Power storage device

Abstract

This power storage device comprises a power storage element and a spacer adjacent to the power storage element. The power storage element is provided with: an electrode body in which an electrode plate is wound and which is provided with a flat part and a pair of curved parts that sandwich the flat part; and a container which accommodates the electrode body. The spacer is provided with a pair of first regions that are respectively opposite from one end and another end of the flat part in the direction in which the flat part and the curved parts are arranged, and a second region that is opposite from an intermediate part between said one end and said other end. The rigidity of the first regions is lower than the rigidity of the second region.

Description

Energy storage device

[0001] This invention relates to an energy storage device.

[0002] Conventionally, a battery pack is known in which multiple non-aqueous electrolytic secondary batteries are arranged in a grid with a spacer placed between two adjacent non-aqueous electrolytic secondary batteries (see Patent Document 1). The non-aqueous electrolytic secondary battery is provided with a wound electrode body in which a positive electrode plate and a negative electrode plate are wound with a separator in between, and a battery case that houses the wound electrode body.

[0003] Japanese Patent Publication No. 2019-160587

[0004] When a non-aqueous electrolytic secondary battery is subjected to repeated charging and discharging, the wound electrode body expands inside the battery case. This expansion causes uneven load distribution between the flat portion of the wound electrode body and the pair of curved portions flanking it. This uneven load distribution may lead to deterioration of the wound electrode body.

[0005] This invention was made by the present inventors by newly focusing on the above-mentioned problems, and aims to provide an energy storage device capable of suppressing the deterioration of electrode bodies.

[0006] An energy storage device according to one aspect of the present invention comprises an energy storage element and a spacer adjacent to the energy storage element, wherein the energy storage element comprises an electrode body on which an electrode plate is wound and which has a flat portion and a pair of curved portions sandwiching the flat portion, and a container for housing the electrode body, wherein the spacer comprises a pair of first regions facing one end and the other end of the flat portion and a second region facing the intermediate portion between the one end and the other end in the direction in which the flat portion and the curved portion are aligned, and the rigidity of the first regions is lower than that of the second region.

[0007] According to the present invention, it is possible to provide an energy storage device that can suppress the deterioration of the electrode body.

[0008] Figure 1 is a perspective view showing the external appearance of an energy storage device according to an embodiment. Figure 2 is an exploded perspective view showing each component when the energy storage device according to an embodiment is disassembled. Figure 3 is a perspective view showing each component when the energy storage element according to an embodiment is disassembled. Figure 4 is a plan view showing a spacer according to an embodiment. Figure 5 is a cross-sectional view showing the positional relationship between the spacer and the internal structure of the energy storage element according to an embodiment. Figure 6 is a cross-sectional view showing the positional relationship between the spacer and the internal structure of the energy storage element according to Modification 1. Figure 7 is a cross-sectional view showing the positional relationship between the spacer and the internal structure of the energy storage element according to Modification 2. Figure 8 is a plan view showing the spacer according to Modification 2. Figure 9 is a plan view showing the spacer according to Modification 3.

[0009] (1) An energy storage device according to one aspect of the present invention comprises an energy storage element and a spacer adjacent to the energy storage element, wherein the energy storage element comprises an electrode body on which an electrode plate is wound and which has a flat portion and a pair of curved portions sandwiching the flat portion, and a container for housing the electrode body, wherein the spacer comprises a pair of first regions facing one end and the other end of the flat portion in the direction in which the flat portion and the curved portion are aligned, and a second region facing the intermediate portion between the one end and the other end, wherein the rigidity of the first regions is lower than the rigidity of the second region.

[0010] When the electrode body expands, the load tends to be greater on the curved portion than on the flat portion. In the energy storage device described in (1) above, the first region of the spacer, which has low rigidity, faces both ends of the flat portion that is close to the curved portion. Therefore, the deformation of the first region can mitigate the load difference between the curved portion and the flat portion. Consequently, load unevenness between the flat portion and the curved portion can be suppressed, and deterioration of the electrode body caused by load unevenness can be suppressed.

[0011] (2) In the energy storage device described in (1) above, the elastic modulus of the material forming the first region may be smaller than the elastic modulus of the material forming the second region.

[0012] According to the energy storage device described in (2) above, the elastic modulus of the material forming the first region is smaller than that of the material forming the second region, so the rigidity of the first region is lower than that of the second region. In this way, the deterioration of the electrode body caused by load unevenness can be suppressed by the difference in materials, and the shape of the spacer can be simplified.

[0013] (3) In the energy storage device described in (1) or (2) above, the thickness of the first region may be smaller than the thickness of the second region.

