Power storage device

Abstract

This power storage device comprises a power storage element and a holding unit that is disposed outside the power storage element and holds the power storage element. The power storage element comprises an electrode body in which electrode plates are wound, and a container that houses the electrode body. The electrode body has a flat shape that comprises a pair of flat portions facing each other and a pair of curved portions facing each other. The container comprises flat wall portions facing the flat portions of the electrode body, and curved wall portions facing the curved portions of the electrode body. The inner surfaces of the flat wall portions have a flat shape that follows the flat portions. The inner surfaces of the curved wall portions have a curved shape that follows the curved portions. The inner surfaces of the holding unit comprises flat surfaces having a flat shape that follows the outer surfaces of the flat wall portions of the container, and curved surfaces having a curved shape that follows the outer surfaces of the curved wall portions of the container. The inner surfaces of the flat wall portions of the container press the flat portions of the electrode body, and the inner surfaces of the curved wall portions of the container press the curved portions of the electrode body. The flat surfaces of the holding unit press the outer surfaces of the flat wall portions of the container, and the curved surfaces of the holding unit press the outer surfaces of the curved wall portions of the container.

Description

Power storage device

[0001] The present invention relates to an electricity storage device.

[0002] For example, Patent Document 1 discloses a nonaqueous electrolyte battery in which a wound electrode body is housed in a square container.

[0003] JP 2010-73580 A

[0004] In the conventional battery containing the electrode assembly wound in the rectangular container, the space inside the container is rectangular, so the inner wall of the container does not conform to the outer surface of the curved portion of the electrode assembly. When the electrode assembly expands during charging and discharging, the expansion of the electrode assembly tends to progress at the curved portion of the electrode assembly that is not compressed by the inner wall of the container. As a result, tensile stress (reaction force) is concentrated between the curved portion and the flat portion of the electrode assembly, causing problems that lead to damage to the electrode plate or to electrode deformation that can cause lithium electrodeposition, leading to a decrease in capacity. Furthermore, when an active material with large expansion is used, significant distortion occurs, which may ultimately lead to foil breakage.

[0005] An object of the present invention is to provide an electricity storage device that can prevent deformation of the electrode body, which may cause lithium electrodeposition, even when a highly expandable active material is used, and can suppress damage to the electrode body.

[0006] An energy storage device according to one aspect of the present invention includes an energy storage element and a holding unit disposed outward of the energy storage element and holding the energy storage element, the energy storage element including an electrode body having electrode plates wound thereon and a container accommodating the electrode body, the electrode body having a flat shape with a pair of opposing flat portions and a pair of opposing curved portions, the container including a flat wall portion opposing the flat portions of the electrode body and a curved wall portion opposing the curved portions of the electrode body, the inner surface of the flat wall portion having a flat shape that conforms to the flat portions and the inner surface of the curved wall portion having a , and has a curved shape that follows the curved portion, and the inner surface of the holding unit has a flat surface that is flat and follows the outer surface of the flat wall portion of the container, and a curved surface that is curved and follows the outer surface of the curved wall portion of the container, and the inner surface of the flat wall portion of the container presses against the flat portion of the electrode body, the inner surface of the curved wall portion of the container presses against the curved portion of the electrode body, the flat surface of the holding unit presses against the outer surface of the flat wall portion of the container, and the curved surface of the holding unit presses against the outer surface of the curved wall portion of the container.

[0007] According to the present invention, it is possible to provide an electricity storage device that can prevent deformation of the electrode body, which may cause lithium electrodeposition, and can suppress damage to the electrode body.

[0008] FIG. 1 is a perspective view showing the appearance of an energy storage device according to an embodiment. FIG. 2 is an exploded perspective view showing each component when the energy storage device according to the embodiment is disassembled. FIG. 3 is a perspective view showing the appearance of an energy storage element according to an embodiment. FIG. 4 is an exploded perspective view showing each component when the energy storage element according to the embodiment is disassembled. FIG. 5 is a perspective view showing the configuration of an electrode body according to an embodiment. FIG. 6 is an explanatory diagram showing a holding unit, a case, and each energy storage element according to an embodiment. FIG. 7 is a cross-sectional view showing a state in which the electrode body is accommodated in a prismatic container according to Comparative Example 1. FIG. 8 is a cross-sectional view showing a state in which the electrode body is accommodated in a prismatic container according to Comparative Example 2. FIG. 9 is a cross-sectional view showing the positional relationship between a holding unit, a container, and an electrode body according to an embodiment. FIG. 10 is an explanatory diagram showing a holding unit, a case, and each energy storage element according to Modification Example 1. FIG. 11 is an explanatory diagram showing a holding unit, a case, and each energy storage element according to Modification Example 2. FIG. 12 is a perspective view showing the appearance of an energy storage element according to Modification Example 3. FIG. 13 is a perspective view showing the appearance of an energy storage element according to Modification Example 4. Fig. 14 is a perspective view showing the appearance of an energy storage element according to Modification 5. Fig. 15 is a perspective view showing the appearance of an energy storage element according to Modification 6. Fig. 16 is a perspective view showing the appearance of an energy storage element according to Modification 7.

[0009] (Findings of the Inventors) The inventors considered the possibility of suppressing the tensile stress occurring in the curved portion of the electrode body and between the curved and flat portions of the electrode body by aligning the inner surface of the wall portion (curved wall portion) of the container facing the curved portion of the electrode body with the curved shape of the curved portion and reducing the space between the curved portion and the curved wall portion, thereby avoiding a situation in which expansion in the curved portion of the electrode body proceeds more easily than expansion in the flat portion of the electrode body when a rectangular container is used, reducing the difference in the degree of progress between the ease of expansion in the curved portion of the electrode body and the ease of progress in the flat portion of the electrode body, and by making the container compress the electrode body. Here, the inventors considered the possibility that the container would be deformed because the strength of the container wall could not withstand the expansion of the curved portion of the electrode body, resulting in insufficient compressive force on the electrode body, and studied an energy storage device including a holding unit. They then discovered a configuration in which the inner surface of the holding unit is provided with a curved surface that is curved along the outer surface of the curved wall portion of the container, and when the container is compressed by the holding unit, the electrode body is compressed via the container. This allows the pressure from the holding unit to be transmitted to the electrode body via the container, making it possible to apply a pressure to the electrode body that exceeds the strength of the container wall and suppress deformation of the container due to expansion of the electrode body.As a result, it is possible to suppress tension generated at the boundary between the flat and curved parts of the electrode body and suppress defects in the electrode body.

[0010] (1) A storage battery comprising: an energy storage element; and a holding unit disposed outward of the energy storage element and holding the energy storage element, wherein the energy storage element comprises an electrode body having an electrode plate wound thereon; and a container accommodating the electrode body, wherein the electrode body has a flat shape having a pair of opposing flat portions and a pair of opposing curved portions, and the container comprises a flat wall portion opposing the flat portions of the electrode body and a curved wall portion opposing the curved portions of the electrode body, wherein the inner surface of the flat wall portion has a flat shape that conforms to the flat portions, and the inner surface of the curved wall portion conforms to the curved portions. The holding unit has a curved shape that follows the outer surface of the flat wall portion of the container, and the inner surface of the holding unit has a flat surface that follows the outer surface of the flat wall portion of the container and a curved surface that follows the outer surface of the curved wall portion of the container, and the inner surface of the flat wall portion of the container presses against the flat portion of the electrode body, the inner surface of the curved wall portion of the container presses against the curved portion of the electrode body, the flat surface of the holding unit presses against the outer surface of the flat wall portion of the container, and the curved surface of the holding unit presses against the outer surface of the curved wall portion of the container.

[0011] According to an aspect of the present invention, the container includes a flat wall portion facing the flat portion of the electrode body and a curved wall portion facing the curved portion of the electrode body, and the inner surface of the flat wall portion, which has a flat shape that conforms to the flat portion of the electrode body, presses against the flat portion of the electrode body, and the inner surface of the curved wall portion, which has a curved shape that conforms to the curved portion of the electrode body, presses against the curved portion of the electrode body. By compressing both the flat portion and the curved portion of the electrode body by the container in this way, the space (excess space) that occurs between the curved portion of the electrode body and the inner surface of the container in the case of a conventional rectangular container is eliminated, and it is possible to suppress a situation in which the expansion of the curved portion of the electrode body is relatively more likely to proceed than the expansion of the flat portion of the electrode body.

[0012] The following describes how electrode assembly expansion generally progresses in a conventional structure in which a wound electrode assembly is housed in a rectangular container. At the beginning of the life of an energy storage device, the electrode plates constituting the flat portion of the electrode assembly expand in the thickness direction and also elongate in the longitudinal direction. However, at the end of the life of the energy storage device, the expansion in the thickness direction of the electrode assembly is restricted by pressure from the inner surface of the container, increasing the frictional force between the inner surface of the container and the electrode assembly. This makes it difficult for the electrode plates to expand in the longitudinal direction. Meanwhile, at the curved portion of the electrode assembly, even at the end of the life of the energy storage device, there remains space (excess space) between the electrode assembly and the inner surface of the container, allowing the electrode plates to continue to expand in the longitudinal direction. This causes strong tensile stress in the electrode plates located at the boundary between the flat and curved portions of the electrode assembly, which, in the worst case, can lead to electrode fracture. Therefore, the inventors devised a power storage device according to one embodiment of the present invention, in which the container of a power storage element using a wound electrode body is shaped to fit along the outer periphery (outer surface) of the electrode body, and the electrode body is compressed by the container, and a holding unit structured to fit along the outer periphery (outer surface) of the container is used outside the container to compress the outer surface of the container.

[0013] Specifically, a state in which the flat portion of the electrode body is compressed by the flat wall portion of the container and the curved portion of the electrode body is compressed by the curved wall portion of the container, with the flat surface of the holding unit compressing the outer surface of the flat wall portion of the container and the curved surface of the holding unit compressing the outer surface of the curved wall portion of the container, is considered to be an energy storage device according to one aspect of the present invention. That is, the holding unit can compress the flat portion of the electrode body via the flat wall portion of the container and the curved portion of the electrode body via the curved wall portion of the container. As a result, a combined compressive force is applied to the flat portion of the electrode body, consisting of the compressive force from the flat wall portion of the container and the compressive force from the flat surface of the holding unit. Similarly, a combined compressive force is applied to the curved portion of the electrode body, consisting of the compressive force from the curved wall portion of the container and the compressive force from the curved wall portion of the holding unit. As a result, a compressive force large enough to suppress expansion of the electrode body and exceeding the strength of the container can be applied to the electrode body, thereby suppressing deformation of the container due to expansion of the electrode body. As a result, tension generated at the boundary between the flat portion and the curved portion of the electrode body can be suppressed, thereby suppressing defects in the electrode body. Examples of defects in the electrode body include deformation of the electrode body, which may cause lithium electrodeposition, a decrease in the capacity of the storage element, and damage to the electrode body due to foil breakage, etc. The stress applied to the container and the holding unit is designed to be within the elastic range of their respective materials.

[0014] (2) The energy storage device described in (1) above may be provided with an external member or case positioned outward from the holding unit, and the external member or case may fix or house the holding unit, and the outer surface of the holding unit may be pressed against the external member or case, so that the curved surface of the holding unit presses against the outer surface of the curved wall portion of the container of the energy storage element, and the flat surface of the holding unit presses against the outer surface of the flat wall portion of the container of the energy storage element.

