Flat-type battery

Abstract

To provide a flat-type battery that can save space and suppress internal short circuits. [Solution] The flat-type battery 1 comprises an outer casing 100 and an electrode body 41 housed in the internal space of the outer casing 100. The electrode body 41 consists of a plurality of positive electrode sheets 411 and a plurality of negative electrode sheets 412 that are alternately stacked. A negative electrode sheet 412 is arranged on one outermost layer of the electrode body 41, and a positive electrode sheet 411 is arranged on the other outermost layer. A positive electrode current collector foil 44 is arranged between a separator (outermost separator 411d) that covers the outermost positive electrode sheet 411 and the outer casing 100 (bottom 11 of the outer casing 10). The outer peripheral edge of the positive electrode current collector foil 44 is positioned inward from the outer peripheral edge of the outermost separator 411d.

Description

[Technical Field]

[0001] This invention relates to flat-type batteries such as coin-type batteries. [Background technology]

[0002] A flat-type battery is known that comprises a bottomed cylindrical outer can, a bottomed cylindrical sealing can positioned in an inverted dish shape relative to the outer can so as to form a space between them, and an electrode body positioned between the outer can and the sealing can. In such a flat-type battery, for example, as described in Japanese Patent Application Publication No. 2013-187182 (Patent Document 1) or International Publication No. 2018 / 120388 (Patent Document 2), an electrode body formed by alternately stacking a plurality of positive electrode sheets and a plurality of negative electrode sheets is housed within the internal space of the outer can formed by the outer can and the sealing can.

[0003] Patent Document 1 discloses a flat-type battery having alternatingly stacked positive and negative electrodes. The positive electrode has a flat plate-shaped positive electrode body and a positive electrode lead. The negative electrode has a flat plate-shaped negative electrode body and a negative electrode lead. The negative electrode body consists of a negative electrode current collector and negative electrode active material layers stacked on both sides of the negative electrode current collector. However, the negative electrode body located on the axial end side of the electrode body has the negative electrode active material layer on only one side of the negative electrode current collector so that the negative electrode current collector is located on the axial end side of the electrode body. Of the negative electrodes located on both axial ends of the electrode body, the negative electrode current collector of the negative electrode located on one end side contacts the flat surface of the negative electrode can when the electrode body is placed in the space of the battery case. The negative electrode current collector of the negative electrode body located on the other end side of the electrode body is positioned on the bottom of the positive electrode can via an insulating sheet and a positive electrode foil. In other words, in the electrode body of Patent Document 1, negative electrode bodies are arranged on both axial ends of the electrode body, and an insulating sheet is placed between the negative electrode body located at the other end of the electrode body and the positive electrode can.

[0004] Patent Document 2 discloses a button battery comprising a casing and a columnar cell provided within the casing. The columnar cell is formed by stacking a plurality of positive electrode sheets and a plurality of negative electrode sheets. In the columnar cell, the number of positive electrode sheets and negative electrode sheets are equal, and both ends of the columnar cell are a positive electrode sheet and a negative electrode sheet, respectively. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-187182 [Patent Document 2] International Publication No. 2018 / 120388 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of this disclosure is to provide a flat-type battery that can save space in the internal space of the outer casing and suppress the occurrence of internal short circuits. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the flat-type battery of this disclosure employs the following solutions. Specifically, the flat-type battery according to this disclosure comprises an outer casing, an electrode body housed in the internal space of the outer casing, and a positive electrode current collector foil disposed between the electrode body and the outer casing. The electrode body is formed by alternately stacking a plurality of positive electrode sheets and a plurality of negative electrode sheets. Each of the plurality of positive electrode sheets is covered by a bag-shaped separator. A positive electrode sheet is arranged on one of the outermost layers of the electrode body. A negative electrode sheet is arranged on the other outermost layer of the electrode body. The positive electrode current collector foil is disposed between the outer casing and a separator that covers the positive electrode sheet arranged on the outermost layer (hereinafter referred to as the "outermost separator" in this disclosure). In a plan view, the outer peripheral edge of the positive electrode current collector foil is positioned inside the outer peripheral edge of the outermost separator. [Effects of the Invention]

