Energy storage device

Abstract

This power storage device is equipped with: an outer body; a plurality of power storage elements which are arranged in a second direction perpendicular to a first direction in an orientation in which the gas discharge valve of each faces the first direction; and a gas diffusion member. The gas diffusion member is a metal plate-shaped member positioned so as to face the gas discharge valves of the plurality of power storage elements. The gas diffusion member is positioned: in a location between the plurality of power storage elements and a lid, which is another member positioned in a location facing the plurality of power storage elements in the first direction; and in a location which is separated from each of the plurality of power storage elements and from the lid. The gas diffusion member is formed in a shape and size which permit the passage of a gas in the first direction both to the side of the gas diffusion member in the second direction and to the side of the gas diffusion member in a third direction which intersects the first and second directions.

Description

Technical Field

[0001] The present invention relates to a power storage device including a plurality of power storage elements and an exterior body that houses the plurality of power storage elements.

Background Art

[0002] Patent Document 1 discloses a battery pack (power storage device) including a battery stack having a plurality of cells (power storage elements) and a case (exterior body) that houses the battery stack. In this power storage device, each power storage element has a gas discharge valve configured to discharge internal gas to the outside when the internal pressure rises. On the inner surface of the upper case, which is the lid of the exterior body, a metal plate is attached by a fixture such as a bolt at a position overlapping each gas discharge valve in a plan view. This prevents the high-temperature gas discharged vigorously from the gas discharge valve from directly hitting the lid.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above conventional power storage device, for example, since the heat of the gas easily transfers to the resin lid through the metal plate, this heat may cause a decrease in strength or melting of the portion of the lid where the plate is fixed. When a decrease in strength or melting occurs in a part of the exterior body, gas may leak from an unexpected position of the exterior body, or the exterior body may be damaged by the internal pressure of the gas. That is, the state of the power storage device may further deteriorate.

[0005] This invention was made by the present inventors by newly focusing on the above-mentioned problems, and aims to provide an energy storage device that can suppress further deterioration of the condition when an unsafe event occurs. [Means for solving the problem]

[0006] An energy storage device according to one aspect of the present invention comprises an outer casing, a plurality of energy storage elements housed in the outer casing and arranged in a second direction intersecting the first direction, each with its gas discharge valve facing the first direction, and a metal, plate-shaped gas diffusion member positioned opposite the gas discharge valves of the plurality of energy storage elements, wherein the gas diffusion member is positioned between the plurality of energy storage elements and another member positioned opposite the plurality of energy storage elements in the first direction, and is spaced apart from the plurality of energy storage elements and the other member, and is formed in a shape and size that allows gas to pass in the first direction on both the side in the second direction and the side in a third direction intersecting the first and second directions. [Effects of the Invention]

[0007] According to the present invention, the energy storage device can suppress further deterioration of the condition in the event of an unsafe event. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view showing the external appearance of an energy storage device according to an embodiment. [Figure 2] Figure 2 is an exploded perspective view showing an overview of the configuration of the energy storage device according to the embodiment. [Figure 3] Figure 3 is an exploded perspective view showing the general configuration of the energy storage element according to the embodiment. [Figure 4] Figure 4 is a perspective view showing the gas diffusion member and its surrounding configuration according to an embodiment. [Figure 5] Figure 5 is a first cross-sectional view of the energy storage device according to the embodiment. [Figure 6]Figure 6 is a second cross-sectional view of the energy storage device according to the embodiment. [Figure 7] Figure 7 is a cross-sectional view of a power storage element according to a modified example 1 of the embodiment. [Figure 8] Figure 8 is a cross-sectional view of a power storage element according to a modified example 2 of the embodiment. [Figure 9] Figure 9 is a cross-sectional view of a power storage element according to a modified example 3 of the embodiment. [Modes for carrying out the invention]

[0009] An energy storage device according to one aspect of the present invention comprises an outer casing, a plurality of energy storage elements housed in the outer casing and arranged in a second direction intersecting the first direction, each with its gas discharge valve facing the first direction, and a metal, plate-shaped gas diffusion member positioned opposite the gas discharge valves of the plurality of energy storage elements, wherein the gas diffusion member is positioned between the plurality of energy storage elements and another member positioned opposite the plurality of energy storage elements in the first direction, and is spaced apart from the plurality of energy storage elements and the other member, and is formed in a shape and size that allows gas to pass in the first direction on both the side in the second direction and the side in a third direction intersecting the first and second directions.

[0010] With this configuration, for example, if one energy storage element opens, the gas ejected from the gas discharge valve collides with the gas diffusion member, dispersing its pressure and lowering its temperature. Furthermore, the gas diffusion member is positioned at a distance from other components (such as the lid of the outer casing) located on the first direction side of the multiple energy storage elements. Therefore, the heat from the gas diffusion member, which is made of a metal with high thermal conductivity, is less likely to be transferred to these other components. Consequently, the possibility of a decrease in strength or melting of other components made of resin or the like due to the heat of the gas is reduced. Moreover, the gas ejected in the first direction and colliding with the gas diffusion member can, at least, bypass the gas diffusion member from both the second and third direction sides and spread into the space on the first direction side of the gas diffusion member. This allows the gas to be diffused using a wide range of the internal space of the outer casing, and as a result, the gas pressure and temperature can be rapidly reduced. Thus, the energy storage device according to this embodiment can suppress further deterioration of the condition in the event of an unsafe event.

