Energy storage cell

Abstract

The present invention provides a power storage cell that can suppress the increase in size of the case that houses the electrode body formed by winding electrode sheets. [Solution] The energy storage cell 100 comprises an electrode body 10 in which a first electrode 10A is wound around a winding axis α, and a case 20 that houses the electrode body 10. The first electrode 10A includes a first current collector 11A. The electrode body 10 includes a bent portion 10E. The first current collector 11A has a bent portion 11E corresponding to the bent portion 10E. The bent portion 11E has an expandable / contractable portion 80 that can expand and contract in the winding direction of the electrode body 10.

Description

Technical Field

[0001] The present disclosure relates to a storage cell.

Background Art

[0002] Japanese Patent Application Publication No. 2023-517924 (Patent Document 1) discloses an electrode assembly formed by winding a positive electrode sheet and a negative electrode sheet. A bending region is formed in each of the positive electrode sheet and the negative electrode sheet. The electrode assembly is housed in a housing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1 described above, as described above, bending regions are formed in the positive electrode sheet and the negative electrode sheet. In this case, for example, when the bending rigidity of the sheet (electrode sheet) is relatively high, it may be difficult to bend the sheet compactly. In this case, it is conceivable that the housing (case) becomes larger.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a storage cell capable of suppressing an increase in the size of a case that houses an electrode body formed by winding an electrode sheet.

Means for Solving the Problems

[0006] A storage cell according to one aspect of the present disclosure comprises a wound electrode body in which an electrode sheet is wound around a winding axis, and a case housing the wound electrode body. The electrode sheet includes a conductive sheet and an electrode active material layer formed on the surface of the conductive sheet. The wound electrode body includes at least one bent portion. The conductive sheet has a bent portion corresponding to at least one bent portion. The bent portion has an expandable portion that is expandable and contractible in the winding direction of the wound electrode body. [Effects of the Invention]

[0007] According to this disclosure, it is possible to suppress the increase in size of the case that houses the electrode body formed by winding the electrode sheet. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view showing the configuration of the energy storage device and frame members according to this embodiment. [Figure 2] This is a perspective view showing the configuration of the energy storage cell according to this embodiment. [Figure 3] This is an exploded perspective view showing the configuration of the energy storage cell according to this embodiment. [Figure 4] This is a cross-sectional view of the electrode body according to this embodiment. [Figure 5] This is a cross-sectional view showing the configuration of the first tab and the first electrode according to this embodiment. [Figure 6] This is a cross-sectional view showing the configuration of the second tab and the second electrode according to this embodiment. [Figure 7] This is a front view of the first current collector with the winding unwound according to this embodiment. [Figure 8] This is a cross-sectional view showing the configuration of the expandable portion of this embodiment. [Figure 9] This is a cross-sectional view showing the configuration of the expandable portion according to a first modified example of this embodiment. [Figure 10] This is a cross-sectional view showing the configuration of the expandable portion according to a second modification of this embodiment. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described with reference to the drawings. In the drawings referred to below, the same or equivalent components are given the same number.

[0010] Figure 1 is a perspective view showing the configuration of an energy storage device 1 including an energy storage cell 100 in an embodiment of the present disclosure. The energy storage device 1 is mounted, for example, on a vehicle (not shown). Examples of vehicles include hybrid electric vehicles, plug-in hybrid electric vehicles, and battery electric vehicles. The energy storage device 1 may also be installed in electrical equipment other than electric vehicles (for example, a stationary energy storage device).

[0011] In this specification, the X, Y, and Z directions are mutually orthogonal directions. For example, the X and Y directions may be the front-to-back and left-to-right directions, respectively, when the energy storage device 1 is mounted on an electric vehicle. The Z direction may also be the up-and-down direction. Specifically, the Z1 and Z2 directions may be upward and downward, respectively.

[0012] The energy storage device 1 is attached to a frame member 2 located at the bottom of the vehicle. The frame member 2 is formed in a roughly rectangular cylindrical shape that surrounds the energy storage device 1.

[0013] The energy storage device 1 comprises multiple energy storage stacks 3. Each energy storage stack 3 is formed in the shape of a rectangular parallelepiped, elongated in the Y direction. The multiple energy storage stacks 3 are arranged in a line along the X direction. Each energy storage stack 3 contains multiple energy storage cells 100 arranged in the Y direction. Note that in Figure 1, for simplification, only two energy storage stacks 3 are shown, and only three energy storage cells 100 in each energy storage stack 3 are shown.

[0014] FIG. 2 is a perspective view showing the power storage cell 100 according to the present embodiment. As shown in FIG. 2, the power storage cell 100 is a so-called rectangular battery. The power storage cell 100 is a secondary battery configured to be capable of charge and discharge. The power storage cell 100 may be a secondary battery such as a lithium-ion battery or a nickel-hydrogen battery. The power storage cell 100 can be used, for example, as a cell included in a power storage module mounted on an electric vehicle.

