JP7409212B2 - Energy storage module - Google Patents

Description

The present disclosure relates to a power storage module.

As a conventional power storage module, a bipolar battery is known that includes a bipolar electrode in which a positive electrode is formed on one surface of a metal plate and a negative electrode is formed on the other surface (see, for example, Patent Document 1). A bipolar battery includes a stacked body in which bipolar electrodes and separators are alternately stacked along the stacking direction. A sealing body that seals between bipolar electrodes adjacent to each other in the stacking direction is provided on the side surface of the laminate, and an electrolytic solution is accommodated in the internal space formed between the bipolar electrodes.

JP2011-204386A

In the electricity storage module, the sealed body may have a plurality of resin parts made of mutually different resin materials. In this case, due to changes in the environmental temperature, the bonding strength between the resin parts may decrease, and the sealing performance of the electrolyte by the sealing body may decrease.

An object of the present disclosure is to provide a power storage module that can suppress deterioration in sealing performance of a sealed body.

A power storage module according to one aspect of the present disclosure includes a laminate having a plurality of stacked metal plates and a module for sealing an internal space formed between two adjacent metal plates of the plurality of metal plates. a sealing body, the plurality of metal plates include a metal plate of a positive terminal electrode, a metal plate of a negative terminal electrode, and a plurality of metal plates of bipolar electrodes provided between the positive terminal electrode and the negative terminal electrode. The sealing body includes a rectangular ring-shaped first sealing part joined to the peripheral edge of the metal plate, and a second sealing part provided around the stacked first sealing part. , the second sealing part has a first resin part provided around the first sealing part, and a second resin part provided around the first resin part, and the second sealing part has a first resin part provided around the first resin part, and a second resin part provided around the first resin part. The difference between the linear expansion coefficient of the first sealing part and the linear expansion coefficient of the first resin part is smaller than the difference between the linear expansion coefficient of the first sealing part and the linear expansion coefficient of the second resin part.

In this electricity storage module, the difference between the linear expansion coefficient of the first sealing part and the linear expansion coefficient of the first resin part is greater than the difference between the linear expansion coefficient of the first sealing part and the linear expansion coefficient of the second resin part. It's also small. Therefore, the linear expansion coefficient of the sealing body changes in two steps from the inside to the outside. Therefore, compared to a configuration in which the linear expansion coefficient of the sealed body changes in one step, it is possible to suppress the difference in the linear expansion coefficient between each part of the sealed body. Therefore, the bonding strength between the various parts of the sealed body is prevented from decreasing due to changes in the environmental temperature. As a result, it is possible to suppress the deterioration of the sealability of the sealed body.

The linear expansion coefficient of the first resin part may be smaller than that of the first sealing part and larger than that of the second resin part. In this case, the linear expansion coefficient of the sealing body can be reduced in two steps from the inside to the outside.

The melt flow rate of the first resin part may be greater than the melt flow rate of the second resin part. In this case, when forming the first resin part around the first sealing part by injection molding, the resin material easily follows the surface shape of the first sealing part. Therefore, generation of voids at the interface between the first sealing part and the first resin part is suppressed.

The second sealing part further includes a third resin part provided around the second resin part, and the linear expansion coefficient of the third resin part is equivalent to that of the second resin part. In this case, the bonding strength between the second resin part and the third resin part is unlikely to decrease due to changes in environmental temperature. Therefore, it is possible to suppress the deterioration of the sealability of the sealed body.

According to the present disclosure, it is possible to suppress a decrease in sealing performance of a sealed body.

FIG. 1 is a schematic cross-sectional view showing an example of a power storage device including a power storage module according to an embodiment. FIG. 2 is a schematic cross-sectional view showing the internal configuration of the power storage module shown in FIG. 1. FIG. FIG. 3 is a perspective view of the power storage module shown in FIG. 1.

Hereinafter, one embodiment will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and redundant description will be omitted.

