Electric power storage element

Abstract

An electric power storage element comprises: a plurality of electrode bodies around which electrode plates are wound, and which are each provided with a flat portion and a pair of curved portions that sandwich the flat portion; a container that accommodates the plurality of electrode bodies that are arranged so that the flat portions face each other; a plurality of first elastic portions that are individually provided at the center of each of the plurality of electrode bodies; and a plurality of second elastic portions that are provided at positions that sandwich the flat portions of the plurality of electrode bodies.

Description

Energy storage element

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

[0002] Patent Document 1 discloses a secondary battery comprising a wound electrode body in which a positive electrode and a negative electrode are wound around a winding axis with a separator in between, and a battery container that houses the wound electrode body.

[0003] Japanese Patent Publication No. 2017-27681

[0004] Repeated charging and discharging causes the wound electrode to expand and be compressed by the container. This is particularly noticeable in the flat sections of the wound electrode, where excessive pressure may be applied, potentially leading to damage.

[0005] This invention was made by the present inventors by newly focusing on the above-mentioned problems, and aims to provide an energy storage element that can suppress excessive pressure on the flat portion of the electrode body.

[0006] An energy storage element according to one aspect of the present invention comprises a plurality of electrode bodies, each having a flat portion and a pair of curved portions sandwiching the flat portion, an electrode plate wound around the electrode, a container for housing the plurality of electrode bodies arranged so that the flat portions face each other, a plurality of first elastic portions individually disposed in the center of each of the plurality of electrode bodies, and a plurality of second elastic portions disposed at positions sandwiching the flat portions of the plurality of electrode bodies.

[0007] According to the present invention, it is possible to provide an energy storage element that can suppress excessive pressure on the flat portion 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 cross-sectional view showing a container, a pair of electrode bodies, and a pair of elastic sheets according to an embodiment. Figure 5 is a cross-sectional view showing a container, a pair of electrode bodies, a third elastic sheet, and a fourth elastic sheet according to Modification 1. Figure 6 is a cross-sectional view showing a container, a pair of electrode bodies, and a fourth elastic sheet according to Modification 2. Figure 7 is a cross-sectional view showing a container, a pair of electrode bodies, a fifth elastic sheet, and a pair of sixth elastic sheets according to Modification 3.

[0009] (1) An energy storage element according to one aspect of the present invention comprises a plurality of electrode bodies on which an electrode plate is wound and which have a flat portion and a pair of curved portions sandwiching the flat portion; a container for housing the plurality of electrode bodies arranged so that the flat portions face each other; a plurality of first elastic portions individually disposed in the center of each of the plurality of electrode bodies; and a plurality of second elastic portions disposed at positions sandwiching the flat portions of the plurality of electrode bodies.

[0010] According to one aspect of the present invention, a first elastic portion is arranged in the center of each electrode body, and a plurality of second elastic portions are arranged in positions that sandwich the flat portions of the plurality of electrode bodies. Therefore, even when the electrode bodies are compressed, the first and second elastic portions allow for a certain degree of expansion of the electrode bodies. This makes it possible to alleviate excessive pressure on the flat portions of the electrode bodies.

[0011] (2) The energy storage element described in (1) above may be provided with a third elastic portion disposed between the flat portions of the plurality of electrode bodies.

[0012] According to the energy storage element described in (2) above, a third elastic portion is positioned between the flat portions of multiple electrode bodies, which allows for greater tolerance of electrode expansion. This further reduces excessive pressure on the flat portions of the electrode bodies.

[0013] (3) In the energy storage element described in (2) above, the first elastic portion, the second elastic portion, and the third elastic portion may be formed from a foam.

[0014] According to the energy storage element described in (3) above, since the first elastic part, the second elastic part, and the third elastic part are made of foam, they can be impregnated with an electrolyte, and thus electrolyte depletion can be suppressed.

[0015] (4) In the energy storage element described in any one of (1) to (3) above, the plurality of second elastic parts may be an elastic sheet that is wrapped around the plurality of electrode bodies collectively.