[0015] The power storage cell 100 includes an electrode body 10, a case 20, a first external terminal 30A, a second external terminal 30B, a first terminal support portion 40A, and a second terminal support portion 40B. In FIG. 2, the electrode body 10 is schematically shown by a broken line. The electrode body 10 is an example of the "wound electrode body" of the present disclosure.

[0016] The case 20 has conductivity. The conductive portion of the case 20 is made of a metal such as aluminum. The case 20 houses the electrode body 10. The case 20 also houses an electrolyte solution (not shown).

[0017] The case 20 includes a case body 21 and a lid 22. The case body 21 includes a bottom wall 210 and a peripheral wall 211 standing up from the bottom wall 210.

[0018] The lid 22 includes a lid body 220 and an insulating cover 221. The lid body 220 is joined to the peripheral wall 211 by welding or the like so as to close the opening of the peripheral wall 211.

[0019] The first external terminal 30A and the second external terminal 30B are provided so as to be exposed to the outside in the power storage cell 100. In the present embodiment, the first external terminal 30A is a positive electrode terminal, and the second external terminal 30B is a negative electrode terminal. The first external terminal 30A and the second external terminal 30B are arranged side by side in the X direction.

[0020] The first terminal support portion 40A is locked to the lid body 220. The first terminal support portion 40A supports the first external terminal 30A from the outer circumference side of the first external terminal 30A. The second terminal support portion 40B is locked to the lid body 220. The second terminal support portion 40B supports the second external terminal 30B from the outer circumference side of the second external terminal 30B.

[0021] Figure 3 is an exploded perspective view of the energy storage cell 100 according to this embodiment. The energy storage cell 100 further comprises a first connecting member 50A, a second connecting member 50B, a first sealing ring 60A, a second sealing ring 60B, an insulating member 70, and a fuse protection unit 101.

[0022] The bottom wall 210 includes a bottom body 212, an outer protective film 213, and an inner protective film 214. The peripheral wall 211 rises from the bottom body 212. A pressure relief valve SV is provided in the bottom body 212. The outer protective film 213 covers the pressure relief valve SV from the outside. The inner protective film 214 covers the pressure relief valve SV from the inside. The bottom body 212 and the pressure relief valve SV are made of a metal such as aluminum.

[0023] An opening is formed at the upper end of the peripheral wall 211. The peripheral wall 211 has a substantially rectangular outer shape when viewed from the direction of the opening. The opening and the bottom wall 210 are aligned in the Z direction. The opening is located on the Z1 side of the bottom wall 210. The Z direction may be the height direction or vertical direction of the energy storage cell 100. The peripheral wall 211 is made of a metal such as aluminum.

[0024] The lid 22 further includes a sealing plug 222 and a plug cover 223. The lid body 220 has a first connecting hole 224A, a second connecting hole 224B, and an electrolyte injection hole 225. The electrolyte injection hole 225 is a through hole for injecting electrolyte into the case body 21 during the manufacturing process of the energy storage cell 100.

[0025] The sealing plug 222 seals the injection hole 225. The plug cover 223 covers the injection hole 225 and the sealing plug 222. The insulating cover 221 covers the injection hole 225, the sealing plug 222, and the plug cover 223.

[0026] The first connecting member 50A and the second connecting member 50B are conductive. At least a portion of the first connecting member 50A and the second connecting member 50B are located inside the case 20. Each of the first connecting member 50A and the second connecting member 50B is positioned opposite the electrode body 10 in the Z direction. Each of the first connecting member 50A and the second connecting member 50B is positioned on the Z1 side of the electrode body 10.

[0027] The first external terminal 30A or the first connecting member 50A is inserted through the first connecting hole 224A. The first external terminal 30A and the first connecting member 50A are joined to each other. The first connecting member 50A is joined to the electrode body 10. As a result, the first external terminal 30A is electrically connected to the electrode body 10.

[0028] The second external terminal 30B or the second connecting member 50B is inserted through the second connecting hole 224B. The second external terminal 30B and the second connecting member 50B are joined to each other. The second connecting member 50B is joined to the electrode body 10. As a result, the second external terminal 30B is electrically connected to the electrode body 10.

[0029] The first seal ring 60A is provided along the first connecting hole 224A. The first seal ring 60A is provided in the gap between the lid body 220 and the first external terminal 30A, and seals this gap. The second seal ring 60B is provided along the second connecting hole 224B. The second seal ring 60B is provided in the gap between the lid body 220 and the second external terminal 30B, and seals this gap. The first seal ring 60A and the second seal ring 60B have electrical insulating properties.

[0030] The first terminal support portion 40A includes a first locking ring 41A and a first covering ring 42A. The first locking ring 41A extends in an annular shape to surround the first connecting hole 224A and is directly locked to the lid body 220. The first covering ring 42A covers the first locking ring 41A. The first locking ring 41A supports the first external terminal 30A via the first covering ring 42A. The first covering ring 42A is made of a resin material that is electrically insulating or has relatively weak conductivity.

