Electricity storage unit

Abstract

An electricity storage cell is provided with: an electrode body having a strip-shaped electrode sheet; a laminated film that accommodates the electrode body such that a portion of the electrode sheet is exposed; and an insulating coating part which is provided on an end surface of the electrode body on which the electrode sheet is formed, and which covers a portion of the end surface on which the electrode sheet is not formed.

Description

Technical Field

[0001] This disclosure relates to energy storage units. Background Technology

[0002] For example, Japanese Patent Application Publication No. 2023-502698 discloses a battery having multiple electrode groups and a casing housing the multiple electrode groups. The multiple electrode groups include at least one electrode. Summary of the Invention

[0003] The electrode body has a coating portion and an electrode sheet. The coating portion is the area in the electrode foil of the positive or negative electrode sheet where an active material layer is provided. The electrode sheet is the area in the electrode foil of the positive or negative electrode sheet where no active material layer is provided, i.e., the uncoated portion of the exposed electrode foil. Typically, a long strip-shaped electrode sheet is formed on one side of the short side of the long strip-shaped coating portion. The short side direction of the coating portion corresponds to the first direction described later. A positive electrode sheet is formed at one end of the electrode body in the first direction, and a negative electrode sheet is formed at the other end of the electrode body in the first direction. To aggregate the electrode sheets, the electrode sheets are pressed from both ends of the end face of the electrode body in the short side direction. The short side direction of the end face of the electrode body corresponds to the second direction described later. As a result, the electrode foil of the electrode sheet is stretched from both ends of the long side direction of the end face to the center of the long side direction of the end face. The long side direction of the end face corresponds to the third direction described later. The electrode foil is stretched, thereby causing the electrode foil to break or form wrinkles on the electrode foil. In addition, the electrode foil in the positive or negative electrode sheet is located on the end face of the electrode body. Therefore, if foreign matter adheres to the end face of the electrode body, it may cause a short circuit within the electrode body.

[0004] One object of this disclosure is to suppress damage and wrinkling of the electrode foil and to suppress short circuits within the electrode body.

[0005] The energy storage unit disclosed herein includes: an electrode body having strip-shaped electrode sheets; a laminated film housing the electrode body with a portion of the electrode sheets exposed; and an insulating coating portion disposed in the electrode body on the end face where the electrode sheets are formed, and covering the portion of the end face where no electrode sheets are formed.

[0006] Preferably, the electrode body is formed in a manner that surrounds the imaginary wire. The electrode body includes a first end face and a second end face arranged in the direction in which the imaginary wire extends. An electrode sheet protrudes from the first end face in the direction in which the imaginary wire extends. The electrode sheet is bent in a direction that intersects with the direction in which the imaginary wire extends.

[0007] Preferably, the electrode sheet is bent in a direction that intersects the direction of extension of the imaginary winding line from the exposed portion of the laminated film. The energy storage unit also includes a current collector terminal connected to the front end of the bend in the exposed portion.

[0008] Preferably, the electrode sheet is bent in a direction intersecting the direction of extension of the imaginary winding line at the portion covered by the laminated film. The electrode sheet is further bent at the exposed portion from the laminated film. The energy storage unit also includes a current collector terminal connected to the bent front end in the exposed portion.

[0009] Preferably, at least one of the portion of the electrode sheet that contacts the laminated film and the portion of the laminated film that contacts the electrode sheet is roughened.

[0010] According to this disclosure, it is possible to suppress damage and wrinkles of the electrode foil, and to suppress short circuits within the electrode body. Attached Figure Description

[0011] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which like reference numerals denote like elements, and wherein:

[0012] Figure 1 This is a schematic side view of a vehicle having an energy storage device including an energy storage unit in one embodiment of the present disclosure.

[0013] Figure 2 This is a perspective view schematically representing an energy storage unit in one embodiment of the present disclosure.

[0014] Figure 3 This is a front view of an energy storage unit in one embodiment of the present disclosure.

[0015] Figure 4 yes Figure 3 A cross-sectional view at line IV-IV.

[0016] Figure 5 This is a three-dimensional view showing the group of electrode bodies included in each individual unit 100.

[0017] Figure 6 This is a diagram showing an example of the portion of the electrode sheet 114 that is in contact with the laminate 160 and an example of the portion of the laminate 160 that is in contact with the electrode sheet 114.

