Power storage device

Abstract

To provide a power storage device capable of suppressing damage to a heat welded portion of an exterior body due to expansion of a power storage element.SOLUTION: A power storage device includes a power storage element 20, an end plate 39 arranged in line with the power storage element 20, and an exterior body that houses the power storage element 20 and the end plate 39, and the exterior body includes a first wall portion at a position where the end plate 39 is sandwiched between the power storage element 20 and the first wall portion. The first wall portion includes a joint that joins the first wall portion and a portion of the exterior body other than the first wall portion, the center portion of the end plate 39 protrudes toward the power storage element, the end portion of the end plate 39 is located closer to the first wall portion than the center portion of the end plate 39, and a space is formed between the center portion of the end plate 39 and the first wall portion.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an energy storage device including an energy storage element, an end plate, and an exterior body. [Background technology]

[0002] Conventionally, there is known an electric storage device in which a plurality of electric storage elements, such as lithium ion batteries, are housed in a pair of divided exterior bodies, and the connecting surfaces of the pair of exterior bodies are heat-welded to each other. In such an electric storage device, a pair of flat end plates arranged at positions sandwiching the plurality of electric storage elements are also housed in the exterior body (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-79599 A Summary of the Invention [Problem to be solved by the invention]

[0004] The energy storage element has the characteristic of gradually expanding as it is charged and discharged. Therefore, as the expansion of the energy storage elements progresses, the outermost energy storage element presses the inner surface of the exterior body through the end plate. This increases the stress acting on the heat-sealed parts of the exterior body, which may damage the heat-sealed parts.

[0005] An object of the present invention is to provide an energy storage device that can suppress damage to the heat-welded parts of the exterior body caused by expansion of the energy storage element. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, an energy storage device according to one embodiment of the present invention comprises an energy storage element, an end plate arranged alongside the energy storage element, and an exterior body that houses the energy storage element and the end plate, wherein the exterior body has a first wall portion at a position where the end plate is sandwiched between the energy storage element and the first wall portion, the first wall portion includes a joint portion that joins the first wall portion to a portion of the exterior body other than the first wall portion, a central portion of the end plate protrudes towards the energy storage element, an end portion of the end plate is located closer to the first wall portion than the central portion of the end plate, and a space is formed between the central portion of the end plate and the first wall portion.

[0007] Here, when the multiple energy storage elements expand, the center of one of the inner wall surfaces of the openings in the first member is most likely to deform due to the pressing force applied during expansion. This deformation is likely to cause damage to the heat-sealed portion at a position corresponding to the center of the inner wall surface. On the other hand, the corners of the openings are more rigid than the center of the inner wall surface, and therefore are less likely to deform even when subjected to pressing force. In other words, the heat-sealed portion at a position corresponding to the corners is less likely to be damaged.

[0008] In this embodiment, the abutting portions at both ends of the end plate abut the corners of the opening, and the non-abutting portion at the middle does not abut the inner wall surface of the opening. This allows the pressing force that the inner wall surface of the opening receives through the end plate to be concentrated at the corners and not applied to the center of the inner wall surface. This makes it possible to suppress damage to the heat-sealed portion of the exterior body.

[0009] The abutment portion may be inclined with respect to a pair of edges forming corners of the opening.

[0010] According to this, since the abutment portion of the end plate is inclined with respect to the pair of edges forming the corner portion, when the end plate is subjected to a pressing force, the end plate can be pressed against the inner wall surface. This makes the end plate less likely to deform, and prevents the non-abutment portion from abutting against the inner wall surface, in the unlikely event that the non-abutment portion abuts against the inner wall surface. Therefore, damage to the heat-sealed portion of the exterior body can be more reliably prevented.

[0011] The end plate may have a curved shape in a plan view.

[0012] According to this, since the end plate has a curved shape, the end plate itself can exert an elastic force. Therefore, when the multiple energy storage elements expand, the end plate rebounds, and a restraining force can be applied to the multiple energy storage elements. Therefore, deformation of the end plate itself can be suppressed, and the pressing force acting on the inner wall surface of the first member can also be suppressed. This makes it possible to more reliably suppress damage to the heat-sealed portion of the exterior body.

[0013] The non-contact portion does not have to contact the inner wall surface of the opening from a position corresponding to the center of the energy storage element to a position corresponding to the heat-sealed portion in the insertion direction when multiple energy storage elements are inserted into the opening.

[0014] Here, the energy storage element expands the most at its center. In other words, the central portion of the energy storage element experiences the greatest pressing force when it expands. The non-contact portion does not contact the inner wall surface of the opening from the position corresponding to the central portion of the energy storage element to the position corresponding to the heat-sealed portion, and therefore the portion where the pressing force is greatest can be avoided. Therefore, the end plate itself is less likely to deform, and the pressing force acting on the inner wall surface can also be suppressed. This makes it possible to more reliably suppress damage to the heat-sealed portion of the exterior body.

[0015] The end plate does not need to be restrained within the opening when the plurality of energy storage elements are not expanded.

