JP6913587B2 - Power storage device - Google Patents

Description

The present invention relates to a power storage device.

As a conventional power storage device, a so-called bipolar type power storage device 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 device includes an electrode laminate formed by laminating a plurality of bipolar electrodes via a separator. On the side surface of the electrode laminate, a sealant is provided to seal between the bipolar electrodes adjacent to each other in the lamination direction. The electrolytic solution is housed in the internal space formed between the sealant and the bipolar electrode.

Japanese Unexamined Patent Publication No. 2011-204386

In the above-mentioned power storage device, in order to improve the bonding strength and the liquidtightness between the electrode plate constituting the bipolar electrode and the sealing body, a configuration in which the surface of the electrode plate is rough can be adopted. A plurality of fine protrusions by, for example, electrolytic plating are provided on the rough surface. As a result, the constituent material of the encapsulant enters between the fine protrusions, and the joint strength and liquidtightness between the electrode plate and the encapsulant can be improved.

By the way, in a power storage device that uses an alkaline solution as an electrolytic solution, for example, a nickel-metal hydride battery, a so-called alkaline creep phenomenon may occur in which the electrolytic solution moves from a positive potential to a negative potential. In the configuration in which the fine protrusions are provided on the surface of the electrode plate, a not a little gap is generated between the rough surface and the sealing body. Therefore, a technique for suppressing a short circuit between bipolar electrodes due to an alkaline creep phenomenon and leakage of an electrolytic solution to the outside of a power storage device is desired.

The present invention has been made to solve the above problems, and can improve the bonding strength and liquidtightness between the electrode plate and the sealing body, and between the bipolar electrodes due to the alkaline creep phenomenon. An object of the present invention is to provide a power storage device capable of suppressing a short circuit or leakage of an electrolytic solution to the outside of the power storage device.

The power storage device according to one aspect of the present invention is a laminate in which a plurality of bipolar electrodes are laminated via a separator, and a sealing body provided on the side surface of the laminate and sealing between the bipolar electrodes adjacent to each other in the lamination direction. The bipolar electrode has an electrode plate bonded to the encapsulant while having a positive electrode formed on one surface side and a negative electrode formed on the other surface side. An internal space containing an electrolytic solution composed of an alkaline solution is provided between them, and at least the joint portion with the sealing body of the electrode plate is a rough surface provided with a plurality of fine protrusions. The surface is provided with an alkali-resistant packing layer that fills the gap between the sealing body and the sealing body.

In this power storage device, a rough surface is provided on the electrode plate constituting the bipolar electrode, and the constituent material of the encapsulant enters between a plurality of fine protrusions on the rough surface to join the electrode plate and the encapsulant. Strength and liquidtightness are improved. Further, in this power storage device, an alkali-resistant packing layer is provided on the rough surface of the electrode plate to fill the gap between the electrode plate and the sealing body. By arranging such a packed layer, the occurrence of the alkaline creep phenomenon of the electrolytic solution is suppressed, and the electrolytic solution moves to the internal space of the adjacent bipolar electrode through the gap between the rough surface and the sealing body. Can be deterred. Therefore, it is possible to prevent a short circuit between the bipolar electrodes and leakage of the electrolytic solution to the outside of the power storage device due to the alkaline creep phenomenon.

Further, the fine protrusion has a tip-thick portion, and the filling layer may be provided so that the tip-thick portion is exposed. In this case, while the packed layer exerts the effect of suppressing the alkaline creep phenomenon, the thick portion of the fine protrusions is exposed from the packed layer, so that an anchor effect on the encapsulant can be sufficiently generated, and the electrode plate and the seal can be sealed. Sufficient joint strength and liquidtightness with the stationary body can be ensured.

Further, the viscosity of the packed bed may be 0.6 Pa · s or less. By using a packed layer having a viscosity of 0.6 Pa · s or less, the packed layer can be more reliably distributed in the gap between the rough surface and the sealing body.

Further, the packed bed may be composed of fluorine-based grease, silicon-based grease, or asphalt pitch. When such a material is used, a packed bed that causes the above action can be easily formed.