[0014] According to the energy storage device described in (3) above, the thickness of the first region is smaller than the thickness of the second region, so that the rigidity of the first region is lower than that of the second region. For this reason, even if the spacer is made of a uniform material overall, deterioration of the electrode body caused by load unevenness can be suppressed.

[0015] (4) In the energy storage device described in any one of (1) to (3) above, the spacer may be a foam.

[0016] According to the energy storage device described in (4) above, since the spacer is made of foam, it can adequately resist the expansion of the energy storage element and apply an appropriate load to the inside of the container. This further suppresses uneven load distribution in the electrode body.

[0017] (5) In the energy storage device described in any one of (1) to (4) above, the second region may surround the first region.

[0018] According to the energy storage device described in (5) above, since the first region is surrounded by a highly rigid second region, the rigidity of the spacer itself can be ensured while making only the first region easily deformable.

[0019] (Embodiments) Hereinafter, an energy storage device according to an embodiment (including its modifications) of the present invention will be described with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples and are not intended to limit the present invention. In each figure, dimensions, etc., are not strictly illustrated. In each figure, the same or similar components are denoted by the same reference numeral. The names of each component (each component) in this embodiment are those of this embodiment and may differ from the names of each component (each component) in the background art.

[0020] In the following description and drawings, the longitudinal direction of the energy storage element and the direction along the winding axis of the electrode body provided on the energy storage element are defined as the X-axis direction. The thickness direction of the container of the energy storage element is defined as the Y-axis direction. The direction in which the bottom surface of the container body and the top surface of the lid are aligned, or the vertical direction, is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in this embodiment). Depending on the usage, the Z-axis direction may not be the vertical direction, but for the sake of explanation below, the Z-axis direction will be described as the vertical direction. In the following description, when "insulation" is used, it means "electrical insulation". An insulating material has a volume resistivity of 1 × 10⁻⁶ ６ Preferably Ωm or more, 1 × 10 ７ Ωm or greater is more preferable, 1 × 10 １０ A value of Ωm or greater is even more preferable.

[0021] In the following explanation, the X-axis positive direction refers to the direction of the X-axis arrow, and the X-axis negative direction refers to the opposite direction. The same applies to the Y-axis and Z-axis directions. Furthermore, expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where they are not strictly those directions or orientations. Two directions being orthogonal does not only mean that the two directions are perfectly orthogonal, but also that they are substantially orthogonal, that is, they may include a difference of a few percent.

[0022] [Energy Storage Device] First, the general configuration of the energy storage device 1 in this embodiment will be described. Figure 1 is a perspective view showing the external appearance of the energy storage device 1 according to this embodiment. Figure 2 is an exploded perspective view showing each component when the energy storage device 1 according to this embodiment is disassembled.

[0023] The energy storage device 1 is a device that can charge electricity from an external source and discharge electricity to the outside, and in this embodiment, it has a substantially rectangular parallelepiped shape. The energy storage device 1 is used as a battery for driving or starting the engine of mobile bodies such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, automated guided vehicles (AGVs), or railway vehicles for electric railways. Examples of automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicles. Examples of railway vehicles for electric railways include electric trains, monorails, linear motor cars, and hybrid trains equipped with both diesel engines and electric motors. The energy storage device 1 may also be used as a stationary battery for household or commercial use.

[0024] As shown in Figure 1, the energy storage device 1 includes an outer casing 2. As shown in Figure 2, the outer casing 2 houses a plurality of energy storage elements 10, a plurality of spacers 20, and a plurality of busbars (not shown), etc. The energy storage device 1 also includes external terminals 11 (positive external terminal and negative external terminal) for electrical connection to an external device. In addition to the above components, the energy storage device 1 may also include restraining members (end plates, side plates, etc.) for restraining the plurality of energy storage elements 10, busbar holders for holding the busbars, busbar covers, a circuit board for monitoring or controlling the charging and discharging states of the energy storage elements 10, relays, fuses, shunt resistors, connectors, and other electrical components.

[0025] The outer casing 2 is a rectangular parallelepiped (box-shaped) container (module case) that constitutes the outer casing (housing, shell) of the energy storage device 1. A rectangular parallelepiped is a hexahedron in which all faces are rectangles or squares. The outer casing 2 is positioned outside the plurality of energy storage elements 10 and the plurality of spacers 20, etc., and fixes the plurality of energy storage elements 10 and the plurality of spacers 20, etc. in predetermined positions and protects them from impacts, etc. The outer casing 2 is a metal outer casing made of a metal material such as aluminum, aluminum alloy, stainless steel, iron, plated steel sheet, etc. The outer casing 2 may also be made of an insulating material such as any resin material that can be used for the spacers 20 described later. If the outer casing 2 is made of a conductive material, the inner surface of the outer casing 2 may be covered with an insulating material to ensure insulation from the energy storage elements 10.

