element.

  In recent years, extremely thin electronic devices such as electronic paper, IC tags, IC cards, and electronic keys have been put into practical use. For power sources of these electronic devices, laminate type storage elements (primary batteries, secondary batteries, electric double layer capacitors, etc.) suitable for thinning are used. FIG. 1 shows a schematic structure of the laminate-type energy storage device 1. Here, the structure of the laminate type energy storage device 1 operating as a lithium primary battery is shown. FIG. 1A is an external view of a laminate-type power storage element 1, and FIG. 1B is an exploded perspective view showing the internal structure of the power storage element 1. In FIG. 1B, some members are hatched so that they can be easily distinguished from other members. As shown in FIG. 1A, the laminate-type energy storage device 1 has a flat plate-like appearance. In this example, the positive electrode terminal plate 23 extends outward from one side 13 of the outer package 11 having a rectangular planar shape. The negative terminal plate 33 is led out.

  In the exterior body 11, the electrode body 10 formed by pressure bonding in a state where the sheet-like positive electrode 20 and the sheet-like negative electrode 30 are laminated via the separator 40 as shown in FIG. It is enclosed. The positive electrode 20 is obtained by applying and drying a slurry-like positive electrode material 22 containing a positive electrode active material such as manganese dioxide on one main surface of a positive electrode current collector 21 made of a metal foil or the like. It is applied to the surface of the current collector 21 that faces the separator 40. The negative electrode 30 has a structure in which a negative electrode lithium 32 made of flat metal lithium or a lithium alloy is pressure-bonded to the surface of the negative electrode current collector 31 made of metal foil or the like on the separator 40 side.

  The exterior body 11 is formed by welding the peripheral regions 12 of two laminated laminate films (11a, 11b) that are stacked on each other by a thermocompression bonding method and sealing the inside. As is well known, the laminate films (11a, 11b) have a structure in which one or more resin layers are laminated on the front and back of a metal foil (aluminum foil, etc.) serving as a base material. 11 has a structure in which a protective layer made of, for example, a polyamide resin is laminated on the front surface, which is an outer surface, and an adhesive layer, such as polypropylene, is laminated on the back surface, which is an inner surface of the outer package 11. doing.

  As a procedure for housing the electrode body 10 in the exterior body 11, for example, the electrode body 10 is disposed inside two facing laminate films (11a, 11b), and the rectangular laminate films (11a, 11b) are arranged. 3) of the peripheral region 12) is welded to open the remaining one side. Thereby, the bag-shaped exterior body 11 is formed. At this time, the terminal plates (23, 33) of the positive and negative electrodes (20, 30) are projected outward from one side 13 of the exterior body 11. Next, an electrolytic solution is injected into the bag-shaped exterior body 11 from the opening, and one side opened in the peripheral region 12 is welded, thereby completing the laminate type energy storage device 1 shown in FIG.

  In addition, at the edge 13 where the electrode terminal plates (23, 33) are led out in the outer package 11, the electrode terminal plates (23, 33) and the laminate film ( 11a, 11b) may not be able to secure sufficient adhesive strength. Therefore, in the general laminate-type energy storage device 1, the edge 13 from which the electrode terminals (23, 33) are led out in the outer package 11 is securely sealed. It has a structure for stopping. In the illustrated power storage element 1, as shown in FIG. 1B, the edge 13 from which the electrode terminals (23, 33) are led out is reliably sealed by using a known tab lead 50. As described in Patent Document 1 below, the tab lead 50 is insulated on the way of extension of the strip-shaped terminal lead 51 made of a metal plate or a metal foil which is a substantial electrode terminal plate (23, 33). A resin sealing material (hereinafter referred to as tab film 52) has a structure in which the terminal leads 51 are sandwiched. One end 53 of the terminal lead 51 is exposed to the outside of the outer package 11, and the other end is connected to a part of the positive electrode current collector 21 and the negative electrode current collector 31 by a method such as ultrasonic welding. Yes.

  The tab film 52 has a structure in which a resin film such as polypropylene is laminated as an adhesive layer on both front and back surfaces of an insulating base film made of polyimide or the like. When the peripheral regions 12 of the laminate films (11a, 11b) facing each other are thermocompression bonded to form a flat bag-shaped outer package 11, the electrode terminal plates (23, 33) are formed in the peripheral region 12 of the outer package 11. The tab film 52 of the tab lead 50 is thermally welded together with the laminate films (11a, 11b) at the edge 13 on the side from which the protrusions protrude. As a result, the tab film 52 is welded to the adhesive layer of the laminate film (11a, 11b), and the lead-out portion of the terminal lead 51 is firmly sealed.

