Energy storage device

Abstract

This energy storage device comprises a plurality of energy storage elements and an exterior body accommodating the plurality of energy storage elements. Each of the energy storage elements comprises: a wound electrode body comprising a pair of curved parts and a flat part interposed between the pair of curved parts; a container accommodating the electrode body; and a pair of terminals which are partially disposed outside the container and which are electrically connected to the electrode body. The container comprises: a pair of first flat wall parts facing both end parts of the electrode body in a winding axis direction; a pair of curved wall parts facing the pair of curved parts; and a pair of second flat wall parts facing each other with the flat part interposed therebetween. The plurality of energy storage elements are oriented such that the pair of curved wall parts are arranged in the vertical direction and the second flat wall parts of a pair of adjacent energy storage elements face each other. The terminal is installed in an upper end part of each of the pair of first flat wall parts. In at least one of the pair of first flat wall parts, a gas discharge valve is disposed below the terminal.

Description

Energy storage device

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

[0002] Conventionally, a sealed battery is known in which a flattened, rolled electrode body is housed within a long, cylindrical outer casing (see Patent Document 1).

[0003] Japanese Patent Publication No. 2011-187325

[0004] In energy storage devices comprising multiple sealed batteries and an outer casing to house them, there is a need to improve manufacturability.

[0005] Therefore, the object of the present invention is to provide an energy storage device that can improve manufacturability.

[0006] An energy storage device according to one aspect of the present invention is an energy storage device comprising a plurality of energy storage elements and an outer casing for housing the plurality of energy storage elements, wherein the energy storage element comprises a wound electrode body having a pair of curved portions and a flat portion sandwiched between the pair of curved portions, a container for housing the electrode body, and a pair of terminals, part of which are located outside the container and electrically connected to the electrode body, wherein the container comprises a pair of first flat wall portions facing both ends of the electrode body in the winding axis direction, a pair of curved wall portions facing the pair of curved portions, and a pair of second flat wall portions facing each other across the flat portion, wherein the plurality of energy storage elements are arranged such that the pair of curved wall portions are arranged in the vertical direction and the second flat wall portions of adjacent pairs of energy storage elements face each other, the terminals are installed at the upper ends of each of the pair of first flat wall portions, and a gas discharge valve is located below the terminal on at least one of the pair of first flat wall portions.

[0007] According to the present invention, it is possible to provide an energy storage device that can improve manufacturability.

[0008] Figure 1 is a perspective view showing the external appearance of the energy storage device according to the embodiment. Figure 2 is an exploded perspective view showing the individual components when the energy storage device according to the embodiment is disassembled. Figure 3 is a perspective view showing the external appearance of the energy storage element according to the embodiment. Figure 4 is an exploded perspective view showing the individual components when the energy storage element according to the embodiment is disassembled. Figure 5 is a perspective view showing the configuration of the electrode body according to the embodiment. Figure 6 is a cross-sectional view showing the positional relationship between the container and electrode body and the spacer of the energy storage element according to the embodiment.

[0009] (1) An energy storage device according to one aspect of the present invention is an energy storage device comprising a plurality of energy storage elements and an outer casing for housing the plurality of energy storage elements, wherein the energy storage element comprises a wound electrode body having a pair of curved portions and a flat portion sandwiched between the pair of curved portions, a container for housing the electrode body, and a pair of terminals, part of which are located outside the container and electrically connected to the electrode body, wherein the container comprises a pair of first flat wall portions facing both ends of the electrode body in the winding axis direction, a pair of curved wall portions facing the pair of curved portions, and a pair of second flat wall portions facing each other across the flat portion, wherein the plurality of energy storage elements are arranged such that the pair of curved wall portions are arranged in the vertical direction and the second flat wall portions of adjacent pairs of energy storage elements face each other, the terminals are installed at the upper ends of each of the pair of first flat wall portions, and a gas discharge valve is located below the terminals on at least one of the pair of first flat wall portions.

[0010] According to the energy storage device described in (1) above, terminals are located at the upper ends of each of the pair of first flat wall portions provided on each energy storage element, so that the terminals of each energy storage element can be connected with busbars before each energy storage element is fully inserted into the outer casing. On the other hand, since a gas discharge valve is located below the terminals on at least one of the first flat wall portions of each energy storage element, the gas discharge valves can be arranged in a straight line. This simplifies the gas flow path inside the outer casing. As a result, the manufacturability of the energy storage device can be improved.

[0011] (2) In the energy storage device described in (1) above, the gas discharge valve may be housed in the lower half of the first flat wall portion.

[0012] According to the energy storage device described in (2) above, since the gas discharge valve is housed in the lower half of the first flat wall section, the gas flow path inside the outer casing can be formed compactly.

[0013] (3) In the energy storage device described in (1) or (2) above, one of the pair of first flat wall portions may be provided with an injection portion for injecting electrolyte into the container between the terminal and the gas discharge valve.

[0014] According to the energy storage device described in (3) above, since the liquid injection section is provided between the terminal and the gas discharge valve, the liquid injection section can be positioned opposite the winding core of the electrode body. Therefore, the electrolyte can be injected from the liquid injection section toward the winding core of the electrode body, and the electrolyte can be injected into the electrode body in a balanced manner.

[0015] (4) In the energy storage device described in any one of (1) to (3) above, the pair of curved portions may be in close contact with the pair of curved wall portions, and the flat portion may be in close contact with the pair of second flat wall portions.