[0031] The second terminal support portion 40B includes a second locking ring 41B and a second covering ring 42B. The second locking ring 41B extends in an annular shape to surround the second connecting hole 224B and is directly locked to the lid body 220. The second covering ring 42B covers the second locking ring 41B. The second locking ring 41B supports the second external terminal 30B via the second covering ring 42B. The second covering ring 42B is made of an electrically insulating resin material.

[0032] The insulating member 70 has electrical insulating properties. The insulating member 70 is placed between the electrode body 10 and the case 20. The insulating member 70 electrically insulates the electrode body 10 and the case 20 from each other. The insulating member 70 includes an insulating bracket 71, a circumferential insulating portion 72, a bottom insulating portion 73, and adhesive tape 74.

[0033] The insulating bracket 71 is positioned between the electrode body 10 and the lid body 220. The insulating bracket 71 is relatively rigid and is in contact with both the electrode body 10 and the lid body 220. As a result, the electrode body 10 is fixed to the case 20 in the Z direction.

[0034] The circumferential insulating portion 72 is positioned between the electrode body 10 and the circumferential wall 211. The electrode body 10 is made of a film-like material.

[0035] The bottom insulating portion 73 is positioned between the electrode body 10 and the bottom wall 210. The bottom insulating portion 73 is made of a film-like material. The bottom insulating portion 73 is fixed (adhered) to the case 20 (bottom wall 210) by adhesive tape 74.

[0036] The energy storage cell 100 according to this embodiment includes a plurality of electrode bodies 10. The energy storage cell 100 of this embodiment includes two electrode bodies 10. These electrode bodies 10 are arranged in the Y direction. The circumferential insulating portion 72 may integrally cover the plurality of electrode bodies 10 so that these electrode bodies 10 are fixed to each other.

[0037] Each of the multiple electrode bodies 10 is provided with at least one first tab 90A and at least one second tab 90B. In this embodiment, each of the multiple electrode bodies 10 is provided with multiple first tabs 90A and multiple second tabs 90B. Each first tab 90A electrically connects the first electrode 10A (described later) and the first connecting member 50A. Each second tab 90B electrically connects the second electrode 10B (described later) and the second connecting member 50B.

[0038] Multiple first tabs 90A are arranged so as to be aligned with each other in the Y direction. Multiple first tabs 90A are joined to each other, for example by ultrasonic welding. Multiple first tabs 90A are joined to the first connecting member 50A, for example by ultrasonic welding. Multiple second tabs 90B are arranged so as to be aligned with each other in the Y direction. Multiple second tabs 90B are joined to each other, for example by ultrasonic welding. Multiple second tabs 90B are joined to the second connecting member 50B, for example by ultrasonic welding.

[0039] Figure 4 is a cross-sectional view of the electrode body 10 in the XY plane. The electrode body 10 includes a first electrode 10A, a second electrode 10B, a separator 10C, and a tape member 10D. The electrode body 10 is wound such that the first electrode 10A, the second electrode 10B, and the separator 10C surround the winding axis α. Thus, in this embodiment, the electrode body 10 is a so-called wound electrode body. The first electrode 10A is an example of the "electrode sheet" of this disclosure.

[0040] The first electrode 10A and the second electrode 10B have a sheet-like outer shape. The electrode body 10 is composed of a group of electrode plates in which the first electrode 10A and the second electrode 10B are wound around one or more separators 10C.

[0041] In this embodiment, the first electrode 10A is the positive electrode and the second electrode 10B is the negative electrode. However, the first electrode 10A may be the negative electrode and the second electrode 10B may be the positive electrode.

[0042] The separator 10C is provided between the first electrode 10A and the second electrode 10B. The separator 10C separates the first electrode 10A and the second electrode 10B while allowing ions to move between them. The ions are, for example, lithium ions. The separator 10C has electrical insulating properties.

[0043] Of the first electrode 10A, the second electrode 10B, and the separator 10C, the separator 10C is located on the innermost side with respect to the winding axis α. Also, of the first electrode 10A, the second electrode 10B, and the separator 10C, the separator 10C is located on the outermost side with respect to the winding axis α. The outer edge of the separator 10C in the winding direction is fixed by a tape member 10D placed on the outer surface of the separator 10C.

[0044] The first electrode 10A includes a first current collector 11A and a first active material layer 12A. The second electrode 10B includes a second current collector 11B and a second active material layer 12B. The first current collector 11A and the first active material layer 12A are examples of the "conductive sheet" and "electrode active material layer" of this disclosure, respectively.

[0045] As shown in Figure 4, the electrode body 10 includes at least one bent portion 10E and at least one straight portion 10F. In this embodiment, there are two bent portions 10E and two straight portions 10F on the electrode body 10.

