JP7371458B2 - Power storage device - Google Patents

Description

The present invention relates to a power storage device including a power storage element, an end plate, and an exterior body.

BACKGROUND ART Conventionally, a power storage device is known in which a plurality of power 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 thermally welded together. In such a power storage device, a pair of flat end plates arranged to sandwich a plurality of power storage elements are also housed within the exterior body (for example, see Patent Document 1).

JP 2019-79599 Publication

A power storage element has a characteristic of gradually expanding as it is charged and discharged. Therefore, as expansion of the plurality of power storage elements progresses, the outermost power storage element presses against the inner surface of the exterior body via the end plate. This increases the stress acting on the thermally welded portion of the exterior body, and there is a risk that the thermally welded portion may be damaged.

An object of the present invention is to provide a power storage device that can suppress damage to a thermally welded portion of an exterior body due to expansion of a power storage element.

In order to achieve the above object, a power storage device according to one embodiment of the present invention includes a plurality of power storage elements stacked in a predetermined direction, and a pair of ends arranged at positions sandwiching the plurality of power storage elements in a predetermined direction. A first member comprising: a plate; and an exterior body housing a plurality of power storage elements and a pair of end plates, the exterior body having an opening, and a first member in which the plurality of power storage elements and the end plate are housed; a second member joined to the first member while covering the opening, the first member and the second member having a heat welded part joined to each other along the entire circumference of the opening. However, the opening has a polygonal shape when viewed from above, and at least one of the pair of end plates has both ends located within the opening when viewed from above. It is a contacting part that comes into contact with the corner of the opening, and an intermediate part between both ends is a non-contacting part that does not come into contact with the inner wall surface of the opening.

Here, when the plurality of power storage elements expand, within the inner wall surface of one of the openings provided in the first member, the central portion thereof is most likely to deform due to the pressing force at the time of expansion. Due to this deformation, the heat welded portion at a position corresponding to the central portion of the inner wall surface is likely to be damaged. On the other hand, the corner portions of the opening have greater rigidity than the center portion of the inner wall surface, and therefore are less likely to deform even if subjected to a pressing force. In other words, the thermally welded portions at the positions corresponding to the corners are less likely to be damaged.

In this aspect, the contact parts, which are both ends of the end plate, contact the corners in the opening, and the non-contact parts, which are the intermediate parts, do not contact the inner wall surface of the opening. Thereby, the pressing force applied to the inner wall surface of the opening via the end plate can be concentrated on the corner and not applied to the center of the inner wall surface. Therefore, damage to the heat-welded portion of the exterior body can be suppressed.

The contact portion may be inclined with respect to a pair of edges forming corners of the opening.

According to this, since the contact portion of the end plate is inclined with respect to the pair of edges forming the corner, when the end plate receives a pressing force, the end plate is stretched against the inner wall surface. be able to. This makes it difficult for the end plate to deform, and it is possible to prevent the non-contacting portion from coming into contact with the inner wall surface. Therefore, damage to the heat-welded portion of the exterior body can be more reliably suppressed.

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

According to this, since the end plate has a curved shape, the end plate itself can exert elastic force. Therefore, when the plurality of power storage elements expand, the end plate will repel, and a restraining force can be applied to the plurality of power 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. Thereby, damage to the heat welded portion of the exterior body can be more reliably suppressed.

The non-contact portion contacts the inner wall surface of the opening from a position corresponding to the center of the power storage element to a position corresponding to the thermal welding part in the insertion direction when multiple power storage elements are inserted into the opening. They don't have to be in contact.

Here, the amount of expansion of the electricity storage element is greatest at the center. In other words, the pressing force is greatest at the center of the power storage element during expansion. Since the non-contacting portion does not contact the inner wall surface of the opening from the position corresponding to the central portion of the power storage element to the position corresponding to the heat welding portion, it is possible to avoid a portion where the pressing force is the largest. Therefore, since the end plate itself becomes difficult to deform, the pressing force acting on the inner wall surface can also be suppressed. Thereby, damage to the heat welded portion of the exterior body can be more reliably suppressed.

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

For example, when the end plate is restrained together with a plurality of power storage elements via another restraint member, even if the plurality of power storage elements expand, the deformation of the end plate is suppressed by the restraint force from the restraint member. . On the other hand, if the end plate is not restrained within the opening, it is likely to be deformed by the pressing force received by the expansion of the plurality of power storage elements. In other words, damage to the heat welded portion of the exterior body is likely to occur. The configuration of the present invention is suitable for such an unrestricted end plate.

According to the power storage device of the present invention, damage to the thermally welded portion of the exterior body due to expansion of the power storage element can be suppressed.

