JP2020135932A - Power storage module - Google Patents

Abstract

To provide a power storage module with a uniform resin frame thickness.SOLUTION: In a power storage module 4, since each of corners C1 to C4 is a folding corner and is composed of a resin sheet having more layers than the number of resin sheets forming the side portions, the corners C1 to C4 are locally thickened in the state before heat welding. Therefore, when the corners C1 to C4 are roller-pressed twice when a resin frame 21 is heat-welded to a bipolar electrode 14, it is possible to prevent the corners C1 to C4 from becoming excessively thin. Therefore, the thickness of the folding corners C1 to C4 of the resin frame 21 and the thickness of the side portions S1 to S4 are made uniform.SELECTED DRAWING: Figure 3

Description

The present invention relates to a power storage module.

Patent Document 1 describes a power storage module. This power storage module includes a plurality of stacked bipolar electrodes. The bipolar electrode has a current collector, a positive electrode layer provided on one surface of the current collector, and a negative electrode layer provided on the other surface of the current collector. Further, this power storage module includes a resin frame that covers the edge of the bipolar electrode. The resin frame is provided to seal the electrolytic solution inside the battery so as not to leak to the outside.

Japanese Unexamined Patent Publication No. 2005-005163

When the resin frame as described above is provided on the bipolar electrode, the use of heat welding can be considered. That is, the resin frame can be welded to the bipolar electrode by placing the resin frame on one surface of the bipolar electrode and moving the roller along the edge of the bipolar electrode.

However, when the bipolar electrode has a rectangular shape and the rollers are moved along the respective sides of the resin frame, the corners of the resin frame are roller-pressed twice. As a result, the thickness of the corner portion becomes thinner than the thickness of the side portion. When the corners of the resin frame are locally thinned in this way, even in a power storage module having a configuration in which a plurality of bipolar electrodes and the resin frame are overlapped with each other, a locally thinned portion may occur. In this case, it is conceivable that a molding defect may occur in the secondary seal provided on the outside of the resin frame, or a situation may occur in which the airtightness of the secondary seal cannot be sufficiently ensured.

An object of the present invention is to provide a power storage module in which the thickness of a resin frame is made uniform.

The power storage module according to one embodiment of the present invention is a power storage module including a rectangular electrode and a rectangular frame-shaped resin frame joined to the edge of the electrode, and the resin frame is a single resin sheet. In addition to being composed of four corners, it is also composed of four corners and four sides connecting the corners, and at least a part of the four corners is folded with one resin sheet. It is a folded angle portion, and the number of layers of the resin sheet in the folded angle portion is larger than the number of layers of the resin sheet in the side portion.

In the above power storage module, since the number of layers of the resin sheet at the folding angle portion is larger than the number of layers of the resin sheet at the side portion, the folding angle portion of the resin frame is rolled twice when the resin frame is heat-welded to the electrode. The difference in thickness between the folded angle portion and the side portion when pressed can be suppressed. Therefore, in the power storage module, since a part or all of the four corners of the resin frame are folded corners, it is possible to suppress a situation where the corners of the resin frame are locally thinned. It is possible to achieve uniform thickness.

In the power storage module according to another form, the folding angle portion is composed of three or more layers of resin sheets.

In the power storage module according to another form, the resin sheet has a rectangular frame-shaped main body frame portion and four overhanging portions extending along the side portions of the main body frame portion, and the resin frame is a resin sheet. Each overhanging portion is folded over the main body frame portion along the outer edge of the main body frame portion, and the folded angle portion is formed by overlapping two overhanging portions on the main body frame portion.

In the power storage module according to another form, the overhanging portion extends over the entire length of the side portion of the main body frame portion.

In the power storage module according to another form, the width of the overhanging portion of the resin sheet is narrower than the width of the side portion of the main body frame portion in which the overhanging portion is folded, and the resin frame is formed by the main body frame portion and the overhanging portion. It has a formed step. In this case, the separator of the power storage module can be arranged on the main body frame so as to fit inside the overhanging portion, and the upper surface position of the separator can be lowered by the thickness of the overhanging portion.

According to the present invention, there is provided a power storage module in which the thickness of the resin frame is made uniform.

