Power storage element

Abstract

This power storage element comprises an electrode body formed by winding an electrode plate, and a sheet member fixed to the outermost periphery of the electrode body, wherein the elongation rigidity of the sheet member is higher than the elongation rigidity of the electrode plate.

Description

Energy storage element

[0001] The present invention relates to an energy storage element.

[0002] Patent Document 1 discloses a lithium ion secondary battery having a wound electrode group in which a positive electrode sheet and a negative electrode sheet are wound with a separator interposed therebetween, and a battery container that houses the wound electrode group, with a stretchable rubber-based insulating resin sheet provided between the wound electrode group and the battery container.

[0003] JP 2013-73809 A

[0004] The electrode assembly formed by winding electrode plates expands as the energy storage device is used, and there is a risk of damage due to this expansion, so there is a need to suppress this damage. The lithium ion secondary battery disclosed in the above Patent Document 1 is provided with an elastic rubber-based insulating resin sheet for the purpose of preventing a short circuit when a metallic foreign object pierces or penetrates, but does not suppress damage due to the expansion of the wound electrode group.

[0005] The present invention was made by the inventors of the present application by focusing on the above-mentioned problem, and has an object to provide an energy storage element that can suppress damage to an electrode body.

[0006] An energy storage element according to one aspect of the present invention comprises an electrode body formed by winding electrode plates and a sheet member fixed to the outermost periphery of the electrode body, wherein the tensile rigidity of the sheet member is higher than the tensile rigidity of the electrode plates.

[0007] According to the energy storage element of the present invention, damage to the electrode assembly can be suppressed.

[0008] FIG. 1 is a perspective view showing the appearance of an energy storage element according to an embodiment. FIG. 2 is a perspective view showing each component of an energy storage element according to an embodiment when disassembled. FIG. 3 is a perspective view showing the configuration of an electrode assembly according to an embodiment. FIG. 4 is a cross-sectional view showing the configuration of an electrode assembly according to an embodiment. FIG. 5 is a perspective view showing the configuration of an electrode assembly and a sheet member according to an embodiment. FIG. 6 is a cross-sectional view showing the configuration of an electrode assembly and a sheet member according to an embodiment. FIG. 7 is a cross-sectional view illustrating how a sheet member according to an embodiment suppresses damage to an electrode assembly. FIG. 8 is a cross-sectional view showing a configuration in which a sheet member according to a first modified example of the embodiment is fixed to the outermost periphery of an electrode assembly. FIG. 9 is a cross-sectional view showing a configuration in which a sheet member according to a second modified example of the embodiment is fixed to the outermost periphery of an electrode assembly. FIG. 10 is a perspective view showing a configuration in which a sheet member according to a third modified example of the embodiment is fixed to the outermost periphery of an electrode assembly. FIG. 11 is a cross-sectional view showing a configuration in which a sheet member according to a fourth modified example of the embodiment is fixed to the outermost periphery of an electrode assembly. FIG. 12 is a cross-sectional view showing a configuration in which a sheet member according to a fifth modified example of the embodiment is fixed to the outermost periphery of an electrode assembly. FIG. 13 is a cross-sectional view showing a configuration in which a sheet member according to a sixth modified example of the embodiment is fixed to the outermost periphery of an electrode assembly. Fig. 14 is a cross-sectional view showing a configuration in which a sheet member according to a seventh modification of the embodiment is fixed to the outermost periphery of an electrode body. Fig. 15 is a plan view showing an example of an electricity storage device according to an eighth modification of the embodiment.

[0009] (1) A storage element according to one aspect of the present invention comprises an electrode body formed by winding electrode plates and a sheet member fixed to the outermost periphery of the electrode body, wherein the tensile rigidity of the sheet member is higher than the tensile rigidity of the electrode plates.

[0010] In an energy storage device according to one embodiment of the present invention, the sheet member fixed to the outermost periphery of the electrode assembly has a higher tensile rigidity than the electrode plates of the electrode assembly. This allows the electrode assembly to be reinforced by the sheet member, thereby suppressing expansion of the electrode assembly and therefore suppressing damage to the electrode assembly.

[0011] (2) In the energy storage element described in (1) above, the electrode body may have a curved portion and a flat portion formed by winding the electrode plate, and the sheet member may be arranged across the boundary between the curved portion and the flat portion.

[0012] According to the energy storage element described in (2) above, the sheet member is disposed across the boundary between the curved portion and the flat portion of the electrode body, thereby reinforcing the boundary. Since the boundary between the curved portion and the flat portion of the electrode body is easily damaged when the electrode body expands, reinforcing the boundary can prevent damage to the boundary.

[0013] (3) In the energy storage device described in (2) above, the sheet member may cover the entire outermost periphery of the curved portion.

[0014] According to the energy storage element described in (3) above, the sheet member covers the entire outermost periphery of the curved portion of the electrode body, thereby reinforcing the curved portion of the electrode body. When the electrode body expands, the curved portion of the electrode body expands and is likely to be damaged, so by reinforcing the curved portion of the electrode body, expansion of the curved portion can be suppressed.

[0015] (4) In the energy storage element described in (3) above, the sheet member may cover the entire outermost periphery of the electrode body.

[0016] According to the energy storage element described in (4) above, the sheet member covers the entire outermost periphery of the electrode body, thereby reinforcing the entire periphery of the electrode body, thereby effectively suppressing expansion of the electrode body.

[0017] (5) In the energy storage device according to any one of (1) to (4) above, the sheet member may be made of fiber-reinforced plastic.

[0018] According to the energy storage element described in (5) above, by forming the sheet member from fiber-reinforced plastic, it is possible to easily produce a sheet member with high tensile rigidity.

[0019] Hereinafter, with reference to the drawings, an energy storage element according to an embodiment of the present invention (including its modified examples) will be described. The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples only and are not intended to limit the present invention. In each drawing, dimensions and the like are not strictly illustrated. In each drawing, the same or similar components are designated by the same reference numerals.