According to the present invention, it is possible to improve the joint strength and liquidtightness between the electrode plate and the sealing body, and also cause a short circuit between the bipolar electrodes due to the alkaline creep phenomenon and the electrolytic solution to the outside of the power storage device. Liquid leakage can be suppressed.

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. It is an enlarged schematic view of the main part which shows the structural example of the joint part of the electrode plate and the sealing body. It is an enlarged schematic view of a main part which shows the state of the gap which may occur in the joint part between an electrode plate and a sealing body. It is a schematic cross-sectional view which shows the movement path of the electrolytic solution by an alkaline creep phenomenon. It is an enlarged schematic view of the main part which shows the structure of the joint part of the electrode plate and the sealing body which concerns on this embodiment.

Hereinafter, preferred embodiments of the power storage device according to one aspect of the present invention will be described in detail with reference to the drawings.

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 a device 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 portion 3 for applying a restraint pressure to the power storage module stack 2.

The power storage module stack 2 is composed of a plurality of (three in this 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 a bipolar type power storage module provided with a plurality of bipolar electrodes 14 (described later), and has a rectangular shape when viewed from the stacking direction. Storage module 4, for example, a nickel-hydrogen secondary battery, or an electric double layer capacitor. In the following description, a nickel-metal hydride 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 plate 5 is also arranged on the outside of the power storage module 4 located at the laminated end of the power storage module stack 2. A positive electrode terminal 6 is connected to a conductive plate 5 arranged outside the power storage module 4 located at one of the laminated ends. Further, the negative electrode terminal 7 is connected to the conductive plate 5 arranged outside the power storage module 4 located at the other 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 with each other in 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 portion 3 includes a pair of restraint 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 restraint plates 8 and 8 to each other. The restraint 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 arranged on the inner surface of the restraint plate 8 (the surface on the side of the power storage module laminate 2). The energy storage module laminate 2 and the restraint plate 8 are electrically insulated by the film F.

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

FIG. 2 is a schematic cross-sectional view showing the internal configuration of the power storage module. 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. The bipolar electrode 14 is an electrode composed of an electrode plate 15 having a positive electrode 16 formed on one side 15a and a negative electrode 17 formed on the other side 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 with the separator 13 interposed therebetween. Further, 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 with the separator 13 interposed therebetween.

The negative electrode terminal electrode 18 is arranged on one of the laminated ends of the electrode laminated body 11, and the positive electrode terminal electrode 19 is arranged on the other side of the laminated end of the electrode laminated body 11. The negative electrode terminal electrode 18 is composed of an electrode plate 15 having a negative electrode 17 formed on the inner surface side (center side in the stacking direction), and the positive electrode terminal electrode 19 has a positive electrode 16 on the inner surface side (center side in the stacking direction). It is composed of the formed electrode plate 15. The negative electrode 17 of the negative electrode terminal electrode 18 faces the positive electrode 16 of one of the bipolar electrodes 14 at the laminated end via the separator 13. The positive electrode 16 of the positive electrode terminal electrode 19 faces the negative electrode 17 of the other bipolar electrode 14 at the laminated end via the separator 13. The electrode plate 15 of the negative electrode terminal electrode 18 and the electrode plate 15 of the positive electrode terminal 19 are electrically connected to the conductive plate 5 (see FIG. 1) adjacent to the power storage module 4.

The electrode plate 15 is, for example, a nickel-plated steel plate in which a steel plate is plated with nickel, or a rectangular metal foil made of nickel. The edge portion 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, and the uncoated region is buried and held in the sealing body 12. Examples of the positive electrode active material constituting the positive electrode 16 include nickel hydroxide. Further, 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 material for forming the separator 13 include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a woven cloth made of polypropylene, polyethylene terephthalate (PET), methyl cellulose and the like, or a non-woven fabric. .. Further, the separator 13 may be reinforced with a vinylidene fluoride resin compound.

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 of the electrode laminated body 11 formed by laminating the bipolar electrodes 14.