[0016] According to the energy storage element described in (4) above, since multiple second elastic parts are formed by an elastic sheet that is wrapped around multiple electrode bodies at once, the unity of the multiple electrode bodies can be enhanced.

[0017] (5) In the energy storage element described in (2) or (3) above, an elastic sheet may be wrapped around each of the plurality of electrode bodies, and the elastic sheet may include the second elastic portion and the third elastic portion.

[0018] According to the energy storage element described in (5) above, the second and third elastic parts are formed by elastic sheets wrapped around each electrode body, so the second and third elastic parts can be easily constructed.

[0019] (6) In the energy storage element described in (2) or (3) above, each of the plurality of second elastic portions and the third elastic portion may be flat and have a convex portion that protrudes toward the flat portion.

[0020] According to the energy storage element described in (6) above, each of the multiple second elastic parts and third elastic parts is provided with a convex portion that protrudes toward the flat part, so that the expansion of the electrode body can be more tolerated by the convex portion. This makes it possible to alleviate excessive pressure on the flat part of the electrode body.

[0021] (7) In the energy storage element described in any one of (1) to (6) above, the thickness of the second elastic portion may be greater than the thickness of the first elastic portion.

[0022] According to the energy storage element described in (7) above, since the thickness of the second elastic portion is greater than the thickness of the first elastic portion, the expansion of the electrode body in the flat portion can be effectively suppressed by the second elastic portion.

[0023] (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.

[0024] 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.

[0025] 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.

[0026] [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.

[0027] 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 vehicles 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.

[0028] As shown in Figures 1 and 2, the energy storage device 1 includes an outer casing 2. Inside the outer casing 2 are multiple energy storage elements 10 and multiple 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 multiple energy storage elements 10, busbar holders for holding the busbars, spacers positioned between the multiple energy storage elements 10, a circuit board for monitoring or controlling the charging and discharging states of the energy storage elements 10, and electrical components such as relays, fuses, shunt resistors, and connectors.

[0029] The outer casing 2 is a rectangular parallelepiped (box-shaped) container (module case) that constitutes the outer casing (housing, outer 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, etc., and fixes the plurality of energy storage elements 10, 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 resin material. 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.

[0030] The exterior body 2 comprises an exterior body 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 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, etc.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] [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 when it is disassembled according to this embodiment. 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, a pair of electrode bodies 700, and a pair of elastic sheets 800. 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.

[0036] The container 100 is a container having an outer shape based on a rectangular parallelepiped. Specifically, the container 100 has a rectangular parallelepiped shape elongated in the X-axis direction as its outer shape. The container 100 includes a container body 110 and a lid 120, and forms a rectangular parallelepiped shape when the container body 110 and the lid 120 are assembled.

[0037] The container body 110 is a rectangular parallelepiped box body with the Z-axis positive direction open. The container body 110 includes a rectangular bottom plate elongated in the X-axis direction and a corner tube-shaped wall portion extending in the Z-axis positive direction from the outer peripheral edge of the bottom plate. The lid 120 is a rectangular sheet metal elongated in the X-axis direction and closes the opening of the container body 110. Through holes 121 through which each terminal 300 penetrates are formed at both ends of the lid 120 in the X-axis direction.

[0038] Although not shown here, a liquid injection part and a gas discharge valve are formed in the lid 120. The liquid injection part is a part for injecting electrolyte into the interior of the container 100 during the manufacture of the energy storage element 10. The gas discharge valve is a safety valve that releases the pressure when the pressure inside the container 100 rises excessively.

[0039] With such a configuration, after the electrode body 700 etc. are housed inside the container body 110, the container body 110 and the lid 120 are joined by welding etc., and the interior is sealed. The material of the container 100 (the container body 110 and the lid 120) is not particularly limited, but it is preferably a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or a plated steel sheet.

[0040] The terminal 300 is a terminal (positive electrode terminal 310 and 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, an aluminum alloy, copper, or a copper alloy. The terminal 300 is connected (joined) to the current collector 600 by caulking or welding, etc., and is attached to the lid body 120.

