JP2020053160A - Power storage module - Google Patents

Abstract

To provide a power storage module which can continuously prevent the seepage of an electrolyte due to an alkali creep phenomenon.SOLUTION: A power storage module 4 comprises an electrode laminate 11, a sealing body 12, and an electrolyte containing an alkaline solution. The electrode laminate 11 has a first metal plate 30 which is arranged on the outer side in a lamination direction D with respect to an electrode plate 15 of a negative terminal electrode 18. The sealing body 12 has a frame-like first sealing part 21 which is arranged between a peripheral portion 30c of the first metal plate 30 and a peripheral portion 15c of the electrode plate 15 of the negative terminal electrode 18 in the lamination direction D. An excess space VA is defined by the electrode plate 15 of the negative terminal electrode 18, the first metal plate 30, and the first sealing part 21A. In the excess space VA, a second metal plate 40 is arranged between the first metal plate 30 and the electrode plate 15 of the negative terminal electrode 18.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a power storage module.

  BACKGROUND ART As a conventional power storage module, a bipolar battery including a bipolar electrode in which a positive electrode is formed on one surface of an electrode plate and a negative electrode is formed on the other surface is known (see Patent Document 1). A bipolar battery includes a laminate formed by laminating a plurality of bipolar electrodes with a separator interposed therebetween. A sealing body that seals between the bipolar electrodes adjacent to each other in the stacking direction is provided on a side surface of the stacked body, and the electrolyte is contained in an internal space formed between the bipolar electrodes.

JP 2011-204386 A

  In the above-described power storage module, a negative electrode termination electrode that is disposed at one end in the stacking direction of the stacked body and has a negative electrode formed inside the stacked direction is disposed. The periphery of the electrode plate of the negative terminal electrode is sealed by a sealing body, similarly to other bipolar electrodes. However, when the electrolytic solution contains an alkaline solution, there is a possibility that the electrolytic solution may seep out of the power storage module through the space between the sealing body and the electrode plate of the negative terminal electrode due to a so-called alkaline creep phenomenon.

  The present invention has been made to solve the above-described problem, and has as its object to provide a power storage module capable of continuously suppressing seepage of an electrolytic solution due to an alkaline creep phenomenon.

  An energy storage module according to one aspect of the present invention includes a stacked body including a plurality of stacked bipolar electrodes, an electrode stacked body including a negative electrode terminated at one end in the stacking direction of the stacked body, and an electrode. A sealing body that is provided to surround the side surface of the laminate and forms an internal space between adjacent electrodes and seals the internal space, and an electrolytic solution containing an alkaline solution contained in the internal space, The electrode laminate has a first metal plate disposed outside in the laminating direction with respect to the electrode plate of the negative terminal electrode, and the sealing body has a peripheral portion of the first metal plate and the negative terminal electrode in the laminating direction. A frame-shaped sealing portion disposed between the peripheral portion of the electrode plate and a surplus space formed by the electrode plate of the negative terminal electrode, the first metal plate, and the sealing portion; Inside the first metal plate and the electrode plate of the negative terminal electrode. There has been placed.

  In this power storage module, since the first metal plate is arranged outside the electrode plate of the negative electrode terminal electrode in the laminating direction, an extra space is formed on the movement path of the electrolyte due to the alkali creep phenomenon. By forming the surplus space, it is possible to suppress entry of moisture contained in external air into the gap between the sealing portion and the electrode plate of the negative electrode terminal electrode, which is the starting point of the electrolyte oozing. Thus, the influence of external humidity, which is the condition for accelerating the alkaline creep phenomenon, can be suppressed, and seepage of the electrolyte solution to the outside of the power storage module can be suppressed. Further, in this power storage module, the second metal plate is disposed between the electrode plate of the negative terminal electrode and the first metal plate in the surplus space. The arrangement of the second metal plate restricts the deformation of the first metal plate inward in the stacking direction. As a result, the tensile stress applied to the first metal plate can be reduced, and breakage of the first metal plate due to the tensile stress can be suppressed. By suppressing breakage of the first metal plate, the surplus space is maintained, and the effect of suppressing seepage of the electrolytic solution due to the alkali creep phenomenon can be maintained.

  The thickness of the second metal plate may be equal to or less than the thickness of the sealing portion. The thickness of the second metal plate may be equal to or less than the thickness of the sealing portion. The electrode stack may expand outward in the stacking direction due to an internal pressure fluctuation during charging and discharging of the power storage module. In this case, the second metal plate in the surplus space may expand outward in the stacking direction. Therefore, by setting the thickness of the second metal plate to be equal to or less than the thickness of the sealing portion, deformation of the first metal plate due to expansion of the second metal plate can be suppressed.

  The thickness of the second metal plate may be the same as the thickness of the sealing portion. In this case, the first metal plate forming the surplus space can be substantially flattened. Therefore, the tensile stress applied to the first metal plate can be further reduced.

  On both surfaces of the electrode plate of the bipolar electrode, a coating portion made of an active material layer is provided, and even when the outer edge of the second metal plate is located outside the outer edge of the coating portion when viewed from the laminating direction. Good. In this case, in the surplus space, the volume of the space region excluding the second metal plate can be suppressed, and the amount of water existing in the space region can be suppressed. Thereby, the progress of the alkali creep phenomenon can be suppressed, and the seepage of the electrolytic solution due to the alkali creep phenomenon can be effectively suppressed.

  On both surfaces of the electrode plate of the bipolar electrode, a coating portion of the active material layer is provided, and even when the outer edge of the second metal plate is located inside the outer edge of the coating portion, as viewed from the laminating direction. Good. In this case, it is possible to increase the volume of the space region excluding the second metal plate in the surplus space, and it is possible to suppress an increase in the humidity of the space region due to entry of moisture from the outside. Thereby, formation of a gap between the electrode plate of the negative electrode terminal electrode and the sealing portion can be suppressed, and seepage of the electrolytic solution due to the alkali creep phenomenon can be effectively suppressed.