[0016] In the energy storage device described in (4) above, a pair of curved sections are in close contact with a pair of curved wall sections, and a flat section is in close contact with a pair of second flat wall sections, so that the outer surface of the electrode body is restrained by each curved wall section and each second flat wall section. This restraint suppresses the expansion of the electrode body, and thus also suppresses the expansion and contraction that occur during charging and discharging of the energy storage element. In other words, damage to the electrode body caused by expansion and contraction can be suppressed, and the lifespan of the energy storage element can be extended.

[0017] (5) In the energy storage device described in (4) above, the electrode body may comprise at least one of a positive electrode plate comprising a positive electrode active material containing Ni in a molar ratio of 50% or more of the transition metals contained in the active material, and a negative electrode plate comprising a negative electrode active material layer containing Si in a molar ratio of 5% or more.

[0018] According to the energy storage device described in (5) above, the positive electrode plate, which has a positive electrode active material containing Ni at a molar ratio of 50% or more of the transition metals contained in the active material, and the negative electrode plate, which has a negative electrode active material layer containing Si at a molar ratio of 5% or more, have a tendency to expand. Even in an electrode body comprising at least one of the positive electrode plate and the negative electrode plate, the outer surface thereof is constrained by each curved wall portion and each second flat wall portion, so expansion can be suppressed and it is preferable.

[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 positions 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 X-axis direction is defined as at least one of the longitudinal direction of the energy storage element and the winding axis direction of the electrode body provided on the energy storage element. The Y-axis direction is defined as at least one of the direction in which the multiple energy storage elements are arranged, the thickness direction of the container of the energy storage element, and the opposing direction of the pair of flat wall portions of the container. The Z-axis direction is defined as at least one of the opposing direction of the pair of curved portions of the electrode body, the opposing direction of the pair of curved wall portions of the container, and the vertical 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.

[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] In the following explanation, "insulation" refers to "electrical insulation." The volume resistivity of an insulating material is 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.

[0023] In the following description, the term "tight contact" refers to "effective contact" to ensure the effects of this disclosure, and does not mean that there are no voids or gaps at the contact interface when viewed microscopically. The purpose of tightly contacting each component in this disclosure is to ensure that the container, or the spacer (described later) via the container, is substantially uniformly constrained to the electrode body, and the presence of microscopic gaps or voids does not hinder this purpose.

[0024] [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.

[0025] 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. Here, a rectangular parallelepiped refers to a hexahedron in which all faces are rectangles or squares. The energy storage device 1 is a battery module (battery pack) used for power storage or power supply purposes. Specifically, 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), aircraft, 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. Furthermore, the energy storage device 1 can also be used as a stationary battery for household or commercial use.

[0026] As shown in Figure 1, the energy storage device 1 includes a case 2. As shown in Figure 2, the case 2 houses a plurality of energy storage elements 10, a plurality of spacers 20, a pair of exhaust members 50, and a plurality of busbars 800, etc. The energy storage device 1 also includes external terminals (positive external terminal and negative external terminal) for electrically connecting to an external device in the case 2, but their illustration and description are omitted. 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 800, 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. Furthermore, a mechanism for cooling or heating the energy storage elements 10 can be provided at the bottom or outer circumference of the energy storage elements 10.

[0027] Case 2 is a roughly rectangular parallelepiped (box-shaped) container (module case) that constitutes the outer casing (enclosure, shell) of the energy storage device 1. Case 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. Case 2 is a metal case formed from a metal component such as aluminum, aluminum alloy, stainless steel, iron, plated steel sheet, etc. In addition, some or all of the components of Case 2 may be formed from an insulating component such as a resin material. If Case 2 is made of a conductive material, the inner surface of Case 2 may be covered with an insulating material to ensure insulation from the energy storage elements. It is preferable that Case 2 has higher rigidity than the spacers 20, which will be described later.

[0028] As shown in Figure 2, Case 2 comprises a case body 30 that constitutes the main body of Case 2 and a case cover 40 that constitutes the cover of Case 2. The case 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.

[0029] Specifically, the case body 30 has a bottom wall 32 and side walls 33. The bottom wall 32 is a flat, rectangular portion located at the end of the case body 30 in the negative Z-axis direction. The side wall 33 is a rectangular annular wall extending from the outer edge in the positive Z-axis direction and is continuously provided around the entire circumference of the bottom wall 32. The inside of the side wall 33 is an opening 31. A pair of exhaust ports 37 are provided in the portion of the side wall 33 in the negative Z-axis direction. Of the pair of exhaust ports 37, one exhaust port 37 is located at the corners in the negative Z-axis direction and the negative X-axis direction, and the other exhaust port 37 is located at the corners in the negative Z-axis direction and the positive X-axis direction. Each exhaust port 37 is a portion that connects the inside and outside of the case 2 and exhausts the gas discharged from each energy storage element 10 to the outside of the case 2.

[0030] The case lid 40 is a flat, rectangular member that closes the rectangular opening 31 of the case body 30. The case body 30 and the case lid 40 are sealed by joining them together by welding, welding, screwing, etc. The case body 30 and the case lid 40 may be made of the same material or of different materials.

[0031] 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 has a shape in which the length in the X-axis direction is longer than the length in the Y-axis direction, specifically, a rectangular parallelepiped shape (square, prism) that is flattened in the Y-axis direction. In this embodiment, eight energy storage elements 10 are arranged in line in the Y-axis direction. The size of the energy storage elements 10 and the number of energy storage elements 10 arranged are not particularly limited, and only one energy storage element 10 may be arranged. Each energy storage element 10 may be covered with an insulating film. Details of the energy storage elements 10 will be described later.

