Wound electrode assembly

Abstract

The invention provides a wound electrode assembly. A wound electrode body in which a positive electrode and a negative electrode are wound in a flat shape with a separator interposed therebetween, the wound electrode body having a pair of flat portions facing each other with a winding center therebetween and a pair of bent portions connecting end portions of the pair of flat portions to each other, the positive electrode including a first base material in which a first metal foil and a first resin member are alternately joined in a winding direction of the wound electrode body, and the negative electrode including a second base material in which a second metal foil and a second resin member are alternately joined in a winding direction of the wound electrode body. The negative electrode includes a second base material in which a second metal foil and a second resin member are alternately joined in the winding direction, the first metal foil and the second metal foil are alternately arranged in a direction in which the pair of flat portions face each other in each of the pair of flat portions, and the first metal foil and the second metal foil are alternately arranged in a direction in which the pair of flat portions face each other in each of the pair of bent portions. The first resin members and the second resin members are alternately arranged in the radial direction of the wound electrode body.

Description

Technical Field

[0001] This disclosure relates to wound electrode bodies. Background Technology

[0002] As a conventional electrode, Japanese Patent Application Publication No. 2016-042433 discloses a wound electrode in which a separator is provided between a positive electrode having a first metal foil and a positive active material layer formed on the first metal foil and a negative electrode having a second metal foil and a negative active material layer formed on the second metal foil, thereby winding the positive electrode and the negative electrode together. Summary of the Invention

[0003] The winding electrode body forms a pair of flat portions facing each other with the winding center, and a pair of curved portions connecting the ends of the pair of flat portions to each other. In the winding electrode, the pair of curved portions are maintained in a curved state, and are subjected to higher stress compared to the pair of flat portions.

[0004] This disclosure is made in view of the aforementioned problems, and the purpose of this disclosure is to provide a wound electrode body capable of suppressing breakage at the bend.

[0005] The wound electrode body according to this disclosure is a wound electrode body in which a positive electrode and a negative electrode are wound into a flat shape with a separator between them, and has a pair of flat portions facing each other with their winding centers sandwiched between them and a pair of curved portions connecting the ends of the pair of flat portions to each other. In this wound electrode body, the positive electrode comprises a first substrate formed by alternately bonding a first metal foil and a first resin member along the winding direction of the wound electrode body. The negative electrode comprises a second substrate formed by alternately bonding a second metal foil and a second resin member along the winding direction. In each of the pair of flat portions, the first metal foil and the second metal foil are alternately arranged in the direction opposite to the pair of flat portions. In each of the pair of curved portions, the first resin member and the second resin member are alternately arranged in the radial direction of the wound electrode body.

[0006] According to the above configuration, in each of the pair of curved portions, the first resin member and the second resin member are alternately arranged in the radial direction of the winding electrode body. Therefore, compared with the configuration in which a metal foil is arranged in the curved portion, the curved portion is easier to bend and deform, and less likely to break. Thus, even when high stress is applied to the curved portion, damage to the curved portion can be suppressed.

[0007] In the wound electrode body based on the present disclosure, in a cross-section of the wound electrode body perpendicular to the winding axis, the first boundary, which serves as the boundary between the first metal foil and the first resin member, may be located at the boundary between the pair of flat portions and the pair of curved portions. Similarly, the second boundary, which serves as the boundary between the second metal foil and the second resin member, may be located at the boundary between the pair of flat portions and the pair of curved portions.

[0008] Based on the above configuration, the entire bending section is made of resin components. This further reduces the risk of breakage in the bending section.

[0009] In the wound electrode body based on the present disclosure, in the cross section perpendicular to the winding axis, at each boundary of the pair of flat portions and the pair of curved portions, the first boundary and the second boundary can be alternately arranged in an arrangement direction in which the first metal foil and the second metal foil are alternately arranged.

[0010] In the above configuration, the curved portion is also entirely made of resin components. This further reduces the risk of breakage in the curved portion.

[0011] In the winding electrode body based on the present disclosure, when the direction orthogonal to the direction opposite to the winding axis and the pair of flat portions is set as the width direction, in the cross section perpendicular to the winding axis, the first boundary and the second boundary can be alternately arranged at each boundary of the pair of flat portions and the pair of curved portions in such a way that they go from the outer peripheral side to the inner peripheral side of the winding electrode body and to the inner side of the width direction.