FIG. 1 is a schematic cross-sectional view showing an example of a power storage device including a power storage module according to an embodiment. Power storage device 1 shown in FIG. 1 is used, for example, as a battery for various vehicles such as a forklift, a hybrid vehicle, or an electric vehicle. Power storage device 1 includes a module stack 2 and a restraining member 3.

The module stack 2 includes a plurality (four in this embodiment) of power storage modules 4 and a plurality (three in this embodiment) of conductive plates 5. The plurality of power storage modules 4 are stacked along the stacking direction D. The power storage module 4 is a bipolar battery, and has a rectangular shape when viewed from the stacking direction D. The power storage module 4 is, for example, a secondary battery such as a nickel metal hydride 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 exemplified.

Two power storage modules 4 adjacent to each other in the stacking direction D are electrically connected to each other via a conductive plate 5. Here, power storage modules 4 are arranged at both stacked ends of the module stack 2, and conductive plates 5 are respectively arranged between two power storage modules 4 adjacent to each other in the stacking direction D. A conductive plate P different from the conductive plate 5 is arranged outside in the stacking direction D of the power storage module 4 located at the stacked end. A positive electrode terminal 6 is connected to the conductive plate P located at the bottom end of the stack. A negative electrode terminal 7 is connected to the conductive plate P located at the upper end of the stack. The positive electrode terminal 6 and the negative electrode terminal 7 are drawn out, for example, from the edge of the conductive plate P in a direction intersecting (perpendicular to) the lamination direction D. Charging and discharging of the power storage device 1 is performed by the positive electrode terminal 6 and the negative electrode terminal 7.

The conductive plate 5 is provided with a plurality of channels 5a. The flow path 5a is a through hole through which a cooling fluid such as air flows. The flow path 5a extends, for example, in a direction intersecting (orthogonal to) the stacking direction D and the direction in which the positive electrode terminal 6 and the negative electrode terminal 7 are drawn out, and penetrates the conductive plate 5. The conductive plate 5 functions as a connecting member that electrically connects two power storage modules 4 adjacent to each other in the stacking direction D, and also serves as a connecting member for electrically connecting two power storage modules 4 that are adjacent to each other in the stacking direction D. It also functions as a heat sink that releases the heat generated by the heat sink. In the example of FIG. 1, the area of the conductive plate 5 viewed from the stacking direction D 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 same as the area of the power storage module 4. The area may be the same, or may be larger than the area of the power storage module 4.

The restraining member 3 is a member that applies a restraining load to the module laminate 2 in the stacking direction D of the module laminate 2 . The restraining member 3 includes a pair of end plates 8 that sandwich the module stack 2 in the stacking direction D, and a fastening bolt 9 and a nut 10 that fasten the pair of end plates 8 to each other. The end plate 8 is a rectangular metal plate having an area that is one size larger than the areas of the power storage module 4, the conductive plate 5, and the conductive plate P when viewed from the stacking direction D. An insulating plate F having electrical insulation properties is provided between the end plate 8 and the conductive plate P. The insulating plate F provides insulation between the end plate 8 and the conductive plate P.

An insertion hole 8 a is provided in the edge of the end plate 8 at a position outside the module stack 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 the tip of the fastening bolt 9 protruding from the insertion hole 8a of the other end plate 8 has a , nuts 10 are screwed together. Thereby, the power storage module 4, the conductive plate 5, and the conductive plate P are sandwiched between the pair of end plates 8, and are unitized as the module stack 2. A restraining load is applied to the module stack 2 in the stacking direction D.

Next, the configuration of power storage module 4 will be explained in detail. FIG. 2 is a schematic cross-sectional view showing the internal configuration of the power storage module shown in FIG. 1. FIG. As shown in FIG. 2, the electricity storage module 4 includes an electrode stack 11 and a resin sealing body 12 that seals the electrode stack 11. The electrode stack 11 is composed of a plurality of electrodes stacked along the stacking direction D of the power storage modules 4 with separators 13 in between. These electrodes include a negative termination electrode 18 , a positive termination electrode 19 , and a plurality of bipolar electrodes 14 provided between the negative termination electrode 18 and the positive termination electrode 19 .