[0015] According to the energy storage device described in (2) above, a large compressive force is applied to the curved portion of the electrode assembly by three forces: a compressive force from an external member or case, a compressive force from the curved surface of the holding unit, and a compressive force from the curved wall of the container. At this time, the curved surface of the inner surface of the holding unit can be said to be pressing against the curved wall of the container, and a large compressive force is also applied to the curved wall of the container by the compressive force from the external member or case and the compressive force from the holding unit. Furthermore, deformation of the container due to expansion of the curved portion of each electrode assembly can be more reliably suppressed. In addition, because each curved portion of the electrode assembly is compressed by each curved wall of the container and each flat portion of the electrode assembly is compressed by each flat wall of the container, expansion is suppressed at both the curved portion and the flat portion of the electrode assembly, and an increase in tensile stress at the boundary between the curved portion and the flat portion can be suppressed. As a result, expansion of the curved portion of the electrode assembly and the resulting deformation of the container can be further suppressed, resulting in more suppressed foil tearing of the electrode assembly. Here, examples of methods for applying pressure to the holding unit from an external member or a case include a method of applying pressure to an integrated unit (block) formed by assembling the holding unit and the energy storage element and forcing it into a fixed-size case while compressing it, and a method of placing an integrated unit (block) formed by integrating the holding unit and the energy storage element into a fixed-size case, inserting a member between the case and the block, and applying pressure, etc. Note that the method of applying pressure to the holding unit from an external member or a case in the present invention is not limited to the examples.

[0016] (3) In the energy storage device described in (2) above, the holding unit may include a plurality of holding members arranged in a direction in which the flat portion of the electrode body and the flat wall portion of the container face each other, and the inner surface of the holding member may include the flat surface that presses against the outer surface of the flat wall portion of the container and the curved surface that presses against the outer surface of the curved wall portion of the container.

[0017] According to the energy storage device described in (3) above, each holding member integrally includes a flat surface that presses against the flat wall portion and a curved surface that presses against the curved wall portion, so that the holding member can suppress both expansion of the flat portion of the electrode body via the flat wall portion of the container and expansion of the curved portion of the electrode body via the curved wall portion of the container. In other words, the entire electrode body can be compressed with an energy storage device having a simple configuration, and as a result, defects in the electrode body can be more reliably suppressed.

[0018] (4) In the energy storage device described in (2) above, the holding unit may include a pair of first holding members that sandwich the energy storage element in a direction in which the curved portion of the electrode body and the curved wall portion of the container face each other, and a pair of second holding members that sandwich the energy storage element in a direction in which the flat portion and the flat wall portion face each other, and the pair of first holding members and the pair of second holding members may be separate members, and the inner surface of the first holding member may have the curved surface that presses against the curved wall portion of the container, and the inner surface of the second holding member may have the flat surface that presses against the flat wall portion of the container.

[0019] According to the energy storage device described in (4) above, since the first and second holding members are separate, the first and second holding members do not need to be installed simultaneously, facilitating the manufacture of the energy storage device. Furthermore, the compressive force applied from the first holding member to the curved wall portion of the container and the compressive force applied from the second holding member to the flat wall portion of the container can be adjusted independently. This allows for a reduction in manufacturing costs by repurposing either the first or second holding member, even if the size of the energy storage element changes due to a design change or model change, as long as the container shape remains partially the same.

[0020] (5) The energy storage device according to (4) above, further comprising a plurality of the energy storage elements, the plurality of energy storage elements including a first energy storage element and a second energy storage element, the first energy storage element comprising a first electrode body having the same configuration as the electrode body and a first container having the same configuration as the container, the first electrode body having a flat shape with a first flat portion having the same configuration as the flat portion and a first curved portion having the same configuration as the curved portion, the first container comprising a first flat wall portion having the same configuration as the flat wall portion and a first curved wall portion having the same configuration as the curved wall portion, the second energy storage element comprising a second electrode body having the same configuration as the electrode body and a second container having the same configuration as the container, the second electrode body having a flat shape with a second flat portion having the same configuration as the flat portion and a second curved portion having the same configuration as the curved portion, the first container of the first energy storage element and the second container of the second energy storage element are arranged so that a surface of the first flat wall portion of the first container faces a surface of the second flat wall portion of the second container of the second energy storage element; the inner surface of the first holding member has a plurality of curved surfaces integrated together, the plurality of curved surfaces including a first curved surface facing the first curved wall portion and a second curved surface facing the second curved wall portion; the outer surface of the first curved wall portion of the first container is pressed against the first curved surface of the first holding member, thereby compressing the first curved portion of the first electrode body; and the outer surface of the second curved wall portion of the second container is pressed against the second curved surface of the first holding member, thereby compressing the second curved portion of the second electrode body.

[0021] According to the energy storage device described in (5) above, the multiple curved surfaces (first curved surface, second curved surface) of the first holding member face the respective curved wall portions of the multiple energy storage elements (first energy storage element, second energy storage element), and therefore the multiple curved surfaces (first curved surface, second curved surface) of the first holding member can collectively compress the multiple curved wall portions (first curved wall portion, second curved wall portion). Furthermore, since fewer first holding members are required than when one first holding member is disposed for one curved wall portion, assembly of the energy storage device is facilitated. Furthermore, although the first energy storage element and the second energy storage element have been described here, it is obvious that one first holding member may have multiple curved surfaces facing the respective curved wall portions of two or more multiple energy storage elements.

[0022] (6) In the electricity storage device described in (1) to (5) above, the holding unit may be made of foamed resin.

[0023] According to the energy storage device described in (6) above, the holding unit is made of a foamed resin, which allows it to be easily formed to fit the shape of the curved wall of the container during manufacturing. Furthermore, forming the holding unit from a foamed resin allows for weight reduction and ease of manufacturing. Various methods for forming the holding unit from a foamed resin are conceivable. The holding unit may be formed by placing the energy storage element inside the energy storage device and then filling and solidifying the foamed resin. Alternatively, pre-formed components constituting the holding unit may be assembled together with the energy storage element, etc. The holding unit may be composed of a combination of a portion filled as foamed resin inside the energy storage device and then solidified, and a portion pre-formed before assembling the energy storage device. For example, the energy storage element and a second holding member (part of the holding unit) facing the flat wall of the energy storage element may be positioned within the energy storage device, and then foamed resin may be filled to form a first holding member (part of the holding unit) facing the curved wall of the energy storage element. In this example, a pre-formed second holding member (part of the holding unit) with a fixed shape is placed inside the energy storage device together with the energy storage element. Furthermore, the second holding member (part of the holding unit) may be formed from a foamed resin, or from a material different from the foamed resin. Alternatively, the holding unit may be formed by positioning the energy storage element, and then filling and solidifying the foamed resin once or multiple times. Each component of the holding unit, which has a pre-formed shape, may be assembled together with the energy storage element. The holding unit is formed from a material that has sufficient strength even for a foamed resin and has a sufficient elastic region to suppress expansion of the electrode body. The entire holding unit may be formed from a foamed resin, or only a portion of the holding unit may be formed from a foamed resin.

[0024] (7) In the power storage device described in (1) to (6) above, the holding unit may include a coolant passage through which a coolant flows.

[0025] According to the power storage device described in (7) above, since the holding unit has a refrigerant path, the container can be efficiently cooled via the holding unit. Furthermore, it is obvious that if a heat medium for heating is passed through the refrigerant path, it can be used as a heating method.

[0026] (Embodiments) Hereinafter, with reference to the drawings, a description will be given of an energy storage device and an energy storage element according to an embodiment of the present invention (including modifications thereof). The embodiments described below all show comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, manufacturing processes, and the order of manufacturing processes shown in the following embodiments are examples and are not intended to limit the present invention. In each drawing, dimensions and the like are not strictly illustrated. In each drawing, the same or similar components are assigned the same reference numerals. The names of the components (each component) in this embodiment are those used in this embodiment and may differ from the names of the components (each component) in the background art.

[0027] In the following description and drawings, the longitudinal direction of the energy storage element and the winding axis direction of the electrode body provided in the energy storage element are defined as the X-axis direction. The arrangement direction of the multiple energy storage elements and the thickness direction of the container of the energy storage element are defined as the Y-axis direction. The arrangement direction of the case lid and case body of the energy storage device, or the up-down 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 mode, the Z-axis may not be the up-down direction, but for convenience of explanation, the following description will be made assuming that the Z-axis direction is the up-down direction.

[0028] In the following description, the term "insulation" means "electrical insulation." An insulating material has a volume resistivity of 1×10 １０ It is preferable that the material be made of a material with a resistance of Ωm or more.

[0029] In the following description, the positive X-axis direction refers to the direction of the X-axis arrow, and the negative X-axis direction refers to the direction opposite to the positive X-axis direction. The same applies to the Y-axis and Z-axis directions. Furthermore, expressions indicating relative directions or attitudes, such as parallel and perpendicular, also include cases where the direction or attitude is not strictly that. "Two directions are perpendicular" does not only mean that the two directions are completely perpendicular, but also means that the directions are substantially perpendicular, i.e., there is a difference of about a few percent.

[0030] [Description of Energy Storage Device] First, a schematic configuration of an energy storage device 1 according to the present embodiment will be described. Fig. 1 is a perspective view showing the appearance of the energy storage device 1 according to the embodiment. Fig. 2 is an exploded perspective view showing each component of the energy storage device 1 according to the embodiment.

[0031] The power storage device 1 is a device capable of charging with electricity from an external source or discharging electricity to an external source, and in this embodiment, has a substantially rectangular parallelepiped shape. The rectangular parallelepiped here refers to a hexahedron with all sides formed of rectangles or squares. The power storage device 1 is a battery module (battery assembly) used for power storage, power supply, or other purposes. Specifically, the power storage device 1 is used as a battery for driving or starting the engine of a moving object such as an automobile, motorcycle, personal watercraft, ship, snowmobile, agricultural machinery, construction machinery, automatic guided vehicle (AGV), or electric railway vehicle. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicle. Examples of the electric railway vehicle include a train, a monorail, a linear motor car, and a hybrid train equipped with both a diesel engine and an electric motor. The power storage device 1 can also be used as a stationary battery for home or business use.

[0032] 1 and 2 , the energy storage device 1 includes a case 2. The case 2 accommodates a plurality of energy storage elements 10, a holding unit 20, a pair of exhaust members 50, a plurality of bus bars (not shown), and the like. The energy storage device 1 also includes external terminals (positive and negative external terminals) for electrically connecting to an external device, but these are not shown or described here. In addition to the above components, the energy storage device 1 may also include restraining members (end plates, side plates, etc.) that restrain the plurality of energy storage elements 10, bus bar holders that hold the bus bars, bus bar covers, circuit boards that monitor or control the charge and discharge states of the energy storage elements 10, and electrical components such as relays, fuses, shunt resistors, and connectors.

[0033] The case 2 is a container (case) having a substantially rectangular parallelepiped (box-shaped) shape that constitutes the exterior body (housing, outer shell) of the energy storage device 1. The case 2 is an example of an external member. The case 2 is arranged outside the plurality of energy storage elements 10 and the holding unit 20, etc., and presses against the plurality of energy storage elements 10 and the holding unit 20, etc. The case 2 is a metal case formed from a metal member such as aluminum, aluminum alloy, stainless steel, iron, or plated steel sheet. The case 2 may be formed from an insulating material such as a resin material. When the case 2 is formed from a conductive material, the inner surface of the case 2 may be coated with an insulating material to ensure insulation from the energy storage elements 10.