FIG. 1 is a perspective view showing the appearance of a power storage device according to an embodiment. FIG. 2 is an exploded perspective view showing each component when the power storage device according to the embodiment is disassembled. It is an explanatory view showing a schematic structure of an end plate concerning an embodiment. FIG. 3 is a top view schematically showing the internal structure of the main body according to the embodiment. FIG. 7 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 1. FIG. FIG. 7 is an explanatory diagram showing a schematic configuration of an end plate according to a second modification. FIG. 7 is an explanatory diagram showing a schematic configuration of an end plate according to modification 3. FIG. 7 is an explanatory diagram showing a schematic configuration of an end plate according to Modification 4. FIG. FIG. 7 is an explanatory diagram showing a schematic configuration of an end plate according to modification 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, power storage devices according to embodiments of the present invention and modifications thereof will be described with reference to the drawings. Note that the embodiments and modifications thereof described below are comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments and modifications thereof are merely examples, and do not limit the present invention. Further, in each figure, dimensions etc. are not strictly illustrated.

In addition, in the following description and drawings, the direction in which the power storage elements are arranged, the direction in which the power storage elements face the long sides of the container, or the thickness direction of the container is defined as the X-axis direction. Further, the direction in which the electrode terminals in one power storage element are arranged or the direction in which the short sides of the container of the power storage element face each other is defined as the Y-axis direction. Further, the direction in which the main body and the outer cover are lined up in the exterior body of the power storage device, or the up-down direction is defined as the Z-axis direction. The Z-axis direction is also the insertion direction when inserting a plurality of power 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 modifications thereof). Note that depending on the mode of use, the Z-axis direction may not be the vertical direction, but for convenience of explanation, the Z-axis direction will be described as the vertical direction below. Furthermore, in the following description, for example, the plus side in the X-axis direction refers to the side in the direction of the arrow of the X-axis, and the minus side in the X-axis direction refers to the side opposite to the plus side in the X-axis direction. The same applies to the Y-axis direction and the Z-axis direction. Furthermore, expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where the directions or orientations are not strictly speaking. For example, when two directions are orthogonal, it does not only mean that the two directions are completely orthogonal, but also that they are substantially orthogonal, that is, there is a difference of only a few percent, for example. It also means to include.

[General explanation of power storage device]
First, a general description of the power storage device 1 according to the embodiment will be given using FIGS. 1 and 2. FIG. 1 is a perspective view showing the appearance of a power storage device 1 according to an embodiment. FIG. 2 is an exploded perspective view showing each component when power storage device 1 according to the embodiment is disassembled.

Power storage device 1 is a device that can charge electricity from the outside and 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 assembly) used for power storage, power supply, or the like. Specifically, the power storage device 1 is used for driving or starting an engine of a moving object such as a car, a motorcycle, a watercraft, a ship, a snowmobile, an agricultural machine, a construction machine, or a railway vehicle for an electric railway. It is used as a battery etc. Examples of the above-mentioned vehicle include an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a gasoline vehicle. Examples of the above-mentioned railway vehicles for electric railways include electric trains, monorails, and linear motor cars. Furthermore, the power storage device 1 can also be used as a stationary battery or the like used for home use, a generator, or the like.

As shown in FIGS. 1 and 2, the power storage device 1 includes a power storage element 20 and an exterior body 10 that accommodates the plurality of power storage elements 20. The exterior body 10 includes a main body 11 that accommodates a plurality of power storage elements 20, a busbar plate 17 arranged above the plurality of power storage elements 20, and an outer lid 12 that covers the busbar plate 17 above.

Exterior body 10 is a rectangular (box-shaped) container (module case) that constitutes the exterior body of power storage device 1 . That is, the exterior body 10 is a member that fixes the plurality of power storage elements 20, the bus bar plate 17, etc. in a predetermined position, and protects these elements from impact and the like.

The main body portion 11 is an example of a first member having an opening 111. The main body part 11 is a bottomed rectangular cylindrical member with an open upper part, and the open part is an opening part 111. The opening 111 has a substantially rectangular shape in plan view. A wall portion 50 is provided at the upper end of the main body portion 11 and continuously surrounds the opening portion 111 over the entire circumference. Inside the opening 111 of the main body 11, in addition to the plurality of power storage elements 20 and the busbar plate 17, there are a plurality of busbars 33 held by the busbar plate 17, a connection unit 80 including a control circuit, etc., and a pair of ends. A plate 39 is housed therein.

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 cover 12 has an external terminal 91 on the positive side and an external terminal 92 on the negative side. The external terminals 91 and 92 are electrically connected to the plurality of power storage elements 20 via the connection unit 80 and the bus bar 33, and the power storage device 1 receives electricity from the outside via the external terminals 91 and 92. Charges and discharges electricity to the outside. The external terminals 91 and 92 are made of a conductive member made of a metal such as a copper alloy such as brass, copper, aluminum, or an aluminum alloy. The main body portion 11 is a bottomed rectangular cylindrical housing with an opening formed therein, and accommodates the power storage element 20 and the like.