The sealing body 12 is provided so as to surround the primary sealing body 21 provided along the edge portion 15c of the electrode plate 15 of each bipolar electrode 14 and the entire primary sealing body 21 from the outside. It is composed of a subsealing body 22 and the like. The primary encapsulant 21 is formed by, for example, injection molding of resin, and 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. There is. In the present embodiment, the primary encapsulant 21 is provided so as to wrap around from the one surface 15a side of the electrode plate 15 to the end surface 15d side, and is bonded to the one surface 15a and the end surface 15d by, for example, welding. The primary encapsulants 21 and 21 adjacent to each other in the stacking direction are in contact with each other, but are not joined by welding or the like.

The primary sealant 21 seals between the bipolar electrodes 14 and 14 adjacent to each other in the stacking direction, and also functions as a spacer between the electrode plates 15 and 15 of the bipolar electrodes 14 and 14 adjacent to each other in the stacking direction. An internal space V defined by the thickness of the portion of the primary sealing body 21 located between the electrode plates 15 and 15 is formed between the electrode plates 15 and 15. The internal space V contains an electrolytic solution E composed of an alkaline solution such as an aqueous potassium hydroxide solution.

The secondary encapsulant 22 is formed by, for example, injection molding of a resin, and extends over the entire length of the electrode laminate 11 in the lamination direction. The secondary encapsulant 22 is welded to the outer surface of the primary encapsulant 21 by heat during injection molding, for example. In the sealing body 12, the electrolytic solution E housed in the internal space V can pass between the primary sealing bodies 21 and 21 adjacent to each other in the stacking direction, but the primary sealing body 21 and the secondary sealing body 22 It is sealed at the welded part.

Subsequently, the bonding structure between the bipolar electrode 14 and the sealing body 12 described above will be described in more detail.

FIG. 3 is an enlarged schematic view of a main part showing a configuration example of a joint portion between the electrode plate and the sealing body. As shown in the figure, when joining the bipolar electrode 14 and the sealing body 12, a rough surface 31 provided with a plurality of fine protrusions 32 is provided at the joining portion of the electrode plate 15 with at least the primary sealing body 21. It is provided. In the present embodiment, the rough surface 31 is provided over the entire surface of one surface 15a of the electrode plate 15 on which the positive electrode 16 is provided.

The fine protrusion 32 is, for example, a protrusion-shaped precipitated metal (including an impart) formed by electrolytic plating on the electrode plate 15. The shape of the microprojection 32 generally includes a columnar base end portion 32a and a substantially spherical tip portion 32b. The shape of the fine protrusions 32 is not limited to a uniform shape. For example, the shape of the base end portion 32a may be a substantially spherical shape or a shape in which substantially spherical portions are continuous. The width dimension of the tip end portion 32b of the fine protrusion 32 is larger than the width dimension of the base end portion 32a. That is, the tip portion 32b of the fine protrusion 32 is a tip thick portion 33. The height of the fine protrusions 32 is not particularly limited, but is set to about 0.1 μm to 30 μm when the thickness of the electrode plate 15 is about 0.1 μm to 1000 μm. On the rough surface 31, the resin material constituting the primary sealing body 21 enters the space between the fine protrusions 32 and 32 to generate an anchor effect, and the bonding strength between the electrode plate 15 and the primary sealing body 21 and the bonding strength and the primary sealing body 21 are generated. The liquidtightness is improved. The tip-thick portion 33 is not limited to the configuration formed in the tip end portion 32b, and a tip-thick portion 33 thicker than the base end portion 32a is formed between the base end portion 32a and the tip end portion 32b. You may.

When the primary encapsulant 21 is joined to the electrode plate 15 by welding, for example, the resin material of the primary encapsulant 21 is roughened by pressing the heated primary encapsulant 21 against the edge of one surface 15a of the electrode plate 15. It is inserted between the fine protrusions 32 and 32 in 31. In this case, if the temperature of the primary encapsulant 21 decreases after joining, the resin material shrinks as the temperature decreases. Therefore, as shown in FIG. 4, it is conceivable that a gap S is formed between the fine protrusions 32 and 32, for example, between one surface 15a of the electrode plate 15 and the primary sealing body 21. The gap S may also be formed between the base end portion 32a of the fine protrusion 32 and the primary sealing body 21.