  The first metal plate may be made of the same material as the electrode plate of the bipolar electrode. In this case, the cost of the power storage module can be reduced by using common materials.

  The second metal plate may be made of the same material as the electrode plate of the bipolar electrode. In this case, the cost of the power storage module can be reduced by using common materials.

  The sealing portion may be respectively coupled to the first metal plate and the electrode plate of the negative terminal electrode. According to this configuration, a two-stage sealing structure is formed on the movement path of the electrolytic solution from the negative terminal electrode to the outside, so that the progress of the alkali creep phenomenon can be effectively suppressed. Further, since the rigidity of the sealing portion is increased by the connection between the first metal plate and the sealing portion, peeling of the sealing portion from the electrode plate of the negative electrode terminal electrode is suppressed. Accordingly, it is possible to suppress the generation of a gap that may be a path for leakage of the electrolyte due to the alkali creep phenomenon, and it is possible to effectively suppress the oozing of the electrolyte.

  At least one of the electrode plate of the negative electrode terminal electrode and the first metal plate may be roughened in a coupling region with the sealing portion. In this case, by the anchor effect, the bonding strength between at least one of the electrode plate of the negative electrode terminal electrode and the first metal plate and the sealing portion can be improved. Therefore, peeling of the sealing portion can be effectively suppressed, and seepage of the electrolytic solution due to the alkali creep phenomenon can be more effectively suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the electrical storage module which can suppress oozing of the electrolyte solution by alkali creep phenomenon continuously is provided.

FIG. 2 is a schematic cross-sectional view illustrating one embodiment of a power storage device. FIG. 2 is a schematic sectional view illustrating an internal configuration of the power storage module illustrated in FIG. 1. FIG. 3 is an enlarged cross-sectional view illustrating a part of the power storage module illustrated in FIG. 2. FIG. 4 is an enlarged cross-sectional view illustrating a part of a power storage module according to a first comparative example. It is an expanded sectional view showing a part of electric storage module concerning a 2nd comparative example. It is an expanded sectional view showing a part of electric storage module concerning a 1st modification. It is an expanded sectional view showing a part of electric storage module concerning a 2nd modification.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements have the same reference characters allotted, and redundant description will not be repeated.

  FIG. 1 is a schematic cross-sectional view illustrating one embodiment of a power storage device. The power storage device 1 shown in FIG. 1 is used as a battery of various vehicles such as a forklift, a hybrid vehicle, and an electric vehicle. The power storage device 1 includes a module stack 2 including a plurality of stacked power storage modules 4 and a restraining member 3 that applies a restraining load to the module stack 2 in the stacking direction of the module stack 2.

  The module stack 2 includes a plurality (three in this embodiment) of power storage modules 4 and a plurality (four in this embodiment) of conductive plates 5. The power storage module 4 is a bipolar battery, and has a substantially 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 is exemplified as the power storage module 4.

  The power storage modules 4 adjacent to each other in the stacking direction are electrically connected 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 and outside the power storage module 4 located at the stacking end. A positive electrode terminal 6 is connected to one conductive plate 5 arranged outside the power storage module 4 located at the lamination end. The negative electrode terminal 7 is connected to the other conductive plate 5 disposed outside the power storage module 4 located at the lamination end. The positive electrode terminal 6 and the negative electrode terminal 7 are drawn out, for example, from the edge of the conductive plate 5 in a direction crossing the laminating direction. The power storage device 1 is charged and discharged by the positive terminal 6 and the negative terminal 7.

  Inside the conductive plate 5, a plurality of flow paths 5a for circulating a refrigerant such as air are provided. The flow path 5a extends, for example, along a direction that intersects (in one example, orthogonally) the laminating direction and the drawing direction of the positive electrode terminal 6 and the negative electrode terminal 7, respectively. The conductive plate 5 functions not only as a connecting member for electrically connecting the power storage modules 4 to each other, but also as a radiator plate for radiating heat generated in the power storage module 4 by circulating a coolant through these flow paths 5a. Has both functions. In the example of FIG. 1, the area of the conductive plate 5 viewed from the stacking direction is smaller than the area of the power storage module 4. However, from the viewpoint of improving heat dissipation, the area of the conductive plate 5 may be the same as the area of the power storage module 4 or may be larger than the area of the power storage module 4.

  The restraining member 3 includes a pair of end plates 8 sandwiching the module stack 2 in the stacking direction, and a fastening bolt 9 and a nut 10 for fastening the end plates 8 to each other. The end plate 8 is a substantially rectangular metal plate having an area slightly larger than the area of the power storage module 4 and the conductive plate 5 as viewed from the stacking direction. A film F having an electrical insulation property is provided on a surface of the end plate 8 on the module laminate 2 side. The film F insulates between the end plate 8 and the conductive plate 5.

  At the edge of the end plate 8, an insertion hole 8 a is provided at a position outside the module laminate 2. The fastening bolt 9 is passed from the insertion hole 8a of the one end plate 8 toward the insertion hole 8a of the other end plate 8, and is provided at the tip of the fastening bolt 9 protruding from the insertion hole 8a of the other end plate 8. , Nut 10 are screwed. As a result, the power storage module 4 and the conductive plate 5 are sandwiched by the end plates 8 to form a unit as the module stack 2, and a binding force is applied to the module stack 2 in the stacking direction.