[0012] Based on the above configuration, the curved portion can be formed into a fan shape, making it easy to deform. Therefore, when stress is applied to the curved portion, breakage of the curved portion can be prevented.

[0013] In the wound electrode body based on the present disclosure, when the direction orthogonal to the direction opposite to the winding axis and the pair of flat portions is set as the width direction, in the cross section perpendicular to the winding axis, the first boundary and the second boundary can be alternately arranged at each boundary of the pair of flat portions and the pair of curved portions in such a way that they go outward from the outer periphery side to the inner periphery side of the wound electrode body and outward from the width direction.

[0014] According to the above configuration, in a pair of flat portions, the proportion (length) of the metal foil disposed on the inner side of the wound electrode body is greater than the proportion (length) of the metal foil disposed on the outer side of the wound electrode body.

[0015] Generally, heat tends to accumulate on the inside of the wound electrode body, but by making the above-described configuration, the proportion of metal foil on the inside of the wound electrode body can be increased, thereby improving heat dissipation.

[0016] In the wound electrode body based on the present disclosure, the thickness of the first resin component may be thinner than the thickness of the first metal foil.

[0017] According to the above configuration, since the thickness of the first resin component is thinner than the thickness of the first metal foil, the bending portion is easy to bend.

[0018] In the wound electrode body based on the present disclosure, the thickness of the second resin component may be thinner than the thickness of the second metal foil.

[0019] According to the above configuration, since the thickness of the second resin component is thinner than the thickness of the second metal foil, the bending portion is easy to bend.

[0020] The foregoing and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description relating to the invention, which is understood in conjunction with the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a perspective view showing the battery of Embodiment 1.

[0022] Figure 2 This is an exploded perspective view of the battery according to Embodiment 1.

[0023] Figure 3 Observe in the direction of the arrow on line III-III Figure 1 The cross-sectional view of the battery shown.

[0024] Figure 4 Observe in the direction of the arrow on line IV-IV. Figure 3 The cross-sectional view shown is of the wound electrode body.

[0025] Figure 5 It is Figure 3 A cross-sectional view of the state after the positive electrode of the wound electrode body has been unwound.

[0026] Figure 6 It is Figure 3 A cross-sectional view of the state after the negative electrode of the wound electrode body has been unwound.

[0027] Figure 7 This is a cross-sectional view of the wound electrode body according to Embodiment 2.

[0028] Figure 8 This is a cross-sectional view of the wound electrode body according to Embodiment 3. Detailed Implementation

[0029] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the embodiments shown below, the same reference numerals are used to label the same or common parts in the drawings, and their description will not be repeated.

[0030] (Implementation Method 1)

[0031] Figure 1 This is a perspective view showing the battery according to Embodiment 1. (Refer to...) Figure 1 The battery 1 of Embodiment 1 will be described.

[0032] like Figure 1 As shown, battery 1 is a so-called prismatic battery. Battery 1 can be a rechargeable secondary battery, such as a lithium-ion battery or a nickel-metal hydride battery. Battery 1 can be used, for example, as a unit included in an energy storage module mounted in an electric vehicle.

[0033] Figure 2 This is an exploded perspective view of the battery according to Embodiment 1. Figure 3 Observe in the direction of the arrow on line III-III Figure 1 A cross-sectional view of the battery.

[0034] like Figures 1-3 As shown, the battery 1 includes multiple wound electrode bodies 10, a housing 20, a first external terminal 30A, a second external terminal 30B, a first connecting member 40A, a second connecting member 40B, a first sealing ring 50A, a second sealing ring 50B, a first terminal support 60A, a second terminal support 60B, an insulating member 70, and a fuse protection part 80. First, the components of the battery 1 other than the wound electrode bodies 10 will be described.

[0035] The housing 20 is conductive. The conductive portion of the housing 20 is made of a metal such as aluminum. The housing 20 houses the wound electrode body 10. The housing 20 also houses an electrolyte (not shown).

[0036] The housing 20 includes a housing body 21 and a cover 22. The housing body 21 includes a bottom wall 21a and a peripheral wall 21b rising from the bottom wall 21a.