On the other hand, in the power storage device 1, an electrolytic solution E (see FIG. 5) composed of an alkaline solution such as an aqueous potassium hydroxide solution is housed in the internal space V. Therefore, if a gap S exists between one surface 15a of the electrode plate 15 and the primary sealing body 21, the gap S can serve as a movement path for the electrolytic solution E due to the alkaline creep phenomenon. The alkaline creep phenomenon is a phenomenon in which the electrolytic solution E, which is an alkaline solution, moves from a positive potential to a negative potential.

In the present embodiment, in the bipolar electrode 14, the other surface 15b side on which the negative electrode 17 is formed has a positive potential, and the one side 15a side on which the positive electrode 16 is formed has a negative potential. In the present embodiment, since the primary encapsulants 21 and 21 adjacent to each other in the stacking direction are not joined to each other, as shown in FIG. 5, the other surface 15b and the primary encapsulant 21 are connected from the internal space V on the other surface 15b side. A movement path K of the electrolytic solution E is formed, which wraps around to the one-sided surface 15a side through the space between the two, passes through the gap S between the one-sided surface 15a and the primary sealing body 21, and escapes to the internal space V on the one-sided surface 15a side. Can be done. When such movement of the electrolytic solution E occurs, it is conceivable that a short circuit between the bipolar electrodes 14 and 14 and leakage of the electrolytic solution E to the outside of the power storage device 1 occur.

On the other hand, in the power storage device 1, as shown in FIG. 6, an alkali-resistant filling layer 34 is provided on the rough surface 31 to fill the gap S between the rough surface 31 and the primary sealing body 21. The packing layer 34 is formed over the entire surface of the joint portion between the electrode plate 15 and the primary sealing body 21. For the formation of the packing layer 34, for example, silicon using perfluoroalkyl ether as a base oil, fluorogrease using polytetrafluoroethylene as a thickener, silicone oil as a base oil, and metal soap as a thickener. Grease, liquid petroleum modified asphalt, asphalt pitch containing hydrocarbon as a component, etc. are used.

In order to block the movement of the electrolytic solution E due to the alkaline creep phenomenon, it is necessary to satisfy either 1) no potential, 2) no gap, and 3) no water. It becomes. By providing the filling layer 34 with grease or the like described above between the rough surface 31 and the primary sealing body 21, 2 of the conditions 1) to 3) between the rough surface 31 and the primary sealing body 21 ) Is satisfied, and the movement path K of the electrolytic solution E shown in FIG. 5 can be canceled. Further, since the packed bed 34 has alkali resistance, the packed bed 34 is not eroded by the electrolytic solution E, and the action of blocking the movement of the electrolytic solution E can be maintained.

The packing layer 34 is preferably provided so that the thick portion 33 of the fine protrusion 32 is exposed. In the example shown in FIG. 6, the filling layer 34 is provided on the rough surface 31 at a height lower than the height of the base end portion 32a of the fine protrusion 32, and is based on the entire tip thick portion 33 of the fine protrusion 32. A part of the end portion 32a (the root portion of the tip thick portion 33) is exposed from the filling layer 34. The height of the packing layer 34 is not limited to this, and may be such that only the tip portion of the tip thick portion 33 is exposed, and the height is such that most of the proximal end portion 32a is exposed. You may.

The method for forming the packed layer 34 is not particularly limited. For example, a material for forming the packed layer 34 is previously applied to the rough surface 31 or the joint surface with the rough surface 31 of the primary sealing body 21, and the electrode plate 15 is in this state. The primary sealant 21 may be welded. Considering the ease of coating, the surface of the primary encapsulant 21 is flatter than the rough surface 31, so it is preferable to apply the material for forming the packing layer 34 to the surface of the primary encapsulant 21. When the primary encapsulant 21 is welded to the electrode plate 15, the material for forming the packing layer 34 is preferably a material that does not deteriorate or volatilize at the melting point of the primary encapsulant 21.