The plurality of bipolar electrodes 14 are provided between the negative terminal electrode 18 and the positive terminal electrode 19. Bipolar electrode 14 includes a metal plate 15 including one surface 15a and another surface 15b opposite to one surface 15a, a positive electrode 16 provided on one surface 15a, and a negative electrode 17 provided on the other surface 15b. ing. The positive electrode 16 is formed by coating the metal plate 15 with a positive electrode active material. Examples of the positive electrode active material constituting the positive electrode 16 include nickel hydroxide. The negative electrode 17 is formed by coating the metal plate 15 with a negative electrode active material. Examples of the negative electrode active material constituting the negative electrode 17 include a hydrogen storage alloy.

In this embodiment, the area where the negative electrode 17 is formed on the other side 15b of the metal plate 15 is slightly larger than the area where the positive electrode 16 is formed on the one side 15a of the metal plate 15. In the electrode stack 11, the positive electrode 16 of one bipolar electrode 14 faces the negative electrode 17 of another bipolar electrode 14 adjacent to it on one side in the stacking direction D with the separator 13 in between. In the electrode stack 11, the negative electrode 17 of one bipolar electrode 14 faces the positive electrode 16 of another bipolar electrode 14 adjacent to the other bipolar electrode 14 in the stacking direction D with the separator 13 in between.

The negative terminal electrode 18 includes a metal plate 15 and a negative electrode 17 provided on the other surface 15b of the metal plate 15. The negative terminal electrode 18 is arranged at one end of the plurality of electrodes in the stacking direction D. The negative electrode 17 provided on the other surface 15b of the negative terminal electrode 18 faces the positive electrode 16 of the bipolar electrode 14 at one end in the stacking direction D with the separator 13 in between.

The positive terminal electrode 19 includes a metal plate 15 and a positive electrode 16 provided on one side 15a of the metal plate 15. The positive terminal electrode 19 is arranged at the other end of the plurality of electrodes in the stacking direction D. The positive electrode 16 provided on one side 15a of the positive terminal electrode 19 faces the negative electrode 17 of the bipolar electrode 14 at the other end in the stacking direction D with the separator 13 in between.

In this embodiment, the electrode stack 11 further includes a pair of metal plates 15 that are arranged outside the negative terminal electrode 18 and the positive terminal electrode 19 and constitute the outermost layer of the electrode stack 11. One surface 15a of the metal plate 15 disposed outside the negative terminal electrode 18 is electrically connected to one of the conductive plates 5 or P (see FIG. 1) adjacent to the power storage module 4. The other surface 15b of the metal plate 15 disposed outside the positive terminal electrode 19 is electrically connected to the other conductive plate 5 or conductive plate P (see FIG. 1) adjacent to the power storage module 4.

The electrode stack 11 includes a plurality of metal plates 15 stacked along the stacking direction D. The plurality of metal plates 15 include the metal plate 15 of the negative terminal electrode 18 , the metal plate 15 of the positive terminal electrode 19 , the metal plate 15 of the plurality of bipolar electrodes 14 , and the outer side of the negative terminal electrode 18 and the positive terminal electrode 19 . A pair of metal plates 15 are arranged.

The metal plate 15 is made of, for example, a nickel plate whose surface is plated, a steel plate whose surface is plated, or the like. Here, the metal plate 15 is constituted by a plated steel plate whose surface is plated with nickel. For example, ordinary steel such as rolled steel or special steel such as stainless steel is used as the steel plate that serves as the base material of the plated steel plate. The peripheral edge part 15c of the metal plate 15 of the bipolar electrode 14, the negative terminal electrode 18, and the positive terminal electrode 19 has a rectangular frame shape, and is an uncoated area where the positive electrode active material and the negative electrode active material are not coated. In the pair of metal plates 15 arranged outside the negative terminal electrode 18 and the positive terminal electrode 19, the entire area including the peripheral edge 15c is an uncoated area.