[0032] The spacer 20 is a flattened member in the Y-axis direction that is positioned alongside the energy storage element 10 in the Y-axis direction to fix the energy storage element 10 to other members and to provide insulation and / or heat insulation. The spacer 20 is positioned adjacent to the energy storage element 10 in the positive or negative Y-axis direction of the energy storage element 10 and is a member that fixes the energy storage elements 10 to each other or to the energy storage elements 10 to the case 2 and provides insulation and / or heat insulation.

[0033] Of the spacers 20, the spacers 20 placed between adjacent energy storage elements 10 are intermediate spacers 21, and the two spacers 20 placed at the Y-axis ends of the multiple energy storage elements 10 are end spacers 22. All spacers 20 may be made of the same material, or any of the spacers 20 may be made of a different material. Details of the spacers 20 will be described later.

[0034] The exhaust member 50 is a component that constitutes a gas flow path S that carries gas discharged from at least one energy storage element 10 to the outside of the case 2. In this embodiment, the energy storage device 1 is equipped with a pair of exhaust members 50. Each exhaust member 50 is located at the end in the X-axis direction within the case body 30 and is a component that faces the gap between each energy storage element 10 and each spacer 20 on a surface and covers the gap. By providing these exhaust members 50, it is possible to prevent high-temperature gas and debris from being directly released toward adjacent energy storage elements 10 in the event of thermal runaway of an energy storage element 10, thereby reducing the thermal impact on adjacent energy storage elements 10.

[0035] Each exhaust member 50 is a member having a first plate portion 51 and a second plate portion 52 bent relative to the first plate portion 51. In each exhaust member 50, the first plate portion 51 is a rectangular plate-shaped portion that is parallel to the YZ plane and elongated in the Y-axis direction. In each exhaust member 50, the second plate portion 52 is a rectangular plate-shaped portion that is parallel to the XY plane and elongated in the Y-axis direction. The first plate portion 51 overlaps the end face in the positive X-axis direction and the end face in the negative X-axis direction of each energy storage element 10. In each exhaust member 50, the second plate portion 52 extends to a position that abuts the YZ plane on the inner surface of the case body 30. As a result, each exhaust member 50 forms a gas flow path S extending in the Y-axis direction on both sides of each energy storage element 10 in the X-axis direction. Each exhaust member 50 covers the gap between adjacent energy storage elements 10 and spacers 20.

[0036] In each of the first plate portions 51, a plurality of ventilation holes 53 are provided at positions corresponding to the gas discharge valves 173 of the respective power storage elements 10. When a predetermined power storage element 10 enters a thermal runaway state and the discharge valve 173 is opened by high-temperature gas or debris to discharge the gas, the gas enters the gas flow path S through the ventilation holes 53. An annular sealing material interposed between the first plate portion 51 and the power storage element 10 may be disposed around the ventilation holes 53. The sealing material is formed of rubber or porous resin. The sealing material suppresses leakage of gas outside the gas flow path S. The gas flows through the gas flow path S and is exhausted from the exhaust port 37. At this time, since the exhaust member 50 covers the gaps between adjacent power storage elements 10 and the spacers 20, it is possible to suppress gas from entering these gaps, and it is possible to suppress a temperature rise of the adjacent power storage elements 10. Here, an L-shaped exhaust member 50 is illustrated when viewed from the Y-axis direction, but it may be U-shaped or square tubular. In any shape, ventilation holes may be formed at locations corresponding to the gas discharge valves of the respective power storage elements.

[0037] The bus bar 800 is connected (joined) to terminals 300 provided in a plurality of power storage elements 10. Specifically, a plurality of bus bars 800 connect the terminals 300 of the plurality of power storage elements 10 to each other and electrically connect the terminal 300 of the power storage element 10 at the end and an external terminal. The connection form of the bus bar 800 is not particularly limited, and the plurality of power storage elements 10 may be connected in series in any combination, may be connected in parallel, or all the power storage elements 10 may be connected in series or in parallel. The bus bar 800 and the terminal 300 are connected (joined) by welding or the like, but the connection form is not particularly limited. The bus bar 800 is formed of a metal conductive member such as aluminum, an aluminum alloy, copper, a copper alloy, nickel, or a combination thereof, or a conductive member other than metal.

[0038] [Power Storage Element] A general description of the power storage element 10 in the embodiment will be given with reference to FIGS. 3 and 4. FIG. 3 is a perspective view showing the appearance of the power storage element 10 according to the embodiment. FIG. 4 is an exploded perspective view showing the power storage element 10 according to the embodiment disassembled to show each component.

[0039] The energy storage element 10 is a secondary battery (single cell) that can charge and discharge electricity. More specifically, it is a non-aqueous electrolyte secondary battery such as a lithium-ion secondary 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 may be 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 a battery using a solid electrolyte.

[0040] As shown in FIGS. 3 and 4, the energy storage element 10 includes a container 100, a pair of terminals 300, and a pair of external gaskets 400. Further, the energy storage element 10 includes a pair of internal gaskets 500, a pair of current collectors 600, and an electrode body 700 inside the container 100.

[0041] An electrolytic solution (non-aqueous electrolyte) is enclosed inside the container 100, but its illustration is omitted. The type of the electrolytic solution is not particularly limited as long as it does not impair the performance of the energy storage element 10. In addition to the above components, a spacer may be arranged on the side, above, or below the electrode body 700, or an insulating film or the like that wraps the electrode body 700 or the like may be arranged.