It is the schematic sectional drawing which showed the power storage device which concerns on embodiment. It is a schematic cross-sectional view which shows the internal structure of the power storage module shown in FIG. It is the schematic perspective view which showed the bipolar electrode and the resin frame of FIG. It is a developed view of the resin frame shown in FIG. It is a top view which showed the laminated state of the bipolar electrode and a resin frame shown in FIG. 5A is a cross-sectional view taken along the line (a) aa, (b) is a cross-sectional view taken along the line bb, and (c) is a sectional view taken along the line cc of the bipolar electrode and the resin frame shown in FIG. It is a perspective view which showed the structure of the resin frame of a different structure. It is a developed view of the resin frame shown in FIG. 7. It is a perspective view which showed the structure of the resin frame of a different structure. It is a developed view of the resin frame shown in FIG.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals will be used for the same or equivalent elements, and duplicate description will be omitted.

The power storage device 1 shown in FIG. 1 is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 1 includes a module stack 2 including a plurality of stacked power storage modules 4, and a restraint member 3 that applies a restraint load to the module stack 2 in the stacking direction.

The module laminate 2 includes a plurality of (three in this embodiment) power storage modules 4 and a plurality of (four in this embodiment) conductive plates 5. The power storage module 4 is a bipolar battery and has a rectangular shape when viewed from the stacking direction. The power storage module 4 is, for example, a secondary battery such as a nickel hydrogen secondary battery or a lithium ion secondary battery, or an electric double layer capacitor. In the following description, a nickel-metal hydride secondary battery will be described as an example.

The power storage modules 4 adjacent to each other in the stacking direction are electrically connected to each other via the conductive plate 5. The conductive plates 5 are arranged between the power storage modules 4 adjacent to each other in the stacking direction. The conductive plate 5 can be arranged outside the power storage module 4 located at the laminated end. In this case, the positive electrode terminal 6 is connected to one of the conductive plates 5 arranged outside the power storage module 4 located at the laminated end, and the negative electrode terminal 7 is connected to the other conductive plate 5. The positive electrode terminal 6 and the negative electrode terminal 7 are drawn out from the edge of the conductive plate 5, for example, in a direction intersecting the stacking direction. The positive electrode terminal 6 and the negative electrode terminal 7 charge and discharge the power storage device 1.

Inside the conductive plate 5, a plurality of flow paths 5a through which a refrigerant such as air flows are provided. The flow path 5a extends along a direction intersecting (orthogonal) with, for example, the stacking direction and the drawing direction of the positive electrode terminal 6 and the negative electrode terminal 7. The conductive plate 5 not only functions as a connecting member that electrically connects the power storage modules 4 to each other, but also serves as a heat dissipation plate that dissipates heat generated by the power storage module 4 by circulating a refrigerant through these flow paths 5a. It also has a function. In the example of FIG. 1, the area of the conductive plate 5 seen from the stacking direction is smaller than the area of the power storage module 4, but from the viewpoint of improving heat dissipation, the area of the conductive plate 5 is the area of the power storage module 4. It may be the same as, and may be larger than the area of the power storage module 4.

The restraint member 3 is composed of a pair of end plates 8 that sandwich the module laminate 2 in the stacking direction, and fastening bolts 9 and nuts 10 that fasten the end plates 8 to each other. The end plate 8 is a rectangular metal plate having an area one size larger than the area of the power storage module 4 and the conductive plate 5 when viewed from the stacking direction. A film F having electrical insulation is provided on the inner side surface of the end plate 8 (the surface on the module laminate 2 side). The film F insulates between the end plate 8 and the power storage module 4 (or the conductive plate 5 when the conductive plate 5 is arranged outside the power storage module 4 located at the laminated end).

An insertion hole 8a is provided at the edge of the end plate 8 at a position outside the module laminate 2. The fastening bolt 9 is passed from the insertion hole 8a of one end plate 8 toward the insertion hole 8a of the other end plate 8, and is attached to the tip portion of the fastening bolt 9 protruding from the insertion hole 8a of the other end plate 8. , The nut 10 is screwed. As a result, the power storage module 4 and the conductive plate 5 are sandwiched by the end plates 8 to be unitized as the module laminate 2, and a restraining load is applied to the module laminate 2 in the stacking direction.