  Next, the configuration of the power storage module 4 will be described in detail. FIG. 2 is a schematic sectional view showing the internal configuration of the power storage module shown in FIG. As illustrated in FIG. 2, the power storage module 4 includes an electrode stack 11 and a resin sealing body 12 that seals the electrode stack 11. The electrode stack 11 includes a plurality of electrodes stacked along the stacking direction D of the power storage module 4 with the separator 13 interposed therebetween. These electrodes are arranged on a stacked body of a plurality of bipolar electrodes 14, a negative electrode termination electrode 18 arranged on one end side in the stacking direction D of the stacked body, and arranged on the other end side in the stacking direction D of the stacked body. And a positive electrode termination electrode 19.

  The bipolar electrode 14 has an electrode plate 15 including one surface 15a and the other surface 15b opposite to the one surface 15a, and an active material layer-coated portion 20 on both surfaces of the electrode plate 15. The coating section 20 includes a positive electrode 16 provided on one surface 15 a of the electrode plate 15 and a negative electrode 17 provided on the other surface 15 b of the electrode plate 15. The positive electrode 16 is a positive electrode active material layer formed by applying a positive electrode active material to the electrode plate 15. The negative electrode 17 is a negative electrode active material layer formed by applying a negative electrode active material to the electrode 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 one side in the stacking direction D with the separator 13 interposed therebetween. 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 in the stacking direction D with the separator 13 interposed therebetween.

  The negative terminal electrode 18 has the electrode plate 15 and the negative electrode 17 provided on the other surface 15 b of the electrode plate 15. The negative electrode termination electrode 18 is disposed at one end in the stacking direction D such that the other surface 15b faces the inside (center side) of the electrode stack 11 in the stacking direction D. The negative electrode 17 provided on the other surface 15 b of the electrode plate 15 of the negative electrode termination electrode 18 faces the positive electrode 16 of the bipolar electrode 14 at one end in the stacking direction D via the separator 13.

  The positive electrode termination electrode 19 has an electrode plate 15 and a positive electrode 16 provided on one surface 15 a of the electrode plate 15. The positive electrode termination electrode 19 is disposed at the other end in the stacking direction D such that the one surface 15a faces the inside of the electrode stack 11 in the stacking direction D. The positive electrode 16 provided on one surface 15 a of the positive electrode termination electrode 19 faces the negative electrode 17 of the bipolar electrode 14 at the other end in the stacking direction D via the separator 13. The other surface 15 b of the electrode plate 15 of the positive electrode terminal electrode 19 forms the other outer surface of the electrode stack 11 in the stacking direction D, and is electrically connected to the conductive plate 5 adjacent to the power storage module 4.

  The electrode plate 15 is made of, for example, a metal such as nickel or a nickel-plated steel plate. As an example, the electrode plate 15 is a substantially rectangular metal foil made of nickel. The peripheral portion 15c of the electrode plate 15 has a substantially rectangular frame shape, and is an uncoated region where the positive electrode active material and the negative electrode active material are not coated. As a positive electrode active material constituting the positive electrode 16, for example, nickel hydroxide is given. 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 15 b of the electrode plate 15 is slightly larger than the formation region of the positive electrode 16 on the one surface 15 a of the electrode plate 15.

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

  The sealing body 12 is formed, for example, of an insulating resin into a rectangular tube as a whole. The sealing body 12 is provided on the side surface 11 a of the electrode laminate 11 so as to surround the peripheral edge 15 c of the electrode plate 15. The sealing body 12 holds the peripheral part 15c on the side surface 11a. The sealing body 12 surrounds the plurality of first sealing portions 21 coupled to the peripheral edge portion 15c of the electrode plate 15 and the first sealing portion 21 from the outside along the side surface 11a. And a second sealing portion 22 coupled to each of them. The first sealing portion 21 and the second sealing portion 22 are, for example, an insulating resin having alkali resistance. The constituent material of the first sealing portion 21 and the second sealing portion 22 includes, for example, polypropylene (PP), polyphenylene sulfide (PPS), or modified polyphenylene ether (modified PPE).

  The first sealing portion 21 is provided continuously over the entire periphery of the peripheral portion 15c in the electrode plate 15, and has a rectangular frame shape when viewed from the laminating direction D. The first sealing portion 21 is, for example, a film having a predetermined thickness in the stacking direction D. The first sealing portion 21 includes a peripheral portion 15c on one surface 15a of the electrode plate 15 of the bipolar electrode 14 adjacent to each other along the stacking direction D, a peripheral portion 15c on the one surface 15a of the electrode plate 15 of the negative electrode termination electrode 18, In addition, the positive electrode terminal electrode 19 is located at the peripheral edge 15c on one surface 15a and the other surface 15b of the electrode plate 15 respectively. The inside of each of the first sealing portions 21 is, when viewed from the laminating direction D, a peripheral portion 15c on one surface 15a of the electrode plate 15 of the bipolar electrode 14 and a peripheral portion 15c on one surface 15a of the electrode plate 15 of the negative electrode termination electrode 18. And the peripheral edge 15c on the one surface 15a and the other surface 15b of the electrode plate 15 of the positive electrode terminal electrode 19, respectively.

  The inside of the first sealing portion 21 overlapping the peripheral portion 15c of the one surface 15a of the electrode plate 15 is welded to the peripheral portion 15c of the one surface 15a of the electrode plate 15 by, for example, ultrasonic waves or heat, and is airtightly coupled. . The inside of the first sealing portion 21 that overlaps with the peripheral portion 15c of the other surface 15b of the electrode plate 15 of the positive electrode terminal electrode 19 is, for example, ultrasonically or by heat, the peripheral portion 15c of the other surface 15b of the electrode plate 15 of the positive electrode terminal electrode 19. And are hermetically bonded. The outside of the first sealing portion 21 projects outward beyond the outer edge of the electrode plate 15 when viewed in the laminating direction D, and the tip portion is held by the second sealing portion 22. The first sealing portions 21 adjacent to each other along the stacking direction D may be separated from each other or may be in contact with each other.

