JP7655359B2 - Power storage device - Google Patents

Description

The present invention relates to an energy storage device that includes an energy storage element, an end plate, and an exterior body.

Conventionally, there is known an energy storage device in which a pair of divided exterior bodies house multiple energy storage elements, such as lithium ion batteries, and the connecting surfaces of the pair of exterior bodies are heat-welded together. In such an energy storage device, a pair of flat end plates arranged in positions that sandwich the multiple energy storage elements are also housed within the exterior body (see, for example, Patent Document 1).

JP 2019-79599 A

Energy storage elements have the property of gradually expanding as they are charged and discharged. Therefore, as the expansion of multiple energy storage elements progresses, the outermost energy storage element presses against the inner surface of the exterior body via the end plate. This increases the stress acting on the heat-sealed parts of the exterior body, which may damage the heat-sealed parts.

The present invention aims to provide an energy storage device that can suppress damage to the heat-welded parts of the exterior body caused by the expansion of the energy storage element.

To achieve the above object, an energy storage device according to one aspect of the present invention comprises an energy storage element, an end plate arranged alongside the energy storage element, and an exterior housing that houses the energy storage element and the end plate, the exterior housing having a first wall portion at a position where the end plate is sandwiched between the energy storage element and the exterior housing, the first wall portion including a joint portion that joins the first wall portion to a portion of the exterior housing other than the first wall portion, a central portion of the end plate protruding towards the energy storage element, an end portion of the end plate being located closer to the first wall portion than the central portion of the end plate, and a space being formed between the central portion of the end plate and the first wall portion.

Here, when the multiple energy storage elements expand, the center of one of the inner wall surfaces of the opening in the first member is most likely to deform due to the pressure 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 opening are more rigid than the center of the inner wall surface, and are therefore less likely to deform even when subjected to pressure. In other words, the heat-sealed portion at a position corresponding to the corner is less likely to be damaged.

In this embodiment, the abutting portions at both ends of the end plate abut the corners inside the opening, and the non-abutting portion at the middle does not abut against 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 act on the center of the inner wall surface. This makes it possible to suppress damage to the heat-sealed portion of the exterior body.

The abutment portion may be inclined with respect to a pair of edges that form the corners of the opening.

With this, the abutment portion of the end plate is inclined with respect to a pair of edges forming a corner, so that when the end plate is subjected to a pressing force, the end plate can be pushed against the inner wall surface. This makes the end plate less likely to deform, and in the unlikely event that the non-abutment portion comes into contact with the inner wall surface, it is possible to more reliably prevent damage to the heat-sealed portion of the exterior body.

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

With 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.

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

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 location where the pressing force is greatest can be avoided. This makes it difficult for the end plate itself to deform, and therefore 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.

The end plate does not need to be restrained within the opening when the multiple energy storage elements are not expanded.

When the end plate is restrained together with multiple energy storage elements, for example, via 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.

The energy storage device of the present invention can suppress damage to the heat-sealed parts of the exterior body caused by the expansion of the energy storage element.

1 is a perspective view showing an external appearance of a power storage device according to an embodiment; FIG. 2 is an exploded perspective view showing each component of the electricity storage device according to the embodiment. FIG. 4 is an explanatory diagram showing a schematic configuration of an end plate according to the embodiment. FIG. 2 is a top view showing a schematic internal structure of a main body according to the embodiment. 10A and 10B are explanatory diagrams showing a schematic configuration of an end plate according to Modification 1. 13 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 2. FIG. 13 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 3. FIG. 13 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 4. FIG. 13 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 5. FIG.

The following describes 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 modified examples 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 modified examples are merely examples and are not intended to limit the present invention. Also, the dimensions and the like are not strictly shown in each figure.

In the following description and drawings, the X-axis direction is defined as the arrangement direction of the storage elements, the opposing direction of the long side of the container of the 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 in one storage element, or the opposing direction of the short side of the container of the 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 storage device, or the up-down direction. The Z-axis direction is also the insertion direction when inserting multiple 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 usage mode, it is possible that the Z-axis direction is not the up-down direction, but for convenience of explanation, the Z-axis direction will be described as the up-down direction below. In addition, 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 relative directions or attitudes, such as parallel and perpendicular, also include cases where the directions or attitudes are not strictly those. For example, saying that two directions are perpendicular does not only mean that the two directions are completely perpendicular, but also means that the directions are substantially perpendicular, that is, that there is a difference of, for example, about a few percent.

[General Description of 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 of the power storage device 1 according to the embodiment when disassembled.