The main body 11 and outer lid 12 of the exterior body 10 are made of, for example, polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), polyphenylene sulfide resin (PPS), polyphenylene ether (PPE (modified (including PPE)), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyetheretherketone (PEEK), tetrafluoroethylene perfluoroalkyl vinyl ether (PFA), polytetrafluoroethylene (PTFE), polyether It is formed of an insulating member such as sulfone (PES), ABS resin, or a composite material thereof, or a metal coated with an insulating coating. The exterior body 10 thereby prevents the power 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 member such as metal as long as the electrical insulation of the power storage element 20 and the like is maintained.

The power storage element 20 is a secondary battery (single battery) that can charge and discharge electricity, and more specifically, it is a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. . The power storage element 20 has a flat rectangular parallelepiped shape (prismatic shape), and in this embodiment, eight power storage elements 20 are arranged in the X-axis direction. Note that the shape of the power storage elements 20 and the number of power storage elements 20 arranged are not limited. Furthermore, the power 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 battery that can be charged by the user. It may also be a primary battery that can use the stored electricity without having to do so.

Specifically, the power storage element 20 includes a metal container 21. The container 21 is formed into 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 are opposite to each other in the X-axis direction, and the pair of short sides 212 are opposite to each other in the Y-axis direction. Each of the plurality of power storage elements 20 is stacked so that the long sides 211 of the containers 21 face each other, and are housed in the main body 11 .

The lid portion of the container 21 is provided with a positive electrode terminal 221 and a negative electrode terminal 222 made of metal. An insulating member (not shown) is interposed between the lid portion and the positive electrode terminal 221 and the negative electrode terminal 222, and the lid portion and the positive electrode terminal 221 and the negative electrode terminal 222 are insulated by this insulating member.

The positive electrode terminal 221 and the negative electrode terminal 222 are electrode terminals arranged to protrude from the lid portion of the container 21 toward the busbar plate 17 side (upward, that is, toward the positive side in the Z-axis direction). By connecting the positive electrode terminal 221 and the negative electrode terminal 222 to external terminals 91 and 92 via at least one bus bar 33 and the connection unit 80, the power storage device 1 can charge electricity from the outside and also transfer it to the outside. Can discharge electricity. Note that the lid portion of the container 21 may be provided with a liquid injection part for injecting the electrolyte solution, a gas discharge valve for discharging gas to release the pressure when the pressure inside the container 21 increases, and the like. Further, inside the container 21, an electrode body (also referred to as a power storage element or a power generation element), a current collector (a positive electrode current collector and a negative electrode current collector), etc. are arranged, and an electrolytic solution (non-aqueous electrolyte) etc. Although it is enclosed, detailed explanation will be omitted.

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

Further, the connection unit 80 is a unit having a plurality of bus bars, a control board, etc., and connects a power storage element group consisting of eight power storage elements 20 and external terminals 91 and 92. The control board included in the connection unit 80 has a plurality of electrical components, and these electrical components form a detection circuit that detects the state of each power storage element 20, a control circuit that controls charging and discharging, etc. There is. In this embodiment, connection unit 80 is fixed to busbar plate 17. Note that the detection circuit and the control circuit may be formed on separate substrates. Moreover, the connection unit 80 does not need to have a control board. In this case, for example, a control device disposed outside power storage device 1 may control charging and discharging of each power storage element 20.

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

Note that the busbar plate 17 arranged above the plurality of power storage elements 20 may be called, for example, a "busbar frame" or an "inner lid." The busbar plate 17 is made of, for example, PC, PP, PE, PS, PPS, PPE (including modified PPE), PET, PBT, PEEK, PFA, PTFE, PES, ABS resin, or a composite material thereof. It is made of an insulating member or a metal coated with an insulating coating.

The pair of end plates 39 are rectangular plates disposed within the main body 11 at positions that collectively sandwich the plurality of power storage elements 20 . Specifically, the pair of end plates 39 are arranged parallel to the YZ plane at positions sandwiching the plurality of power storage elements 20 in the X-axis direction. That is, the pair of end plates 39 are arranged so as to overlap with the long side surface 211 of the container 21 of the electricity storage element 20 arranged at the outermost side. The end plate 39 is made 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, it is made of metal or the like with an insulating coating. Details of the end plate 39 will be described later.

[Joining structure between main body and outer cover]
Next, the joining structure between the main body portion 11 and the outer cover 12 will be explained. As shown in FIG. 2 and FIG. 3(c) to be described later, a skirt portion 123 extending downward is provided on the entire periphery of the outer lid 12. As shown in FIG. The skirt portion 123 is formed into a circumferentially continuous rectangular frame shape when viewed from below.