[0046] The bent portions 10E are provided at the X1-side end and the X2-side end of the electrode body 10. Each of the two bent portions 10E is formed in a semicircular shape (curved). Each of the two straight portions 10F connects the X1-side bent portion 10E and the X2-side bent portion 10E. One of the two straight portions 10F is positioned on the Y1 side with respect to the winding axis α. The other of the two straight portions 10F is positioned on the Y2 side with respect to the winding axis α.

[0047] Figure 5 is a cross-sectional view of the first electrode 10A and the first tab 90A. The first current collector 11A includes an insulating support layer 110, a first conductive layer 111, and a second conductive layer 112. The first electrode 10A further includes a protective portion 13. The first conductive layer 111 is an example of the "electrode layer" and "inner electrode film" of this disclosure. The second conductive layer 112 is also an example of the "electrode layer" and "outer electrode film" of this disclosure.

[0048] The first conductive layer 111 has a surface 111a, which is the surface opposite to the insulating support layer 110. The second conductive layer 112 has a surface 112a, which is the surface opposite to the insulating support layer 110. The first active material layer 12A is formed on each of the surfaces 111a and 112a. Note that each of the surfaces 111a and 112a is an example of a "surface" in this disclosure.

[0049] The insulating support layer 110 has an inner surface 110a and an outer surface 110b. The inner surface 110a is the surface of the insulating support layer 110 located on the winding axis α side. The surface located on the winding axis α side means the surface that is positioned facing the winding axis α side. The outer surface 110b is the surface located on the opposite side from the inner surface 110a (winding axis α).

[0050] The insulating support layer 110 is made of an electrically insulating resin composition. For example, the insulating support layer 110 is made of a resin composition containing a polyester resin. The polyester resin is preferably polyethylene terephthalate, for example. This makes it possible to increase the rigidity of the first current collector 11A while maintaining the electrical insulation properties of the insulating support layer 110. Consequently, the insulating support layer 110 can be made relatively thin. The orthogonal direction DO that intersects (is perpendicular to) the thickness direction DT of the insulating support layer 110 is approximately parallel to the Z direction.

[0051] The first conductive layer 111 is formed on the inner surface 110a. The first conductive layer 111 may be provided over the entire inner surface 110a of the insulating support layer 110.

[0052] The second conductive layer 112 is formed on the outer surface 110b. The second conductive layer 112 may be provided over the entire outer surface 110b of the insulating support layer 110.

[0053] Each of the first conductive layer 111 and the second conductive layer 112 is made of a metal layer. Each of the first conductive layer 111 and the second conductive layer 112 is made of a metal containing aluminum. As a result, the first current collector 11A can be suitably used as a positive electrode current collector. The first current collector 11A may also be a negative electrode current collector, and the first conductive layer 111 and the second conductive layer 112 may be made of a metal containing copper.

[0054] Each of the multiple first tabs 90A is joined to the first conductive layer 111 and the second conductive layer 112, for example, by ultrasonic welding. Each of the multiple first tabs 90A extends from the insulating support layer 110 toward Z1.

[0055] Each of the multiple first tabs 90A includes a first foil portion 91 and a second foil portion 92. The first foil portion 91 is located on the opposite side of the insulating support layer 110 when viewed from the first conductive layer 111. The first foil portion 91 is bonded to the first conductive layer 111. The first foil portion 91 is bonded to the first connecting member 50A. The second foil portion 92 is located on the opposite side of the insulating support layer 110 when viewed from the second conductive layer 112. The second foil portion 92 is bonded to the second conductive layer 112.

[0056] The first foil portion 91 includes a lower portion 91a and an upper portion 91b. The lower portion 91a is the part of the first foil portion 91 that is positioned on the first current collector 11A. The upper portion 91b is the part that protrudes from the lower portion 91a toward the Z1 side (the first connecting member 50A side).

[0057] The second foil portion 92 includes a lower portion 92a and an upper portion 92b. The lower portion 92a is the part of the second foil portion 92 that is positioned on the first current collector 11A. The upper portion 92b is the part that protrudes from the lower portion 92a toward the Z1 side (towards the first connecting member 50A).

[0058] The upper portion 91b is joined to the upper portion 92b. Specifically, the upper portion 91b and the upper portion 92b are joined at the joint portion 93 on the Z1 side of the first current collector 11A, for example by ultrasonic welding.

[0059] The first foil portion 91 (upper portion 91b) extends further toward Z1 than the upper end portion 92c (Z1 side end) of the second foil portion 92 (upper portion 92b). The joint portion 93 is the portion where the upper portion 92b and the Z2 side base portion of the upper portion 91b are joined. The joint portion 93 extends toward Z1 from, for example, the upper end portion 10G of the electrode body 10. The upper end portion 10G of the electrode body 10 is the upper end portion of the separator 10C (Figure 4). The lower end portion of the joint portion 93 may be located, for example, toward Z1 or Z2 than the upper end portion 10G.