  The region where the peripheral portion 15c of the one surface 15a of the electrode plate 15 overlaps the first sealing portion 21 and the peripheral portion 15c of the other surface 15b of the electrode plate 15 of the positive electrode terminal electrode 19 and the first sealing portion 21 The overlapping region is a coupling region K between the electrode plate 15 and the first sealing portion 21. In the coupling region K, the surface of each electrode plate 15 is roughened. In the present embodiment, the entirety on one surface 15a of the electrode plate 15 and the entirety of the positive electrode terminal electrode 19 on the other surface 15b of the electrode plate 15 are roughened. However, only the coupling region K on one surface 15a of each electrode plate 15 may be roughened, or only the coupling region K on the other surface 15b of the electrode plate 15 of the positive electrode terminal electrode 19 may be roughened. Good.

  Roughening can be achieved by forming a plurality of protrusions by, for example, electrolytic plating. For example, in the case where one surface 15a of the electrode plate 15 is roughened, a plurality of protrusions are formed on the one surface 15a, so that at the bonding interface between the one surface 15a of the electrode plate 15 and the first sealing portion 21, The resin in a molten state 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 first sealing portion 21 can be improved. The projection formed at the time of roughening has, for example, a shape that becomes tapered from the base end side to the tip end side. Thereby, the cross-sectional shape between the adjacent projections becomes an undercut shape, and the anchor effect can be enhanced.

  The second sealing portion 22 is provided outside the electrode stack 11 and the first sealing portion 21, and forms an outer wall (housing) of the power storage module 4. The second sealing portion 22 is formed, for example, by injection molding of a 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 tubular shape (annular shape) extending in the stacking direction D as an axial direction. The second sealing portion 22 is welded to the outer surface of the first sealing portion 21 by, for example, heat during injection molding.

  The first sealing portion 21 and the second sealing portion 22 form an internal space V between adjacent electrodes and seal the internal space V. More specifically, the second sealing portion 22 is, together with the first sealing portion 21, between the bipolar electrodes 14 adjacent to each other along the stacking direction D, and the negative electrode termination electrodes 18 adjacent to each other along the stacking direction D. And the bipolar electrode 14, and between the positive electrode terminal electrode 19 and the bipolar electrode 14 adjacent to each other along the stacking direction D. Thereby, air-tightly partitioned internal spaces V are formed between the adjacent bipolar electrodes 14, between the negative electrode termination electrode 18 and the bipolar electrode 14, and between the positive electrode termination electrode 19 and the bipolar electrode 14, respectively. ing. The internal space V contains an electrolytic solution (not shown) containing an alkaline solution such as an aqueous potassium hydroxide solution. The electrolyte is impregnated in the separator 13, the positive electrode 16, and the negative electrode 17.

  Next, the configuration around the negative electrode termination electrode 18 will be described in more detail. FIG. 3 is an enlarged view of a main part showing a part of power storage module 4 shown in FIG.

  As shown in FIG. 3, in the electrode stack 11, a first metal plate 30 is further stacked outside the negative electrode termination electrode 18 in the stacking direction D. The first metal plate 30 is made of the same material as the material of the electrode plate 15 of the bipolar electrode 14. That is, the first metal plate 30 is made of, for example, a metal such as nickel or a nickel-plated steel plate. As an example, the first metal plate 30 is a rectangular metal foil made of nickel.

  The first metal plate 30 includes one surface 30a and the other surface 30b opposite to the one surface 30a. The one surface 30a is located outside the electrode stack 11 in the stacking direction D, and the other surface 30b is located inside the electrode stack 11 in the stack direction D. One surface 30a constitutes one outer surface of electrode stack 11 in stacking direction D, and is electrically connected to conductive plate 5 adjacent to power storage module 4. Both the one surface 30a and the other surface 30b are not coated with the positive electrode active material and the negative electrode active material, and the entire surfaces of the one surface 30a and the other surface 30b are uncoated regions. Therefore, in the present embodiment, the first metal plate 30 is an uncoated electrode on which neither the positive electrode 16 nor the negative electrode 17 is provided.

  A peripheral portion 30c of the other surface 30b of the first metal plate 30 is provided with a first sealing portion 21 (hereinafter, referred to as a "first sealing portion 21A") provided on a peripheral portion 15c of the electrode plate 15 of the negative electrode terminal electrode 18. Are welded by, for example, ultrasonic waves or heat, and are hermetically connected. Therefore, one surface of the first sealing portion 21A in the stacking direction D is coupled to the other surface 30b of the first metal plate 30, and the other surface of the first sealing portion 21A in the stacking direction D is It is in a state of being coupled to one surface 15a of electrode plate 15. A first sealing portion 21 (hereinafter, referred to as a “first sealing portion 21B”) is provided on the peripheral portion 30c on the one surface 30a side of the first metal plate 30, similarly to the bipolar electrode 14 and the negative electrode termination electrode 18. ing. The inside of the first sealing portion 21B overlaps with the peripheral portion 30c of the one surface 30a of the first metal plate 30 when viewed from the laminating direction D, and is welded to the peripheral portion 30c by, for example, ultrasonic waves or heat, and is airtight. Is joined to.

  In the peripheral portion 30c of the first metal plate 30, a region where the one surface 30a and the first sealing portion 21B overlap and a region where the other surface 30b and the first sealing portion 21A overlap each other are the first metal plate 30 and the first sealing portion 21A. It is a coupling region K with one sealing portion 21A, 21B. One surface 30a and the other surface 30b of the first metal plate 30 are roughened similarly to the one surface 15a of the electrode plate 15. In the present embodiment, the whole of one surface 30a and the other surface 30b is roughened. However, only the coupling region K on one surface 30a and the other surface 30b may be roughened.