[0020] In the following description and drawings, the X-axis direction is defined as the direction in which a pair of terminals (positive and negative electrodes, hereinafter the same) of the energy storage element are arranged, the direction in which a pair of current collectors are arranged, the direction in which the winding axis of the electrode assembly extends, or the direction in which the short side surfaces of the container face each other. The Y-axis direction is defined as the direction in which the long side surfaces of the container face each other, the thickness direction (flattening direction) of the container or electrode assembly, or the direction in which the flat portions of the electrode assembly face each other. The Z-axis direction is defined as the direction in which the container body and lid of the container are arranged, the direction in which the terminals and electrode assembly are arranged, the direction in which the curved portions of the electrode assembly face each other, or the up-down direction. The X-axis direction, Y-axis direction, and Z-axis direction intersect each other (orthogonal in this embodiment). Depending on the usage mode, the Z-axis direction may not be the up-down direction; however, for convenience of explanation, the Z-axis direction will be described below as the up-down direction.

[0021] In the following description, the positive X-axis direction refers to the direction of the arrow on the X-axis, and the negative X-axis direction refers to the direction opposite to the positive X-axis direction. When simply referring to the X-axis direction, it refers to both or either of the positive X-axis direction and the negative X-axis direction. The same applies to the Y-axis direction and the Z-axis direction. Expressions indicating relative directions or attitudes, such as parallel and orthogonal, also include cases where the directions or attitudes are not strictly those. When two directions are parallel (or orthogonal), it does not only mean that the two directions are completely parallel (or orthogonal), but also means that the directions are substantially parallel (or orthogonal), that is, there is a difference of, for example, about several percent. In the following description, when the term "insulation" is used, it means "electrical insulation". An insulating material has a volume resistivity of 1×10 １０ It is preferable that the material be made of a material with a resistance of Ωm or more.

[0022] (Embodiment) [1 General Description of Energy Storage Device 10] First, an overall description of the energy storage device 10 according to the present embodiment will be given using Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing the appearance of the energy storage device 10 according to the present embodiment. Fig. 2 is a perspective view showing the components of the energy storage device 10 according to the present embodiment in an exploded form.

[0023] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, more specifically, a nonaqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used as a battery for driving or starting the engine of a moving object such as an automobile, motorcycle, personal watercraft, ship, snowmobile, agricultural machinery, construction machinery, automatic guided vehicle (AGV), or electric railway vehicle. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicle. Examples of the electric railway vehicle include a train, a monorail, a linear motor car, and a hybrid train equipped with both a diesel engine and an electric motor. The energy storage element 10 can also be used as a stationary battery for home or business use.

[0024] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, or may be a capacitor. The energy storage element 10 may be a primary battery instead of a secondary battery. The energy storage element 10 may be a battery using a solid electrolyte. The energy storage element 10 may be a pouch-type energy storage element. In the present embodiment, the energy storage element 10 is illustrated as having a rectangular parallelepiped shape (square) that is flattened in the Y-axis direction, but the shape of the energy storage element 10 is not limited to a rectangular parallelepiped shape, and may be a polygonal prism shape other than a rectangular parallelepiped, an elongated cylinder shape, an elliptical cylinder shape, a cylindrical shape, or the like.

[0025] As shown in FIG. 1 , the energy storage element 10 includes a container 100, a pair of (positive and negative) terminals 200, and a pair of (positive and negative) upper gaskets 400. As shown in FIG. 2 , the container 100 contains a pair of (positive and negative) lower gaskets 500, a pair of (positive and negative) current collectors 600, an electrode assembly 700, and a sheet member 800. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but is not shown. The type of electrolyte is not particularly limited as long as it does not impair the performance of the energy storage element 10, and various electrolytes can be selected. In addition to the above components, spacers disposed on the sides or below the electrode assembly 700, an insulating film enclosing the electrode assembly 700 and the current collectors 600, etc. may also be disposed.

[0026] The container 100 is a rectangular parallelepiped (square or box-shaped) case that includes a container body 110 with an opening formed therein and a lid 120 that closes the opening of the container body 110. The container body 110 is a rectangular cylindrical member with a bottom that constitutes the main body of the container 100. The container body 110 includes a pair of flat, rectangular long side walls 111 on both side surfaces in the Y-axis direction (long side surfaces), a pair of flat, rectangular short side walls 112 on both side surfaces in the X-axis direction (short side surfaces), and a flat, rectangular bottom wall 113 on the surface in the negative Z-axis direction (bottom surface).

[0027] The lid 120 is a rectangular plate-like member that is elongated in the X-axis direction and that constitutes the lid of the container 100, and is disposed in the positive Z-axis direction of the container body 110. The lid 120 is formed with a liquid injection section 130 and a gas release valve 140. The liquid injection section 130 is a portion for injecting electrolyte into the container 100 during the manufacture of the energy storage device 10, and includes a liquid injection port 131 and a liquid injection plug 132. The liquid injection port 131 is a circular through-hole formed in the lid 120. The liquid injection plug 132 is a closing member (lid member) that is joined to the lid 120 and closes the liquid injection port 131. The gas release valve 140 is a safety valve that releases pressure inside the container 100 if the pressure rises excessively.

[0028] With this configuration, the container 100 is configured such that the electrode assembly 700 and the like are housed inside the container body 110, and then the container body 110 and the lid 120 are joined by welding or the like, thereby sealing the interior. The material of the container 100 (container body 110 and lid 120) is not particularly limited, and can be a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet, but resin can also be used.

[0029] The terminals 200 are electrode terminals (positive and negative terminals) electrically connected to the electrode body 700 via the current collector 600. The terminals 200 are metal members for conducting electricity stored in the electrode body 700 to the external space of the energy storage element 10 and for introducing electricity into the internal space of the energy storage element 10 in order to store electricity in the electrode body 700. The terminals 200 are formed of a conductive member such as a metal, such as aluminum, an aluminum alloy, copper, or a copper alloy. The terminals 200 are connected (joined) to the current collector 600 by crimping, welding, or the like, and are attached to the lid body 120.

[0030] The current collectors 600 are disposed on both sides of the electrode body 700 in the X-axis direction and are connected (joined) to the electrode body 700 and the terminal 200, serving as current collecting members (positive electrode current collector and negative electrode current collector) that electrically connect the electrode body 700 and the terminal 200. The current collectors 600 are connected (joined) to an end portion 720 of the electrode body 700 (described later) by crimping, welding, or the like, and are also connected (joined) to the terminal 200 by crimping, welding, or the like, as described above, and are fixed to the lid 120. The material of the current collectors 600 is not particularly limited, but the positive electrode current collector 600 is formed of a conductive material such as aluminum or an aluminum alloy, similar to the positive electrode current collector foil 701a of the electrode body 700 (described later). The negative electrode current collector 600 is formed of a conductive material such as copper or a copper alloy, similar to the negative electrode current collector foil 702a of the electrode body 700 (described later).