[0011] The gas diffusion member may have a plurality of through holes that penetrate in the first direction.

[0012] With this configuration, some of the gas that collides with the gas diffusion member can penetrate it. In other words, the number of directions of gas flow that collides with the gas diffusion member increases, so that the gas pressure is efficiently distributed and the gas temperature is efficiently reduced.

[0013] The energy storage device may further include a busbar holder positioned on the first direction side of the plurality of energy storage elements and holding busbars electrically connected to the plurality of energy storage elements, wherein the busbar holder has a support portion that supports the gas diffusion member in a state separated from the plurality of energy storage elements and the other members.

[0014] With this configuration, the gas diffusion member can be supported by the busbar holder necessary for holding the busbar, etc., eliminating the need to provide a new dedicated member for positioning the gas diffusion member in a predetermined location.

[0015] The exterior body may include an exterior body main body that houses the plurality of power storage elements, and a lid that closes an opening of the exterior body main body, and the lid may have a support portion that supports the gas diffusion member in a suspended state while being separated from the plurality of power storage elements and the other members.

[0016] According to this configuration, since the gas diffusion member can be supported by the lid of the exterior body, there is no need to newly provide a dedicated member for arranging the gas diffusion member at a predetermined position.

[0017] The exterior body may have an exhaust port for discharging the gas inside the exterior body to the outside, and the gas diffusion member may be arranged at a position between the gas discharge valve and the exhaust port in the first direction.

[0018] According to this configuration, the gas ejected from the gas discharge valve in the first direction and diffused by the gas diffusion member is discharged to the outside of the exterior body through an opening located further on the first direction side than the gas diffusion member. That is, the gas ejected from at least one gas discharge valve and whose pressure (flow rate) and temperature are reduced by the gas diffusion member is efficiently discharged to the outside of the exterior body.

[0019] Hereinafter, a power storage device according to an embodiment (including a modified example) of the present invention will be described with reference to the drawings. Each of the embodiments described below shows comprehensive or specific examples. Numerical values, shapes, materials, components, arrangement positions of components, connection forms, etc. shown in the following embodiments are examples and are not intended to limit the present invention. In each figure, dimensions, etc. are not shown precisely.

[0020] In the following description and drawings, the direction in which multiple energy storage elements are arranged, the direction in which the long sides of the containers of the energy storage elements face each other, or the thickness direction of the container is defined as the X-axis direction (except for Modification 3). The direction in which the electrode terminals of a single energy storage element are arranged, or the direction in which the short sides of the containers of the energy storage element face each other is defined as the Y-axis direction (except for Modifications 2 and 3). The direction in which the main body and the lid of the energy storage device are arranged, or the vertical direction is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in the following embodiments). Depending on the usage, the Z-axis direction may not be the vertical direction, but for the sake of explanation, the Z-axis direction will be described as the vertical direction below.

[0021] In the following embodiments, expressions indicating relative directions or orientations, such as parallel and orthogonal, may be used, but these expressions may not strictly include cases where the directions or orientations are not exactly as described. For example, two directions being parallel means not only that the two directions are perfectly parallel, but also that they are substantially parallel, i.e., that they include a difference of, for example, a few percent. In the following description, for example, the X-axis positive direction refers to the direction of the arrow on the X-axis, and the X-axis negative direction refers to the direction opposite to the X-axis positive direction. The same applies to the Y-axis and Z-axis directions. Furthermore, when simply referred to as "X-axis direction," it means either the bidirectional or unidirectional direction parallel to the X-axis. The same applies to the terminology related to the Y-axis and Z-axis.

[0022] (Embodiment) [1. General explanation of energy storage devices] First, a general description of the energy storage device 1 according to the embodiment will be given using Figures 1 and 2. Figure 1 is a perspective view showing the external appearance of the energy storage device 1 according to the embodiment. Figure 2 is an exploded perspective view showing the configuration overview of the energy storage device 1 according to the embodiment. Figure 3 is an exploded perspective view showing the configuration overview of the energy storage element 20 according to the embodiment.

[0023] The energy storage device 1 is a device that can charge electricity from an external source and discharge electricity to the outside, and in this embodiment, it has a substantially rectangular parallelepiped shape. For example, the energy storage device 1 is a battery module (battery pack) used for power storage or power supply purposes. Specifically, the energy storage device 1 is used as a battery for driving or starting the engine of mobile vehicles such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, or railway vehicles for electric railways. Examples of automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and gasoline automobiles. Examples of railway vehicles for electric railways include electric trains, monorails, and linear motor cars. The energy storage device 1 can also be used as a stationary battery for household or commercial use.

[0024] As shown in Figures 1 and 2, the energy storage device 1 comprises a plurality of energy storage elements 20 and an outer casing 10 that houses the plurality of energy storage elements 20. In this embodiment, the outer casing 10 houses eight energy storage elements 20. The number of energy storage elements 20 in the energy storage device 1 is not limited to eight. The energy storage device 1 may have two or more energy storage elements 20. In this embodiment, a plurality of energy storage elements 20 arranged in the X-axis direction constitute one energy storage element unit 28. The energy storage element unit 28 may have spacers and insulating films, etc., which are not shown.

[0025] The casing 10 comprises a main casing body 12 that houses the energy storage element unit 28, and a cover 11 that closes the opening (main body opening 15) of the main casing body 12. Inside the casing 10, a busbar holder 17 is positioned between the energy storage element unit 28 housed in the main casing body 12 and the cover 11. The busbar holder 17 holds a plurality of busbars 33. Electrical equipment such as control circuits and relays, as well as wires, may be positioned between the busbar holder 17 and the cover 11, but their illustration and description are omitted.