[0037] The bottom wall 21a includes a bottom body 21aa, a pressure relief valve 21ab, an outer protective membrane 21ac, and an inner protective membrane 21ad. The peripheral wall 21b rises from the bottom body 21aa. The pressure relief valve 21ab is disposed on the bottom body 21aa. The outer protective membrane 21ac covers the pressure relief valve 21ab from the outside. The inner protective membrane covers the pressure relief valve 21ab from the inside. The bottom body 21aa and the pressure relief valve 21ab are made of metal such as aluminum.

[0038] An opening is formed at the upper end of the peripheral wall 21b. The peripheral wall 21b has a generally rectangular shape when viewed from the opening direction (the normal direction of the opening surface). The opening and the bottom wall 21a are aligned in a first direction D1. The first direction D1 can be the height direction of the battery 1 or the vertical direction. The peripheral wall 21b is made of a metal such as aluminum.

[0039] The cover 22 includes a cover body 22a, a sealing bolt 22b, a bolt cover 22c, and an insulating cover 22d.

[0040] The cover body 22a is joined to the peripheral wall 21b by welding or the like to close the opening of the peripheral wall 21b. A first connecting hole 22aa, a second connecting hole 22ab, and an electrolyte injection hole 22ac are formed in the cover body 22a. The electrolyte injection hole 22ac is a through hole used to inject electrolyte into the casing body 21 during the manufacturing process of the battery 1.

[0041] A sealing plug 22b seals the injection hole 22ac. A plug cover 22c covers the injection hole 22ac and the sealing plug 22b. An insulating cover 22d covers the injection hole 22ac, the sealing plug 22b, and the plug cover 22c.

[0042] The first external terminal 30A and the second external terminal 30B are configured to be exposed to the outside within the battery 1. The first connecting structural member 40A and the second connecting structural member 40B are conductive. At least a portion of the first connecting structural member 40A and the second connecting structural member 40B is disposed inside the housing 20.

[0043] The first external terminal 30A or the first connecting member 40A is inserted into the first connecting hole 22aa. The first external terminal 30A and the first connecting member 40A are engaged with each other. The first connecting member 40A is engaged with the wound electrode body 10. Thus, the first external terminal 30A is electrically connected to the wound electrode body 10.

[0044] The second external terminal 30B or the second connecting member 40B is inserted into the second connecting hole 22ab. The second external terminal 30B and the second connecting member 40B are engaged with each other. The second connecting member 40B is engaged with the wound electrode body 10. Thus, the second external terminal 30B is electrically connected to the wound electrode body 10.

[0045] Furthermore, in this embodiment, the first external terminal 30A is the positive terminal, and the second external terminal 30B is the negative terminal. The first external terminal 30A and the second external terminal 30B are arranged in the second direction D2. The second direction D2 is a direction orthogonal to the first direction D1.

[0046] A first sealing ring 50A is disposed along the first connecting hole 22aa. The first sealing ring 50A is disposed in the gap between the cover body 22a and the first external terminal 30A, sealing the gap. A second sealing ring 50B is disposed along the second connecting hole 22ab. The second sealing ring 50B is disposed in the gap between the cover body 22a and the second external terminal 30B, sealing the gap. The first sealing ring 50A and the second sealing ring 50B are electrically insulating.

[0047] The first terminal support portion 60A is engaged (stopped) to the cover body 22a. The first terminal support portion 60A supports the first external terminal 30A from its outer periphery. The first terminal support portion 60A includes a first locking ring 61A and a first covering ring 62A. The first locking ring 61A extends annularly around the first connecting hole 22aa and is directly engaged with the cover body 22a. The first covering ring 62A covers the first locking ring 61A. The first locking ring 61A supports the first external terminal 30A via the first covering ring 62A. The first covering ring 62A is made of a resin member having electrical insulation or weak conductivity.

[0048] The second terminal support portion 60B is engaged with the cover body 22a. The second terminal support portion 60B supports the second external terminal 30B from its outer periphery. The second terminal support portion 60B includes a second locking ring 61B and a second covering ring 62B. The second locking ring 61B extends annularly around the second connecting hole 22ab and is directly engaged with the cover body 22a. The second covering ring 62B covers the second locking ring 61B. The second locking ring 61B supports the second external terminal 30B via the second covering ring 62B. The second covering ring 62B is made of an electrically insulating resin component.

[0049] The insulating member 70 is electrically insulating. The insulating member 70 is disposed between the plurality of wound electrode bodies 10 and the housing 20. The insulating member 70 electrically insulates the plurality of wound electrode bodies 10 from the housing 20. The insulating member 70 includes an insulating bracket 71, a peripheral insulating portion 72, and a bottom insulating portion 73.