[0042] The container 100 is a case having an elliptical columnar or oblong columnar outer shape that is long in the X-axis direction and flat in the Y-axis direction. In the present embodiment, although not particularly limited, from the viewpoint of improving the energy density of the energy storage element 10, the length of the container 100 in the X-axis direction is preferably 3 times or more the length of the container 100 in the Z-axis direction. More preferably, the length of the container 100 in the X-axis direction is 5 times or more the length of the container 100 in the Y-axis direction.

[0043] The container 100 comprises a container body 160 and a pair of first flat wall portions 170. The container body 160 and each of the first flat wall portions 170 are assembled to form an elliptical or oblong cylindrical container 100 that extends in the X-axis direction. The container body 160 comprises a pair of second flat wall portions 131 and a pair of curved wall portions 141. The pair of second flat wall portions 131 and the pair of curved wall portions 141 form an oblong cylindrical shape that extends in the X-axis direction and penetrates through in the X-axis direction. Each of the first flat wall portions 170 is a plate-like member that closes each end of the container body 160 in the X-axis direction and is included in the wall portion of the container 100. The first flat wall portion 170 located in the negative X-axis direction closes the end of the container body 160 in the negative X-axis direction, and the first flat wall portion 170 located in the positive X-axis direction closes the end of the container body 160 in the positive X-axis direction.

[0044] A gas discharge valve 173 is located in at least one of the pair of first flat wall sections 170. Figure 4 illustrates the case where the gas discharge valve 173 is located at the end of each first flat wall section 170 in the negative Z-axis direction. The gas discharge valve 173 is housed in the lower half of the first flat wall section 170. The gas discharge valve 173 is a safety valve that releases pressure when the pressure inside the container 100 rises excessively.

[0045] In Figure 4, of the pair of first flat wall sections 170, the first flat wall section 170 in the positive X-axis direction is provided with a liquid injection section 171 in the center in the Z-axis direction. As a result, the liquid injection section 171 is located between the terminal 300 and the gas discharge valve 173 in the first flat wall section 170. The liquid injection section 171 is the part used to inject the electrolyte into the container 100 during manufacturing, and is closed after injection.

[0046] With this configuration, the container 100 is sealed inside by welding or other means to the container body 160 and the first flat wall portion 170 after the electrode body 700 and the first flat wall portion 170 have been placed inside the container body 160. The material of the container 100 (container body 160 and first flat wall portion 170) is not particularly limited, but weldable metals such as stainless steel, aluminum, aluminum alloy, iron, and plated steel sheet are preferred.

[0047] Each of the pair of curved wall portions 141 is elongated in the X-axis direction and faces the curved portion 711 of the electrode body 700. In other words, each of the pair of curved wall portions 141 faces the pair of curved portions 711. The inner surface of each curved wall portion 141 is curved to conform to the curved portion 711 of the electrode body 700. Specifically, the inner surface of the curved wall portion 141 located in the Z-axis positive direction is curved so as to be concave in the Z-axis positive direction when viewed in the X-axis direction, and the inner surface of the curved wall portion 141 located in the Z-axis negative direction is curved so as to be concave in the Z-axis negative direction when viewed in the X-axis direction. In this embodiment, the outer surface of each curved wall portion 141 is also curved. Specifically, the curved wall portion 141 located in the Z-axis positive direction is formed in a curved plate shape that protrudes in the Z-axis positive direction when viewed in the X-axis direction. On the other hand, the curved wall portion 141 in the Z-axis negative direction is formed in a curved plate shape that protrudes in the Z-axis negative direction when viewed in the X-axis direction.

[0048] Each of the pair of second flat wall portions 131 is elongated in the X-axis direction and is a wall portion that faces the flat portion 712 of the electrode body 700 in the Y-axis direction. In other words, it can be said that each of the second flat wall portions 131 faces both sides of the flat portion 712. Each second flat wall portion 131 is formed in a flat plate shape parallel to the XZ plane, and the inner surface of the second flat wall portion 131 is flat so as to conform to the flat portion 712 of the electrode body 700.

[0049] The terminals 300 are terminals (positive and negative terminals) that are electrically connected to the electrode body 700 via the current collector 600. In other words, the terminals 300 are metal members that lead the electricity stored in the electrode body 700 to the external space of the energy storage element 10, or introduce electricity into the internal space of the energy storage element 10 in order to store electricity in the electrode body 700. The material of the terminals 300 is not particularly limited, but the terminals 300 are made of a conductive material such as aluminum, aluminum alloy, copper, or copper alloy. The terminals 300 are connected (joined) to the current collector 600 by crimping, welding, or the like, and are attached to the first flat wall portion 170.

[0050] Each terminal 300 is attached to each first flat wall portion 170 with a portion of it positioned outside the container 100. Specifically, each terminal 300 comprises a terminal body portion 330 and a shaft portion 340 protruding from the terminal body portion 330. The terminal body portion 330 is the portion that protrudes outward from the first flat wall portion 170. A through hole 172 is formed in each first flat wall portion 170 through which the shaft portion 340 passes. The terminal 300 and the current collector 600 are connected (joined) by crimping the shaft portion 340 so that it passes through the first flat wall portion 170, the outer gasket 400, the inner gasket 500, and the current collector 600.

[0051] The current collectors 600 are positioned one at each end of the electrode body 700 in the X-axis direction. The current collectors 600 are conductive members (positive electrode current collector and negative electrode current collector) that are connected (joined) to the electrode body 700 and the terminal 300, thereby electrically connecting the electrode body 700 and the terminal 300. The current collector 600 integrally includes a first joint portion 630 and a second joint portion 640. Specifically, the first joint portion 630 of the current collector 600 and the tab portion 720 of the electrode body 700 (described later) are connected (joined) by welding or crimping, and the second joint portion 640 of the current collector 600 and the terminal 300 are connected (joined) by crimping or welding. The first joint portion 630 and the second joint portion 640 are each flat plate-shaped parts, formed by bending a single sheet of metal. The material of the current collector 600 is not particularly limited, but in this embodiment, the positive electrode current collector is made of a conductive material such as aluminum or an aluminum alloy, and the negative electrode current collector is made of a conductive material such as copper or a copper alloy.