[0026] The outer casing 10 is a rectangular (box-shaped) container (module case) that constitutes the outer shell of the energy storage device 1. In other words, the outer casing 10 is a component that fixes the energy storage element unit 28 and the busbar holder 17, etc., in predetermined positions and protects them from impacts, etc. The outer casing 10 is formed from insulating materials such as polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (including modified PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyetheretherketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyethersulfone (PES), ABS resin, or composite materials thereof, or from metal with an insulating coating.

[0027] The lid 11 of the outer casing 10 is a rectangular member that closes the main body opening 15 of the outer casing body 12 and has an external terminal 91 on the positive side and an external terminal 92 on the negative side. The external terminals 91 and 92 are electrically connected to a plurality of energy storage elements 20 via a busbar 33, and the energy storage device 1 charges with electricity from the outside and discharges electricity to the outside via these external terminals 91 and 92. The external terminals 91 and 92 are made of a conductive metal such as aluminum or an aluminum alloy. The outer casing body 12 of the outer casing 10 is a bottomed rectangular cylindrical housing with a main body opening 15 formed for housing the energy storage element unit 28. The outer casing body 12 has a pair of walls 14 facing each other in the X-axis direction and a pair of walls 13 facing each other in the Y-axis direction. The main body opening 15 is formed by the upper ends of these four walls. The main body opening 15 and the lid 11 are joined together without any gaps, for example, by heat welding, adhesive bonding, or fastening with a gasket in between.

[0028] The energy storage element 20 is a secondary battery (single cell) capable of charging and discharging electricity, and more specifically, a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 20 may be a secondary battery other than a non-aqueous electrolyte secondary battery, or it may be a capacitor. The energy storage element 20 may be a primary battery that allows the user to use the stored electricity without charging it. The energy storage element 20 may be a battery using a solid electrolyte. The energy storage element 20 may be a pouch-type energy storage element.

[0029] In this embodiment, the energy storage element 20 comprises a flat, rectangular (square) metal container 21. The container 21 is a square case having a pair of opposing long sides 21a, a pair of opposing short sides 21b, and a terminal arrangement surface 21c connected to the upper ends of the pair of long sides 21a and the pair of short sides 21b. Specifically, as shown in Figure 3, the container 21 has a container body 25 and a lid plate 24 that closes the opening of the container body 25. The four sides of the container body 25 form the pair of long sides 21a and the pair of short sides 21b. The upper surface of the lid plate 24 forms the terminal arrangement surface 21c. The container body 25 houses an electrode body 26, current collectors 27 on the positive and negative sides, and an electrolyte (not shown). In this embodiment, each of the multiple energy storage elements 20 is arranged in a line along the X-axis direction with its long side 21a facing the X-axis direction (and its short side 21b parallel to the X-axis direction).

[0030] In this embodiment, the electrode body 26 is a wound-type electrode body formed by winding electrode plates (positive electrode plate and negative electrode plate) with a separator in between. Both ends of the electrode body 26 in the winding axis direction (Y axis direction) are joined to the legs of the current collector 27. The electrode body provided in the energy storage element 20 is not limited to the wound type. For example, the energy storage element 20 may be provided with a laminated electrode body made by stacking flat electrode plates, or an electrode body having a structure in which long strip-shaped electrode plates are stacked in a bellows-like manner by repeatedly folding mountain folds and valley folds. When the energy storage element 20 is provided with a wound-type electrode body, the orientation of the electrode body does not need to be such that the winding axis direction is parallel to the Y axis direction (the opposing direction of the pair of short sides 21b). For example, the electrode body may be provided in the energy storage element 20 in an orientation where the winding axis direction is parallel to the Z axis direction (the longitudinal direction of the short sides 21b).

[0031] On the terminal arrangement surface 21c of the lid plate 24, metal electrode terminals 22 (positive and negative terminals) are arranged, electrically connected to the electrode body 26 inside the container body 25 via a current collector 27. The electrode terminals 22 are fixed to the lid plate 24 via, for example, a resin gasket (not shown). The lid plate 24 of the container 21 is further provided with a gas discharge valve 23 for discharging gas from inside the container 21 to the outside. The gas discharge valve 23 has the function of discharging gas from inside the container 21 to the outside of the container 21 by opening (opening the valve) when the internal pressure of the container 21 rises, for example, due to the vaporization of the electrolyte inside the container 21. More specifically, when the gas discharge valve 23 is subjected to internal pressure, it may break or deform, forming an opening (exhaust port) at the location of the gas discharge valve 23 on the lid plate 24, and gas is discharged from this exhaust port. Therefore, the formation of an exhaust port due to the rupture of the gas exhaust valve 23, etc., is expressed, for example, as "the gas exhaust valve 23 (or energy storage element 20) opens." Furthermore, the discharge of gas from this exhaust port is expressed, for example, as "gas is discharged from the gas exhaust valve 23 (or energy storage element 20)."

[0032] In this embodiment, the gas discharge valve 23 of each of the multiple energy storage elements 20 is oriented in the Z-axis positive direction, which is an example of a first direction. The X-axis direction, which is the direction in which the multiple energy storage elements 20 are aligned, is an example of a second direction intersecting the first direction, and the Y-axis direction is an example of a third direction intersecting both the first and second directions.

