JP6989436B2 - Power storage module - Google Patents

Description

The present invention relates to a power storage module.

As a conventional power storage module, a so-called bipolar type power storage module having a bipolar electrode having a positive electrode formed on one surface of an electrode plate and a negative electrode formed on the other surface is known (see Patent Document 1). Such a power storage module includes a laminate formed by laminating a plurality of bipolar electrodes. On the side surface of the laminated body, a resin group for sealing between the bipolar electrodes adjacent to each other in the laminated direction is provided. The electrolytic solution is housed in the internal space formed between the adjacent bipolar electrodes.

Japanese Unexamined Patent Publication No. 2005-5163

In the power storage module described in Patent Document 1, liquid tightness is ensured by sealing the internal space formed between adjacent bipolar electrodes with a resin member in order to prevent leakage of the electrolytic solution and the like. On the other hand, as a phenomenon peculiar to a battery using an alkaline aqueous solution, leakage of an electrolytic solution from the negative electrode (alkali creep) is known. One of the factors for advancing alkaline creep is that a driving force for drawing the electrolytic solution into the potential of the negative electrode is generated through a minute gap formed between the resin member and the metal electrode plate.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a power storage module capable of suppressing the progress of alkaline creep.

The power storage module according to one aspect of the present invention is separated by a bipolar electrode including an electrode plate, a positive electrode having a positive electrode active material layer on one surface of the electrode plate, and a negative electrode having a negative electrode active material layer on the other surface of the electrode plate. At both ends of the laminated body, the positive electrode side terminal electrode and the electrode plate are laminated so that the positive electrode active material layer provided on one surface of the electrode plate faces the inside of the laminated body. The negative electrode side terminal electrode, in which the negative electrode active material layer provided on the other surface of the electrode is laminated so as to face the inside of the laminated body, is laminated, and an insulating portion containing metal in the composition is frame-shaped on the edge of the electrode plate. Is formed in.

According to this configuration, by providing an insulating portion containing a metal in the composition at the edge of the electrode plate, a drive for drawing the electrolytic solution that has entered the minute gap formed between the electrode plate and the resin member into the potential of the negative electrode. It is possible to reduce the force. Therefore, the progress of alkaline creep can be suppressed.

The insulating portion may be formed at the end portion of the electrode plate so as to be along the laminating direction of the laminated body. This makes it possible to more reliably reduce the driving force that draws the electrolytic solution into the potential of the negative electrode.

The insulating portion is formed in a frame shape on the surface of the electrode plate and from the end portion of the electrode plate to the outer edge portion of the other surface of the electrode plate, and the area of the separator is the negative electrode active material when viewed from the stacking direction of the laminated body. It may be larger than the area of the layer. This makes it possible to more reliably reduce the driving force that draws the electrolytic solution into the potential of the negative electrode.

The insulating portion may be formed in the uncoated region of the negative electrode active material layer on the other surface of the electrode plate. In this case, it is possible to prevent a short circuit due to contact between adjacent electrode plates in the uncoated area.

The insulating portion may be a portion where the metal is rusted. In this case, since the insulating portion can be formed by rusting the metal, the cost can be reduced.

According to this power storage module, the progress of alkaline creep can be suppressed.

It is a schematic sectional drawing which shows one Embodiment of the power storage device including the power storage module. It is a schematic sectional drawing which shows one Embodiment of a power storage module. It is an enlarged sectional view of the main part of a power storage module. It is an enlarged sectional view of the main part of the other embodiment of a power storage module. It is an enlarged sectional view of the main part of the other embodiment of a power storage module. It is an enlarged sectional view of the main part of the other embodiment of a power storage module.

Hereinafter, a preferred embodiment of the power storage module according to one aspect of the present invention will be described in detail with reference to the drawings. In the description, the same code will be used for the same element or the element having the same function, and duplicate description will be omitted.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a power storage device. The power storage device 10 shown in FIG. 1 is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 10 includes a power storage module stack 12a in which a plurality of power storage modules 12 are laminated, and a restraint member 16 that applies a restraining load to the power storage module stack 12a in the stacking direction.

The power storage device 10 includes a plurality of (three in this embodiment) power storage modules 12, but may include a single power storage module 12. The power storage module 12 is, for example, a bipolar battery. The power storage module 12 is a secondary battery such as a nickel hydrogen secondary battery or a lithium ion secondary battery, but may be an electric double layer capacitor. In the following description, a nickel-metal hydride secondary battery will be illustrated.

