JP2018073509A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of improving reliability.SOLUTION: In a power storage device 1, the thickness of outermost electrode plates 11A and 11B arranged on the outermost side in a laminate direction of an electrode plate 11 included in a laminate body 2 is larger than the other electrode plate 11 arranged in an inner side in the laminate direction. That is, the outermost electrode plates 11A and 11B receive a force inducing deformation due to influence of differential pressure of an inner pressure and an atmospheric pressure of the laminate body 2 in a seal part 4 to the outer side in the laminate direction. The thickness of the outermost electrode plates 11A and 11B is higher than that of the other electrode plate 11, and the intensity of them becomes increase. Therefore, the deterioration due to influence of the force acting on the outermost electrode plates 11A and 11B can be suppressed. Thus, reliability of the power storage device 1 can be improved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power storage device.

  As a conventional power storage device, 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). The bipolar battery is provided with a laminate formed by laminating a plurality of bipolar electrodes via a separator. The laminated body is provided with a seal portion so that side surfaces formed by the lamination of bipolar electrodes are held.

JP 2007-122977 A

  In the power storage device as described above, a pressure that induces deformation on the electrode plate does not act between the bipolar electrodes on the inner side in the stacking direction because the pressure balance between the bipolar electrodes is maintained. On the other hand, a force that induces deformation may act on the outermost electrode plate in the stacking direction due to the effect of the differential pressure between the internal pressure of the stack and the atmospheric pressure. This may affect the reliability of the power storage device. Therefore, there has been a demand for improving the reliability of the power storage device.

  SUMMARY An advantage of some aspects of the invention is that it provides a power storage device that can improve reliability.

  A 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 side and a negative electrode formed on the other side, with a separator interposed therebetween. A laminated body formed by alternately laminating bipolar electrodes, and a seal portion formed between at least the edges of the electrode plates of the laminated body, and the laminating direction of the electrode plates included in the laminated body The thickness of the outermost electrode plate disposed on the outermost side is greater than the thicknesses of the other electrode plates disposed on the inner side in the stacking direction.

  In this power storage device, among the electrode plates included in the stacked body, the thickness of the outermost electrode plate disposed on the outermost side in the stacking direction is greater than the thickness of the other electrode plate disposed on the inner side in the stacking direction. That is, the outermost electrode plate receives a force that induces deformation to the outside in the laminating direction due to the influence of the differential pressure between the internal pressure of the laminated body and the atmospheric pressure in the seal portion. Compared with the electrode plate, the thickness is large and the strength is high. Therefore, deformation due to the influence of the force acting on the outermost electrode plate can be suppressed. Thereby, the reliability of the power storage device can be improved.

  The outermost electrode plate may be composed of a plurality of laminated metal foils. With such a configuration, it is possible to easily increase the thickness of the outermost electrode plate by simply stacking a plurality of metal foils. In addition, it is possible to increase the thickness of the outermost electrode plate by using an electrode foil common to other electrode plates. Therefore, it is possible to improve the manufacturability of the outermost electrode plate.

  The outermost electrode plate may include a metal foil and a plating layer formed on the surface of the metal foil. With such a configuration, the thickness of the outermost electrode plate can be easily adjusted by adjusting the thickness of the plating layer.

  Further, the outermost electrode plate may be made of a metal foil having a thickness larger than that of the metal foil constituting the other electrode plate. With such a configuration, it is possible to increase the thickness of the outermost electrode plate by increasing the thickness of one metal foil itself, so that contact between metal foils as occurs when a plurality of metal foils are stacked. There is no resistance. Therefore, the electrical characteristics at the outermost electrode plate can be stabilized.

  The power storage device may further include a pair of restraining plates that restrain the stacked body from the outside in the stacking direction, and the restraining plates may be in contact with the outermost electrode plate and connected to an extraction portion that extracts current. With such a configuration, the constraining plate can support the outermost electrode plate that tends to deform outward in the stacking direction due to the influence of the differential pressure between the internal pressure and the atmospheric pressure. Therefore, the constraining plate can suppress deformation of the outermost electrode plate. Further, the restraint plate has a function of restraining the laminated body and can also serve as a current collecting function for collecting current generated in the laminated body. Therefore, the constraining plate can secure a distance for enlarging or converging the current path between the extraction portion and the outermost electrode plate. Thereby, the nonuniformity of the electric power generation in a bipolar electrode can be reduced.