[0041] 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 in a state of 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 is thus connected (joined) to the current collector 600.

[0042] The current collector 600 is disposed one by one on both sides in the X-axis direction of the pair of electrode bodies 700, 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 negative X-axis direction is the positive electrode current collector 610, and the current collector 600 in the positive X-axis direction is the negative electrode current collector 620.

[0043] Specifically, the current collector 600 comprises a base portion 601 and a pair of legs 602, which are integrally formed from sheet metal. The base portion 601 is a flat plate portion parallel to the XY plane and has a through hole 603 through which the shaft portion 340 of the terminal 300 passes. The pair of legs 602 are positioned to sandwich the base portion 601 in the Y-axis direction and are flat plate-shaped portions extending from the base portion 601 in the Z-axis negative direction. Of the pair of legs 602, the leg portion 602 in the Y-axis positive direction is connected (joined) to the electrode body 700 in the Y-axis positive direction, and the leg portion 602 in the Y-axis negative direction is connected (joined) to the electrode body 700 in the Y-axis negative direction.

[0044] The external gasket 400 is a plate-shaped, rectangular insulating sealing member that is placed between the lid 120 of the container 100 and the terminal 300, and insulates and seals the space between the lid 120 and the terminal 300. The internal gasket 500 is a plate-shaped, rectangular insulating sealing member that is placed between the lid 120 and the current collector 600, and insulates and seals the space between the lid 120 and the current collector 600. The outer gasket 400 and the inner gasket 500 are formed from electrically insulating resins such as polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyetheretherketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), ABS resin, or composite materials to which fillers have been added.

[0045] A 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, etc. 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, etc. 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.

[0046] 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 Ni ０．５ O ４ and other spinel-type lithium manganese oxides, LiMO ２ having an α-NaFeO ２ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) and other lithium transition metal oxides can be used. Examples of the negative electrode active material include lithium metal, an alloy capable of occluding and releasing lithium, a carbon material (graphite, non-graphitizable carbon, graphitizable carbon, low-temperature fired carbon, amorphous carbon, etc.), and silicon oxide.

[0047] The separator is a microporous sheet made of resin. As the material of the separator, any known material can be appropriately used as long as it does not impair the performance of the power storage element. As the separator, a woven fabric insoluble in an organic solvent, a non-woven fabric, a synthetic resin microporous membrane made of a polyolefin resin such as polyethylene, etc. may be used.

[0048] 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. 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.

[0049] In this embodiment, a core 790 is positioned in the center of the electrode body 700 in the X-axis direction. The electrode body 700 is formed by winding a positive electrode plate, a negative electrode plate, and a separator around the core 790. The core 790 is a rectangular, flat, elastic member that is parallel to the XZ plane and elongated in the X-axis direction. Thus, the core 790 is an example of a first elastic part that is individually positioned in the center of each of the multiple electrode bodies 700.

[0050] The thickness of the core 790 (length in the Y-axis direction) is greater than the thickness of the separator or the insulating film enclosing the electrode body 700, etc. Specifically, the thickness of the core 790 is 0.5 mm or more. The core 790 is a porous elastic body formed from an insulating foam. Therefore, the electrolyte can be absorbed by the core 790.

[0051] One end of the winding core 790 in the positive X-axis direction faces one end of the main body portion 710 of the electrode body 700 in the positive X-axis direction, and one end of the winding core 790 in the negative X-axis direction faces one end of the main body portion 710 in the negative X-axis direction. As a result, even if the main body portion 710 expands, the winding core 790 contracts overall relative to the entire length of the main body portion 710 in the X-axis direction. Therefore, some degree of expansion of the main body portion 710 can be tolerated along its entire length in the X-axis direction.

[0052] Furthermore, it is even more preferable that one end of the winding core 790 in the positive X-axis direction faces one end of the electrode body 700 in the positive X-axis direction, and one end of the winding core 790 in the negative X-axis direction faces one end of the electrode body 700 in the negative X-axis direction. This allows the winding core 790 to be made as large as possible, and increases the amount of electrolyte absorbed by the winding core 790.