[0050] An insulating bracket 71 is disposed between the plurality of wound electrode bodies 10 and the cover body 22a. The insulating bracket 71 has high rigidity and is in contact with both the wound electrode bodies 10 and the cover body 22a. Thus, the wound electrode bodies 10 are fixed to the housing 20 in the first direction D1.

[0051] The peripheral insulating portion 72 is disposed between the plurality of wound electrode bodies 10 and the peripheral wall 21b. The peripheral insulating portion 72 is composed of a film-like component.

[0052] A bottom insulating portion 73 is disposed between each wound electrode body 10 and the bottom wall 21a. The bottom insulating portion 73 is composed of a film-like component. In this embodiment, the bottom insulating portion 73 is bonded to the wound electrode body 10. Alternatively, the bottom insulating portion 73 may only cover a portion of the bottom surface of the wound electrode body 10. Furthermore, the bottom insulating portion 73 may also completely cover the bottom surface.

[0053] The wound electrode body 10 is provided with a plurality of first electrode tabs 150A and a plurality of second electrode tabs 150B. One end of the plurality of first electrode tabs 150A is connected to the positive electrode 11 described later (see reference). Figure 4 The first metal foil 111 (refer to) Figure 4 The other end of the plurality of first tabs 150A is joined to the aforementioned first connecting structural member 40A by means of ultrasonic welding or the like.

[0054] One end of multiple second electrodes 150B is connected to the negative electrode 12 described later (see reference). Figure 4 The second metal foil 121 (refer to) Figure 4 The other end of the plurality of second tabs 150B is joined to the aforementioned second connecting structural member 40B by means of ultrasonic welding or the like.

[0055] like Figure 2 As shown, the battery 1 of this embodiment includes a plurality of wound electrode bodies 10. Typically, the battery 1 includes two wound electrode bodies 10. These wound electrode bodies 10 are arranged in a third direction D3. The third direction D3 is a direction orthogonal to both the first direction D1 and the second direction D2. Furthermore, the peripheral insulating portion 72 may integrally cover the plurality of wound electrode bodies 10 so that these wound electrode bodies 10 are fixed to each other. In addition, in this embodiment, the insulating member 70 includes a plurality of bottom insulating portions 73 in a manner corresponding one-to-one with the plurality of wound electrode bodies 10.

[0056] Figure 4 Observe in the direction of the arrow on line IV-IV. Figure 3 A cross-sectional view showing the winding of the electrode body. (Refer to...) Figure 4 The details of the wound electrode body 10 in Embodiment 1 will be described.

[0057] like Figure 4 As shown, the wound electrode body 10 is constructed by winding the positive electrode 11 and the negative electrode 12 in a flat shape with a separator 13 in between. The separator 13 is disposed on the innermost and outermost peripheral sides of the wound electrode body 10. The outer peripheral end edge of the separator 13 in the winding direction DR is fixed by a strip member 15 disposed on the outer peripheral surface of the separator 13.

[0058] A separator 13 is disposed between the positive electrode 11 and the negative electrode 12. The separator 13 allows ions to pass between the positive electrode 11 and the negative electrode 12 while simultaneously separating them. These ions are, for example, lithium ions. The separator 13 is electrically insulating.

[0059] The separator 13 may, for example, comprise a polyolefin resin. The separator 13 may also be substantially composed of a polyolefin resin. The polyolefin resin may, for example, comprise at least one selected from polyethylene (PE) and polypropylene (PP).

[0060] The wound electrode body 10 has a pair of flat portions 91 sandwiching the winding center opposite each other and a pair of curved portions 92 connecting the ends of the pair of flat portions to each other as constituent parts.

[0061] A pair of flat portions 91 have a thin plate shape parallel to the winding axis Z. In this embodiment, the pair of flat portions 91 are opposite each other in a third direction D3 orthogonal to the winding axis Z. A pair of curved portions 92 constitute the two ends of the wound electrode body 10 in a direction orthogonal to both the thickness direction (third direction D3) and the winding axis Z direction of the flat portions 91. Specifically, the pair of curved portions 92 constitute the two ends of the wound electrode body 10 in the second direction D2. Each of the pair of curved portions 92 bulges outward in the second direction D2. Each of the pair of curved portions 92 is bent so as to bulge outward in the second direction D2.