  In the electrode stack 11, a surplus space VA in which no electrolytic solution is accommodated is formed between the first metal plate 30 and the negative electrode terminal electrode 18. The surplus space VA is surrounded by one surface 15a of the electrode plate 15 of the negative terminal electrode 18, the other surface 30b of the first metal plate 30, and the inner edge 21a of the first sealing portion 21A. When viewed from a cross section along the stacking direction D, the surplus space VA has a substantially rectangular shape.

  The second metal plate 40 is disposed in the surplus space VA. Specifically, the second metal plate 40 is located inside the first sealing portion 21 </ b> A in the surplus space VA, and is connected to one surface 15 a of the electrode plate 15 of the negative electrode terminal electrode 18 and the other of the first metal plate 30. It is arranged between the direction 30b. The second metal plate 40 is made of, for example, a metal having alkali resistance. As a constituent material of the second metal plate 40, for example, nickel, a nickel-plated steel plate, or a stainless steel plate (SUS) is used. In the present embodiment, the second metal plate 40 is made of the same material as the material of the electrode plate 15 of the bipolar electrode 14. That is, the second metal plate 40 is made of a highly conductive metal such as nickel or a nickel-plated steel plate. As an example, the second metal plate 40 is a rectangular metal plate made of nickel.

  The second metal plate 40 includes one surface 40a and the other surface 40b opposite to the one surface 40a. One surface 40a faces the other surface 30b of first metal plate 30, and the other surface 40b faces one surface 15a of electrode plate 15 of negative electrode terminal electrode 18. In the present embodiment, one surface 40a is in contact with the other surface 30b of the first metal plate 30, and the other surface 40b is in contact with one surface 15a of the electrode plate 15 of the negative electrode terminal electrode 18. The first metal plate is formed by contact between one surface 40a of the second metal plate 40 and the other surface 30b of the first metal plate 30 and between the other surface 40b of the second metal plate 40 and one surface 15a of the electrode plate 15. 30 and the electrode plate 15 of the negative terminal electrode 18 are electrically connected via the second metal plate 40. In the present embodiment, one surface 40a of the second metal plate 40 is not connected to the other surface 30b of the first metal plate 30, and the other surface 40b of the second metal plate 40 is connected to the one surface 15a of the electrode plate 15. Not combined with However, one surface 40a may be coupled to the other surface 30b, and the other surface 40b may be coupled to the one surface 15a.

  The thickness T1 of the second metal plate 40 in the stacking direction D (that is, the distance between the one surface 40a and the other surface 40b) is equal to or less than the thickness T2 of the first sealing portion 21A in the stacking direction D. In the present embodiment, the thickness T1 of the second metal plate 40 is the same as the thickness T2 of the first sealing portion 21A. The thickness T1 of the second metal plate 40 is, for example, not less than 150 μm and not more than 200 μm. The second metal plate 40 having the same thickness T1 as the thickness T2 of the first sealing portion 21A is disposed between the electrode plate 15 of the negative terminal electrode 18 and the first metal plate 30, so that The position (height) of the central portion 30d of the first metal plate 30 in the stacking direction D and the position (height) of the peripheral portion 30c of the first metal plate 30 in the stacking direction D are aligned. Thereby, the first metal plate 30 is substantially flattened.

  When viewed from the laminating direction D, the dimension S1 of the second metal plate 40 is larger than the dimension S2 of the coating portion 20 of the bipolar electrode 14 (specifically, the dimension of the negative electrode 17). When viewed from the lamination direction D, the centers of the second metal plate 40 and the bipolar electrode 14 are substantially coincident with each other. Therefore, the outer edge 40c of the second metal plate 40 is located outside the outer edge 20a of the coating portion 20 of the bipolar electrode 14 (specifically, the outer edge of the negative electrode 17). The outer edge 40c of the second metal plate 40 is located inside the inner edge 21a of the first sealing portion 21A when viewed from the laminating direction D. In the present embodiment, the outer edges 20a of the coating portions 20 of the respective bipolar electrodes 14 substantially coincide with each other when viewed from the laminating direction D.

  The dimension S1 of the second metal plate 40 can be changed as appropriate. The change in the dimension S1 of the second metal plate 40 (that is, the size of the area of the second metal plate 40) affects the volume of the space region excluding the second metal plate 40 in the surplus space VA. Specifically, the volume of the space region increases as the size S1 of the second metal plate 40 decreases, and the volume of the space region decreases as the size S1 of the second metal plate 40 increases. Therefore, by adjusting the size S1 of the second metal plate 40, the volume of the surplus space VA in the space region can be easily controlled.

  Next, an example of a method for manufacturing the power storage module 4 will be described. The method for manufacturing the power storage module 4 includes a primary molding step, a lamination step, a secondary molding step, and an injection step. In the primary forming step, a predetermined number of bipolar electrodes 14, a negative electrode termination electrode 18, a positive electrode termination electrode 19, a first metal plate 30, a second metal plate 40, and a first sealing portion 21 are prepared. Then, the first sealing portion 21 is welded to the peripheral portion 15c of the one surface 15a of each electrode plate 15 and the peripheral portion 15c of the one surface 15a of the electrode plate 15 of the positive terminal electrode 19, respectively. Further, the first sealing portion 21B is welded to the peripheral portion 30c of the one surface 30a of the first metal plate 30.

