Bipolar battery, current collector, and method for manufacturing bipolar battery

Abstract

This bipolar battery comprises: a current collector including a base material formed of a thermoplastic resin film, a first conductive layer formed on a first surface of the base material, and a second conductive layer formed on a second surface of the base material; a first electrode layer corresponding to one of a positive electrode and a negative electrode and laminated on the first conductive layer; a second electrode layer corresponding to the other of the positive electrode and the negative electrode and laminated on the second conductive layer; and an electrolyte layer provided for a bipolar electrode including the current collector, the first electrode layer, and the second electrode layer. In the current collector, a plurality of through-holes extending between the first surface and the second surface over the shortest distance are formed in the base material. At least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through-holes, and the first conductive layer and the second conductive layer are electrically connected.

Description

Bipolar battery, current collector, and method for manufacturing a bipolar battery

[0001] This disclosure relates to a bipolar battery, a current collector, and a method for manufacturing a bipolar battery. This application claims priority under Japanese Patent Application No. 2025-50898, filed in Japan on March 26, 2025, the contents of which are incorporated herein by reference.

[0002] Conventionally, various current collectors for batteries and batteries containing such current collectors are known. For example, Patent Document 1 discloses a current collector comprising a substrate with through holes, lead layers formed on both sides of the substrate, and a conductive element arranged in the through holes.

[0003] Japanese Patent Publication No. 2022-122593

[0004] According to some aspects of this disclosure, it is possible to provide a lightweight bipolar battery with high energy density, a current collector, and a method for manufacturing a bipolar battery.

[0005] One aspect of the present disclosure relates to a bipolar battery comprising: a substrate formed of a thermoplastic resin film; a current collector including a first conductive layer formed on a first surface of the substrate and a second conductive layer formed on a second surface of the substrate opposite to the first surface; a first electrode layer corresponding to one of the positive and negative electrodes and laminated on the first conductive layer; a second electrode layer corresponding to the other of the positive and negative electrodes and laminated on the second conductive layer; and an electrolyte layer provided for a bipolar electrode composed of the current collector, the first electrode layer and the second electrode layer, wherein the current collector has a plurality of through holes formed in the substrate that connect the first surface and the second surface of the substrate by the shortest distance, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes, and the first conductive layer and the second conductive layer are electrically connected.

[0006] Other aspects of the present disclosure include a substrate formed of a thermoplastic resin film, a first conductive layer formed on a first surface side of the substrate, and a second conductive layer formed on a second surface side which is the surface opposite to the first surface of the substrate, wherein the substrate has a plurality of through holes formed thereon that connect the first surface and the second surface of the substrate by the shortest distance, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes, the first conductive layer and the second conductive layer are electrically connected, and each of the plurality of through holes relates to a current collector which, in plan view, has a non-circular shape in which the length in a first direction corresponding to the stretching direction of the thermoplastic resin film is longer than the length in a second direction perpendicular to the first direction.

[0007] A further aspect of the present disclosure includes a substrate formed of a thermoplastic resin film, a first conductive layer formed on a first surface of the substrate, and a second conductive layer formed on a second surface of the substrate opposite to the first surface, wherein the substrate has a plurality of through holes formed thereon that connect the first surface and the second surface of the substrate by the shortest distance, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes, the first conductive layer and the second conductive layer are electrically connected, and the first conductive layer and the second conductive layer relate to a current collector each formed of a different metal.

[0008] Further aspects of the present disclosure relate to a method for manufacturing a bipolar battery, comprising forming a battery structure including a current collector, a first electrode layer corresponding to one of a positive electrode and a negative electrode, a second electrode layer corresponding to the other of the positive electrode and the negative electrode, and an electrolyte layer, and stacking a plurality of the battery structures, wherein forming the battery structure includes forming a plurality of through holes in a substrate made of a thermoplastic resin film that connect a first surface of the substrate and a second surface which is the surface opposite to the first surface by the shortest distance, forming a first conductive layer on the first surface side of the substrate, forming a second conductive layer on the second surface side of the substrate, forming the first electrode layer so as to be stacked on the first conductive layer, forming the electrolyte layer so as to be stacked on the first electrode layer, and forming the second electrode layer so as to be stacked on the electrolyte layer or the second conductive layer, wherein in at least one of the formation of the first conductive layer and the formation of the second conductive layer, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes.