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

Thermal welding is employed to join the joint portion 124 and the wall portion 50. Thermal welding is a method of joining members to be joined by melting them with heat, then bringing them into close contact with each other and re-hardening them. Examples of thermal welding include heat sealing and ultrasonic welding. In the present disclosure, bonding using an adhesive is not included in thermal welding. Even when joining using an adhesive, the members to be joined are melted and re-hardened, but if the joint location is analyzed after hardening, the adhesive remains at that location. Therefore, even after joining, it is possible to determine whether the joining is by thermal welding or by adhesive.

During thermal welding, the entire circumference of the tip (upper end) of the wall portion 50 of the main body portion 11 is heated and melted. On the other hand, in the outer lid 12, the entire circumference of the lower end portion of the joint portion 124 is melted. With both of them melted, the outer cover 12 is brought close to the main body 11 and the entire circumference of the lower end of the joint section 124 is pressed against the entire circumference of the tip of the wall section 50, so that the melted parts mix with each other. Fit. After a certain period of time has elapsed in an unheated state, the mixed parts are hardened, integrated, and joined. This joining part is a thermally welded part 90 (see (c) of FIG. 3). The thermally welded portion 90 is continuously provided along the entire circumference of the opening 111. In other words, the main body part 11 and the outer cover 12 have a thermally welded part 90 joined along the entire circumference of the opening part 111. Note that although FIG. 3C shows the interface between the tip (lower end) of the joint portion 124 and the tip (upper end) of the wall portion 50 with respect to the thermally welded portion 90, the interface is actually Since the two are cured in a mixed state, there is no interface between them. This thermal welding part 90 seals the main body part 11 and the outer lid 12 over the entire circumference, ensuring airtightness.

[end plate]
Next, details of the end plate 39 will be explained. 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 top view of the end plate 39, and FIG. 3(c) is a top view of the end plate 39. FIG. In FIG. 3A, the opening 111 is shown by a two-dot chain line, and the power storage element 20 is shown by a broken line. Moreover, in FIG. 3(c), the main body portion 11 and the outer cover 12 are shown with two-dot chain lines, and the power storage element 20 is shown with a broken line. FIG. 3(c) is a sectional view taken along the line IIIC--IIIC in FIGS. 3(a) and 3(b).

Here, the pair of end plates 39 have the same shape although their postures are different. Specifically, the end plate 39 disposed on the minus side in the X-axis direction has a central portion protruding toward the plus side in the X-axis direction, and the end plate 39 disposed on the plus side in the X-axis direction is This is a posture in which the central portion protrudes toward the negative side in the X-axis direction. Therefore, in this embodiment, the details of the end plate 39 disposed on the minus side in the X-axis direction will be described, and the details of the end plate 39 disposed on the plus side in the X-axis direction will be omitted. 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 a first inner wall surface 118, and a pair of inner wall surfaces facing each other in the Y-axis direction will be referred to as a second inner wall surface 119. .

As shown in FIG. 3, the end plate 39 is a curved plate having a rectangular shape in plan view. The end plate 39 is housed within the opening 111 and is interposed between the power storage element 20 disposed closest to the 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 disposed below the upper end of the main body 11, that is, below the thermal welding part 90.

The end plate 39 is curved so that the center portion thereof protrudes toward the positive side in the X-axis direction, that is, toward the power storage element 20 when viewed from above. The end plate 39 has a uniform shape over the entire length in the Z-axis direction. Both end portions of the end plate 39 are arranged on the minus side in the X-axis direction with respect to the center portion. Both end surfaces of the end plate 39 in the Y-axis direction are opposed to a pair of second inner wall surfaces 119 of the opening 111. Note that both end surfaces of the end plate 39 in the Y-axis direction may be in contact with the pair of second inner wall surfaces 119.

Both ends of the end plate 39 in the Y-axis direction are abutting portions 391 and 392 that abut against a pair of corners 113 and 114 on the negative side of the X-axis within the opening 111. The contact portions 391 and 392 are inclined with respect to a pair of edges forming corners 113 and 114 of the opening 111. For example, the corner 113 includes an edge 115 that is one first inner wall surface 118 of the opening 111 and an edge 116 that is one second inner wall surface 119 of the opening 111. The contact portion 391 is inclined at an angle α with respect to the edge 115 and inclined at an angle β with respect to the edge 116. Here, the corners 113 and 114 are parts that have a certain range. The term "corner" refers to the area around the corner; for example, if the corner is rounded, the corner includes the area from the boundary where the angle of the edge that forms the corner begins to change.

Further, an intermediate portion between both ends of the end plate 39 is a non-contacting portion 393 that does not abut against 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 serves as a non-contact portion 393.