The storage modules 12, 12 adjacent to each other in the stacking direction D1 (Z direction) are electrically connected to each other via the conductive plate 14. Seen from the stacking direction D1, the power storage module 12 and the conductive plate 14 have, for example, a rectangular shape. The conductive plates 14 are arranged between the power storage modules 12 and 12 adjacent to each other in the stacking direction D1 and outside the power storage modules 12 located at the stacking ends, respectively.

A positive electrode terminal 24 is connected to one of the conductive plates 14 arranged outside the power storage module 12 located at the laminated end. The negative electrode terminal 26 is connected to the other conductive plate 14 arranged outside the power storage module 12 located at the laminated end. The positive electrode terminal 24 and the negative electrode terminal 26 are drawn out from the edge of the conductive plate 14, for example, in a direction orthogonal to the stacking direction D1. The positive electrode terminal 24 and the negative electrode terminal 26 charge and discharge the power storage device 10.

Inside each conductive plate 14, a plurality of flow paths 14a through which a refrigerant such as air flows are provided. Each flow path 14a extends in parallel with each other in a direction orthogonal to, for example, the stacking direction D1 and the drawing direction of the positive electrode terminal 24 and the negative electrode terminal 26. By circulating the refrigerant through these flow paths 14a, the conductive plate 14 functions as a connecting member for electrically connecting the power storage modules 12 and 12 to each other, and also dissipates heat generated by the power storage module 12. It also has the function of. In the example of FIG. 1, the area of the conductive plate 14 seen from the stacking direction D1 is smaller than the area of the power storage module 12, but from the viewpoint of improving heat dissipation, the area of the conductive plate 14 is the area of the power storage module 12. It may be the same as the area, or may be larger than the area of the power storage module 12.

The power storage device 10 may include a restraint member 16 that restrains the alternately stacked power storage modules 12 and the conductive plates 14 in the stacking direction D1. The restraint member 16 includes a pair of restraint plates 16A and 16B and a connecting member (bolt 18 and nut 20) that connects the restraint plates 16A and 16B to each other. An insulating film 22 such as a resin film is arranged between the restraint plates 16A and 16B and the conductive plate 14. Each of the restraint plates 16A and 16B is made of a metal such as iron. Seen from the stacking direction D1, each of the restraint plates 16A and 16B and the insulating film 22 has, for example, a rectangular shape.

The insulating film 22 seen from the stacking direction D1 covers the conductive plate 14, and the area of the insulating film 22 seen from the stacking direction D1 is larger than the area of the conductive plate 14. Further, the restraint plates 16A and 16B seen from the stacking direction D1 cover the power storage module 12, and the area of the restraint plates 16A and 16B seen from the stacking direction D1 is larger than the area of the power storage module 12. ..

When viewed from the stacking direction D1, an insertion hole H1 through which the shaft portion of the bolt 18 is inserted is provided at a position outside the power storage module 12 at the edge portion of the restraint plate 16A. Similarly, when viewed from the stacking direction D1, an insertion hole H2 through which the shaft portion of the bolt 18 is inserted is provided at a position outside the power storage module 12 at the edge portion of the restraint plate 16B. When the restraint plates 16A and 16B have a rectangular shape when viewed from the stacking direction D1, the insertion holes H1 and the insertion holes H2 are located at the corners of the restraint plates 16A and 16B.

One restraint plate 16A is abutted against the conductive plate 14 connected to the negative electrode terminal 26 via the insulating film 22, and the other restraint plate 16B has the insulating film 22 attached to the conductive plate 14 connected to the positive electrode terminal 24. It is struck through. For example, the bolt 18 is passed through the insertion hole H1 from one restraint plate 16A side toward the other restraint plate 16B side, and a nut 20 is screwed into the tip of the bolt 18 protruding from the other restraint plate 16B. There is. As a result, the insulating film 22, the conductive plate 14, and the power storage module 12 are sandwiched and unitized, and a restraining load is applied to the stacking direction D1.

FIG. 2 is a schematic cross-sectional view showing a power storage module constituting the power storage device of FIG. FIG. 3 is an enlarged cross-sectional view of a main part of the power storage module. Specifically, FIG. 3 shows one side in the X direction (left side in the drawing of FIG. 2) of the outer edge portions (each of the upper edge portion and the lower edge portion) in the stacking direction D1 of the laminated body constituting the power storage module. It is the figure which enlarged and showed the part of. In FIG. 2, which shows the schematic configuration of the power storage module, the detailed configuration of the outer edge portion of the laminated body is not shown.