[0008] The flat-shaped battery of this disclosure allows for space saving in the internal space of the outer casing and suppresses the occurrence of internal short circuits. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a cross-sectional view of a flat-type battery according to an embodiment of the present disclosure. [Figure 2] Figure 2 is an enlarged cross-sectional view of the flat-shaped battery shown in Figure 1, located in the lower right corner. [Figure 3] Figure 3 is an enlarged cross-sectional view of the lower left side of the flat-shaped battery shown in Figure 1. [Figure 4] Figure 4 is a plan view of the positive electrode sheet shown in Figure 1. [Figure 5] Figure 5 is a plan view of the negative electrode sheet shown in Figure 1. [Figure 6] Figure 6 is a schematic diagram showing the positional relationship between the outermost separator and the positive electrode current collector foil shown in Figure 1. [Figure 7] Figure 7 is a schematic diagram showing a modified version of the outermost separator and positive electrode current collector foil shown in Figure 6. [Figure 8] Figure 8 is a cross-sectional view of a flat-type battery further equipped with a mesh current collector. [Modes for carrying out the invention]

[0010] The present inventors investigated the flat-type battery described in Patent Document 1 and considered removing the insulating sheet, which does not contribute to power generation, in order to save space inside the flat-type battery. By stacking multiple positive electrode sheets and multiple negative electrode sheets, with the negative electrode sheet positioned at one end in the axial direction of a substantially cylindrical electrode body and the positive electrode sheet covered by a bag-shaped separator positioned at the other end in the axial direction of the electrode body, the insulating sheet can be removed.

[0011] However, by removing the insulating sheet, the end portion of the positive current collector foil that is disposed between the electrode body and the exterior body and extends outward from the outer peripheral end of the electrode body becomes more likely to bend in the stacking direction of the electrode body. For example, the bending of the end portion of the positive current collector foil can occur due to pressing the electrode body in the direction of the positive current collector foil, or can occur when the electrode body and the positive current collector foil are bound by a binding band. When the end portion of the positive current collector foil bends, the end portion of the positive current collector foil becomes likely to contact the negative sheet or the negative lead, and a short circuit is likely to occur.

[0012] Therefore, as a result of intensive studies, the inventors of the present invention have found that if the size of the positive current collector foil in a plan view is made smaller than that of the separator (outermost separator) that covers the outermost positive sheet, bending of the end portion of the positive current collector foil can be suppressed, and occurrence of a short circuit due to contact between the positive current collector foil and the negative sheet or the negative lead can be suppressed. The present disclosure has been completed by the inventors based on such findings.

[0013] (Configuration 1) The flat battery according to an embodiment of the present disclosure includes an exterior body, an electrode body main body accommodated in an internal space of the exterior body, and a positive current collector foil disposed between the electrode body main body and the exterior body. The electrode body main body is formed by alternately stacking a plurality of positive sheets and a plurality of negative sheets. Each of the plurality of positive sheets is covered by a bag-shaped separator. A positive sheet is disposed on one outermost layer of the electrode body main body. A negative sheet is disposed on the other outermost layer of the electrode body main body. The positive current collector foil is disposed between the outermost separator and the exterior body. The outer peripheral end of the positive current collector foil is positioned inside the outer peripheral end of the outermost separator in a plan view.

[0014] Thereby, space saving in the internal space of the exterior body can be achieved, and occurrence of an internal short circuit can be suppressed.

[0015] (Configuration 2) A flat battery of Configuration 1, wherein the positive electrode current collector foil includes a first arc portion at its outer peripheral end. The outermost separator includes a second arc portion at its outer peripheral end. The shortest distance in a plan view between the outer peripheral end of the positive electrode current collector foil and the second arc portion of the outermost separator may be 0.1 mm or more. Thereby, internal short circuit can be more effectively suppressed.