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

As shown in Figures 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 part of the bus bar plate 17.

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 and the bus bar plate 17, etc., in predetermined positions and protects these elements from impacts, etc.

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 when viewed from above. A wall 50 is provided at the upper end of the main body 11, continuously surrounding the entire circumference 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 contains multiple bus bars 33 held by the bus bar plate 17, a connection unit 80 including a control circuit, etc., and a pair of end plates 39.

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 while covering the opening 111 of the main body 11. 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 storage elements 20 via the connection unit 80 and the bus bar 33, and the 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 contains the storage elements 20, etc.

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 metals with insulating coating. This prevents the 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 storage element 20 and the like is maintained.

The storage element 20 is a secondary battery (single cell) that can charge and discharge electricity, and more specifically, is a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. The storage element 20 has a flat rectangular parallelepiped shape (square shape), and in this embodiment, eight storage elements 20 are arranged in the X-axis direction. The shape of the storage element 20 and the number of storage elements 20 arranged are not limited. In addition, the 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 can use stored electricity without the user having to charge it.

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 sides 211 and a pair of short sides 212 adjacent to the pair of long sides 211. The pair of long sides 211 face each other in the X-axis direction, and the pair of short sides 212 face each other in the Y-axis direction. Each of the multiple energy storage elements 20 is stacked such that the long sides 211 of the containers 21 face each other, and is housed within the main body 11.

The lid of the container 21 is provided with a metallic positive terminal 221 and a negative terminal 222. An insulating member (not shown) is interposed between the lid and the positive and negative terminals 221 and 222, and the insulating member insulates the lid from the positive and negative terminals 221 and 222.

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, i.e., 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 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 and a gas exhaust valve for releasing pressure by discharging gas when the pressure inside the container 21 increases. In addition, inside the container 21, an electrode body (also called an electricity storage element or a power generation element) and a current collector (a positive electrode current collector and a negative electrode current collector) are arranged, and an electrolyte (non-aqueous electrolyte) is sealed in, but a detailed description will be omitted.

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

The connection unit 80 is a unit having multiple bus bars and a control board, 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 multiple electrical components, and these multiple electrical components form a detection circuit that detects the state of each energy storage element 20, a control circuit that controls charging and discharging, and the like. 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 the charging and discharging of each energy storage element 20.

The busbar plate 17 is an example of a holding member arranged above the multiple energy storage elements 20 (the side where the positive electrode terminal 221 and the negative electrode terminal 222 are arranged), and in this embodiment, it is a member that holds the busbar 33. More specifically, the busbar plate 17 is a member that holds the multiple busbars 33, the connection unit 80, and other wiring (not shown) and can regulate the positions of these members. The busbar plate 17 also has 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. The busbar plate 17 is fixed to the main body 11, and therefore also has the role of regulating the movement of the multiple energy storage elements 20 upward (to the positive side in the Z-axis direction), for example.

The bus bar plate 17 arranged above the multiple energy storage elements 20 may also be called, for example, a "bus bar frame" or an "inner lid." The 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.

The pair of end plates 39 are rectangular plates arranged in the main body 11 at positions that sandwich the multiple energy storage elements 20 together. Specifically, the pair of end plates 39 are arranged in a position that sandwiches the multiple energy storage elements 20 in the X-axis direction in a posture parallel to the YZ plane. In other words, the pair of end plates 39 are arranged so as to overlap the long side surface 211 of the container 21 of the energy storage element 20 arranged on the outermost side. The end plates 39 are formed of 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. Details of the end plates 39 will be described later.

[Joint structure between main body and outer lid]
Next, a description will be given of the joining structure between the main body 11 and the outer lid 12. 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.

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

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 adhesives is not considered to be thermal welding. Even when adhesive is used to join the members to be joined, they melt and re-harden, but if the joint is analyzed after hardening, the adhesive remains at that location. Therefore, even after joining, it is possible to determine whether the joint was made by thermal welding or adhesive.

During heat 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 mix together. After a certain period of time has passed in a non-heated state, the mixed parts harden and are integrated and joined. This joint part is the heat-sealed part 90 (see (c) in FIG. 3). The heat-sealed 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 heat-sealed part 90 joined along the entire circumference of the opening 111. In addition, in FIG. 3(c), the interface between the tip (lower end) of the joint 124 and the tip (upper end) of the wall 50 is shown with respect to the heat-sealed portion 90, but in reality, the two are mixed together and hardened, so there is no interface. This heat-sealed portion 90 seals the main body 11 and the outer lid 12 all around, ensuring airtightness.