As shown in FIGS. 2 and 3, the power storage module 12 includes an electrode laminate 30 in which a plurality of bipolar electrodes 32 are laminated. The electrode laminate 30 has, for example, a rectangular shape when viewed from the stacking direction D1 of the bipolar electrodes 32. A separator 40 may be arranged between adjacent bipolar electrodes 32. The bipolar electrode 32 includes an electrode plate 34, a positive electrode 36 provided on one surface 34a of the electrode plate 34, and a negative electrode 38 provided on the other surface 34b of the electrode plate 34.

In the electrode laminate 30, the positive electrode 36 of one bipolar electrode 32 faces the negative electrode 38 of one of the bipolar electrodes 32 adjacent to each other in the stacking direction D1 with the separator 40 interposed therebetween, and the negative electrode 38 of one bipolar electrode 32 is a separator. It faces the positive electrode 36 of the other bipolar electrode 32 adjacent to each other in the stacking direction D1 with 40 in between.

In the stacking direction D1, an electrode plate 34 (negative electrode side terminal electrode 39) in which a negative electrode 38 is arranged on an inner side surface is arranged at one end of the electrode laminated body 30. Further, at the other end of the electrode laminate 30, an electrode plate 34 (positive electrode side terminal electrode 37) in which a positive electrode 36 is arranged on an inner side surface is arranged. The negative electrode active material layer of the negative electrode side terminal electrode 39 faces the positive electrode active material layer of the uppermost bipolar electrode 32 via the separator 40. The positive electrode active material layer of the positive electrode side terminal electrode 37 faces the negative electrode active material layer of the lowermost bipolar electrode 32 via the separator 40. The electrode plates 34 of these terminal electrodes are connected to adjacent conductive plates 14 (see FIG. 1).

Further, the power storage module 12 includes a frame body 50 which is a sealing member for sealing the electrode laminated body 30. The frame body 50 holds the edge portion 34c of the electrode plate 34 on the side surface 30a of the electrode laminated body 30 extending in the stacking direction D1. The frame body 50 is provided around the electrode laminated body 30 when viewed from the stacking direction D1, and is configured to surround the side surface 30a of the electrode laminated body 30. Further, the frame body 50 is configured to hold the edge portions 34c of the plurality of electrode plates 34. The frame body 50 is, for example, a sealing member formed of an insulating resin. Examples of the resin material constituting the frame 50 include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), and the like.

The frame body 50 includes a first resin portion 52 provided in a frame shape on the edge portion 34c, and a frame-shaped second resin portion 54 provided around the first resin portion 52 and accommodating the electrode laminate 30. Have. The first resin portion 52 is a film having a predetermined thickness (length in the stacking direction D1). The first resin portion 52 has a rectangular frame shape when viewed from the stacking direction D1, and is continuously welded over the entire circumference of the edge portion 34c by, for example, ultrasonic waves or heat. The first resin portion 52 is provided on the edge portion 34c on the one side 34a (here, the surface on which the positive electrode 36 is formed) side of the electrode plate 34. The first resin portion 52 is provided apart from the positive electrode 36 and the negative electrode 38 when viewed from the stacking direction D1. The outer edge portion of the first resin portion 52 and the inner wall surface of the second resin portion 54 are in contact with each other.

As shown in FIG. 3, the first resin portion 52 has a first portion 52a and a second portion 52b. The first portion 52a is provided on one surface 34a and overlaps with the electrode plate 34 when viewed from the stacking direction D1. The second portion 52b is integrally formed with the first portion 52a and is provided on the outside of the electrode plate 34 when viewed from the stacking direction D1. The thickness of the first portion 52a is thinner than the thickness of the second portion 52b, which is equal to or greater than the thickness of the positive electrode active material layer, but may be equal to or greater than that of the positive electrode active material layer. A stepped surface 52c extending in the stacking direction D1 is formed between the first portion 52a and the second portion 52b.

In FIG. 3, the outer edge portion of the separator 40 is arranged on the upper surface of the first portion 52a. Seen from the stacking direction D1, the first portion 52a and the outer edge portion of the separator 40 overlap each other. The outer edge portion of the separator 40 is fixed to the upper surface of the first portion 52a at a plurality of locations arranged along the outer edge of the separator 40, for example, by welding. The outer edge portion of the separator 40 may be in contact with the stepped surface 52c or may be separated from the stepped surface 52c. The height of the stepped surface 52c (length in the stacking direction D1) may be equal to or greater than the sum of the thickness of the separator 40 and the thickness of the negative electrode active material layer.