[0026] As shown in Figure 2, the exterior body 2 comprises an exterior body main body 30 that constitutes the main body of the exterior body 2, and an exterior body cover 40 that constitutes the cover of the exterior body 2. The exterior body main body 30 is a bottomed rectangular cylindrical housing (enclosure) with an opening 31 formed in the Z-axis positive direction, and houses a plurality of energy storage elements 10 and a plurality of spacers 20, etc.

[0027] Specifically, the outer casing body 30 comprises a bottom wall 32 and side walls 33. The bottom wall 32 is a flat, rectangular portion located at the end of the outer casing body 30 in the negative Z-axis direction. The side walls 33 are rectangular annular walls extending from the outer edge in the positive Z-axis direction and are continuously provided around the entire circumference of the bottom wall 32. The inside of the side walls 33 is an opening 31. The outer casing body 30 may have an exhaust port for exhausting gas discharged from the energy storage element 10 to the outside of the outer casing body 2.

[0028] The outer casing cover 40 is a flat, rectangular member that closes the rectangular opening 31 of the outer casing body 30. The outer casing body 30 and the outer casing cover 40 are sealed by joining them together by welding, welding, screwing, etc. The outer casing body 30 and the outer casing cover 40 may be made of the same material or of different materials. On the upper surface of the outer casing cover 40, a pair of external terminals 11 are arranged in the Y-axis direction at the end in the X-axis positive direction.

[0029] The energy storage element 10 is a secondary battery (single cell) capable of charging and discharging electricity, and more specifically, a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is a non-pouch type battery. 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 a capacitor. The energy storage element 10 may be a primary battery instead of a secondary battery. Furthermore, the energy storage element 10 may be an all-solid-state lithium battery using a solid electrolyte, or a polymer lithium battery. Details of the energy storage element 10 will be described later.

[0030] The spacer 20 is a flat plate-shaped member that is positioned alongside the energy storage element 10 in the Y-axis direction and insulates and / or heats the energy storage element 10 from other members. The spacer 20 is an insulating plate or heatsink plate that is positioned adjacent to the energy storage element 10 in the positive or negative Y-axis direction of the energy storage element 10 and insulates and / or heats the energy storage elements 10 from each other or from the energy storage element 10 to the outer casing 2.

[0031] Of the spacers 20, the spacers 20 placed between adjacent energy storage elements 10 are intermediate spacers, and the two spacers 20 placed at the ends of the multiple energy storage elements 10 in the Y-axis direction are end spacers. Details of the spacers 20 will be described later.

[0032] The busbar is connected (joined) to the terminals 300 of multiple energy storage elements 10. Specifically, the multiple busbars connect the terminals 300 of the multiple energy storage elements 10 to each other, and also electrically connect the terminals 300 of the end energy storage elements 10 to the external terminals 11. In other words, one busbar may connect the terminals 300 of multiple energy storage elements 10, or it may connect the terminals 300 to the external terminals 11. The busbar and the terminals 300 are connected (joined) by welding or the like, but the connection method is not particularly limited. The busbar is made of a conductive material made of metal such as aluminum, aluminum alloy, copper, copper alloy, nickel, or a combination thereof, or a conductive material other than metal.

[0033] [Energy Storage Element] Next, the configuration of the energy storage element 10 in this embodiment will be described. Figure 3 is a perspective view showing the components of the energy storage element 10 according to this embodiment when disassembled. As shown in Figure 3, the energy storage element 10 comprises a container 100, a pair of terminals 300, and a pair of external gaskets 400. Inside the container 100 are a pair of internal gaskets 500, a pair of current collectors 600, and a pair of electrode bodies 700. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but it is not shown in the illustration. As for the electrolyte, there are no particular restrictions on the type as long as it does not impair the performance of the energy storage element 10, and various types can be selected. In addition to the above components, spacers placed to the side, above, or below the electrode bodies 700, insulating films that enclose the electrode bodies 700, etc., may also be arranged.

[0034] Container 100 is a container having an external shape based on a rectangular parallelepiped. Specifically, container 100 has an external shape that is elongated in the X-axis direction. Container 100 comprises a container body 110 and a lid 120, and the container body 110 and the lid 120 are combined to form a rectangular parallelepiped.