As described above, the end plate 39 has a uniform shape over the entire length in the Z-axis direction, and the upper end of the end plate 39 is disposed below the heat welding part 90. Therefore, as shown in FIG. 3C, the non-contacting portion 393 extends from the position corresponding to the center of the power storage element 20 in the Z-axis direction to the position corresponding to the heat welding portion 90. - Not in contact with the inner wall surface 118.

Next, the function of the end plate 39 will be explained. FIG. 4 is a top view schematically showing the internal structure of the main body portion 11 according to the embodiment. Arrow Y1 in FIG. 4 indicates the pressing force applied from the power storage element 20 to the end plate 39 when the power storage element 20 expands. Further, an arrow Y2 in FIG. 4 indicates a pressing force applied to the main body portion 11 from the end plate 39 that has received the pressing force Y1. That is, when the power storage element 20 is not expanded, the pressing forces Y1 and Y2 are not generated, and the end plate 39 is not restrained (pressed) within the opening 111. That is, the end plate 39 is not deformed from the state before being accommodated in the main body portion 11. Immediately after the end plate 39 is inserted into the opening 111 together with the plurality of power storage elements 20, the end plate 39 may receive external force from the opening 111 or the power storage elements 20 before expansion. Since this external force is a slight force (less than 10%) compared to the pressing force Y1 when the power storage element 20 is expanded, it is assumed that the end plate 39 is not restrained (pressed) in this state as well.

The plurality of power storage elements 20 expand as they are charged and discharged. Due to this expansion, a pressing force Y1 is applied from the power storage element 20 to the end plate 39. Specifically, the power storage element 20 expands the most at the center of the long side surface 211 of the container 21 . Therefore, the pressing force Y1 acts on the central portion of the end plate 39 in the Y-axis direction. Further, the non-contacting portion 393 of the end plate 39 does not abut against the first inner wall surface 118 of the opening 111, but the abutting portions 391 and 392 abut against the corners 113 and 114 of the opening 111. ing. Therefore, the pressing force Y2 is applied only to the corner portions 113 and 114 from the contact portions 391 and 392.

Here, a flat end plate is assumed as a comparative example. When the plurality of power storage elements 20 expand, a large pressing force is applied to the central portion of the flat end plate. Therefore, in the first inner wall surface 118 of the opening 111, the central portion within the surface is most likely to deform due to the pressing force from the central portion of the flat end plate. Due to this deformation, the heat welded portion 90 at a position corresponding to the center of the first inner wall surface 118 is likely to be damaged.

On the other hand, since the corners 113 and 114 of the opening 111 have greater rigidity than the center portion of the first inner wall surface 118, they are less likely to deform even if they receive the pressing force Y1. In other words, the heat welded 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 contact parts 391 and 392, which are both ends of the end plate 39, contact the corners 113 and 114 in the opening 111, and the non-contact part 393, which is the middle part, contacts the corners 113 and 114 in the opening 111. The first inner wall surface 118 of the portion 111 is not in contact with the first inner wall surface 118 . Thereby, the pressing force that the first inner wall surface 118 of the opening 111 receives via the end plate 39 can be concentrated on the corners 113 and 114 and not be applied to the center of the first inner wall surface 118. can. Therefore, damage to the heat welded portion 90 can be suppressed.

[Effects etc.]
As described above, according to the power storage device 1 according to the present embodiment, a plurality of power storage elements 20 are stacked in the X-axis direction (predetermined direction), and a plurality of power storage elements 20 are placed in positions sandwiching each other in the X-axis direction. It includes a pair of disposed end plates 39 and an exterior body 10 that accommodates the plurality of power 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 in which a plurality of power storage elements 20 and an end plate 39 are housed, and a main body 11 (first member) that covers the opening 111. 11. The outer cover 12 (second member) is joined to the outer cover 11. The main body part 11 and the outer lid 12 have a thermally welded part 90 that is joined to each other along the entire circumference of the opening part 111. The opening 111 is formed into a polygonal shape when the opening 111 is viewed from above. Among the pair of end plates 39, at least one end plate 39 has contact portions 391, 392, each of which has both ends abutting corners 113, 114 within the opening 111, when the opening 111 is viewed from above. The intermediate portion between both ends is a non-contacting portion 393 that does not abut against the first inner wall surface 118 of the opening 111 .

According to this, the contact parts 391 and 392 which are both ends of the end plate 39 contact the corners 113 and 114 in the opening 111, and the non-contact part 393 which is the intermediate part contacts the first corner of the opening 111. It is not in contact with the inner wall surface 118. Thereby, the pressing force that the first inner wall surface 118 of the opening 111 receives via the end plate 39 can be concentrated on the corners 113 and 114 and not be applied to the center of the first inner wall surface 118. can. Therefore, damage to the heat welded portion 90 can be suppressed.