[0031] The upper gasket 400 is a gasket disposed between the lid 120 of the container 100 and the terminal 200, and the lower gasket 500 is a gasket disposed between the lid 120 and the current collector 600. The upper gasket 400 and the lower gasket 500 are formed of an insulating resin or the like, but the material is not particularly limited.

[0032] The electrode assembly 700 is an electricity storage element (power generation element) that includes electrode plates (positive and negative electrode plates) and a separator and is formed by winding these electrode plates and separators. In this embodiment, the electrode assembly 700 has an oval shape (long cylindrical shape) when viewed from the X-axis direction. The electrode assembly 700 includes an electrode assembly main body 710 and end portions 720 that protrude from the electrode assembly main body 710 on both sides in the X-axis direction, and as described above, the end portions 720 are connected (joined) to the current collector 600. A sheet member 800 is disposed on the outermost periphery of the electrode assembly 700 (electrode assembly main body 710). The configurations of the electrode assembly 700 and the sheet member 800 are described in detail below.

[0033] [2 Description of Electrode Assembly 700 and Sheet Member 800] FIG. 3 is a perspective view showing the configuration of the electrode assembly 700 according to the present embodiment. FIG. 3(a) shows the configuration of the electrode assembly 700 in a partially unfolded state, with the wound electrode plates, and FIG. 3(b) shows the configuration of the electrode assembly 700 after the electrode plates have been wound. FIG. 4 is a cross-sectional view showing the configuration of the electrode assembly 700 according to the present embodiment. FIG. 4 shows a cross-section of the electrode assembly 700 of FIG. 3(b) cut along a plane passing through line IV-IV and parallel to the YZ plane. FIG. 5 is a perspective view showing the configuration of the electrode assembly 700 and sheet member 800 according to the present embodiment. FIG. 5(a) shows the state before the sheet member 800 is fixed to the electrode assembly 700, and FIG. 5(b) shows the state after the sheet member 800 is fixed to the electrode assembly 700. FIG. 6 is a cross-sectional view showing the configuration of the electrode assembly 700 and sheet member 800 according to the present embodiment. Fig. 6 shows a cross section of the electrode body 700 and sheet member 800 in Fig. 5(b) when cut along a plane passing through line VI-VI and parallel to the YZ plane. Fig. 7 is a cross section illustrating how the sheet member 800 according to this embodiment suppresses damage to the electrode body 700. Fig. 7(a) and Fig. 7(b) show cross sections of the electrode body 700 and sheet member 800 housed in the container 100 (container body 110) when cut along a plane parallel to the YZ plane.

[0034] [2.1 Description of Electrode Assembly 700] First, a detailed description will be given of the configuration of the electrode assembly 700. As shown in Fig. 3(a) , the electrode assembly 700 includes a positive electrode plate 701, a negative electrode plate 702, and separators 703 and 704.

[0035] The positive electrode plate 701 is an electrode plate in which a positive electrode active material layer 701b is formed on the surface of a positive electrode current collector foil 701a, which is a long, strip-shaped current collector foil (metal foil) made of aluminum or an aluminum alloy. The negative electrode plate 702 is an electrode plate in which a negative electrode active material layer 702b is formed on the surface of a negative electrode current collector foil 702a, which is a long, strip-shaped current collector foil (metal foil) made of copper or a copper alloy. For the positive electrode current collector foil 701a and the negative electrode current collector foil 702a, any known material may be used as long as it is stable against oxidation-reduction reactions during charge and discharge, such as nickel, iron, stainless steel, titanium, baked carbon, conductive polymers, conductive glass, or an Al—Cd alloy. The positive electrode active material used in the positive electrode active material layer 701b and the negative electrode active material used in the negative electrode active material layer 702b may be any known material as long as it is capable of absorbing and releasing charge-transport ions.

[0036] Separators 703 and 704 are microporous sheets made of resin. Any known material can be used as the material for separators 703 and 704 as long as it does not impair the performance of energy storage element 10. Separators 703 and 704 can be made of woven fabric or nonwoven fabric that is insoluble in organic solvents, or a synthetic resin microporous film made of a polyolefin resin such as polyethylene.

[0037] The electrode assembly 700 is formed by alternately stacking and winding positive and negative electrode plates 701, 702, and separators 703 and 704. That is, the electrode assembly 700 is formed by stacking and winding the positive and negative electrode plates 701, 703, 702, and 704 in this order. In this embodiment, the electrode assembly 700 is a flat, wound electrode assembly formed by winding the positive and negative electrode plates 701, 702, and the like around a winding axis L that extends parallel to the lid 120 (in the X-axis direction). The winding axis L is an imaginary axis that serves as the central axis when winding the positive and negative electrode plates 701, 702, and the like, and in this embodiment, is a straight line that passes through the center of the electrode assembly 700 and is parallel to the X-axis direction.

[0038] Specifically, the electrode assembly 700 includes a positive electrode plate 701 and a negative electrode plate 702 wound with separators 703 and 704 interposed therebetween, offset from each other in the direction in which the winding axis L extends (the X-axis direction; hereinafter, also referred to as the winding axis direction). The positive electrode plate 701 and the negative electrode plate 702 have, at their respective ends in the offset direction, portions (active material layer-free portions) where the positive electrode active material layer 701 b and the negative electrode active material layer 702 b are not formed (coated) and the positive electrode current collector foil 701 a and the negative electrode current collector foil 702 a are exposed. As a result, as shown in FIG. 3B , the electrode assembly 700 has, at one end in the winding axis direction (the end in the negative X-axis direction), a positive electrode end 720 in which the active material layer-free portions of the positive electrode plate 701 are stacked and bundled. The electrode body 700 has, at the other end in the winding axis direction (the end in the positive direction of the X-axis), a negative electrode end 720 in which the active material layer-free portions of the negative electrode plates 702 are stacked and bundled.