[0016] (Configuration 3) A flat battery of Configuration 1 or 2, wherein the positive electrode current collector foil may have an area of 96% or less with respect to the area of the outermost separator in a plan view. Thereby, internal short circuit can be more effectively suppressed.

[0017] (Configuration 4) A flat battery of any one of Configurations 1 to 3 may further include a mesh current collector. The mesh current collector may be disposed between the exterior body and the positive electrode current collector foil. Thereby, the current collection efficiency can be improved.

[0018] (Configuration 5) A flat battery of Configuration 4, wherein the outer peripheral end of the mesh current collector may be positioned inside the outer peripheral end of the positive electrode current collector foil in a plan view. Thereby, the current collection efficiency can be further improved.

[0019] Hereinafter, the flat battery 1 of the embodiment according to the present disclosure will be specifically described with reference to FIGS. 1 to 8. Note that the same and corresponding configurations in the figures are denoted by the same reference numerals, and the same description will not be repeated. Also, in order to make the description easier to understand, in the drawings referred to below, the configurations are shown in a simplified or schematic manner, or some of the constituent members are omitted.

[0020] As shown in Figure 1, the flat-type battery 1 comprises a bottomed cylindrical outer casing 10, a sealing casing 20 that covers the opening of the outer casing 10, a gasket 30 positioned between the outer periphery of the outer casing 10 and the outer periphery of the sealing casing 20, and an electrode body 40 housed in the space formed between the outer casing 10 and the sealing casing 20. Therefore, when the outer casing 10 and the sealing casing 20 are combined, the flat-type battery 1 takes on an overall flat, coin shape. That is, the outer casing 10 and the sealing casing 20 constitute an outer casing 100 having an internal space. In addition to the electrode body 40, a non-aqueous electrolyte (not shown) is also sealed in the internal space of the outer casing 100.

[0021] The outer can 10 is made of a metal material such as stainless steel and is formed into a bottomed cylindrical shape by press molding. The outer can 10 has a circular bottom 11 and a cylindrical peripheral wall 12 that is formed continuously with the bottom 11 on its outer circumference. In a longitudinal cross-sectional view (as shown in Figure 1), this peripheral wall 12 is provided so as to extend almost vertically from the outer peripheral end of the bottom 11. As will be described later, with a gasket 30 sandwiched between the outer can 10 and the sealing can 20, the open end side of the peripheral wall 12 is bent inward and crimped to the sealing can 20.

[0022] The sealed can 20 is made of a metal material such as stainless steel and is formed into a bottomed cylindrical shape by press molding. The sealed can 20 has a cylindrical peripheral wall portion 22 whose outer diameter is smaller than the peripheral wall portion 12 of the outer can 10, and a circular flat portion 21 that closes one of its openings. The peripheral wall portion 22 is provided so as to extend almost perpendicularly to the flat portion 21 in a vertical cross-sectional view.

[0023] The gasket 30 is made of polypropylene (PP). The gasket 30 is positioned between the peripheral wall portion 12 and the peripheral wall portion 22 of the outer can 10 so as to be sandwiched between the peripheral wall portion 22 of the sealing can 20 and the peripheral wall portion 12 of the outer can 10. The material of the gasket 30 is not limited to PP; a resin composition containing an olefin-based elastomer in polyphenylene sulfide (PPS), polytetrafluoroethylene (PFA), polyamide resin, etc., may also be used.

[0024] The electrode body 40 includes an electrode body main body 41, a positive electrode connection part 42, and a negative electrode connection part 43.

[0025] The electrode body 41 has multiple positive electrode sheets 411 and multiple negative electrode sheets 412 that are stacked alternately. The electrode body 41 has a substantially cylindrical shape. The number of positive electrode sheets 411 and multiple negative electrode sheets 412 are the same, and the outermost layer of the electrode body 41 on the flat portion 21 side of the sealing can 20 is a negative electrode sheet 412, while the outermost layer on the bottom portion 11 side of the outer packaging can 10 is a positive electrode sheet 411.