[0016] When the end plate is restrained together with the multiple energy storage elements via, for example, another restraining member, even if the multiple energy storage elements expand, the restraining force from the restraining member suppresses deformation of the end plate. On the other hand, if the end plate is not restrained within the opening, it is likely to deform due to the pressure exerted by the expansion of the multiple energy storage elements. In other words, it is likely to induce damage to the heat-sealed portion of the exterior body. The configuration of the present invention is suitable for such unrestrained end plates. Effect of the Invention

[0017] According to the electricity storage device of the present invention, damage to the heat-sealed portion of the exterior body caused by expansion of the electricity storage element can be suppressed. [Brief description of the drawings]

[0018] [Figure 1] 1 is a perspective view showing an external appearance of a power storage device according to an embodiment; [Diagram 2] FIG. 2 is an exploded perspective view illustrating each component of the electricity storage device according to the embodiment. [Diagram 3] FIG. 2 is an explanatory diagram showing a schematic configuration of an end plate according to the embodiment. [Figure 4] FIG. 2 is a top view showing a schematic internal structure of a main body according to the embodiment. [Diagram 5] FIG. 11 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 1. [Figure 6] 11 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 2. FIG. [Figure 7] 13 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 3. FIG. [Figure 8] FIG. 13 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 4. [Figure 9] FIG. 13 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, a description will be given of an embodiment of the present invention and a power storage device according to a modified example thereof with reference to the drawings. Note that the embodiment and the modified example described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiment and the modified example are merely examples and are not intended to limit the present invention. Also, the dimensions and the like are not strictly illustrated in each drawing.

[0020] In the following description and drawings, the X-axis direction is defined as the arrangement direction of the energy storage elements, the opposing direction of the long side surfaces of the container of the energy storage elements, or the thickness direction of the container. In addition, the Y-axis direction is defined as the arrangement direction of the electrode terminals of one energy storage element, or the opposing direction of the short side surfaces of the container of the energy storage element. In addition, the Z-axis direction is defined as the arrangement direction of the main body and the outer lid in the exterior body of the energy storage device, or the up-down direction. The Z-axis direction is also the insertion direction when inserting a plurality of energy storage elements into the opening of the main body. These X-axis direction, Y-axis direction, and Z-axis direction are directions that intersect with each other (orthogonal in the following embodiments and their modifications). Note that, depending on the mode of use, the Z-axis direction may not be the up-down direction, but for convenience of explanation, the Z-axis direction will be described as the up-down direction below. In the following description, for example, the positive side of the X-axis direction refers to the side of the arrow on the X-axis, and the negative side of the X-axis direction refers to the opposite side to the positive side of the X-axis direction. The same applies to the Y-axis direction and the Z-axis direction. Furthermore, expressions indicating a relative direction or attitude, such as "parallel" and "orthogonal," also include cases where the direction or attitude is not strictly the same. For example, "two directions are orthogonal" does not only mean that the two directions are completely orthogonal, but also means that the two directions are substantially orthogonal, that is, includes a difference of, for example, about several percent.

[0021] [General description of the power storage device] First, an overall description of a power storage device 1 according to an embodiment will be given with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing the external appearance of the power storage device 1 according to an embodiment. Fig. 2 is an exploded perspective view showing each component when the power storage device 1 according to the embodiment is disassembled.

[0022] The power storage device 1 is a device that can be charged with electricity from the outside and can discharge electricity to the outside, and in this embodiment, has a substantially rectangular parallelepiped shape. For example, the power storage device 1 is a battery module (battery pack) used for power storage or power supply. Specifically, the power storage device 1 is used as a battery for driving or starting an engine of a moving body such as an automobile, a motorcycle, a watercraft, a ship, a snowmobile, an agricultural machine, a construction machine, or a railway vehicle for an electric railway. Examples of the automobile include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a gasoline-powered vehicle. Examples of the railway vehicle for the electric railway include a train, a monorail, and a linear motor car. The power storage device 1 can also be used as a stationary battery for home use or for a power generator.

[0023] 1 and 2, the energy storage device 1 includes an energy storage element 20 and an exterior body 10 that houses the multiple energy storage elements 20. The exterior body 10 includes a main body 11 that houses the multiple energy storage elements 20, a bus bar plate 17 that is disposed above the multiple energy storage elements 20, and an outer lid 12 that covers the upper side of the bus bar plate 17.

[0024] The exterior body 10 is a rectangular (box-shaped) container (module case) that constitutes the exterior body of the energy storage device 1. In other words, the exterior body 10 is a member that fixes the multiple energy storage elements 20, the bus bar plate 17, etc. in predetermined positions and protects these elements from impacts and the like.

[0025] The main body 11 is an example of a first member having an opening 111. The main body 11 is a bottomed rectangular tubular member with an open top, and the open portion is the opening 111. The opening 111 is substantially rectangular in shape in a plan view. A wall 50 is provided at the upper end of the main body 11, continuously surrounding the entire periphery of the opening 111. In addition to the multiple energy storage elements 20 and the bus bar plate 17, the opening 111 of the main body 11 accommodates multiple bus bars 33 held by the bus bar plate 17, a connection unit 80 including a control circuit and the like, and a pair of end plates 39.

[0026] The outer lid 12 is a rectangular member that closes the opening 111 of the main body 11, and is an example of a second member. The outer lid 12 is joined to the main body 11 in a state in which the opening 111 of the main body 11 is covered. The outer lid 12 has a positive external terminal 91 and a negative external terminal 92. The external terminals 91 and 92 are electrically connected to the multiple energy storage elements 20 via the connection unit 80 and the bus bar 33, and the energy storage device 1 charges with electricity from the outside and discharges electricity to the outside via the external terminals 91 and 92. The external terminals 91 and 92 are formed of a conductive member made of metal, such as a copper alloy such as brass, copper, aluminum, or an aluminum alloy. The main body 11 is a bottomed rectangular cylindrical housing (casing) with an opening formed therein, and houses the energy storage elements 20 and the like.