[0052] The external gasket 400 is a member that is disposed between the first flat wall portion 170 and the terminal 300, insulates between the first flat wall portion 170 and the terminal 300, and seals the interior of the container 100. The internal gasket 500 is a member that is disposed between the first flat wall portion 170 and the current collector 600, insulates between the first flat wall portion 170 and the current collector 600, and seals the interior of the container 100. In the present embodiment, both the external gasket 400 and the internal gasket 500 are plate-shaped and rectangular insulating members. The materials of the external gasket 400 and the internal gasket 500 may be resins having electrical insulation properties such as polypropylene (PP), polyethylene (PE), polystyrene (PS), ABS resin, or composite materials thereof.

[0053] [Electrode Body] FIG. 5 is a perspective view showing the configuration of the electrode body 700 according to the embodiment. Specifically, FIG. 5 shows a state in which the winding of the electrode plate in the electrode body 700 is partially unfolded. As shown in FIG. 5, the electrode body 700 includes a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762.

[0054] The positive electrode plate 740 is an electrode plate (electrode sheet) in which positive electrode active material layers 742 are disposed on both surfaces of a positive electrode current collector foil 741 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 741. The negative electrode plate 750 is an electrode plate (electrode sheet) in which negative electrode active material layers 752 are disposed on both surfaces of a negative electrode current collector foil 751 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 751. As the positive electrode active material used in the positive electrode active material layer 742 and the negative electrode active material used in the negative electrode active material layer 752, any known material can be appropriately used as long as it is a material capable of occluding and releasing lithium ions.

[0055] 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 O４ 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. Here, if the positive electrode active material contains Ni, it is preferable that it contains 50% or more Ni in molar ratio to increase the energy density of the electrode body 700. The positive electrode active material layer may optionally contain other positive electrode active materials other than the lithium transition metal composite oxide, conductive agents, binders, thickeners, fillers, and other optional components.

[0056] Examples of negative electrode active materials include lithium metal, alloys capable of intercalating and deintercalating lithium, carbon materials (graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature calcined carbon, amorphous carbon, etc.), and silicon oxides. In particular, it is preferable that the negative electrode active material contains 5% or more Si by molar ratio. One form of Si in which Si is included is by adding at least one of Si metal, SiO active material, and SiC (Si supported on carbon) to the negative electrode active material. All three of these may also be added to the negative electrode active material.

[0057] The separators 761 and 762 are microporous sheets made of resin. Any known material can be used for the separators 761 and 762, as long as it does not impair the performance of the energy storage element 10. As separators 761 and 762, woven fabrics, nonwoven fabrics, synthetic resin microporous membranes made of polyolefin resins such as polyethylene, which are insoluble in organic solvents, may also be used.

[0058] The electrode body 700 is formed by winding together a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762. Specifically, the electrode body 700 is formed by stacking and winding together the negative electrode plate 750, separator 761, positive electrode plate 740, and separator 762 in this order. In this embodiment, the positive electrode plate 740, the negative electrode plate 750, and separators 761 and 762 are wound around a winding axis L extending in the X-axis direction to form a wound electrode body 700. The winding axis L is a virtual axis that serves as the central axis when winding the positive electrode plate 740, the negative electrode plate 750, and separators 761 and 762. In this embodiment, the winding axis is a straight line parallel to the X-axis direction that passes through the center of the electrode body 700.

[0059] When the electrode body 700 is placed in the container 100, its winding core and the liquid injection section 171 are positioned opposite each other. As a result, the electrolyte poured from the liquid injection section 171 is poured toward the winding core of the electrode body 700 and injected into the electrode body 700 in a balanced manner.

[0060] Multiple positive electrode tabs 743 are spaced apart on the edge of the positive electrode plate 740 in the positive X-axis direction, protruding outward. Similarly, multiple negative electrode tabs 753 are spaced apart on the edge of the negative electrode plate 750 in the negative X-axis direction. Each of the multiple positive electrode tabs 743 is a portion where the positive electrode active material layer is not present and the positive electrode current collector foil 741 is exposed (a portion where the positive electrode active material layer is not formed). On the positive electrode plate 740, portions where the positive electrode current collector foil 741 is exposed (a portion where the positive electrode active material layer is not formed) are continuously formed on both edges in the X-axis direction. Each of the multiple negative electrode tabs 753 is a portion where the negative electrode active material layer is not present and the negative electrode current collector foil 751 is exposed (a portion where the negative electrode active material layer is not formed). In Figure 5, the portions where the active material layer is not formed (a portion where the positive electrode active material layer is not formed, a portion where the negative electrode active material layer is not formed) are shown with hatched lines.

[0061] When the positive electrode plate 740 and the negative electrode plate 750 are wound with the separators 761 and 762, the multiple positive electrode tabs 743 of the positive electrode plate 740 almost overlap at the end face (one end face) in the positive X-axis direction of the main body portion 710, and the multiple negative electrode tabs 753 of the negative electrode plate 750 almost overlap at the end face (the other end face) in the negative X-axis direction. The portion of the positive electrode plate 740 where the multiple positive electrode tabs 743 overlap is the positive electrode tab portion 721. In other words, the positive electrode tab portion 721 is the part where the multiple tabs (positive electrode tabs 743) of the electrode plate (positive electrode plate 740) of the same polarity are stacked. Hereafter, the expressions "overlapping" and "overlapping" are not limited to a strictly integral stacking. "Overlapping" and "overlapping" include situations where they overlap with variation (shift) in a direction intersecting the direction of overlap.