[0060] As described above, the length of the first foil portion 91 in the orthogonal direction DO (Z direction) perpendicular to the thickness direction DT is longer than the length of the second foil portion 92 in the orthogonal direction DO. However, the configuration of the first tab 90A is not limited to this. The length of the second foil portion 92 in the orthogonal direction DO may be longer than the length of the first foil portion 91 in the orthogonal direction DO. Furthermore, the second foil portion 92 may be joined to the first connecting member 50A, while the first foil portion 91 may not be joined to the first connecting member 50A.

[0061] The first active material layer 12A includes an inner active material layer 121A and an outer active material layer 122A. The inner active material layer 121A is formed on the first conductive layer 111 (surface 111a). The outer active material layer 122A is laminated on the second conductive layer 112 (surface 112a).

[0062] The upper edge of the first active material layer 12A is separated from each of the multiple first tabs 90A. Specifically, the upper edge of the inner active material layer 121A is separated from each of the first foil portions 91 of the multiple first tabs 90A. The upper edge of the outer active material layer 122A is separated from each of the second foil portions 92 of the multiple first tabs 90A.

[0063] The separator 10C is laminated on the first active material layer 12A in the radial direction centered on the winding axis α (Figure 4). The separator 10C is laminated on the inner active material layer 121A in the same radial direction. The separator 10C is also laminated on the outer active material layer 122A in the same radial direction.

[0064] The protective part 13 has electrical insulating properties and is made of, for example, ceramic. The protective part 13 covers the upper part of the first active material layer 12A. The protective part 13 further covers the first current collector 11A between the first tab 90A and the first active material layer 12A.

[0065] The protective portion 13 includes an inner protective portion 131 and an outer protective portion 132. The inner protective portion 131 covers the upper part of the inner active material layer 121A. The inner protective portion 131 covers the first conductive layer 111 (surface 111a) between the first foil portion 91 and the inner active material layer 121A. The outer protective portion 132 covers the upper part of the outer active material layer 122A. The outer protective portion 132 covers the second conductive layer 112 (surface 112a) between the second foil portion 92 and the outer active material layer 122A.

[0066] Figure 6 is a cross-sectional view of the second electrode 10B. The second electrode 10B is laminated on the first active material layer 12A (Figure 4) via the separator 10C (Figure 4) in the radial direction.

[0067] The second electrode 10B includes a second current collector 11B and a second active material layer 12B. The second current collector 11B includes a conductive support portion 113 and a plurality of second tabs 90B. The conductive support portion 113 extends along the orthogonal direction DO (Z direction). The plurality of second tabs 90B extend from the upper end of the conductive support portion 113. The plurality of second tabs 90B are joined to each other by ultrasonic welding and are also joined to the second connecting member 50B.

[0068] The multiple second tabs 90B and conductive support portion 113 are made of an integral material, for example, metal foil. In this embodiment, the multiple second tabs 90B and conductive support portion 113 are made of a metal including copper, for example. This allows the second current collector 11B to be suitably used as a negative electrode current collector. If the first current collector 11A is a negative electrode current collector, the multiple second tabs 90B and conductive support portion 113 may be made of a metal including aluminum.

[0069] The second active material layer 12B is laminated on both sides of the conductive support portion 113 of the second current collector 11B. In this embodiment, since the second electrode 10B is the negative electrode, the Z1-side edge of the second active material layer 12B is located Z1 closer to the Z1 side than the Z1-side edge of the first active material layer 12A. The Z2-side edge of the second active material layer 12B is located Z2 closer to the Z2 side than the Z2-side edge of the first active material layer 12A.

[0070] Figure 7 is a front view of the first current collector 11A after the winding has been unwound. The first current collector 11A is formed to be elongated in the winding direction. One end of the first current collector 11A in the winding direction is the inner circumference end of the first current collector 11A. The other end of the first current collector 11A in the winding direction is the outer circumference end of the first current collector 11A.

[0071] The first current collector 11A has a bent portion 11E and a straight portion 11F. The bent portion 11E corresponds to the bent portion 10E (Figure 4) of the electrode body 10. Each bent portion 10E includes multiple bent portions 11E. The straight portion 11F corresponds to the straight portion 10F (Figure 4) of the electrode body 10. Each straight portion 10F includes multiple straight portions 11F.

[0072] The curved portions 11E and straight portions 11F are arranged alternately in the winding direction. Between adjacent curved portions 11E and straight portions 11F in the winding direction, the length L1 of the curved portion 11E in the winding direction is smaller than the length L2 of the straight portion 11F in the winding direction. However, between adjacent curved portions 11E and straight portions 11F in the winding direction, the length L1 of the curved portion 11E may be greater than or equal to the length L2 of the straight portion 11F.