[0027] The main body 11 and the outer lid 12 of the exterior body 10 are formed of 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), polyether ether ketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether sulfone (PES), ABS resin, or composite materials thereof, or metal with insulating coating. This prevents the energy storage element 20 and the like from coming into contact with external metal members and the like. Note that the exterior body 10 may be formed of a conductive material such as metal as long as the electrical insulation of the energy storage element 20 and the like is maintained.

[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 has a flattened rectangular parallelepiped shape (square shape), and in this embodiment, eight energy storage elements 20 are arranged in the X-axis direction. The shape of the energy storage element 20 and the number of the arranged energy storage elements 20 are not limited. In addition, the energy storage element 20 is not limited to a non-aqueous electrolyte secondary battery, and may be a secondary battery other than a non-aqueous electrolyte secondary battery, a capacitor, or a primary battery that allows the user to use stored electricity without charging.

[0029] Specifically, the energy storage element 20 includes a metal container 21. The container 21 is formed in a substantially rectangular parallelepiped shape and has a pair of long side surfaces 211 and a pair of short side surfaces 212 adjacent to the pair of long side surfaces 211. The pair of long side surfaces 211 face each other in the X-axis direction, and the pair of short side surfaces 212 face each other in the Y-axis direction. Each of the multiple energy storage elements 20 is stacked such that the long side surfaces 211 of the containers 21 face each other, and is housed within the main body 11.

[0030] A metallic positive electrode terminal 221 and a negative electrode terminal 222 are provided on the lid of the container 21. An insulating member (not shown) is interposed between the lid and the positive electrode terminal 221 and the negative electrode terminal 222, and the lid is insulated from the positive electrode terminal 221 and the negative electrode terminal 222 by this insulating member.

[0031] The positive electrode terminal 221 and the negative electrode terminal 222 are electrode terminals arranged to protrude from the lid of the container 21 toward the bus bar plate 17 (upward, that is, toward the positive side in the Z-axis direction). The positive electrode terminal 221 and the negative electrode terminal 222 are connected to external terminals 91, 92 via at least one bus bar 33 and a connection unit 80, so that the electricity storage device 1 can charge electricity from the outside and discharge electricity to the outside. The lid of the container 21 may be provided with a liquid injection section for injecting an electrolyte solution, and a gas exhaust valve for releasing pressure by discharging gas when the pressure inside the container 21 increases. In addition, an electrode body (also referred to as an electricity storage element or a power generation element), a current collector (a positive electrode current collector and a negative electrode current collector), and the like are arranged inside the container 21, and an electrolyte solution (a non-aqueous electrolyte) and the like are sealed therein, but a detailed description thereof will be omitted.

[0032] The bus bar 33 is a rectangular plate-like member that is arranged on at least two energy storage elements 20 while being held by the bus bar plate 17, and electrically connects the positive electrode terminals 221 and the negative electrode terminals 222 of the at least two energy storage elements 20. The bus bar 33 is formed of a conductive member made of metal such as copper, a copper alloy, aluminum, an aluminum alloy, or the like. In this embodiment, five bus bars 33 are used to connect two energy storage elements 20 in parallel to configure four sets of energy storage element groups, and the four sets of energy storage element groups are connected in series.

[0033] The connection unit 80 is a unit having a plurality of bus bars and a control board, etc., and connects a group of eight energy storage elements 20 to external terminals 91 and 92. The control board of the connection unit 80 has a plurality of electric components, and a detection circuit for detecting the state of each energy storage element 20 and a control circuit for controlling charging and discharging are formed by these plurality of electric components. In this embodiment, the connection unit 80 is fixed to the bus bar plate 17. The detection circuit and the control circuit may be formed on separate boards. The connection unit 80 does not need to have a control board. In this case, for example, a control device arranged outside the energy storage device 1 may control charging and discharging of each energy storage element 20.

[0034] The busbar plate 17 is an example of a holding member arranged above the plurality of energy storage elements 20 (on the side where the positive electrode terminal 221 and the negative electrode terminal 222 are arranged), and in this embodiment, is a member that holds the busbar 33. More specifically, the busbar plate 17 is a member that holds the plurality of busbars 33, the connection unit 80, and other wirings (not shown), and can regulate the positions of these members. The busbar plate 17 is provided with a plurality of busbar openings 17a that hold each of the plurality of busbars 33 and expose a portion of each of the plurality of busbars 33 to the side of the plurality of energy storage elements 20. The busbar plate 17 is fixed to the main body 11, and thus also has a role of regulating, for example, the movement of the plurality of energy storage elements 20 upward (to the positive side in the Z-axis direction).

[0035] Bus bar plate 17 disposed above the multiple energy storage elements 20 may also be called, for example, a "bus bar frame" or an "inner lid." Bus bar plate 17 is formed from an insulating material such as PC, PP, PE, PS, PPS, PPE (including modified PPE), PET, PBT, PEEK, PFA, PTFE, PES, ABS resin, or a composite material thereof, or a metal with an insulating coating.

[0036] The pair of end plates 39 are rectangular plates disposed in the main body 11 at positions sandwiching the plurality of energy storage elements 20 together. Specifically, the pair of end plates 39 are disposed in positions sandwiching the plurality of energy storage elements 20 in the X-axis direction in an attitude parallel to the YZ plane. That is, the pair of end plates 39 are disposed so as to overlap the long side surface 211 of the container 21 of the energy storage element 20 disposed on the outermost side. The end plates 39 are formed of an insulating member such as PC, PP, PE, PS, PPS, PPE (including modified PPE), PET, PBT, PEEK, PFA, PTFE, PES, ABS resin, or a composite material thereof, or a metal coated with an insulating coating. The end plates 39 will be described in detail later.