[0009] This is a cross-sectional view showing an example of the configuration of a battery according to this embodiment. This is a perspective view showing an example of the configuration of a current collector. This is a cross-sectional view showing an example of the configuration of a current collector. This is a plan view of a current collector, illustrating a plurality of through holes. This is a cross-sectional view illustrating another example of the configuration of a current collector. This is a cross-sectional view illustrating another example of the configuration of a current collector. This is a cross-sectional view illustrating another example of the configuration of a current collector. This is a perspective view illustrating another example of the configuration of a current collector. This is a cross-sectional view showing an example of the configuration of a current collector shown in Figure 9A. This is a perspective view illustrating the step of forming through holes in a substrate. This is a cross-sectional view illustrating the step of forming through holes in a substrate. This is a perspective view illustrating the step of forming a first conductive layer and a second conductive layer. This is a cross-sectional view illustrating the step of forming a first conductive layer and a second conductive layer. This is a perspective view illustrating the step of forming a first electrode layer. This is a cross-sectional view illustrating the step of forming an electrolyte layer. This is a cross-sectional view illustrating the step of forming a second electrode layer. This is a cross-sectional view illustrating the step of forming a second electrode layer. This is a perspective view illustrating the step of stacking a plurality of battery structures. This is a cross-sectional view illustrating the step of stacking a plurality of battery structures. This is a cross-sectional view illustrating the step of forming an extraction electrode and the step of sealing the whole with a sealing member.

[0010] This embodiment will be described below with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. This embodiment described below is not intended to unduly limit the content described in the claims. Furthermore, not all of the configurations described in this embodiment are essential components of this disclosure.

[0011] 1. Example of Battery Configuration Figure 1 is a cross-sectional view showing an example of the configuration of a battery including the current collector 100 according to this embodiment. The battery according to this embodiment may be a bipolar battery 10. As shown in Figure 1, the bipolar battery 10 includes a current collector 100, a first electrode layer 200, a second electrode layer 300, and an electrolyte layer 400.

[0012] Here, the axis in the direction in which the current collector 100, the first electrode layer 200, the second electrode layer 300, and the electrolyte layer 400 are stacked is defined as the z-axis. The two axes perpendicular to the z-axis are defined as the x-axis and y-axis. The directions of the x, y, and z axes are the same in all subsequent figures from Figure 2 onward.

[0013] The structure of the current collector 100 will be described later with reference to Figures 2 and 3.

[0014] The first electrode layer 200 corresponds to one of the positive and negative electrodes and is laminated on one side of the current collector 100. The second electrode layer 300 corresponds to the other of the positive and negative electrodes and is laminated on the other side of the current collector 100. For example, the first electrode layer 200 is in contact with one side of the current collector 100, and the second electrode layer 300 is in contact with the other side of the current collector 100. As shown in Figure 1, the current collector 100 may be a bipolar current collector that functions as both a current collector for the positive electrode and a current collector for the negative electrode. In the example in Figure 1, the second electrode layer 300, the current collector 100, and the first electrode layer 200 are laminated in this order in a given lamination direction to form a bipolar electrode 30 in which one side functions as the positive electrode and the other side functions as the negative electrode. The lamination direction here refers to, for example, the direction along the z-axis, and more narrowly, the positive z-axis direction.

[0015] For example, the first electrode layer 200 is an electrode layer for the negative electrode. The first electrode layer 200 is composed of a carbon-based active material such as graphite or hard carbon and an electrolyte. However, the material of the first electrode layer 200 is not limited to this, and a wide range of known materials suitable for the negative electrode can be applied. Also, in an anode-free structure, the negative electrode does not contain an active material. The second electrode layer 300 is an electrode layer for the positive electrode. The second electrode layer 300 is composed of an active material such as lithium cobalt oxide, lithium titanate, lithium sulfide, sodium chromate, sodium vanadium phosphate, an electrolyte and a conductive additive such as acetylene black or carbon nanotubes. However, the material of the second electrode layer 300 is not limited to this, and a wide range of known materials suitable for the positive electrode can be applied. Also, the positive and negative electrodes are not limited to this example, and the first electrode layer 200 may be an electrode layer for the positive electrode and the second electrode layer may be an electrode layer for the negative electrode.

