Power storage cell and method of manufacturing electrode body

Abstract

To provide a power storage cell that can achieve both of improvement of an energy density and reduction of precipitation of lithium ions onto a negative electrode sheet.SOLUTION: A power storage cell 1 includes: an electrode body formed by a wound body formed by winding a positive electrode sheet 110 and a negative electrode sheet 120 through a separator 130; and a cell case that accommodates the electrode body. The positive electrode sheet 110 includes a positive electrode current collector 112, an inner positive electrode active material layer 114, and an outer positive electrode active material layer 116. The negative electrode sheet 120 includes a negative electrode current collector 122, an inner negative electrode active material layer 124, and an outer negative electrode active material layer 126. The cell case 300 is formed in a cuboid shape. The electrode body includes four corner portions 105r. The positive electrode current collector 112 at the corner portion 105r includes a positive electrode exposed portion 122A. The negative electrode current collector 122 at the corner portion 105r includes only a negative electrode covered portion 122B.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electric storage cell and an electrode assembly. [Background technology]

[0002] For example, Japanese Patent Application Laid-Open Publication No. 2023-47012 discloses a secondary battery including a wound electrode assembly and a rectangular battery case that houses the wound electrode assembly. The wound electrode assembly is formed by winding a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween. The positive electrode sheet has a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The negative electrode sheet has a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector.

[0003] The wound electrode body is wound so that its shape when viewed from the axial direction of the wound electrode body is rectangular. The wound electrode body has corners located at the four corners of the wound electrode body when viewed from the axial direction. Fold grooves are formed along the winding axis direction at the corners of the positive electrode active material layer and the negative electrode active material layer.

[0004] The fold grooves include an inner positive electrode fold groove formed in the inner positive electrode active material layer, an outer positive electrode fold groove formed in the outer positive electrode active material layer, an inner negative electrode fold groove formed in the inner negative electrode active material layer, and an outer negative electrode fold groove formed in the outer negative electrode active material layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-47012 Summary of the Invention [Problem to be solved by the invention]

[0006] In the secondary battery described in JP 2023-47012 A, the dead space between the wound electrode body and the battery case is reduced, thereby increasing the energy density. However, in this secondary battery, there is a concern that lithium ions may precipitate on the negative electrode sheet during charging.

[0007] An object of the present disclosure is to provide a method for manufacturing an energy storage cell and an electrode assembly that can achieve both an improvement in energy density and suppression of lithium ion deposition on a negative electrode sheet. [Means for solving the problem]

[0008] An energy storage cell according to one aspect of the present disclosure includes: an electrode assembly configured as a wound body formed by winding a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween; and a cell case that accommodates the electrode assembly; the positive electrode sheet has a positive electrode current collector, an inner positive electrode active material layer provided inside the positive electrode current collector in a radial direction of the wound body, and an outer positive electrode active material layer provided outside the positive electrode current collector in the radial direction; and the negative electrode sheet has a negative electrode current collector and an outer positive electrode active material layer formed inside the negative electrode current collector in the radial direction. the cell case is formed in a rectangular parallelepiped shape, the electrode body has four corners when the electrode body is viewed in the axial direction of the wound body, the positive electrode current collector at the corners includes a positive electrode exposed portion where the inner positive electrode active material layer and the outer positive electrode active material layer are not provided, and the negative electrode current collector at the corners has only a negative electrode covered portion covered with the inner negative electrode active material layer and the outer negative electrode active material layer.