[0062] Similarly, the portion of the negative electrode plate 750 where multiple negative electrode tabs 753 overlap is the negative electrode tab portion 722. In other words, the negative electrode tab portion 722 is the part of the plate (positive electrode plate 740 and negative electrode plate 750) where multiple tabs (negative electrode tabs 753) of the same polarity plate (negative electrode plate 750) are stacked.

[0063] Thus, the electrode body 700 comprises a main body portion 710 that constitutes the body of the electrode body 700, and tab portions 720 (positive electrode tab portion 721 and negative electrode tab portion 722) that protrude from each end face of the main body portion 710 in the X-axis direction. In other words, the electrode body 700 comprises a pair of tab portions consisting of a positive electrode tab portion 721 and a negative electrode tab portion 722.

[0064] The main body portion 710 is an elliptical or oblong cylindrical portion formed by winding together the portion of the positive electrode plate 740 on which the positive electrode active material layer 742 is arranged (formed, coated) and a portion of which is uncoated, the portion of the negative electrode plate 750 on which the negative electrode active material layer 752 is arranged (formed, coated), and separators 761 and 762. Within the main body portion 710, the region where at least one of the positive electrode active material layer 742 and the negative electrode active material layer 752 is laminated is called the active material layer forming portion. The main body portion 710 has curved portions 711 at both ends in the Z-axis direction and a flat portion 712 between them. The flat portion 712 is located between the pair of curved portions 711 in the Z-axis direction and is flat overall.

[0065] The curved portion 711 extends in the X-axis direction and protrudes in a curved manner in the positive and negative Z-axis directions. When viewed from the X-axis direction, the outer surface of the curved portion 711 is curved in a semicircular arc shape. The curved portion 711 located in the positive Z-axis direction and the curved wall portion 141 of the container body 160 face each other in the Z-axis direction, and the curved portion 711 located in the negative Z-axis direction and the curved wall portion 141 of the container body 160 face each other in the Z-axis direction. In other words, the curved portion 711 and the curved wall portion 141 face each other in the Z-axis direction.

[0066] The flat portion 712 extends in the X-axis direction and is a flat (plate-shaped) portion parallel to the XZ plane that connects the ends of the pair of curved portions 711. The flat portion 712 is positioned opposite each second flat wall portion 131 of the container body 160. In the flat portion 712, multiple wound electrode plates and separators (positive electrode plate 740, negative electrode plate 750, separators 761, 762) are stacked in the Y-axis direction. Here, the stacking direction of the multiple electrode plates in the flat portion 712 is defined as the Y-axis direction.

[0067] The curved shape of the outer surface of the curved portion 711, as viewed from the X-axis direction, is not limited to a semicircular arc shape, but may also be a shape like part of an ellipse, or a polygonal shape, etc. The flat portion 712 is not limited to the outer surface of the electrode body 700 perpendicular to the Y-axis direction being perfectly flat, but the outer surface may be slightly concave or slightly convex.

[0068] [Spacer] As shown in Figure 2, the spacer 20 is formed in a rectangular shape when viewed in the Y-axis direction, and its length in the X-axis direction corresponds to the length of the energy storage element 10 in the X-axis direction. An upper flange portion 201 extending in the X-axis direction is provided at the upper end of the spacer 20, and a lower flange portion 202 extending in the X-axis direction is provided at the lower end of the spacer 20. Specifically, the upper end of the intermediate spacer 21 is provided with upper flange portions 201 at both ends in the Y-axis direction, and the lower end of the intermediate spacer 21 is provided with lower flange portions 202 at both ends in the Y-axis direction.

[0069] In the end spacer 22, the side of the end spacer 22 adjacent to the energy storage element 10 has an upper flange portion 201 at its upper end and a lower flange portion 202 at its lower end. On the other hand, the side of the end spacer 22 opposite to the energy storage element 10 does not have a flange portion 202 and is flat overall.

[0070] The upper flange portion 201 has a concave curved surface 203 that is in close contact with the curved wall portion 141 above the adjacent energy storage element 10. The lower flange portion 202 has a concave curved surface 204 that is in close contact with the curved wall portion 141 below the adjacent energy storage element 10.

[0071] [Positional relationship between the container and electrode body of the energy storage element and the spacer] Next, the positional relationship between the container 100 and electrode body 700 of the energy storage element 10 and the spacer 20 will be explained. Figure 6 is a cross-sectional view showing the positional relationship between the container 100 and electrode body 700 of the energy storage element 10 and the spacer 20 according to the embodiment. In Figure 6, only the upper end of the energy storage element 10 is shown, but the same applies to the lower end.

[0072] As shown in Figure 6, the container 100 of the energy storage element 10 is in close contact with the entire circumference of the electrode body 700. The curved wall portion 141 of the container 100 is in close contact with the curved portion 711 of the electrode body 700, and each second flat wall portion 131 of the container 100 is in close contact with the flat portion 712 of the electrode body 700. Specifically, the inner surface of the curved wall portion 141 is in continuous contact with the entire outer surface of the curved portion 711, and the inner surface of each second flat wall portion 131 is in close contact with the entire outer surface of the flat portion 712.