[0035] The container body 110 is a rectangular box-shaped body with an open Z-axis positive direction. The container body 110 comprises a rectangular bottom plate that is elongated in the X-axis direction and a rectangular tubular wall portion that extends from the outer edge of the bottom plate in the Z-axis positive direction. The lid 120 is a rectangular sheet metal that is elongated in the X-axis direction and closes the opening of the container body 110. Through holes 121 are formed at both ends of the lid 120 in the X-axis direction, through which each terminal 300 passes.

[0036] Although not shown in the illustration here, the lid 120 has a liquid injection section and a gas discharge valve. The liquid injection section is for injecting the electrolyte into the container 100 during the manufacturing of the energy storage element 10. The gas discharge valve is a safety valve that releases pressure if the pressure inside the container 100 rises excessively.

[0037] With such a configuration, after the electrode body 700 and the like are accommodated inside the container body 110, the container body 110 and the lid body 120 are joined by welding or the like, so that the interior is sealed. The material of the container 100 (the container body 110 and the lid body 120) is not particularly limited, but for example, weldable metals such as stainless steel, aluminum, aluminum alloy, iron, and plated steel sheets are preferred.

[0038] The terminal 300 is a terminal (the positive electrode terminal 310 and the negative electrode terminal 320) that is electrically connected to the electrode body 700 via the current collector 600. That is, the terminal 300 is a metal member for leading out the electricity stored in the electrode body 700 to the external space of the energy storage element 10 and introducing electricity into the internal space of the energy storage element 10 to store electricity in the electrode body 700. Among the pair of terminals 300, the terminal 300 in the negative X-axis direction is the positive electrode terminal 310, and the terminal 300 in the positive X-axis direction is the negative electrode terminal 320. The material of the terminal 300 is not particularly limited, but the terminal 300 is formed of a conductive member such as aluminum, aluminum alloy, copper, or copper alloy. The terminal 300 is connected (joined) to the current collector 600 and attached to the lid body 120 by caulking, welding, or the like.

[0039] In the present embodiment, the terminal 300 has a terminal main body portion 330 and a shaft portion 340 protruding from the terminal main body portion 330. The terminal main body portion 330 is a rectangular flat plate-like portion protruding outward from the lid body 120. The shaft portion 340 is caulked while passing through the through-hole 121 of the lid body 120, the external gasket 400, the internal gasket 500, and the current collector 600, and thus is connected (joined) to the current collector 600.

[0040] The current collector 600 is arranged one by one on both sides of the pair of electrode bodies 700 in the X-axis direction, and is connected (joined) to each electrode body 700 and each terminal 300, and is a current collecting member (positive electrode current collector 610 and negative electrode current collector 620) having conductivity for electrically connecting the electrode body 700 and the terminal 300. The material of the current collector 600 is not particularly limited. For example, the positive electrode current collector 610 is formed of a conductive member such as aluminum or an aluminum alloy, similar to the positive electrode current collecting foil of the electrode body 700 described later, and the negative electrode current collector 620 is formed of a conductive member such as copper or a copper alloy, similar to the negative electrode current collecting foil of the electrode body 700 described later. Among the pair of current collectors 600, the current collector 600 in the minus X-axis direction is the positive electrode current collector 610, and the current collector 600 in the plus X-axis direction is the negative electrode current collector 620.

[0041] Specifically, the current collector 600 includes a base portion 601 and a pair of leg portions 602, and these are integrally formed by sheet metal. The base portion 601 is a flat plate portion parallel to the XY plane, and includes a through hole 603 through which the shaft portion 340 of the terminal 300 penetrates. The pair of leg portions 602 are arranged at positions sandwiching the base portion 601 in the Y-axis direction, and are flat plate-like portions extending in the minus Z-axis direction from the base portion 601. Among the pair of leg portions 602, the electrode body 700 in the plus Y-axis direction is connected (joined) to the leg portion 602 in the plus Y-axis direction, and the electrode body 700 in the minus Y-axis direction is connected (joined) to the leg portion 602 in the minus Y-axis direction.

[0042] The external gasket 400 is a plate-shaped and rectangular insulating seal member that is disposed between the lid 120 of the container 100 and the terminal 300, insulates and seals between the lid 120 and the terminal 300. The internal gasket 500 is a plate-shaped and rectangular insulating seal member that is disposed between the lid 120 and the current collector 600, insulates and seals between the lid 120 and the current collector 600. The external gasket 400 and the internal gasket 500 are formed of a resin having electrical insulation properties such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), tetrafluoroethylene / perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), ABS resin, or a composite material obtained by adding a filler to these.