[0026] As shown in Figures 2 and 3, the positive electrode sheet 411 has a positive electrode active material layer 411a containing a positive electrode active material such as lithium cobalt oxide, which is arranged on both sides of a positive electrode current collector 411b made of metal foil such as aluminum. As shown in Figure 4, the positive electrode sheet 411 has a shape in which a part of a disc is cut out, and the positive electrode lead 421 extends from the cut-out portion of the positive electrode sheet 411. The positive electrode sheet 411 is covered by a bag-shaped separator 411c. A part of the positive electrode lead 421, that is, the base end portion on the positive electrode sheet 411 side, is covered by an overhang 421a extending from the separator 411c. The overhang 421a is cylindrical, and the inside of the overhang 421a is in communication with the inside of the separator 411c.

[0027] As shown in Figures 1 to 3, the positive electrode sheet 411 closest to the bottom 11 of the outer container 10, in other words, the positive electrode sheet 411 located on the outermost layer of the electrode body 41, has a positive electrode active material layer 411a provided only on one side of the positive electrode current collector 411b so that the positive electrode current collector 411b faces the bottom 11. That is, the positive electrode active material layer 411a is not provided on the side of the positive electrode current collector 411b that faces the bottom 11.

[0028] The separator 411c is a bag-shaped member formed in a substantially circular shape in plan view, and is sized to accommodate the positive electrode sheet 411. The protruding portion 421a is sized to accommodate at least the base end portion of the positive electrode lead 421 on the positive electrode sheet 411 side. The separator 411c is made of a microporous thin film of polyethylene, which has excellent insulating properties. By making the separator 411c a microporous thin film in this way, lithium ions can permeate through the separator 411c. The separator 411c and the protruding portion 421a are formed by sandwiching the positive electrode sheet 411 and a portion of the positive electrode lead 421 closer to the positive electrode sheet 411 between two rectangular microporous thin film sheets, bonding the overlapping portions of the two sheets—the outer peripheral portion of the positive electrode sheet 411 and the outer portion of a portion of the positive electrode lead 421—by heat welding or the like, and then punching out the bonded portion along the outer shape of the positive electrode sheet 411 and the positive electrode lead 421.

[0029] As shown in Figures 2 and 3, the negative electrode sheet 412 has a negative electrode active material layer 412a containing a negative electrode active material such as graphite, which is arranged on both sides of a negative electrode current collector 412b made of metal foil such as copper. As shown in Figure 1, the negative electrode sheet 412 closest to the flat portion 21 of the sealing can 20 has the negative electrode active material layer 412a formed only on one side of the negative electrode current collector 412b so that the negative electrode current collector 412b faces the flat portion 21. As shown in Figure 5, the negative electrode sheet 412 has a shape in which a part of a disc is cut out, and the negative electrode lead 431 extends from the cut-out portion of the negative electrode sheet 412.

[0030] In this way, by placing the positive electrode sheet 411 on the outermost layer of the electrode body 41 on the bottom 11 side of the outer casing 10, there is no need to provide an insulating sheet between the electrode body 41 and the bottom 11. Therefore, the internal space of the outer casing 100 can be reduced by removing the insulating sheet. As a result, the flat-type battery 1 can be made smaller in proportion to the space saved internally. Alternatively, the capacity of the flat-type battery 1 can be increased by adding a positive electrode sheet 411 and a negative electrode sheet 412 to the space saved internally.

[0031] As shown in Figures 1 and 4, the positive electrode connection portion 42 is formed by bundling together the positive electrode leads 421 that extend outward from a plurality of positive electrode sheets 411 while bending them. The positive electrode connection portion 42 is connected to the positive electrode current collector foil 44.