[0053] 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).

[0054] 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).

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The main body portion 710 includes a flat portion 711 and a pair of curved portions 712 that sandwich the flat portion 711 in the Z-axis direction (see FIG. 4). The flat portion 711 is a flat portion 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 laminated in the Y-axis direction. Since the flat portion 711 is the main part of the electrode body 700, the lamination direction (Y-axis direction) of each electrode plate in this flat portion 711 can be referred to as the lamination direction of the electrode plates in the electrode body 700.

[0059] Each curved portion 712 is a portion 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 a semicircular arc shape. Each curved portion 712 does not have to be a complete semicircular arc shape, and may be an arc shape in which the semicircle is somewhat crushed.

[0060] [Positional Relationship between Each Electrode Body and Each Elastic Sheet] FIG. 4 is a cross-sectional view showing the container 100, the pair of electrode bodies 700, and the pair of elastic sheets 800 according to the embodiment. In FIG. 4, the illustration of the terminal 300, the external gasket 400, the internal gasket 500, and the current collector 600 is omitted.

[0061] As shown in FIG. 4, each elastic sheet 800 is wound around each electrode body 700. Each elastic sheet 800 is wound along the circumferential direction with respect to the outer peripheral surface of each electrode body 700. At this time, each elastic sheet 800 is wound around the outer peripheral surface of each electrode body 700 so as to expose the curved portion 712 in the +Z-axis direction and cover other regions. Each elastic sheet 800 is a porous elastic body formed in a strip shape from an insulating foam. The thickness (wall thickness) of each elastic sheet 800 is larger than the thickness of the separator or the thickness of the insulating film that wraps the electrode body 700 or the like. Specifically, the thickness of each elastic sheet 800 is 0.5 mm or more. Further, it is preferable that the thickness of each elastic sheet 800 is larger than the thickness of the winding core 790.

[0062] One end of the elastic sheet 800 in the positive X-axis direction faces one end of the main body 710 of the electrode body 700 in the positive X-axis direction, and one end of the elastic sheet 800 in the negative X-axis direction faces one end of the main body 710 in the negative X-axis direction. Thus, even when the main body 710 expands, the elastic sheet 800 contracts as a whole with respect to the total length of the main body 710 in the X-axis direction. Therefore, the expansion of the main body 710 can be tolerated to some extent over the entire length in the X-axis direction.

[0063] Furthermore, it is more preferable that one end of the elastic sheet 800 in the positive X-axis direction faces one end of the electrode body 700 in the positive X-axis direction, and one end of the elastic sheet 800 in the negative X-axis direction faces one end of the electrode body 700 in the negative X-axis direction. Thereby, the elastic sheet 800 can be made as large as possible, and the amount of electrolyte absorbed by the elastic sheet 800 can be increased.

[0064] Of the pair of electrode bodies 700, the electrode body 700 in the negative Y-axis direction is referred to as the first electrode body 701, and the electrode body 700 in the positive Y-axis direction is referred to as the second electrode body 702. Similarly, of the pair of elastic sheets 800, the elastic sheet 800 wound around the first electrode body 701 is referred to as the first elastic sheet 810, and the elastic sheet 800 wound around the second electrode body 702 is referred to as the second elastic sheet 820.

[0065] In the first elastic sheet 810 and the second elastic sheet 820, the portions that overlap the flat portion 711 of each electrode body 700 from the negative Y-axis direction are first flat portions 811 and 821 that are planar along the flat portion 711. On the other hand, in the first elastic sheet 810 and the second elastic sheet 820, the portions that overlap the flat portion 711 of each electrode body 700 from the positive Y-axis direction are second flat portions 812 and 822 that are planar along the flat portion 711.

[0066] That is, the first flat portion 811 of the first elastic sheet 810 and the second flat portion 822 of the second elastic sheet 820 are an example of a plurality of second elastic portions arranged at positions sandwiching the flat portion 711 of each electrode body 700.