[0043] The pair of electrode bodies 700 are arranged side by side in the Y-axis direction. Each electrode body 700 includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate is an electrode plate (electrode sheet) in which a positive electrode active material layer is disposed on both surfaces of a positive electrode current collector foil that is a long strip-shaped metal foil. Aluminum or an aluminum alloy or the like is used for the positive electrode current collector foil. The negative electrode plate is an electrode plate (electrode sheet) in which a negative electrode active material layer is disposed on both surfaces of a negative electrode current collector foil that is a long strip-shaped metal foil. Copper or a copper alloy or the like is used for the negative electrode current collector foil. As the positive electrode active material used in the positive electrode active material layer and the negative electrode active material used in the negative electrode active material layer, any known material can be appropriately used as long as it is a material capable of occluding and releasing ions by an electrochemical reaction.

[0044] As the positive electrode active material, LiMPO ４ 、LiMSiO ４ 、LiMBO ３ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) and other polyanion compounds, lithium titanate, LiMn ２ O ４ and LiMn １．５ Ni０．５ O ４ spinel-type lithium manganese oxides such as α-NaFeO ２ LiMO having a type crystal structure ２ Lithium transition metal oxides such as (where M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) can be used. Examples of negative electrode active materials include lithium metal, alloys capable of intercalating and releasing lithium, carbon materials (graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature calcined carbon, amorphous carbon, etc.), and silicon oxides.

[0045] The separator is a microporous sheet made of resin. Any known material can be used as the separator material, as long as it does not impair the performance of the energy storage element 10. As the separator, a woven fabric, nonwoven fabric, or a synthetic resin microporous membrane made of polyolefin resin such as polyethylene, which is insoluble in organic solvents, may be used.

[0046] The electrode body 700 is formed by winding together a positive electrode plate, a negative electrode plate, and a separator. Specifically, the electrode body 700 is formed by stacking and winding together a negative electrode plate, a separator, a positive electrode plate, and a separator in that order. In this embodiment, the positive electrode plate, the negative electrode plate, and the separator are wound around a winding axis L extending in the X-axis direction to form a wound-type electrode body 700. The winding axis L is a hypothetical axis that serves as the central axis when winding the positive electrode plate, the negative electrode plate, and the separator. In this embodiment, the winding axis L is a straight line parallel to the X-axis direction that passes through the center of the electrode body 700.

[0047] The end of the positive electrode plate in the negative X-axis direction protrudes from the negative electrode plate in the negative X-axis direction. This end of the positive electrode plate in the negative X-axis direction is the portion where the positive electrode active material layer is not present and the positive electrode current collector foil is exposed (the portion where the positive electrode active material layer is not formed).

[0048] The end of the negative electrode plate in the positive X-axis direction protrudes from the positive electrode plate in the positive X-axis direction. This end of the negative electrode plate in the positive X-axis direction is the portion where the negative electrode active material layer is not present and the negative electrode current collector foil is exposed (the portion where the negative electrode active material layer is not formed).

[0049] When the positive electrode plate, the negative electrode plate, and the separator are wound together, the portion of the positive electrode plate that does not have a positive electrode active material layer protrudes from the end face (one end face) in the negative X-axis direction of the main body 710 and overlaps with it. This overlapping portion is the positive electrode connection portion 721. On the other hand, the portion of the negative electrode plate that does not have a negative electrode active material layer protrudes from the end face (the other end face) in the positive X-axis direction of the main body 710 and overlaps with it. This overlapping portion is the negative electrode connection portion 722.

[0050] Thus, the electrode body 700 comprises a main body portion 710 that constitutes the body of the electrode body 700, and a positive electrode connection portion 721 and a negative electrode connection portion 722 that protrude from each end face of the main body portion 710 in the X-axis direction.

[0051] The main body portion 710 is an elongated cylindrical portion formed by winding together a portion of the positive electrode plate on which the positive electrode active material layer is arranged (formed, coated), a portion of the negative electrode plate on which the negative electrode active material layer is arranged (formed, coated), and a separator. The region of the main body portion 710 in which at least one of the positive electrode active material layer and the negative electrode active material layer is laminated is called the active material layer forming portion.

[0052] The main body 710 comprises a flat portion 711 and a pair of curved portions 712 that sandwich the flat portion 711 in the Z-axis direction (see Figure 4). The flat portion 711 and the pair of curved portions 712 are arranged side by side in the Z-axis direction. In other words, the direction in which the flat portion 711 and the pair of curved portions 712 are aligned is the Z-axis direction.