[0009] A method for manufacturing an electrode assembly in an energy storage cell according to one aspect of the present disclosure includes: a positive electrode sheet preparation step of preparing a positive electrode sheet having a positive electrode current collector, an inner positive electrode active material layer provided on one surface of the positive electrode current collector, and an outer positive electrode active material layer provided on the other surface of the positive electrode current collector; a negative electrode sheet preparation step of preparing a negative electrode sheet having a negative electrode current collector, an inner negative electrode active material layer provided on one surface of the negative electrode current collector, and an outer negative electrode active material layer provided on the other surface of the negative electrode current collector; and a winding step of winding the positive electrode sheet and the negative electrode sheet with a separator interposed therebetween to form the electrode assembly constituted of a wound body, In the positive electrode sheet preparation step, the inner positive electrode active material layer and the outer positive electrode active material layer are provided by intermittent coating so that positive electrode exposed portions where the inner positive electrode active material layer and the outer positive electrode active material layer are not provided are formed on the one surface and the other surface of the positive electrode current collector; in the negative electrode sheet preparation step, the inner negative electrode active material layer and the outer negative electrode active material layer are provided by continuous coating on the one surface and the other surface of the negative electrode current collector; and in the winding step, the positive electrode sheet, the negative electrode sheet, and the separator are wound so that the positive electrode exposed portions are located at four corners when the wound body is viewed in the axial direction of the wound body. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a method for manufacturing an energy storage cell and an electrode assembly that can achieve both an improvement in energy density and suppression of lithium ion deposition on a negative electrode sheet. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view schematically illustrating a storage cell according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a front view of the storage cell. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a cross-sectional view schematically showing a corner of a cell unit. [Figure 5]FIG. 2 is a plan view of the positive electrode sheet and the negative electrode sheet in an unfolded state. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure will be described with reference to the accompanying drawings, in which the same or corresponding elements are designated by the same reference numerals.

[0013] Fig. 1 is a perspective view schematically showing a storage cell according to an embodiment of the present disclosure. Fig. 2 is a front view of the storage cell. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Fig. 4 is a cross-sectional view schematically showing a corner of a cell unit. This storage cell 1 is mounted, for example, on the bottom of a vehicle.

[0014] As shown in FIGS. 1 to 4, the energy storage cell 1 includes a plurality of cell units 100, a covering sheet 200, a cell case 300, and an external terminal 400.

[0015] As shown in FIG. 2 , the plurality of cell units 100 includes a first cell unit 101, a second cell unit 102, a third cell unit 103, and a fourth cell unit 104. In this embodiment, the plurality of cell units 100 includes eight cell units 100. However, the number of cell units 100 is not limited to eight. Each cell unit 100 may be, for example, a lithium-ion battery. Each cell unit 100 may be configured as a so-called all-solid-state battery including a solid electrolyte.

[0016] The first cell unit 101 is connected to the third cell unit 103. The second cell unit 102 is connected to the fourth cell unit 104. The first cell unit 101 and the second cell unit 102 are adjacent to each other in a second direction (a direction perpendicular to the paper surface in FIG. 2) that is perpendicular to both the first direction in which the first cell unit 101 and the third cell unit 103 are aligned and the vertical direction. The third cell unit 103 and the fourth cell unit 104 are adjacent to each other in the second direction. Each cell unit 100 has a shape that is longer in the first direction than in the second direction and that extends longer in the first direction than in the vertical direction. Each cell unit 100 has a shape that extends longer in the vertical direction than in the second direction.

[0017] As shown in FIGS. 2 and 3, each cell unit 100 has at least one electrode assembly 105 , a current collecting terminal 140 , and a laminate exterior body 160 .

[0018] As shown in FIG. 3, at least one electrode body 105 includes two electrode bodies 105. However, the number of electrode bodies 105 is not limited to two. As shown in FIG. 4, each electrode body 105 is configured as a wound body in which a positive electrode sheet 110 and a negative electrode sheet 120 are wound with a separator 130 interposed therebetween. The two electrode bodies 105 are adjacent to each other in the stacking direction in which the positive electrode sheet 110 and the negative electrode sheet 120 are stacked on each other. Each electrode body 105 is formed in a shape elongated in an orthogonal direction (axial direction of the wound body) that is orthogonal to both the stacking direction and the up-down direction. The stacking direction (thickness direction) corresponds to the second direction, and the orthogonal direction (axial direction of the wound body) corresponds to the first direction.