[0067] In contrast, the second flat portion 812 of the first elastic sheet 810 and the first flat portion 821 of the second elastic sheet 820 are examples of a third elastic portion positioned between the flat portions 711 of each electrode body 700.

[0068] When the first electrode body 701 and the second electrode body 702, which are constrained by the container 100, expand within the container 100, each flat portion 711 is particularly prone to expanding in the Y-axis direction. Each first elastic portion (winding core 790) is compressed, allowing each flat portion 711 to expand toward the center. The second elastic portion (first planar portion 811 and second planar portion 822) is compressed by the container 100 and each flat portion 711, allowing each flat portion 711 to expand toward the outside of the container 100. The third elastic portion (second planar portion 822 and first planar portion 821) is compressed by each flat portion 711, allowing each flat portion 711 to expand toward the inside of the container 100. This suppresses excessive compression in each flat portion 711.

[0069] The elastic sheet 800 is wrapped around the outer surface of the electrode body 700 so as to expose the curved portion 712 in the positive Z-axis direction and cover the other areas. In other words, since at least one of the pair of curved portions 712 is exposed from the elastic sheet 800, the load on the exposed curved portion 712 during expansion of the electrode body 700 is reduced, which is preferable.

[0070] [Effects, etc.] As described above, according to the embodiment, a winding core 790 (first elastic part) is arranged in the center of each electrode body 700, and a plurality of second elastic parts (first planar part 811 and second planar part 822) are arranged in positions that sandwich the flat parts 711 of the plurality of electrode bodies 700. Therefore, even when the electrode body 700 is compressed, the first elastic part and the second elastic part allow the electrode body 700 to expand to a certain extent. This makes it possible to alleviate excessive pressure on the flat parts 711 of the electrode body 700.

[0071] Since a third elastic portion (second planar portion 822 and first planar portion 821) is positioned between the flat portions 711 of the multiple electrode bodies 700, the expansion of the electrode bodies 700 can be more tolerated. This further reduces excessive pressure on the flat portions 711 of the electrode bodies 700.

[0072] Since the first, second, and third elastic parts are made of foam, they can be impregnated with electrolyte, thus preventing electrolyte depletion.

[0073] Since the second and third elastic parts are formed by elastic sheets 800 individually wrapped around each electrode body 700, the second and third elastic parts can be easily constructed.

[0074] The thickness of the elastic sheet 800 is greater than the thickness of the core 790. In other words, since the thickness of the second elastic section is greater than the thickness of the first elastic section, the expansion of the flat section 711 of the electrode body 700 can be effectively suppressed by the second elastic section. The same applies to the third elastic section.

[0075] (Modifications) Modifications of the above embodiments will be described below. In the following description, parts that are the same as those in the above embodiments or other modifications may be denoted by the same reference numerals and their descriptions may be omitted.

[0076] [Modification 1] Figure 5 is a cross-sectional view showing the container 100, a pair of electrode bodies 700, a third elastic sheet 830, and a fourth elastic sheet 840 according to Modification 1. Figure 5 corresponds to Figure 4.

[0077] As shown in Figure 5, the third elastic sheet 830 is an example of a third elastic portion positioned between the flat portions 711 of a pair of electrode bodies 700. The third elastic sheet 830 is a rectangular, flat elastic member that is parallel to the XZ plane and elongated in the X-axis direction. The third elastic sheet 830 is a porous elastic body formed from an insulating foam. The thickness (length in the Y-axis direction) of the third elastic sheet 830 is greater than the thickness of the separator or the insulating film that encloses the electrode bodies 700, etc. Furthermore, it is preferable that the thickness of the third elastic sheet 830 is greater than the thickness of the core 790.