[0034] 2, the case 2 includes a case main body 30 that constitutes the main body of the case 2, and a case lid 40 that constitutes the lid of the case 2. The case main body 30 is a rectangular cylindrical housing (chassis) with a bottom and an opening 31 formed in the positive direction of the Z axis, and houses a plurality of energy storage elements 10, holding units 20, etc.

[0035] Specifically, the case body 30 includes a bottom wall 32 and a side wall 33. The bottom wall 32 is a flat, rectangular portion disposed at the end of the case body 30 in the negative Z-axis direction.

[0036] The side wall 33 is a rectangular annular wall extending from the outer periphery of the bottom wall 32 in the positive Z-axis direction and is provided continuously around the entire circumference of the bottom wall 32. The opening 31 is located inside the side wall 33. A pair of exhaust ports 37 is provided in the side wall 33, and in this embodiment, they are arranged in the negative Z-axis direction within the side wall 33. Of the pair of exhaust ports 37, one exhaust port 37 is arranged in the negative Z-axis direction and the negative X-axis direction, and the other exhaust port 37 is arranged at a corner in the negative Z-axis direction and the positive X-axis direction. In other words, both of the pair of exhaust ports 37 are arranged at corners of the case body 30. Each exhaust port 37 connects the inside and outside of the case 2 and exhausts gas discharged from each energy storage element 10 to the outside of the case 2.

[0037] 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 joined by welding, adhesive bonding, screwing, or the like to seal the case 2. The case body 30 and the case lid 40 may be made of the same material or different materials.

[0038] The energy storage element 10 has a shape that is longer in the X-axis direction than in the Y-axis direction, specifically, an elongated cylindrical shape that is flattened in the Y-axis direction. In this embodiment, eight energy storage elements 10 are arranged 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. A detailed description of the configuration of the energy storage elements 10 will be given later.

[0039] The holding unit 20 holds each energy storage element 10. In this embodiment, the holding unit 20 includes a plurality of holding members 21 arranged in the Y-axis direction. One energy storage element 10 is disposed between two holding members 21 adjacent to each other in the Y-axis direction. Details of the holding unit 20 will be described later.

[0040] The exhaust member 50 is a member that forms a flow path through which gas discharged from at least one energy storage element 10 flows to the outside of the case 2. In this embodiment, the energy storage device 1 includes a pair of exhaust members 50. Each exhaust member 50 is disposed at an end in the X-axis direction within the case body 30, and is a member that faces the gap between each energy storage element 10 and each holding member 21 and covers the gap.

[0041] The exhaust member 50 has a first plate portion 51 and a second plate portion 52 bent relative to the first plate portion 51. The first plate portion 51 is a rectangular plate-shaped portion parallel to the YZ plane and elongated in the Y-axis direction. The second plate portion 52 is a rectangular plate-shaped portion parallel to the XY plane and elongated in the Y-axis direction. The first plate portion 51 overlaps a portion of the second recessed portion 102 of each energy storage element 10 that forms the space S2. The second plate portion 52 overlaps another portion of the second recessed portion 102 of each energy storage element 10 that forms the space S2. As a result, within the space S2, the first plate portion 51 and the second plate portion 52 cover the gaps between adjacent energy storage elements 10 and the gaps between adjacent energy storage elements 10 and holding members 21.

[0042] The second plate portion 52 has a plurality of vent holes 53 at positions corresponding to the gas exhaust valves 800 of the respective energy storage elements 10. When the gas exhaust valve 800 of a given energy storage element 10 is opened to exhaust gas, the gas enters the space S2 through the vent holes 53. The vent holes 53 are preferably larger than the gas exhaust valves 800. A ring-shaped sealant may be disposed around the vent holes 53 between the second plate portion 52 and the energy storage elements 10. The sealant is made of rubber or porous resin. The sealant prevents the gas from leaking out of the space S2. The gas flows through the space S2 and is exhausted through the exhaust port 37. At this time, the exhaust member 50 covers the gaps between adjacent energy storage elements 10 and the gaps between adjacent energy storage elements 10 and the holding member 21, thereby preventing gas from entering these gaps. Although an L-shaped exhaust member 50 is shown here as an example when viewed from the Y-axis direction, it may be U-shaped or have a square tube shape. In any shape, it is sufficient that vent holes are formed in locations corresponding to the gas exhaust valves of each energy storage element.

[0043] The busbars are connected (joined) to terminals 300 provided on the plurality of energy storage elements 10. Specifically, the plurality of busbars connect the terminals 300 of two adjacent energy storage elements 10 among the plurality of energy storage elements 10, and electrically connect the terminals 300 of the end energy storage elements 10 to an external terminal. The connection form of the busbars is not particularly limited, and the plurality of energy storage elements 10 may be connected in series or in parallel in any combination, or all of the energy storage elements 10 may be connected in series or in parallel. The busbars and the terminals 300 are connected (joined) by welding or the like, but the connection form is not particularly limited. The busbars are formed of a conductive member made of a metal such as aluminum, an aluminum alloy, copper, a copper alloy, or Ni, or a combination thereof, or a conductive member other than a metal.

[0044] [Description of Energy Storage Element] The energy storage element 10 according to the embodiment will be generally described with reference to Fig. 3 and Fig. 4. Fig. 3 is a perspective view showing the appearance of the energy storage element 10 according to the embodiment. Fig. 4 is an exploded perspective view showing the components of the energy storage element 10 according to the embodiment.

[0045] The energy storage element 10 is an energy storage element that can be charged with electricity from an external source or can discharge electricity to an external source. The energy storage element 10 is not limited to a nonaqueous electrolyte secondary battery, and may be a secondary battery other than a nonaqueous electrolyte secondary battery. The energy storage element 10 may be an all-solid-state lithium battery using a solid electrolyte or a polymer lithium battery. The energy storage element 10 may be a pouch-type energy storage element. In this embodiment, the energy storage element 10 is illustrated based on a flat, oval cylindrical shape. However, the shape of the energy storage element 10, i.e., the shape of the container 100, is not limited to a shape based on a flat, oval cylindrical shape, and may be a shape based on a polygonal prism, an elliptical cylinder, a cylindrical shape, or the like, as long as it conforms to the outer surface of the electrode assembly 700 described below.

[0046] 3 and 4 , in this embodiment, the energy storage element 10 includes the container 100, a pair of terminals 300, and a pair of external gaskets 400 outside the container 100, and a pair of internal gaskets 500, a pair of current collectors 600, and an electrode assembly 700 housed inside the container 100. Specifically, the positive electrode components are arranged on a first side surface 110, which is the outer surface of the container 100 in the positive X-axis direction. Examples of the positive electrode components include the terminal 300, the external gasket 400, the internal gasket 500, and the current collector 600. In other words, the first side surface 110 is a portion that forms the outer surface of the lid 170 that covers the end of the container 100 in the positive X-axis direction, and the positive electrode components are arranged on the first side surface 110. In this embodiment, the first side portion 110 is a portion in the X-axis direction that is within a range of 1% to 10% of the length of the container 100 from the end face of the container 100 in the positive X-axis direction, but if the length of the container 100 in the X-axis direction is less than three times the length of the container 100 in the Z-axis direction, the range of the length of the container 100 in the X-axis direction may be greater than 10%.

[0047] The negative electrode components are disposed on the second side surface 120, which is the outer surface of the container 100 in the negative X-axis direction. Examples of the negative electrode components include a terminal 300, an external gasket 400, an internal gasket 500, and a current collector 600. In other words, the second side surface 120 is a surface that constitutes the outer surface of the lid 170 that covers the end of the container 100 in the negative X-axis direction, and the negative electrode components are disposed on the second side surface 120. The second side surface 120 is a portion that is within a range of 1% to 10% of the length of the container 100 in the X-axis direction from the end surface of the container 100 in the negative X-axis direction. However, if the length of the container 100 in the X-axis direction is less than three times the length of the container 100 in the Z-axis direction, the range of the length of the container 100 in the X-axis direction may be greater than 10%.

[0048] An electrolyte solution (nonaqueous electrolyte) is sealed inside the container 100, but is not shown in the figure. The type of electrolyte 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, spacers may be disposed on the sides, above, or below the electrode body 700, or an insulating film or the like that encases the electrode body 700 or the like may be disposed.

[0049] The container 100 is a case having an outer shape based on an oval cylindrical shape that is long in the X-axis direction and flattened in the Y-axis direction. In this embodiment, the length of the container 100 in the X-axis direction is at least three times the length of the container 100 in the Z-axis direction, and the length of the container 100 in the X-axis direction is at least five times the length of the container 100 in the Y-axis direction. In FIG. 3 , the oval cylindrical region that serves as the outer shape of the container 100 is illustrated by a two-dot chain line L1. In this embodiment, the container 100 has notches at each end of the electrode body 700 in the winding axis direction (X-axis direction), at the end in the positive Z-axis direction and the end in the negative Z-axis direction. In other words, the container 100 has two notches (a pair of notches) at the end in the positive X-axis direction of the container 100 and two notches (a pair of notches) at the end in the negative X-axis direction of the container 100, for a total of four notches (pairs of notches). Each notch is a cutout at a corner of the container 100, and is rectangular when viewed in the Y-axis direction. In other words, the container 100 has an outer shape that is elongated in the X-axis direction and flattened in the Y-axis direction, with rectangular notches formed at the top and bottom of both ends of the container 100 in the X-axis direction. Each notch can be considered a recess formed by recessing a portion of the oval cylindrical shape. Of the multiple notches, a pair of notches located at the top of the container 100 are first recesses 101, and a pair of notches located at the bottom of the container 100 are second recesses 102. A terminal 300 is disposed in the first recess 101, and a gas release valve 800 (see FIGS. 3 and 4 ) is disposed in the second recess 102. Specifically, the gas release valve 800 is disposed on the surface of the second recess 102 facing the negative Z-axis direction (first lower surface 114 and second lower surface 124; described below). The gas release valve 800 is a safety valve that releases pressure inside the container 100 if the pressure rises excessively.

[0050] The container 100 includes a container body 160 and a pair of lids 170, and the container body 160 and each lid 170 are assembled together to form a cylindrical shape that is long in the X-axis direction. The container body 160 includes a pair of flat wall portions 131 and a pair of curved wall portions 141, 151, and is formed into a cylindrical shape that is long in the X-axis direction, with the pair of flat wall portions 131 and the pair of curved wall portions 141, 151 penetrating the X-axis direction. Each lid 170 of the pair of lids 170 is a plate-shaped 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 lid 170 located in the negative X-axis direction closes the end of the container body 160 in the negative X-axis direction, and the lid 170 located in the positive X-axis direction closes the end of the container body 160 in the positive X-axis direction. Each lid 170 is formed by stamping a metal piece into a flat shape and bending it so that it matches the shape of the end of the opposing container body 160 in the X-axis direction.

[0051] With this configuration, the container 100 has a structure in which the electrode assembly 700 and the like are housed inside the container body 160, and then the container body 160 and the lid 170 are joined by welding or the like, thereby sealing the interior. The material of the container 100 (container body 160 and lid 170) is not particularly limited, but a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet is preferred.

[0052] Although not shown here, a liquid injection portion is formed in the container body 160 or the lid 170. The liquid injection portion is a portion for injecting an electrolyte into the container 100 when manufacturing the energy storage element 10.