  Note that the structure of the laminate-type power storage element is also described in, for example, Patent Document 2 below. Non-Patent Document 1 below describes a thin lithium primary battery that is a laminate-type storage element that is actually provided as a product.

JP 2014-86139 A JP 2006-281613 A

FDK Corporation, “Thin Lithium Primary Battery”, [online], [Search July 28, 2016], Internet <URL: http://www.fdk.co.jp/battery/lithium/lithium_thin.html>

  The laminate type power storage element has a structure suitable for thinning, and can be said to be the only power storage element that can be used as a power source for an IC card at present. However, thin electronic devices such as IC cards may contain more electronic circuits within a predetermined size due to future high functionality, and as a result, the power storage space in the electronic device further increases. May be smaller. Of course, there is always a demand for thinning electronic devices as well as IC cards. Therefore, further reduction in thickness is required for the current laminate type storage element. However, the thin lithium primary battery described in Non-Patent Document 1 currently used as a power source for IC cards is extremely thin with a thickness of 0.45 mm to 0.55 mm, and this thickness is already the limit of thinning. It can be said that it is close to. That is, there is a possibility that the laminated power storage device cannot sufficiently meet the demand for further thinning.

  In addition, a laminate type power storage element uses a laminate film that is soft and easily deformed for an exterior body. Therefore, when the internal pressure in the exterior body rises due to generation of heat or gas due to a power generation reaction, the exterior body may swell. If an exterior body of a laminate-type energy storage device incorporated in a thin electronic device such as an IC card swells, the electronic device may be deformed. In addition, the laminated storage element has a thicker electrode housing area and electrode terminal plate lead-out area than the other areas, and the thickness is not uniform over the entire planar area. A level difference is caused. And the level | step difference produces a wrinkle on the surface of an exterior body. If wrinkles occur on the surface of the exterior body, the distance between the two laminate films facing each other is partially different. If wrinkles occur in the peripheral area, the sealing strength is naturally reduced.

  Therefore, an object of the present invention is to provide a power storage element that is extremely thin and hardly deforms or wrinkles in an exterior body.

The present invention for achieving the above object is an electricity storage element in which an electrode body in which a sheet-like positive electrode and a negative electrode are stacked in a vertical direction via a separator is housed together with an electrolytic solution in an exterior body,
The exterior body is composed of two flexible printed wiring boards,
The flexible printed wiring board has a planar shape in which convex pieces projecting in a strip shape from a planar region including the electrode body are integrally formed, and a conductor layer is formed on a surface which is an inner surface of the exterior body. ,
The conductor layer is composed of a current collecting part including a planar region of the positive electrode and the negative electrode and a lead part extending in a band shape from the current collecting part along the convex piece,
The outer package is sealed by a peripheral region surrounding the current collector being welded by an insulating resin.
It is set as the electrical storage element characterized by this.

  Preferably, the flexible printed wiring board is such that the conductor layer is formed on a substrate made of a polyimide film. Further, the insulating resin for sealing the exterior body is a seal film in which a frame-shaped polyimide film surrounding the current collector is used as a base, and a heat-meltable adhesive layer is formed on both front and back surfaces of the base. If there is, it is more suitable. And if it is set as the electrical storage element by which the said sheet-like positive electrode and said negative electrode are each accommodated in the said exterior body, the effect of thickness reduction can be made great.

  According to the present invention, a power storage element that is extremely thin and hardly deforms or wrinkles in an exterior body is provided. Other effects will be clarified in the following description.

It is a figure which shows the structure of a general lamination type electrical storage element. It is the external view and exploded perspective view of the electrical storage element which concerns on the Example of this invention. It is sectional drawing which shows the structure of the electrical storage element which concerns on the said Example.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the drawings used for the following description, the same or similar parts may be denoted by the same reference numerals and redundant description may be omitted. In some drawings, reference numerals may be assigned to parts that are not required in other drawings if unnecessary.