[0073] In this case, if the electrode body 700 is covered with an insulating sheet, then if the insulating sheet is in close contact with both the electrode body 700 and the container 100, then the electrode body 700 and the container 100 can be said to be indirectly in close contact. In other words, even in this case, the container 100 and the electrode body 700 are included in the close contact.

[0074] The state of close contact between the container 100 and the electrode body 700 is already achieved immediately after the manufacture or shipment of the energy storage device 1. In other words, the electrode body 700 of the energy storage element 10 does not expand and cause the curved wall portion 141 and the curved portion 711 to come into close contact when the energy storage device 1 is used by a user.

[0075] The curved wall portion 141 of the container 100 is in close contact with the upper flange portion 201 of the spacer 20. Specifically, the outer surface of the curved wall portion 141 is in continuous contact with the entire curved surface 203 provided on the upper flange portion 201 of each adjacent spacer 20. On the other hand, each second flat wall portion 131 of the container 100 is in continuous contact with the entire plane between the upper flange portion 201 and the lower flange portion 202 of each adjacent spacer 20.

[0076] In this case, if the container 100 is covered with an insulating sheet, then if the insulating sheet is in close contact with the container 100 and the spacer 20, then it can be said that the container 100 and the spacer 20 are indirectly in close contact. In other words, even in this case, the container 100 and the spacer 20 are included in the statement that they are in close contact.

[0077] [Manufacturing Method for Energy Storage Device] Next, the manufacturing method for the energy storage device will be described. As shown in Figure 2, the assembly 900, which is assembled from a plurality of spacers 20 and a plurality of energy storage elements 10, is arranged in a position where each terminal 300 of each energy storage element 10 is facing upwards and each gas discharge valve 173 is facing downwards. Each energy storage element 10 is arranged along the Y-axis direction. A pair of adjacent energy storage elements 10 are arranged in a position where their second flat wall portions 131 face each other. In this position, each gas discharge valve 173 is arranged linearly along the Y-axis direction.

[0078] The assembly 900 is inserted into the case body 30 through the opening 31. At this time, each exhaust member 50 may be attached to the assembly 900 before insertion, or each exhaust member 50 may be placed in a predetermined position inside the case body 30 before insertion.

[0079] During insertion, in order to ensure that the assembly 900 receives a compressive force from the case body 30 after insertion, the assembly 900 is compressed in the Y-axis direction to be slightly smaller than the opening 31. After inserting approximately the lower half of the assembly 900, insertion is stopped and the compression on the assembly 900 is released. This fixes the assembly 900 to the case body 30.

[0080] In this state, each terminal 300 of each energy storage element 10 is exposed from the case body 30, so each busbar 800 is connected to each terminal 300. Then, the assembly 900 is pushed in until its lower end surface contacts the bottom wall 32 of the case body 30, thereby completing the insertion of the assembly 900 into the case body 30.

[0081] Here, it is also possible to connect each busbar 800 to each terminal 300 of each energy storage element 10 in the assembly 900 before inserting it into the case body 30. However, if the assembly 900 is compressed in the Y-axis direction during insertion, misalignment may occur between each busbar 800 and each terminal 300, potentially damaging the connection points between the busbars 800 and the terminals 300.

[0082] Alternatively, it is possible to connect each busbar 800 to each terminal 300 of each energy storage element 10 while the assembly 900 is compressed before insertion. However, if the compression of the assembly 900 is released after insertion, the assembly 900 will expand slightly, which may cause misalignment between each busbar 800 and each terminal 300, potentially damaging the connection points between the busbars 800 and the terminals 300.

[0083] In this embodiment, as described above, with approximately the upper half of the assembly 900 exposed from the case body 30, the compression on the assembly 900 is released, and then each busbar 800 is connected to each terminal 300. After connection, the assembly 900 is pushed into the case body 30 and fully inserted. In other words, before and after the connection of the busbars 800, the assembly 900 is neither expanded nor compressed to a significant extent, so misalignment between each busbar 800 and each terminal 300 can be suppressed, and consequently, damage to the connection points between the busbars 800 and terminals 300 can also be suppressed. This makes it possible to extend the lifespan of the energy storage device 1.

[0084] Furthermore, the case lid 40 is joined to the case body 30 to create a seal. At this time, the case lid 40 comes into contact with the upper end surface of the assembly 900. As a result, the bottom wall 32 of the case body 30 and the case lid 40 compress the assembly 900 in the Z-axis direction.

[0085] As a result, the assembly 900 is housed in the case body 30 under conditions where it receives a compressive force in the Y-axis direction from the side wall 33 of the case body 30, and a compressive force in the Z-axis direction from the bottom wall 32 of the case body 30 and the case lid 40. The expansion of each energy storage element 10 in the assembly 900 is suppressed by this compressive force. This compressive force also acts on each energy storage element 10 via the spacer 20. In other words, the spacer 20 is structured to compress the container 100 of the energy storage element 10, and furthermore, the electrode body 700. If the electrode body 700 expands due to repeated charging and discharging, the expansion of the electrode body 700 is uniformly compressed by the entire container 100 and the entire spacer 20. Therefore, tensile stress is suppressed between the curved portion 711 and the flat portion 712, which would otherwise cause deformation of the electrode body 700 or fracture of the electrode plates (positive electrode plate 740, negative electrode plate 750).