[End plate]
Next, the details of the end plate 39 will be described. 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).

Here, the pair of end plates 39 have different postures but the same shape. Specifically, the end plate 39 arranged on the negative side of the X axis direction has a posture in which the center portion protrudes toward the positive side of the X axis direction, and the end plate 39 arranged on the positive side of the X axis direction has a posture in which the center portion protrudes toward the negative side of the X axis direction. For this reason, in this embodiment, the details of the end plate 39 arranged on the negative side of the X axis direction will be described, and the details of the end plate 39 arranged on the positive side of the X axis direction will be omitted. In addition, in the following description, within 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.

As shown in FIG. 3, the end plate 39 is a curved plate having a rectangular shape in a plan view. The end plate 39 is accommodated in the opening 111 and is interposed between the energy storage element 20 arranged on the most negative side in the X-axis direction and the first inner wall surface 118 of the opening 111. The upper end of the end plate 39 is located below the upper end of the main body 11, i.e., below the heat-sealed portion 90.

The end plate 39 is curved so that the center portion protrudes toward the positive side in the X-axis direction when viewed from above, that is, toward the energy storage element 20. The end plate 39 has a uniform shape over its entire length in the Z-axis direction. Both ends of the end plate 39 are located on the negative side in the X-axis direction relative to the center portion. Both end faces of the end plate 39 in the Y-axis direction face a pair of second inner wall surfaces 119 of the opening 111. Note that both end faces of the end plate 39 in the Y-axis direction may abut against the pair of second inner wall surfaces 119.

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 of the X-axis direction within the opening 111. The abutment portions 391, 392 are inclined with respect to a pair of edges that form 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 at an angle α with respect to the edge 115, and is inclined at an angle β with respect to the edge 116.

The intermediate portion between both ends 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 area between both end faces of the end plate 39 in the Y-axis direction is the non-contact portion 393.

As described above, the end plate 39 has a uniform shape over its entire length in the Z-axis direction, and the upper end of the end plate 39 is located below the heat-sealed portion 90. Therefore, as shown in FIG. 3C, the non-contact portion 393 does not contact the first inner wall surface 118 of the opening 111 from the position corresponding to the center of the energy storage element 20 in the Z-axis direction to the position corresponding to the heat-sealed portion 90.

Next, the function of the end plate 39 will be described. FIG. 4 is a top view showing a schematic internal structure of the main body 11 according to the embodiment. The arrow Y1 in FIG. 4 indicates the pressing force applied from the energy storage element 20 to the end plate 39 when the energy storage element 20 expands. The arrow Y2 in FIG. 4 indicates the pressing force applied from the end plate 39 that has received the pressing force Y1 to the main body 11. In other words, 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. In other words, the end plate 39 is not deformed from the state before being accommodated in the main body 11. In addition, immediately after the end plate 39 is inserted into the opening 111 together with the multiple energy storage elements 20, it may receive an external force from the opening 111 or the energy storage element 20 before expansion. This external force is a small force (less than 10%) compared to the pressing force Y1 when the energy storage element 20 expands, so the end plate 39 is not constrained (compressed) in this state either.

The multiple energy storage elements 20 expand as they are charged and discharged. This expansion causes the energy storage elements 20 to apply a pressing force Y1 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. In addition, 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, the pressing force Y2 is applied only from the contact portions 391 and 392 to the corners 113 and 114.

Here, a flat end plate is considered as a comparative example. When the multiple energy storage elements 20 expand, a large pressing force is applied to the center of the flat end plate. For this reason, 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.

On the other hand, the corners 113 and 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 center of the first inner wall surface 118. In other words, the heat-sealed portion 90 at the positions corresponding to the corners 113 and 114 is less likely to be damaged.

In this embodiment, as described above, the abutment portions 391, 392, which are both ends of the end plate 39, abut against the corners 113, 114 in the opening 111, and the non-abutment portion 393, which is the middle portion, does not abut against the first inner wall surface 118 of the opening 111. This allows the pressing force that the first inner wall surface 118 of the opening 111 receives through the end plate 39 to be concentrated on the corners 113, 114, and not to act on the center of the first inner wall surface 118. Therefore, damage to the heat-sealed portion 90 can be suppressed.

[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 in the opening 111, 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 abutment portions 391, 392 at both ends that abut against corners 113, 114 within the opening 111 when the opening 111 is viewed in a plane, and an intermediate portion between the two ends is a non-abutment portion 393 that does not abut against the first inner wall surface 118 of the opening 111.