[0053] The container body 160 includes a pair of flat wall portions 131 and a pair of curved wall portions 141, 151. 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. The inner surface of each curved wall portion 141 has a curved shape that follows the curved portion 711 of the electrode body 700. Specifically, the inner surface of the curved wall portion 141 in the positive Z-axis direction is curved so as to be concave in the positive Z-axis direction, and the inner surface of the curved wall portion 151 in the negative Z-axis direction is curved so as to be concave in the negative Z-axis direction. In this embodiment, the outer surfaces of the curved wall portions 141, 151 are also curved, with the curved wall portion 141 formed like a curved plate that protrudes in the positive Z-axis direction and the curved wall portion 151 formed like a curved plate that protrudes in the negative Z-axis direction. Each flat wall portion 131 of the pair of flat wall portions 131 is a wall portion that is elongated in the X-axis direction and faces the flat portion 712 of the electrode body in the Y-axis direction. Each flat wall portion 131 is formed in a flat plate shape parallel to the XZ plane, and the inner surface of the flat wall portion 131 is arranged along the flat portion 712 of the electrode body 700. In this embodiment, the end of each flat wall portion 131 has a portion that protrudes in the X-axis direction more than the other portions so that the end of each flat wall portion 131 and the end of the bent lid body 170 are joined without gaps. Specifically, the central portion in the Z-axis direction of the lid body 170 is bent so as to protrude in the X-axis direction, and therefore the central portion in the Z-axis direction of the end of the X-axis direction of the flat wall portion 131 protrudes in the X-axis direction more than the other portions of the end of the flat wall portion 131.

[0054] In the container body 160, the outer surface of each flat wall portion 131 comprises a long side surface 130, the outer surface of the curved wall portion 141 comprises a top surface 140, and the outer surface of the curved wall portion 151 comprises a bottom surface 150. The long side surfaces 130 are long in the X-axis direction and parallel to the XZ plane, and a pair of long side surfaces 130 face each other back to back in the Y-axis direction. The top surface 140 is long in the X-axis direction and curved to protrude in the positive direction of the Z-axis along the curved portion 711 of the electrode body 700, and is located further in the positive direction of the Z-axis than the long side surfaces 130. The bottom surface 150 is long in the X-axis direction and curved to protrude in the negative direction of the Z-axis along the curved portion 711 of the electrode body 700, and is located further in the negative direction of the Z-axis than the long side surfaces 130.

[0055] The outer surface of the pair of lid bodies 170 in the positive direction of the X-axis includes a first side surface portion 110. The first side surface portion 110 includes a first upper side surface 111, a first upper surface 112, a first middle side surface 113, a first lower surface 114, and a first lower surface 115. The first upper side surface 111 and the first lower surface 115 are parallel to the YZ plane. The first upper side surface 111, the first middle side surface 113, and the first lower surface 115 are parallel to the YZ plane. The first upper side surface 111 is continuous with the first upper surface 112 and is the surface of the outer surface of the lid body 170 in the positive direction of the X-axis that is located furthest in the positive direction of the Z-axis. The first lower surface 115 is continuous with the first lower surface 114 and is the surface of the outer surface of the lid body 170 in the positive direction of the X-axis that is located furthest in the negative direction of the Z-axis. The first middle side surface 113 is a surface that is continuous with the first upper surface 112 and the first lower surface 114, and is disposed at a position sandwiched in the Z-axis direction between the first upper side surface 111 and the first lower side surface 115 when viewed from the X-axis direction. Of the pair of lid bodies 170, the outer surface of the lid body 170 in the negative X-axis direction includes a second side surface portion 120. The second side surface portion 120 includes a second upper side surface 121, a second upper surface 122, a second middle side surface 123, a second lower surface 124, and a second lower side surface 125. The configuration of the outer surfaces of the lid body 170 in the negative X-axis direction is the same as the configuration of the outer surfaces of the lid body 170 in the positive X-axis direction, and therefore description thereof will be omitted.

[0056] The terminals 300 are terminals (positive electrode terminal and negative electrode terminal) electrically connected to the electrode body 700 via the current collector 600. In other words, the terminals 300 are metal members for conducting electricity stored in the electrode body 700 to the external space of the energy storage element 10, or for introducing 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 formed of a conductive material such as aluminum, an aluminum alloy, copper, or a copper alloy. The terminals 300 are connected (joined) to the current collector 600 by crimping, welding, or the like, and are attached to the lid body 170.

[0057] In the present embodiment, the terminal 300 includes a terminal body 330 and a shaft 340 protruding from the terminal body 330. The terminal body 330 is a portion protruding outward from the terminal installation surface of the container 100. Here, the terminal installation surface is the surface facing the positive direction of the Z axis in each first recess 101, the terminal installation surface located in the positive direction of the X axis is the first upper surface 112, and the terminal installation surface located in the negative direction of the X axis is the second upper surface 122. In the present embodiment, the terminal body 330 protrudes outward from the container 100 in the positive direction of the Z axis from the terminal installation surface. In each lid 170, through holes 112a, 122a through which the shaft 340 passes are formed in the wall portion including each terminal installation surface (in the present embodiment, the first upper surface 112 and the second upper surface 122). The shaft 340 is crimped while passing through the wall portion including the terminal installation surface (in this embodiment, the first upper surface 112 and the second upper surface 122), the external gasket 400, the internal gasket 500, and the current collector 600, thereby connecting (joining) the terminal 300 and the current collector 600. During or after this connection, each lid 170 may be bent so as to match the shape of the end of the container body 160 in the X-axis direction.

[0058] The current collectors 600 are arranged one at each end of the electrode body 700 in the X-axis direction. The current collectors 600 are connected (joined) to the electrode body 700 and the terminal 300, and are conductive members (positive electrode current collector and negative electrode current collector) that electrically connect 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 is connected (joined) to a tab portion 720 of the electrode body 700 (described later) by welding, crimping, or the like, and the second joint portion 640 of the current collector 600 is connected (joined) to the terminal 300 by crimping, welding, or the like. The first joint portion 630 and the second joint portion 640 are each flat plate-shaped portions formed by bending a single metal plate. The material of the current collector 600 is not particularly limited, but 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.

[0059] The external gasket 400 is disposed between the lid 170 of the container 100 and the terminal 300, and is a member that insulates the lid 170 from the terminal 300 and seals the interior of the container 100. In this embodiment, the external gasket 400 is a plate-shaped, rectangular insulating member. The internal gasket 500 is disposed between the lid 170 and the current collector 600, and is a member that insulates the lid 170 from the current collector 600 and seals the interior of the container 100. In this embodiment, both the external gasket 400 and the internal gasket 500 are plate-shaped, rectangular insulating members. The material of the external gasket 400 and the internal gasket 500 may be an electrically insulating resin such as polypropylene (PP), polyethylene (PE), polystyrene (PS), ABS resin, or a composite material thereof.

[0060] The electrode body 700 is an electricity storage element (power generating element) formed by winding electrode plates. The electrode body 700 has a long, elongated cylindrical shape extending in the X-axis direction. Because the length of the electrode body 700 in the Y-axis direction is shorter than the lengths of the electrode body 700 in the X-axis direction and the Z-axis direction, the electrode body 700 can also be said to have a flat shape. The length of the electrode body 700 in the X-axis direction is 300 mm or more, specifically, approximately 500 mm to 1500 mm. The length of the electrode body 700 in the X-axis direction is longer than the length of the electrode body 700 in the Z-axis direction, and the length of the electrode body 700 in the X-axis direction is three times or more the length of the electrode body 700 in the Z-axis direction. The electrode body 700 includes a main body portion 710 and multiple tab portions 720 protruding from the main body portion 710. As described above, the tab portions 720 are connected (joined) to the current collector 600.

[0061] In this embodiment, the multiple tab portions 720 protrude one by one from both end faces in the X-axis direction of the main body portion 710. A positive electrode tab portion 721 is provided on the end face (one end face) of the main body portion 710 in the positive X-axis direction, and a negative electrode tab portion 722 is provided on the end face (the other end face) of the main body portion 710 in the negative X-axis direction.

[0062] Such an energy storage element 10 is manufactured by the following manufacturing method. First, the container body 160 is formed by extrusion molding, or by rolling a metal sheet and welding the ends in the Z-axis direction together. The container body 160 may be formed by welding together multiple segments divided in the XY plane. Next, the electrode assembly 700 is inserted into the container body 160. After insertion, the current collectors 600 are connected to the tab portions 720 of the positive and negative electrodes. Next, the external gasket 400, the internal gasket 500, the lid 170, and the terminals 300 are assembled to each current collector 600, and then the lids 170 are welded to both ends of the container body 160. After that, the electrolyte is injected into the container 100 through the injection port, and the injection port is sealed.

[0063] [Explanation of the configuration of the electrode assembly] Fig. 5 is a perspective view showing the configuration of an electrode assembly 700 according to an embodiment. Specifically, Fig. 5 shows a partially unfolded state of the winding of the electrode plates in the electrode assembly 700. As shown in Fig. 5, the electrode assembly 700 includes a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762.

[0064] The positive electrode plate 740 is an electrode plate in which a positive electrode active material layer 742 is disposed on both sides of a positive electrode current collector foil 741, which is a long strip of metal foil. Aluminum, 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 in which a negative electrode active material layer 752 is disposed on both sides of a negative electrode current collector foil 751, which is a long strip of metal foil. Copper, 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 used as long as it is capable of absorbing and releasing lithium ions.

[0065] As a 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.), polyanion compounds such as lithium titanate, LiMn ２ O ４ and LiMn １．５ Ni ０．５ O ４Spinel-type lithium manganese oxides such as α-NaFeO ２ LiMO having a type crystal structure ２ (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc.) can be used. Examples of the negative electrode active material include lithium metal, alloys capable of absorbing and releasing lithium, carbon materials (graphite, non-graphitizable carbon, easily graphitizable carbon, low-temperature fired carbon, amorphous carbon, etc.), and silicon oxides.

[0066] Here, the positive electrode active material is α-NaFeO ２ When the active material has a crystalline structure and contains Ni, it is preferable to set the ratio of the mass of Ni to the mass of the transition metal contained in the positive electrode active material to 50% or more in order to increase the energy density of the electrode body 700. The positive electrode active material layer contains optional components such as a positive electrode active material other than the lithium transition metal composite oxide, a conductive agent, a binder, a thickener, and a filler, as necessary.

[0067] Separators 761 and 762 are microporous sheets made of resin. Any known material can be used as the material for separators 761 and 762 as long as it does not impair the performance of energy storage element 10. Separators 761 and 762 may be made of a woven fabric or nonwoven fabric that is insoluble in organic solvents, a synthetic resin microporous film made of a polyolefin resin such as polyethylene, or the like.

[0068] The electrode assembly 700 is formed by winding a positive electrode plate 740, a negative electrode plate 750, and separators 761 and 762. The electrode assembly 700 is formed by stacking and winding the negative electrode plate 750, the separator 761, the positive electrode plate 740, and the separator 762 in this order. In this embodiment, the positive electrode plate 740, the negative electrode plate 750, and the separators 761 and 762 are wound around a winding axis L extending in the X-axis direction, thereby forming the wound electrode assembly 700. The winding axis L is an imaginary axis that serves as the central axis when winding the positive electrode plate 740, the negative electrode plate 750, and the separators 761 and 762. In this embodiment, the winding axis is a straight line that passes through the center of the electrode assembly 700 and is parallel to the X-axis direction.

[0069] A plurality of protruding pieces 743 protruding outward are arranged at intervals on the edge of the positive electrode plate 740 in the X-axis positive direction. Similarly, a plurality of protruding pieces 753 protruding outward are arranged at intervals on the edge of the negative electrode plate 750 in the X-axis negative direction. Each of the plurality of protruding pieces 743 is a portion where no positive electrode active material layer is disposed and the positive electrode current collector foil 741 is exposed (a portion where no positive electrode active material layer is formed). Each of the plurality of protruding pieces 753 is a portion where no negative electrode active material layer is disposed and the negative electrode current collector foil 751 is exposed (a portion where no negative electrode active material layer is formed). In FIG. 5 , the active material layer-free portions (a portion where no positive electrode active material layer is formed, a portion where no negative electrode active material layer is formed) are indicated by diagonal lines.