The separator 13 is formed, for example, in a sheet shape. Examples of the separator 13 include porous films made of polyolefin resins such as polyethylene (PE) and polypropylene (PP), and woven or nonwoven fabrics made of polypropylene, methylcellulose, and the like. The separator 13 may be reinforced with a vinylidene fluoride resin compound.

FIG. 3 is a perspective view of the power storage module shown in FIG. 1. As shown in FIG. 3, the sealing body 12 is made of, for example, an insulating resin and is formed into a rectangular cylindrical shape as a whole, and has four side parts 12a, 12b, 12c, and 12d. Side portions 12a and 12b are opposed to each other. The sides 12c and 12d are opposed to each other. A plurality of through holes 12e are provided in the side portion 12a.

As shown in FIG. 2, the sealing body 12 is provided on the side surface 11a of the electrode stack 11 so as to surround the peripheral edge 15c of the metal plate 15. The sealing body 12 holds a peripheral portion 15c on the side surface 11a. The sealing body 12 is provided around the plurality of first sealing parts 21 joined to the peripheral edge 15c of the metal plate 15 and the plurality of first sealing parts 21 that extend along the stacking direction D and are stacked. It has a second sealing part 22 that is closed. The first sealing part 21 and the second sealing part 22 are made of an insulating resin having alkali resistance. Examples of the constituent material of the sealing body 12 include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), and the like.

The first sealing portion 21 is provided continuously over the entire circumference of the peripheral edge portion 15c on one side 15a of the metal plate 15, and has a rectangular ring shape or a rectangular frame shape when viewed from the stacking direction D. The first sealing portion 21 is arranged outside not only the metal plate 15 of the bipolar electrode 14 but also the metal plate 15 of the negative terminal electrode 18, the metal plate 15 of the positive terminal electrode 19, the negative terminal electrode 18, and the positive terminal electrode 19. A pair of metal plates 15 are also provided. In the metal plate 15 disposed outside the positive terminal electrode 19, a first sealing portion 21 is provided on the peripheral edge portions 15c of both one surface 15a and the other surface 15b.

The first sealing part 21 is formed using a film having a predetermined thickness in the lamination direction D, for example. The first sealing part 21 is overlapped with the peripheral edge part 15c of the metal plate 15, and an overlapping part K is formed. In the overlapping portion K, the first sealing portion 21 is hermetically welded to the metal plate 15 by, for example, ultrasonic waves or thermocompression bonding. The surface of the metal plate 15 is roughened in the overlapping portion K. In this embodiment, the entire surface of the metal plate 15 is roughened. The surface roughening can be achieved by forming a plurality of protrusions, for example, by electrolytic plating. In the overlapping portion K, the molten resin enters between the plurality of protrusions formed by roughening the surface, and an anchor effect is exerted. Thereby, the bonding strength between the metal plate 15 and the first sealing part 21 can be improved. The projections formed during surface roughening have, for example, a shape that becomes thicker from the proximal end toward the distal end. As a result, the cross-sectional shape between adjacent protrusions becomes an undercut shape, making it possible to enhance the anchoring effect.

The inner portion of the first sealing portion 21 is located between the peripheral edges 15c of two metal plates 15 adjacent to each other in the stacking direction D. A stepped portion 23 on which the edge of the separator 13 is placed is provided on the inner side of the first sealing portion 21 welded to the bipolar electrode 14 and the positive terminal electrode 19 . The outer portions of the plurality of first sealing portions 21 protrude outward from the edge of the metal plate 15. In the side portions 12b, 12c, and 12d, the tips of the plurality of first sealing portions 21 form a welded portion 24. The welded portion 24 is formed by, for example, joining together the tips of a plurality of first sealing portions 21 that are melted by hot plate welding or infrared welding. The welded portion 24 is formed before the second sealing portion 22 is injection molded.