[0019] The current collecting terminal 140 is connected to the electrode body 105. The current collecting terminal 140 protrudes from the electrode body 105 in a first direction. The current collecting terminal 140 electrically connected to the positive electrode sheet 110 of the electrode body 105 is made of, for example, aluminum. The current collecting terminal 140 electrically connected to the negative electrode sheet 120 of the electrode body 105 is made of, for example, copper. The current collecting terminal 140 is formed in a flat plate shape.

[0020] The laminated exterior body 160 houses two electrode assemblies 105. The laminated exterior body 160 is made of a laminated film. The current collecting terminal 140 protrudes from an edge of the laminated exterior body 160 in a first direction.

[0021] The covering sheet 200 covers the multiple cell units 100. More specifically, the covering sheet 200 covers the multiple cell units 100 so as to surround the multiple cell units 100 collectively. The covering sheet 200 is made of an insulating material (synthetic resin, etc.). Note that the covering sheet 200 may be omitted.

[0022] The cell case 300 houses a plurality of cell units 100. The cell case 300 is made of, for example, aluminum. The cell case 300 is formed in a rectangular parallelepiped shape. Each cell unit 100 is housed in the cell case 300 with the central axis of the electrode assembly 105 parallel to the first direction. As shown in FIGS. 1 to 3, the cell case 300 has a case body 310 and a lid 320.

[0023] The case body 310 is formed in the shape of a rectangular tube that opens in a first direction. The case body 310 extends long in the first direction. The case body 310 surrounds the multiple cell units 100 and the cover sheet 200.

[0024] The lid 320 is connected to the case body 310 by welding or the like so as to close the opening of the case body 310 .

[0025] The external terminal 400 is provided on the lid 320. The external terminal 400 is connected to the current collecting terminal 140 of the cell unit 100 that is positioned closest to the lid 320 among the multiple cell units 100.

[0026] Here, a detailed description will be given of the electrode body 105. As shown in Figures 3 and 4, each electrode body 105 has four corners 105r when the electrode body 105 is viewed in the axial direction of the wound body.

[0027] As shown in Fig. 4, the positive electrode sheet 110 has a positive electrode current collector 112, an inner positive electrode active material layer 114, and an outer positive electrode active material layer 116. The positive electrode current collector 112 is made of a metal such as aluminum. The inner positive electrode active material layer 114 is provided on the inner surface of the positive electrode current collector 112 in the radial direction of the wound body. The outer positive electrode active material layer 116 is provided on the outer surface of the positive electrode current collector 112 in the radial direction. The positive electrode sheet 110 includes an outermost positive electrode sheet portion 111 arranged on the outermost periphery of the wound body.

[0028] The negative electrode sheet 120 has a negative electrode current collector 122, an inner negative electrode active material layer 124, and an outer negative electrode active material layer 126. The negative electrode current collector 122 is made of a metal such as copper. The inner negative electrode active material layer 124 is provided on the inner surface of the negative electrode current collector 122 in the radial direction. The outer negative electrode active material layer 126 is provided on the outer surface of the negative electrode current collector 122 in the radial direction.

[0029] 4, the positive electrode current collector 112 has a positive electrode exposed portion 112A and a positive electrode covering portion 112B. Both the positive electrode exposed portion 112A and the positive electrode covering portion 112B are formed on the corner portion 105r.

[0030] The positive electrode exposed portion 112A is a portion of the positive electrode current collector 112 where the inner positive electrode active material layer 114 and the outer positive electrode active material layer 116 are not provided. That is, the positive electrode current collector 112 is exposed in the positive electrode exposed portion 112A.

[0031] The positive electrode covering portion 112B is a portion of the positive electrode current collector 112 where the inner positive electrode active material layer 114 and the outer positive electrode active material layer 116 are provided. That is, the positive electrode covering portion 112B is covered with the inner positive electrode active material layer 114 and the outer positive electrode active material layer 116.

