JP6785728B2 - Power storage device - Google Patents

Description

The present invention relates to a power storage device.

As a conventional power storage device, a bipolar battery including 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). The bipolar battery includes a laminate formed by laminating a plurality of bipolar electrodes via a separator. On the side surface of the laminated body, a sealing body for sealing between the bipolar electrodes adjacent to each other in the stacking direction is provided, and the electrolytic solution is housed in the internal space formed between the bipolar electrodes.

Japanese Unexamined Patent Publication No. 2011-204386

In the power storage device as described above, a negative electrode terminal electrode made of an electrode plate having a negative electrode formed on the inner surface is arranged at one end of the laminated body in the stacking direction. The edge of the electrode plate of the negative electrode terminal electrode is also sealed by a sealant, but when the electrolytic solution is composed of an alkaline solution, the electrolytic solution is transmitted on the electrode plate of the negative electrode terminal electrode due to the so-called alkaline creep phenomenon. , It may seep out to the outer surface side of the electrode plate through between the sealing body and the electrode plate. If the electrolytic solution leaks to the outer surface side, for example, corrosion of the conductive plate arranged adjacent to the negative electrode terminal electrode or short circuit between the negative electrode terminal electrode and the restraint member may occur, which is not preferable from the viewpoint of reliability. ..

The present invention has been made to solve the above problems, and an object of the present invention is to provide a power storage device with improved reliability.

The power storage device according to one aspect of the present invention is a power storage device having a bipolar electrode composed of an electrode plate having a positive electrode formed on one surface side and a negative electrode formed on the other surface side, and the bipolar electrode is formed via a separator. An internal space formed between the laminated body, which is provided on the side surface of the laminated body and which seals between the bipolar electrodes adjacent to each other in the stacking direction, and which is provided between the bipolar electrodes adjacent to each other in the stacking direction. Contains an electrolytic solution composed of an alkaline solution, and in the laminated body, a negative electrode terminal electrode composed of an electrode plate having a negative electrode formed on the inner surface is arranged at one end in the stacking direction, and the negative electrode terminal electrode of the negative electrode terminal electrode. A liquid absorbing member for absorbing the electrolytic solution is provided on the outer surface of the electrode plate.

In this power storage device, the electrolytic solution exuded from between the sealing body and the electrode plate of the negative electrode terminal electrode due to the alkaline creep phenomenon is absorbed by the liquid absorbing member provided on the outer surface of the electrode plate. As a result, it is possible to prevent corrosion and short circuit from occurring due to the exuded electrolytic solution, and it is possible to improve reliability.

Further, the liquid absorbing member may be made of a non-woven fabric. In this case, the electrolytic solution exuded from between the sealing body and the electrode plate of the negative electrode terminal electrode can be absorbed by the non-woven fabric.

Further, the liquid absorbing member may have a melt-solidified portion bonded to the outer surface. In this case, the liquid absorbing member can be easily and surely provided on the outer surface of the electrode plate of the negative electrode terminal electrode.

Further, the melt-solidified portion may be formed in a dot shape. In this case, it is possible to suppress the influence of heat generated during the formation of the melt-solidified portion on the negative electrode.

Further, the melt-solidified portion may be arranged outside the negative electrode forming region when viewed from the stacking direction. In this case, it is possible to further suppress the influence of heat generated during the formation of the melt-solidified portion on the negative electrode.

According to the present invention, it is possible to provide a power storage device with improved reliability.

It is the schematic sectional drawing which shows one Embodiment of the power storage device. It is the schematic sectional drawing which shows the internal structure of the power storage module of FIG. It is the schematic sectional drawing which shows the part of FIG. 2 enlarged. It is a figure which shows a part of FIG. 3 as seen from the stacking direction.

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

FIG. 1 is a schematic cross-sectional view showing an embodiment of a power storage device. The power storage device 1 shown in the figure is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The power storage device 1 is configured to include a power storage module stack 2 formed by stacking a plurality of power storage modules 4, and a restraint member 3 that applies a restraint load to the power storage module stack 2 in the stacking direction.

The power storage module stack 2 is composed of a plurality of (three bodies in the present embodiment) power storage modules 4 and a plurality of conductive plates 5 arranged between the power storage modules 4 and 4. The power storage module 4 is, for example, a bipolar battery provided with a bipolar electrode 14 described later, and has a rectangular shape when viewed from the stacking direction. The power storage module 4 is, for example, a secondary battery such as a nickel hydrogen secondary battery or a lithium ion secondary battery, or an electric double layer capacitor. In the following description, a nickel hydrogen secondary battery will be illustrated.