[0078] The fourth elastic sheet 840 is wrapped around multiple electrode bodies 700 collectively. At this time, the fourth elastic sheet 840 is wrapped around the outer surface of each electrode body 700 along the circumferential direction so as to expose the curved portion 712 in the positive Z-axis direction. One end 841 of the fourth elastic sheet 840 overlaps the flat portion 711 of the first electrode body 701 from the negative Y-axis direction. The other end 842 of the fourth elastic sheet 840 overlaps the flat portion 711 of the second electrode body 702 from the positive Y-axis direction. In other words, one end 841 and the other end 842 of the fourth elastic sheet 840 are an example of multiple second elastic portions positioned to sandwich the flat portion 711 of each electrode body 700. The middle portion 843 of the fourth elastic sheet 840 is positioned opposite the curved portion 712 in the negative Z-axis direction of the first electrode body 701 and the second electrode body 702 and the third elastic sheet 830.

[0079] The fourth elastic sheet 840 is a porous elastic body formed in a strip shape from an insulating foam. The thickness (wall thickness) of the fourth elastic sheet 840 is greater than the thickness of the separator or the thickness of the insulating film that encloses the electrode body 700, etc. Specifically, the thickness of the fourth elastic sheet 840 is 0.5 mm or more. Furthermore, it is preferable that the thickness of the fourth elastic sheet 840 is greater than the thickness of the winding core 790.

[0080] As described above, since multiple second elastic sections are formed by the fourth elastic sheet 840 which is wrapped around multiple electrode bodies 700 at once, the unity of the multiple electrode bodies 700 can be enhanced.

[0081] [Modified Example 2] Figure 6 is a cross-sectional view showing the container 100, a pair of electrode bodies 700, and a fourth elastic sheet 840 according to Modified Example 2. Figure 6 corresponds to Figure 5. Modified Example 2 shows a form in which the third elastic sheet 830 is removed from the form of Modified Example 1. Therefore, the flat portions 711 of the pair of electrode bodies 700 are overlapped. Even without the third elastic sheet 830 (third elastic portion), the winding core 790 (first elastic portion) and one end 841 and the other end 842 (second elastic portion) of the fourth elastic sheet 840 allow for expansion of the flat portions 711 of each electrode body 700, and excessive pressure on the flat portions 711 can be alleviated.

[0082] [Modification 3] Figure 7 is a cross-sectional view showing the container 100, a pair of electrode bodies 700, a fifth elastic sheet 850, and a pair of sixth elastic sheets 860 according to Modification 3. Figure 7 corresponds to Figure 4.

[0083] As shown in Figure 7, the fifth elastic sheet 850 is an example of a third elastic portion positioned between the flat portions 711 of a pair of electrode bodies 700. The fifth elastic sheet 850 is a rectangular, flat elastic member that is parallel to the XZ plane and elongated in the X-axis direction. The fifth elastic sheet 850 is provided continuously from the upper end to the lower end inside the container 100. In the fifth elastic sheet 850, the portion facing the flat portion 711 of each electrode body 700 is a convex portion 851 that protrudes toward the flat portion. The convex portions 851 are provided on both the front and back surfaces of the fifth elastic sheet 850. The fifth elastic sheet 850 is a porous elastic body formed from an insulating foam. The thickness (length in the Y-axis direction) of the fifth elastic sheet 850 is greater than the thickness of the separator or the thickness of the insulating film that encloses the electrode bodies 700, etc. Furthermore, it is preferable that the thickness of the fifth elastic sheet 850 is greater than the thickness of the core 790.

[0084] The pair of sixth elastic sheets 860 are arranged to sandwich the pair of electrode bodies 700 in the Y-axis direction. In other words, the pair of sixth elastic sheets 860 are an example of a plurality of second elastic parts positioned to sandwich the flat portion 711 of each electrode body 700.