By forming the welded portions 24 in the side portions 12b, 12c, and 12d, the positions of the tips of the plurality of first sealing portions 21 can be aligned. No welded portion 24 is formed on the side portion 12a. The units in which the first sealing part 21 is welded to the metal plate 15 are stacked on the basis of the side corresponding to the side part 12a of the unit. Thereby, the positions of the tips of the plurality of first sealing parts 21 are aligned in the side part 12a compared to the side parts 12b, 12c, and 12d.

The second sealing portion 22 is provided outside the electrode stack 11 and the first sealing portion 21 and constitutes an outer wall (casing) of the power storage module 4. The second sealing part 22 is formed, for example, by injection molding of resin, and extends over the entire length of the electrode stack 11 along the stacking direction D. The second sealing portion 22 has a rectangular cylindrical shape extending with the stacking direction D as the axial direction. The second sealing part 22 is welded to the first sealing part 21 by heat during injection molding, for example.

The second sealing part 22 includes a first resin part 26 provided around the first sealing part 21 , a second resin part 27 provided around the first resin part 26 , and a second resin part 27 provided around the first resin part 26 . and a third resin part 28 provided around the .

The first resin portion 26 has a rectangular cylindrical shape extending with the stacking direction D as an axial direction. The first resin part 26 is arranged between the first sealing part 21 and the second resin part 27. The first resin part 26 constitutes the inner surface of the second sealing part 22. The first resin part 26 is, for example, welded to the tip of the first sealing part 21 (the welded part 24 in the side parts 12b, 12c, and 12d) by heat during injection molding, and A compatible part 25 is formed between the two parts. In the compatible portion 25, the first resin portion 26 and the tip portions of the first sealing portion 21 are thermally melted and are compatible with each other. In the side portion 12a, the tips of the plurality of first sealing portions 21 are bonded to each other in the compatible portion 25.

The second resin portion 27 has a main body portion 27A and an overhang portion 27B. The main body portion 27A has a rectangular cylindrical shape extending with the stacking direction D as an axial direction, and covers the outer surface 26a of the first resin portion 26. The main body portion 27A is arranged between the first resin portion 26 and the third resin portion 28. The overhang portion 27B protrudes inside the electrode stack 11 from one end of the main body portion 27A in the stacking direction D. The second resin portion 27 is formed into an L-shaped cross section by a main body portion 27A and an overhang portion 27B.

For example, the main body portion 27A is welded to the outer surface 26a by heat during injection molding. The overhang portion 27B is welded to the first sealing portion 21 provided on one side 15a of the metal plate 15 disposed outside the negative terminal electrode 18. The overhang portion 27B is also welded to one end surface of the first resin portion 26 in the stacking direction D. Although not shown, compatible parts are formed between the second resin part 27 and each of the first resin part 26 and the first sealing part 21.

The third resin part 28 has a main body part 28A and an overhang part 28B. The main body portion 28A has a rectangular cylindrical shape extending with the stacking direction D as an axial direction, and covers the outer surface 27a of the second resin portion 27. The main body portion 28A constitutes the outer surface of the second sealing portion 22. The overhang portion 28B projects from the other end of the main body portion 28A in the stacking direction D to the inside of the electrode stack 11. The third resin portion 28 is formed into an L-shaped cross section by a main body portion 28A and an overhang portion 28B.

For example, the main body portion 28A is welded to the outer surface 27a by heat during injection molding. The overhang portion 28B is welded to the first sealing portion 21 provided on the other surface 15b of the metal plate 15 disposed outside the positive terminal electrode 19. The overhang portion 28B is also welded to the other end surface of the first resin portion 26 in the stacking direction D and the other end surface of the main body portion 27A in the stacking direction D. The overhang portion 27B is exposed from the third resin portion 28. Although not shown, compatible parts are also formed between the third resin part 28 and each of the second resin part 27, the first resin part 26, and the first sealing part 21.

The sealing body 12 seals an internal space V formed between two adjacent metal plates 15 among the plurality of metal plates 15 . As a result, an airtightly partitioned internal space V is formed between two adjacent metal plates 15. This internal space V accommodates, for example, an aqueous electrolyte (not shown) containing an alkaline solution such as an aqueous potassium hydroxide solution. The electrolytic solution is impregnated into the separator 13, the positive electrode 16, and the negative electrode 17. The internal space V communicates with a through hole 12e (see FIG. 3) provided in the side portion 12a.