  Thereafter, the negative electrode termination electrode 18 and the first metal plate 30 are connected so that the other surface 30b of the first metal plate 30 and the one surface 15a of the electrode plate 15 of the negative electrode termination electrode 18 face each other along the stacking direction D. Are stacked in the stacking direction D. At this time, the second metal plate 40 is disposed between the first metal plate 30 and the negative electrode termination electrode 18 inside the first sealing portion 21A welded to the negative electrode termination electrode 18. Between the first metal plate 30 and the negative electrode terminal electrode 18, one surface 40 a of the second metal plate 40 is in contact with the other surface 30 b of the first metal plate 30, and the other surface 40 b is the electrode plate 15 of the negative electrode terminal electrode 18. Contacts one surface 15a of the first member.

  After that, the first sealing portion 21A welded to the negative electrode terminal electrode 18 is welded to the peripheral portion 30c of the other surface 30b of the first metal plate 30. Accordingly, one surface of the first sealing portion 21A in the stacking direction D is welded to the peripheral portion 30c of the other surface 30b of the first metal plate 30, and the other surface of the first sealing portion 21A is The electrode plate 15 is welded to the peripheral portion 15c of the one surface 15a. In this manner, a negative electrode assembly in which the first metal plate 30 and the negative electrode termination electrode 18 are combined with the second metal plate 40 disposed between the first metal plate 30 and the negative electrode termination electrode 18 is formed. You.

  In the laminating step, the positive electrode terminal electrode 19, the bipolar electrode 14, and the negative electrode assembly are laminated along the laminating direction D with the separator 13 interposed therebetween, thereby forming the electrode laminated body 11 including the first sealing portion 21. In the secondary molding step, after disposing the electrode laminate 11 including the first sealing portion 21 in a mold (not shown) for injection molding, the molten resin is injected into the mold to form the electrode laminate. The second sealing part 22 is formed so as to surround the first sealing part 11 and the first sealing part 21. Thereby, the sealing body 12 is formed on the side surface 11a of the electrode laminate 11. In the injection step, an electrolyte is injected into the internal space V between the bipolar electrodes 14 after the secondary molding step. Thereby, the power storage module 4 is obtained.

  Next, the operation and effect of the power storage module 4 will be described together with the problems of the comparative example. FIG. 4 is an enlarged cross-sectional view illustrating a part of the power storage module 100 according to the first comparative example. As shown in FIG. 4, in the power storage module 100 according to the first comparative example, the first metal plate 30 is not included in the electrode stack 11, and the second metal plate 40 is not disposed in the surplus space VA. This is different from the power storage module 4 according to the present embodiment.

  In the power storage module 100, the electrolytic solution present in the internal space V is transmitted along the surface of the electrode plate 15 of the negative electrode terminal electrode 18 due to the so-called alkali creep phenomenon, and between the electrode plate 15 and the first sealing portion 21A in the coupling region K. May ooze out to the one surface 15a side of the electrode plate 15 through the gap. In FIG. 4, the traveling path of the electrolytic solution L in the alkaline creep phenomenon is indicated by an arrow A. The alkaline creep phenomenon may occur at the time of charging and discharging of the power storage device and at the time of no load due to electrochemical factors and fluid phenomena. The alkali creep phenomenon occurs due to the existence of the paths of the negative electrode potential, moisture, and the electrolyte solution L, respectively, and progresses with the passage of time.

  The alkali creep phenomenon can also occur when one surface 15a of the electrode plate 15 in the bonding region K is roughened. Even when the bonding strength between the electrode plate 15 and the first sealing portion 21A is enhanced by the roughening, the electrolytic solution L is not removed from the plurality of protrusions formed on the one surface 15a of the electrode plate 15 and the first sealing portion. The resin may be peeled off from the electrode plate 15 when passing between the resin constituting the stop portion 21A. Also, when the internal pressure increases due to the hydrogen gas generated by the self-discharge reaction of the negative electrode active material (for example, a hydrogen storage alloy), and when the generated stress due to the internal pressure exceeds the breaking stress of the resin, the resin is broken and It is also conceivable that swelling occurs in one sealing portion 21A.

  FIG. 5 is an enlarged cross-sectional view illustrating a part of the power storage module 200 according to the second comparative example. As shown in FIG. 5, in the power storage module 200 according to the second comparative example, in addition to the configuration of the power storage module 100 described above, a first metal plate is disposed outside the electrode plate 15 of the negative terminal electrode 18 in the stacking direction D. 30 are arranged.

  In the power storage module 200, the first metal plate 30 is disposed outside the electrode plate 15 of the negative electrode terminal electrode 18 in the stacking direction D, so that an excess space VA is formed on the movement path of the electrolytic solution due to the alkali creep phenomenon. Is done. Due to the formation of the surplus space VA, the moisture contained in the external air is provided in the gap between the electrode plate 15 of the negative electrode terminal electrode 18 and the first sealing portion 21A, which is a starting point for the electrolyte to seep out. Can be suppressed from entering. Thus, the influence of external humidity, which is a condition for accelerating the alkaline creep phenomenon, can be suppressed, and seepage of the electrolyte solution to the outside of the power storage module 200 can be suppressed.

  In the power storage module 200, when the module stack 2 is restrained by the restraining member 3, the first metal plate 30 may be deformed by a restraining force applied inside the stacking direction D of the power storage module 200. Specifically, the central portion 30d which is not coupled to the first sealing portion 21A and is located far from the peripheral portion 30c is located on the inner side in the stacking direction D with respect to the peripheral portion 30c coupled to the first sealing portion 21A. It is conceivable that the displacement is large. When the first metal plate 30 is deformed in this way, the central portion 30d of the first metal plate 30 is depressed toward the electrode plate 15 side of the negative electrode termination electrode 18 while the one surface 15a of the electrode plate 15 of the negative electrode termination electrode 18 is kept. Contact By this contact, the electrode plate 15 of the negative terminal electrode 18 and the conductive plate 5 disposed outside the negative terminal electrode 18 are electrically connected via the first metal plate 30.