[0033] Other components, such as insulating sheets and spacers (not shown), may be placed inside the container 21. In this embodiment, a rectangular parallelepiped (square) energy storage element 20 is shown, but the shape of the energy storage element 20 is not limited to a rectangular parallelepiped, and may be a polygonal prism or other shape.

[0034] The busbar 33 is a rectangular plate-shaped member that is held by the busbar holder 17 and positioned on at least two energy storage elements 20, electrically connecting the electrode terminals 22 of the at least two energy storage elements 20. The material of the busbar 33 is not particularly limited and may be made of metals such as aluminum, aluminum alloy, copper, copper alloy, or a combination thereof, or of a conductive material other than metal. In this embodiment, five busbars 33 are used to connect two energy storage elements 20 in parallel to form four sets of energy storage element groups 20, and these four sets of energy storage element groups 20 are connected in series. There are no particular limitations on the manner in which the eight energy storage elements 20 are electrically connected; for example, all eight energy storage elements 20 may be connected in series.

[0035] The busbar holder 17 is a resin component that holds the busbars 33. The resin material used to form the busbar holder 17 is the same as that used for the outer casing 10, such as PC, PP, PE, PS, or PPS. In this embodiment, the busbar holder 17 also plays a role in supporting the gas diffusion member 50, which will be described later. The busbar holder 17 is provided with multiple busbar openings 17a that hold each of the multiple busbars 33 and expose a portion of each of the multiple busbars 33 to the side of the multiple energy storage elements 20.

[0036] The busbar holder 17 is further provided with an elongated exhaust opening 18 in the direction of the arrangement of the multiple energy storage elements 20. The exhaust opening 18 is positioned in the energy storage element unit 28 opposite to the multiple gas discharge valves 23 arranged in that direction. The gas discharged from these gas discharge valves 23 can pass through the busbar holder 17 in the positive Z-axis direction via the exhaust opening 18.

[0037] In the energy storage device 1 according to this embodiment, a gas diffusion member 50 is positioned opposite the multiple gas discharge valves 23 to diffuse the gas ejected from the gas discharge valves 23 when the gas discharge valves 23 are opened. Specifically in this embodiment, multiple support parts 19 are arranged around the exhaust opening 18 in the busbar holder 17, and the gas diffusion member 50 is supported by these support parts 19. As a result, the gas diffusion member 50 is positioned at a distance from both the energy storage element unit 28 and the lid 11 in the Z-axis direction. In other words, the gas traveling in the Z-axis positive direction through the exhaust opening 18 is diffused in various directions by the gas diffusion member 50 positioned further ahead. The gas is then discharged to the outside of the outer casing 10 through the exhaust pipe 120 provided in the lid 11. This prevents further deterioration of the state of the energy storage device 1 in the event that the energy storage element 20 opens due to some abnormality. The configuration of the gas diffusion member 50 and its surroundings according to this embodiment will be described below with reference to Figures 4 to 6.

[0038] [2. Gas diffusion member and its surrounding structure] Figure 4 is a perspective view showing the gas diffusion member 50 and its surrounding configuration according to the embodiment. In Figure 4, only the lid 11, the gas diffusion member 50, and the energy storage element unit 28 are shown, and each is shown separately in the Z-axis direction. The open-circle and dotted arrows shown in Figures 4 and later schematically indicate the gas flow. Figure 5 is a first cross-sectional view of the energy storage device 1 according to the embodiment, and Figure 6 is a second cross-sectional view of the energy storage device 1 according to the embodiment. In Figure 5, a simplified cross-section of the energy storage device 1 in the YZ plane passing through the line IV-IV in Figure 2 is shown. In Figure 6, a simplified cross-section of the energy storage device 1 in the XZ plane passing through the line VV in Figure 2 is shown. In Figures 5 and 6, the external shape of the energy storage element 20 when viewed from the X-axis direction or the Y-axis direction is shown, and the approximate area of ​​the gas discharge valve 23 is represented by a hatched rectangle.

[0039] As shown in Figures 4 to 6, the energy storage device 1 according to this embodiment is provided with a gas diffusion member 50 positioned opposite the energy storage element unit 28 having a plurality of energy storage elements 20. The gas diffusion member 50 is a metal plate-shaped member, with its thickness direction facing the energy storage element unit 28, and positioned to cover a plurality of gas discharge valves 23 arranged in line in the X-axis direction when viewed from the Z-axis positive direction (plan view). The metal forming the gas diffusion member 50 can be iron, stainless steel, aluminum, or an aluminum alloy. Therefore, the gas diffusion member 50 will not melt due to the high temperature gas (for example, around 400°C) ejected from the gas discharge valves 23 when the valves are opened.

[0040] More specifically, the size and shape of the gas diffusion member 50 in plan view are such that, in plan view, it covers the plurality of gas discharge valves 23 and a portion of the energy storage element unit 28 is exposed in both the X-axis direction and the Y-axis direction. In this embodiment, the gas diffusion member 50 is rectangular in plan view, but the shape in plan view may be a polygon other than a rectangle, an ellipse, or an oblong shape. The position of the gas diffusion member 50 in the Z-axis direction is, as shown in Figures 5 and 6, between the energy storage element unit 28 and the cover 11, and spaced apart from both the energy storage element unit 28 and the cover 11. In other words, a space is formed in the vertical direction (Z-axis direction) and the lateral direction (direction parallel to the XY plane) of the gas diffusion member 50, allowing gas to move. That is, if the Z-axis positive direction, the X-axis direction, and the Y-axis direction are expressed as the first direction, second direction, and third direction in this order, the basic configuration of the energy storage device 1 according to this embodiment is described as follows.