Next, the configuration of the power storage module 4 will be described in detail. As shown in FIG. 2, the power storage module 4 includes an electrode laminated body 11 and a resin sealing body 12 that seals the electrode laminated body 11. The electrode laminate 11 is composed of a plurality of electrodes laminated along the stacking direction D1 of the power storage module 4 via the separator 13. These electrodes include a laminate of a plurality of bipolar electrodes 14, a negative electrode termination electrode 18, and a positive electrode termination electrode 19. In the present embodiment, the stacking direction D1 of the electrode laminated body 11 coincides with the stacking direction of the module laminated body 2. The electrode laminate 11 has a side surface 11a extending in the lamination direction D1.

The bipolar electrode 14 has an electrode plate 15 including one surface 15a and the other surface 15b on the opposite side of the one surface 15a, a positive electrode 16 provided on the one surface 15a, and a negative electrode 17 provided on the other surface 15b. ing. The positive electrode 16 is a positive electrode active material layer formed by coating the electrode plate 15 with the positive electrode active material. The negative electrode 17 is a negative electrode active material layer formed by applying the negative electrode active material to the electrode plate 15. In the electrode laminate 11, the positive electrode 16 of one bipolar electrode 14 faces the negative electrode 17 of another bipolar electrode 14 adjacent to one of the stacking directions D1 with the separator 13 interposed therebetween. In the electrode laminate 11, the negative electrode 17 of one bipolar electrode 14 faces the positive electrode 16 of yet another bipolar electrode 14 adjacent to the other in the stacking direction D1 with the separator 13 interposed therebetween.

The negative electrode terminal electrode 18 includes an electrode plate 15 and a negative electrode 17 provided on the other surface 15b of the electrode plate 15. The negative electrode terminal electrode 18 is arranged at one end of the stacking direction D1 so that the other surface 15b faces the center side of the stacking direction D1 in the electrode laminated body 11. One surface 15a of the electrode plate 15 of the negative electrode terminal electrode 18 constitutes one outer surface in the stacking direction D1 of the electrode laminate 11, and is electrically connected to one conductive plate 5 (see FIG. 1) adjacent to the power storage module 4. It is connected to the. The negative electrode 17 provided on the other surface 15b of the electrode plate 15 of the negative electrode terminal electrode 18 faces the positive electrode 16 of the bipolar electrode 14 at one end in the stacking direction D1 via the separator 13. The other surface 15b of the electrode plate 15 of the positive electrode terminal electrode 19 constitutes the other outer surface in the stacking direction D1 of the electrode laminate 11, and is electrically connected to the other conductive plate 5 (see FIG. 1) adjacent to the power storage module 4. It is connected to the.

The positive electrode terminal electrode 19 has an electrode plate 15 and a positive electrode 16 provided on one surface 15a of the electrode plate 15. The positive electrode terminal electrode 19 is arranged at the other end of the stacking direction D1 so that one surface 15a faces the center side of the stacking direction D1 in the electrode laminated body 11. The positive electrode 16 provided on one surface 15a of the positive electrode terminal electrode 19 faces the negative electrode 17 of the bipolar electrode 14 at the other end in the stacking direction D1 via the separator 13.

The conductive plate 5 is in contact with one surface 15a of the electrode plate 15 of the negative electrode terminal electrode 18. Further, the other conductive plate 5 adjacent to the power storage module 4 is in contact with the other surface 15b of the electrode plate 15 of the positive electrode terminal electrode 19. The restraint load from the restraint member 3 is applied to the electrode laminate 11 from the negative electrode terminal electrode 18 and the positive electrode terminal electrode 19 via the conductive plate 5. That is, the conductive plate 5 is also a restraining member that applies a restraining load to the electrode laminated body 11 along the stacking direction D1.