[0037] [Joint structure between main body and outer lid] Next, a joining structure between the main body 11 and the outer lid 12 will be described. As shown in Fig. 2 and Fig. 3(c) described later, a skirt portion 123 extending downward is provided on the entire periphery of the outer lid 12. The skirt portion 123 is formed in a rectangular frame shape that is continuous in the circumferential direction when viewed from below.

[0038] Further, in the outer lid 12, a joint portion 124 is formed in the shape of a rectangular frame that is continuous in the circumferential direction when viewed from below, on the inside of the skirt portion 123 (see FIG. 3(c)). The lower end portion of the joint portion 124 is disposed above the lower end portion of the skirt portion 123. The joint portion 124 is a portion that is joined to the wall portion 50 of the main body portion 11.

[0039] Thermal welding is used to join the joint 124 and the wall 50. Thermal welding is a method of joining the members to be joined by melting them with heat, then bringing them into close contact and re-hardening them. Examples of thermal welding include heat sealing and ultrasonic welding. In this disclosure, joining with an adhesive is not included in thermal welding. Even in joining using an adhesive, the members to be joined melt and re-harden, but if the joint is analyzed after hardening, the adhesive remains at the site. Therefore, even after joining, it is possible to determine whether the joint is made by thermal welding or adhesive.

[0040] During thermal welding, in the main body 11, the entire circumference of the tip (upper end) of the wall 50 is heated and melted. On the other hand, in the outer lid 12, the entire circumference of the lower end of the joint 124 is melted. In the melted state, the outer lid 12 is brought close to the main body 11, and the entire circumference of the lower end of the joint 124 is pressed against the entire circumference of the tip of the wall 50, so that the melted parts are mixed together. After a certain period of time has passed in a non-heated state, the mixed parts are hardened and integrated and joined. This joint part is the thermally welded part 90 (see FIG. 3(c)). The thermally welded part 90 is provided continuously along the entire circumference of the opening 111. In other words, the main body 11 and the outer lid 12 have a thermally welded part 90 joined along the entire circumference of the opening 111. 3(c) shows the interface between the tip (lower end) of the joint 124 and the tip (upper end) of the wall 50 with respect to the heat-sealed portion 90, but in reality there is no interface because the two are hardened in a mixed state. The heat-sealed portion 90 seals the main body 11 and the outer lid 12 all around, ensuring airtightness.

[0041] [End plate] Next, the end plate 39 will be described in detail. FIG. 3 is an explanatory diagram showing a schematic configuration of the end plate 39 according to the embodiment. Specifically, FIG. 3(a) is a top view of the end plate 39, FIG. 3(b) is a plan view of the end plate 39, and FIG. 3(c) is a cross-sectional view of the end plate 39. In FIG. 3(a), the opening 111 is indicated by a two-dot chain line, and the energy storage element 20 is indicated by a broken line. In FIG. 3(c), the main body 11 and the outer lid 12 are indicated by a two-dot chain line, and the energy storage element 20 is indicated by a broken line. FIG. 3(c) is a cross-sectional view of a cut surface including the line IIIC-IIIC in FIG. 3(a) and FIG. 3(b).

[0042] Here, the pair of end plates 39 have different postures but the same shape. Specifically, the end plate 39 arranged on the negative side in the X-axis direction has a posture in which the central portion protrudes toward the positive side in the X-axis direction, and the end plate 39 arranged on the positive side in the X-axis direction has a posture in which the central portion protrudes toward the negative side in the X-axis direction. For this reason, in this embodiment, the details of the end plate 39 arranged on the negative side in the X-axis direction will be described, and the details of the end plate 39 arranged on the positive side in the X-axis direction will be omitted. In the following description, in the opening 111, a pair of inner wall surfaces facing each other in the X-axis direction will be referred to as first inner wall surfaces 118, and a pair of inner wall surfaces facing each other in the Y-axis direction will be referred to as second inner wall surfaces 119.

[0043] 3, end plate 39 is a curved plate having a rectangular shape in a plan view. End plate 39 is accommodated in opening 111 and is interposed between energy storage elements 20 arranged on the most negative side in the X-axis direction and a first inner wall surface 118 of opening 111. An upper end portion of end plate 39 is arranged below an upper end portion of main body portion 11, i.e., below thermally welded portion 90.

[0044] End plate 39 is curved such that its central portion protrudes toward the positive side in the X-axis direction in top view, that is, toward energy storage element 20. End plate 39 has a uniform shape over its entire length in the Z-axis direction. Both end portions of end plate 39 are disposed on the negative side in the X-axis direction relative to the central portion. Both end faces of end plate 39 in the Y-axis direction face a pair of second inner wall surfaces 119 of opening 111. Both end faces of end plate 39 in the Y-axis direction may abut against the pair of second inner wall surfaces 119.

[0045] Both ends of the end plate 39 in the Y-axis direction are abutment portions 391, 392 that abut against a pair of corners 113, 114 on the negative side in the X-axis direction within the opening 111. The abutment portions 391, 392 are inclined with respect to a pair of edges forming the corners 113, 114 of the opening 111. For example, the corner 113 is composed of an edge 115 that is one of the first inner wall surfaces 118 of the opening 111 and an edge 116 that is one of the second inner wall surfaces 119 of the opening 111. The abutment portion 391 is inclined with respect to the edge 115 at an angle α, and is inclined with respect to the edge 116 at an angle β.