The difference between the linear expansion coefficient of the first sealing part 21 and the linear expansion coefficient of the first resin part 26 is larger than the difference between the linear expansion coefficient of the first sealing part 21 and the second resin part 27. small. The linear expansion coefficient of the first resin part 26 is smaller than that of the first sealing part 21 and larger than that of the second resin part 27. The linear expansion coefficients of the second resin part 27 and the third resin part 28 are equal to each other. Each linear expansion coefficient is adjusted, for example, by the constituent material of each part. In this embodiment, the same material is used as the constituent material of the second resin part 27 and the third resin part 28.

The first sealing portion 21 is made of, for example, acid-modified polypropylene. The first resin portion 26 is made of, for example, polypropylene. The second resin part 27 and the third resin part 28 are constructed by mixing polypropylene with modified polyphenylene ether having high strength, for example. The linear expansion coefficient of the first sealing portion 21 may be, for example, 12×10 ⁻⁵ /K or more and 25×10 ⁻⁵ /K or less, or 18×10 ⁻⁵ /K or more and 23×10 ⁻⁵ /K. The following may be sufficient. The linear expansion coefficient of the first resin portion 26 may be, for example, not less than 5×10 ⁻⁵ /K and not more than 15×10 ⁻⁵ /K, and not less than 8×10 ⁻⁵ /K and not more than 11×10 ⁻⁵ /K. It may be. The linear expansion coefficients of the second resin part 27 and the third resin part 28 may be, for example, 3×10 ⁻⁵ /K or more and 12×10 ⁻⁵ /K or less, and 5×10 ⁻⁵ /K or more and 10× It may be 10 ⁻⁵ /K or less.

In this embodiment, the second resin part 27 and the third resin part 28 are made of, for example, PPE as a resin having high tensile strength. The tensile strengths of the second resin part 27 and the third resin part 28 are equal to each other. The tensile strength of the second resin part 27 and the third resin part 28 is, for example, 37 MPa.

The melt flow rate of the first resin part 26 is higher than the melt flow rates of the second resin part 27 and the third resin part 28. In this embodiment, the melt flow rates of the second resin part 27 and the third resin part 28 are equal to each other. The melt flow rate is determined according to JIS K7210. The melt flow rate of the first resin part 26 may be, for example, 3 g/10 min or more and 15 g/10 min or less, or 5 g/10 min or more and 11 g/10 min or less, at a temperature of 230° C. and a load of 2.16 kgf. . The melt flow rate of the second resin part 27 and the third resin part 28 may be, for example, 11 g/10 min or more and 25 g/10 min or less, or 13 g/10 min or more and 23 g/10 min or less, at a temperature of 230° C. and a load of 10 kgf. There may be. Each melt flow rate is adjusted, for example, by the molecular weight of the constituent material constituting each resin part. Note that the melt flow rate of the first sealing part 21 is higher than the melt flow rate of the first resin part 26. The melt flow rate of the first sealing part 21 may be, for example, 11 g/10 min or more and 25 g/10 min or less, or 13 g/10 min or more and 23 g/10 min or less, at a temperature of 230° C. and a load of 2.16 kgf. good.

The difference between the mold shrinkage rate of the first sealing part 21 and the mold shrinkage rate of the first resin part 26 is larger than the difference between the mold shrinkage rate of the first sealing part 21 and the mold shrinkage rate of the second resin part 27. small. The molding shrinkage rate of the first resin part 26 is greater than that of the first sealing part 21 and smaller than the molding shrinkage rate of the second resin part 27 and the third resin part 28 . In this embodiment, the molding shrinkage rates of the second resin part 27 and the third resin part 28 are equal to each other. The molding shrinkage rate of the first sealing portion 21 is, for example, 0.4 or more and 1.8 or less. The molding shrinkage rate of the first resin portion 26 may be, for example, 0.8 or more and 2.0 or less, or 0.9 or more and 1.2 or less. The molding shrinkage rate of the second resin part 27 and the third resin part 28 may be, for example, 1.8 or more and 2.8 or less, or 2.0 or more and 2.5 or less.