[0062] Figure 5 It is Figure 3 A cross-sectional view of the positive electrode of the wound electrode body after it has been unwound. (See attached image.) Figure 5 As shown, the positive electrode 11 has a sheet shape extending along its long side in its unfolded state. Furthermore, the long side direction is the winding direction of the electrode body 10 when the positive electrode 11 is wound. The positive electrode 11 includes a first substrate 110 and a positive electrode active material layer 113 disposed on the first substrate 110. The first substrate 110 includes a first metal foil 111 and a first resin member 112 alternately bonded along their long side in the unfolded state. The boundaries between the first metal foil 111 and the first resin member 112 are designated as first boundaries P1 and... Figure 5 As shown in the figure. Furthermore, the thickness of the first resin member 112 in the thickness direction DT can be thinner than that of the first metal foil 111. The thickness direction DT of the first substrate 110 is substantially parallel to the third direction D3 at the flat portion 91.

[0063] The first metal foil 111 can be, for example, an aluminum-containing metal component. The first resin component 112 can be, for example, polyethylene (PE), polypropylene (PP), PPS (polyphenylene sulfide), or PET (polyethylene terephthalate). The first resin component 112 can also be insulating. To reduce the resistance of the first substrate 110, the first resin component 112 can also contain conductive particles.

[0064] The first metal foil 111 and the first resin component 112 have a first main surface and a second main surface arranged in the thickness direction DT. A positive electrode active material layer 113 is disposed on the first and second main surfaces of the first metal foil 111 and the first and second main surfaces of the first resin component 112. A well-known positive electrode active material layer can be used as the positive electrode active material layer 113.

[0065] Figure 6 It is Figure 3 A cross-sectional view of the unwound negative electrode of the wound electrode body. Figure 6 As shown, the negative electrode 12 has a sheet shape extending along its long side in its unfolded state. Furthermore, the long side direction is the winding direction of the electrode body 10 when the negative electrode 12 is wound. The negative electrode 12 includes a second substrate 120 and a negative electrode active material layer 123 disposed on the second substrate 120. The second substrate 120 includes a second metal foil 121 and a second resin member 122 alternately bonded along their long side in the unfolded state. The boundaries of the second metal foil 121 and the second resin member 122 are designated as second boundaries P2 and... Figure 5 As shown in the figure. Furthermore, the thickness of the second resin member 122 in the thickness direction DT can be thinner than that of the second metal foil 121. The thickness direction DT of the second substrate 120 is substantially parallel to the third direction D3 at the flat portion 91.

[0066] The second metal foil 121 can be, for example, a copper-containing metal component. The second resin component 122 can be, for example, polyethylene (PE), polypropylene (PP), PPS (polyphenylene sulfide), or PET (polyethylene terephthalate). The second resin component 122 can also be insulating. To reduce the resistance of the first substrate 110, the second resin component 122 can also contain conductive particles.

[0067] The second metal foil 121 and the second resin component 122 have a first main surface and a second main surface arranged in the thickness direction DT. A negative electrode active material layer 123 is disposed on the first and second main surfaces of the second metal foil 121 and the first and second main surfaces of the second resin component 122. A well-known negative electrode active material layer can be used as the negative electrode active material layer 123.

[0068] Reference Figures 4-6 In the wound electrode body 10, in the first substrate 110 of the positive electrode 11, the first metal foil 111 and the first resin member 112 are alternately bonded along the winding direction. Similarly, in the wound electrode body 10, in the second substrate 120 of the negative electrode 12, the second metal foil 121 and the second resin member 122 are alternately bonded along the winding direction.

[0069] In each of the aforementioned pair of flat portions 91, a first metal foil 111 and a second metal foil 121 are alternately arranged in the direction opposite to the pair of flat portions. In each of the pair of curved portions 92, a first resin member 112 and a second resin member 122 are alternately arranged in the radial direction of the winding electrode body 10.

[0070] By alternately arranging the first resin member 112 and the second resin member 122 radially at the bend 92, the bend 92 is more prone to flexural deformation and less likely to break compared to a configuration where a metal foil is arranged at the bend 92. Therefore, even under high stress, breakage of the bend 92 can be suppressed.