[0086] [Explanation of Effects] As described above, according to this embodiment, terminals 300 are arranged at the upper ends of each of the pair of first flat wall portions 170 provided on each energy storage element 10, so that the terminals 300 of each energy storage element 10 can be connected with busbars 800 before each energy storage element 10 is fully inserted into the case 2 (outer casing). On the other hand, a gas discharge valve 173 is arranged below the terminal 300 on at least one of the first flat wall portions 170 of each energy storage element 10, so that the gas discharge valves 173 can be arranged in a straight line. This simplifies the gas flow path S inside the case 2. As a result, the manufacturability of the energy storage device 1 can be improved.

[0087] Furthermore, since terminals 300 are located at the upper ends of each pair of first flat wall portions 170 provided on each energy storage element 10, maintenance of the busbars 800 and other components can be performed by exposing only the upper ends, without having to remove the entire assembly 900 from the case 2 during maintenance. In other words, the maintainability of the energy storage device 1 can be improved.

[0088] Since the gas discharge valve 173 is housed in the lower half of the first flat wall portion 170, the gas flow path S inside the case 2 can be formed compactly.

[0089] Since the liquid injection section 171 is provided between the terminal 300 and the gas discharge valve 173, the liquid injection section 171 can be positioned opposite the winding core of the electrode body 700. Therefore, the electrolyte can be injected from the liquid injection section 171 toward the winding core of the electrode body 700, and the electrolyte can be injected into the electrode body 700 in a balanced manner.

[0090] Since the pair of curved portions 711 are in close contact with the pair of curved wall portions 141 and the flat portion 712 is in close contact with the pair of second flat wall portions 131, the outer surface of the electrode body 700 is constrained by each of the curved wall portions 141 and each of the second flat wall portions 131. This constraint suppresses the expansion of the electrode body 700, and thus also suppresses the expansion and contraction that occur during the charging and discharging of the energy storage element 10. In other words, damage to the electrode body 700 caused by expansion and contraction can be suppressed, and the lifespan of the energy storage element 10 can be extended.

[0091] A positive electrode plate 740 having a positive electrode active material layer 742 containing Ni at a molar ratio of 50% or more of the transition metals contained in the active material, and a negative electrode plate 750 having a negative electrode active material layer 752 containing Si at a molar ratio of 5% or more, both have a tendency to expand. Even an electrode body 700 having at least one of the positive electrode plate 740 and the negative electrode plate 750 is preferable because its outer circumferential surface is constrained by each curved wall portion 141 and each second flat wall portion 131, thereby suppressing expansion.

[0092] (Other) Although an energy storage device according to an embodiment of the present invention 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.

[0093] In the above embodiment, an example was given in which the gas discharge valve 173 is housed in the lower half of the first flat wall portion 170, but the gas discharge valve 173 does not have to be housed in the lower half of the first flat wall portion 170.

[0094] In the above embodiment, the example shows that the liquid injection section 171 is located between the terminal 300 and the gas discharge valve 173, but the liquid injection section may be located in other positions.

[0095] In the above embodiment, the case in which the electrode body 700 is in continuous contact with the container 100 over its entire circumference was illustrated, but the electrode body 700 and the container 100 may be partially separated.

[0096] The present invention also includes forms constructed by arbitrarily combining the components included in the above embodiments and their modified examples.

[0097] This invention can be applied to energy storage devices that include energy storage elements such as lithium-ion secondary batteries.

[0098] 1. Energy storage device 2. Case (outer casing) 10. Energy storage element 20. Spacer 30. Case body 40. Case lid 50. Exhaust member 100. Container 131. Second flat wall section 141. Curved wall section 160. Container body 170. First flat wall section 171. Liquid injection section 173. Gas discharge valve 300. Terminal 400. External gasket 500. Internal gasket 600. Current collector 630. First joint section 640. Second joint section 700. Electrode body 710. Main body section 711. Curved section 712. Flat section 720. Tab section 740. Positive electrode plate 741. Positive electrode current collector foil 742. Positive electrode active material layer 750. Negative electrode plate 751. Negative electrode current collector foil 752. Negative electrode active material layer 800. Busbar 900 Assembly L Winding shaft S Gas flow path

Claims

1. An energy storage device comprising a plurality of energy storage elements and an outer casing housing the plurality of energy storage elements, wherein each energy storage element comprises a wound electrode body having a pair of curved portions and a flat portion sandwiched between the pair of curved portions, a container housing the electrode body, and a pair of terminals, part of which are located outside the container and electrically connected to the electrode body, wherein the container comprises a pair of first flat wall portions facing both ends of the electrode body in the winding axis direction, a pair of curved wall portions facing the pair of curved portions, and a pair of second flat wall portions facing each other across the flat portion, wherein the plurality of energy storage elements are arranged such that the pair of curved wall portions are arranged vertically and the second flat wall portions of adjacent pairs of energy storage elements face each other, the terminals are installed at the upper ends of each of the pair of first flat wall portions, and a gas discharge valve is located below the terminal on at least one of the pair of first flat wall portions.

2. The energy storage device according to claim 1, wherein the gas discharge valve is housed in the lower half of the first flat wall portion.

3. The energy storage device according to claim 2, wherein one of the pair of first flat wall portions is provided with an injection portion for injecting an electrolyte into the container, between the terminal and the gas discharge valve.

4. The energy storage device according to any one of claims 1 to 3, wherein the pair of curved portions are in close contact with the pair of curved wall portions, and the flat portion is in close contact with the pair of second flat wall portions.

5. The energy storage device according to claim 4, wherein the electrode body comprises at least one of a positive electrode plate having a positive electrode active material containing Ni in a molar ratio of 50% or more of the transition metals contained in the active material, and a negative electrode plate having a negative electrode active material layer containing Si in a molar ratio of 5% or more.

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