[0053] The flat portion 711 is a flat area parallel to the XZ plane that connects the ends of the pair of curved portions 712 when viewed in the X-axis direction. In the flat portion 711, the wound positive electrode plate, negative electrode plate, and separator are stacked in the Y-axis direction. Since the flat portion 711 is the main part of the electrode body 700, the stacking direction of each electrode plate in this flat portion 711 (Y-axis direction) can be referred to as the stacking direction of the electrode plates in the electrode body 700.

[0054] Each curved portion 712 is a part that protrudes in a curved shape in the Z-axis direction. When viewed from the X-axis direction, each curved portion 712 is curved in the shape of a semicircular arc. Each curved portion 712 does not have to be a perfect semicircular arc; it may be an arc shape in which the semicircle is somewhat flattened.

[0055] [Spacer] Figure 4 is a plan view showing a spacer 20 according to the embodiment. Figure 5 is a cross-sectional view showing the positional relationship between the spacer 20 according to the embodiment and the internal structure of the energy storage element 10. In Figure 4, the outer shape of the main body portion 710 of the electrode body 700 is shown by the dashed line L10. In Figure 5, the energy storage element 10 and a pair of spacers 20 that sandwich the energy storage element 10 in the Y-axis direction are shown.

[0056] As shown in Figures 4 and 5, the spacer 20 is formed in the shape of a rectangular plate when viewed in the Y-axis direction, and its outer shape and size correspond to the container 100 of the energy storage element 10. The spacer 20 comprises a pair of first regions 21 and 22, and a second region 23 that surrounds each of the first regions 21 and 22.

[0057] The pair of first regions 21 and 22 are arranged in the flat portion 711 of the main body 710, corresponding to both ends in the Z-axis direction. Specifically, the pair of first regions 21 and 22 are spaced apart in the Z-axis direction. The first region 21 in the Z-axis positive direction is positioned opposite one end 713 in the Z-axis positive direction of the flat portion 711. The first region 21 is formed in a rectangular shape extending in the X-axis direction, corresponding to one end 713. The Z-axis positive end of the first region 21 substantially coincides with the boundary between the Z-axis positive curved portion 712 and the flat portion 711. The Z-axis direction length d11 of the first region 21 is greater than the Z-axis direction length Dz11 of the curved portion 712.

[0058] The first region 22 in the negative Z-axis direction is positioned opposite the other end 714 of the flat portion 711 in the negative Z-axis direction. The first region 22 is formed in a rectangular shape that extends in the X-axis direction, corresponding to the other end 714. The end of the first region 22 in the negative Z-axis direction substantially coincides with the boundary between the curved portion 712 and the flat portion 711 in the negative Z-axis direction. The length d12 of the first region 22 in the Z-axis direction is greater than the length Dz12 of the curved portion 712 in the Z-axis direction.

[0059] The second region 23 is the region of the spacer 20 excluding the pair of first regions 21 and 22 when viewed in the Y-axis direction. The second region 23 as a whole is a plane that aligns with the XZ plane. The intermediate region 231 between the pair of first regions 21 and 22 in the second region 23 is opposite the intermediate portion 715 between one end 713 and the other end 714 of the flat portion 711.

[0060] The spacer 20 is formed from the same material as a whole. Specifically, the spacer 20 is made of foam. Examples of foam include expanded polyethylene, but it is not limited to this as long as it is an insulating foam.

[0061] As shown in Figure 5, the thickness of the first regions 21 and 22 is smaller than the thickness of the second region 23. Specifically, on the main surface of the spacer 20 facing the energy storage element 10, the first regions 21 and 22 are recessed relative to the second region 23. Similarly, on the main surface of the spacer 20 opposite to the energy storage element 10, the first regions 21 and 22 are recessed relative to the second region 23. The bottom surfaces of the first regions 21 and 22 are planes that are aligned with the XZ plane as a whole. The amount of recession (depth in the Y-axis direction) of the first regions 21 and 22 should be between 0.1 mm and 1.0 mm.

[0062] As mentioned above, since the spacer 20 is formed from the same material as a whole, the rigidity of the first region 21 and 22 and the rigidity of the second region 23 differ due to the difference in thickness. Specifically, the rigidity of the first region 21 and 22, which is thinner, is lower than the rigidity of the second region 23, which is thicker. For this reason, the first region 21 and 22 are more easily deformed than the second region 23.

[0063] When the electrode body 700 expands, uneven load distribution may occur between the flat portion 711 and the curved portion 712. Specifically, the load becomes greater in the curved portion 712 than in the flat portion 711. This load difference becomes particularly noticeable at the boundary between the curved portion 712 and the flat portion 711.