[0041] The energy storage device 1 comprises an outer casing 10, a plurality of energy storage elements 20 housed in the outer casing 10 and arranged in a second direction (X-axis direction) intersecting the first direction, each with its gas discharge valve 23 facing the first direction (Z-axis positive direction), and a gas diffusion member 50. The gas diffusion member 50 is a metal, plate-shaped member positioned opposite the gas discharge valves 23 of the plurality of energy storage elements 20. The gas diffusion member 50 is positioned between the plurality of energy storage elements 20 and a lid 11, which is another member positioned opposite the plurality of energy storage elements 20 in the first direction, and is spaced apart from each of the plurality of energy storage elements 20 and the lid 11. The gas diffusion member 50 is formed in a shape and size that allows gas to pass in the first direction on both the side in the second direction and the side in the third direction (Y-axis direction) intersecting the first and second directions.

[0042] In the energy storage device 1 configured in this way, for example, when one energy storage element 20 opens, the gas ejected from the gas discharge valve 23 of that energy storage element 20 collides with the gas diffusion member 50, dispersing its pressure and lowering its temperature. Furthermore, the gas diffusion member 50 is positioned at a distance from other members (in this embodiment, the lid 11) located on the first direction side of the multiple energy storage elements 20. Therefore, the heat from the gas diffusion member 50, which is made of a metal with high thermal conductivity, is less likely to be transferred to the lid 11. Consequently, the possibility of the lid 11, which is made of resin or the like, losing strength or melting due to the heat of the gas is reduced. Moreover, the gas ejected in the first direction and colliding with the gas diffusion member 50 can, at least, bypass the gas diffusion member 50 from the sides (both the second and third direction sides) and spread into the space on the first direction side of the gas diffusion member 50. In other words, the gas diffusion member 50 is not positioned to partition (divide) the space inside the outer casing 10. The gas diffusion member 50 is formed in a shape and size that creates a space to the side of it that serves as a gas flow path, so that gas that collides with the gas diffusion member 50 spreads beyond the gas diffusion member 50. This allows the gas to be diffused by making extensive use of the internal space of the outer casing 10, and as a result, the gas pressure and temperature can be rapidly reduced. Thus, according to the energy storage device 1 of this embodiment, further deterioration of the condition in the event of an unsafe event can be suppressed.

[0043] The distance between the energy storage element 20 (more specifically, the gas discharge valve 23) and the gas diffusion member 50 in the first direction is preferably greater than half of the maximum outer dimension of the gas discharge valve 23 in a plan view (radius in the case of a circle) in order to suppress interference between the gas discharge valve 23 and the gas diffusion member 50 when the valve is open. It is even more preferable that this distance is greater than the maximum outer dimension of the gas discharge valve 23 (diameter in the case of a circle).

[0044] The distance between the gas diffusion member 50 and the other member (lid 11) in the first direction is preferably 1 mm or more, and more preferably 5 mm or more, in order to suppress heat conduction from the gas diffusion member 50 to the lid 11.

[0045] When a temperature sensor (e.g., a thermistor) is placed in the energy storage device 1 to monitor the state of the energy storage device 1, the temperature sensor may be placed in contact with the gas diffusion member 50. This allows for rapid detection of the temperature rise when the valve is opened by utilizing the gas diffusion member 50, which has high thermal conductivity due to being made of metal. The gas diffusion member 50 is preferably placed in the central part of the gas diffusion member 50 in a plan view. This allows for rapid detection of the temperature rise when the valve is opened of one or more energy storage elements 20 over a wide area using, for example, a single temperature sensor. This is advantageous, for example, in simplifying the configuration of the energy storage device 1 or reducing the manufacturing cost of the energy storage device 1.

[0046] The gas diffusion member 50 according to this embodiment is configured to allow a portion of the gas that collides with the gas diffusion member 50 to pass through in the direction of the collision. Specifically, the gas diffusion member 50 has a plurality of through holes 51 that penetrate in the first direction. In other words, as shown in Figures 4 to 6, the plate-shaped gas diffusion member 50 has a plurality of through holes 51 that penetrate in the thickness direction.

[0047] As a result, some of the gas that collides with the gas diffusion member 50 can penetrate it. Consequently, the number of directions in which the gas can flow after colliding with the gas diffusion member 50 increases. Specifically, as shown in Figures 4 to 6, the gas that collides with the gas diffusion member 50 can not only bypass the gas diffusion member 50 by going around its side, but can also pass through it in the direction of impact. Since the gas diffusion member 50 is positioned at a distance from the lid 11, which is another component located directly above it, the gas that passes through the gas diffusion member 50 diffuses at least in the space between the gas diffusion member 50 and the lid 11. Therefore, the pressure of the gas ejected from the gas discharge valve 23 of the energy storage element 20 is efficiently dispersed, and the temperature of the gas is also efficiently reduced. Consequently, the possibility of the lid 11 being deformed or damaged by the heat or pressure of the gas is reduced. The multiple through-holes 51 allow the gas diffusion member 50 to release the pressure it receives from the gas ejected from the gas discharge valve 23, thereby suppressing deformation or damage to the gas diffusion member 50 due to the pressure of the gas. Therefore, for example, a relatively thin (low rigidity) metal plate can be used as the base material for the gas diffusion member 50, thereby reducing the weight of the energy storage device 1.