The electrode plate 15 is made of a metal such as nickel or a nickel-plated steel plate. As an example, the electrode plate 15 is a rectangular metal foil made of nickel. The edge portion 15c of the electrode plate 15 has a rectangular frame shape, and is an uncoated region in which the positive electrode active material and the negative electrode active material are not coated. Examples of the positive electrode active material constituting the positive electrode 16 include nickel hydroxide. Examples of the negative electrode active material constituting the negative electrode 17 include a hydrogen storage alloy. In the present embodiment, the formation region of the negative electrode 17 on the other surface 15b of the electrode plate 15 is slightly larger than the formation region of the positive electrode 16 on the one surface 15a of the electrode plate 15.

The separator 13 is formed in a sheet shape, for example. Examples of the separator 13 include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a woven fabric made of polypropylene, methyl cellulose and the like, or a non-woven fabric. The separator 13 may be reinforced with a vinylidene fluoride resin compound. The separator 13 is not limited to a sheet shape, and a bag shape may be used.

The sealing body 12 is formed in a rectangular tubular shape as a whole by, for example, an insulating resin. The sealing body 12 is provided on the side surface 11a of the electrode laminated body 11 so as to surround the edge portion 15c of the electrode plate 15. The sealing body 12 holds the edge portion 15c on the side surface 11a. The sealing body 12 surrounds a plurality of resin frames 21 joined to each edge portion 15c of the electrode plate 15 from the outside and the resin frame 21 from the outside along the side surface 11a, and is joined to each of the resin frames 21. It has a seal 22 and. The resin frame 21 and the secondary seal 22 are, for example, an insulating resin having alkali resistance. Examples of the constituent materials of the resin frame 21 and the secondary seal 22 include polypropylene (PP), polyphenylene sulfide (PPS), and modified polyphenylene ether (modified PPE).

The resin frame 21 has a rectangular frame shape when viewed from the stacking direction D1 of the electrode laminate 11. The resin frame 21 is joined over the entire circumference of the edge portion 14c of the bipolar electrode 14 (that is, the edge portion 15c of the electrode plate 15). The resin frame 21 is airtightly (liquid-tightly) heat-welded to one surface 14a of the bipolar electrode 14 (one surface 15a of the electrode plate 15 in this embodiment). As will be described later, the resin frame 21 is composed of one resin sheet. In the power storage module 4, a plurality of electrode plates 15 and a plurality of resin frames 21 surrounding the edge portion 15c of the electrode plate 15 on one surface 15a of the electrode plate 15 are laminated.

A part of the inside of the resin frame 21 viewed from the direction orthogonal to the stacking direction D1 is located between the edge portions 14c of the bipolar electrodes 14 adjacent to each other in the stacking direction D1, and the resin frame 21 is stacked in the stacking direction D1. A part of the outside seen from the direction orthogonal to the above projects outward from the edge 14c of the bipolar electrode 14. The resin frame 21 is embedded in the secondary seal 22 in the outer edge region protruding outward from the edge portion 14c of the bipolar electrode 14. The resin frames 21 adjacent to each other in the stacking direction D1 may be separated from each other or may be in contact with each other. Further, the outer edge portions of the resin frame 21 may be joined to each other by, for example, hot plate welding.

In the present embodiment, the resin frame 21 is provided not only on the electrode plate 15 of the bipolar electrode 14, but also on the electrode plate 15 of the negative electrode terminal 18 and the electrode plate 15 of the positive electrode 19. In the negative electrode terminal electrode 18, a resin frame 21 is provided on the edge 15c of one surface 15a of the electrode plate 15, and in the positive electrode terminal 19, resin is provided on both edges 15c of both one surface 15a and the other surface 15b of the electrode plate 15. A frame 21 is provided.

The region where the electrode plate 15 and the resin frame 21 overlap is a joint region K between the electrode plate 15 and the resin frame 21. In the joint region K, the surface of the electrode plate 15 is roughened. The roughened region may be only the joint region K, but in the present embodiment, the entire surface of the electrode plate 15 is roughened. Roughening can be achieved, for example, by forming a plurality of protrusions by electrolytic plating. By forming the plurality of protrusions, at the bonding interface between the electrode plate 15 and the resin frame 21, the molten resin enters between the plurality of protrusions formed by the roughening, and the anchor effect is exhibited. Thereby, the bonding strength between the electrode plate 15 and the resin frame 21 can be improved. The protrusions formed during roughening have a shape that becomes thicker from the base end side to the tip end side, for example. As a result, the cross-sectional shape between the adjacent protrusions becomes an undercut shape, and the anchor effect can be enhanced.