An additive (antioxidant) is added to the first sealing portion 21 to prevent deterioration of the resin due to the strong alkaline electrolyte. Since the first sealing part 21 and the first resin part 26 are mutually dissolved, the additive added to the first sealing part 21 is diffused into the first resin part 26 by a so-called bleed phenomenon. For this reason, there is a possibility that the additive in the first sealing part 21 will gradually decrease. Therefore, in this embodiment, the same additive is added to the first resin part 26 and the first sealing part 21 in advance. This prevents the additive from unilaterally diffusing from the first sealing part 21 to the first resin part 26. Furthermore, when the additive in the first sealing part 21 and the first resin part 26 is consumed by coming into contact with the electrolytic solution, the additive is diffused between the first sealing part 21 and the first resin part 26 in both directions. go back and forth. In this way, in the first sealing part 21 and the first resin part 26, the additives can complement each other, so that electrolyte resistance is improved.

Since the second sealing portion 22 constitutes the outer wall of the power storage module 4, it needs to have high strength. Therefore, the constituent material of the second sealing portion 22 is selected with emphasis on strength. On the other hand, for the first sealing part 21, a different constituent material from that of the second sealing part 22 is selected in consideration of weldability with the metal plate 15 and the second sealing part 22, etc. Suppose that the entire second sealing part 22 including the first resin part 26 is made of the same material, and the linear expansion coefficient of the first resin part 26 is the same as that of the second resin part 27 and the third resin part 28. If the coefficient is approximately the same, the difference in linear expansion coefficient between the first resin part 26 and the first sealing part 21 will be large. Therefore, due to changes in the environmental temperature, the bonding strength between the first resin part 26 and the first sealing part 21 may decrease, and the sealing performance of the electrolyte by the sealing body 12 may decrease.

On the other hand, in the electricity storage module 4, the first resin part 26 is made of a material different from that of the second resin part 27 and the third resin part 28, and has a coefficient of linear expansion that is different from that of the first sealing part 21. The difference between the coefficient of linear expansion of the first resin part 26 is smaller than the difference between the coefficient of linear expansion of the first sealing part 21 and the coefficient of linear expansion of the second resin part 27. In this way, the linear expansion coefficient of the first resin part 26 is set between the linear expansion coefficient of the first sealing part 21 and the linear expansion coefficients of the second resin part 27 and the third resin part 28. The linear expansion coefficient of the sealing body 12 changes in two steps from the inside to the outside. Therefore, compared to a configuration in which the linear expansion coefficient of the sealing body 12 changes in one step, the difference in linear expansion coefficient at the interface between each part of the sealing body 12 can be suppressed. Therefore, the bonding strength between the various parts of the sealed body 12 is prevented from decreasing due to changes in the environmental temperature. As a result, deterioration in the sealing performance of the sealed body 12 can be suppressed.

The linear expansion coefficient of the first resin part 26 is larger than that of the first sealing part 21 and smaller than the linear expansion coefficients of the second resin part 27 and the third resin part 28. Therefore, the linear expansion coefficient of the sealing body 12 can be reduced in two steps from the inside to the outside.

The melt flow rate of the first resin portion 26 is higher than the melt flow rates of the second resin portion 27 and the third resin portion 28 . Therefore, when forming the first resin part 26 around the first sealing part 21 by injection molding, the resin material easily follows the surface shape of the first sealing part 21. Therefore, generation of voids at the interface between the first sealing part 21 and the first resin part 26 is suppressed. When forming the first resin portion 26 by injection molding, unlike the side portions 12b, 12c, and 12d, the welded portion 24 is not formed on the side portion 12a, so that the tip portions of the plurality of first sealing portions 21 are There is a small gap on the outer surface. Therefore, when the melt flow rate of the first resin part 26 is low, the resin material is not filled into the gap, especially in the side part 12a, and voids are formed at the interface between the first sealing part 21 and the first resin part 26. is likely to occur. In this embodiment, it is possible to suppress the generation of voids also in the side portion 12a.