[0018] Figure 7 This is a cross-sectional view of a first modified example showing the connection portion of two single-unit cells 100 arranged in the first direction.

[0019] Figure 8 This is a cross-sectional view of a second modified example showing the connection portion of two single-unit cells 100 arranged in the first direction. Detailed Implementation

[0020] Hereinafter, embodiments and variations according to the present disclosure will be described with reference to the accompanying drawings. In the following description, the same reference numerals will be used to denote the same parts and components. Their names and functions are also the same. Therefore, detailed descriptions will not be repeated. Furthermore, the embodiments and variations described below can be selectively combined as appropriate.

[0022] Reference Figures 1-6 The energy storage unit in one embodiment of this disclosure will be described. Figure 1 This is a schematic side view of a vehicle having an energy storage device including an energy storage unit in one embodiment of the present disclosure. Figure 2 This is a perspective view schematically representing an energy storage unit in one embodiment of the present disclosure. Figure 3 This is a front view of an energy storage unit in one embodiment of the present disclosure.

[0023] Reference Figure 1 and Figure 2 The vehicle 10 includes an energy storage device 2 and a vehicle frame 3. The energy storage device 2 is located below the floor panel of the vehicle 10. The energy storage device 2 includes multiple energy storage units 1. Examples of vehicles 10 include hybrid vehicles, plug-in hybrid vehicles, fuel cell vehicles, and electric vehicles.

[0024] Reference Figure 2 and Figure 3 The energy storage unit 1 has multiple individual units 100, unit housings 300 and external terminals 400.

[0025] In this embodiment, the plurality of individual units 100 includes eight individual units 100. More specifically, four individual units 100 are arranged in a first direction and two individual units 100 are arranged in a second direction. In addition, the number of individual units 100 is not limited to eight.

[0026] The first direction could be vehicle 10 (refer to...) Figure 1 The first direction is the front-to-back direction of the battery cell 1, and the second direction is the width direction of the vehicle 10. The third direction is the height direction of the battery cell 1. The first direction is orthogonal to the second direction and the third direction. The second direction is orthogonal to the first direction and the third direction. The third direction is orthogonal to the first direction and the second direction. Each individual cell 100 has a shape that is longer in the first direction than in the second direction and extends longer in the third direction than in the first direction. Each individual cell 100 has a shape that extends longer in the third direction than in the second direction.

[0027] Each individual cell 100 can be, for example, a lithium-ion battery. Each individual cell 100 can also be composed of a so-called all-solid-state battery containing a solid electrolyte.

[0028] The unit housing 300 houses multiple individual units 100. The unit housing 300 is made of, for example, aluminum. The unit housing 300 is formed into a cuboid shape that is longer in a first direction.

[0029] The unit housing 300 has a housing body 310 and a cover 320. The housing body 310 is formed as a rectangular tube that is longer in a first direction. The housing body 310 surrounds a plurality of individual units 100.

[0030] The cover 320 is connected to the housing body 310 by welding or the like in a way that blocks the opening of the housing body 310.

[0031] External terminals 400 are disposed on cover 320. External terminals 400 are connected to electrode plates 114 of the individual unit 100 located closest to cover 320 among the plurality of individual units 100.

[0032] Figure 4 yes Figure 3 A cross-sectional view at line IV-IV. (Refer to...) Figure 4 The multiple single-unit units 100 include a first single-unit unit 101, a second single-unit unit 102, a third single-unit unit 103, and a fourth single-unit unit 104.

[0033] The first unit 101 is connected to the second unit 102. The first unit 101 and the second unit 102 are arranged in a first direction. The third unit 103 is connected to the fourth unit 104. The third unit 103 and the fourth unit 104 are arranged in a first direction.

[0034] The first unit 101 and the third unit 103 are adjacent to each other in the second direction. The second unit 102 and the fourth unit 104 are adjacent to each other in the second direction.

[0035] Each unit 100 includes at least one electrode body 110 and a laminate 160.

[0036] Figure 5 This is a perspective view showing the groups of electrode bodies included in each individual unit 100. (Refer to...) Figure 5 In this embodiment, each unit 100 includes two electrode bodies 110 (electrode body 110a and electrode body 110b). However, the number of electrode bodies 110 included in each unit 100 is not limited to two.