Furthermore, the contact portions 391 and 392 are inclined with respect to the pair of edges forming the corner portions 113 and 114 of the opening portion 111.

According to this, since the contact portions 391 and 392 of the end plate 39 are inclined with respect to the pair of edges forming the corner portions 113 and 114, when the end plate 39 receives the pressing force Y1, the end plate 39 The plate 39 can be stretched 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 it is possible to prevent the non-contacting portion 393 from coming into contact with the first inner wall surface 118 of the opening 111 by any chance. Therefore, damage to the heat welded portion 90 can be more reliably suppressed.

Furthermore, the end plate 39 has a curved shape when viewed from above with respect to the opening 111 .

According to this, since the end plate 39 has a curved shape, the end plate 39 itself can exert elastic force. Therefore, when the plurality of power storage elements 20 expand, the end plate 39 will repel, and a restraining force can be applied to the plurality of power 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. Thereby, damage to the thermally welded portion 90 can be more reliably suppressed.

In addition, the non-contacting portion 393 extends from the position corresponding to the center of the electricity storage element 20 to the position corresponding to the heat welding portion 90 in the Z-axis direction (insertion direction) to the first inner wall surface 118 of the opening 111. Not in contact.

According to this, the non-contacting portion 393 does not contact the first inner wall surface 118 of the opening 111 from the position corresponding to the center of the power storage element 20 to the position corresponding to the heat welding portion 90 . For this reason, the direct force transmission path from the point (center) where the pressing force is greatest in the expanded power storage element 20 to the thermally welded portion 90 is cut off. Therefore, force caused by the expansion of power storage element 20 is less likely to act on thermally welded portion 90, and damage to thermally welded portion 90 can be suppressed more reliably.

Further, the end plate 39 is not restrained within the opening 111 when the plurality of power storage elements 20 are not expanded.

Here, if the end plate 39 is restrained together with the plurality of power storage elements 20 via another restraint member, even if the plurality of power storage elements 20 expand, the end plate 39 is restrained by the restraint force from the restraint member. deformation is suppressed. 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 plurality of power storage elements 20. In other words, damage to the thermally welded portion 90 is likely to occur. The configuration of the present disclosure is suitable for such an unrestricted end plate 39.

[Modification 1]
In the embodiment described above, the case is illustrated in which both end surfaces of the end plate 39 in the Y-axis direction face the pair of second inner wall surfaces 119. In this first modification, a case will be described in which both end surfaces of the end plate 39 in the Y-axis direction are in contact with the first inner wall surface 118. FIG. 5 is an explanatory diagram showing a schematic configuration of an end plate 39a according to Modification 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 top view of the end plate 39a, and FIG. 5(c) is a top view of the end plate 39a. FIG. FIG. 5(c) is a cross-sectional view of FIGS. 5(a) and 5(b) taken along the VC-VC line. In the following description, parts that are the same as those in the embodiment described above may be denoted by the same reference numerals, and the description thereof may be omitted.

As shown in FIG. 5, the end plate 39a is curved so that the center portion thereof protrudes toward the positive side in the X-axis direction, that is, protrudes toward the power 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 arranged on the minus side in the X-axis direction with respect to the center portion. Both end surfaces 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 the both end faces only need to be in contact with the first inner wall surface 118 when the power storage element 20 expands, and do not need to be in contact with the first inner wall surface 118 before the power storage element 20 expands. good.

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

Even with such an end plate 39a, it is possible to achieve the same effects as those of the above embodiment.

Here, when the end plate 39a receives a pressing force from the expanded electricity storage element 20, both end surfaces of the end plate 39a in the Y-axis direction apply a pressing force to the first inner wall surface 118. Since both end surfaces are in surface contact with the first inner wall surface 118, the pressing force is distributed. Thereby, the pressing force applied to the corners 113 and 114 can be weakened, and damage to the corners 113 and 114 can be suppressed.

[Modification 2]
In the embodiment described above, the case 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 power storage element 20 is illustrated. In this second modification, a case will be described in which both ends of the end plate 39b in the Y-axis direction are bent.

FIG. 6 is an explanatory diagram showing a schematic configuration of an end plate 39b according to a second modification. 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 top view of the end plate 39b, and FIG. 6(c) is a top view of the end plate 39b. FIG. FIG. 6(c) is a cross-sectional view of FIGS. 6(a) and 6(b) taken along the line VIC-VIC. In the following description, parts that are the same as those in the embodiment described above may be denoted by the same reference numerals, and the description thereof may be omitted.