[0032] The positive electrode covering portion 112B is formed on the positive electrode collector 112 of the outermost positive electrode sheet portion 111 among the plurality of positive electrode collectors 112 at the corner 105r. The positive electrode exposed portion 112A is formed on each positive electrode collector 112 that is disposed more inward than the outermost positive electrode sheet portion 111 among the plurality of positive electrode collectors 112 at the corner 105r.

[0033] As shown in FIG. 4, the inner positive electrode active material layer 114 provided at a position adjacent to the positive electrode exposed portion 112A in the circumferential direction of the paper roll has an opposing surface 114a that faces the positive electrode exposed portion 112A with a gap therebetween.

[0034] The negative electrode current collector 122 at the corner 105r has only a negative electrode covering portion 122B that is covered with the inner negative electrode active material layer 124 and the outer negative electrode active material layer 126.

[0035] Next, a method for manufacturing the electrode assembly 105 will be described with reference to Fig. 5. This manufacturing method includes a positive electrode sheet preparation step, a negative electrode sheet preparation step, and a winding step.

[0036] In the positive electrode sheet preparation step, the above-described positive electrode sheet 110 is prepared. As shown in FIG. 5 , the unfolded positive electrode sheet 110 includes a strip-shaped positive electrode current collector 112, an inner positive electrode active material layer 114 intermittently provided on one surface of the positive electrode current collector 112 along the longitudinal direction of the positive electrode current collector 112, and an outer positive electrode active material layer 116 intermittently provided on the other surface of the positive electrode current collector 112 along the longitudinal direction of the positive electrode current collector 112. The inner positive electrode active material layer 114 and the outer positive electrode active material layer 116 are formed in positions where they overlap each other in the thickness direction. In the positive electrode sheet preparation step, the inner positive electrode active material layer 114 and the outer positive electrode active material layer 116 are provided on each surface of the positive electrode current collector 112 by intermittent coating so that a positive electrode exposed portion 112A is formed on the positive electrode current collector 112. In FIG. 5, the inner positive electrode active material layer 114 is indicated by dots, and the portion where the positive electrode covering portion 112B is formed (the portion that is bent in the winding step) is indicated by a dashed dotted line.

[0037] In the negative electrode sheet preparation step, the above-described negative electrode sheet 120 is prepared. As shown in FIG. 5 , the negative electrode sheet 120 in an unfolded state includes a strip-shaped negative electrode current collector 122, an inner negative electrode active material layer 124 continuously provided on one surface of the negative electrode current collector 122 along the longitudinal direction of the negative electrode current collector 122, and an outer negative electrode active material layer 126 continuously provided on the other surface of the negative electrode current collector 122 along the longitudinal direction of the negative electrode current collector 122. The inner negative electrode active material layer 124 and the outer negative electrode active material layer 126 are formed in positions where they overlap each other in the thickness direction. In the negative electrode sheet preparation step, the inner negative electrode active material layer 124 and the outer negative electrode active material layer 126 are provided on each surface of the negative electrode current collector 122 by continuous coating so that a negative electrode coating portion 122B is formed on the negative electrode current collector 122. In FIG. 5, the inner negative electrode active material layer 124 is indicated by diagonal lines, and the portion where the negative electrode covering portion 122B is to be formed (the portion that is folded in the winding step) is indicated by dashed lines.

[0038] In the winding step, the positive electrode sheet 110 and the negative electrode sheet 120 are wound with the separator 130 interposed therebetween. Specifically, in this step, the positive electrode sheet 110, the negative electrode sheet 120, and the separator 130 are wound so that the positive electrode exposed portions 112A are located at the four corners 105r when the wound body is viewed in the axial direction of the wound body.