The secondary seal 22 is provided on the outside of the electrode laminate 11 and the resin frame 21, and constitutes an outer wall (housing) of the power storage module 4. The secondary seal 22 is formed, for example, by injection molding of a resin, and extends along the stacking direction D1 over the entire length of the electrode laminate 11. The secondary seal 22 has a rectangular frame shape extending with the stacking direction D1 as the axial direction. The secondary seal 22 is welded to the outer surface of the resin frame 21 by heat during injection molding, for example.

The resin frame 21 and the secondary seal 22 form an internal space V between adjacent electrodes and seal the internal space V. More specifically, the secondary seal 22, together with the resin frame 21, has the bipolar electrodes 14 adjacent to each other along the stacking direction D1 and the negative electrode termination electrodes 18 and the bipolar electrodes 14 adjacent to each other along the stacking direction D1. The space between the positive electrode terminal 19 and the bipolar electrode 14 adjacent to each other along the stacking direction D1 are sealed. As a result, an airtightly partitioned internal space V is formed between the adjacent bipolar electrodes 14, between the negative electrode terminal 18 and the bipolar electrode 14, and between the positive electrode 19 and the bipolar electrode 14. ing. An electrolytic solution (not shown) containing an alkaline solution such as an aqueous potassium hydroxide solution is housed in the internal space V. The electrolytic solution is impregnated in the separator 13, the positive electrode 16, and the negative electrode 17. A liquid injection port for injecting a liquid injection port into the internal space V is provided on the side surface of the sealing body 12.

As shown in FIGS. 3 to 6, the resin frame 21 has a rectangular frame shape composed of four corner portions C1 to C4 and four side portions S1 to S4 connecting the corner portions C1 to C4. The resin frame 21 is composed of one resin sheet 30 arranged on one surface 14a of the bipolar electrode 14. As shown in FIG. 4, the resin sheet 30 has a rectangular frame-shaped main body frame portion 35 composed of four side portions 31 to 34, and four overhanging portions 36 to 39 protruding from each side portion 31 to 34. And have.

The main body frame portion 35 has a rectangular outer edge E that substantially coincides with the outer edge of the resin frame 21. The main body frame portion 35 has four side portions 31 to 34, and more specifically, a pair of side portions 31 and 33 facing each other and a pair of side portions orthogonal to the pair of side portions 31 and 33. It has 32 and 34. All four sides 31 to 34 extend with a uniform width along the outer edge E. In this embodiment, the four sides 31 to 34 have the same width d1. The main body frame portion 35 has a rectangular opening 23 defined by four side portions 31 to 34, and the positive electrode 16 of the bipolar electrode 14 is exposed from the opening 23.

The four overhanging portions 36 to 39 are strip-shaped portions extending with a uniform width along the side portions 31 to 34 of the corresponding main body frame portion 35. In this embodiment, the four overhanging portions 36 to 39 extend over the entire length of the side portions 31 to 34. Further, in the present embodiment, the four overhanging portions 36 to 39 have the same width d2. Further, in the present embodiment, the width d2 of the four overhanging portions 36 to 39 is designed to be narrower than the width d1 of the four side portions 31 to 34. In the resin frame 21, each of the overhanging portions 36 to 39 is bent along the outer edge E of the main body frame portion 35 and overlapped with the corresponding side portions 31 to 34.

Therefore, the side portions S1 to S4 of the resin frame 21 have a two-layer structure in which the overhanging portions 36 to 39 and the side portions 31 to 34 of the resin sheet 30 are folded. The corner portions C1 to C4 of the resin frame 21 are folded angle portions in which both of the two overhanging portions 36 to 39 located at positions sandwiching the corner portions C1 to C4 are folded. In the folded angle portions C1 to C4, the overhanging portions 36 and 38 are folded and the overhanging portions 37 and 39 are further folded, and the folded angle portions C1 to C4 have a three-layer structure. Therefore, in the resin frame 21, the number of layers of the resin sheets forming the folded angle portions C1 to 4 is larger than the number of layers of the resin sheets forming the side portions S1 to S4. In the specification of the present application, even if it is originally one resin sheet, the folded layers are counted separately, and the number of folded layers is also included in the number of layers.