[0046] Further, an intermediate portion between both end portions of the end plate 39 is a non-contact portion 393 that does not contact the first inner wall surface 118 of the opening 111. In this embodiment, the entire region between both end faces of the end plate 39 in the Y-axis direction is the non-contact portion 393.

[0047] As described above, end plate 39 has a uniform shape over the entire length in the Z-axis direction, and the upper end of end plate 39 is disposed below thermally welded portion 90. Therefore, non-contact portion 393 does not contact first inner wall surface 118 of opening 111 from a position corresponding to the center of energy storage element 20 in the Z-axis direction to a position corresponding to thermally welded portion 90, as shown in Fig. 3(c).

[0048] Next, the function of the end plate 39 will be described. FIG. 4 is a top view that typically illustrates the internal structure of the main body 11 according to the embodiment. An arrow Y1 in FIG. 4 indicates a pressing force applied from the energy storage element 20 to the end plate 39 when the energy storage element 20 expands. An arrow Y2 in FIG. 4 indicates a pressing force applied from the end plate 39 that has received the pressing force Y1 to the main body 11. That is, when the energy storage element 20 is not expanded, the pressing forces Y1 and Y2 are not generated, and the end plate 39 is not constrained (compressed) in the opening 111. That is, the end plate 39 is not deformed from the state before being accommodated in the main body 11. Note that the end plate 39 may receive an external force from the opening 111 or the energy storage element 20 before expansion immediately after being inserted into the opening 111 together with the multiple energy storage elements 20. This external force is a small force (less than 10%) compared to the pressing force Y1 when the energy storage element 20 expands, and therefore, in this state as well, the end plate 39 is not constrained (compressed).

[0049] The energy storage elements 20 expand as they are charged and discharged. This expansion causes a pressing force Y1 to be applied from the energy storage elements 20 to the end plate 39. Specifically, the energy storage elements 20 expand most at the center of the long side surface 211 of the container 21. Therefore, the pressing force Y1 acts on the center of the end plate 39 in the Y-axis direction. Furthermore, the non-contact portion 393 of the end plate 39 does not contact the first inner wall surface 118 of the opening 111, but the contact portions 391 and 392 contact the corners 113 and 114 of the opening 111. Therefore, a pressing force Y2 is applied from the contact portions 391 and 392 only to the corners 113 and 114.

[0050] Here, a flat end plate is assumed as a comparative example. When the energy storage elements 20 expand, a large pressing force is applied to the center of the flat end plate. Therefore, the center of the first inner wall surface 118 of the opening 111 is most likely to deform due to the pressing force from the center of the flat end plate. This deformation easily causes damage to the heat-sealed portion 90 at a position corresponding to the center of the first inner wall surface 118.

[0051] On the other hand, the corners 113, 114 of the opening 111 are less likely to deform even when subjected to the pressing force Y1 because they have greater rigidity than the central portion of the first inner wall surface 118. In other words, the heat-sealed portion 90 at the positions corresponding to the corners 113, 114 is less likely to be damaged.

[0052] In this embodiment, as described above, abutment portions 391, 392 which are both ends of end plate 39 abut against corners 113, 114 in opening 111, and non-abutment portion 393 which is the middle portion does not abut against first inner wall surface 118 of opening 111. This makes it possible to concentrate the pressing force received by first inner wall surface 118 of opening 111 through end plate 39 on corners 113, 114 and not to act on the center of first inner wall surface 118. Therefore, damage to heat-welded portion 90 can be suppressed.

[0053] [Effects, etc.] As described above, the energy storage device 1 according to the present embodiment includes a plurality of energy storage elements 20 stacked in the X-axis direction (predetermined direction), a pair of end plates 39 arranged at positions sandwiching the plurality of energy storage elements 20 in the X-axis direction, and an exterior body 10 that houses the plurality of energy storage elements 20 and the pair of end plates 39. The exterior body 10 includes a main body 11 (first member) having an opening 111 and in which the plurality of energy storage elements 20 and the end plates 39 are housed, and an outer lid 12 (second member) that is joined to the main body 11 while covering the opening 111. The main body 11 and the outer lid 12 have a heat-sealed portion 90 that is joined to each other along the entire circumference of the opening 111. The opening 111 is formed in a polygonal shape when the opening 111 is viewed in a plan view. Of the pair of end plates 39, at least one end plate 39 has two end ends which, when viewed in a plane through the opening 111, abutment portions 391, 392 abut against corners 113, 114 within the opening 111, and an intermediate portion between the two end ends which is a non-abutment portion 393 that does not abut against the first inner wall surface 118 of the opening 111.

[0054] According to this, abutment portions 391, 392 which are both ends of end plate 39 abut against corners 113, 114 in opening 111, and non-abutment portion 393 which is the middle portion does not abut against first inner wall surface 118 of opening 111. This makes it possible to concentrate the pressing force received by first inner wall surface 118 of opening 111 through end plate 39 on corners 113, 114 and not to act on the center of first inner wall surface 118. Therefore, damage to heat-welded portion 90 can be suppressed.

[0055] Further, the contact portions 391 and 392 are inclined with respect to a pair of edges forming the corners 113 and 114 of the opening 111 .

[0056] According to this, since the abutment portions 391, 392 of the end plate 39 are inclined with respect to a pair of edges forming the corners 113, 114, when the end plate 39 receives the pressing force Y1, the end plate 39 can be pressed against the pair of second inner wall surfaces 119 of the opening 111. This makes it difficult for the end plate 39 to deform, and can prevent the non-abutment portion 393 from abutting against the first inner wall surface 118 of the opening 111, in the unlikely event that the non-abutment portion 393 comes into contact with the first inner wall surface 118 of the opening 111. Therefore, damage to the heat-sealed portion 90 can be more reliably prevented.