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

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

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

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

Next, the configuration of the power storage module 4 will be described in more detail. FIG. 2 is a schematic cross-sectional view showing the internal configuration of the power storage module 4. As shown in the figure, the power storage module 4 includes an electrode laminated body 11 and a sealing body 12 that seals the electrode laminated body 11.

The electrode laminate 11 is configured by laminating a plurality of bipolar electrodes 14 via a separator 13. In this example, the stacking direction D of the electrode laminate 11 coincides with the stacking direction of the power storage module stack 2. The bipolar electrode 14 is an electrode composed of an electrode plate 15 having a positive electrode 16 formed on one surface 15a and a negative electrode 17 formed on the other surface 15b. In the electrode laminate 11, the positive electrode 16 of one bipolar electrode 14 faces the negative electrode 17 of one of the bipolar electrodes 14 adjacent to each other in the stacking direction D with the separator 13 interposed therebetween. In the electrode laminate 11, the negative electrode 17 of one bipolar electrode 14 faces the positive electrode 16 of the other bipolar electrode 14 adjacent to each other in the stacking direction D with the separator 13 interposed therebetween.

In the electrode laminate 11, the negative electrode terminal electrode 18 is arranged at one end in the stacking direction D, and the positive electrode terminal 19 is arranged at the other end in the stacking direction D. The negative electrode terminal electrode 18 is an electrode plate 15 on which the negative electrode 17 is formed on the inner surface (the surface on the center side in the stacking direction D) 15d, and the positive electrode terminal electrode 19 is on the inner surface (the surface on the center side in the stacking direction D) 15f. The electrode plate 15 on which the positive electrode 16 is formed. The negative electrode 17 of the negative electrode terminal 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 16 of the positive electrode terminal electrode 19 faces the negative electrode 17 of the bipolar electrode 14 at the other end in the stacking direction D via the separator 13. One of the conductive plates 5 adjacent to the power storage module 4 is in contact with the outer surface 15e of the electrode plate 15 of the negative electrode terminal electrode 18. The other conductive plate 5 adjacent to the power storage module 4 is in contact with the outer surface 15 g of the electrode plate 15 of the positive electrode terminal electrode 19.

The electrode plate 15 is a rectangular metal foil made of, for example, nickel. The edge portion (edge portion of the bipolar electrode 14) 15c of the electrode plate 15 is an uncoated region in which the positive electrode active material and the negative electrode active material are not coated. Examples of the positive electrode active material constituting the positive electrode 16 include nickel hydroxide. Examples of the negative electrode active material constituting the negative electrode 17 include a hydrogen storage alloy. In the present embodiment, the formation region of the negative electrode 17 on the other surface 15b of the electrode plate 15 is slightly larger than the formation region of the positive electrode 16 on the one surface 15a of the electrode plate 15.

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

The sealing body 12 is formed in a rectangular tubular shape by, for example, an insulating resin. Examples of the resin material constituting the sealing body 12 include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), and the like. The sealing body 12 is configured to surround the side surface 11a of the electrode laminated body 11 formed by laminating the bipolar electrodes 14.

The sealing body 12 includes a first portion 21 provided along the edge portion 15c of the electrode plate 15 of each bipolar electrode 14, and a second portion provided so as to surround the entire first portion 21 from the outside. It is composed of 22 and. The first portion 21 is continuously provided over all sides of the electrode plate 15 at the edge portion 15c (uncoated region) on the one side 15a side of the electrode plate 15. The first portion 21 is bonded to the edge portion 15c by welding. A part of the inside of the first portion 21 is located between the edges 15c of the electrode plates 15 of the bipolar electrodes 14 and 14 adjacent to each other in the stacking direction D, and a part of the outside is outside from the electrode plate 15. Overhanging. The first portion 21 is buried in the second portion 22 in the outer part thereof.

The second portion 22 is formed by, for example, injection molding of a resin, and extends over the entire length of the electrode laminate 11 in the stacking direction D. The second portion 22 is welded to the outer surface of the first portion 21 by heat during injection molding, for example, and seals between the bipolar electrodes 14 and 14 adjacent to each other in the stacking direction D. As a result, an internal space V is formed between the bipolar electrodes 14 and 14 adjacent to each other in the stacking direction D. An electrolytic solution (not shown) composed of an alkaline solution such as an aqueous potassium hydroxide solution is housed in this internal space V. The electrolytic solution is impregnated in the separator 13, the positive electrode 16 and the negative electrode 17.