[0070] When the positive electrode plate 740, the negative electrode plate 750, and the separators 761, 762 are wound, the multiple protruding pieces 743 of the positive electrode plate 740 substantially overlap at the end face (one end face) of the main body portion 710 in the positive direction of the X axis, and the multiple protruding pieces 753 of the negative electrode plate 750 substantially overlap at the end face (the other end face) in the negative direction of the X axis. The portion of the positive electrode plate 740 where the multiple protruding pieces 743 overlap is the positive electrode tab portion 721. In other words, the positive electrode tab portion 721 is a portion where multiple pieces (protruding pieces 743) of the electrode plates (positive electrode plate 740 and negative electrode plate 750) of the same polarity are stacked. Hereinafter, the expressions "overlap" and "overlapping" are not limited to the strict meaning of "integrally stacked." The terms "overlap" and "overlapping" also include situations where the electrodes are stacked with variation (shift) in a direction perpendicular to the overlapping direction.

[0071] Similarly, the portion of the negative electrode plate 750 where the multiple protruding pieces 753 overlap is the negative electrode tab portion 722. In other words, the negative electrode tab portion 722 is a portion where the multiple pieces (protruding pieces 753) provided on the electrode plate of the same polarity (negative electrode plate 750) among the multiple electrode plates (positive electrode plate 740 and negative electrode plate 750) are stacked.

[0072] As described above, the electrode body 700 includes a main body portion 710 that constitutes the main 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 in the X-axis direction of the main body portion 710. In other words, the electrode body 700 includes a pair of tab portions that are composed of the positive electrode tab portion 721 and the negative electrode tab portion 722.

[0073] The main body portion 710 is an elongated cylindrical portion formed by winding together a portion of the positive electrode plate 740 where the positive electrode active material layer 742 is disposed (formed, coated), a portion of the negative electrode plate 750 where the negative electrode active material layer 752 is disposed (formed, coated), and separators 761 and 762. The region of the main body portion 710 where at least one of the positive electrode active material layer 742 and the negative electrode active material layer 752 is laminated is referred to as the active material layer formation portion. The outer surface of the main body portion 710 includes curved portions 711 at both ends in the Z-axis direction and flat portions 712 at both ends in the Y-axis direction. In other words, the outer surface of the main body portion 710 includes a pair of curved portions 711 and a pair of flat portions 712. Each flat portion 712 of the pair of flat portions 712 is located between the pair of curved portions 711 in the Z-axis direction, forming a flat shape overall. It can also be said that the pair of curved portions 711 are arranged at positions sandwiching each flat portion 712 in the Z-axis direction.

[0074] The curved portion 711 is a portion that extends in the X-axis direction and protrudes in a curved shape in the Z-axis direction. When viewed from the X-axis direction, the curved portion 711 is curved in a semicircular arc shape. The curved portion 711 located in the positive direction of the Z-axis faces the curved wall portion 141 of the container body 160 in the Z-axis direction, and the curved portion 711 located in the negative direction of the Z-axis faces the curved wall portion 151 of the container body 160 in the Z-axis direction. In other words, the curved portion 711 faces the curved wall portions 141 and 151 in the Z-axis direction.

[0075] The flat portion 712 is a flat portion that extends in the X-axis direction and is parallel to the XZ plane, connecting the ends of the pair of curved portions 711. The flat portion 712 is a surface that is perpendicular to the Y-axis direction. Each flat portion 712 is disposed opposite a corresponding flat wall portion 131 of the container body 160. In the portion of the electrode body 700 sandwiched between the flat portions 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 main stacking direction of the multiple electrode plates is defined as the Y-axis direction.

[0076] The curved shape of the curved portion 711 as viewed from the X-axis direction is not limited to a semicircular arc shape, but may be a shape like a part of an ellipse, 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 completely flat, but the outer surface may be slightly recessed or slightly bulged.

[0077] [Holding Unit] Fig. 6 is an explanatory diagram showing the holding unit 20, the case 2, and the energy storage device 10 according to the embodiment. Fig. 6 shows a cross-sectional view of only the case 2. As shown in Fig. 6, the holding unit 20 is composed of a plurality of holding members 21 arranged in the Y-axis direction.

[0078] The holding members 21 are arranged alternately with the energy storage elements 10 in the Y-axis direction and are members that hold the energy storage elements 10, providing insulation and / or heat between the energy storage elements 10 and between the energy storage elements 10 and other components. In this embodiment, the holding members 21 are arranged so as to directly face the flat wall portion 131 of the container 100 and at least a portion of the curved wall portion 141 of the container 100 and overlap the region of the electrode body 700 where the active material layer is formed (see FIGS. 2 and 4 ). The holding members 21 are insulating plate-like members that are arranged adjacent to the energy storage elements 10 in the positive or negative Y-axis direction of the energy storage elements 10 and that insulate the energy storage elements 10 from each other or from the case 2. The holding members 21 may be formed of an insulating material such as PC, PP, PE, PS, ABS resin, or a composite material thereof, or may be formed of a metal member with an insulating surface.

[0079] From the viewpoint of cooling performance, each holding member 21 may be made of a material with high thermal conductivity. Each holding member 21 may be made of an insulating material with higher thermal conductivity than polypropylene. Alternatively, each holding member 21 may be formed mainly of metal, the surface of which may be coated with an insulating material. Each holding member 21 may be made of a heat insulating material to avoid thermal influence with adjacent energy storage elements. Examples of heat insulating materials include mica and other insulating materials.

[0080] Of the intermediate spacer 210, the flat surface 211 and the curved surfaces 212 and 213, which face in the negative Y-axis direction, overlap with and are in contact with the surfaces, facing in the positive Y-axis direction, of the energy storage devices 10 adjacent to the intermediate spacer 210 in the negative Y-axis direction. Specifically, of the containers 100 of the energy storage devices 10 adjacent to the intermediate spacer 210 in the negative Y-axis direction, the outer surfaces of the flat wall portions 131, the curved wall portions 141, and the curved wall portions 151, which face in the positive Y-axis direction, are in surface contact with the flat surface 211 and the curved surfaces 212 and 213, which face in the negative Y-axis direction, of the intermediate spacer 210. In this embodiment, the curved surface 212 is in contact with the outer surface of the curved wall portion 141 up to the furthest position in the positive Z-axis direction (the apex of the outer surface of the curved wall portion 141); however, a portion of the outer surface of the curved wall portion 141 does not have to face or be in contact with the curved surface 212. Similarly, the curved surface 213 contacts the outer surface of the curved wall portion 151 up to the position furthest in the negative Z-axis direction (the apex of the outer surface of the curved wall portion 151), but a portion of the outer surface of the curved wall portion 151 does not have to face or contact the curved surface 212.

[0081] Similarly, the flat surface 211 and the curved surfaces 212 and 213 of the intermediate spacer 210, which face in the positive direction of the Y axis, overlap with the surfaces of the energy storage devices 10 adjacent to the intermediate spacer 210 in the positive direction of the Y axis, which face in the negative direction of the Y axis. Specifically, of the containers 100 of the energy storage devices 10 adjacent to the intermediate spacer 210 in the positive direction of the Y axis, the outer surfaces of the flat wall portions 131, the curved wall portions 141, and the curved wall portions 151, which face in the negative direction of the Y axis, are in surface contact with the flat surface 211 and the curved surfaces 212 and 213 of the intermediate spacer 210, which face in the positive direction of the Y axis. In this embodiment, the curved surface 212 is in contact with the outer surface of the curved wall portion 141 up to the furthest position in the positive direction of the Z axis (the apex of the outer surface of the curved wall portion 141). However, it is not necessary for a portion of the outer surface of the curved wall portion 141 to face or be in contact with the curved surface 212. Similarly, the curved surface 213 contacts the outer surface of the curved wall portion 151 up to the position furthest in the negative Z-axis direction (the apex of the outer surface of the curved wall portion 151), but a portion of the outer surface of the curved wall portion 151 does not have to face or contact the curved surface 212.

[0082] In the end spacer 220 arranged in the negative Y-axis direction, the end face in the negative Y-axis direction is formed flat along the inner surface of the case body 30, and the end face in the positive Y-axis direction is formed in a shape recessed in the negative Y-axis direction along the outer shape of the adjacent energy storage element 10. The flat surface 221 and curved surfaces 222, 223 of this end spacer 220 overlap and come into contact with the surface of the adjacent energy storage element 10 facing in the negative Y-axis direction in the positive Y-axis direction.

[0083] Similarly, in the end spacer 220 arranged in the positive direction of the Y axis, the end face in the positive direction of the Y axis is formed flat along the inner surface of the case body 30, and the end face in the negative direction of the Y axis is formed in a shape recessed in the positive direction of the Y axis along the outer shape of the adjacent energy storage element 10. The flat surface 221 and curved surfaces 222, 223 of this end spacer 220 overlap and come into contact with the surface of the adjacent energy storage element 10 in the negative direction of the Y axis that faces the positive direction of the Y axis.

[0084] In this embodiment, the inner surface of the flat wall portion 131 of the container 100 contacts the flat portion 712 of the electrode assembly 700, and the inner surface of the curved wall portion 141 contacts the curved portion 711 of the electrode assembly 700, thereby suppressing and limiting expansion of the curved portion 711. This makes it possible to suppress damage to the curved portion 711 and to the boundary between the curved portion 711 and the flat portion 712.

[0085] 6, in particular, the holding unit 20 holding each energy storage element 10 presses each energy storage element 10 in the Y-axis direction and the Z-axis direction. Here, at the beginning of life (BOL) of the energy storage element 10, the reaction force in the Y-axis direction and the reaction force in the Z-axis direction applied by the holding unit 20 to the energy storage element 10 are 1 kN or more and 5 kN or less.

[0086] In the Y-axis direction and Z-axis direction, which are the compression directions, the thickness of the end spacer 220 and the thickness of the intermediate spacer 210 are thicker than the thickness of the container 100. Furthermore, the strength of the holding unit 20 is greater than the strength of the container 100. The holding unit 20 has sufficient strength to compress the electrode assembly 700, and the inner surface of the holding unit 20 includes curved surfaces 212, 222 that face most of the curved wall portion 141 of the container 100, and a flat surface 221 that faces most of the flat wall portion 131 of the container 100. Because the container 100 is directly interposed between both the holding unit 20 and the electrode assembly 700, when the holding unit 20 compresses (compresses) the outer surface of the container 100, the compression from the holding unit 20 is transmitted to the electrode assembly 700 via the container 100. This allows a compressive force that exceeds the strength of the container 100 to be applied to the electrode assembly 700, and deformation of the container 100 due to expansion of the electrode assembly 700 can be suppressed. That is, it is possible to prevent the expansion of the electrode body 700 from progressing beyond the dimensions of the container 100. As a result, it is possible to suppress the tension generated at the boundary between the flat portion 712 and the curved portion 711.

[0087] In particular, because the curved portion 711 of the electrode body 700 is in contact with the inner surface of the curved wall portion 141, stress is applied to the curved portion 711 from the curved wall portion 141, and the expansion of the curved portion 711 can be more reliably suppressed by the curved wall portion 141. Since there is no room for the curved portion 711 to expand within the container 100, dimensional changes in the electrode body 700 can be limited.