  According to the present invention, the reliability of the power storage device can be improved.

It is a schematic sectional drawing which shows the structure of the electrical storage apparatus which concerns on one Embodiment of this invention. It is an enlarged view which shows the structure of an outermost electrode plate. It is a conceptual diagram of an outermost electrode plate and an electrode plate. It is a schematic sectional drawing which shows the structure of the electrical storage apparatus which concerns on a modification.

  Hereinafter, preferred embodiments of a 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 illustrating a configuration of a power storage device according to an embodiment of the present invention. The power storage device 1 shown in the figure is a bipolar battery including a laminated body 2 of bipolar electrodes 3. The power storage device 1 is, for example, a secondary battery such as a nickel metal hydride secondary battery or a lithium ion secondary battery, or an electric double layer capacitor. The power storage device 1 is used as a battery for various vehicles such as forklifts, hybrid vehicles, and electric vehicles. In the following description, a nickel metal hydride secondary battery is illustrated.

  The power storage device 1 includes the laminate 2 of the bipolar electrode 3 described above, a seal portion 4 that holds the laminate 2, and a restraining member 5 that restrains the laminate 2.

  The laminate 2 is configured by laminating a plurality of bipolar electrodes 3 with separators 6 interposed therebetween. Each of the bipolar electrodes 3 includes an electrode plate 11, a positive electrode 12 provided on one surface 11 a of the electrode plate 11, and a negative electrode 13 provided on the other surface 11 b of the electrode plate 11. In the laminate 2, the positive electrode 12 of one bipolar electrode 3 faces the negative electrode 13 of one bipolar electrode 3 adjacent in the stacking direction, and the negative electrode 13 of one bipolar electrode 3 is the other bipolar electrode adjacent in the stacking direction. Opposite the positive electrode 12 of the electrode.

  The electrode plate 11 is a metal foil made of nickel, for example. The thickness of the electrode plates 11 other than the outermost electrode plates 11A and 11B described later is, for example, about 0.1 μm to 1000 μm. An example of the positive electrode active material constituting the positive electrode 12 is nickel hydroxide. An example of the negative electrode active material constituting the negative electrode 13 is a hydrogen storage alloy. The formation region of the negative electrode 13 on the other surface 11 b of the electrode plate 11 may be slightly larger than the formation region of the positive electrode 12 on the one surface 11 a of the electrode plate 11.

  The edge portion 11 c of the electrode plate 11 is an uncoated region where the positive electrode active material and the negative electrode active material are not applied, and is held by the seal portion 4 while being buried in the inner wall 4 a of the seal portion 4. As a result, a space partitioned by the electrode plates 11 and 11 and the inner wall 4a of the seal portion 4 is formed between the electrode plates 11 and 11 adjacent in the stacking direction. In the space, an electrolytic solution (not shown) made of an alkaline solution such as an aqueous potassium hydroxide solution is accommodated.

  The stacked body 2 includes an outermost electrode plate 11A and an outermost electrode plate 11B that are disposed on the outermost side in the stacking direction among the electrode plates 11 included in the stacked body 2. The outermost electrode plate 11 </ b> A is provided at one stacked end (the upper stacked end in FIG. 1) of the stacked body 2. In the outermost electrode plate 11A, only the negative electrode 13 is provided on one inner surface in the stacking direction. The outermost electrode plate 11B is provided at the other stacked end of the stacked body 2 (lower stacked end in FIG. 1). In the outermost electrode plate 11B, only the positive electrode 12 is provided on one inner surface in the stacking direction. The edge portions of the outermost electrode plates 11 </ b> A and 11 </ b> B are held by the seal portion 4 in a state of being buried in the inner wall 4 a of the seal portion 4, similarly to the electrode plate 11 of the bipolar electrode 3. Details of the configuration of the outermost electrode plates 11A and 11B will be described later.