[0071] Furthermore, in the cross-section of the wound electrode body 10 perpendicular to the winding axis Z, the first boundary P1, which serves as the boundary between the first metal foil 111 and the first resin member 112, is located at the boundaries B1 and B2 between a pair of flat portions 91 and a pair of curved portions 92; similarly, the second boundary P2, which serves as the boundary between the second metal foil 121 and the second resin member 122, is located at the boundaries B1 and B2 between a pair of flat portions 91 and a pair of curved portions 92. Thus, the curved portions 92 are entirely composed of resin members. As a result, damage to the curved portions 92 can be further suppressed.

[0072] More specifically, at each boundary of the pair of flat portions 91 and the pair of curved portions 92, the first boundary P1 and the second boundary P2 are alternately arranged in an arrangement direction in which the first metal foil 111 and the second metal foil 121 are arranged alternately from the inner peripheral side of the wound electrode body 10 toward the outer peripheral side. That is, each boundary of the pair of flat portions 91 and the pair of curved portions 92 is parallel to the third direction D3.

[0073] In this configuration, the bending portion 92 is also entirely made of resin components. This further reduces the risk of breakage of the bending portion 92.

[0074] Furthermore, since the thickness of the first resin member 112 is thinner than the thickness of the first metal foil 111, the bending portion 92 is easier to bend. Additionally, since the thickness of the second resin member 122 is thinner than the thickness of the second metal foil 121, the bending portion 92 is also easier to bend. Therefore, damage to the bending portion 92 can be further suppressed.

[0075] (Implementation Method 2)

[0076] Figure 7 This is a cross-sectional view of the wound electrode body according to Embodiment 2. Furthermore, Figure 7 This is the same as the observation in the direction of the arrow along line III-III in embodiment 1. Figure 1 The cross-sectional view corresponding to the cross-sectional view of the battery shown. (Refer to...) Figure 7 The wound electrode body 10X of Embodiment 2 will be described.

[0077] like Figure 7 As shown, the wound electrode body 10X of Embodiment 2 differs from the wound electrode body 10 of Embodiment 1 in that the positions of the boundaries of the pair of flat portions 91 and the pair of curved portions 92 are different. The other configurations are almost the same.

[0078] When the direction opposite to the pair of flat portions 91 and the direction orthogonal to the winding axis Z of the winding electrode body 10 are defined as the width direction, in a cross-section of the winding electrode body 10 perpendicular to the winding axis Z, the boundaries of each of the pair of flat portions 91 and the pair of curved portions 92 are inclined inward in the width direction as they move from the outer peripheral side to the inner peripheral side of the winding electrode body 10. Furthermore, the width direction is parallel to the second direction D2.

[0079] In a cross section perpendicular to the winding axis Z of the wound electrode body 10, at each boundary of a pair of flat portions 91 and a pair of curved portions 92, the first boundary P1 and the second boundary P2 are alternately arranged in such a way that they go from the outer peripheral side to the inner peripheral side and from the inner side in the width direction of the wound electrode body 10X.

[0080] With the configuration described above, the wound electrode body 10X of Embodiment 2 can achieve almost the same effect as Embodiment 1. Furthermore, by setting the boundary positions of the pair of flat portions 91 and the pair of curved portions 92 as described above, the curved portions 92 can be formed in a fan shape, making them easily deformable. Therefore, when stress is applied to the curved portions 92, breakage of the curved portions 92 can be suppressed.

[0081] (Implementation Method 3)

[0082] Figure 8 This is a cross-sectional view of the wound electrode body according to Embodiment 3. Furthermore, Figure 8 This is the same as the observation in the direction of the arrow along line III-III in embodiment 1. Figure 1 The cross-sectional view corresponding to the cross-sectional view of the battery shown. (Refer to...) Figure 8 The wound electrode body 10Y of Embodiment 3 will be described.

[0083] like Figure 8 As shown, the wound electrode body 10Y of Embodiment 3 differs from the wound electrode body 10 of Embodiment 1 in that the positions of the boundaries of the pair of flat portions 91 and the pair of curved portions 92 are different. The other configurations are almost the same.

[0084] When the direction opposite to the pair of flat portions 91 and the direction orthogonal to the winding axis Z of the winding electrode body 10 are defined as the width direction, in a cross-section of the winding electrode body 10Y perpendicular to the winding axis Z, the boundaries of each of the pair of flat portions 91 and the pair of curved portions 92 are inclined outward in the width direction as they move from the outer peripheral side to the inner peripheral side of the winding electrode body 10. Furthermore, the width direction is parallel to the second direction D2.