=== Example ===
<Structure of power storage element>
A lithium primary battery is mentioned as an electrical storage element according to an embodiment of the present invention. 2 and 3 show a power storage device 101 according to an embodiment of the present invention. FIG. 2A is a perspective view illustrating an external appearance of the power storage element 101, and FIG. 2B is an exploded perspective view illustrating an internal structure of the power storage element 101. FIG. 3 is a cross-sectional view taken along the line aa in FIG. As shown in FIG. 2A, in the power storage element 101 illustrated, the exterior body 111 has a rectangular flat plate shape, and two strip-shaped convex pieces (113a, 113a, 113b) protrudes. Further, the two convex pieces (113a, 113b) protrude from different positions on one side 13 of the exterior body 111. And the area | region of the predetermined width w which goes around the outer edge of the rectangular flat plane area | region 112 becomes the peripheral area | region 12 for sealing the exterior body 111. FIG.

  As shown in FIGS. 2B and 3, the power storage element 101 is configured so that the sheet-like positive electrode 20 and the negative electrode 30 face each other with a separator 40 in the same manner as the laminate-type power storage element 1 shown in FIG. An electrode body 10 is provided. However, in the electricity storage device 101 of the present embodiment, the structure of the exterior body 111 is significantly different from that of the laminate-type electricity storage device, and the peripheral regions 12 of the flexible printed circuit boards (hereinafter also referred to as FPC (111a, 111b)) It has the structure which welded. The FPC (111a, 111b) is obtained by forming a conductor layer (311a, 311b) formed by bonding a copper foil or the like on the surface of a base (211a, 211b) made of an insulating film. An electric circuit is formed by the conductor layers (311a, 311b). In this embodiment, a polyimide film is used as a base (211a, 211b), and conductor layers (311a, 311b) are bonded to the inner surface of the exterior body 111 (hereinafter also referred to as a back surface). The base body (211a, 211b) is a planar shape formed by integrally projecting strip-shaped convex pieces (113a, 113b) from one side 13 of a rectangular flat region (hereinafter also referred to as a rectangular region (112a, 112b)). have. The conductor layers (311a, 311b) are rectangular regions (121, 131) similar to the rectangular regions (112a, 112b) inside the rectangular regions (112a, 112b) of the base bodies (211a, 211b) and It has a planar shape in which convex portions (hereinafter also referred to as lead portions (123, 133)) extending in a strip shape from one side 113 of the rectangular regions (121, 131) along the convex pieces (113a, 113b) are connected. doing. In addition, when the two FPCs (111a, 111b) face each other, the protruding pieces (113a, 113b) of the base (211a, 211b) are arranged so that the lead parts (123-133) do not overlap in the facing direction. The protruding side 13 is formed at a different position. The rectangular regions (121, 131) in the conductor layers (311a, 311b) are regions functioning as current collectors (hereinafter also referred to as current collectors (121, 131)), and lead portions (123, 133). The portion of the base (211a, 211b) that protrudes outward from the rectangular area (112a, 112b) corresponds to the electrode terminal plate.

  Further, in the FPC (111a, 111b), the rectangular frame-shaped region surrounding the current collectors (121, 131) is the peripheral region 12, and in this embodiment, the rectangular frame-shaped sealing film 150 is provided in the peripheral region 12. The exterior body 111 is sealed by welding. The sealing film 150 is a single-layer film made of a resin having heat-welding properties such as polypropylene, and a resin layer such as polypropylene is formed as an adhesive layer on both the front and back sides of a base film made of polyimide or the like, similar to the above-described tab film. 3 layers of film. The electrode body 10 is disposed inside the rectangular frame-shaped seal film 150.

  As described above, the power storage device 101 according to this example uses the FPC (111a, 111b) for the exterior body 111, and the FPC (111a, 111b) is a current collector that functions as a current collector for the positive electrode and the negative electrode ( 121 and 131) and a conductor layer (311a, 311b) in which lead portions (123, 133) functioning as electrode terminal plates are integrated with each other (base 211a, 211b). That is, the exterior body 111 serves as both a current collector and an electrode terminal plate. Therefore, a separate member serving as a current collector is not necessary, and can be made thinner than a laminate type power storage element. In this example, the thickness of 0.08 mm was further reduced with respect to the 0.45 mm-thick laminate type storage element described in Patent Document 1.

  The exterior body 111 made of FPC (111a, 111b) with a resin film as a base is unlikely to bend even when the electrode body 10 is housed inside, unlike the exterior body made of a laminate film. By adjusting the thickness of the seal film 150, the thickness of the rectangular region 112 of the exterior body 111 can be made extremely uniform. Of course, the surface of the exterior body 111 is not wrinkled.