[0073] In conventional energy storage cells, for example, when the bending rigidity of the electrode sheet is relatively high, it can be difficult to fold the electrode sheet compactly. In this case, the case housing the electrode body may become larger.

[0074] In this embodiment, the bent portion 11E is formed with an expandable portion 80 that can expand and contract in the winding direction of the electrode body 10. This allows the first current collector 11A to be easily expanded and contracted at the bent portion 10E of the electrode body 10. The expandable portion 80 is formed in each bent portion 11E.

[0075] Specifically, the expandable portion 80 includes a plurality of protrusions 81. The plurality of protrusions 81 are arranged at intervals from each other in the winding direction. Recesses 82 are formed between adjacent protrusions 81 in the winding direction. The plurality of recesses 82 are arranged in the winding direction. In this way, the expandable portion 80 includes the protrusions and recesses (bellows portion) formed on the first current collector 11A. Note that in Figure 7, the area where the protrusions 81 are provided is shaded for clarity.

[0076] Each protrusion 81 extends in the Z direction. Specifically, each protrusion 81 extends from the Z1-side end 11G of the first current collector 11A to the Z2-side end 11H of the first current collector 11A. Therefore, the recess 82 has a groove shape that extends in the Z direction from end 11G to end 11H.

[0077] Furthermore, the expandable portion 80 is also formed in the straight portion 11F. The expandable portion 80 is formed in each straight portion 11F. This makes it possible to suppress the tearing (damage) of the straight portion 11F even when tensile stress is applied to it. In addition, since the configuration of the bent portion 11E and the straight portion 11F can be standardized, the manufacturing of the first current collector 11A can be made easier (simplified).

[0078] Figure 8 is a cross-sectional view of the bent portion 11E along the line VIII-VIII in Figure 7. As shown in Figure 8, the expandable portion 80 is formed in the insulating support layer 110. This allows the insulating support layer 110 to be easily bent even if its bending rigidity is relatively high. Note that in Figure 8, for simplification, components other than the insulating support layer 110, the first conductive layer 111, and the second conductive layer 112 are omitted from the illustration.

[0079] Specifically, the insulating support layer 110 (expandable portion 80) includes a base portion 83 and a plurality of protrusions 81. The plurality of protrusions 81 include a plurality of protrusions 81a and a plurality of protrusions 81b. Each of the plurality of protrusions 81a and the plurality of protrusions 81b is integrally formed with the base portion 83.

[0080] Multiple protrusions 81a project from the base portion 83 in the direction toward the winding axis α (Figure 4) (towards the inner diameter). The multiple protrusions 81a are arranged with spacing between them in the winding direction.

[0081] Multiple protrusions 81b project from the base portion 83 in the direction opposite to the winding axis α (towards the outer diameter). The multiple protrusions 81b are arranged with spacing between them in the winding direction.

[0082] Each of the multiple recesses 82 includes a plurality of recesses 82a and a plurality of recesses 82b. Each of the plurality of recesses 82a is formed between convex portions 81a aligned in the winding direction. Each of the plurality of recesses 82b is formed between convex portions 81b aligned in the winding direction.

[0083] With this configuration, when winding the first current collector 11A, the insulating support layer 110 can be deformed so that the protrusions 81a aligned in the winding direction are brought closer together, and the insulating support layer 110 can be deformed so that the protrusions 81b aligned in the winding direction are moved further apart. Therefore, the insulating support layer 110 can be deformed so that its inner surface 110a is shortened, and the insulating support layer 110 can be deformed so that its outer surface 110b is stretched. As a result, the bent portion 11E of the first current collector 11A can be easily bent.

[0084] Each of the multiple protrusions 81b is positioned radially opposite to the protrusion 81a. Therefore, each of the multiple recesses 82b is positioned radially opposite to the recess 82a. This allows the circumferential positions where deformation occurs to be aligned on both the inner surface 110a and the outer surface 110b. As a result, the first current collector 11A can be bent more easily. Note that the protrusions 81a (recesses 82a) that each protrusion 81b (recess 82b) faces radially are different from each other.

[0085] Each protrusion 81a has a trapezoidal shape in the cross-sectional view shown in Figure 8. Specifically, each protrusion 81a has a flat surface 81c, an inclined surface 81d, and an inclined surface 81e. The flat surface 81c connects the inner diameter end of the inclined surface 81d to the inner diameter end of the inclined surface 81e. The flat surface 81c extends parallel to the base portion 83. The inclined surface 81d is inclined so as it approaches the inclined surface 81e as it approaches the inner diameter. The inclined surface 81e is inclined so as it approaches the inclined surface 81d as it approaches the inner diameter. Note that each of the inclined surfaces 81d and 81e may extend in a planar shape (i.e., they may be flat inclined surfaces), or they may be curved so as to be convex toward the inner diameter.