[0039] That is, the electrode body 700 includes an electrode body main body 710 that forms the main body of the electrode body 700, and a pair of (positive and negative) end portions 720 that protrude on both sides in the X-axis direction from the entire X-axis end portion of the electrode body main body 710. The electrode body main body 710 is an elongated cylindrical portion (active material layer forming portion) formed by winding together the separators 703 and 704 and the portions of the positive electrode plate 701 and the negative electrode plate 702 on which the positive electrode active material layer 701b and the negative electrode active material layer 702b are formed (coated). As a result, the electrode body main body 710 includes a pair of electrode body curved portions 711 on both sides in the Z-axis direction and a pair of electrode body flat portions 712 on both sides in the Y-axis direction. In other words, the electrode body 700 (electrode body main body portion 710) has a flat shape with a pair of curved electrode body curved portions 711 and a pair of flat electrode body flat portions 712 formed by winding a positive electrode plate 701, a negative electrode plate 702, and separators 703 and 704 around a winding axis L.

[0040] As shown in (b) of FIG. 3 and FIG. 4 , the electrode curved portion 711 is a curved portion (curved portion) that curves in a semicircular arc shape so as to protrude in the Z-axis direction when viewed from the X-axis direction and extends in the X-axis direction. The pair of electrode curved portions 711 are arranged opposite the lid 120 of the container 100 and the bottom wall portion 113 of the container body 110. That is, when viewed from the X-axis direction, the pair of electrode curved portions 711 are curved portions that protrude on both sides in the Z-axis direction toward the lid 120 and the bottom wall portion 113. The electrode flat portion 712 is a flat, rectangular portion (flat portion) that connects the ends of the pair of electrode curved portions 711 and extends parallel to the XZ plane facing the Y-axis direction. A pair of electrode flat portions 712 aligned in the Y-axis direction are arranged opposite the long side wall portions 111 on both sides in the Y-axis direction of the container body 110. The curved shape of the electrode curved portion 711 is not limited to a semicircular arc shape, but may be a part of an ellipse, etc., and may be any curved shape. The outer surface of the electrode flat portion 712 facing the Y-axis direction is not limited to being flat, but the outer surface may be slightly concave or slightly bulged.

[0041] In this way, the electrode body 700 is formed by winding the electrode plates (positive electrode plate 701, negative electrode plate 702), and by winding the electrode plates (positive electrode plate 701, negative electrode plate 702), an electrode body curved portion 711 and an electrode body flat portion 712 are formed in the electrode body 700. In this configuration, as shown in FIG. 4 , the boundary portion between the electrode body curved portion 711 and the electrode body flat portion 712 is referred to as a boundary portion 713. The boundary portion 713 is a boundary (connection portion) between the electrode body curved portion 711 and the electrode body flat portion 712 formed in the electrode body main body portion 710, and extends in the X-axis direction. Four boundary portions 713 are formed in the electrode body 700 (electrode body main body portion 710).

[0042] [2.2 Description of Sheet Member 800] Next, a detailed description will be given of the configuration of the sheet member 800. As shown in Fig. 5(a), the sheet member 800 is a sheet-like member that is separate from the electrode assembly 700, and as shown in Fig. 5(b), the sheet member 800 is disposed on the outermost periphery of the electrode assembly 700.

[0043] In this embodiment, the sheet member 800 has the same length as the electrode body main body 710 in the X-axis direction and is disposed on the outermost periphery of the electrode body main body 710. The outermost periphery of the electrode body 700 (electrode body main body 710) refers to the final turn (outermost portion) of the electrode body 700 (electrode body main body 710) after winding the positive electrode plate 701, the negative electrode plate 702, and the separators 703 and 704. The sheet member 800 is disposed on the outer peripheral surface of the final turn (outermost portion) of the electrode body 700 (electrode body main body 710). The sheet member 800 may be formed slightly shorter than the electrode body main body 710 in the X-axis direction, or may be formed longer than the electrode body main body 710 (it may protrude to the end 720) as long as it does not interfere with the joining of the current collector 600 and the end 720.

[0044] As shown in FIG. 6 , the sheet member 800 includes a pair of sheet curved portions 810 and a pair of sheet flat portions 820. The sheet curved portions 810 are sheet-like portions arranged on the outermost periphery (outer peripheral surface) of the electrode body curved portion 711. In the present embodiment, the sheet curved portions 810 are arranged over the entire outermost periphery (outer peripheral surface) of the electrode body curved portion 711, covering the entire outermost periphery (outer peripheral surface) of the electrode body curved portion 711. As a result, the pair of sheet curved portions 810 are arranged to sandwich the pair of electrode body curved portions 711 in the Z-axis direction, covering the entire outermost periphery (outer peripheral surface) of the pair of electrode body curved portions 711. The sheet flat portions 820 are sheet-like portions arranged on the outermost periphery (outer peripheral surface) of the electrode body flat portion 712. In the present embodiment, the sheet flat portions 820 are arranged over the entire outermost periphery (outer peripheral surface) of the electrode body flat portion 712, covering the entire outermost periphery (outer peripheral surface) of the electrode body flat portion 712. As a result, the pair of sheet flat portions 820 are arranged to sandwich the pair of electrode body flat portions 712 in the Y-axis direction, and cover the entire outermost periphery (outer peripheral surface) of the pair of electrode body flat portions 712. In this way, the sheet member 800 covers the entire outermost periphery (outer peripheral surface) of the electrode body main body portion 710.

[0045] In the present embodiment, the sheet flat portion 820 in the positive direction of the Y axis includes a sheet member first end portion 821 and a sheet member second end portion 822. The sheet member first end portion 821 and the sheet member second end portion 822 are portions of the sheet flat portion 820 that extend in the X axis direction and are located at positions of the sheet flat portion 820 close to the electrode body curved portion 711 (in the present embodiment, the ends in the positive direction of the Z axis). The sheet member first end portion 821 and the sheet member second end portion 822 are ends of the sheet member 800 (see FIG. 5 ). The sheet member 800 is wrapped around the outermost periphery (outer peripheral surface) of the electrode body 700 (electrode body main body portion 710) with the sheet member first end portion 821 and the sheet member second end portion 822 as the starting and ending points. In the present embodiment, the sheet member first end portion 821 and the sheet member second end portion 822 are arranged opposite each other in the Z axis direction (with their tips in contact) so as not to overlap in the Y axis direction (thickness direction).