[0057] Further, the end plate 39 has a curved shape when the opening 111 is seen in a plan view.

[0058] According to this, since the end plate 39 has a curved shape, the end plate 39 itself can exert an elastic force. Therefore, when the plurality of energy storage elements 20 expand, the end plate 39 rebounds, and a restraining force can be applied to the plurality of energy storage elements 20. Therefore, deformation of the end plate 39 itself can be suppressed, and the pressing force Y2 acting on the first inner wall surface 118 of the opening 111 can also be suppressed. This makes it possible to more reliably suppress damage to the thermally welded portion 90.

[0059] Further, non-contact portion 393 does not contact first inner wall surface 118 of opening 111 from a position corresponding to the center of energy storage element 20 to a position corresponding to thermally welded portion 90 in the Z-axis direction (insertion direction).

[0060] According to this, non-contact portion 393 does not contact first inner wall surface 118 of opening 111 from a position corresponding to the center of energy storage element 20 to a position corresponding to thermally welded portion 90. This cuts off the direct force transmission path from the portion (center) of expanded energy storage element 20 where the pressing force is greatest to thermally welded portion 90. This makes it difficult for force caused by the expansion of energy storage element 20 to act on thermally welded portion 90, making it possible to more reliably suppress damage to thermally welded portion 90.

[0061] Furthermore, end plate 39 is not restrained within opening 111 when multiple energy storage elements 20 are not expanded.

[0062] Here, when the end plate 39 is restrained together with the multiple energy storage elements 20 via, for example, another restraining member, even if the multiple energy storage elements 20 expand, the deformation of the end plate 39 is suppressed by the restraining force from the restraining member. On the other hand, if the end plate 39 is not restrained within the opening 111, it is likely to be deformed by the pressing force Y1 received by the expansion of the multiple energy storage elements 20. In other words, damage to the thermally welded portion 90 is likely to be induced. The configuration of the present disclosure is suitable for such an unrestrained end plate 39.

[0063] [Variation 1] In the above embodiment, the case where both end faces in the Y-axis direction of the end plate 39 face a pair of second inner wall surfaces 119 is exemplified. In this modified example 1, the case where both end faces in the Y-axis direction of the end plate 39 abut against the first inner wall surface 118 will be described. FIG. 5 is an explanatory diagram showing a schematic configuration of an end plate 39a according to modified example 1. FIG. 5 is a diagram corresponding to FIG. 3. Specifically, FIG. 5(a) is a top view of the end plate 39a, FIG. 5(b) is a plan view of the end plate 39a, and FIG. 5(c) is a cross-sectional view of the end plate 39a. FIG. 5(c) is a cross-sectional view of a cut surface including the VC-VC line in FIG. 5(a) and FIG. 5(b). In the following description, the same reference numerals may be used for the same parts as those in the above embodiment, and the description thereof may be omitted.

[0064] As shown in FIG. 5, the end plate 39a is curved such that the central portion protrudes toward the positive side in the X-axis direction, that is, toward the energy storage element 20, when viewed from above. The end plate 39a has a uniform shape over the entire length in the Z-axis direction. Both end portions of the end plate 39a in the Y-axis direction are disposed on the negative side in the X-axis direction relative to the central portion. Both end faces of the end plate 39a in the Y-axis direction are in surface contact with the first inner wall surface 118 of the opening 111. Note that it is sufficient that both end faces abut against the first inner wall surface 118 when the energy storage element 20 expands, and they do not have to abut against the first inner wall surface 118 before the energy storage element 20 expands.

[0065] Both ends of end plate 39a in the Y-axis direction are abutting portions 391a, 392a that abut against a pair of corners 113, 114 on the negative side in the X-axis direction within opening 111. The abutting portions 391a, 392a are inclined with respect to a pair of edges that form corners 113, 114 of opening 111. In addition, an intermediate portion between both ends of end plate 39a is a non-abutting portion 393a that does not abut against first inner wall surface 118 of opening 111.

[0066] With such an end plate 39a, it is possible to achieve the same effects as those of the above embodiment.

[0067] Here, when end plate 39a receives a pressing force from expanded energy storage elements 20, both end faces in the Y-axis direction of end plate 39a apply the pressing force to first inner wall surface 118. Since both end faces are in surface contact with first inner wall surface 118, the pressing force is dispersed. This makes it possible to weaken the pressing force applied to corners 113, 114, and to suppress damage to corners 113, 114.

[0068] [Variation 2] In the above embodiment, the case has been described where the entire end plate 39 is curved such that the central portion of end plate 39 in the Y axis direction is convex toward energy storage element 20. In this modification 2, a case will be described where both end portions in the Y axis direction of end plate 39b are bent.

[0069] Fig. 6 is an explanatory diagram showing a schematic configuration of an end plate 39b according to Modification 2. Fig. 6 is a diagram corresponding to Fig. 3. Specifically, Fig. 6(a) is a top view of the end plate 39b, Fig. 6(b) is a plan view of the end plate 39b, and Fig. 6(c) is a cross-sectional view of the end plate 39b. Fig. 6(c) is a cross-sectional view of a cut surface including the VIC-VIC line in Fig. 6(a) and Fig. 6(b). In the following description, the same reference numerals may be used to designate the same parts as those in the above embodiment, and the description thereof may be omitted.