[0085] In a cross section perpendicular to the winding axis Z of the wound electrode body 10Y, at each boundary of a pair of flat portions 91 and a pair of curved portions 92, the first boundary P1 and the second boundary P2 are alternately arranged in such a way that they go outward in the width direction from the outer peripheral side to the inner peripheral side of the wound electrode body 10.

[0086] With the configuration described above, the wound electrode body 10Y of Embodiment 3 can also achieve almost the same effect as Embodiment 1. Furthermore, by setting the boundary positions of the pair of flat portions 91 and the pair of curved portions 92 as described above, it is possible to make the proportion (length) of the metal foil disposed on the inner side of the wound electrode body 10 in the pair of flat portions 91 greater than the proportion (length) of the metal foil disposed on the outer side of the wound electrode body 10.

[0087] Generally, heat tends to accumulate on the inside of the wound electrode body. However, by making the above-described configuration, the proportion of metal foil on the inside of the wound electrode body 10Y can be increased, thereby improving heat dissipation on the inside of the wound electrode body 10Y.

[0088] (Other variations)

[0089] In the embodiments 1 to 3 described above, the case where the thickness of the first resin member 112 is thinner than the thickness of the first metal foil 111 and the thickness of the second resin member 122 is thinner than the thickness of the second metal foil 121 is illustrated, but this is not a limitation. The thickness of the first resin member 112 and the first metal foil 111 may be the same, or the thickness of the first resin member 112 may be thicker than the thickness of the first metal foil 111. Furthermore, the thickness of the second resin member 122 and the second metal foil 121 may be the same, or the thickness of the second resin member 122 may be thicker than the thickness of the second metal foil 121.

[0090] Embodiments of the present invention have been described, but should be considered illustrative rather than restrictive in all respects. The scope of the invention is defined by the claims and is intended to include all modifications within the scope and equivalent meaning of the claims.

Claims

1. A wound electrode body, wherein, The positive and negative electrodes are wound into a flat shape with a separator between them. The wound electrode body has a pair of flat portions facing each other with the winding center sandwiched between them and a pair of curved portions connecting the ends of the pair of flat portions to each other. The positive electrode includes a first substrate, in which a first metal foil and a first resin component are alternately bonded along the winding direction of the wound electrode body. The negative electrode includes a second substrate, in which a second metal foil and a second resin component are alternately bonded along the winding direction. In each of the pair of flat portions, the first metal foil and the second metal foil are arranged alternately in the direction opposite to the pair of flat portions. In each of the pair of curved portions, the first resin component and the second resin component are arranged alternately in the radial direction of the wound electrode body.

2. The wound electrode body according to claim 1, In the cross-section of the wound electrode body perpendicular to the winding axis, The first boundary, which serves as the boundary between the first metal foil and the first resin component, is located at the boundary between the pair of flat portions and the pair of curved portions. The second boundary, which serves as the boundary between the second metal foil and the second resin component, is located at the boundary between the pair of flat portions and the pair of curved portions.

3. The wound electrode body according to claim 2, In the cross-section perpendicular to the winding axis, At each boundary of the pair of flat portions and the pair of curved portions, the first boundary and the second boundary are alternately arranged in the arrangement direction in which the first metal foil and the second metal foil are alternately arranged.

4. The wound electrode body according to claim 2, When the direction orthogonal to the direction opposite to the winding shaft and the pair of flat portions is set as the width direction, In the cross-section perpendicular to the winding axis, At each boundary of the pair of flat portions and the pair of curved portions, the first boundary and the second boundary are alternately arranged such that they extend from the outer peripheral side of the wound electrode body to the inner peripheral side and then to the inner side in the width direction.

5. The wound electrode body according to claim 2, When the direction orthogonal to the direction opposite to the winding shaft and the pair of flat portions is set as the width direction, In the cross-section perpendicular to the winding axis, At each boundary of the pair of flat portions and the pair of curved portions, the first boundary and the second boundary are alternately arranged in such a way that they move outward in the width direction from the outer peripheral side to the inner peripheral side of the wound electrode body.

6. The wound electrode body according to any one of claims 1 to 5, The thickness of the first resin component is thinner than the thickness of the first metal foil.

7. The wound electrode body according to claim 6, The thickness of the second resin component is thinner than the thickness of the second metal foil.

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