[0048] The shape and size of the through-holes 51 are not limited to any particular shape and size. Each of the multiple through-holes 51 may be, for example, a circular hole with an inner diameter of about 1 to 5 mm, or a hole of any shape with a maximum inner dimension of 1 mm or less. The shape and size of the multiple through-holes 51 do not have to be uniform, and at least one of the shape and size may be random. The gas diffusion member 50 having multiple through-holes 51 does not have to be a plate-shaped metal plate with multiple through-holes 51 arranged in a matrix, as shown in Figures 4 to 6. For example, a plate-shaped metal net or steel wool may be used as the gas diffusion member 50 having multiple through-holes 51.

[0049] In this embodiment, the energy storage device 1 includes a busbar holder 17 positioned on the first direction side of the plurality of energy storage elements 20 and holding busbars 33 electrically connected to the plurality of energy storage elements 20. The busbar holder 17 has support portions 19 that support the gas diffusion member 50 in a state separated from the plurality of energy storage elements 20 and the cover 11. More specifically, the busbar holder 17 has four support portions 19 distributed around the exhaust opening 18, and these four support portions 19 support the gas diffusion member 50 at four points.

[0050] With this configuration, the gas diffusion member 50 can be supported by the busbar holder 17, which is necessary for holding the busbar 33, etc., so there is no need to provide a new dedicated member for positioning the gas diffusion member 50 in a predetermined location. The member having a support portion 19 that supports the gas diffusion member 50 in a state separated from the gas discharge valve 23 and the cover 11 is not limited to the busbar holder 17. For example, the support portion 19 may be provided on a tray or case that holds electrical equipment such as a control circuit and relays. Alternatively, for example, one or more rod-shaped (or string-shaped) members that connect the inner surface of the outer casing body 12 and the gas diffusion member 50 in the lateral direction (a direction parallel to the XY plane) may be used as support portions that support the gas diffusion member 50 in a state separated from the gas discharge valve 23 and the cover 11. In other words, the support portion that supports the gas diffusion member 50 may be realized by a member dedicated to supporting the gas diffusion member 50.

[0051] In this embodiment, the outer casing 10 has an outlet 121 for discharging gas from inside the outer casing 10 to the outside. The gas diffusion member 50 is positioned between the gas discharge valve 23 and the outlet 121 in the first direction. Specifically, as shown in Figures 5 and 6, the outlet 121 is provided on the inside side of the lid 11 of the outer casing 10. The outlet 121 is formed in a position that communicates with an exhaust pipe 120 which is provided protruding from the outer surface of the lid 11. In other words, gas that flows from inside the outer casing 10 into the outlet 121 passes through the exhaust pipe 120 and is discharged to the outside of the outer casing 10.

[0052] In this configuration, the gas ejected from the gas discharge valve 23 in a first direction and diffused by the gas diffusion member 50 is discharged to the outside of the outer casing 10 from the outlet 121, which is located further to the first direction than the gas diffusion member 50. In other words, the gas ejected from at least one gas discharge valve 23 and whose pressure (flow velocity) and temperature have been reduced by the gas diffusion member 50 is efficiently discharged to the outside of the outer casing 10.

[0053] The above describes an embodiment of the energy storage device 1 according to the present invention. However, the energy storage device 1 may have configurations for the gas diffusion member 50 and its surroundings that differ from those shown in Figures 2 to 6. Therefore, various modifications of the gas diffusion member 50 and its surroundings will be explained using Figures 7 to 9, focusing on the differences from the above embodiment.

[0054] [3-1. Variation 1] Figure 7 is a cross-sectional view of the energy storage device 1a according to modified embodiment 1. The position of the cross-section in Figure 7, and supplementary information such as the fact that the cross-section is simply illustrated, are the same as those in Figure 5 described above. This also applies to Figures 8 and 9, which will be described later.

[0055] As shown in Figure 7, the energy storage device 1a according to this modified example includes a metal, plate-shaped gas diffusion member 50. The gas diffusion member 50 is positioned between the lid 11a and the plurality of energy storage elements 20, and is spaced apart from each of the plurality of energy storage elements 20 and the lid 11a. These configurations are common to the energy storage device 1 according to the embodiment. The energy storage device 1a according to this modified example differs from the energy storage device 1 according to the embodiment in that the gas diffusion member 50 is supported by a support portion 19a provided on the lid 11a.

[0056] In other words, in this modified example, the exterior body 10a has an exterior body main body 12a that houses a plurality of energy storage elements 20 and a lid 11a that closes the opening 15 of the main body. The lid 11a has a support portion 19a that supports the gas diffusion member 50 in a suspended manner, spaced apart from the plurality of energy storage elements 20 and the lid 11a, which is another component.

[0057] With this configuration, the gas diffusion member 50 can be supported by the lid 11a of the outer casing 10, so there is no need to provide a new dedicated member for positioning the gas diffusion member 50 in a predetermined location.

[0058] When the gas diffusion member 50 is supported by the lid 11a, it is not essential to support the gas diffusion member 50 in a suspended manner. For example, one or more rod-shaped (or string-shaped) members that connect the inner surface of the lid 11a and the gas diffusion member 50 in the lateral direction may be used as support parts that support the gas diffusion member 50 at a distance from the gas discharge valve 23 and the lid 11a.