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

In addition, the abutment portions 391, 392 are inclined with respect to a pair of edges that form the corners 113, 114 of the opening 111.

As a result, the abutment portions 391, 392 of the end plate 39 are inclined relative to a pair of edges forming the corners 113, 114, so that when the end plate 39 receives a pressing force Y1, the end plate 39 can be pressed against a pair of second inner wall surfaces 119 of the opening 111. This makes it difficult for the end plate 39 to deform, and prevents the non-abutment portion 393 from abutting against the first inner wall surface 118 of the opening 111, in the unlikely event that this occurs. Therefore, damage to the heat-sealed portion 90 can be more reliably prevented.

In addition, the end plate 39 has a curved shape when viewed in plan of the opening 111.

As a result, since the end plate 39 has a curved shape, the end plate 39 itself can exert an elastic force. Therefore, when the multiple energy storage elements 20 expand, the end plate 39 rebounds, and a restraining force can be applied to the multiple 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 heat-sealed portion 90.

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

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

In addition, the end plate 39 is not constrained within the opening 111 when the multiple storage elements 20 are not expanded.

Here, if the end plate 39 is restrained together with the multiple energy storage elements 20, for example, via another restraining member, the restraining force from the restraining member suppresses deformation of the end plate 39 even if the multiple energy storage elements 20 expand. 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, it is likely to induce damage to the thermally welded portion 90. The configuration of the present disclosure is suitable for such an unrestrained end plate 39.

[Modification 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.

As shown in FIG. 5, the end plate 39a is curved so 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 its entire length in the Z-axis direction. Both end portions of the end plate 39a in the Y-axis direction are located 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.

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

This type of end plate 39a can achieve the same effects as the above embodiment.

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

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

Figure 6 is an explanatory diagram showing the schematic configuration of end plate 39b according to modified example 2. Figure 6 is a diagram corresponding to Figure 3. Specifically, Figure 6(a) is a top view of end plate 39b, Figure 6(b) is a plan view of end plate 39b, and Figure 6(c) is a cross-sectional view of end plate 39b. Figure 6(c) is a cross-sectional view of a cut surface including line VIC-VIC in Figures 6(a) and 6(b). Note that in the following description, parts that are the same as those in the above embodiment may be given the same reference numerals and their description may be omitted.

6, the end plate 39b includes a flat plate portion 395b and a pair of protrusions 396b, 397b that protrude 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 protrusions 396b, 397b is bent so as to be perpendicular to the flat plate portion 395b. Each of the protrusions 396b, 397b is an example of an abutment portion that abuts against the corners 113, 114 of the opening 111. Specifically, the tip surface of each of the protrusions 396b, 397b is in surface contact with the first inner wall surface 118, and the outer surface of each of the protrusions 396b, 397b is in surface contact with the second inner wall surface 119. The tip surface and outer surface of each protrusion 396b, 397b need only contact the first inner wall surface 118 and the second inner wall surface 119 when the energy storage element 20 expands, and do not need to contact the first inner wall surface 118 and the second inner wall surface 119 before the energy storage element 20 expands.

The flat portion 395b (middle portion) between the pair of protrusions 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.

This type of end plate 39b can achieve the same effects as the above embodiment.

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

[Modification 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.

Figure 7 is an explanatory diagram showing the schematic configuration of end plate 39c according to modified example 3. Figure 7 is a diagram corresponding to Figure 6. Specifically, Figure 7(a) is a top view of end plate 39c, Figure 7(b) is a plan view of end plate 39c, and Figure 7(c) is a cross-sectional view of end plate 39c. Figure 7(c) is a cross-sectional view of a cut surface including line VIIC-VIIC in Figures 7(a) and 7(b). Note that in the following description, parts that are the same as those in the above embodiment may be given the same reference numerals and their description may be omitted.

7, the end plate 39c includes a flat plate portion 395c and a pair of protrusions 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. Each of the protrusions 396c, 397c bends with respect to the flat plate portion 395c at an inclination such that the distance between them increases toward the tip. Each of the protrusions 396c, 397c is an example of an abutment portion that abuts against the corners 113, 114 of the opening 111. Specifically, the tip surface of each of the protrusions 396c, 397c is in surface contact with the first inner wall surface 118, and the outer surface of each of the protrusions 396c, 397c is inclined with respect to the second inner wall surface 119 and does not contact it. The tip surface of each protrusion 396c, 397c only needs to abut against the first inner wall surface 118 when the energy storage element 20 expands, and does not need to abut against the first inner wall surface 118 before the energy storage element 20 expands.