The second resin portion 54 surrounds the electrode laminate 30 and the first resin portion 52, and constitutes an outer wall (housing) of the power storage module 12. The second resin portion 54 is formed, for example, by injection molding of a resin, and extends over the entire length of the electrode laminate 30 in the stacking direction D1. The second resin portion 54 has a rectangular frame shape extending with the stacking direction D1 as the axial direction. The second resin portion 54 covers the outer surface of the first resin portion 52 extending in the stacking direction D1. The second resin portion 54 is joined to the outer surface of the first resin portion 52 and seals the outer surface of the first resin portion 52. The second resin portion 54 is welded to the outer surface of the first resin portion 52, for example, by heat during injection molding. The second resin portion 54 may be welded to the outer surface of the first resin portion 52 by hot plate welding.

The second resin portion 54 abuts on the adjacent second resin portion 54 on a surface extending outside the other surface 34b (here, the surface on which the negative electrode 38 is formed) of the electrode plate 34 of each bipolar electrode 32. There is. The second resin portion 54 has frame-shaped flange portions 54a and 54b extending inward at each of both end portions in the stacking direction D1. The flange portions 54a and 54b are portions that cover at least a part of the outer surface of the first resin portion 52 located at the laminated end of the electrode laminated body 30 in the stacking direction D1. In the stacking direction D1, the flange portion 54b arranged on the lower side of the electrode laminated body 30 is preferably thicker and wider than the flange portion 54a arranged on the upper side. The electrode laminate 30 is sandwiched by flange portions 54a and 54b formed at both ends in the stacking direction D1.

An internal space V that is liquid-tightly partitioned by the electrode plate 34 and the first resin portion 52 is formed between the electrode plates 34, 34 adjacent to each other in the stacking direction D1. An electrolytic solution (not shown) composed of an alkaline aqueous solution such as an aqueous solution of potassium hydroxide is housed in this internal space V. The electrolytic solution is impregnated in the separator 40, the positive electrode 36 and the negative electrode 38. Since the electrolytic solution is strongly alkaline, the frame 50 is made of a resin material having strong alkali resistance.

The frame body 50 is provided with a plurality of communication holes (not shown) that communicate with each internal space V. The communication hole extends in a direction intersecting (here, orthogonal) with the stacking direction D1 and functions as a liquid injection port for injecting the electrolytic solution into each internal space V, and after the electrolytic solution is injected, the pressure is increased. Functions as a connection port for a regulating valve (not shown).

The electrode plate 34 is made of metal and is made of, for example, nickel or a nickel-plated steel plate. The electrode plate 34 may be a rectangular metal foil made of nickel. The edge portion 34c of the electrode plate 34 (the outer edge portion of the bipolar electrode 32) has a rectangular frame shape, and is an uncoated region in which the positive electrode active material and the negative electrode active material are not coated. The uncoated area is an area held by the first resin portion 52 constituting the inner wall of the frame body 50.

The edge portion 34c of the electrode plate 34 is provided with an insulating portion 35 containing a metal in the composition. Specifically, as shown in FIG. 3, a metal insulating portion 35 is provided on the surface of the end portion 34d of the electrode plate 34. The metal insulating portion 35 may be a passivation coating or a portion where the metal constituting the electrode plate 34 is rusted.

Examples of the positive electrode active material constituting the positive electrode 36 include nickel hydroxide. Examples of the negative electrode active material constituting the negative electrode 38 include a hydrogen storage alloy. The formation region of the negative electrode 38 on the other surface 34b of the electrode plate 34 is slightly larger than the formation region of the positive electrode 36 on the one surface 34a of the electrode plate 34.

The separator 40 is formed, for example, in the form of a sheet. Examples of the material for forming the separator 40 include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a woven fabric made of polypropylene or the like, or a non-woven fabric. Further, the separator 40 may be reinforced with a vinylidene fluoride resin compound or the like.

Next, the operation of this embodiment will be described. According to the above embodiment, the following effects can be obtained.

(1) In the bipolar electrode 32, a fine gap is formed between the metal electrode plate 34 and the first resin portion 52 which is a resin member, and the electrolytic solution has entered the gap. In the electrode laminate 30, since it is a battery, a potential gradient is generated, and a potential gradient is also generated in the electrolytic solution that has entered the fine gap. At this time, alkaline ions in the electrolytic solution are attracted to the negative electrode potential, so that alkaline creep may occur. On the other hand, in the power storage module 12, by providing the insulating portion 35 at the end portion 34d of the electrode plate 34, electrolysis that has entered a fine gap formed between the electrode plate 34 and the first resin portion 52 which is a resin member. The potential gradient can be eliminated in part of the liquid pathway. This makes it possible to reduce the driving force at which the electrolytic solution is pulled to the potential of the negative electrode. Therefore, the progress of alkaline creep can be suppressed.