As shown in FIG. 6, the end plate 39b includes a flat plate portion 395b, and a pair of protruding portions 396b and 397b that protrude so as to bend toward the first inner wall surface 118 from both ends of the flat plate portion 395b in the Y-axis direction. It is equipped with Each protruding portion 396b, 397b is bent orthogonally to the flat plate portion 395b. Each of the protrusions 396b and 397b is an example of an abutting part that abuts against the corners 113 and 114 of the opening 111. Specifically, the tip surfaces of each of the protrusions 396b and 397b are in surface contact with the first inner wall surface 118, and the outer surfaces of each of the protrusions 396b and 397b are in surface contact with the second inner wall surface 119. . Note that the tip surface and outer surface of each of the protrusions 396b and 397b only need to be in contact with the first inner wall surface 118 and the second inner wall surface 119 when the power storage element 20 expands, and before the power storage element 20 expands. In this case, the first inner wall surface 118 and the second inner wall surface 119 may not be in contact with each other.

The flat plate portion 395b (intermediate portion) between the pair of protrusions 396b and 397b of the end plate 39b is an example of a non-contacting portion that does not abut against the first inner wall surface 118 of the opening 111.

Even in such an end plate 39b, it is possible to achieve the same effects as those of the above embodiment.

Here, when the end plate 39b receives a pressing force from the expanded electricity storage element 20, the tip surfaces of the respective protrusions 396b and 397b on the end plate 39b apply a pressing force to the first inner wall surface 118. Since the tip surface is in surface contact with the first inner wall surface 118, the pressing force is dispersed. Thereby, the pressing force applied to the corners 113 and 114 can be weakened, and damage to the corners 113 and 114 can be suppressed.

[Modification 3]
In the above modification 2, the case where the pair of protrusions 396b and 397b of the end plate 39b are bent perpendicularly to the flat plate part 395b is illustrated. In this third modification, a case will be described in which both ends of the end plate 39 in the Y-axis direction are bent. FIG. 6 describes a case where a pair of protrusions 396c and 397c of an end plate 39c according to modification 2 are bent so as to be inclined with respect to a flat plate part 395c.

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 top view of the end plate 39c, and FIG. 7(c) is a top view of the end plate 39c. FIG. FIG. 7(c) is a cross-sectional view of FIG. 7(a) and FIG. 7(b) taken along the line VIIC-VIIC. In the following description, parts that are the same as those in the embodiment described above may be denoted by the same reference numerals, and the description thereof may be omitted.

As shown in FIG. 7, the end plate 39c includes a flat plate portion 395c, and a pair of protruding portions 396c and 397c that protrude from both ends of the flat plate portion 395c in the Y-axis direction so as to be bent toward the first inner wall surface 118. It is equipped with Each of the protrusions 396c and 397c is bent with respect to the flat plate part 395c so that the distance between them increases toward the tip. Each of the protrusions 396c and 397c is an example of an abutting part that abuts against the corners 113 and 114 of the opening 111. Specifically, the tip surfaces of each of the protrusions 396c and 397c are in surface contact with the first inner wall surface 118, and the outer surfaces of each of the protrusions 396c and 397c are inclined and in contact with the second inner wall surface 119. Not yet. Note that the tip surfaces of each of the protrusions 396c and 397c only need to be in contact with the first inner wall surface 118 when the power storage element 20 expands, and before the power storage element 20 expands, They do not have to be in contact with each other.

The flat plate portion 395c (intermediate portion) between the pair of protrusions 396c and 397c of the end plate 39c is an example of a non-contacting portion that does not abut against the first inner wall surface 118 of the opening 111.

Even in such an end plate 39c, it is possible to achieve the same effects as in the second modification.

[Modification 4]
In the embodiment described above, 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 power storage element 20. Illustrated as an example. In this fourth modification, a case will be described in which a slit portion 390d is provided in the end plate 39d to form a non-contact portion.

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 top view of the end plate 39d, and FIG. 8(c) is a top view of the end plate 39d. FIG. FIG. 8(c) is a cross-sectional view taken along the line VIIIC-VIIIC in FIGS. 8(a) and 8(b). In the following description, parts that are the same as those in the embodiment described above may be denoted by the same reference numerals, and the description thereof may be omitted.

As shown in FIG. 8, the end plate 39d has a flat plate shape as a whole, and a slit portion 390d is formed at the upper end of the central portion in the Y-axis direction. The slit portion 390d is a rectangular opening in plan view that is open at the top. The lower end portion of slit portion 390d is arranged below the center portion of power storage element 20. That is, the slit portion 390d contacts the first inner wall surface 118 of the opening portion 111 from a position corresponding to the center of the electricity storage element 20 to a position corresponding to the heat welding portion 90 in the Z-axis direction (insertion direction). do not. In this way, the slit portion 390d is an example of a portion that does not contact the first inner wall surface 118 of the opening portion 111.