[0086] Each protrusion 81b has a trapezoidal shape in the cross-sectional view shown in Figure 8. Specifically, each protrusion 81b has a flat surface 81f, an inclined surface 81g, and an inclined surface 81h. The flat surface 81f connects the outer diameter end of the inclined surface 81g to the outer diameter end of the inclined surface 81h. The flat surface 81f extends parallel to the base portion 83. The inclined surface 81g is inclined so as it moves toward the outer diameter side it approaches the inclined surface 81h side. The inclined surface 81h is inclined so as it moves toward the outer diameter side it approaches the inclined surface 81g side. Note that each of the inclined surfaces 81g and 81h may extend in a planar shape, or they may be curved so as to be convex toward the outer diameter side, for example.

[0087] The base portion 83 has a thickness t1 in the radial direction. The thickness t1 is constant in the circumferential direction of the first current collector 11A. Each protrusion 81a has a thickness t2 in the radial direction. The thickness t2 gradually increases toward the inner diameter. The maximum value of the thickness t2 (i.e., the amount of protrusion of the protrusion 81a) is greater than the thickness t1 of the base portion 83. Each protrusion 81b has a thickness t3 in the radial direction. The thickness t3 gradually increases toward the outer diameter. The maximum value of the thickness t3 (i.e., the amount of protrusion of the protrusion 81b) is greater than the thickness t1 of the base portion 83. Note that the maximum values ​​of thickness t2 and thickness t3 may be equal. Also, at least one of the maximum values ​​of thickness t2 and thickness t3 may be less than or equal to the thickness t1 of the base portion 83.

[0088] The first conductive layer 111 has a thickness t11 in the radial direction. The second conductive layer 112 has a thickness t12 in the radial direction. Thicknesses t11 and t12 may be equal. Each of thicknesses t11 and t12 is constant in the circumferential direction. Each of thicknesses t11 and t12 is sufficiently smaller than, for example, the thickness t1 of the base portion 83. Therefore, the recess 82a is not filled by the first conductive layer 111 (a space remains). Similarly, the recess 82b is not filled by the second conductive layer 112 (a space remains).

[0089] The recess 82a is a space defined by one inclined surface 81d of two convex portions 81a aligned in the winding direction, the other inclined surface 81e of two convex portions 81a aligned in the winding direction, and the bottom surface 82c. The bottom surface 82c connects the outer diameter end of one inclined surface 81d to the outer diameter end of the other inclined surface 81e. The first conductive layer 111 is formed on each of the flat surface 81c, inclined surface 81d, inclined surface 81e, and bottom surface 82c of the convex portion 81a.

[0090] The recess 82b is a space defined by one inclined surface 81g of two convex portions 81b aligned in the winding direction, the other inclined surface 81h of two convex portions 81b aligned in the winding direction, and the bottom surface 82d. The bottom surface 82d connects the inner diameter end of the one inclined surface 81g to the inner diameter end of the other inclined surface 81h. The second conductive layer 112 is formed on the flat surface 81f, the inclined surface 81g, the inclined surface 81h, and the bottom surface 82d of the convex portion 81b.

[0091] As described above, in the above embodiment, the bent portion 11E has an expandable portion 80 that can expand and contract in the winding direction of the electrode body 10. This allows the bent portion 11E to be bent while the expandable portion 80 is expanded and contracted. As a result, the bent portion 10E of the electrode body 10, including the bent portion 11E, can be easily bent, so the electrode body 10 can be bent (wound) compactly. This prevents the case housing the electrode body 10 from becoming larger. In addition, since the electrode body 10 is easier to bend, it is possible to prevent the formation of dead space in the case 20.

[0092] <Variation> Figure 9 shows a cross-sectional view of an expandable portion 380, which is a first modified example of the expandable portion 80 of the above embodiment. The expandable portion 380 is formed in the bent portion 311E corresponding to the bent portion of the electrode body, similar to the above embodiment. The expandable portion 380 may also be formed in the straight portion corresponding to the straight portion of the electrode body, similar to the above embodiment.

[0093] In the expandable portion 380, the convex portion 81a and the concave portion 82b are arranged radially, and the concave portion 82a and the convex portion 81b are arranged radially. In other words, in the expandable portion 380, the convex portion 81a and the convex portion 81b are arranged alternately along the winding direction. This makes it possible to make the radial thickness of the insulating support layer 310 uniform in the circumferential direction of the electrode body.

[0094] Figure 10 shows a cross-sectional view of an expandable portion 480, which is a second modified example of the expandable portion 80 of the above embodiment. The expandable portion 480 is formed in the bent portion 411E corresponding to the bent portion of the electrode body, similar to the above embodiment. The expandable portion 480 may also be formed in the straight portion corresponding to the straight portion of the electrode body, similar to the above embodiment.

[0095] The expandable portion 480 (insulating support layer 410) has at least one through-hole 481 that connects the first conductive layer 111 and the second conductive layer 112. In the example shown in Figure 10, multiple through-holes 481 are arranged in the winding direction.