[0046] The sheet member first end 821 and the sheet member second end 822 may or may not be connected (joined) to each other in the Z-axis direction. When the sheet member first end 821 and the sheet member second end 822 are connected (joined) to each other in the Z-axis direction, an adhesive layer such as a pressure-sensitive adhesive layer may be provided on at least one of the surfaces of the sheet member first end 821 and the sheet member second end 822 that face each other in the Z-axis direction, thereby connecting (joining) them. The sheet member first end 821 and the sheet member second end 822 may be connected (joined) to each other by providing a recess on one surface and a protrusion on the other surface, and mechanically joining the sheet member first end 821 and the sheet member second end 822 by engagement or press-fitting or other means. In this way, the sheet member first end 821 and the sheet member second end 822 do not overlap in the Y-axis direction (thickness direction), making it less likely that a gap will form between the sheet member 800 and the electrode body 700 (electrode body main body portion 710).

[0047] In this way, the sheet member 800 covers the entire outermost periphery of the electrode body 700 (electrode body main body portion 710). As a result, the sheet member 800 is arranged across the boundary portion 713 between the electrode body curved portion 711 and the electrode body flat portion 712. In other words, the sheet member 800 is arranged continuously on the outer periphery of the electrode body curved portion 711 and the electrode body flat portion 712, from the electrode body curved portion 711 on one side of the boundary portion 713 to the electrode body flat portion 712 on the other side of the boundary portion 713. In other words, the portion of the sheet member 800 that is close to the sheet flat portion 820 of the sheet curved portion 810 and the portion of the sheet flat portion 820 that is close to the sheet curved portion 810 are formed continuously and integrally. The sheet member 800 covers the entire outermost periphery of the electrode body curved portion 711. In other words, the sheet member 800 is arranged continuously on the outer surface of the electrode body curved portion 711, from one end to the other end of the electrode body curved portion 711. In other words, the sheet member 800 is formed continuously and integrally from one end to the other end of the sheet curved portion 810 .

[0048] The sheet member 800 is fixed to the outermost periphery of the electrode body 700 (electrode body main body portion 710). In the present embodiment, the sheet member 800 has an adhesive layer such as a pressure-sensitive adhesive layer provided on the inner surfaces of the sheet member first end portion 821 and the sheet member second end portion 822, and the sheet member first end portion 821 and the sheet member second end portion 822 are attached and fixed to the outermost periphery of the electrode body 700 by adhesion such as pressure-sensitive adhesive. The adhesive layer such as a pressure-sensitive adhesive layer may be provided at any position on the sheet member 800, and the sheet member 800 may be attached and fixed to the outermost periphery of the electrode body 700 at any position. The sheet member 800 has an adhesive layer such as a pressure-sensitive adhesive layer provided on the entire inner surface of the sheet member 800, and the entire inner surface of the sheet member 800 may be attached and fixed to the outermost periphery of the electrode body 700. The sheet member 800 may be fixed to the electrode body 700 by adhesion using an adhesive or the like, or by welding using heat welding or the like.

[0049] The elongation rigidity of the sheet member 800 is higher than that of the electrode plates included in the electrode assembly 700. Elongation rigidity is an index that indicates the ease of deformation when an axial tensile force is applied to an object, and can also be referred to as axial rigidity. The elongation rigidity is measured in accordance with JIS Z2241:2001, and the elongation rigidity of the two members is compared. In other words, the sheet member 800 elongates less within elastic deformation than the electrode plates. The sheet member 800 is less likely to elongate than the electrode plates when pulled with the same force as the electrode plates. The elongation rigidity of the sheet member 800 is higher than that of at least one of the positive electrode plate 701 and the negative electrode plate 702. The elongation rigidity of the sheet member 800 is preferably higher than that of the electrode plate located at the outermost periphery of the positive electrode plate 701 or the negative electrode plate 702 (in this embodiment, the negative electrode plate 702). In this embodiment, the tensile rigidity of the sheet member 800 is higher than the tensile rigidity of both the positive electrode plate 701 and the negative electrode plate 702 .

[0050] The sheet member 800 is a thin, high-strength, and flexible sheet-like member containing reinforcing fibers such as carbon fiber, glass fiber, or aramid fiber. In this embodiment, the sheet member 800 is formed from fiber-reinforced plastics (FRP). The thickness of the sheet member 800 is preferably 50 μm or more and 200 μm or less, more preferably 70 μm or more and 150 μm or less, and even more preferably 90 μm or more and 110 μm or less. This prevents the formation of gaps between the sheet member 800 and the outermost periphery (outer periphery) of the electrode body 700 (particularly the curved portion 711 of the electrode body) when the sheet member 800 is wrapped around the outermost periphery (outer periphery). The sheet member 800 is not limited to the above-mentioned materials and may be formed from a hard (highly tensile rigid) resin or may be formed by insulating a metal plate (metal foil).

[0051] In the electrode assembly 700 and sheet member 800 configured as described above, the sheet member 800 suppresses damage to the electrode assembly 700 as follows. First, as shown in (a) of Figure 7, when the electrode assembly 700 expands, the electrode assembly flat portion 712 expands in the Y-axis direction, generating an expansion force F1 in the Y-axis direction. Because the electrode assembly flat portion 712 is sandwiched between the pair of long side wall portions 111 of the container 100 (container body 110), the clearance in the Y-axis direction in the electrode assembly flat portion 712 decreases due to the expansion.

[0052] As shown in FIG. 7B , the electrode assembly flat portion 712 expands in the Z-axis direction as a result of the reduction in clearance in the Y-axis direction, generating an expansion force F2 in the Z-axis direction. The electrode assembly curved portion 711 also expands. As a result, if the sheet member 800 is not fixed to the outermost periphery of the electrode assembly 700, stress may concentrate on the electrode assembly curved portion 711 and its surroundings, particularly on the boundary portion 713 between the electrode assembly curved portion 711 and the electrode assembly flat portion 712, potentially damaging the electrode assembly 700. In contrast, in this embodiment, the sheet member 800, which has higher tensile rigidity than the electrode plates of the electrode assembly 700, is fixed to the outermost periphery of the electrode assembly 700. Therefore, the expansion force from the inside of the electrode assembly 700 can be suppressed by the compression force from the outside of the sheet member 800. This suppresses the rate at which strain increases in the electrode plates, thereby increasing the time until the electrode plates break. This suppresses damage to the electrode assembly 700 and extends the life of the energy storage element 10. Here, the container 100 in which the electrode assembly 700 is housed will be compared between a case in which the container 100 has a film-like wall and a case in which the container 100 has a flat plate-like wall. When the container 100 has a film-like wall, the wall of the container 100 also deforms (expands) when the electrode assembly 700 expands, so the clearance in the Y-axis direction at the electrode assembly flat portion 712 is less likely to decrease. In other words, the expansion force F2 of the electrode assembly 700 in the Z-axis direction is relatively small. On the other hand, when the container 100 has a flat plate-like wall, the wall of the container 100 is less likely to deform (expand) even when the electrode assembly 700 expands, so the clearance in the Y-axis direction at the electrode assembly flat portion 712 is more likely to decrease. In other words, the expansion force F2 of the electrode assembly 700 in the Z-axis direction is relatively large. Therefore, when the container 100 has a flat plate-like wall, the life of the energy storage element 10 is more significantly extended.