[0070] As shown in Fig. 6, the end plate 39b includes a flat plate portion 395b and a pair of protruding portions 396b, 397b protruding from both ends of the flat plate portion 395b in the Y-axis direction so as to bend toward the first inner wall surface 118. Each of the protruding portions 396b, 397b is bent so as to be perpendicular to the flat plate portion 395b. Each of the protruding portions 396b, 397b is an example of an abutting portion that abuts against the corners 113, 114 of the opening 111. Specifically, the tip surface of each of the protruding portions 396b, 397b is in surface contact with the first inner wall surface 118, and the outer surface of each of the protruding portions 396b, 397b is in surface contact with the second inner wall surface 119. Furthermore, the tip surface and outer surface of each protrusion 396b, 397b need only abut against the first inner wall surface 118 and the second inner wall surface 119 when the storage element 20 expands, and do not need to abut against the first inner wall surface 118 and the second inner wall surface 119 before the storage element 20 expands.

[0071] A flat portion 395b (middle portion) between a pair of protruding portions 396b, 397b of the end plate 39b is an example of a non-contact portion that does not contact the first inner wall surface 118 of the opening 111.

[0072] With this type of end plate 39b, it is possible to achieve the same effects as those of the above embodiment.

[0073] Here, when end plate 39b receives a pressing force from expanded energy storage element 20, the tip faces of protrusions 396b, 397b of end plate 39b apply the pressing force to first inner wall surface 118. Since the tip faces are in surface contact with first inner wall surface 118, the pressing force is dispersed. This makes it possible to weaken the pressing force applied to corners 113, 114, and to suppress damage to corners 113, 114.

[0074] [Variation 3] In the above-described modified example 2, a case was illustrated in which a pair of protrusions 396b, 397b of end plate 39b are bent so as to be perpendicular to flat plate portion 395b. In this modified example 3, a case in which both ends in the Y-axis direction of end plate 39 are bent will be described. Fig. 6 illustrates a case in which a pair of protrusions 396c, 397c of end plate 39c according to modified example 2 are bent so as to be inclined with respect to flat plate portion 395c.

[0075] Fig. 7 is an explanatory diagram showing a schematic configuration of an end plate 39c according to Modification 3. Fig. 7 is a diagram corresponding to Fig. 6. Specifically, Fig. 7(a) is a top view of the end plate 39c, Fig. 7(b) is a plan view of the end plate 39c, and Fig. 7(c) is a cross-sectional view of the end plate 39c. Fig. 7(c) is a cross-sectional view of a cut surface including line VIIC-VIIC in Fig. 7(a) and Fig. 7(b). In the following description, the same parts as those in the above embodiment are denoted by the same reference numerals, and description thereof may be omitted.

[0076] As shown in FIG. 7, the end plate 39c includes a flat plate portion 395c and a pair of protruding portions 396c, 397c that protrude from both ends of the flat plate portion 395c in the Y-axis direction so as to bend toward the first inner wall surface 118. The protruding portions 396c, 397c are bent with respect to the flat plate portion 395c at an inclination such that the distance between them increases toward the tip. The protruding portions 396c, 397c are an example of abutting portions that abut against the corners 113, 114 of the opening 111. Specifically, the tip surfaces of the protruding portions 396c, 397c are in surface contact with the first inner wall surface 118, and the outer surfaces of the protruding portions 396c, 397c are inclined with respect to the second inner wall surface 119 and do not contact it. In addition, the tip surfaces of each protrusion 396c, 397c need only abut against the first inner wall surface 118 when the storage element 20 expands, and do not need to abut against the first inner wall surface 118 before the storage element 20 expands.

[0077] A flat portion 395c (middle portion) between a pair of protruding portions 396c, 397c of the end plate 39c is an example of a non-contact portion that does not contact the first inner wall surface 118 of the opening 111.

[0078] With this type of end plate 39c as well, it is possible to achieve the same effects as those of the second modified example.

[0079] [Variation 4] In the above embodiment, the case has been described in which the non-contact portion 393 is formed by curving the entire end plate 39 so that the central portion of the end plate 39 in the Y-axis direction is convex toward the energy storage element 20. In this fourth modification, a case will be described in which a slit portion 390d is provided in end plate 39d to form the non-contact portion.

[0080] Fig. 8 is an explanatory diagram showing a schematic configuration of an end plate 39d according to Modification 4. Fig. 8 is a diagram corresponding to Fig. 3. Specifically, Fig. 8(a) is a top view of the end plate 39d, Fig. 8(b) is a plan view of the end plate 39d, and Fig. 8(c) is a cross-sectional view of the end plate 39d. Fig. 8(c) is a cross-sectional view of a cut surface including line VIIIC-VIIIC in Figs. 8(a) and 8(b). In the following description, the same reference numerals may be used to refer to the same parts as those in the above embodiment, and the description thereof may be omitted.

[0081] 8, the end plate 39d is generally flat, and a slit portion 390d is formed at the upper end of the center portion in the Y-axis direction. The slit portion 390d is an opening that is rectangular in plan view and open at the top. The lower end of the slit portion 390d is disposed below the center portion of the energy storage element 20. That is, the slit portion 390d does not abut against the first inner wall surface 118 of the opening 111 from the position corresponding to the center portion of the energy storage element 20 to the position corresponding to the thermally welded portion 90 in the Z-axis direction (insertion direction). Thus, the slit portion 390d is an example of a portion that does not abut against the first inner wall surface 118 of the opening 111.

[0082] Furthermore, both ends of end plate 39d in the Y-axis direction are contact portions 391d, 392d that contact corners 113, 114 of opening 111. Specifically, it is sufficient that contact portions 391d, 392d contact first inner wall surface 118 when energy storage element 20 expands, and they do not need to contact first inner wall surface 118 before energy storage element 20 expands.