[0059] [3-2. Variation 2] Figure 8 is a cross-sectional view of a modified embodiment 2 of the energy storage device 1b. As shown in Figure 8, the energy storage device 1b according to this modified embodiment comprises an energy storage element unit 28 having a plurality of energy storage elements 20 arranged in the X-axis direction, and an outer casing 10b that houses the energy storage element unit 28. The outer casing 10b has an outer casing body 12b and a lid 11b. In the energy storage device 1b configured in this way, a metal, plate-shaped gas diffusion member 50 is positioned opposite the gas discharge valve 23 of the plurality of energy storage elements 20, and between the plurality of energy storage elements 20 and another component, the wall portion 13b (wall portion 13b of the outer casing body 12b). The gas diffusion member 50 is positioned spaced apart from each of the plurality of energy storage elements 20 and the wall portion 13b. Spaces are formed in the vertical direction (Z-axis direction) and lateral direction (direction parallel to the XY plane) of the gas diffusion member 50, allowing gas to move.

[0060] Thus, the energy storage device 1b according to this modified example has a configuration common to the energy storage device 1 according to the embodiment. The energy storage device 1b according to this modified example differs from the energy storage device 1 according to the embodiment in that each of the multiple energy storage elements 20 is arranged with the gas discharge valve 23 facing in the positive Y-axis direction. More specifically, the multiple energy storage elements 20 are arranged in the X-axis direction with the gas discharge valve 23 facing in the positive Y-axis direction and the long side surface 21a facing in the X-axis direction.

[0061] In the case of the energy storage device 1b having the above configuration, if the Y-axis positive direction, the X-axis direction, and the Z-axis direction are expressed in this order as the first direction, the second direction, and the third direction, the description of its configuration will be the same as the description of the configuration of the energy storage device 1 according to the embodiment. That is, the energy storage device 1b comprises an outer casing 10b, a plurality of energy storage elements 20 housed in the outer casing 10b and arranged in a second direction (X-axis direction) intersecting the first direction, with each element facing the first direction (Y-axis positive direction) and with the gas discharge valve 23 facing the first direction, and a gas diffusion member 50. The gas diffusion member 50 is positioned between the wall portion 13b, which is positioned opposite the plurality of energy storage elements 20 in the first direction, and the plurality of energy storage elements 20, and is positioned spaced apart from each of the plurality of energy storage elements 20 and the wall portion 13b. The gas diffusion member 50 is formed in a shape and size that allows gas to pass in the first direction on both the side in the second direction and the side in the third direction (Z-axis direction) that intersects the first and second directions.

[0062] With this configuration, the energy storage device 1b according to this modified example, like the energy storage device 1 according to the embodiment, can rapidly reduce the pressure and temperature of the gas ejected from the gas discharge valve 23 by the gas diffusion member 50. This suppresses a decrease in strength or melting of the outer casing 10b. Therefore, the energy storage device 1b can suppress further deterioration of the condition in the event of an unsafe event.

[0063] [3-3. Modified Example 3] Figure 9 is a cross-sectional view of a power storage device 1c according to a modified example 3 of the embodiment. As shown in Figure 9, the power storage device 1c according to this modified example comprises a power storage element unit 28 having a plurality of power storage elements 20 arranged in the Z-axis direction, and an outer casing 10c that houses the power storage element unit 28. The outer casing 10c has an outer casing body 12c and a lid 11c. In the power storage device 1c configured in this way, a metal, plate-shaped gas diffusion member 50 is positioned opposite the gas discharge valve 23 of the plurality of power storage elements 20, and between the plurality of power storage elements 20 and another component, the wall portion 13c (wall portion 13c of the outer casing body 12c). The gas diffusion member 50 is positioned spaced apart from the plurality of power storage elements 20 and the wall portion 13c. Spaces are formed in the vertical direction (Z-axis direction) and lateral direction (direction parallel to the XY plane) of the gas diffusion member 50, allowing gas to move.

[0064] Thus, the energy storage device 1c according to this modified example has a configuration common to the energy storage device 1 according to the embodiment. The energy storage device 1c according to this modified example differs from the energy storage device 1 according to the embodiment in that each of the multiple energy storage elements 20 is arranged with the gas discharge valve 23 facing in the positive Y-axis direction. More specifically, the multiple energy storage elements 20 are arranged in the Z-axis direction with the gas discharge valve 23 facing in the positive Y-axis direction and the short side 21b facing in the X-axis direction. In other words, in this modified example, the multiple energy storage elements 20 are stacked in the vertical direction.

[0065] In the case of the energy storage device 1c having the above configuration, if the Y-axis positive direction, the Z-axis direction, and the X-axis direction are expressed in this order as the first direction, second direction, and third direction, the description of its configuration is the same as the description of the configuration of the energy storage device 1 according to the embodiment. That is, the energy storage device 1c comprises an outer casing 10c, a plurality of energy storage elements 20 housed in the outer casing 10c and arranged in a second direction (Z-axis direction) intersecting the first direction, with each element facing the first direction (Y-axis positive direction) and with the gas discharge valve 23 facing the first direction, and a gas diffusion member 50. The gas diffusion member 50 is positioned between the wall portion 13b, which is positioned opposite the plurality of energy storage elements 20 in the first direction, and the plurality of energy storage elements 20, and is positioned spaced apart from each of the plurality of energy storage elements 20 and the wall portion 13b. The gas diffusion member 50 is formed in a shape and size that allows gas to pass in the first direction on both the side in the second direction and the side in the third direction (X-axis direction) that intersects the first and second directions.