Similarly, the first portion 21 is also provided on the edge portion 15c of the electrode plate 15 of the negative electrode terminal 18 and the positive electrode 19 and the negative electrode 18 and the positive electrode 19 and the bipolar electrode 14 are separated from each other. It is sealed by two parts 22. As a result, an internal space V is formed between the negative electrode terminal electrode 18, the positive electrode terminal electrode 19, and the bipolar electrode 14, and the electrolytic solution is housed in this internal space V.

Here, in the power storage module 4 of the present embodiment, the liquid absorbing member 31 is provided on the outer surface 15e of the electrode plate 15 of the negative electrode terminal electrode 18. Hereinafter, the liquid absorbing member 31 will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a schematic cross-sectional view showing a part of FIG. 2 in an enlarged manner, and FIG. 4 is a view showing a part of FIG. 3 as viewed from the stacking direction D. In FIG. 4, the outer edge of the conductive plate 5 is indicated by a two-dot chain line, and the outer edge of the negative electrode 17 is indicated by a broken line.

The liquid absorbing member 31 is formed in a sheet shape by, for example, a non-woven fabric. Examples of the material constituting this non-woven fabric include polyolefins. The non-woven fabric may be subjected to plasma treatment in order to improve water absorption. The thickness of the liquid absorbing member 31 (the length along the stacking direction D) is, for example, about several hundred μm. The liquid absorbing member 31 has, for example, a rectangular annular shape when viewed from the stacking direction D, and is arranged between the first portion 21 and the conductive plate 5 to surround the conductive plate 5. In this example, the liquid absorbing member 31 is separated from both the first portion 21 and the conductive plate 5. A part of the inside of the liquid absorbing member 31 overlaps with the formation region of the negative electrode 17 when viewed from the stacking direction D.

The liquid absorbing member 31 has, for example, a melt-solidified portion 32 bonded to the outer surface 15e, and is bonded to the outer surface 15e by welding. The liquid absorbing member 31 is welded to the outer surface 15e by, for example, heat welding, and the melt-solidifying portion 32 is a portion that is melted and solidified during this welding. The outer surface 15e may be roughened for welding of the liquid absorbing member 31. A plurality of melt-solidified portions 32 are formed in a spot shape and are provided side by side at intervals along the extending direction (circumferential direction) of the liquid absorbing member 31. The melt-solidified portion 32 is located in the middle portion in the width direction of the liquid absorbing member 31 when viewed from the stacking direction D, and is arranged outside the formation region of the negative electrode 17.

Subsequently, the manufacturing method of the power storage device 1 described above will be described. The manufacturing method of the power storage device 1 includes a primary molding step, a laminating step, and a secondary molding step. First, in the primary molding step, a predetermined number of bipolar electrodes 14, a pair of negative electrode terminal electrodes 18 and a positive electrode terminal electrode 19 are prepared, and the first portion 21 is welded along the edge portion 15c of each electrode plate 15. Subsequently, in a state where the non-woven fabric is placed on the outer surface 15e of the electrode plate 15 of the negative electrode terminal electrode 18, a part of the non-woven fabric is melted and solidified to absorb liquid having a melt-solidified portion 32 bonded to the outer surface 15e. The member 31 is formed on the outer surface 15e. The liquid absorbing member 31 forming step may be performed before the forming step of the first portion 21.

In the laminating step, the bipolar electrode 14, the negative electrode terminal electrode 18, and the positive electrode terminal 19 are laminated via the separator 13 so that the first portion 21 is arranged between the edge portions 15c of the electrode plate 15. The electrode laminate 11 is formed. In the secondary molding step, after the electrode laminate 11 is placed in the injection molding mold (not shown), the molten resin is injected into the mold to surround the first portion 21 so as to surround the second portion. 22 is formed. As a result, the sealing body 12 is formed on the side surface 11a of the electrode laminated body 11.

After the secondary molding step, a step of injecting an electrolytic solution into the internal space V between the bipolar electrodes 14 and 14, a step of laminating the power storage module 4 and the conductive plate 5 to form the power storage module laminate 2, and a restraint member. The power storage device 1 shown in FIG. 1 is obtained through a step of restraining the power storage module laminate 2 and the like by 3.

Subsequently, the operation and effect of the power storage device 1 will be described.

As described above, in the power storage device 1, due to the so-called alkaline creep phenomenon, the electrolytic solution is transmitted on the electrode plate 15 of the negative electrode terminal electrode 18 and passes between the first portion 21 of the sealing body 12 and the electrode plate 15. It may seep out to the outer surface 15e side of the electrode plate 15. In FIG. 3, the movement path of the electrolytic solution in the alkaline creep phenomenon is indicated by an arrow A. This alkaline creep phenomenon occurs both when the power storage device 1 is charged and discharged, or when the power storage device 1 is energized and when no load is applied, due to an electrochemical factor.