  The separator 6 is formed in a sheet shape, for example. Examples of the material for forming the separator include a porous film made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP), a woven fabric or a nonwoven fabric made of polypropylene, polyethylene terephthalate (PET), methylcellulose, and the like. The separator 6 may be reinforced with a vinylidene fluoride resin compound. The separator 6 is not limited to a sheet shape, and may be a bag shape.

  The seal portion 4 is formed in a rectangular cylindrical shape by, for example, injection molding using an insulating resin. Examples of the resin material constituting the resinous seal portion 4 include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), modified polyphenylene sulfide (modified PPS), and the like. The seal portion 4 is a member that surrounds and holds the side surface 2 a of the stacked body 2 formed by stacking the bipolar electrodes 3. More specifically, the seal portion 4 holds the edge of the electrode plate 11 of the bipolar electrode 3 and the outermost electrode plates 11A and 11B located at the stacking end of the stacked body 2, and between the bipolar electrodes 3 and 3. The space for accommodating the electrolytic solution to be formed is sealed.

  The restraint member 5 includes a pair of restraint plates 21A and 21B, a connecting member (bolt 22 and nut 23) for joining the restraint plates 21A and 21B, and the outermost electrode plates 11A and 11B and the restraint plates 21A and 21B. Current collector plates 25A and 25B, and extraction portions 26A and 26B for taking out current from the current collector plates 25A and 25B. The restraint plates 21A and 21B are formed in a flat plate shape. The restraining plates 21A and 21B may be made of an insulating material such as nylon, for example. Alternatively, the restraining plates 21A and 21B may be formed in a flat plate shape with a conductive material such as iron or aluminum. However, when the restraining plates 21A and 21B are made of a conductive material, an insulating member is disposed between the restraining plates 21A and 21B and the current collecting plates 25A and 25B. An insertion hole 21a through which the bolt 22 is inserted is provided at a position on the outer side of the seal portion 4 at the edge of the restraint plates 21A and 21B. For example, the bolt 22 is passed through the insertion hole 21a from one restraint plate 21A side to the other restraint plate 21B side, and a nut 23 is screwed onto the tip of the bolt 22 protruding from the other restraint plate 21B. Yes.

  The current collecting plates 25A and 25B are formed in a flat plate shape with a conductive material such as aluminum or nickel-plated steel plate. The inner surface of the current collecting plate 25A in the stacking direction is in contact with the outermost electrode plate 11A in the inner region of the seal portion 4. The inner surface in the stacking direction of the other current collector plate 25B is in contact with the outermost electrode plate 11B in the region inside the seal portion 4.

  The extraction portion 26A is connected to the current collector plate 25A. The extraction portion 26A is connected to the side surface of the current collector plate 25A. The extraction portion 26 </ b> A penetrates the seal portion 4 and is drawn to the outside of the seal portion 4. However, the connection position and the extraction position of the extraction part 26A are not particularly limited. The extraction portion 26B is connected to the current collector plate 25B. The extraction portion 26B is connected to the side surface of the current collector plate 25B. The take-out part 26 </ b> B penetrates the seal part 4 and is drawn out of the seal part 4. However, the connection position and the extraction position of the extraction part 26B are not particularly limited.

  Thereby, the laminate 2, the outermost electrode plates 11A and 11B, and the seal portion 4 are sandwiched and unitized, and a restraining load is applied. Further, the outermost electrode plates 11A and 11B can output the current generated in the multilayer body 2 to the extraction portions 26A and 26B.