[0053] [3 Description of Effects] As described above, according to the energy storage element 10 according to the embodiment of the present invention, the sheet member 800 fixed to the outermost periphery of the electrode assembly 700 has a higher tensile rigidity than the electrode plates (positive electrode plate 701, negative electrode plate 702) of the electrode assembly 700. This allows the electrode assembly 700 to be reinforced by the sheet member 800, thereby suppressing expansion of the electrode assembly 700. Therefore, damage to the electrode assembly 700 can be suppressed.

[0054] The sheet member 800 is disposed across the boundary portion 713 between the electrode body curved portion 711 and the electrode body flat portion 712 of the electrode body 700, thereby reinforcing the boundary portion 713. When the electrode body 700 expands, the boundary portion 713 between the electrode body curved portion 711 and the electrode body flat portion 712 is easily damaged, so by reinforcing the boundary portion 713, damage to the boundary portion 713 can be suppressed.

[0055] The sheet member 800 covers the entire outermost periphery of the electrode body curved portion 711 of the electrode body 700, thereby reinforcing the electrode body curved portion 711. When the electrode body 700 expands, the electrode body 700 is likely to be damaged by the expansion of the electrode body curved portion 711, so by reinforcing the electrode body curved portion 711, the expansion of the electrode body curved portion 711 can be suppressed.

[0056] The sheet member 800 covers the entire outermost periphery of the electrode body 700, thereby reinforcing the entire periphery of the electrode body 700, thereby effectively suppressing expansion of the electrode body 700.

[0057] By forming the sheet member 800 from fiber reinforced plastic, it is possible to easily manufacture a sheet member 800 with high elongation rigidity.

[0058] [4 Description of Modifications] While the energy storage device 10 according to the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The embodiment disclosed herein is illustrative in all respects, and the scope of the present invention includes all modifications within the meaning and scope of the claims.

[0059] (Variations 1 and 2) In the above embodiment, the sheet member 800 is fixed to the outermost periphery of the electrode body 700 by being adhered to the outermost periphery of the electrode body 700 with adhesive or the like, but this is not limited to this and various other configurations are possible. Fig. 8 is a cross-sectional view showing a configuration in which the sheet member 800 according to Variation 1 of this embodiment is fixed to the outermost periphery of the electrode body 700. Fig. 9 is a cross-sectional view showing a configuration in which the sheet member 800 according to Variation 2 of this embodiment is fixed to the outermost periphery of the electrode body 700. Figs. 8 and 9 correspond to (b) of Fig. 6.

[0060] As shown in FIG. 8 , in Modification 1, a sheet member 800 has a first end portion 821 and a second end portion 822 connected by a connecting member 830. The connecting member 830 is an adhesive tape (adhesive sheet, adhesive film) with an adhesive layer provided on its inner surface, or a tape (sheet, film) with an adhesive applied to its inner surface, and is attached to and fixed to the first end portion 821 and the second end portion 822 of the sheet member. The connecting member 830 may be fixed to the first end portion 821 and the second end portion 822 of the sheet member by thermal welding or the like. This fixes the sheet member 800 to the outermost periphery of the electrode body 700. The other configurations of this modification are similar to those of the above-described embodiment, and therefore detailed description thereof will be omitted.

[0061] 9 , in Modification 2, the sheet member 800 is fixed to the outermost periphery of the electrode assembly 700 by being sandwiched between the electrode assembly flat portion 712 of the electrode assembly 700 and the long side wall portion 111 of the container 100 (container body 110). The other configurations of this modification are the same as those of the above-described embodiment, and therefore detailed description thereof will be omitted.

[0062] According to Modifications 1 and 2, it is possible to achieve the same effects as the above-described embodiment. In particular, in Modifications 1 and 2, it is not necessary to directly attach the sheet member 800 to the electrode body 700, and therefore the sheet member 800 can be easily fixed to the electrode body 700. Even if circumstances arise in which the sheet member 800 must be removed from the electrode body 700, damage to the electrode body 700 can be suppressed.

[0063] In the first modification, the electrode body 700 and the sheet member 800 may be fixed with a connecting member 830. In the first modification, in addition to the fixation with the connecting member 830, the sheet member 800 may be directly attached to the electrode body 700, as in the above embodiment.

[0064] (Variation 3) In the above embodiment, one sheet member 800 covers almost the entire outer periphery (outer periphery surface) of the electrode body main body 710 in the winding axis direction (X-axis direction) of the electrode body 700, but this is not limited to this. The sheet member 800 may cover only a portion of the outer periphery of the electrode body main body 710 in the winding axis direction, or multiple sheet members 800 may be arranged. Figure 10 is a perspective view showing a configuration in which a sheet member 801 according to Variation 3 of this embodiment is fixed to the outer periphery of the electrode body 700.

[0065] 10 , in Modification 3, three sheet members 801 are fixed to the outermost periphery (outer peripheral surface) of the electrode body 700 (electrode body main body 710) with a space between them in the X-axis direction. That is, in Modification 3, multiple sheet members 801 are arranged instead of one, and the multiple sheet members 801 do not cover the entire outermost periphery (outer peripheral surface) of the electrode body main body 710 in the direction of the winding axis (X-axis direction) of the electrode body 700. The other configurations of this modification are the same as those of the above embodiment, and therefore detailed description thereof will be omitted.

[0066] According to the third modification, it is possible to achieve the same effects as the above-described embodiment. In particular, in the third modification, since the sheet members 801 can be divided into multiple sheet members 801 and fixed to the electrode body 700, it is easy to fix the sheet members 801 to the electrode body 700. Because the multiple sheet members 801 are not configured to cover the entire outermost periphery of the electrode body main body 710 in the X-axis direction, there is no need to position the multiple sheet members 801 with high precision. The extension stiffness of each of the multiple sheet members 801 can be set according to the extension stiffness of the portion of the electrode body 700 corresponding to each sheet member 801. In other words, the degree of freedom in designing the sheet members 801 is increased.