The above embodiment may be modified as follows.

In the above embodiment, the insulating portion 35 is provided on the edge portion 34c of the electrode plate 34. However, not only the insulating portion 35 is provided only on the end portion 34d of the electrode plate 34, but also the insulating portion 35 is provided in a frame shape from the end portion 34d to the outer edge portion on the plane of the electrode plate 34 as shown in FIGS. 5 and 6. It may be provided. At this time, it is desirable to provide the insulating portion 35 in the negative electrode uncoated region of the other surface 34b of the electrode plate 34, and it is further desirable that the insulating portion 35 does not face the positive electrode active material layer when viewed from the stacking direction D1. Further, when viewed from the stacking direction D1, the separator 40 has a larger area than the negative electrode active material layer, and it is desirable that the separator 40 is arranged so as to cover the negative electrode active material layer.

Further, as shown in FIGS. 4 and 6, the end portion 34d of the electrode plate 34 of each bipolar electrode 32 may be located between the first resin portions 52.

In the above modification, in addition to the effect (1), the following effects can be obtained.

(2) When the insulating portion 35 is provided in a frame shape from the end portion 34d to the outer edge portion on the plane of the electrode plate 34, the negative electrode uncoated region is covered by the insulating portion 35, so that the electrode plates 34 adjacent to each other in the region are covered. It has the effect of preventing a short circuit due to contact. In this case, it is not necessary to install the outer edge portion of the separator 40 on the first portion 52a of the first resin portion 52 as in the form of FIGS. 3 and 4. Therefore, as shown in FIGS. 5 and 6, the step of the inner edge portion of the first resin portion 52 becomes unnecessary, and the structure can be simplified.

(3) When the end portion 34d of the electrode plate 34 of each bipolar electrode 32 is held between the first resin portions 52, the contact region between the first resin portions 52 increases, so that the welding process can be simplified. Further, it is possible to prevent wrinkles and twists from occurring on the electrode plate 34 and the frame body 50.

12 ... power storage module, 30 ... electrode laminate (laminate), 32 ... bipolar electrode, 34 ... electrode plate, 34a ... one side, 34b ... other side, 34c ... edge, 34d ... end, 35 ... insulation, 36 ... Positive electrode, 37 ... Positive electrode side terminal electrode, 38 ... Negative electrode, 39 ... Negative electrode side terminal electrode, 40 ... Separator, D1 ... Laminating direction.

Claims (3)

A laminate in which a bipolar electrode including an electrode plate, a positive electrode having a positive electrode active material layer provided on one surface of the electrode plate, and a negative electrode having a negative electrode active material layer provided on the other surface of the electrode plate are laminated via a separator. Prepare,
At both ends of the laminated body, a positive electrode side terminal electrode is laminated so that a positive electrode active material layer provided on one surface of the electrode plate faces the inside of the laminated body, and a negative electrode active material provided on the other surface of the electrode plate. The negative electrode side terminal electrode laminated so that the layer faces the inside of the laminated body is laminated, respectively.
A resin frame that is welded to the edge of at least one surface of each of the electrode plates included in the laminate, holds the edge of each of the electrode plates, and seals the laminate is provided.
An internal space is formed between the electrode plates adjacent to each other in the stacking direction so as to be liquid-tightly partitioned by the frame and the electrode plates and to accommodate the electrolytic solution.
On the edge of the electrode plate, an insulating portion containing metal in the composition is formed in a frame shape .
The insulating portion is a portion where the metal constituting the electrode plate is rusted, and is a power storage module formed only on the side surface of an end portion of the electrode plate so as to follow the stacking direction of the laminated body. The resin frame is
A plurality of first resin portions provided on the edge of at least one surface of each of the electrode plates, and
It has a second resin portion provided around the first resin portion and accommodating the laminated body, and has.
The second resin portion extends over the entire length of the laminated body in the laminating direction, is joined to each of the plurality of first resin portions extending in the laminating direction, and is outside the plurality of first resin portions. The power storage module according to claim 1, wherein the side surface is sealed. The first resin part is
The first portion that overlaps with the electrode plate when viewed from the stacking direction,
It has a second portion that is integrally formed with the first portion and is provided outside the electrode plate when viewed from the stacking direction.
The power storage module according to claim 2, wherein the first resin portions adjacent to each other in the stacking direction are in contact with each other.

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