[0096] A conductive portion 482 is formed in each of the multiple through holes 481. The conductive portion 482 is formed by filling the through hole 481 with a conductive material (for example, aluminum).

[0097] This allows the conductive portion 482 to connect the first conductive layer 111 and the second conductive layer 112 electrically. As a result, the second foil portion 92 (Figure 5) can be omitted.

[0098] Each through-hole 481 extends radially in the electrode body. Specifically, each through-hole 481 is formed at a position that connects radially opposing bottom surfaces 82c and bottom surface 82d. Alternatively, in addition to the through-holes 481, for example, through-holes may be formed at a position that connects flat surfaces 81c and flat surfaces 81f.

[0099] Note that the configuration of the through-hole 481 and conductive part 482 shown in Figure 10 may also be applied to the configuration shown in Figure 9.

[0100] In the above embodiment, an example is shown in which an expandable portion 80 is formed on the insulating support layer 110 of the first electrode 10A, but the disclosure is not limited thereto. For example, instead of / in addition to the first electrode 10A, an expandable portion may be formed on the conductive support portion 113 (second tab 90B) of the second electrode 10B.

[0101] In the above embodiment, an example was shown in which the electrode body 10 includes a straight portion 10F, but the disclosure is not limited thereto. The electrode body may have a cylindrical shape that does not include a straight portion. In this case, bent portions are formed at all positions in the circumferential direction of the electrode body.

[0102] In the above embodiment, an example was shown in which the expandable portion 80 is formed on the straight portion 11F, but the disclosure is not limited thereto. The expandable portion 80 may be formed only on the bent portion 11E. Alternatively, the expandable portion 80 may be formed only on a portion of the bent portion 11E with a relatively high curvature.

[0103] In the above embodiment, an example was shown in which the protrusion 81 protrudes in the direction toward the winding axis α from the base portion 83 and in the direction toward the opposite side of the winding axis α from the base portion 83, but the present disclosure is not limited thereto. The protrusion 81 may protrude in only one of the directions toward the winding axis α from the base portion 83 and the direction toward the opposite side of the winding axis α from the base portion 83.

[0104] In the above embodiment, an example was shown in which the expandable portion 80 is formed by the uneven portion (bellows portion) of the first current collector 11A (conductive sheet), but the disclosure is not limited thereto. For example, at least the bent portion of the conductive sheet may include an expandable portion formed of a highly elastic material.

[0105] The configurations of each of the above embodiments and each of the modified examples may be combined with each other. It should be noted that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of this disclosure is defined by the claims rather than the description of the embodiments above, and includes all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0106] 10 Electrode body (winding electrode body), 10A First electrode (electrode sheet), 10E Bent section, 10F Straight section, 11A First current collector (conductive sheet), 11E, 311E, 411E Bent section, 11F Straight section, 12A First active material layer (electrode active material layer), 20 Case, 80, 380, 480 Expandable section, 81, 81a, 81b Protruding section, 83 Base section, 100 Energy storage cell, 110, 310, 410 Insulating support layer, 110a Inner surface, 110b Outer surface, 111 First conductive layer (electrode layer) (inner electrode film), 111a, 112a Surface, 112 Second conductive layer (electrode layer) (outer electrode film), 481 Through hole, 482 Conductive section, α Winding axis.

Claims

1. A wound electrode body in which an electrode sheet is wound around the winding axis, The system comprises a case for housing the wound electrode body, The electrode sheet is A conductive sheet and The conductive sheet includes an electrode active material layer formed on the surface of the conductive sheet, The wound electrode body includes at least one bent portion, The conductive sheet has a bent portion corresponding to the at least one bent portion, A storage cell in which an expandable portion is formed in the bent portion, which is expandable and contractible in the winding direction of the wound electrode body.

2. The aforementioned expandable portion is The base unit and It includes a plurality of protrusions projecting in at least one direction toward the winding axis from the base portion and toward the opposite direction from the winding axis from the base portion, The energy storage cell according to claim 1, wherein the plurality of protrusions are arranged at intervals from each other in the winding direction.

3. The at least one bent portion includes a plurality of bent portions, The wound electrode body further includes straight sections that connect the plurality of bent sections, The conductive sheet further has a straight portion corresponding to the straight portion, The energy storage cell according to claim 1 or 2, wherein the expandable portion is formed in the straight portion.

4. The conductive sheet is Insulating support layer, The insulating support layer has an electrode layer formed thereon, The energy storage cell according to claim 1 or 2, wherein the expandable portion is formed in the insulating support layer.

5. The aforementioned insulating support layer is The inner surface located on the winding axis side, Includes an outer surface located on the opposite side of the inner surface, The electrode layer is The inner electrode film formed on the inner surface, The outer electrode film formed on the outer surface includes, The expandable portion has through holes that connect the inner electrode film and the outer electrode film. The energy storage cell according to claim 4, wherein a conductive portion is formed in the through hole.

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