  Next, the configuration of the outermost electrode plates 11A and 11B in the power storage device 1 described above will be described in more detail. The thicknesses of the outermost electrode plates 11A and 11B are larger than the thicknesses of the other electrode plates 11 arranged on the inner side in the stacking direction. The extent to which the thicknesses of the outermost electrode plates 11A and 11B are larger than the thicknesses of the other electrode plates 11 is not particularly limited. For example, the thickness of the outermost electrode plates 11 </ b> A and 11 </ b> B may be an integer multiple of 2 or more compared to the thicknesses of the other electrode plates 11. Alternatively, the thickness of the outermost electrode plates 11 </ b> A and 11 </ b> B may be 1.5 times or more the thickness of the other electrode plates 11. By setting it as such a magnitude | size, outermost electrode plate 11A, 11B can have the intensity | strength which can endure the pressure difference of the internal pressure of the laminated body 2 and atmospheric pressure. The upper limit value of the thickness of the outermost electrode plates 11A and 11B is not particularly limited. For example, the thickness of the outermost electrode plates 11A and 11B may be 20 times or less the thickness of the other electrode plates 11. The thickness of the outermost electrode plate 11A and the thickness of the outermost electrode plate 11B are the same. However, the thickness of the outermost electrode plate 11A and the thickness of the outermost electrode plate 11B may be different as long as the performance is not affected.

  A configuration for increasing the thickness of the outermost electrode plates 11A and 11B will be described with reference to FIG. As shown in FIG. 2A, the outermost electrode plates 11 </ b> A and 11 </ b> B may be configured by a metal foil 36 that is thicker than the metal foil 36 that configures the other electrode plate 11. That is, the outermost electrode plates 11A and 11B are not formed by superimposing a plurality of metal foils 36 but by a single metal foil 36, and the thickness of the one metal foil 36 itself is the other electrode plate. 11 greater than the thickness of one metal foil 36. According to such a configuration, since the outermost electrode plates 11A and 11B are configured by a single metal foil 36, contact resistance between the metal foils 36 when a plurality of metal foils 36 are stacked does not occur. . Therefore, the electrical characteristics of the outermost electrode plates 11A and 11B can be stabilized.

  As shown in FIG. 2B, the outermost electrode plates 11 </ b> A and 11 </ b> B may include a metal foil 36 and a plating layer 37 formed on the surface of the metal foil 36. The plating layer 37 is a layer integrally formed on the surface of the metal foil 36. For example, the plating layer 37 may be made of a material such as tin or nickel. When forming tin plating, it may be formed on the surface of the metal foil 36 by electrolytic plating. In this case, the plating layer 37 may be formed on one side of the metal foil 36. When forming nickel plating, an electrolytic plating method or an electroless plating method may be employed. Therefore, the metal foil 36 with the plating layer 37 is different from a configuration in which another member is simply laminated on the surface of the metal foil 36. In particular, the material of the plating layer 37 is preferably a material whose strength is similar to that of the metal foil 36. The plated layer 37 is formed on one side of the metal foil 36 in FIG. 2B, but may be formed on both sides. In addition, when the material of the metal foil 36 is nickel and the material of plating is nickel, it may have a cross section as shown in FIG. With such a configuration, by adjusting the thickness of the plating layer 37, the thickness of the outermost electrode plates 11A and 11B can be easily adjusted.

  Moreover, as shown in FIG.2 (c), outermost electrode plate 11A, 11B may be comprised by the some metal foil 36 laminated | stacked. With such a configuration, it is possible to easily increase the thickness of the outermost electrode plates 11A and 11B only by stacking the plurality of metal foils 36. In FIG. 2C, the outermost electrode plates 11 </ b> A and 11 </ b> B are constituted by two metal foils 36. When the metal foil 36 of the other electrode plate 11 is used as the metal foil 36 per sheet, the outermost electrode plates 11A and 11B having a thickness twice that of the other electrode plate 11 can be easily manufactured. . Further, the thickness of the outermost electrode plates 11A and 11B can be increased by using components common to the other electrode plates 11. Accordingly, the ease of manufacturing the outermost electrode plates 11A and 11B can be improved.

  2 illustrates three configurations for increasing the thickness of the outermost electrode plates 11A and 11B, but any configuration or all configurations may be combined with each other.

  Next, the operation and effect of the power storage device 1 according to this embodiment will be described.