[0088] Furthermore, because the outer surface of the curved wall portion 141 is in surface contact with the curved surfaces 212, 222 of the holding unit 20, stress is applied to the curved wall portion 141 from the curved surfaces 212, 222. Therefore, even if the curved wall portion 141 attempts to expand due to the electrode body 700, the expansion can be more reliably suppressed by the curved surfaces 212, 222. The curved surfaces 212, 222 of the holding unit 20 can eliminate room for expansion of the curved wall portion 141 of the container 100, thereby limiting dimensional changes in the container 100.

[0089] Here, the BOL of the energy storage device 10 includes the time of shipment or immediately after manufacture. Immediately after manufacture also includes the period when the number of charge / discharge cycles since the energy storage device 10 was first charged after manufacture falls within a predetermined number. The predetermined number is the number of times that the main body 710 of the electrode body 700 expands and the outer surface of the main body 710 can entirely contact the inner surface of the container 100. The predetermined number is preferably 10 times, more preferably 5 times, and even more preferably 3 times.

[0090] After being housed in the case 2, the holding unit 20 holding each of the energy storage elements 10 is compressed in the Y-axis and Z-axis directions by the case 2. At this time, as shown in Fig. 6 , the outer surface of the holding unit 20 and the inner surface of the case 2 are in surface contact in the Y-axis and Z-axis directions, so that each of the energy storage elements 10 is subjected to pressure (restraining force) from the holding unit 20 as well as pressure (restraining force) from the case 2.

[0091] Whether or not the energy storage elements 10 held in the holding unit 20 are compressed by the holding unit 20 can be determined by detecting deformation of the energy storage elements 10 when the holding unit 20 and each energy storage element 10 are disassembled. Specifically, the dimensions of the energy storage elements 10 before disassembly and the dimensions of the energy storage elements 10 after disassembly are measured, and if the dimensions of the energy storage elements 10 after disassembly are larger than the dimensions of the energy storage elements 10 before disassembly, it can be determined that the energy storage elements 10 were compressed before disassembly. The swelling of the energy storage elements 10 may also be determined by shape changes before and after release of compression by CT imaging, or by shape changes due to whether the energy storage elements 10 fit into the holding unit 20 after release of compression.

[0092] [Explanation of Effects] As described above, according to the energy storage device 10 according to the embodiment of the present invention, the container 100 includes the curved wall portion 141 that faces the curved portion 711 of the electrode body 700, and the inner surface of the curved wall portion 141 has a curved shape that follows the curved portion 711 of the electrode body 700. This makes it possible to make the space created between the curved portion 711 of the electrode body 700 and the curved wall portion 141 of the container 100 smaller than the space created between the curved portion of the electrode body and the inner surface of the container in the case of a rectangular container, thereby preventing a situation in which the expansion of the curved portion 711 of the electrode body 700 is more likely to proceed relative to the expansion of the flat portion 712 of the electrode body 700. Furthermore, the inner surface of the holding unit 20 is provided with curved surfaces 212, 222 that follow the outer surface of the curved wall portion 141 of the container 100, so that when the container 100 is pressed by the holding unit 20, the electrode body 700 is compressed. This allows the pressure from the holding unit 20 to be transmitted to the electrode body 700 via the container 100, making it possible to apply a pressure to the electrode body 700 that exceeds the strength of the container 100 and to suppress deformation of the container 100 due to expansion of the electrode body 700. As a result, the tension generated at the boundary between the flat portion 712 and the curved portion 711 can be suppressed, and damage to the electrode body 700 can be suppressed.

[0093] The inner surface of the curved wall portion 141 of the container 100 presses against the curved portion 711 of the electrode body 700, and the inner surface of the flat wall portion 131 of the container 100 presses against the flat portion 712 of the electrode body 700, so that both the curved portion 711 and the flat portion 712 of the electrode body 700 are compressed, which more reliably prevents the curved portion 711 of the electrode body 700 from expanding more easily than the flat portion 712 of the electrode body 700. As a result, the tension generated at the boundary between the flat portion 712 and the curved portion 711 can be further suppressed, and damage to the electrode body 700 can be further suppressed.

[0094] It is conceivable that immediately after manufacture, the outer surface of the flat portion 712 of the electrode body 700 is not in contact with the inner surface of the flat wall portion 131 of the container 100, or the outer surface of the curved portion 711 of the electrode body 700 is not in contact with the inner surface of the curved wall portion 141 of the container 100. Even in these cases, if the energy storage element 10 is used after sale or the like and the electrode body 700 expands, so that the flat wall portion 131 of the container 100 presses against the flat portion 712 of the electrode body 700 and the curved wall portion 141 of the container 100 presses against the curved portion 711 of the electrode body 700, this is included in the configuration of the present application.

[0095] With the flat portion 712 of the electrode body 700 compressed by the flat wall portion 131 of the container 100 and the curved portion 711 of the electrode body 700 compressed by the curved wall portion 141 of the container 100, the curved surfaces 212, 213 of the holding unit 20 press against the outer surface of the curved wall portion 141 of the container 100. That is, the pressure from the holding unit 20 is transmitted to the curved portion 711 of the electrode body 700 via the curved surfaces 212, 213 of the holding unit 20 and the curved wall portion 141 of the container 100. This allows a large compressive force to be applied to the curved portion 711 of the electrode body 700 that exceeds the strength of the curved wall portion 141 of the container 1000, and deformation of the container 100 due to expansion of the curved portion 711 of the electrode body 700 can also be suppressed.

[0096] Because the inner surface of the holding unit 20 presses against the outer surface of the flat wall portion 131 of the container 100, expansion of the flat wall portion 131 of the container 100 can be more reliably suppressed. Furthermore, the holding unit 20 presses against the flat portion 712 of the electrode assembly 700 via the flat wall portion 131 of the container 100, and presses against the curved portion 711 of the electrode assembly 700 via the curved wall portion 141 of the container 100, thereby suppressing deformation of the entire electrode assembly 700. This more reliably suppresses defects that lead to a decrease in capacity, such as distortion of the electrode assembly 700, which occur at an earlier stage than damage to the electrode assembly 700.

[0097] Each holding member 21 integrally comprises flat surfaces 211, 221 that compress the flat wall portion 131 and curved surfaces 212, 222 that compress the curved wall portion 141, so that the holding member 21 can suppress both the expansion of the flat wall portion 131 and the expansion of the curved wall portion 141 in the container 100, and the electrode body 700 can be compressed with a simple configuration.

[0098] The outer surface of the holding member 21 is pressed by the case 2 (external member), so that the curved surfaces 212, 222 of the holding member 21 press against the outer surface of the curved wall portion 141 of the container 100. At this time, the curved surfaces 212, 222 of the inner surface of the holding member 21 themselves press against the curved wall portion 141 of the container 100, and a large compressive force consisting of both the compressive force from the case 2 and the compressive force from the holding member 21 is applied to the curved wall portion 141 of the container 100. Furthermore, deformation of the container 100 due to expansion of the curved portion 711 of the electrode body 700 can be more reliably suppressed. Because the electrode body 700 is also pressed against the container 100, expansion of the electrode body 700 can be more effectively suppressed from progressing beyond the internal dimensions of the container 100. In addition, when the curved portion 711 of the electrode body 700 is compressed by the curved wall portion 141 of the container 100 and the flat portion 712 of the electrode body 700 is compressed by the flat wall portion 131 of the container 100, expansion is suppressed in both the curved portion 711 and the flat portion 712 of the electrode body 700, preventing the tensile stress between the two from exceeding its current level, further preventing foil tearing of the electrode body 700.

[0099] Here, the flat wall portion 131 of the container 100 is preferably directly interposed between the flat surface 211 of the holding unit 20 and the flat portion 712 of the electrode assembly 700 and is in surface contact with them. The curved wall portion 141 of the container 100 is preferably directly interposed between the curved surfaces 212, 222 of the holding unit 20 and the curved portion 711 of the electrode assembly 700 and is in surface contact with them. This allows the compressive force from the holding unit 20 to be transmitted to the electrode assembly 700 via the walls of the container 100 (the flat wall portion 131 and the curved wall portion 141), thereby compressing the electrode assembly 700.

[0100] [Comparison between the Present Invention and the Prior Art] FIG. 7 is a cross-sectional view of a conventional energy storage element 10y (Comparative Example 1) cut along a plane parallel to the YZ plane. Specifically, the energy storage element 10y of Comparative Example 1 is an energy storage element 10y in which a flat, wound electrode assembly 700y is housed in a rectangular container 100y. FIG. 7 shows an example of the internal structure of the energy storage element 10y in which the electrode assembly flat portion 712y contacts the inner surface of the container 100y when the electrode assembly expands. In the prior art structure, depending on the design, even if the electrode assembly flat portion 712y contacts the inner surface of the container 100y, the electrode assembly curved portion 711y may not contact the inner surface of the container 100y. In such a case, as the expansion of the electrode assembly 700y progresses, the expansion in the region of the electrode assembly flat portion 712y initially progresses mainly in the thickness direction of the electrode plate (Y-axis direction), but gradually extends to the longitudinal direction of the electrode plate (Z-axis direction). At the end of the life of the energy storage element 10y, the expansion of the electrode body 700y in the thickness direction (Y-axis direction) is compressed by the inner surface of the container 100y, increasing the frictional force between the inner surface of the energy storage element 10y and the outer surface of the electrode body flat portion 712y, preventing the electrode plate from extending in the longitudinal direction (Z-axis direction). Meanwhile, in the electrode body curved portion 711y, even at the end of the life of the energy storage element 10y, excess space remains between the electrode body 700y and the inner surface of the container 100y, and the electrode plate continues to extend in the longitudinal direction (Y-axis direction, Z-axis direction). Therefore, strong tensile stress is generated in the electrode plate in the boundary region between the electrode body flat portion 712y and the electrode body curved portion 711y of the electrode body 700y, which, in the worst case, may lead to the electrode plate breaking.

[0101] FIG. 8 is a cross-sectional view of a conventional energy storage element 10z (Comparative Example 2), which is a partial modification of the design of the energy storage element of Comparative Example 1, cut along a plane parallel to the YZ plane. The energy storage element 10z of Comparative Example 2 shown in FIG. 8 differs from the energy storage element 10y of Comparative Example 1 in that, when the electrode body 700z expands, the upper portion (the end in the positive Z-axis direction) of the electrode body curved portion 711z as well as the electrode body flat portion 712z contact the inner surface of the container 100z. The other configurations of the energy storage element 10z of Comparative Example 2 are the same as those of the energy storage element 10y of Comparative Example 1. In the case of the energy storage element 10y of Comparative Example 1, when the expansion of the electrode body 700y progresses further than the state shown in FIG. 7, the electrode body flat portion 712y of the electrode body 700y is pressed against the inner surface of the container 100y, preventing the electrode plates from extending in the longitudinal direction (Z-axis direction). On the other hand, because excess space remained in the curved portion 711y of the electrode body, the electrode plate continued to extend in the longitudinal direction (Y-axis direction, Z-axis direction). In contrast, in the energy storage element 10z of Comparative Example 2, the upper portion of the curved portion 711z of the electrode body (the end portion of the curved portion in the Z-axis direction) was also pressed against the inner surface of the container 100z, but excess space remained between the curved portion 711z of the electrode body and the inner surface of the container 100z except for the upper portion of the curved portion 711z. Therefore, deformation of the electrode body 700z may cause unevenness in the inter-electrode distance, potentially resulting in lithium electrodeposition. This may result in deterioration of battery capacity.