  However, in the power storage module 200, when the first metal plate 30 is deformed as described above, the first metal plate 30 is damaged due to tensile stress applied to the boundary between the peripheral portion 30c and the central portion 30d of the first metal plate 30. There is a risk of doing it. When the first metal plate 30 is damaged, the excess space cannot be maintained, and the effect of suppressing the seepage of the electrolytic solution due to the alkali creep phenomenon may not be maintained.

  On the other hand, in the power storage module 4, in addition to the configuration of the power storage module 200, a configuration in which the second metal plate 40 is disposed between the electrode plate 15 of the negative terminal electrode 18 and the first metal plate 30 in the surplus space VA. It has become. The disposition of the second metal plate 40 restricts the deformation of the first metal plate 30 inward in the stacking direction D. Specifically, in the first metal plate 30, displacement of the central portion 30d with respect to the peripheral portion 30c inward in the stacking direction D is restricted. As a result, the tensile stress applied to the boundary between the peripheral portion 30c and the central portion 30d in the first metal plate 30 can be reduced, and the damage of the first metal plate 30 due to the tensile stress can be suppressed. By suppressing the damage of the first metal plate 30, the surplus space VA is maintained, and the effect of suppressing the seepage of the electrolytic solution due to the alkali creep phenomenon can be maintained.

  In the power storage module 4, the thickness T1 of the second metal plate 40 is equal to or less than the thickness T2 of the first sealing portion 21A. The electrode stack 11 may expand outward in the stacking direction D due to an internal pressure fluctuation during charging and discharging of the power storage module 4. In this case, the second metal plate 40 in the surplus space VA may expand outward in the stacking direction D. Therefore, by setting the thickness of the second metal plate 40 to be equal to or less than the thickness of the first sealing portion 21A, the deformation of the first metal plate 30 due to the expansion of the second metal plate 40 can be suppressed.

  In the power storage module 4, the thickness T1 of the second metal plate 40 is the same as the thickness T2 of the first sealing portion 21A. In this case, the first metal plate 30 forming the surplus space VA can be substantially flattened. Therefore, the tensile stress applied to the first metal plate 30 can be further reduced.

  In the power storage module 4, the outer edge 40 c of the second metal plate 40 is located outside the outer edge 20 a of the coating unit 20 when viewed from the stacking direction D. In this case, in the surplus space VA, the volume of the space region excluding the second metal plate 40 can be suppressed, and the amount of moisture existing in the space region can be suppressed. Thereby, the progress of the alkali creep phenomenon can be suppressed, and the seepage of the electrolytic solution due to the alkali creep phenomenon can be effectively suppressed.

  Further, in power storage module 4, first metal plate 30 is formed of the same material as electrode plate 15 of bipolar electrode 14. In this case, the cost of the power storage module 4 can be reduced by using a common material.

  In the power storage module 4, the second metal plate 40 is made of the same material as the electrode plate 15 of the bipolar electrode 14. In this case, similarly to the first metal plate 30, the cost of the power storage module 4 can be reduced by using a common material.

  In the power storage module 4, the first sealing portion 21 </ b> A is joined to the first metal plate 30 and the electrode plate 15 of the negative terminal electrode 18, respectively. According to this configuration, a two-stage sealing structure is formed on the moving path of the electrolytic solution from the negative electrode terminal electrode 18 to the outside, so that the progress of the alkali creep phenomenon can be effectively suppressed. Furthermore, since the rigidity of the first sealing portion 21A is increased by joining the first metal plate 30 and the first sealing portion 21A, peeling of the first sealing portion 21A from the electrode plate 15 of the negative electrode terminal electrode 18 is prevented. Can be suppressed. Accordingly, it is possible to suppress the generation of a gap that may be a path for leakage of the electrolyte due to the alkali creep phenomenon, and it is possible to effectively suppress the oozing of the electrolyte.

  In the power storage module 4, both the electrode plate 15 of the negative electrode terminal electrode 18 and the first metal plate 30 are roughened in the coupling region K with the first sealing portion 21A. In this case, the bonding strength between both the electrode plate 15 of the negative electrode terminal electrode 18 and the first metal plate 30 and the first sealing portion 21A can be improved by the anchor effect. Therefore, the peeling of the first sealing portion 21A can be effectively suppressed, and the seepage of the electrolytic solution due to the alkali creep phenomenon can be more effectively suppressed.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to said Embodiment, Various changes can be performed. For example, various modifications shown in FIGS. 6 and 7 may be adopted.

  FIG. 6 is an enlarged cross-sectional view illustrating a part of the power storage module 4 according to the first modification. The difference between the first modification and the above embodiment is the thickness of the second metal plate 40. That is, in the above embodiment, the thickness T1 of the second metal plate 40 is the same as the thickness T2 of the first sealing portion 21A, but in the present modification, the thickness T1 of the second metal plate 40 is It is smaller than the thickness T2 of one sealing portion 21A. Accordingly, the position (height) of the central portion 30d of the first metal plate 30 in the stacking direction D is higher than the position (height) of the peripheral portion 30c of the first metal plate 30 in the stacking direction D. 2 It is shifted to the metal plate 40 side. As a result, the central portion 30d of the first metal plate 30 is in contact with the one surface 40a of the second metal plate 40 in a state of being depressed toward the second metal plate 40.

  The electrode stack 11 may expand outward in the stacking direction D due to an internal pressure fluctuation or the like during charging and discharging of the power storage module 4. When the electrode stack 11 expands, the second metal plate 40 in the surplus space VA may expand outward in the stacking direction D in accordance with the expansion of the electrode stack 11. Therefore, the thickness T1 of the second metal plate 40 is set to be smaller than the thickness T2 of the first sealing portion 21A in advance in consideration of the expansion amount of the second metal plate 40, thereby expanding the second metal plate 40. The deformation of the first metal plate 30 due to the above can be effectively suppressed.