[0037] Each electrode body 110 is composed of a wound body formed by winding positive electrode material and negative electrode material through a separator. Furthermore, in Figure 5 In the example shown, each electrode body 110 is formed by winding a positive electrode sheet, a negative electrode sheet, and a separator around a wound imaginary line 118 extending along a first direction. Therefore, each electrode body 110 includes two end faces arranged in the first direction (the direction in which the wound imaginary line 118 extends). The two end faces of each electrode body 110 arranged along the first direction are an example of the "first end face and second end face" in this disclosure. Furthermore, the state in which each sheet is wound into a spiral shape can be visually confirmed in these two end faces. The two electrode bodies 110 are adjacent to each other in a second direction. The second direction corresponds to the stacking direction of the positive and negative electrode sheets. Each electrode body 110 is formed with a shape that is longer in the first direction.

[0038] Each electrode body 110 has a coating portion 112 and an electrode sheet 114. The coating portion 112 is the area in the electrode foil of the positive or negative electrode sheet where an active material layer is provided. The electrode sheet 114 is the area in the electrode foil of the positive or negative electrode sheet where no active material layer is provided, that is, the uncoated portion of the exposed electrode foil.

[0039] In each electrode body 110, a strip-shaped electrode sheet 114 is formed on at least one of the two end faces (first end face) arranged along a first direction. The first direction corresponds to the short side direction of the coating portion 112. The electrode sheet 114 protrudes from the first end face in the direction extending towards the winding imaginary line 118. Furthermore, in this embodiment, a plurality of electrode sheets 114 are formed. For example, in the positive and negative electrode sheets in their unwound state, a plurality of electrode sheets 114 are formed at intervals in the extending direction of each sheet. Moreover, in the state after each sheet is wound, each electrode sheet 114 is arranged in a second direction. However, the number of electrode sheets 114 may also be only one.

[0040] exist Figure 5 In the example shown, the positive electrode 114c of electrode body 110a protrudes from one end of the two end faces of electrode body 110a arranged along the first direction toward the direction in which the imaginary line 118a is wound. Conversely, the negative electrode 114d of electrode body 110a protrudes from the other end of the two end faces of electrode body 110a arranged along the first direction toward the direction in which the imaginary line 118a is wound. Similarly, the positive electrode 114c of electrode body 110b protrudes from one end of the two end faces of electrode body 110b arranged along the first direction toward the direction in which the imaginary line 118b is wound. Conversely, the negative electrode 114d of electrode body 110b protrudes from the other end of the two end faces of electrode body 110b arranged along the first direction toward the direction in which the imaginary line 118b is wound.

[0041] The positive electrode plates 114c of electrode bodies 110a and 110b are gathered at one end of electrode bodies 110a and 110b in a first direction. On the other hand, the negative electrode plates 114d of electrode bodies 110a and 110b are gathered at the other end of electrode bodies 110a and 110b in the first direction.

[0042] In each electrode body 110, an insulating coating portion 170 is provided on the end face where the electrode sheet 114 is formed. The coating portion 170 covers the portion of the end face of the electrode body 110 where the electrode sheet 114 is formed that does not have the electrode sheet 114 formed. That is, each individual unit 100 (refer to...) Figure 4 This includes electrode body 110 and laminate 160 (see reference). Figure 4 ) and the coating portion 170. The coating portion 170 suppresses short circuits within the electrode body 110.

[0043] Refer again Figure 4 In each individual unit 100, the laminate 160 houses the electrode body 110 such that a portion of the electrode sheet 114 of the electrode body 110 is exposed. (Refer to again...) Figure 5 More specifically, electrode bodies 110a and 110b are housed in a laminate 160 (see reference). Figure 4 In the state where the electrode bodies 110a and 110b are housed in a laminated film 160 (see reference 160), a portion of the positive electrode plate 114c of the electrode body 110a and a portion of the positive electrode plate 114c of the electrode body 110b are exposed at one end in the first direction of the electrode bodies 110a and 110b. Additionally, when the electrode bodies 110a and 110b are housed in the laminated film 160 (see reference 160), a portion of the positive electrode plate 114c of the electrode body 110a and a portion of the positive electrode plate 114c of the electrode body 110b are exposed at one end in the first direction of the electrode bodies 110a and 110b. Figure 4 In the state of ), a portion of the negative electrode plate 114d of electrode body 110a and a portion of the negative electrode plate 114d of electrode body 110b are exposed at the other end in the first direction of electrode bodies 110a and 110b.