[0039] As described above, in the energy storage cell 1 of this embodiment, the electrode body 105 having four corners 105r is housed in the cell case 300 formed in a rectangular parallelepiped shape, thereby increasing the energy density. Furthermore, since the positive electrode current collector 112 at the corner 105r includes the positive electrode exposed portion 112A and the negative electrode current collector 122 at the corner 105r has only the negative electrode covered portion 122B, deposition of lithium ions onto the negative electrode sheet 120 during charging is suppressed.

[0040] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0041] [Aspect 1] an electrode assembly formed by a wound body formed by winding a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween; a cell case that houses the electrode assembly, The positive electrode sheet is a positive electrode current collector; an inner positive electrode active material layer provided on an inner surface of the positive electrode current collector in a radial direction of the wound body; an outer positive electrode active material layer provided on an outer surface of the positive electrode current collector in the radial direction, The negative electrode sheet is a negative electrode current collector; an inner negative electrode active material layer provided on an inner surface of the negative electrode current collector in the radial direction; an outer negative electrode active material layer provided on an outer surface of the negative electrode current collector in the radial direction, The cell case is formed in a rectangular parallelepiped shape, the electrode body has four corners when viewed in the axial direction of the wound body, the positive electrode current collector at the corner portion includes a positive electrode exposed portion on which the inner positive electrode active material layer and the outer positive electrode active material layer are not provided, The negative electrode current collector at the corner portion has only a negative electrode covering portion that is covered with the inner negative electrode active material layer and the outer negative electrode active material layer.

[0042] In this energy storage cell, the electrode body has four corners, thereby increasing the energy density. In addition, the positive electrode current collector at the corners includes a positive electrode exposed portion, and the negative electrode current collector at the corners has only a negative electrode covered portion, thereby suppressing the deposition of lithium ions onto the negative electrode sheet during charging.

[0043] [Aspect 2] the positive electrode sheet includes an outermost positive electrode sheet portion arranged at the outermost periphery of the wound body, 2. The energy storage cell according to claim 1, wherein the positive electrode current collector of the outermost positive electrode sheet portion at the corner portion has a positive electrode covering portion that is covered with the inner positive electrode active material layer and the outer positive electrode active material layer.

[0044] In this embodiment, the positive electrode current collector of the outermost positive electrode sheet portion, which has a relatively large radius of curvature, has each positive electrode active material layer, making it possible to increase capacity while suppressing cracks and the like in each positive electrode active material layer at the corners.

[0045] [Aspect 3] 3. The energy storage cell according to claim 1, wherein the inner positive electrode active material layer provided at a position adjacent to the positive electrode exposed portion in the circumferential direction of the wound body has an opposing surface facing the positive electrode exposed portion with a gap therebetween.

[0046] [Aspect 4] A method for manufacturing an electrode assembly in a storage cell, comprising: a positive electrode sheet preparation step of preparing a positive electrode sheet including a positive electrode current collector, an inner positive electrode active material layer provided on one surface of the positive electrode current collector, and an outer positive electrode active material layer provided on the other surface of the positive electrode current collector; a negative electrode sheet preparation step of preparing a negative electrode sheet including a negative electrode current collector, an inner negative electrode active material layer provided on one surface of the negative electrode current collector, and an outer negative electrode active material layer provided on the other surface of the negative electrode current collector; a winding step of winding the positive electrode sheet and the negative electrode sheet with a separator interposed therebetween to form the electrode assembly constituted by a wound body, in the positive electrode sheet preparation step, the inner positive electrode active material layer and the outer positive electrode active material layer are provided by intermittent coating so that positive electrode exposed portions, on which the inner positive electrode active material layer and the outer positive electrode active material layer are not provided, are formed on the one surface and the other surface of the positive electrode current collector; In the negative electrode sheet preparation step, the inner negative electrode active material layer and the outer negative electrode active material layer are provided by continuous coating on the one surface and the other surface of the negative electrode current collector, In the winding step, the positive electrode sheet, the negative electrode sheet, and the separator are wound so that the positive electrode exposed portion is located at four corners of the wound body when viewed in the axial direction of the wound body.