[0067] In the third modification, any two or only one of the three sheet members 801 may be fixed to the electrode body 700. The number of sheet members 801 and the width of the sheet members 801 in the X-axis direction are not particularly limited.

[0068] (Variations 4 to 7) In the above embodiment, the sheet member 800 covers the entire outermost periphery of the electrode assembly 700, but this is not limited thereto. The sheet member 800 may cover at least a portion of the outermost periphery of the electrode assembly 700. FIG. 11 is a cross-sectional view showing a configuration in which a sheet member 802 according to Variation 4 of the present embodiment is fixed to the outermost periphery of the electrode assembly 700. FIG. 12 is a cross-sectional view showing a configuration in which a sheet member 803 according to Variation 5 of the present embodiment is fixed to the outermost periphery of the electrode assembly 700. FIG. 13 is a cross-sectional view showing a configuration in which a sheet member 804 according to Variation 6 of the present embodiment is fixed to the outermost periphery of the electrode assembly 700. FIG. 14 is a cross-sectional view showing a configuration in which a sheet member 805 according to Variation 7 of the present embodiment is fixed to the outermost periphery of the electrode assembly 700. FIGS. 11 to 14 correspond to the portions of the electrode assembly 700 and sheet member 800 shown in FIG. 6(a) in the positive direction of the Z axis.

[0069] As shown in FIG. 11 , in Modification 4, the sheet member 802 includes a sheet curved portion 810 in the positive Z-axis direction and a pair of sheet flat portions 823. The pair of sheet flat portions 823 are the portions located at the ends of the pair of sheet flat portions 820 in the positive Z-axis direction in the above embodiment. As a result, the sheet member 802 covers the outermost periphery of the electrode body curved portion 711 in the positive Z-axis direction of the electrode body 700 (electrode body main body portion 710) and the ends of the pair of electrode body flat portions 712 in the positive Z-axis direction, and is fixed to the outermost periphery by adhesive or other bonding. In other words, the sheet member 802 covers the entire outermost periphery of the electrode body curved portion 711 and is positioned across the boundary portion 713 between the electrode body curved portion 711 and the electrode body flat portion 712. The other configuration of this modification is similar to that of the above embodiment, and therefore detailed description thereof will be omitted.

[0070] In the fourth modification, there is no particular limitation on the length of the flat sheet portion 823 in the Z-axis direction. In addition to or instead of the portion in the positive Z-axis direction described above, the sheet member 802 may have a portion in the negative Z-axis direction that has the same configuration as the portion in the positive Z-axis direction described above.

[0071] As shown in FIG. 12 , in the fifth modification, the sheet member 803 includes a pair of curved sheet portions 811 and a pair of flat sheet portions 824. The pair of curved sheet portions 811 are portions located at both ends of the curved sheet portion 810 in the positive Z-axis direction in the Y-axis direction in the above embodiment. The pair of flat sheet portions 824 are portions located at the ends of the flat sheet portions 820 in the positive Z-axis direction in the above embodiment. As a result, the sheet member 803 covers the outermost peripheries of the electrode body 700 (electrode body main body portion 710) at both ends of the curved electrode portion 711 in the positive Z-axis direction and the ends of the flat electrode portions 712 in the positive Z-axis direction, and is fixed to the outermost peripheries by adhesive or other bonding. In other words, the sheet member 803 is disposed across the boundary portion 713 between the curved electrode portion 711 and the flat electrode portion 712. The remaining configuration of this modification is similar to that of the above embodiment, and therefore detailed description thereof will be omitted.

[0072] In the fifth modification, the length of the flat sheet portion 824 in the Z-axis direction is not particularly limited. The sheet member 803 may only have the curved sheet portion 811 and the flat sheet portion 824 in the positive direction of the Y-axis, or the curved sheet portion 811 and the flat sheet portion 824 in the negative direction of the Y-axis. In addition to or instead of the portion in the positive direction of the Z-axis described above, the sheet member 803 may have a portion in the negative direction of the Z-axis that has a configuration similar to the portion in the positive direction of the Z-axis described above.

[0073] 13 , in the sixth modification, the sheet member 804 includes a sheet curved portion 812. The sheet curved portion 812 is the portion that was located in the Y-axis direction central portion (other than the end portion) of the sheet curved portion 810 in the positive Z-axis direction in the above embodiment. As a result, the sheet member 804 covers the outermost periphery of the Y-axis direction central portion (other than the end portion) of the electrode body curved portion 711 in the positive Z-axis direction of the electrode body 700 (electrode body main body portion 710), and is fixed to the outermost periphery by adhesive or other bonding. The other configurations of this modification are the same as those of the above embodiment, and therefore detailed description thereof will be omitted.

[0074] In the sixth modification, the length of the sheet curved portion 812 in the Y-axis direction is not particularly limited. In addition to or instead of the portion in the positive Z-axis direction described above, the sheet member 804 may have a portion in the negative Z-axis direction that has the same configuration as the portion in the positive Z-axis direction described above.

[0075] As shown in Fig. 14, in the seventh modification, the sheet member 805 has a pair of flat sheet portions 825. The pair of flat sheet portions 825 are portions that were located in the central portions (other than the ends) in the Z-axis direction of the pair of flat sheet portions 820 in the above embodiment. As a result, the sheet member 805 covers the outermost periphery of the central portions (other than the ends) in the Z-axis direction of the pair of electrode body flat portions 712 of the electrode body 700 (electrode body main body portion 710), and is fixed to the outermost periphery by adhesion such as adhesive. The other configurations of this modification are the same as those of the above embodiment, and therefore detailed description thereof will be omitted.

[0076] In the seventh modification, the length of the flat sheet portion 825 in the Z-axis direction is not particularly limited. The sheet member 805 may only have the flat sheet portion 825 in the positive Y-axis direction or the flat sheet portion 825 in the negative Y-axis direction.