At least the entire rectangular region T shown in FIG. 5 is composed of three layers of resin sheets in the folded angle portions C1 to C4. The rectangular region T has a side length of d2, and can be defined as a square region having the vertices P of the folding angle portions C1 to 4 as one vertex.

In the present embodiment, since the width d2 of the overhanging portions 36 to 39 is narrower than the width d1 of the side portions 31 to 34, the overhanging portions 36 to 39 are overlapped with the main body frame portion 35, so that FIG. As shown in the above, a step portion 21a is formed by the main body frame portion 35 and the overhanging portions 36 to 39. A part or all of the separator 13 may be accommodated in the step portion 21a. The height of the step portion 21a corresponds to the thickness of the overhanging portions 36 to 39 (that is, the thickness of the resin sheet 30).

The resin frame 21 is heat-welded to one surface 14a of the bipolar electrode 14. Specifically, the resin frame 21 of the resin sheet 30 with all the overhanging portions 36 to 39 bent) is placed on one surface 14a of the bipolar electrode 14, and the side portions S1 to the resin frame 21 are placed. By moving the roller linearly along S4, the resin frame 21 is welded to the bipolar electrode 14. At this time, since the corner portions C1 to C4 of the resin frame 21 are roller-pressed twice, they can be thinner than the side portions S1 to S4 that are roller-pressed only once. If the corners C1 to C4 of the resin frame 21 are locally thinned, even in the power storage module 4 in which the bipolar electrode 14 and the resin frame 21 are overlapped with each other, a locally thinned portion is generated. obtain. In this case, it is conceivable that a molding defect may occur in the secondary seal 22, or a situation may occur in which the airtightness of the secondary seal 22 cannot be sufficiently ensured. For example, when the secondary seal 22 is formed by injection molding, if the power storage module 4 has a locally thin portion, sufficient mold clamping cannot be performed at that portion, and problems such as resin leakage may occur.

In the resin frame 21 described above, since the corner portions C1 to C4 are all folded corner portions and are composed of resin sheets having a larger number of layers than the number of resin sheets forming the side portions, heat welding is performed. In the previous state, the corners C1 to C4 are locally thickened. Therefore, when the corner portions C1 to C4 are roller-pressed twice when the resin frame 21 is heat-welded to the bipolar electrode 14, the situation where the corner portions C1 to C4 become excessively thin can be suppressed. Therefore, the thickness of the folded angle portions C1 to C4 of the resin frame 21 and the thickness of the side portions S1 to S4 are made uniform. Further, in the power storage module 4 having a configuration in which a plurality of bipolar electrodes 14 and a resin frame 21 are overlapped with each other, a situation in which a locally thinned portion is generated can be suppressed, and high moldability of the secondary seal 22 can be realized.

Further, the resin frame 21 has a step portion 21a formed by the main body frame portion 35 of the resin sheet 30 and the overhanging portions 36 to 39, so as to fit inside the folded overhanging portions 36 to 39. , The separator 13 can be arranged on the main body frame portion 35. As a result, the upper surface position of the separator 13 can be lowered by the thickness of the overhanging portions 36 to 39.

The resin frame 21 is not limited to the mode described above, and may be a mode as shown in FIG. 7.

As shown in FIG. 7, the resin frame 21A is composed of one resin sheet 30A arranged on one surface 14a of the bipolar electrode 14. As shown in FIG. 8, the resin sheet 30A has a main body frame portion 35 similar to the resin sheet 30 described above, and four overhanging portions 36A, 37, 38A protruding from each side portion 31 to 34 of the main body frame portion 35. , 39 and.