  In this power storage device 1, among the electrode plates 11 included in the stacked body 2, the thicknesses of the outermost electrode plates 11 </ b> A and 11 </ b> B disposed on the outermost side in the stacking direction are the other electrode plates disposed on the inner side in the stacking direction. It is larger than 11 thickness. That is, the outermost electrode plates 11A and 11B receive a force that induces deformation outward in the stacking direction due to the influence of the differential pressure between the internal pressure and the atmospheric pressure of the stacked body 2 in the seal portion 4, The electrode plates 11 </ b> A and 11 </ b> B are thicker and stronger than the other electrode plates 11. Therefore, deformation due to the influence of the force acting on the outermost electrode plates 11A and 11B can be suppressed. Thereby, the reliability of the power storage device 1 can be improved.

  Moreover, since the thickness of the outermost electrode plates 11A and 11B is large, the outermost electrode plates 11A and 11B can secure a distance for enlarging or converging the current path. In the configuration shown in FIG. 1, the current generated in the laminated body 2 flows through the outermost electrode plate 11B and the current collector plate 25B and converges toward the extraction portion 31B. At this time, since the thickness of the outermost electrode plate 11B is large, a sufficient distance can be secured for the current to converge. Further, the current flowing from the extraction portion 31A flows through the outermost electrode plate 11A and the current collector plate 25A and diffuses toward the laminate. At this time, since the thickness of the outermost electrode plate 11A is large, it is possible to secure a sufficient distance for the current to expand. As described above, power generation unevenness in the bipolar electrode 3 can be reduced.

  The outermost electrode plates 11A and 11B are supported by the current collecting plates 25A and 25B (or the restraining plates 21A and 21B described later), so that deformation that causes breakage can be prevented. Even in such a case, the merit of increasing the thickness of the outermost electrode plates 11A and 11B will be described with reference to FIG. As shown in FIG. 3, even if the outermost electrode plates 11A and 11B and the electrode plate 11 in the state before deformation (the upper stage side in FIG. 3) have the same size in the lateral direction, the internal pressure and the atmospheric pressure. The outermost electrode plates 11A and 11B having a larger thickness have a larger amount of lateral protrusion when deformed due to the differential pressure (see the state on the lower side of FIG. 3). As a result, the outermost electrode plates 11 </ b> A and 11 </ b> B have a longer seal length that bites into the seal portion 4 than the electrode plate 11. Thereby, the sealing performance of the outermost electrode plates 11A and 11B can be improved.

  The present invention is not limited to the above embodiment. For example, the restraining plates 21A and 21B may have a restraining function and a current collecting function.

  Specifically, as shown in FIG. 4, the restraining member 5 of the power storage device 100 includes a pair of restraining plates 21A and 21B, and a connecting member (bolt 22 and nut 23) that connects the restraining plates 21A and 21B. It is comprised by extraction part 31A, 31B which takes out an electric current from restraint board 21A, 21B. The restraint plates 21A and 21B are formed in a flat plate shape with a conductive material such as iron or aluminum. An insertion hole 21a through which the bolt 22 is inserted is provided at a position on the outer side of the seal portion 4 at the edge of the restraint plates 21A and 21B. The insertion hole 21a is formed by embedding a cylindrical insulating member 32 in the restraining plates 21A and 21B.

  Here, the restraining plates 21 </ b> A and 21 </ b> B have both a restraining function for restraining the stacked body 2 and a current collecting function for collecting current generated by the stacked body 2. Accordingly, the inner surface 21 b in the stacking direction of the one restraining plate 21 </ b> A is in contact with the outermost electrode plate 11 </ b> A in the inner region of the seal portion 4. The inner surface 21b in the stacking direction of the other restraining plate 21B is in contact with the outermost electrode plate 11A in the inner region of the seal portion 4. Here, since the insertion hole 21a is formed in the insulating member 32, the bolt 22 (including the head portion 22a of the bolt 22) and the nut 23 are electrically insulated from the restraining plates 21A and 21B. The insulating member 32 may be provided on the bolt 22 side, and the insulating member 32 may be attached to the restraining plates 21A and 21B when restraining.