On the other hand, in the power storage device 1, the electrolytic solution exuded from between the sealing body 12 and the electrode plate 15 of the negative electrode terminal electrode 18 due to the alkaline creep phenomenon is a liquid absorbing member provided on the outer surface 15e of the electrode plate 15. The liquid is absorbed (water is absorbed) by 31. As a result, it is possible to prevent corrosion and short circuit from occurring due to the exuded electrolytic solution, and it is possible to improve reliability. In the power storage device 1, the liquid absorbing member 31 is configured to be able to absorb at least a predetermined allowable amount of electrolytic solution. This allowable amount is set to, for example, an amount equal to the amount of the electrolytic solution contained in one internal space V (for example, 8 ml). After the liquid absorbing member 31 absorbs the liquid, the solvent of the electrolytic solution evaporates by natural drying, and only the salt of the electrolytic solution remains in the liquid absorbing member 31.

Further, in the power storage device 1, the liquid absorbing member 31 is made of a non-woven fabric. As a result, the electrolytic solution exuded from between the sealing body 12 and the electrode plate 15 of the negative electrode terminal electrode 18 can be absorbed by the non-woven fabric. Further, the power storage device 1 has a melt-solidifying portion 32 in which the liquid absorbing member 31 is bonded to the outer surface 15e. Thereby, the liquid absorbing member 31 can be easily and surely provided on the outer surface 15e.

Further, in the power storage device 1, the melt-solidification portion 32 is formed in a dot shape. As a result, it is possible to suppress the influence of heat generated when the melt-solidified portion 32 is formed on the negative electrode 17. Further, in the power storage device 1, the melt-solidifying portion 32 is arranged outside the formation region of the negative electrode 17 when viewed from the stacking direction D. As a result, it is possible to further suppress the influence of heat generated when the melt-solidified portion 32 is formed on the negative electrode 17.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the liquid absorbing member 31 may have a liquid absorbing property, and may be made of a resin member formed in a sponge shape such as a sponge or a porous material. Further, the liquid absorbing member 31 may be connected to the outer surface 15e by, for example, bonding. Further, the liquid absorbing member 31 may be arranged so as to come into contact with the first portion 21. Further, the melt-solidified portion 32 may be continuously formed linearly along the extending direction (circumferential direction) of the liquid absorbing member 31.

Further, in the above embodiment, the first portion 21 is formed only on the one surface 15a side of the electrode plate 15, but the first portion 21 is formed on both the one surface 15a side and the other surface 15b side. For example, the edge portion 15c of the electrode plate 15 may be formed so as to be buried in the first portion 21. Alternatively, the first portion 21 may be formed only on the other surface 15b side. Further, in the above embodiment, a part of the outside of the first portion 21 projects outward from the electrode plate 15, but if the first portion 21 is arranged at least between the edge portions 15c of the electrode plate 15. Often, for example, the entire first portion 21 may be arranged between the edge portions 15c of the electrode plate 15.

1 ... power storage device, 11 ... electrode laminate, 11a ... side surface, 12 ... sealant, 13 ... separator, 14 ... bipolar electrode, 15 ... electrode plate, 15a ... one side, 15b ... other side, 15c ... edge, 15d ... Inner surface, 15e ... Outer surface, 16 ... Positive electrode, 17 ... Negative electrode, 18 ... Negative electrode terminal electrode, 31 ... Liquid absorbing member, 32 ... Melt solidification part, D ... Lamination direction, V ... Internal space.

Claims (5)

A power storage device having a bipolar electrode composed of an electrode plate having a positive electrode formed on one side and a negative electrode formed on the other side.
A laminate formed by laminating the bipolar electrodes via a separator, and
A sealing body provided on the side surface of the laminated body and sealing between the bipolar electrodes adjacent to each other in the stacking direction is provided.
An electrolytic solution composed of an alkaline solution is housed in the internal space formed between the bipolar electrodes adjacent to each other in the stacking direction.
In the laminated body, a negative electrode terminal electrode made of an electrode plate having the negative electrode formed on the inner surface is arranged at one end in the laminated direction.
A power storage device provided with a liquid absorbing member for absorbing the electrolytic solution on the outer surface of the electrode plate of the negative electrode terminal electrode. The power storage device according to claim 1, wherein the liquid absorbing member is made of a non-woven fabric. The power storage device according to claim 1 or 2, wherein the liquid absorbing member has a melt-solidified portion bonded to the outer surface. The power storage device according to claim 3, wherein the melt-solidified portion is formed in a dot shape. The power storage device according to claim 3 or 4, wherein the melt-solidified portion is arranged outside the negative electrode forming region when viewed from the stacking direction.

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