Of the four overhangs 36A, 37, 38A, 39, the overhangs 37, 39 extend over the entire length of the corresponding side portions 32, 34, similar to the resin sheet 30 described above. The overhanging portion 36A does not extend over the entire length of the corresponding side portion 31, and is shortened so as not to reach the outer edge E on the side portion 34 side. The overhanging portion 36A is shorter than the width of the overhanging portion 39, and is set so that the overhanging portion 36A does not overlap the overhanging portion 39 when bent. The overhanging portion 38A does not extend over the entire length of the corresponding side portion 33, and is shortened so as not to reach the outer edge E on the side portion 32 side. The overhanging portion 38A is shorter than the width of the overhanging portion 37, and is set so that the overhanging portion 38A does not overlap the overhanging portion 37 when bent.

In the resin frame 21A, the overhanging portions 36A, 37, 38A, 39 of the resin sheet 30A are bent along the outer edge E of the main body frame portion 35 and overlapped with the corresponding side portions 31 to 34. Therefore, the side portions S1 to S4 of the resin frame 21A have a two-layer structure in which the overhanging portions 36A, 37, 38A, and 39 of the resin sheet 30 are folded over the side portions 31 to 34. Further, the corner portions C1 and C3 of the resin frame 21A also have a two-layer structure in which the overhanging portions 36A, 37, 38A and 39 of the resin sheet 30 are folded over the side portions 31 to 34. The corner portions C2 and C4 of the resin frame 21A are folded corner portions in which both of the two overhanging portions 36A, 37, 38A and 39 located at positions sandwiching the corner portions C2 and C4 are folded. In the folded angle portions C2 and C4, the overhanging portions 36A and 38A are folded and the overhanging portions 37 and 39 are further folded, and the folded angle portions C2 and C4 each have a three-layer structure. .. Therefore, in the resin frame 21A, the number of layers of the resin sheets constituting the folded angle portions C2 and C4 is larger than the number of layers of the resin sheets forming the side portions S1 to S4.

In the resin frame 21A, since the corner portions C2 and C4 are both folded corner portions and are composed of resin sheets having a larger number of layers than the number of resin sheets constituting the side portions S1 to S4, heat is generated. Local thickening of the corners C2 and C4 is achieved in the state before welding. Therefore, when the corner portions C2 and C4 are roller-pressed twice when the resin frame 21A is heat-welded to the bipolar electrode 14, the situation where the corner portions C2 and C4 become excessively thin can be suppressed. Therefore, the thickness of the folded angle portions C2 and C4 of the resin frame 21A and the thickness of the side portions S1 to S4 are made uniform.

The resin frame 21 may have an embodiment as shown in FIG. The resin frame 21B shown in FIG. 9 is different from the above-mentioned resin frame 21A only in the shape of the constituent resin sheet, and is the same in other respects. As shown in FIG. 10, the resin sheet 30B constituting the resin frame 21B has a main body frame portion 35 similar to the resin sheet 30 described above and four overhangs protruding from each side portion 31 to 34 of the main body frame portion 35. It has parts 36B, 37, 38B, and 39.

Of the four overhangs 36B, 37, 38B, 39, the overhangs 37, 39 extend over the entire length of the corresponding side portions 32, 34, similar to the resin sheet 30 described above. The overhanging portion 36B does not extend over the entire length of the corresponding side portion 31, and is shortened so as not to reach the outer edge E on the side portion 32 side. The overhanging portion 36B is shorter than the width of the overhanging portion 37, and is set so that the overhanging portion 36B does not overlap the overhanging portion 37 when bent. The overhanging portion 38B does not extend over the entire length of the corresponding side portion 33, and is shortened so as not to reach the outer edge E on the side portion 34 side. The overhanging portion 38B is shorter than the width of the overhanging portion 39, and is set so that the overhanging portion 38B does not overlap the overhanging portion 39 when bent.