[0066] With this configuration, the energy storage device 1c according to this modified example, like the energy storage device 1 according to the embodiment, allows the gas diffusion member 50 to rapidly reduce the pressure and temperature of the gas ejected from the gas discharge valve 23. This suppresses a decrease in strength or melting of the outer casing 10c. Therefore, the energy storage device 1c can suppress further deterioration of the condition in the event of an unsafe event.

[0067] [4. Other variations] The energy storage device according to the present invention has been described above based on embodiments and modifications thereof. However, the present invention is not limited to the above embodiments and modifications. As long as it does not depart from the spirit of the present invention, various modifications that a person skilled in the art can conceive of are also included within the scope of the present invention.

[0068] For example, other components positioned in the first direction, which is the direction in which the gas discharge valve 23 is directed toward the energy storage element 20, do not need to be part of the casing 10. For example, if a control device or electrical equipment such as a relay, or a tray for holding electrical equipment, is positioned opposite the gas discharge valve 23 in the first direction, the gas diffusion member 50 is placed between the tray or electrical equipment and the energy storage element 20. This allows the gas to diffuse and spread by the gas diffusion member 50 even if gas is ejected from the gas discharge valve 23, causing the gas temperature and pressure to decrease rapidly, thereby protecting the tray or electrical equipment. In other words, if a component made of a material with a lower melting point than the gas diffusion member 50 (such as resin) is positioned as the other component, the gas diffusion member 50 is positioned at a distance from the other component, allowing the pressure and temperature reduction effect of the gas diffusion member 50 to be obtained while protecting the other component from the gas. In other words, for example, in the structure shown in Figures 4 to 6, even if, for example, electrical equipment is placed between the gas diffusion member 50 and the lid 11, the electrical equipment is protected by the gas diffusion member 50 from the gas ejected from the gas discharge valve 23. Furthermore, the gas diffusion member 50 can diffuse the gas by making extensive use of the internal space of the outer casing 10, and as a result, the gas pressure and temperature are efficiently reduced.

[0069] The gas diffusion member 50 does not need to be shaped and sized to cover all of the gas discharge valves 23 together in a plan view. For example, a separate gas diffusion member may be placed for each of the gas discharge valves 23. Even in this case, as long as there is space to which gas can pass above, below, to the left and right of the gas diffusion member, the gas can be diffused by making full use of the internal space of the outer casing 10.

[0070] The gas diffusion member 50 does not need to be supported by any member other than the energy storage element 20, such as the busbar holder 17, and may be supported by the energy storage element 20. For example, the gas diffusion member 50 may be positioned relative to the energy storage element unit 28 by fixing one or more legs extending from the gas diffusion member 50 toward the energy storage element unit 28 to the terminal arrangement surface 21c (see Figure 3) of one or more energy storage elements 20 with an adhesive or the like. As described above, if an individual gas diffusion member is positioned for each of the multiple gas discharge valves 23, each of the multiple energy storage elements 20 may support the gas diffusion member corresponding to that energy storage element 20.

[0071] The present invention also includes configurations constructed by arbitrarily combining the multiple components described above. For example, various supplementary details regarding the energy storage device 1 according to the above embodiment may be applied to any of the energy storage devices 1a to 1c according to Modifications 1 to 3. [Industrial applicability]

[0072] This invention can be applied to energy storage devices equipped with energy storage elements such as lithium-ion secondary batteries. [Explanation of Symbols]

[0073] 1, 1a, 1b, 1c power storage device 10, 10a, 10b, 10c Outer casing 13, 13b, 13c, 14 Wall section 17 Bus bar holder 18 Exhaust opening 19, 19a Support part 20 Energy storage elements 21 Container 23 Gas discharge valve 24 Lid plate 25 Container body 33 Bus Bar 50 Gas diffusion member 51 Through hole 121 Outlet

Claims

1. Exterior body and Housed within the aforementioned exterior, a plurality of energy storage elements are arranged in a second direction intersecting the first direction, each with its gas discharge valve facing the first direction, The plurality of energy storage elements are equipped with a metal, plate-shaped gas diffusion member positioned opposite the gas discharge valve, The aforementioned gas diffusion member is In the first direction, another member is positioned opposite to the plurality of energy storage elements, and is positioned between the plurality of energy storage elements, spaced apart from each of the plurality of energy storage elements and the other member, The gas diffusion member is formed in a shape and size that allows gas to pass in the first direction on both the side in the second direction and the side in the third direction intersecting the first and second directions. The gas diffusion member has a plurality of through holes that penetrate in the first direction, The size of each of the aforementioned multiple through holes is smaller than the size of the gas discharge valve. Energy storage device.

2. Furthermore, the system includes a busbar holder positioned on the first direction side of the plurality of energy storage elements and holding busbars electrically connected to the plurality of energy storage elements, The busbar holder has a support portion that supports the gas diffusion member in a state where it is separated from the plurality of energy storage elements and the other members. The energy storage device according to claim 1.

3. The exterior body comprises an exterior body main body that houses the plurality of energy storage elements and a cover body that closes the opening of the exterior body main body. The cover has a support portion that suspends the gas diffusion member in a manner that is spaced apart from the plurality of energy storage elements and the other members. The energy storage device according to claim 1.

4. The outer casing has an outlet for discharging the gas inside the outer casing to the outside. The gas diffusion member is positioned in the first direction between the gas discharge valve and the discharge port. The energy storage device according to any one of claims 1 to 3.

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