[0083] With such an end plate 39d, it is possible to achieve the same effects as those of the above embodiment.

[0084] Furthermore, the end plate 39d is provided with the slit portion 390d, so that the end plate 39d itself is light in weight. Therefore, the weight of the electricity storage device 1 can be reduced.

[0085] [Variation 5] In the above embodiment, the end plate 39 has a uniform shape along its entire length in the Z-axis direction. In this modification 5, an end plate 39e that does not have a uniform shape along its entire length in the Z-axis direction will be described.

[0086] Fig. 9 is an explanatory diagram showing a schematic configuration of an end plate 39e according to Modification 5. Fig. 9 is a diagram corresponding to Fig. 3. Specifically, Fig. 9(a) is a top view of the end plate 39e, Fig. 9(b) is a plan view of the end plate 39e, and Fig. 9(c) is a cross-sectional view of the end plate 39e. Fig. 9(c) is a cross-sectional view of a cut surface including line IXC-IXC in Fig. 9(a) and Fig. 9(b). In the following description, the same reference numerals may be used to refer to the same parts as those in the above embodiment, and the description thereof may be omitted.

[0087] 9, the lower end of end plate 39e is formed in a flat plate shape, and the entire end plate 39e abuts against first inner wall surface 118 of opening 111. The upper end of end plate 39e is curved such that the central portion in the Y axis direction protrudes toward the positive side in the X axis direction, that is, toward energy storage element 20. Here, both ends of end plate 39e in the Y axis direction are abutment portions 391e, 392e that abut against a pair of corners 113, 114 in opening 111. The abutment portions 391e, 392e abut against the respective corners 113, 114 over the entire length in the Z axis direction.

[0088] The shape of end plate 39e from the lower end to the upper end is a smooth curved plate shape that gradually curves from the lower end to the upper end. Due to this shape, an intermediate portion between both ends of end plate 39e and a portion above the lower end of end plate 39e becomes non-contact portion 393e that does not contact first inner wall surface 118. Even in this case, non-contact portion 393e does not contact first inner wall surface 118 of opening 111 from a position corresponding to the center of energy storage element 20 in the Z-axis direction to a position corresponding to thermally welded portion 90, as shown in FIG. 9(c).

[0089] With this type of end plate 39e, it is possible to achieve the same effects as those of the above embodiment.

[0090] [others] Although the embodiment of the present invention and the modified example thereof have been described above, the present invention is not limited to the above embodiment and modified example. In other words, the embodiment and modified example disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0091] For example, in the above embodiment and its modified examples, the opening 111 has a rectangular shape in a plan view, but the opening may have another polygonal shape. In that case, the opening preferably has a pair of first inner wall surfaces that face each other in the arrangement direction (X-axis direction) of the multiple energy storage elements.

[0092] In addition, in the above embodiment and its modified examples, the upper end of end plate 39 is disposed below heat-sealed portion 90, but the upper end of the end plate may be disposed at the same position as or above heat-sealed portion 90. Even in this case, it is desirable that the non-contact portion of the end plate does not contact first inner wall surface 118 from the position corresponding to the center of energy storage element 20 to the position corresponding to heat-sealed portion 90 in the Z-axis direction.

[0093] Furthermore, configurations constructed by arbitrarily combining the components included in the above-described embodiments and their modifications are also included within the scope of the present invention. [Industrial Applicability]

[0094] The present invention can be applied to an electricity storage device including an electricity storage element such as a lithium ion secondary battery. [Explanation of symbols]

[0095] 1. Energy storage device 10 Exterior body 11 Main body 12 Outer lid 17 Busbar plate 17a Busbar opening 20 Energy storage element 21 Container 33 Busbar 39, 39a, 39b, 39c, 39d, 39e End plates 50 wall 80 Connection Unit 90 Heat welded part 91, 92 External terminals 111 Opening 113, 114 Corner 115, 116 Margin 118 First inner wall surface 119 Second inner wall surface 123 Skirt portion 124 Joint portion 211 Long side surface 212 Short side surface 221 Positive terminal 222 Negative terminal 390d Slit portion 391 Contact portion 391, 391a, 391d, 391e, 392, 392a, 392d, 392e Contact portion 393, 393a, 393e Non-contact portion 395b, 395c Flat portion (non-contact portion) 396b, 396c, 397b, 397c Protruding portion (contact portion) Y1, Y2 Pressing force α, β Angle

Claims

1. A storage element; An end plate arranged next to the energy storage element; an exterior body that houses the energy storage element and the end plate, The exterior body is a first member having an opening, the energy storage element and the end plate being accommodated in the opening; a second member joined to the first member in a state in which the opening is covered, the first member and the second member have a heat-welded portion joined to each other along an entire periphery of the opening, the first member has a first wall portion at a position where the end plate is sandwiched between the first member and the energy storage element, A central portion of the end plate protrudes toward the energy storage element, Both end portions of the end plate are located closer to the first wall portion than the central portion of the end plate, A space is formed between a center portion of the end plate and the first wall portion, the exterior body has a corner portion constituted by the first wall portion and a second wall portion arranged in a direction intersecting the first wall portion, The two ends of the end plate contact the corners. Energy storage device.

2. The end plate has a curved shape. The power storage device according to claim 1 .

3. The end plate does not contact the heat-sealed portion. The power storage device according to claim 1 or 2.

4. The end plate is not constrained within the exterior housing when the energy storage element is not expanded. The power storage device according to any one of claims 1 to 3.

Images