  FIG. 7 is an enlarged cross-sectional view illustrating a part of a power storage module 4 according to a second modification. The difference between the second modified example and the above embodiment is the size of the second metal plate 40 viewed from the lamination direction D. In the above embodiment, the dimension S1 of the second metal plate 40 is larger than the dimension S2 of the coating portion 20 of the bipolar electrode 14 when viewed from the lamination direction D. However, in the present modification, the dimension S1 of the second metal plate 40 is smaller than the dimension S2 of the coating section 20 when viewed from the laminating direction D. Here, the centers of the second metal plate 40 and the bipolar electrode 14 are substantially the same as viewed from the laminating direction D as in the above-described embodiment. Therefore, in the present modification, the outer edge 40c of the second metal plate 40 is located inside the outer edge 20a of the coating portion 20 of the bipolar electrode 14.

  By reducing the dimension S1 of the second metal plate 40 in this manner, it is possible to increase the volume of a space region excluding the second metal plate 40 in the surplus space VA. This makes it possible to suppress an increase in the humidity of the space area due to the entry of moisture from the outside. As a result, formation of a gap between the first sealing portion 21A and the electrode plate 15 of the negative electrode terminal electrode 18 can be suppressed, and seepage of the electrolytic solution due to the alkali creep phenomenon can be effectively suppressed.

  The present invention is capable of various other modifications. For example, the above-described embodiments and the respective modifications may be combined with each other according to necessary purposes and effects. Further, the shape, material, and arrangement of the second metal plate can be appropriately changed. For example, the thickness of the second metal plate may be larger than the thickness of the first sealing portion. When viewed from the lamination direction, the centers of the second metal plate and the bipolar electrode may be shifted from each other. The material of the second metal plate may be made of a material different from the material of the electrode plate of the bipolar electrode. Similarly, the material of the first metal plate may be made of a material different from the material of the electrode plate of the bipolar electrode. The second metal plate may be a single metal plate, or may be divided into a plurality of sheets in the thickness direction or the in-plane direction.

  Further, in the above-described embodiment, one surface and the other surface of the first metal plate are joined to each of the adjacent first sealing portions by welding. However, only one of the one surface and the other surface of the first metal plate may be coupled to the first sealing portion, and both the one surface and the other surface of the first metal plate are coupled to the first sealing portion. It does not need to be done. In the above-described embodiment, both the surface of the first metal plate and the surface of the electrode plate are roughened. However, only one of the surface of the first metal plate and the surface of the electrode plate may be roughened, and neither the surface of the first metal plate nor the surface of the electrode plate may be roughened.

  DESCRIPTION OF SYMBOLS 4 ... Electric storage module, 11 ... Electrode laminated body, 11a ... Side surface, 12 ... Sealing body, 14 ... Bipolar electrode, 15 ... Electrode plate, 15c ... Peripheral part, 18 ... Negative terminal electrode, 19 ... Positive terminal electrode, 20 ... Coating part, 20a outer edge, 21, 21A, 21B first sealing part, 21a inner edge, 22 second sealing part, 30 first metal plate, 30c peripheral part, 40 second metal plate 40c: outer edge, D: stacking direction, K: coupling region, S1, S2: dimensions, T1, T2: thickness, V: internal space, VA: surplus space.

Claims (9)

A stacked body in which a plurality of bipolar electrodes are stacked, and an electrode stacked body including a negative electrode termination electrode disposed at one end in the stacking direction of the stacked body,
A sealing body provided so as to surround the side surface of the electrode laminate, forming an internal space between adjacent electrodes and sealing the internal space,
And an electrolytic solution containing an alkaline solution contained in the internal space,
The electrode laminate includes a first metal plate disposed outside the electrode plate of the negative terminal electrode in the laminating direction,
The sealing body has a frame-shaped sealing portion disposed between a peripheral portion of the first metal plate and a peripheral portion of the electrode plate of the negative terminal electrode in the laminating direction,
An extra space is formed by the electrode plate of the negative electrode terminal electrode, the first metal plate, and the sealing portion,
The power storage module, wherein a second metal plate is disposed between the first metal plate and the electrode plate of the negative terminal electrode in the surplus space.   The power storage module according to claim 1, wherein a thickness of the second metal plate is equal to or less than a thickness of the sealing portion.   The power storage module according to claim 2, wherein a thickness of the second metal plate is the same as a thickness of the sealing portion. On both surfaces of the electrode plate of the bipolar electrode, a coating portion with an active material layer is provided,
The power storage module according to any one of claims 1 to 3, wherein an outer edge of the second metal plate is located outside an outer edge of the coating portion when viewed from the stacking direction. On both surfaces of the electrode plate of the bipolar electrode, a coating portion with an active material layer is provided,
The power storage module according to any one of claims 1 to 3, wherein an outer edge of the second metal plate is located inside an outer edge of the coating portion when viewed from the stacking direction.   The power storage module according to claim 1, wherein the first metal plate is made of the same material as an electrode plate of the bipolar electrode.   The power storage module according to claim 1, wherein the second metal plate is made of the same material as an electrode plate of the bipolar electrode.   The power storage module according to any one of claims 1 to 7, wherein the sealing unit is coupled to the first metal plate and the electrode plate of the negative terminal electrode, respectively.   The power storage module according to claim 8, wherein at least one of the electrode plate of the negative electrode terminal electrode and the first metal plate is roughened in a region where the electrode plate is connected to the sealing portion.

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