  By the way, the power storage element is incorporated in an electronic device in a state of being mounted on a substrate of an electronic circuit. Many electronic components on an electronic circuit are mounted by reflow soldering. However, in a conventional laminate film, the resin layer on the back surface of the exterior body in the laminate film may be melted by heat during reflow. If the resin layer is melted, the metal foil as the substrate is exposed and an internal short circuit occurs. Therefore, in an electronic device using a laminate-type power storage element as a power source, a process for mounting the power storage element on an electronic circuit separately from the electronic component is required, and it is difficult to reduce the manufacturing cost of the electronic device. However, in the electricity storage element 101 of this embodiment, a polyimide film is used for the bases (211a, 211b) of the FPC (111a, 111b). As is well known, polyimide has a thermal decomposition temperature of about 500 ° C. and has extremely high heat resistance. Therefore, it is possible to mount the power storage element 101 in an electronic circuit by reflow soldering, which is difficult with a laminated power storage element, and it can be expected to reduce the manufacturing cost of an electronic device using the power storage element 101 of this embodiment as a power source.

  Further, in the electricity storage device 101 of the present embodiment, in the peripheral region 12 for sealing, the bases (211a, 211b) of the FPC (111a, 111b) made of an insulating resin except for the region where the lead portions (123, 133) are formed. ) Is exposed. That is, unlike the laminate film, the substrate (211a, 211b) is not conductive. The lead portions (123, 133) extend along the convex pieces (113a, 113b) of the base bodies (211a, 211b) from different positions so as not to face each other. Therefore, when the peripheral region 12 is thermocompression bonded to seal the exterior body 111, a short circuit between the positive electrode side and the negative electrode side conductor layers (311a, 311b) does not occur in principle. In this embodiment, polyimide having excellent heat resistance is used for the bases (211a, 211b) of the FPC (111a, 111b). Therefore, the peripheral region 12 can be thermocompression bonded with sufficient temperature and pressure, and the sealing strength can be improved. In other words, the power storage device 101 of the present embodiment can obtain a sufficient sealing strength even when the width of the peripheral region 12 is narrowed, the area of the exterior body 111 can be reduced, and the size and size can be reduced. Can also be achieved. Also for the seal film 150, if a three-layer seal film 150 using a polyimide having excellent heat resistance as a base film is used, the sealing strength can be further improved. The FPC (111a, 111b) using a resin film as a base (211a, 211b) has a lower thermal conductivity than a laminate film using a metal foil as a base. Therefore, even if the exterior body 111 is sealed by thermocompression bonding at a higher temperature, the possibility of damaging the electrode body 10 is low.

<Manufacturing procedure>
Next, the manufacturing procedure of the power storage element 101 of this embodiment will be described with reference to FIG. 2B. The FPC (111a, 111), in which the current collectors (121, 131) and the lead parts (123, 133) described above are formed. 111b), a slurry-like positive electrode material 22 is applied to the surface of the current collecting part 121 on the positive electrode 20 side, and a negative electrode made of rectangular flat metal lithium or lithium alloy on the surface of the current collecting part 131 on the negative electrode 30 side Lithium 32 is disposed. Then, the positive electrode material 22, the separator 40, and the negative electrode lithium 32 are arranged inside the rectangular frame-shaped sealing film 150 while the positive electrode material 22 and the negative electrode lithium 32 face each other through the rectangular separator 40. Further, the two FPCs (111a, 111b) are made to face each other while filling the inside of the seal film 150 with the electrolytic solution. Then, the peripheral region 12 of the FPC (111a, 111b) is thermocompression bonded, and the adhesive layer of the seal film 150 is welded to the back surface of the two FPCs (111a, 111b). Thus, the power storage element 101 illustrated in FIG. 2A is completed. As a procedure for sealing the exterior body 111, a bag-shaped exterior body 111 is first manufactured by welding two FPCs (111 a and 111 b) in a state where a part of the peripheral region 12 is opened, and then opening the exterior body 111. After injecting the electrolytic solution from the part, the outer part 111 may be sealed by thermocompression of the open part.

=== Other Embodiments ===
In the above embodiment, FPC using a polyimide film as a base is used for the exterior body in consideration of mounting by reflow soldering. However, the base film is made of other resin such as glass epoxy resin or PET resin. Also good. Moreover, in the said Example, although the exterior body was sealed using the sealing film, it is good also as sealing an exterior body by apply | coating an adhesive agent to a peripheral area | region. As the adhesive, for example, an epoxy resin can be considered.