[0044] Refer again Figure 4 Two individual units 100 arranged along the first direction are connected to each other by connecting the electrode plates 114 of the two individual units 100.

[0045] More specifically, the exposed portion 116 of the electrode sheet 114 of the first monomer unit 101, which protrudes from the laminate 160 of the first monomer unit 101, is connected to the exposed portion 116 of the electrode sheet 114 of the second monomer unit 102, which protrudes from the laminate 160 of the second monomer unit 102, by welding or the like. Thus, the first monomer unit 101 and the second monomer unit 102 are connected.

[0046] The exposed portion 116 of the electrode sheet 114 of the third monomer unit 103, which protrudes from the laminate 160 of the third monomer unit 103, is connected to the exposed portion 116 of the electrode sheet 114 of the fourth monomer unit 104, which protrudes from the laminate 160 of the fourth monomer unit 104, by welding or the like. Thus, the third monomer unit 103 and the fourth monomer unit 104 are connected.

[0047] Figure 6 This is a diagram showing one example of the portion of electrode sheet 114 that is in contact with the laminated film 160, and another example of the portion of laminated film 160 that is in contact with electrode sheet 114. (Refer to...) Figure 6 The portion 201 of the electrode sheet 114 that is in contact with the laminate 160 and the portion 202 of the laminate 160 that is in contact with the electrode sheet 114 are roughened.

[0048] Alternatively, at least one of portions 201 and 202 may be roughened. Alternatively, neither portion 201 nor portion 202 may be roughened. However, when at least one of portions 201 and 202 is roughened, peeling of the laminate 160 from the electrode sheet 114 can be suppressed.

[0049] Thus, the energy storage unit 1 in this embodiment includes an electrode body 110, a laminated film 160, and a coating portion 170. The electrode body 110 has strip-shaped electrode sheets 114. The laminated film 160 houses the electrode body 110 with a portion of the electrode sheets 114 exposed. The coating portion 170 is an insulating component provided on the end face of the electrode body 110 where the electrode sheets 114 are formed, covering the portion of the end face where the electrode sheets 114 are not formed.

[0050] Typically, in an electrode body, a long strip-shaped electrode sheet is formed on one side of the short side of the long strip-shaped coating portion. Therefore, it is necessary to press the electrode sheet from both ends of the short side of the end face of the electrode body to make the electrode sheet assemble. By pressing the electrode sheet from both ends of the short side of the end face of the electrode body, the electrode foil of the electrode sheet is stretched from both ends of the long side of the end face to the center of the long side of the end face, causing the electrode foil to break or form wrinkles. The short side of the coating portion corresponds to the first direction described above. The short side of the end face corresponds to the second direction described above. The long side of the end face corresponds to the third direction described above.

[0051] In contrast, in this embodiment, each electrode body 110 has a strip-shaped electrode sheet 114 formed on one side of the short side direction (the first direction described above) of the elongated strip-shaped coating portion 112. That is, the electrode body 110 in this embodiment does not have an elongated strip-shaped electrode sheet, but has a strip-shaped electrode sheet 114. As a result, when the electrode sheets 114 are gathered together, it is possible to suppress the stretching of the electrode foil of the electrode sheets 114. Therefore, the energy storage unit 1 in this embodiment can suppress the breakage and wrinkling of the electrode foil.

[0052] Furthermore, typically, the electrode foil in the positive or negative electrode sheet is located on the end face of the electrode body. Therefore, if foreign matter adheres to the end face of the electrode body, a short circuit may occur within the electrode body. In contrast, in this embodiment, the portion of the end face of the electrode sheet 114 formed in the electrode body 110 where the electrode sheet 114 is not formed is covered by an insulating coating 170. Therefore, the energy storage unit 1 in this embodiment can suppress short circuits within the electrode body 110.