The flat portion 395c (middle portion) between the 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.

This type of end plate 39c can also achieve the same effects as those of variant 2 above.

[Modification 4]
In the above embodiment, 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 modification 4, a case will be described in which a slit portion 390d is provided in the end plate 39d to form the non-contact portion.

Figure 8 is an explanatory diagram showing the schematic configuration of end plate 39d according to variant 4. Figure 8 is a diagram corresponding to Figure 3. Specifically, Figure 8(a) is a top view of end plate 39d, Figure 8(b) is a plan view of end plate 39d, and Figure 8(c) is a cross-sectional view of end plate 39d. Figure 8(c) is a cross-sectional view of a cut surface including line VIIIC-VIIIC in Figures 8(a) and 8(b). Note that in the following description, parts that are the same as those in the above embodiment may be given the same reference numerals and their description may be omitted.

As shown in FIG. 8, the end plate 39d is generally flat, and a slit portion 390d is formed at the upper end of the center in the Y-axis direction. The slit portion 390d is a rectangular opening in a plan view that is open at the top. The lower end of the slit portion 390d is located below the center of the energy storage element 20. In other words, the slit portion 390d does not abut against the first inner wall surface 118 of the opening 111 in the Z-axis direction (insertion direction) from the position corresponding to the center of the energy storage element 20 to the position corresponding to the heat-sealed portion 90. In this way, the slit portion 390d is an example of a non-abutting portion with respect to the first inner wall surface 118 of the opening 111.

In addition, both ends of the end plate 39d in the Y-axis direction are abutment portions 391d, 392d that abut against the corners 113, 114 of the opening 111. Specifically, the abutment portions 391d, 392d only need to abut against the first inner wall surface 118 when the energy storage element 20 expands, and do not need to abut against the first inner wall surface 118 before the energy storage element 20 expands.

This type of end plate 39d can achieve the same effects as the above embodiment.

In addition, the end plate 39d has a slit portion 390d, which reduces the weight of the end plate 39d itself. This makes it possible to reduce the weight of the energy storage device 1.

[Modification 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.

Figure 9 is an explanatory diagram showing the schematic configuration of end plate 39e according to modified example 5. Figure 9 is a diagram corresponding to Figure 3. Specifically, Figure 9(a) is a top view of end plate 39e, Figure 9(b) is a plan view of end plate 39e, and Figure 9(c) is a cross-sectional view of end plate 39e. Figure 9(c) is a cross-sectional view of a cut surface including line IXC-IXC in Figures 9(a) and 9(b). Note that in the following description, parts that are the same as those in the above embodiment may be given the same reference numerals and their description may be omitted.

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

The shape of the 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, the intermediate portion between both ends of the end plate 39e and above the lower end of the end plate 39e becomes a non-contact portion 393e that does not contact the first inner wall surface 118. Even in this case, the non-contact portion 393e does not contact the first inner wall surface 118 of the opening 111 from the position corresponding to the center of the energy storage element 20 in the Z-axis direction to the position corresponding to the heat-sealed portion 90, as shown in FIG. 9(c).

This type of end plate 39e can achieve the same effects as the above embodiment.

[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.

For example, in the above embodiment and its modified example, the opening 111 is rectangular in plan view, but the opening may be 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.

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

In addition, configurations constructed by arbitrarily combining the components included in the above embodiments and their variations are also included within the scope of the present invention.

The present invention can be applied to a storage device equipped with a storage element such as a lithium-ion secondary battery.

1 Energy storage device 10 Exterior body 11 Main body 12 Outer lid 17 Bus bar plate 17a Bus bar opening 20 Energy storage element 21 Container 33 Bus bar 39, 39a, 39b, 39c, 39d, 39e End plate 50 Wall 80 Connection unit 90 Thermal welding portion 91, 92 External terminal 111 Opening 113, 114 Corner 115, 116 Edge 118 First inner wall surface 119 Second inner wall surface 123 Skirt portion 124 Joint 211 Long side 212 Short side 221 Positive electrode terminal 222 Negative electrode terminal 390d Slit portion 391 Abutment portion 391, 391a, 391d, 391e, 392, 392a, 392d, 392e Abutment portion 393, 393a, 393e Non-contact parts 395b, 395c Flat plate parts (non-contact parts)
396b, 396c, 397b, 397c Projection part (contact part)
Y1, Y2 Pressing force α, β Angle

Claims (4)

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

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