The linear expansion coefficient of the third resin part 28 is equivalent to the linear expansion coefficient of the second resin part 27. Therefore, the bonding strength between the second resin part 27 and the third resin part 28 is unlikely to decrease due to changes in environmental temperature. Therefore, deterioration in the sealing performance of the sealed body 12 can be suppressed.

Although the electricity storage module 4 according to the embodiment has been described above, the present invention is not limited to the above embodiment.

The metal plate 15 may not be arranged outside the negative terminal electrode 18, and one surface 15a of the metal plate 15 of the negative terminal electrode 18 may be directly connected to the conductive plate 5 or the conductive plate P. The metal plate 15 may not be arranged outside the positive terminal electrode 19, and the other surface 15b of the metal plate 15 of the positive terminal electrode 19 may be directly connected to the conductive plate 5 or the conductive plate P.

The overhang portion 27B extends from the other end of the main body portion 27A in the stacking direction D to the inside of the electrode stack 11, and the overhang portion 28B extends from one end of the main body portion 28A in the stacking direction D to the electrode stack 11. 11 may protrude inside.

The second sealing part 22 does not need to include the third resin part 28. In this case, the first resin portion 26 may have an overhang portion instead of the overhang portion 28B. Alternatively, the second resin portion 27 may have a pair of overhang portions 27B.

The linear expansion coefficients of the second resin part 27 and the third resin part 28 may be different from each other. In this case, the linear expansion coefficient of the second resin part 27 may be larger than the linear expansion coefficient of the first resin part 26 and smaller than the linear expansion coefficient of the third resin part 28. Since the linear expansion coefficient of the sealing body 12 is configured to change in three stages from the inside to the outside, the difference in linear expansion coefficient between each part of the sealing body 12 is further suppressed. Therefore, deterioration in the sealing performance of the sealed body 12 can be further suppressed.

4... Electricity storage module, 11... Electrode laminate (laminate), 12... Sealing body, 14... Bipolar electrode, 15... Metal plate, 15c... Peripheral part, 18... Negative terminal electrode, 19... Positive terminal electrode, 21... First sealing part, 22... Second sealing part, 26... First resin part, 27... Second resin part, 28... Third resin part, V... Internal space.

Claims (4)

a laminate having a plurality of stacked metal plates;
a sealing body for sealing an internal space formed between two adjacent metal plates of the plurality of metal plates,
The plurality of metal plates include a metal plate of a positive terminal electrode, a metal plate of a negative terminal electrode, and a plurality of metal plates of bipolar electrodes provided between the positive terminal electrode and the negative terminal electrode. ,
The sealing body includes a first sealing part having a rectangular annular shape joined to a peripheral edge of the metal plate, and a second sealing part provided around the stacked first sealing part. death,
The second sealing part includes a first resin part provided around the first sealing part, and a second resin part provided around the first resin part,
The difference between the linear expansion coefficient of the first sealing part and the linear expansion coefficient of the first resin part is larger than the difference between the linear expansion coefficient of the first sealing part and the second resin part. small,
In the electricity storage module , the linear expansion coefficient of the first resin part is set between the linear expansion coefficient of the first sealing part and the linear expansion coefficient of the second resin part . The electricity storage module according to claim 1, wherein a linear expansion coefficient of the first resin part is smaller than a linear expansion coefficient of the first sealing part and larger than a linear expansion coefficient of the second resin part. The electricity storage module according to claim 1 or 2, wherein a melt flow rate of the first resin part is higher than a melt flow rate of the second resin part. The second sealing part further includes a third resin part provided around the second resin part,
4. The power storage module according to claim 1, wherein a linear expansion coefficient of the third resin part is the same as a linear expansion coefficient of the second resin part.

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