[0102] FIG. 9 shows an example of an energy storage device 1 in which the curved surface 222 of the holding unit 20 of the present invention is structured to press against the outer surface of the curved wall portion 141 of the container 100 of the energy storage element 10. An electrode assembly 700 having a curved portion 711 and a flat portion 712 is housed in a container 100 arranged so as to fit along the outer surface of the electrode assembly 700, and a holding unit 20 is further arranged so as to fit along the outer surface of the container 100. In FIG. 9, the holding unit 20 is formed of two holding members, an intermediate spacer 210 and an end spacer 220, which press against the energy storage element 10. In this way, the holding unit 20 is structured to press against the container 100 of the energy storage element 10 and further against the electrode assembly 700. In the present invention, when the expansion of the electrode assembly 700 progresses, the entire container 100 and the entire holding unit 20 uniformly press against the expansion of the electrode assembly 700. Therefore, it is possible to prevent the occurrence of tensile stress between the curved portion 711 and the flat portion 712, which would cause deformation of the electrode body or breakage of the electrode, as described above.

[0103] [Explanation of Modifications] Modifications of the above-described embodiment will be described below. In the following description, the same parts as those in the above-described embodiment or other modifications will be denoted by the same reference numerals, and the description thereof may be omitted.

[0104] (Modification 1) A description will be given of a holding unit 20A according to Modification 1. Fig. 10 is an explanatory diagram showing a holding unit 20A according to Modification 1, a case 2, and each energy storage element 10.

[0105] 10, the holding unit 20A includes a plurality of first holding members 23 and a plurality of second holding members 24 for each energy storage device 10. The first holding members 23 and the second holding members 24 are separate members.

[0106] Of the multiple first holding members 23, a pair of first holding members 23 in the Z-axis direction are positioned to sandwich the container 100 of the energy storage device 10 in the Z-axis direction. The first holding members 23 have an outer shape based on a rectangular parallelepiped shape elongated in the X-axis direction. The lower surface of the first holding member 23 located in the positive Z-axis direction (the surface facing the negative Z-axis direction) is recessed in the positive Z-axis direction along the outer shape of the energy storage device 10. This recessed portion is most recessed at the center of the lower surface of the first holding member 23 in the Y-axis direction and is U-shaped when viewed from the X-axis direction. Furthermore, the recessed portion has a curved shape that follows the outer surface of the curved wall portion 141. In the first modified example, since the thickness of the curved wall portion 141 is constant, the recessed portion also has a curved shape that follows the inner surface of the curved wall portion 141. The recessed portion includes a curved surface 231, which comes into surface contact with the outer surface of the curved wall portion 141 of the energy storage device 10.

[0107] Similarly, the upper surface of the first holding member 23 located in the negative Z-axis direction (the surface facing the positive Z-axis direction) has a recessed shape in the negative Z-axis direction that follows the outer shape of the adjacent energy storage element 10. This recessed portion is U-shaped when viewed from the X-axis direction. The recessed portion has a curved shape that follows the outer surface of the curved wall portion 151. In the form of variant example 1, since the thickness of the curved wall portion 151 is constant, the recessed portion also has a curved shape that follows the inner surface of the curved wall portion 151. The recessed portion is a curved surface 231 that comes into surface contact with the outer surface of the curved wall portion 151 of the energy storage element 10.

[0108] The multiple second holding members 24 are arranged alternately with the energy storage devices 10 in the Y-axis direction. The second holding members 24 are elongated in the X-axis direction, parallel to the XZ plane, and have a flat plate shape that is flat in the Y-axis direction. The surface of the second holding member 24 facing the positive Z-axis is in contact with the lower surface (the surface facing the negative Z-axis) of the first holding member 23, which is located further in the positive Z-axis direction than the second holding member 24. The surface of the second holding member 24 facing the negative Z-axis is in contact with the upper surface (the surface facing the positive Z-axis) of the first holding member 23, which is located further in the negative Z-axis direction than the second holding member 24. The surface of each second holding member 24 facing the energy storage device 10 in the Y-axis direction is a flat surface 241 that contacts the outer surface of the flat wall portion 131 of the energy storage device 10.

[0109] As described above, because the first holding member 23 and the second holding member 24 are separate, the first holding member 23 and the second holding member 24 do not need to be installed simultaneously, facilitating the manufacture of the energy storage device 1. Furthermore, the compressive force applied from the first holding member 23 in the opposing direction of the pair of curved portions 711 of the electrode assembly 700 and the compressive force applied from the second holding member 24 in the direction perpendicular to the flat portion 712 of the electrode assembly 700 can be individually adjusted. Even if the size of the energy storage element 10 changes due to a design change or model change, as long as the shape of the container 100 is partially the same, it is possible to reuse either the first holding member 23 or the second holding member 24, thereby reducing manufacturing costs. (Variation 2) A holding unit 20B according to Variation 1 will be described. FIG. 11 is an explanatory diagram showing the holding unit 20B, the case 2, and each energy storage element 10 according to Variation 1.

[0110] 11 , the holding unit 20B includes a pair of first holding members 25 and a plurality of second holding members 26. The first holding members 25 and the second holding members 26 are separate bodies, i.e., separate members. In this modification, the first holding member 25 includes the refrigerant passage 22 through which a refrigerant flows, but the refrigerant passage 22 may also be a passage through which a medium for adjusting the temperature of the energy storage element flows. In other words, the refrigerant passage 22 may also be a passage through which a medium for keeping warm or heating the energy storage element flows.

[0111] The multiple second holding members 26 are arranged alternately with the energy storage elements 10 in the Y-axis direction. Each second holding member 26 has a flat plate shape that is elongated in the X-axis direction, parallel to the XZ plane, and flat in the Y-axis direction. Each surface of each second holding member 26 facing the Y-axis direction is a planar flat surface 261 that faces the outer surface of the flat wall portion 131 of the energy storage element 10 and is in contact with the outer surface of the flat wall portion 131 of the energy storage element 10.

[0112] The pair of first holding members 25 are positioned in the Z-axis direction, sandwiching the container 100 of the energy storage device 10 and the multiple second holding members 26. The first holding member 25 has an outer shape based on a rectangular parallelepiped that is long in the X-axis direction and flat in the Z-axis direction. Of the surfaces of the first holding members 25 facing the negative Z-axis direction, the portions facing each energy storage device 10 in the Z-axis direction are recessed in the positive Z-axis direction along the outer shape of the energy storage device 10. The number of recessed portions is the same as the number of installed energy storage devices 10. Each recessed portion is U-shaped when viewed from the X-axis direction. The recessed portion has a curved shape that follows the outer surface of the curved wall portion 141. In this modified example, since the thickness of the curved wall portion 141 is constant, the recessed portion also has a curved shape that follows the inner surface of the curved wall portion 141. Each recessed portion is a curved surface 251 that comes into surface contact with the outer surface of the curved wall portion 141 of the energy storage device 10.

[0113] Similarly, of the surface of the first holding member 25 located in the negative Z-axis direction and facing the positive Z-axis direction, the portion facing each energy storage device 10 in the Z-axis direction is recessed in the negative Z-axis direction along the outer shape of the energy storage device 10. The number of recessed portions is the same as the number of installed energy storage devices 10. Each recessed portion is U-shaped when viewed from the X-axis direction. The recessed portion has a curved shape that follows the outer surface of the curved wall portion 141. In this modified example, since the thickness of the curved wall portion 141 is constant, the recessed portion also has a curved shape that follows the inner surface of the curved wall portion 141. Each recessed portion is a curved surface 251 that comes into surface contact with the outer surface of the curved wall portion 141 of the energy storage device 10. In this manner, each first holding member 25 integrally includes multiple curved surfaces 251.

[0114] Of the multiple energy storage elements 10 held by such a holding unit 20B, one energy storage element 10 is an example of a first energy storage element, and the other energy storage element 10 adjacent to the first energy storage element in the Y-axis direction is an example of a second energy storage element. The electrode body 700 provided in the first energy storage element is an example of a first electrode body. The flat portion 712 and the curved portion 711 provided in the first electrode body are examples of a first flat portion and a first curved portion. The container 100 provided in the first energy storage element is an example of a first container. The flat wall portion 131 and the curved wall portion 141 provided in the first container are examples of a first flat wall portion and a first curved wall portion. The electrode body 700 provided in the second energy storage element is an example of a second electrode body. The flat portion 712 and the curved portion 711 provided in the second electrode body are examples of a second flat portion and a second curved portion. The container 100 provided in the second energy storage element is an example of a second container. The flat wall portion 131 and the curved wall portion 141 of the second container are examples of a second flat wall portion and a second curved wall portion. Of the multiple curved surfaces 251 of each first holding member 25, the curved surface 251 facing the curved wall portion 141 of the first energy storage element and the curved surface 251 facing the curved wall portion 151 of the first energy storage element are examples of first curved surfaces, and the curved surface 251 facing the curved wall portion 141 of the second energy storage element and the curved surface 251 facing the curved wall portion 151 of the second energy storage element are examples of second curved surfaces.

[0115] As described above, the multiple curved surfaces 251 (first curved surface, second curved surface) of the first holding member 25 face the respective curved wall portions 141, 151 of the multiple energy storage elements 10 (first energy storage element, second energy storage element), and therefore the multiple curved surfaces 251 of the first holding member 25 can collectively compress the multiple curved wall portions 141, 1510. Furthermore, since fewer first holding members 25 are required than when one first holding member is disposed for one curved wall portion, assembly of the energy storage device 1 is easier.

[0116] Because the first holding member 25 is made of a foamed resin, during manufacturing, the curved surface 251 of the first holding member 25 can be easily formed to conform to the shape of the curved wall portions 141, 151 of the container 100. This reduces the number of parts required for the first holding member 25, making manufacturing easier. The first holding member 25 is made of a material that has sufficient strength even though it is made of a foamed resin, and has a sufficient elastic range to suppress expansion of the electrode body 700. An example of such a foamed resin is urethane glass resin. Note that portions of the holding unit 20B other than the first holding member 25 may be made of a foamed resin.

[0117] (Variation 3) An energy storage device 10c according to Variation 3 will be described. FIG. 12 is a perspective view showing the appearance of the energy storage device 10c according to Variation 3. As shown in FIG. 12, in the container 100c of the energy storage device 10c, a gas exhaust valve 800c is arranged on a surface parallel to the YZ plane in each second recess 102c. In this case, no gas exhaust valve is provided on a surface parallel to the XY plane in each second recess 102c. The gas exhaust valve 800c may be provided in only one second recess 102c. A gas exhaust valve may be provided in at least one first recess.

[0118] (Modification 4) An energy storage device 10d according to Modification 4 will be described. Fig. 13 is a perspective view showing the appearance of the energy storage device 10d according to Modification 4. As shown in Fig. 13, the container 100d of the energy storage device 10d has a pair of first recesses 101d located in the positive direction of the Z axis, but does not have a recess located in the negative direction of the Z axis of the container 100d. At least one of the first recesses 101d in the container 100d has a gas release valve 800d located on a surface parallel to the YZ plane.

[0119] (Variation 5) An energy storage device 10e according to Variation 5 will be described. FIG. 14 is a perspective view showing the appearance of the energy storage device 10e according to Variation 5. As shown in FIG. 14, the container 100e of the energy storage device 10e does not have a recess, is elongated in the X-axis direction, and has an overall oval cylindrical shape. Each terminal 300e and each external gasket 400e is disposed on the outer surface of a curved wall portion 141e of the container 100e, and each terminal 300e protrudes in the positive direction of the Z-axis from the outer surface of the curved wall portion 141e of the container 100e. A gas release valve 800e is provided on at least one of a pair of end faces of the container 100e in the X-axis direction.