[0047] It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present disclosure is defined by the claims rather than the description of the above embodiments, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0048] 1 storage cell, 100 cell unit, 105 electrode body, 105r corner portion, 110 positive electrode sheet, 111 outermost positive electrode sheet portion, 112 positive electrode current collector, 112A positive electrode exposed portion, 112B positive electrode coating portion, 114 inner positive electrode active material layer, 114a opposing surface, 116 outer positive electrode active material layer, 120 negative electrode sheet, 122 negative electrode current collector, 122B negative electrode coating portion, 124 inner negative electrode active material layer, 126 outer negative electrode active material layer, 130 separator, 140 current collecting terminal, 160 laminate outer casing, 200 coating sheet, 300 cell case, 310 case main body, 320 lid, 400 external terminal.

Claims

1. an electrode assembly formed by a wound body formed by winding a positive electrode sheet and a negative electrode sheet with a separator interposed therebetween; a cell case that houses the electrode assembly, The positive electrode sheet is a positive electrode current collector; an inner positive electrode active material layer provided on an inner surface of the positive electrode current collector in a radial direction of the wound body; an outer positive electrode active material layer provided on an outer surface of the positive electrode current collector in the radial direction, The negative electrode sheet is a negative electrode current collector; an inner negative electrode active material layer provided on an inner surface of the negative electrode current collector in the radial direction; an outer negative electrode active material layer provided on an outer surface of the negative electrode current collector in the radial direction, The cell case is formed in a rectangular parallelepiped shape, the electrode body has four corners when viewed in the axial direction of the wound body, the positive electrode current collector at the corner portion includes a positive electrode exposed portion on which the inner positive electrode active material layer and the outer positive electrode active material layer are not provided, The negative electrode current collector at the corner portion has only a negative electrode covering portion that is covered with the inner negative electrode active material layer and the outer negative electrode active material layer.

2. the positive electrode sheet includes an outermost positive electrode sheet portion arranged at the outermost periphery of the wound body, 2 . The energy storage cell according to claim 1 , wherein the positive electrode current collector of the outermost positive electrode sheet portion at the corner portion has a positive electrode covering portion covered with the inner positive electrode active material layer and the outer positive electrode active material layer.

3. 3. The energy storage cell according to claim 1, wherein the inner positive electrode active material layer provided at a position adjacent to the positive electrode exposed portion in the circumferential direction of the wound body has an opposing surface that faces the positive electrode exposed portion with a gap therebetween.

4. A method for manufacturing an electrode assembly in a storage cell, comprising: a positive electrode sheet preparation step of preparing a positive electrode sheet including a positive electrode current collector, an inner positive electrode active material layer provided on one surface of the positive electrode current collector, and an outer positive electrode active material layer provided on the other surface of the positive electrode current collector; a negative electrode sheet preparation step of preparing a negative electrode sheet including a negative electrode current collector, an inner negative electrode active material layer provided on one surface of the negative electrode current collector, and an outer negative electrode active material layer provided on the other surface of the negative electrode current collector; a winding step of winding the positive electrode sheet and the negative electrode sheet with a separator interposed therebetween to form the electrode assembly constituted by a wound body, in the positive electrode sheet preparation step, the inner positive electrode active material layer and the outer positive electrode active material layer are provided by intermittent coating so that positive electrode exposed portions, on which the inner positive electrode active material layer and the outer positive electrode active material layer are not provided, are formed on the one surface and the other surface of the positive electrode current collector; In the negative electrode sheet preparation step, the inner negative electrode active material layer and the outer negative electrode active material layer are provided by continuous coating on the one surface and the other surface of the negative electrode current collector, In the winding step, the positive electrode sheet, the negative electrode sheet, and the separator are wound so that the positive electrode exposed portion is located at four corners of the wound body when viewed in the axial direction of the wound body.

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