[0053] Furthermore, in this embodiment, the two individual units 100 arranged in the first direction are connected to each other by connecting the electrode plates 114 of the two individual units 100. Therefore, in the energy storage unit 1 of this embodiment, no current collector terminal or the like is required to connect the two individual units 100 arranged in the first direction. Therefore, the energy storage unit 1 of this embodiment can reduce the number of components required for the energy storage unit 1.

[0054] [First Variation]

[0055] Reference Figure 7 A first modified example of the connection portion of two single-unit cells 100 arranged in the first direction will be described. Figure 7 This is a cross-sectional view of a first modified example showing the connection portion of two single-unit cells 100 arranged in the first direction.

[0056] In the first modified example, the electrode sheet 114 is positioned at the exposed portion 116 from the laminate 160 relative to the wound imaginary line 118 (see reference). Figure 5 The direction of extension intersects with the direction of bending. Figure 7 In the example shown, the electrode sheet 114 is bent in the second direction at the exposed portion 116. However, the direction in which the electrode sheet 114 is bent at the exposed portion 116 is not limited to the second direction, as long as it is a direction that intersects with the direction in which the imaginary winding line 118 extends.

[0057] In addition, in the first modified example, each individual unit 100 includes an electrode body 110, a laminate 160, and a coated portion 170 (see reference). Figure 5Additionally, in the first variation, each unit 100 further includes a current collector terminal 140. The current collector terminal 140 is connected to the bent front end portion 117 in the exposed portion 116.

[0058] The collector terminal 140 of the first unit 101 is connected to the collector terminal 140 of the second unit 102 by soldering or the like. The collector terminal 140 of the third unit 103 is connected to the collector terminal 140 of the fourth unit 104 by soldering or the like. That is, the collector terminal 140 of the first unit 101 is connected to the collector terminal 140 of the second unit 102 by soldering or the like, thereby connecting the first unit 101 and the second unit 102. In addition, the collector terminal 140 of the third unit 103 is connected to the collector terminal 140 of the fourth unit 104 by soldering or the like, thereby connecting the third unit 103 and the fourth unit 104.

[0059] In other respects, the first modification is the same as the embodiment described above. Thus, in the first modification, the electrode sheet 114 is bent at the exposed portion 116. Therefore, according to the first modification, the dimension in the first direction required for connecting the two individual units 100 arranged in the first direction can be shortened. That is, according to the first modification, the number of individual units 100 that can be housed in the energy storage unit 1 can be increased. Therefore, the energy storage unit 1 in the first modification can improve energy density.

[0060] Furthermore, in the first modification, the collector terminals 140 of the two individual units 100 arranged in the first direction are connected to each other by welding or the like. Normally, the electrode foil is prone to scattering due to heat. Therefore, when the electrode sheets 114 of the two individual units 100 arranged in the first direction are connected to each other by welding or the like, the connection operation of the two individual units 100 becomes more difficult. In contrast, in the first modification, the collector terminals 140 of the two individual units 100 arranged in the first direction are connected to each other by welding or the like. Therefore, according to the first modification, compared to the case where the electrode sheets 114 of the two individual units 100 arranged in the first direction are connected to each other by welding or the like, the two individual units 100 can be connected more easily.

[0061] [Second variation]

[0062] Reference Figure 8 A second variation of the connection portion of two single-unit cells 100 arranged in the first direction will be described. Figure 8 This is a cross-sectional view of a second modified example showing the connection portion of two single-unit cells 100 arranged in the first direction.

[0063] In the second variation, the electrode sheet 114 is positioned relative to the wound imaginary line 118 (see reference 160) at the portion covered by the laminate 160. Figure 5 The extension direction is bent in the direction that intersects with the direction in which the imaginary winding 118 extends. More specifically, the end 165 of the laminate 160 is bent in a direction that intersects with the direction in which the imaginary winding 118 extends. The electrode sheet 114 is bent along the laminate 160 at the portion covered by the laminate 160. Figure 8 In the example shown, the electrode sheet 114 is bent in the second direction at the portion covered by the laminate 160. However, the direction in which the electrode sheet 114 is bent at the portion covered by the laminate 160 is not limited to the second direction, as long as it is a direction that intersects with the direction in which the imaginary winding line 118 extends.