Further, the height of the packed layer 34 can be controlled by adjusting the viscosity of the material forming the packed layer 34. Assuming that the height of the fine protrusions 32 is 10 μm, when the viscosity is 100 Pa · s (viscosity of about hand cream) and the viscosity is 11 Pa · s (viscosity of starch syrup), the fluidity is poor and the fine protrusions The entire 32 may be buried in the packing layer 34. Alternatively, the constituent material of the packing layer 34 may not sufficiently penetrate between the fine protrusions 32 and 32. On the other hand, when the viscosity is 0.6 Pa · s (viscosity of about oil), sufficient fluidity is ensured, and the thick portion 33 of the fine protrusions 32 can be exposed from the filling layer 34. Therefore, the viscosity of the packed bed is preferably 0.6 Pa · s or less.

As described above, in the power storage device 1, the rough surface 31 is provided on the electrode plate 15 constituting the bipolar electrode 14, and the constituent material of the primary encapsulant 21 is between the plurality of fine protrusions 32, 32 on the rough surface 31. By entering, the bonding strength and liquidtightness between the electrode plate 15 and the primary sealing body 21 can be improved. Further, in the power storage device 1, an alkali-resistant filling layer 34 is provided on the rough surface 31 of the electrode plate 15 to fill the gap S between the electrode plate 15 and the primary sealing body 21. By such an arrangement of the packing layer 34, the occurrence of the alkaline creep phenomenon of the electrolytic solution E is suppressed, and the electrolytic solution E passes through the gap S between the rough surface 31 and the primary sealing body 21 and is adjacent to the bipolar electrode 14. It can be prevented from moving to the internal space V of. Therefore, it is possible to prevent a short circuit between the bipolar electrodes 14 and 14 due to the alkaline creep phenomenon and leakage of the electrolytic solution E to the outside of the power storage device 1.

Further, in the power storage device 1, the fine protrusion 32 has a tip-thick portion 33, and the filling layer 34 is provided so that the tip-thick portion 33 is exposed. As a result, the packed layer 34 exerts the effect of suppressing the alkaline creep phenomenon, while the tip-thick portion 33 of the fine protrusions is exposed from the packed layer 34, so that the anchor effect on the primary sealing body 21 can be sufficiently generated. , The joint strength and liquidtightness between the electrode plate 15 and the primary sealing body 21 can be sufficiently ensured.

Further, in the power storage device 1, the viscosity of the packing layer 34 is 0.6 Pa · s or less. By using the packed layer 34 having a viscosity of 0.6 Pa · s or less, the packed layer 34 can be more reliably distributed in the gap S between the rough surface 31 and the primary sealing body 21. Further, since the packing layer 34 is composed of fluorine-based grease, silicon-based grease, or asphalt pitch, the packing layer 34 that causes the above action can be easily formed.

1 ... power storage device, 11 ... electrode laminate (laminate), 12 ... sealant, 13 ... separator, 14 ... bipolar electrode, 15 ... electrode plate, 15a ... one side, 15b ... other side, 16 ... positive electrode, 17 ... Negative electrode, 31 ... Rough surface, 32 ... Fine protrusions, 33 ... Thick part, 34 ... Filled layer, E ... Electrolyte, S ... Gap, V ... Internal space.

Claims (4)

A laminate in which a plurality of bipolar electrodes are laminated via a separator,
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.
The bipolar electrode has an electrode plate bonded to the encapsulant as well as having a positive electrode formed on one surface side and a negative electrode formed on the other surface side.
An internal space in which an electrolytic solution composed of an alkaline solution is housed is provided between the bipolar electrode and the sealing body.
In the electrode plate, at least the joint portion with the sealing body is a rough surface provided with a plurality of fine protrusions.
A power storage device provided with an alkali-resistant packing layer on the rough surface to fill a gap between the rough surface and the sealing body. The fine protrusion has a thick tip portion and has a thick tip portion.
The power storage device according to claim 1, wherein the filling layer is provided so that the thick tip portion is exposed. The power storage device according to claim 1 or 2, wherein the viscosity of the packed bed is 0.6 Pa · s or less. The power storage device according to any one of claims 1 to 3, wherein the packed bed is composed of fluorine-based grease, silicon-based grease, or asphalt pitch.

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