[0032] The positive electrode current collector foil 44 is made of a metal such as an aluminum alloy. As shown in Figures 2 and 3, the positive electrode current collector foil 44 is positioned between the electrode body 40 and the bottom 11 of the outer casing 10. One main surface of the positive electrode current collector foil 44 faces and is in contact with the bag-shaped separator (hereinafter, among the separators 411c, the separator that covers the outermost positive electrode sheet 411 will be referred to as the "outermost separator 411d") that covers the outermost positive electrode sheet 411. The other main surface of the positive electrode current collector foil 44 faces and is in contact with the bottom 11 of the outer casing 10. Therefore, in this embodiment, the outer casing 10 functions as a positive electrode can.

[0033] As shown in Figures 2, 3, and 6, the outer edge of the positive electrode current collector foil 44 is positioned inward from the outer edge of the outermost separator 411d in a plan view, that is, viewed from above the main surface of the positive electrode sheet 411. In other words, the entire positive electrode current collector foil 44 is positioned inward from the outer edge of the outermost separator 411d in a plan view, and no part of the positive electrode current collector foil 44 extends outward from the outer edge of the outermost separator 411d. Although not shown here, a tab for connecting to the positive electrode lead 421 is formed from the outer edge of the positive electrode current collector foil 44.

[0034] As a result, even when the positive electrode sheet 411 is placed on the outermost layer on the bottom 11 side of the electrode body 41 and the insulating sheet is removed, bending of the positive electrode current collector foil 44 can be suppressed. Consequently, short circuits caused by contact between the positive electrode current collector foil 44 and the negative electrode sheet 412 or negative electrode lead 431 can be suppressed.

[0035] As shown in Figure 6, the positive electrode current collector foil 44 can include an arc portion 44a by cutting out a part of its circular shape in plan view. The outermost separator 411d can also include an arc portion 411e in part, corresponding to the cutout in the positive electrode sheet 411 described above. However, as shown in Figure 7, the positive electrode current collector foil 44 can be formed in a circular shape in plan view, and the entire outer circumference can be an arc portion 44a. As shown in the figure, a tab outlet portion 44b is formed from the outer circumference of the positive electrode current collector foil 44. Here, the outer circumference of the tab outlet portion 44b is connected to the arc-shaped outer circumference of the positive electrode current collector foil 44 by a smooth curve. In this case, the positive electrode current collector foil 44 can be formed in a circular shape with the dashed line shown as the boundary. Furthermore, since the outermost separator 411d is located on the outermost layer of the electrode body 40, it can be said that it does not contribute significantly to securing space for housing the positive electrode lead 421 inside the outer casing 10. Therefore, as shown in Figure 7, the outermost edge of the outermost separator 411d may be approximately an arc-shaped portion 411e.

[0036] As shown in Figures 6 and 7, the shortest distance D in a plan view is between the arc portion 44a at the outer edge of the positive electrode current collector foil 44 and the arc portion 411e at the outer edge of the outermost separator 411d. min It is preferable to make it 0.1 mm or more. This will more effectively suppress bending of the positive electrode current collector foil 44 and suppress internal short circuits. From this perspective, the shortest distance D min Preferably, it should be 0.3 mm or more, and more preferably 0.5 mm or more. On the other hand, the shortest distance D min If it is too large, it will cause poor current collection. Therefore, the shortest distance D min It is preferable that the distance be 1.2 mm or less, preferably 1.0 mm or less, and more preferably 0.8 mm or less. In other words, the shortest distance D min The thickness should be 0.1 mm to 1.2 mm, preferably 0.3 mm to 1.0 mm, and more preferably 0.5 mm to 0.8 mm.