Further, both ends of the end plate 39d in the Y-axis direction are abutting portions 391d and 392d that abut against the corners 113 and 114 of the opening 111. Specifically, contact portions 391d and 392d only need to contact first inner wall surface 118 when power storage element 20 expands, and contact portions 391d and 392d contact first inner wall surface 118 before power storage element 20 expands. They do not have to be in contact with each other.

Even in such an end plate 39d, it is possible to achieve the same effects as those of the above embodiment.

Further, since the end plate 39d is provided with the slit portion 390d, the end plate 39d itself is lightweight. Therefore, it is possible to reduce the weight of power storage device 1.

[Modification 5]
In the embodiment described above, the end plate 39 has a uniform shape along the entire length in the Z-axis direction. In this fifth modification, an end plate 39e whose shape is not uniform along the entire length in the Z-axis direction will be described.

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 top view of the end plate 39e, and FIG. 9(c) is a top view of the end plate 39e. FIG. FIG. 9(c) is a cross-sectional view of FIG. 9(a) and FIG. 9(b) taken along the line IXC--IXC. In the following description, parts that are the same as those in the embodiment described above may be denoted by the same reference numerals, and the description thereof may be omitted.

As shown in FIG. 9, the lower end of the end plate 39e is formed into a flat plate, and the entire end plate 39e is in contact with the first inner wall surface 118 of the opening 111. Further, the upper end portion of the end plate 39e is curved such that the center portion in the Y-axis direction protrudes toward the plus side in the X-axis direction, that is, protrudes toward the power storage element 20. Here, both ends of the end plate 39e in the Y-axis direction are abutting portions 391e and 392e that abut against a pair of corner portions 113 and 114 within the opening 111. The contact portions 391e and 392e contact the respective corners 113 and 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 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 the portion above the lower end of the end plate 39e is in a non-contact state that does not come into contact with the first inner wall surface 118. 393e. In this case as well, the non-contacting portion 393e extends from the opening 111 from a position corresponding to the center of the power storage element 20 in the Z-axis direction to a position corresponding to the heat welding portion 90, as shown in FIG. 9(c). does not come into contact with the first inner wall surface 118 of.

Even in such an end plate 39e, it is possible to achieve the same effects as those of the above embodiment.

[others]
Although the power storage devices according to the embodiments and modifications thereof of the present invention have been described above, the present invention is not limited to the embodiments and modifications thereof. In other words, the embodiments and modifications disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and scope equivalent to the claims are included.

For example, in the above embodiment and its modified examples, the case where the opening 111 has a rectangular shape in plan view has been exemplified, but the opening may have another polygonal shape. In that case, the opening preferably has a pair of first inner wall surfaces facing each other in the direction in which the plurality of power storage elements are arranged (X-axis direction).

Further, in the above embodiment and its modification examples, the upper end of the end plate 39 is arranged below the heat welding part 90, but the upper end of the end plate is equivalent to the heat welding part 90, Alternatively, it may be placed above. Even in this case, the non-contacting portion of the end plate does not come into contact with the first inner wall surface 118 from the position corresponding to the center of the power storage element 20 to the position corresponding to the heat welding part 90 in the Z-axis direction. desired.

Further, forms constructed by arbitrarily combining the constituent elements included in the above embodiments and their modifications are also included within the scope of the present invention.

The present invention can be applied to a power storage device including a power storage element such as a lithium ion secondary battery.

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

Claims (5)

a plurality of power storage elements stacked in a predetermined direction;
a pair of end plates arranged to sandwich the plurality of power storage elements in the predetermined direction;
an exterior body that accommodates the plurality of power storage elements and the pair of end plates;
The exterior body is
a first member having an opening, in which the plurality of power storage elements and the end plate are housed;
a second member joined to the first member while covering the opening;
The first member and the second member have a heat welded part joined to each other along the entire circumference of the opening,
The opening has a polygonal shape when viewed from above,
Of the pair of end plates, at least one end plate is a contact portion whose both ends are in contact with a corner in the opening when viewed from above, and an intermediate portion between the two end portions. The power storage device is a non-contacting portion that does not come into contact with an inner wall surface of the opening. The power storage device according to claim 1, wherein the contact portion is inclined with respect to a pair of edges forming corners of the opening. The power storage device according to claim 1 , wherein the end plate has a curved shape in plan view. The non-contact portion extends from the opening from a position corresponding to the center of the power storage element to a position corresponding to the thermal welding part in the insertion direction when inserting the plurality of power storage elements into the opening. The power storage device according to any one of claims 1 to 3, wherein the power storage device is not in contact with an inner wall surface of the power storage device. The power storage device according to any one of claims 1 to 4, wherein the end plate is not restrained within the opening when the plurality of power storage elements are not expanded.

Images