  The extraction portion 31A is connected to the restraining plate 21A. The extraction portion 31A is connected to the outer surface 21c in the stacking direction of the restraining plate 21A. Further, the take-out portion 31A is connected to the center position on the surface 21c of the restraining plate 21A. However, the connection position of the extraction portion 31A is not particularly limited, and may be any position on the surface 21c, or may be provided at a position other than the surface 21c, such as the side surface of the restraining plate 21A. The extraction part 31B is connected to the restraint plate 21B. The take-out portion 31B is connected to the outer surface 21c in the stacking direction of the restraining plate 21B. Further, the take-out part 31B is connected to the center position on the surface 21c of the restraining plate 21B. However, the connection position of the extraction portion 31B is not particularly limited, and may be any position on the surface 21c, and may be provided at a position other than the surface 21c, such as the side surface of the restraint plate 21B.

  Thereby, the laminate 2, the outermost electrode plates 11A and 11B, and the seal portion 4 are sandwiched and unitized, and a restraining load is applied. Further, the outermost electrode plates 11A and 11B can output the current generated in the multilayer body 2 to the extraction portions 31A and 31B.

  As described above, the power storage device 100 according to the modification further includes the pair of restraining plates 21A and 21B that restrain the stacked body 2 from the outside in the stacking direction, and the restraining plates 21A and 21B are in contact with the outermost electrode plates 11A and 11B. In addition, it is connected to extraction portions 31A and 31B for extracting current. With such a configuration, the restraint plates 21A and 21B can support the outermost electrode plates 11A and 11B that are to be deformed outward in the stacking direction due to the influence of the differential pressure between the internal pressure and the atmospheric pressure. Therefore, the restraining plates 21A and 21B can suppress deformation of the outermost electrode plates 11A and 11B.

  The constraining plates 21A and 21B have a function of constraining the stacked body 2 and can also serve as a current collecting function of collecting current generated in the stacked body. The restraining plates 21A and 21B are members having a certain thickness in order to have a restraining function. Therefore, the restraining plates 21A and 21B can secure a distance for enlarging or converging the current path between the extraction portions 31A and 31B and the outermost electrode plates 11A and 11B. Thereby, the nonuniformity of the electric power generation in the bipolar electrode 3 can be reduced. In the configuration shown in FIG. 4, the current generated in the stacked body 2 flows through the outermost electrode plate 11 </ b> B and the restraining plate 21 </ b> B and converges toward the extraction portion 31 </ b> B. At this time, since the thickness of the outermost electrode plate 11B and the restraint plate 21B is large, a sufficient distance can be secured for the current to converge. Further, the current flowing from the extraction portion 31A flows through the outermost electrode plate 11A and the restraint plate 21A and diffuses toward the laminate. At this time, since the thickness of the outermost electrode plate 11A and the restraint plate 21A is large, it is possible to secure a sufficient distance for the current to expand. As described above, power generation unevenness in the bipolar electrode 3 can be reduced.

  DESCRIPTION OF SYMBOLS 1,100 ... Power storage device, 3 ... Bipolar electrode, 4 ... Seal part, 6 ... Separator, 11 ... Electrode plate, 11A, 11B ... Outermost electrode plate, 12 ... Positive electrode, 13 ... Negative electrode, 21A, 21B ... Restraint plate, 31A, 31B ... Extracting section.

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 alternately laminating the bipolar electrodes via separators;
Of the laminate, at least a seal portion formed between the edges of the electrode plates,
Of the electrode plates included in the stacked body, the thickness of the outermost electrode plate disposed on the outermost side in the stacking direction is larger than the thickness of other electrode plates disposed on the inner side in the stacking direction. .   The power storage device according to claim 1, wherein the outermost electrode plate includes a plurality of laminated metal foils.   The power storage device according to claim 1, wherein the outermost electrode plate includes a metal foil and a plating layer formed on a surface of the metal foil.   The power storage device according to claim 1, wherein the outermost electrode plate is configured by a metal foil having a thickness larger than that of the metal foil configuring the other electrode plate. A pair of restraining plates for restraining the laminate from outside in the stacking direction;
5. The power storage device according to claim 1, wherein the constraining plate is in contact with the outermost electrode plate and is connected to an extraction unit that extracts current.

Images