[0077] According to Modifications 4 to 7, the portions of the electrode body 700 where the sheet members are fixed can be reinforced, thereby suppressing damage to the electrode body 700. During manufacturing, the electrode body 700 may be held with a jig and then the sheet members may be fixed to the electrode body 700. In such cases, the sheet members cannot be fixed to the portions of the electrode body 700 that are held with the jig. In this way, Modifications 4 to 7 allow the sheet members to be selectively fixed to portions of the electrode body 700 that are desired to be reinforced or portions where the sheet members can be fixed. In other words, the electrode body 700 can be reinforced efficiently.

[0078] (Variation 8) The energy storage element 10 may be used in an energy storage device. In this case, the technology of the present invention may be applied to at least one energy storage element 10 included in the energy storage device. FIG. 15 is a plan view showing an example of an energy storage device 12 according to Variation 8 of the present embodiment. As shown in FIG. 15 , a plurality of energy storage units 11 are arranged inside the energy storage device 12. The energy storage unit 11 is composed of a plurality of electrically connected energy storage elements 10. The energy storage device 12 may include a bus bar (not shown) that electrically connects the plurality of energy storage elements 10, a bus bar (not shown) that electrically connects the plurality of energy storage units 11, and the like. The energy storage unit 11 or the energy storage device 12 may include a state monitoring device (not shown) that monitors the state of one or more energy storage elements 10. The energy storage device 12 may include only one energy storage unit 11 (that is, the energy storage unit 11 may be referred to as an energy storage device).

[0079] (Other Modifications) In the above embodiment, the tensile rigidity of the sheet member 800 is higher than the tensile rigidity of both the positive electrode plate 701 and the negative electrode plate 702. However, it is sufficient that the tensile rigidity of the sheet member 800 is higher than the tensile rigidity of either the positive electrode plate 701 or the negative electrode plate 702. In other words, the tensile rigidity of the sheet member 800 may be lower than the tensile rigidity of either the positive electrode plate 701 or the negative electrode plate 702.

[0080] In the above embodiment, one sheet member 800 (one layer) is fixed to the electrode body 700, but multiple sheets (multiple layers) of sheet members 800 may be fixed. In this case, it is sufficient that the tensile rigidity of the multiple sheets (multiple layers) of sheet members 800 is higher than the tensile rigidity of the electrode plates provided in the electrode body 700.

[0081] In the above embodiment, the sheet member first end 821 and the sheet member second end 822 of the sheet member 800 are provided at the Z-axis positive direction end of the sheet flat portion 820 in the Y-axis positive direction, but they may be provided at any position on the sheet member 800. The sheet member first end 821 and the sheet member second end 822 may be provided at the Z-axis negative direction end or the Z-axis central portion of the sheet flat portion 820 in the Y-axis positive direction. The sheet member first end 821 and the sheet member second end 822 may be provided on the sheet flat portion 820 in the Y-axis negative direction, or on the sheet curved portion 810 in the Z-axis positive direction or the Z-axis negative direction.

[0082] In the above embodiment, the sheet member first end 821 and the sheet member second end 822 are arranged with their tips in contact with each other so as not to overlap in the thickness direction, but this is not limited thereto. The sheet member first end 821 and the sheet member second end 822 may also be arranged with their tips spaced apart. The sheet member first end 821 and the sheet member second end 822 may also be arranged overlapping in the thickness direction. In this case, the overlapping portions of the sheet member first end 821 and the sheet member second end 822 may be connected (joined) by adhesion (adhesion, etc.), welding, engagement using a concave-convex structure, press-fitting, etc., to fix the sheet member 800 to the electrode body 700.

[0083] In the above embodiment, the sheet member first end 821 and the sheet member second end 822 of the sheet member 800 are provided at the Z-axis positive end of the sheet flat portion 820 in the Y-axis positive direction. However, the sheet member first end 821 and the sheet member second end 822 do not have to be provided. That is, the sheet member 800 may have a seamless structure. Specifically, the sheet member 800 may be formed as an integrally molded member manufactured by resin molding or the like. In this case, the electrode assembly 700 may be fixed to the electrode assembly 700 by inserting the electrode assembly 700 through an opening in the X-axis direction of the sheet member 800. If the sheet member 800 has a seamless structure and is made of fiber-reinforced plastic, the fibers of the fiber-reinforced plastic will be oriented along the outermost periphery (outer peripheral surface) of the electrode assembly 700. This allows the elongation rigidity of the sheet member 800 to be designed to match the shape of the electrode assembly 700.

[0084] In the above embodiment, the electrode body 700 is a wound electrode body in which the winding axis L is parallel to the lid body 120. However, the electrode body 700 may also be a wound electrode body in which the winding axis L is perpendicular to the lid body 120. In the electrode body 700, the end portion 720 is not limited to a portion that protrudes from the entire end portion of the electrode body main body 710, and may also be a tab portion (a portion where multiple tabs of electrode plates are stacked) that protrudes from a portion of the end portion of the electrode body main body 710.

[0085] Any combination of the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0086] The present invention can be applied to an electric storage device such as a lithium ion secondary battery.

[0087] REFERENCE SIGNS LIST 10 Energy storage element 11 Energy storage unit 12 Energy storage device 100 Container 110 Container body 111 Long side wall portion 120 Lid body 200 Terminal 600 Current collector 700 Electrode body 701 Positive electrode plate 701a Positive electrode current collector foil 701b Positive electrode active material layer 702 Negative electrode plate 702a Negative electrode current collector foil 702b Negative electrode active material layer 703, 704 Separator 710 Electrode body body portion 711 Electrode body curved portion 712 Electrode body flat portion 713 Boundary portion 720 End portion 800, 801, 802, 803, 804, 805 Sheet member 810, 811, 812 Sheet curved portion 820, 823, 824, 825 Sheet flat portion 821: First end of sheet member 822: Second end of sheet member 830: Connection member

Claims

1. An energy storage element comprising: an electrode body formed by winding electrode plates; and a sheet member fixed to the outermost periphery of the electrode body, wherein the sheet member has a higher tensile rigidity than the electrode plates.

2. The energy storage element according to claim 1, wherein the electrode body has curved portions and flat portions formed by winding the electrode plates, and the sheet member is arranged across the boundary between the curved portions and the flat portions.

3. The energy storage device according to claim 2, wherein the sheet member covers the entire outermost periphery of the curved portion.

4. The energy storage element according to claim 3, wherein the sheet member covers the entire outermost periphery of the electrode body.

5. The energy storage device according to any one of claims 1 to 4, wherein the sheet member is formed of fiber-reinforced plastic.

Images