[0064] In addition, in the second modification, the electrode sheet 114 is further bent at the exposed portion 116 that protrudes from the laminate 160. Figure 8 In the example shown, the electrode sheet 114 is bent in the first direction (the direction in which the imaginary line 118 extends) at the exposed portion 116. However, the direction in which the electrode sheet 114 is bent at the exposed portion 116 is not limited to the first direction, as long as it is a direction that intersects with the direction in which the electrode sheet 114 is bent at the portion covered by the laminate 160.

[0065] In addition, in the second variation, each unit 100 includes an electrode body 110, a laminate 160, and a coated portion 170 (see reference). Figure 5 In addition, in the second variation, the energy storage unit 1 also includes at least one collector terminal 150. Collector terminals 151 and 152 are examples of at least one collector terminal 150. The collector terminal 150 is connected to the front end portion 117 of two individual units 100 arranged in the first direction.

[0066] More specifically, the current collector terminal 151 is connected to the bent front end portion 117 in the exposed portion 116 of the first unit 101 and the bent front end portion 117 in the exposed portion 116 of the second unit 102 via soldering or the like. The current collector terminal 152 is connected to the bent front end portion 117 in the exposed portion 116 of the third unit 103 and the bent front end portion 117 in the exposed portion 116 of the fourth unit 104 via soldering or the like. That is, the first unit 101 is connected to the second unit 102 via the current collector terminal 151. In addition, the third unit 103 is connected to the fourth unit 104 via the current collector terminal 152.

[0067] In other respects, the second modification is the same as the embodiment described above. Thus, in the second modification, the electrode sheet 114 is bent at the portion covered by the laminate 160 and at the exposed portion 116. Therefore, according to the second modification, the dimension in the first direction required for connecting the two individual units 100 arranged in the first direction can be shortened. That is, according to the second modification, the number of individual units 100 that can be housed in the energy storage unit 1 can be increased. Therefore, the energy storage unit 1 in the second modification can improve energy density.

[0068] Furthermore, in the second modification, the two individual units 100 arranged in the first direction are connected via a current collector terminal 150. Therefore, according to the second modification, compared to the case where the electrode plates 114 of the two individual units 100 arranged in the first direction are connected to each other by welding or the like, the two individual units 100 can be easily connected.

[0069] [Other variations]

[0070] Each electrode body 110 may also be composed of a laminate formed by stacking positive and negative electrode sheets via separators. Similar to a wound body, the electrode foil may break or wrinkle in the laminate. Furthermore, similar to a wound body, the electrode foil in the positive or negative electrode sheet is located at the end face of the electrode body. Therefore, if foreign matter adheres to the end face of the electrode body, a short circuit may occur within the electrode body. When each electrode body 110 is composed of a laminate of positive and negative electrode sheets stacked with separators, according to the above embodiment or its variations, damage and wrinkling of the electrode foil can be suppressed, and short circuits within the electrode body can be suppressed.

[0071] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of this disclosure is not defined by the foregoing description, but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

Claims

1. An energy storage unit, comprising: The electrode body has strip-shaped electrode plates; A laminated film is used to house the electrode body with a portion of the electrode sheet exposed; and An insulating coating is provided on the end face of the electrode body where the electrode sheet is formed, and covers the portion of the end face where the electrode sheet is not formed.

2. The energy storage unit according to claim 1, wherein, The electrode body is formed in such a way that it surrounds the imaginary wire. The electrode body includes a first end face and a second end face arranged in the direction in which the imaginary wound line extends. The electrode sheet protrudes from the first end towards the direction in which the imaginary winding extends. The electrode sheet is bent in a direction that intersects with the direction in which the imaginary winding extends.

3. The energy storage unit according to claim 2, wherein, The electrode sheet is bent in a direction that intersects with the direction in which the imaginary winding extends from the exposed portion of the laminated film. The energy storage unit also has a collector terminal that is connected to the bent front end of the exposed portion.

4. The energy storage unit according to claim 2, wherein, The electrode sheet is bent at the portion covered by the laminate in a direction that intersects with the direction in which the imaginary winding extends. The electrode sheet is further bent at the exposed portion that protrudes from the laminated film. The energy storage unit also has a collector terminal that is connected to the bent front end of the exposed portion.

5. The energy storage unit according to any one of claims 1 to 4, wherein, At least one of the portion of the electrode sheet that is in contact with the laminated film and the portion of the laminated film that is in contact with the electrode sheet is roughened.

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