In the resin frame 21B, the overhanging portions 36B, 37, 38B, 39 of the resin sheet 30B are bent along the outer edge E of the main body frame portion 35 and overlapped with the corresponding side portions 31 to 34. Therefore, the side portions S1 to S4 of the resin frame 21B have a two-layer structure in which the overhanging portions 36B, 37, 38B, 39 of the resin sheet 30 are folded over the side portions 31 to 34. Further, the corner portions C2 and C4 of the resin frame 21B also have a two-layer structure in which the overhanging portions 36B, 37, 38B and 39 of the resin sheet 30 are folded over the side portions 31 to 34. In the corner portions C1 and C3 of the resin frame 21B, both of the two overhanging portions 36B, 37, 38B and 39 located at positions sandwiching the corner portions C1 and C3 are folded corner portions. In the folded angle portions C1 and C3, the overhanging portions 36B and 38B are folded and the overhanging portions 37 and 39 are further folded, and the folded angle portions C1 and C3 each have a three-layer structure. .. Therefore, in the resin frame 21B, the number of layers of the resin sheets forming the folded angle portions C1 and C3 is larger than the number of layers of the resin sheets forming the side portions S1 to S4.

In the resin frame 21B, since the corner portions C1 and C3 are both folded corner portions and are composed of resin sheets having a larger number of layers than the number of resin sheets constituting the side portions S1 to S4, heat is generated. Local thickening of the corners C1 and C3 is achieved in the state before welding. Therefore, when the corner portions C1 and C3 are roller-pressed twice when the resin frame 21B is heat-welded to the bipolar electrode 14, the situation where the corner portions C1 and C3 become excessively thin can be suppressed. Therefore, the thickness of the folded angle portions C1 and C3 of the resin frame 21B and the thickness of the side portions S1 to S4 are made uniform.

Further, in the electrode stack 11 of the power storage module 4, the resin frame 21A shown in FIG. 7 and the resin frame 21B shown in FIG. 9 may be alternately superposed via the bipolar electrode 14 and the separator. By superimposing the resin frame 21A in which the corners C2 and C4 are folded corners and the resin frame 21B in which the corners C1 and C3 are folded corners, the side portions S1 are formed in all the corners C1 to C4. It is possible to make the thickness uniform with ~ S4.

The present invention is not limited to the above-described embodiment, and can be variously modified. For example, the number of layers of the folded angle portion and the number of layers of the side portion of the resin frame can be appropriately increased or decreased as long as the number of layers of the folded angle portion is larger than the number of layers of the side portion. For example, the number of layers of the resin sheet constituting the folded angle portion is not limited to three, and may be four or more. When a plurality of corners of the resin frame are folded corners, the number of layers of the resin sheet constituting each folded corner may be the same or different from each other. The side portion is not limited to the two layers and can be increased or decreased as appropriate.

1 ... power storage device, 4 ... power storage module, 11 ... electrode laminate, 11a ... side surface, 13 ... separator, 14 ... bipolar electrode, 15 ... electrode plate, 16 ... positive electrode, 17 ... negative electrode, 21, 21A, 21B ... resin frame , 21a ... Step part, 22 ... Secondary seal, 30, 30A, 30B ... Resin sheet, 31-34 ... Side part, 35 ... Main body frame part, 36, 36A, 36B, 37, 38, 38A, 38B, 39 ... Overhangs, C1 to C4 ... Corners, S1 to S4 ... Sides.

Claims (5)

A power storage module including a rectangular electrode and a rectangular frame-shaped resin frame joined to the edge of the electrode.
The resin frame is composed of one resin sheet, four corner portions, and four side portions connecting the corner portions.
At least a part of the four corners is a folded corner where the one resin sheet is folded.
A power storage module in which the number of layers of the resin sheet in the folded angle portion is larger than the number of layers of the resin sheet in the side portion. The power storage module according to claim 1, wherein the folded angle portion is composed of three or more layers of resin sheets. The resin sheet has a rectangular frame-shaped main body frame portion and four overhanging portions extending along the side portions of the main body frame portion.
The resin frame is formed by folding each of the overhanging portions of the resin sheet onto the main body frame portion along the outer edge of the main body frame portion.
The power storage module according to claim 1 or 2, wherein the folded angle portion is formed by overlapping two of the overhanging portions on the main body frame portion. The power storage module according to claim 3, wherein the overhanging portion extends over the entire length of a side portion of the main body frame portion. The width of the overhanging portion of the resin sheet is narrower than the width of the side portion of the main body frame portion on which the overhanging portion is folded.
The power storage module according to claim 3 or 4, wherein the resin frame has a step portion formed by the main body frame portion and the overhanging portion.

Images