[0037] As shown in Figure 6, when a notch is provided in a part of the outermost separator 411d, a part of the negative electrode sheet 412 is also notched in accordance with the notch in the outermost separator 411d (separator 411c). Therefore, the shortest distance between the outer peripheral edge of the notched portion of the outermost separator 411d and the notched portion of the positive electrode current collector foil 44 is the shortest distance D between the arc portion 44a and the arc portion 411e. min Even in smaller cases, short circuits due to bending of the positive electrode current collector foil 44 are unlikely to occur. Furthermore, the shortest distance between the outer peripheral edge of the notched portion of the outermost separator 411d and the notched portion of the positive electrode current collector foil 44 is defined as the shortest distance D between the arc portion 44a and the arc portion 411e. min By making it smaller, it is possible to increase the battery capacity.

[0038] As shown in Figures 6 and 7, the positive electrode current collector foil 44 may have an area of ​​96% or less of the area of ​​the outermost separator 411d in a plan view. This more effectively suppresses bending of the positive electrode current collector foil 44 and suppresses internal short circuits. From this viewpoint, the area of ​​the positive electrode current collector foil 44 is preferably 85% or less, and more preferably 75% or less, of the area of ​​the outermost separator 411d. On the other hand, if the area of ​​the positive electrode current collector foil 44 is too small, it can cause poor current collection. Therefore, the area of ​​the positive electrode current collector foil 44 is preferably 40% or more, preferably 50% or more, and more preferably 60% or more, of the area of ​​the outermost separator 411d. In other words, the area of ​​the positive electrode current collector foil 44 is preferably 40% to 96%, preferably 50% to 85%, and more preferably 60% to 75%, of the area of ​​the outermost separator 411d.

[0039] The negative electrode connection portion 43 is formed by bundling together negative electrode leads 431 extending outward from multiple negative electrode sheets 412 while bending them. As shown in Figure 1, the negative electrode connection portion 43 is connected to the negative electrode current collector 412b of the negative electrode sheet 412 closest to the flat portion 21 of the sealing can 20. Therefore, in this embodiment, the sealing can 20 functions as a negative electrode can.

[0040] Furthermore, as shown in Figure 8, a mesh current collector 45 may be provided between the positive electrode current collector foil 44 and the bottom 11 of the outer casing 10. The mesh current collector 45 may be made of, for example, SUS316. The mesh current collector 45 can be formed, for example, by punching out a circular shape from a mesh-like sheet having rhombic gaps in a plan view. However, the shape, mesh pattern, and material of the mesh current collector 45 are not limited to this. One end of the mesh current collector 45 in the axial direction (up and down direction in the figure) faces and contacts the positive electrode current collector foil 44. The other end of the mesh current collector 45 in the axial direction faces and contacts the bottom 11 of the outer casing 10. The flat-type battery 1 of this disclosure does not have an insulating sheet like the one described in Patent Document 1 above. Therefore, the contact pressure between the mesh current collector 45 and the bottom 11 becomes large. As a result, the current collection efficiency can be improved by providing the mesh current collector 45. In particular, the contact pressure between the mesh current collector 45 and the bottom 11 is greater near the geometric center of the positive electrode current collector foil 44 in a plan view. Therefore, it is preferable to position the outer edge of the mesh current collector 45 inward from the outer edge of the positive electrode current collector foil 44 in a plan view. This allows the outer edge of the mesh current collector 45 to contact the bottom 11 more strongly, thereby more effectively improving current collection efficiency.

[0041] In the above embodiment, the outer can 10 functions as the positive electrode can and the sealed can 20 functions as the negative electrode can. However, the opposite may also be true: the sealed can may be the positive electrode can and the outer can may be the negative electrode can.

[0042] Although embodiments have been described above, this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the disclosure.

[0043] Furthermore, according to the present invention, it is possible to contribute to Goal 7, "Ensure access to affordable, reliable, sustainable, and modern energy for all," and Goal 12, "Ensure sustainable consumption and production patterns," of the United Nations' Sustainable Development Goals (SDGs). [Examples]

[0044] Under the conditions of Examples 1 to 5 and Comparative Example 1 shown in Table 1 below, 20 flat batteries were fabricated each. For each flat battery, the presence or absence of short circuit and the presence or absence of current collection failure were confirmed, and each was expressed as a percentage. The outermost separator and the positive electrode current collector foil of the flat batteries of Examples 1 to 5 and the Comparative Example were each formed into the shape shown in FIG. 7. Further, the present disclosure is not limited by this example.