[0120] As described above, since the terminals 300e protrude from the outer surface of the curved wall portion 141e of the container 100e, the internal space of the container 100e is not easily consumed. This allows the electrode assembly 700 to be made as large as possible, thereby increasing the energy density.

[0121] Furthermore, since each terminal 300e protrudes from the outer surface of the curved wall portion 141e of the container 100e, the connection work to the terminals 300e of other energy storage elements 10e can be easily performed.

[0122] In the configuration of energy storage element 10e according to modification 5, terminal 300e is not provided on the surface of container 100e in the direction of the winding axis (X-axis), and therefore, when energy storage element 10e is housed in case 2, it is possible to simplify and downsize protective members and the like that are arranged at positions closer to the end of energy storage element 10e in the direction of the winding axis. Furthermore, this allows for greater freedom in designing case 2 compared to an energy storage element that has terminals on the surface in the direction of the winding axis.

[0123] At a position in the positive direction of the Z axis from terminal 300, there is a space sandwiched between the holding unit 20 and the wall of case 2, and by placing a bus bar or the like in this space, the energy density of the entire storage device can be improved.

[0124] (Variation 6) An energy storage device 10f according to Variation 6 will be described. FIG. 15 is a perspective view showing the appearance of the energy storage device 10f according to Variation 6. As shown in FIG. 15, in the energy storage device 10f, the terminals 300 and the external gasket (not shown) are arranged on a surface parallel to the XY plane in each second recess 102f. In other words, one energy storage device 10f has four terminals 300. The gas release valve 800f is arranged on a surface parallel to the YZ plane in the second recess 102f, but may also be arranged on a surface parallel to the YZ plane in the first recess 101f.

[0125] (Variation 7) An energy storage element 10g according to Variation 7 will be described. FIG. 16 is a perspective view showing the appearance of an energy storage element 10g according to Variation 7. In the energy storage element 10e according to Variation 5, the terminals 300e and external gaskets (not shown) are arranged at both ends of the curved wall portion 141e in the X-axis direction. However, in the energy storage element 10g according to Variation 5, the terminals 300g and external gaskets 400g are arranged at both ends of the curved wall portion 141g in the X-axis direction and at both ends of the curved wall portion 151g in the X-axis direction. In other words, one energy storage element 10g has four terminals 300. (Other Variations)

[0126] Although the energy storage element according to the embodiment of the present invention (including its modified examples, the same applies hereinafter) has been described above, the present invention is not limited to the above-described embodiment. The embodiment disclosed here is an example in all respects, and the scope of the present invention includes all modifications within the meaning and scope of the claims.

[0127] Although not illustrated in the above embodiment, any configuration is acceptable as long as the compressive force from the curved surface of the holding unit is transmitted to the curved wall of the container. The present invention also includes a configuration in which the curved shape of the outer surface of the curved wall of the container is replaced with a substantially circular polyhedron, and a configuration in which the curved shape of the curved surface of the holding unit is replaced with a polyhedron. At least one of the outer surface of the curved wall of the container and the curved surface of the holding unit may have a curved shape with a different curvature than the inner surface of the curved wall, and / or a shape with one or more corners and / or one or more flat surfaces. For example, at least one of the outer surface of the curved wall of the container and the curved surface of the holding unit may be a polyhedron.

[0128] Although not illustrated in the above embodiment, portions of the holding unit other than the first holding members 23 and 25 may be formed of foamed resin. Various methods for forming the holding unit using foamed resin are conceivable. The holding unit may be formed by placing the energy storage element in the energy storage device and then filling and solidifying foamed resin. Alternatively, pre-molded components constituting the holding unit may be assembled together with the energy storage element, etc. The holding unit may be composed of a combination of a portion filled as foamed resin in the energy storage device and then solidified, and a portion pre-molded before assembling the energy storage device. In this case, the steps of filling a portion of the holding unit as foamed resin in the energy storage device and solidifying it, and the step of assembling a portion of the pre-molded holding unit in the energy storage device may be performed in any order, and are not particularly limited. For example, the energy storage element and a first holding member (part of the holding unit) facing the curved wall portion of the energy storage element may be positioned and arranged in the energy storage device, and then foamed resin may be filled to form a second holding member (part of the holding unit) facing the flat wall portion of the energy storage element. In this example, a first holding member (part of the holding unit) that has been molded in advance and has a fixed shape is placed inside the energy storage device together with the energy storage element. The material of the first holding member (part of the holding unit) that is molded in advance before assembling the energy storage device may be a foamed resin, or a material different from the foamed resin. Alternatively, the energy storage element may be positioned and then the foamed resin may be filled and solidified once or multiple times to form the holding unit. Each component of the holding unit that has been molded in advance and has a fixed shape may be assembled together with the energy storage element.

[0129] In the above embodiment, the energy storage device 1 in which a plurality of energy storage elements 10 are housed in the case 2 is exemplified, but any energy storage device may be used as long as one or more energy storage elements are housed in the case.

[0130] In the above embodiment, the case where the external member is a box-shaped case 2 is exemplified. The external member may be formed by aluminum die-casting. Furthermore, the external member may be a component constituting a moving body such as an automobile. Examples of the moving body itself include a skeletal structure of the moving body, a bogie, and a chassis.

[0131] In the above embodiment, the pack-type energy storage device 1 in which the energy storage elements 10 and the holding unit 20 are housed in the case 2 has been exemplified, but a module-type energy storage device may also be used.

[0132] Any combination of the components included in the above-described embodiments and their modifications is also included within the scope of the present invention.

[0133] The present invention can be applied to an electric storage element such as a lithium ion secondary battery and an electric storage device including the same.

[0134] REFERENCE SIGNS LIST 1 Energy storage device 2 Case (external member) 10, 10c, 10d, 10e, 10f, 10g Energy storage element 20, 20A, 20B Holding unit 21 Holding member 22 Coolant path 23, 25 First holding member 24, 26 Second holding member 30 Case body 31 Opening 32 Bottom wall 33 Side wall 37 Exhaust port 40 Case lid 50 Exhaust member 51 First plate portion 52 Second plate portion 53 Ventilation hole 100, 100e Container 101 First recess (notch) 102, 102c, 102f Second recess (notch) 110 First side surface portion 112a Through hole 120 Second side surface portion 122a Through hole 130 Long side surface 131 Flat wall portion 140 Top surface 141, 141e, 151, 151g Curved wall portion 150 Bottom surface 160 Container body 170 Lid body 210 Intermediate spacer (holding member) 211, 221, 241, 261 Flat surface 212, 213, 222, 223, 231, 251 Curved surface 220 End spacer (holding member) 300, 300e Terminal 400 External gasket 700 Electrode body 710 Main body portion 711 Curved portion 712 Flat portion 720 Tab portion 721 Positive electrode tab portion 722 Negative electrode tab portion 740 Positive electrode plate 741 Positive electrode current collector foil 742 Positive electrode active material layer 743, 753 Protruding piece 750 Negative electrode plate 751 Negative electrode current collector foil 752: Negative electrode active material layer 761, 762: Separators 800, 800c, 800d, 800e: Gas release valve L: Winding axis L1: Range serving as a reference for the outer shape of the container 100 (shown by a two-dot chain line) S1, S2: Space

Claims

1. A storage device comprising: an energy storage element; and a holding unit arranged outward of the energy storage element and holding the energy storage element, wherein the energy storage element comprises: an electrode body having an electrode plate wound thereon; and a container accommodating the electrode body, wherein the electrode body has a flat shape having a pair of opposing flat portions and a pair of opposing curved portions, and the container comprises: a flat wall portion facing the flat portions of the electrode body; and a curved wall portion facing the curved portions of the electrode body, wherein the inner surface of the flat wall portion has a flat shape that follows the flat portions, and the inner surface of the curved wall portion has a curved shape that follows the curved portions, and the inner surface of the holding unit comprises: a flat surface that is a flat shape that follows the outer surface of the flat wall portion of the container; and a curved surface that is a curved shape that follows the outer surface of the curved wall portion of the container, wherein the inner surface of the flat wall portion of the container presses against the flat portions of the electrode body, and the inner surface of the curved wall portion of the container presses against the curved portions of the electrode body, The flat surface of the holding unit presses against the outer surface of the flat wall portion of the container, and the curved surface of the holding unit presses against the outer surface of the curved wall portion of the container.

2. The energy storage device according to claim 1, further comprising an external member or case arranged outward from the holding unit, the external member or case fixing or housing the holding unit, and the outer surface of the holding unit being pressed against the external member or case, such that the curved surface of the holding unit presses against the outer surface of the curved wall portion of the container of the energy storage element, and the flat surface of the holding unit presses against the outer surface of the flat wall portion of the container of the energy storage element.

3. The energy storage device of claim 2, wherein the holding unit comprises a plurality of holding members arranged in a direction in which the flat portion of the electrode body and the flat wall portion of the container face each other, and the inner surface of the holding member comprises the flat surface that presses against the outer surface of the flat wall portion of the container and the curved surface that presses against the outer surface of the curved wall portion of the container.

4. The energy storage device of claim 2, wherein the holding unit comprises a pair of first holding members that sandwich the energy storage element in a direction in which the curved portion of the electrode body and the curved wall portion of the container face each other, and a pair of second holding members that sandwich the energy storage element in a direction in which the flat portion and the flat wall portion face each other, wherein the pair of first holding members and the pair of second holding members are separate members, and an inner surface of the first holding member has the curved surface that presses against the curved wall portion of the container, and an inner surface of the second holding member has the flat surface that presses against the flat wall portion of the container.

5. A storage battery comprising a plurality of the storage elements, the plurality of storage elements including a first storage element and a second storage element, the first storage element comprising: a first electrode body having the same configuration as the electrode body; and a first container having the same configuration as the container, the first electrode body being in a flat shape with a first flat portion having the same configuration as the flat portion and a first curved portion having the same configuration as the curved portion, the first container comprising: a first flat wall portion having the same configuration as the flat wall portion and a first curved wall portion having the same configuration as the curved wall portion, the second storage element comprising: a second electrode body having the same configuration as the electrode body; and a second container having the same configuration as the container, the second electrode body being in a flat shape with a second flat portion having the same configuration as the flat portion and a second curved portion having the same configuration as the curved portion, the second container comprising: a second flat wall portion having the same configuration as the flat wall portion and a second curved wall portion having the same configuration as the curved wall portion, 5. The energy storage device of claim 4, wherein a surface of the first flat wall portion of the first container of the first energy storage element and a surface of the second flat wall portion of the second container of the second energy storage element are arranged to face each other, an inner surface of the first retaining member has a plurality of the curved surfaces integrated together, the plurality of curved surfaces include a first curved surface facing the first curved wall portion and a second curved surface facing the second curved wall portion, an outer surface of the first curved wall portion of the first container is pressed against the first curved surface of the first retaining member, thereby compressing the first curved portion of the first electrode body, and an outer surface of the second curved wall portion of the second container is pressed against the second curved surface of the first retaining member, thereby compressing the second curved portion of the second electrode body.

6. The electricity storage device according to any one of claims 1 to 5, wherein the holding unit is made of foamed resin.

7. The power storage device according to any one of claims 1 to 5, wherein the holding unit includes a coolant passage through which a coolant flows.

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