[0085] Specifically, of the pair of sixth elastic sheets 860, the sixth elastic sheet 860 in the negative Y-axis direction is positioned in the negative Y-axis direction of the first electrode body 701. On the other hand, the sixth elastic sheet 860 in the positive Y-axis direction is positioned in the positive Y-axis direction of the second electrode body 702. In each sixth elastic sheet 860, the portion facing the flat portion 711 of each electrode body 700 is a convex portion 861 that protrudes toward the flat portion. The sixth elastic sheet 860 is a porous elastic body formed from an insulating foam. The thickness (length in the Y-axis direction) of the sixth elastic sheet 860 is greater than the thickness of the separator or the thickness of the insulating film that encloses the electrode body 700, etc. Furthermore, it is preferable that the thickness of the sixth elastic sheet 860 is greater than the thickness of the core 790.

[0086] As described above, since each of the fifth elastic sheet 850 and the multiple sixth elastic sheets 860 is provided with protrusions 851 and 861 that project toward the flat portion 711, even if the flat portion 711 of the electrode body 700 expands, the protrusions 851 and 861 are compressed. In other words, the protrusions 851 and 861 allow for greater expansion of the electrode body 700. This reduces excessive pressure on the flat portion 711 of the electrode body 700.

[0087] (Other) Although embodiments of the present invention (including modifications thereof; the same applies hereinafter) of energy storage elements have 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.

[0088] In the above embodiment, the example was given in which the curved portion 712 in the Z-axis positive direction of each electrode body 700 is exposed from the elastic sheet 800, but the curved portion 712 may be covered by the elastic sheet 800.

[0089] In the above embodiment, the case in which the core 790 and the elastic sheet 800 are formed from a foam is illustrated, but the core 790 and the elastic sheet 800 may be formed from any material as long as they have elasticity.

[0090] In the above embodiment, the case in which the thickness of the elastic sheet 800 is greater than the thickness of the core 790 was illustrated, but the thickness of the core 790 may be greater than the thickness of the elastic sheet 800, or the thickness of the core 790 and the thickness of the elastic sheet 800 may be equal.

[0091] The present invention also includes forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples.

[0092] This invention can be applied to energy storage elements such as lithium-ion secondary batteries.

[0093] 1. Energy storage device 2. Outer casing 10. Energy storage element 11. External terminal 30. Outer casing body 40. Outer casing lid 100. Container 300. Terminal 600. Current collector 700. Electrode body 701. First electrode body 702. Second electrode body 710. Main body 711. Flat part 712. Curved part 790. Core (first insulating part) 800. Elastic sheet 810. First elastic sheet 811. First flat part (second insulating part) 812. Second flat part (third insulating part) 820. Second elastic sheet 821. First flat part (third insulating part) 822. Second flat part (second insulating part) 830. Third elastic sheet (third insulating part) 840. Fourth elastic sheet 841. One end (second insulating part) 842. Other end (second insulating part) 843. Intermediate part 850. Fifth elastic sheet (third insulating part) 851, 861 Protrusion 860 Sixth elastic sheet (second insulating part)

Claims

1. An energy storage element comprising: a plurality of electrode bodies, each having a flat portion and a pair of curved portions sandwiching the flat portion, with an electrode plate wound around it; a container for housing the plurality of electrode bodies arranged so that the flat portions face each other; a plurality of first elastic portions individually disposed in the center of each of the plurality of electrode bodies; and a plurality of second elastic portions positioned to sandwich the flat portions of the plurality of electrode bodies.

2. The energy storage element according to claim 1, further comprising a third elastic portion disposed between the flat portions of the plurality of electrode bodies.

3. The energy storage element according to claim 2, wherein the first elastic portion, the second elastic portion, and the third elastic portion are formed from a foam.

4. The energy storage element according to claim 1 or 2, wherein the plurality of second elastic portions are elastic sheets wound collectively around the plurality of electrode bodies.

5. The energy storage element according to claim 2 or 3, wherein an elastic sheet is wrapped around each of the plurality of electrode bodies, and the elastic sheet comprises the second elastic portion and the third elastic portion.

6. The energy storage element according to claim 2 or 3, wherein each of the plurality of second elastic portions and the third elastic portion is flat and has a convex portion that protrudes toward the flat portion.

7. The energy storage element according to claim 1 or 2, wherein the thickness of the second elastic portion is greater than the thickness of the first elastic portion.

Images