[0045]

Table 1

[0046] (Examples 1 to 4 and Comparative Example 1) In Examples 1 to 4, in a plan view, the size of the positive electrode current collector foil was smaller than that of the outermost separator, and the outer peripheral end of the positive electrode current collector foil was positioned inside the outer peripheral end of the outermost separator. On the other hand, in Comparative Example 1, the area of the positive electrode current collector foil and the outermost separator was the same, and the arc portion of the outer peripheral end of the positive electrode current collector foil was in contact with the arc portion of the outer peripheral end of the outermost separator. In the comparison between Examples 1 to 4 and Comparative Example 1, it was confirmed that no short circuit occurred in Examples 1 to 4, while a short circuit occurred at a rate of 20% in Comparative Example 1.

[0047] (Examples 3 and 4) When comparing Examples 3 and 4, in Example 4, since the size of the positive electrode current collector foil was smaller than that in Example 3, current collection failure occurred. Therefore, it was confirmed that the shortest distance D min should be 1.2 mm or more, and the area ratio should be 40% or more.

[0048] (Examples 2 and 5) When comparing Examples 2 and 5, in Example 5, since the size of the positive electrode current collector foil was slightly larger than that in Example 2, a slight short circuit occurred. Therefore, it was confirmed that the shortest distance D min should be 0.1 mm or more, and the area ratio should be 96% or less. However, in Example 2, the short circuit occurrence rate could be significantly reduced compared to Comparative Example 1.

Explanation of Signs

[0049] 1: Flat-type battery, 10: Outer casing, 20: Sealing casing, 30: Gasket, 40: Electrode body, 41: Electrode body main body, 42: Positive electrode connection part, 43: Negative electrode connection part, 411: Positive electrode sheet, 411c: Separator, 411d: Outermost separator, 412: Negative electrode sheet, 421: Positive electrode lead, 431: Negative electrode lead, 44: Positive electrode foil, 45: Mesh current collector

Claims

1. Exterior body and The electrode body is housed in the internal space of the outer casing, The electrode body and the outer casing are arranged to form a positive electrode current collector foil, The electrode body is formed by alternately stacking a plurality of positive electrode sheets and a plurality of negative electrode sheets. Each of the aforementioned multiple positive electrode sheets is covered by a bag-shaped separator. A positive electrode sheet is placed on one of the outermost layers of the electrode body. A negative electrode sheet is placed on the other outermost layer of the electrode body. The positive electrode current collector foil is positioned between the separator (hereinafter referred to as the outermost separator) that covers the positive electrode sheet arranged in the outermost layer and the outer casing. A flat-shaped battery in which the outer peripheral edge of the positive electrode current collector foil is positioned inside the outer peripheral edge of the outermost separator in a plan view.

2. A flat-shaped battery according to claim 1, The positive electrode current collector foil includes a first circular arc portion at its outer peripheral end. The outermost separator includes a second arc portion at its outer peripheral end. A flat-type battery in which the shortest distance in a plan view between the first arc portion of the positive electrode current collector foil and the second arc portion of the outermost separator is 0.1 mm or more.

3. A flat-shaped battery according to claim 1, The positive electrode current collector foil has an area of ​​96% or less of the area of ​​the outermost separator when viewed from above, in a flat-type battery.

4. A flat-shaped battery according to any one of claims 1 to 3, Furthermore, it is equipped with a mesh current collector, The mesh current collector is a flat-shaped battery positioned between the outer casing and the positive electrode current collector foil.

5. A flat-shaped battery according to claim 4, A flat-shaped battery in which the outer edge of the mesh current collector is positioned inward from the outer edge of the positive electrode current collector foil in a plan view.

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