  In the above embodiment, the protruding pieces of the FPC protrude in the same direction from different positions on one side of the base so that the protruding pieces of the FPC do not face each other, but the protruding pieces may protrude in different directions such as the opposite direction. Or if the area | region where lead parts face in an exterior body is reliably insulated by sealing members, such as a sealing film, a convex piece (113a, 113b) protrudes from the same position, and is a lead | read | reed of the positive electrode 20 and the negative electrode 30 The parts (123, 133) may be facing each other. When the storage element 101 is incorporated into an electronic device, the lead portions (123-133) of the positive electrode 20 and the negative electrode 30 are short-circuited by bending the convex pieces (113a, 113b) in opposite directions to the facing direction. Do not do that.

  The electricity storage device according to the present invention is not limited to a lithium primary battery, and various types of electricity storage devices (lithium secondary batteries, electric double layer capacitors) as long as a flat electrode body is sealed in an exterior body made of FPC. Etc.). Of course, since the planar shape of the base body that forms the outer shape of the exterior body and the conductor layer that becomes the current collector and electrode terminal can be freely changed, the planar shape of the electrode body and the shape of the peripheral region of the exterior body are rectangular. However, the present invention is not limited to this, and other shapes such as a circle can be used.

  The power storage device according to the above example was a single-layer power storage device in which one sheet-like positive electrode and one negative electrode were housed in the outer package, but the present invention is a pair of positive electrodes facing each other via a separator. And a negative electrode as an electrode body for one layer, it can also be applied to a “multi-layer” power storage element including electrode bodies for a plurality of layers. Certainly, the conventional single-layer power storage element has a basic structure for achieving thinning by including only the electrode body having the smallest number of layers. In the power storage element according to the embodiment, the single-layer power storage element The synergistic effect of the structure of the power storage element and the exterior body made of FPC can greatly enhance the thinning effect. Of course, the outermost layer current collector is not required even in the case of a multilayer type storage element, and the storage element of the present invention can be reliably compared with the multilayer type storage element even if it is a multilayer type. Thinning can be achieved. Of course, there is no deformation of the exterior body or wrinkles on the surface of the exterior body as the internal pressure increases. In addition, since the FPC that serves as a current collector and an electrode terminal plate is used as the exterior body, the number of components can be surely reduced, and the storage element can be expected to be provided at a lower cost.

1,101 Laminate type storage element, 10 electrode body, 11, 111 exterior body,
11a, 11b laminate film, 12 peripheral region, 20 positive electrode,
21 positive electrode current collector, 22 positive electrode material, 23 positive electrode terminal plate,
32 negative electrode material (negative electrode lithium), 32 negative electrode terminal plate, 40 separator,
111a, 111b FPC, 112 rectangular region of the exterior body,
112a, 112b FPC (base) rectangular area, 113a, 113b convex piece,
121, 131 current collector, 123, 133 lead,
211a, 211b FPC substrate, 311a, 311b FPC conductor layer

Claims (4)

An electricity storage element in which an electrode body in which a sheet-like positive electrode and a negative electrode are stacked in a vertical direction with a separator interposed between the electrolyte and an electrolyte solution in an exterior body,
The exterior body is composed of two flexible printed wiring boards,
The flexible printed wiring board has a planar shape in which convex pieces projecting in a strip shape from a planar region including the electrode body are integrally formed, and a conductor layer is formed on a surface which is an inner surface of the exterior body. ,
The conductor layer is composed of a current collecting part including a planar region of the positive electrode and the negative electrode and a lead part extending in a band shape from the current collecting part along the convex piece,
The outer package is sealed by a peripheral region surrounding the current collector being welded by an insulating resin.
A power storage element.   2. The electric storage element according to claim 1, wherein the flexible printed wiring board is obtained by forming the conductor layer on a base made of a polyimide film.   3. The insulating resin for sealing the exterior body according to claim 2, wherein a frame-shaped polyimide film surrounding the current collector is used as a base, and a heat-melt adhesive layer is formed on both front and back surfaces of the base. A power storage element, which is a seal film. 4. The power storage element according to claim 1, wherein each of the sheet-like positive electrode and the negative electrode is accommodated in the exterior body. 5.

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