[0064] In this embodiment, the first regions 21 and 22, which face one end 713 and the other end 714 of the flat portion 711, are more easily deformed than the second region 23. Therefore, the expansion of the electrode body 700 is received by the first regions 21 and 22 via the container 100, causing them to deform and absorbing and mitigating load unevenness.

[0065] In particular, in this embodiment, since the spacer 20 is made of foam, it appropriately resists the expansion of the container 100 and can apply an appropriate load to the inside of the container 100. This is advantageous in suppressing uneven load distribution on the electrode body 700.

[0066] [Effects] As described above, according to the embodiment, the first regions 21 and 22 of the spacer 20, which have low rigidity, face both ends (one end 713 and the other end 714) of the flat portion 711 of the electrode body 700 that is close to the curved portion 712. As a result, the first regions 21 and 22 deform, thereby mitigating the load on the curved portion 712. Therefore, load unevenness between the flat portion 711 and the curved portion 712 can be suppressed, and deterioration of the electrode body 700 caused by load unevenness can be suppressed.

[0067] Because the thickness of the first regions 21 and 22 is smaller than the thickness of the second region 23, the rigidity of the first regions 21 and 22 is lower than that of the second region 23. Therefore, even with a spacer made of a uniformly homogeneous material, deterioration of the electrode body 700 caused by load unevenness can be suppressed.

[0068] Since the spacer 20 is made of foam, it can adequately resist the expansion of the energy storage element 10 and apply an appropriate load to the inside of the container 100. This further suppresses uneven load distribution on the electrode body 700.

[0069] Since the first regions 21 and 22 are surrounded by the highly rigid second region 23, the rigidity of the spacer 20 itself is ensured while making it easier to deform only the first regions 21 and 22.

[0070] In this case, if multiple electrode bodies 700 are housed in the container 100 so that their flat portions 711 face each other, the unevenness of the load on each electrode body 700 becomes significant. Even in such a case, the spacer 20 suppresses the unevenness of the load on each electrode body 700, which is preferable.

[0071] (Description of Modifications) The following describes various modifications of the above embodiment. In the following description, parts that are the same as those in the above embodiment or other modifications may be denoted by the same reference numerals and their descriptions may be omitted.

[0072] [Modification 1] Figure 6 is a cross-sectional view showing the positional relationship between the spacer 20A and the internal structure of the energy storage element 10 according to Modification 1. Figure 6 corresponds to Figure 5.

[0073] As shown in Figure 6, the spacer 20A has a pair of main surfaces that are planar as a whole. In other words, there is no step between the first region 21a, 22a and the second region 23a. Furthermore, in the spacer 20A, the first material forming the first region 21a, 22a and the second material forming the second region 23a are different. The elastic modulus of the first material is smaller than that of the second material. Specifically, the first and second materials are foamed polyethylene, but the second material has a higher density than the first material. The second material, with its higher density, has fewer air bubbles than the second material, and therefore has a higher elastic modulus.

[0074] Thus, since the elastic modulus of the first material forming the first region 21a and 22a is smaller than that of the second material forming the second region 23a, the stiffness of the first region 21a and 22a is lower than that of the second region 23a. In this way, deterioration of the electrode body 700 caused by load unevenness can be suppressed by the difference in materials, and the shape of the spacer 20A can be simplified.

[0075] Furthermore, it is preferable that the compressive stress of the second material at 10% strain is between 0.2 MPa and 1.2 MPa, and the compressive stress of the first material at 10% strain is in the range of 0.1 MPa and 0.6 MPa, which is smaller than the compressive stress of the second material at 10% strain. When this condition is met, load unevenness of the electrode body 700 can be suppressed more reliably.

[0076] [Modification 2] Figure 7 is a cross-sectional view showing the positional relationship between the spacer 20B and the internal structure of the energy storage element 10B according to Modification 2. Figure 8 is a plan view showing the spacer 20B according to Modification 2. Figure 7 corresponds to Figure 5, and Figure 8 corresponds to Figure 4. In Figure 8, the outer shape of the main body portion 710b of the electrode body 700b is shown by the dashed line L10.

[0077] As shown in Figure 7, each electrode body 700b of the energy storage element 10B is housed in the container 100 with its winding axis aligned with the Z-axis direction. Therefore, the flat portion 711b and the pair of curved portions 712b of each electrode body 700b are arranged side by side in the X-axis direction. In other words, the alignment direction of the flat portion 711b and the pair of curved portions 712b is in the X-axis direction.

[0078] As shown in Figures 7 and 8, the pair of first regions 21b and 22b provided in the spacer 20B are arranged in the flat portion 711b corresponding to both ends in the X-axis direction. Specifically, the pair of first regions 21b and 22b are spaced apart in the X-axis direction. The first region 21b in the negative X-axis direction is positioned opposite to one end 713b in the negative X-axis direction of the flat portion 711b. The first region 21b is formed in a rectangular shape extending in the Z-axis direction, corresponding to one end 713b. The first region 22b in the positive X-axis direction is positioned opposite to the other end 714b in the positive X-axis direction of the flat portion 711b. The first region 22b is formed in a rectangular shape extending in the Z-axis direction, corresponding to the other end 714b.

[0079] The second region 23b is the region of the spacer 20B excluding the pair of first regions 21b and 22b when viewed in the Y-axis direction. The intermediate region 231b between the pair of first regions 21b and 22b in the second region 23b is opposite the intermediate portion 715b between one end 713b and the other end 714b of the flat portion 711b.

[0080] Even in this case, the first regions 21b and 22b of the spacer 20B, which have low rigidity, face both ends (one end 713b and the other end 714b) of the flat portion 711b of the electrode body 700b that is close to the curved portion 712b. As a result, the deformation of the first regions 21b and 22b can alleviate the load on the curved portion 712b. Therefore, uneven load distribution between the flat portion 711b and the curved portion 712b can be suppressed, and deterioration of the electrode body 700b caused by uneven load distribution can be suppressed.

[0081] [Modification 3] Figure 9 is a plan view showing the spacer 20C according to Modification 3. Figure 9 corresponds to Figure 4. As shown in Figure 9, the first regions 21c and 22c are formed along the entire length of the spacer 20C in the X-axis direction. Therefore, the second region 23c is separated by the first regions 21c and 22c and does not surround the first regions 21c and 22c. Thus, the second region 23c does not have to surround the first regions 21c and 22c.

[0082] (Other) Although an embodiment of the present invention (including its modifications; the same applies hereinafter) of an energy storage device has been described above, the present invention is not limited to the above embodiments. The embodiments disclosed herein are illustrative in all respects, and the scope of the present invention includes all modifications in the sense and scope equivalent to the claims.

[0083] In the above embodiment, a case in which a pair of electrode bodies 700 are housed in the container 100 was illustrated, but the number of electrode bodies 700 may be one or three or more.

[0084] In the above embodiment, a spacer made of foam was exemplified, but a spacer made of a material other than foam may also be used.

[0085] In the above embodiment, the stiffness of the first region and the stiffness of the second region were made different by varying their thickness or materials, but the stiffness of the first region and the stiffness of the second region may be made different by other methods. Other methods include varying the cross-sectional shape, varying the surface shape, varying the density of bubbles, varying the microstructure, and combining multiple of the above methods.

[0086] The present invention also includes forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples.

[0087] This invention can be applied to energy storage devices equipped with energy storage elements such as lithium-ion secondary batteries.

[0088] 1 Energy storage device 2 Outer casing 10, 10B Energy storage element 11 External terminals 20, 20A, 20B, 20C Spacers 21, 21a, 21b, 21c, 22, 22a, 22b, 22c First region 23, 23a, 23b, 23c Second region 100 Container 231, 231b Intermediate region 300 Terminal 400 External gasket 500 Internal gasket 600 Current collector 700, 700b Electrode body 710, 710b Main body 711, 711b Flat section 712, 712b Curved section 713, 713b One end 714, 714b Other end 715, 715b Intermediate section L Winding shaft

Claims

1. An energy storage device comprising: an energy storage element; and a spacer adjacent to the energy storage element, wherein the energy storage element comprises: an electrode body on which an electrode plate is wound and which has a flat portion and a pair of curved portions sandwiching the flat portion; and a container for housing the electrode body; and the spacer comprises: a pair of first regions facing one end and the other end of the flat portion in the direction in which the flat portion and the curved portion are aligned, and a second region facing the intermediate portion between the one end and the other end, wherein the rigidity of the first regions is lower than that of the second region.

2. The energy storage device according to claim 1, wherein the elastic modulus of the material forming the first region is smaller than the elastic modulus of the material forming the second region.

3. The energy storage device according to claim 1, wherein the thickness of the first region is smaller than the thickness of the second region.

4. The energy storage device according to claim 1 or 2, wherein the spacer is a foam.

5. The energy storage device according to claim 1 or 2, wherein the second region surrounds the first region.

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