[0016] The electrolyte layer 400 is provided on a bipolar electrode 30 composed of a current collector 100, a first electrode layer 200, and a second electrode layer 300. For example, when a battery structure 20 is defined as a structure in which a current collector 100, a first electrode layer 200, an electrolyte layer 400, and a second electrode layer 300 are stacked in this order in a given stacking direction, the bipolar battery 10 has a structure in which a plurality of the battery structures 20 are stacked in the stacking direction. In the example of Fig. 1, the bipolar battery 10 includes two bipolar electrodes 30 formed by stacking three layers of the battery structures 20, and three electrolyte layers 400 alternately stacked with the two bipolar electrodes 30. An electrode formed of the current collector 100 and the second electrode layer 300 (e.g., a positive electrode), an electrode formed of the current collector 100 and the first electrode layer 200 (e.g., a negative electrode), and the electrolyte layer 400 sandwiched between the two electrodes function as one battery. The bipolar battery 10 shown in Fig. 1 has a structure in which three such batteries are connected in series in the stacking direction.

[0017] In the example of Fig. 1, an example where the bipolar battery 10 has three stacked battery structures 20 is shown, but the number of stacked battery structures 20 is not limited thereto, and may be two or four or more.

[0018] The electrolyte layer 400 according to the present embodiment is, for example, a solid electrolyte layer. According to this configuration, a solid battery (all-solid-state battery) can be used as the bipolar battery 10 according to the present embodiment.

[0019] As materials for the solid electrolyte layer, sulfides, oxides, hydrides, halide-based materials, and polymer-based materials are known, and Na-based and Li-based materials are known for each of these categories, respectively.

[0020] The sulfide-based solid electrolyte layer may be a Na-based Na ３ PS ４ , Na ３ SbS ４ , Na １１ Sn ２ PS １２ , or may be any one of the above, and may also be Li-based Li １０ GeP ２ S １２ , Li １０ (Ge ０．５ Sn０．５ ) P ２ S １２ Li １０ SnP ２ S １２ It may be any of these, or it may be a sulfide different from any of these.

[0021] The oxide-based solid electrolyte layer is Na-based β''-Al ２ O ３ , Na ３ Zr ２ Si ２ PO １２ , Na ３．３ Zr １．９ Nb ０．１ Si ２．４ P ０．６ O １２ Either of these is fine, or Li-based Li １．３ Al ０．３ Ti １．７ (PO ４ ) ３ Li ０．４ ZLa ３ Zr １．４ Ta ０．６ O １２ Li ７ La ３ Zr ２ O １２ It may be any of these, or it may be an oxide different from any of these.

[0022] The hydride-based solid electrolyte layer is Na-based. ２ B １０ H １０ , Na ２ B １２ H １２ NaCB １１ H １２ , Na ２ (B １０ H １０ ) ０．５ (B １２ H １２ ) ０．５ , Na ２ (CB ９ H １０ ) (CB １１ H １２ ), Na ２ (BH ４ ) (NH２ ), (Na ４ B ３６ H ３４ )7 (Na ２ B １２ H １２ ), may be any of the above, or may be Li-based Li ２ (B １０ H １０ ) ０．５ (B １２ H １２ ) ０．５ , 0.7Li(CB ９ H １０ ) 0.3Li (CB １１ H １２ ), 0.75Li (BH ４ ) 0.25LiI, or may be a hydride different from any of these.

[0023] The halide-based solid electrolyte layer may be Na-based NaInCl ６ , NaTaCl ６ , Na ２．５ Y ０．５ Zr ０．５ Cl ６ , Na ２．８ In ０．８ Zr ０．２ Cl ６ , or may be Li-based Li ３ InCl ６ , LiNbOCl ４ , LiTaOCl ４ , or may be a halide-based electrolyte different from any of these.

[0024] The polymer-based solid electrolyte layer may be Na-based PVDF / HE gel, polymer (PEO)-NaTFSI, or may be Li-based polymer (PEO)+LiTFSI, or may be a polymer-based electrolyte different from any of these.

[0025] However, the electrolyte layer 400 according to the present embodiment is not limited to a solid electrolyte, and may be an electrolyte composed of a liquid electrolyte and a separator, or may be an electrolyte with other configurations.

[0026] 2. Example of Current Collector Configuration An example of the configuration of the current collector 100 according to this embodiment will be described using Figures 2-3. Figure 2 is a perspective view showing an example of the configuration of the current collector 100. Figure 3 is a cross-sectional view showing an example of the configuration of the current collector 100.

[0027] As shown in Figures 2 and 3, the current collector 100 includes a base material 110, a first conductive layer 130, and a second conductive layer 150. The base material 110 is formed from a thermoplastic resin film. The base material 110 has a first surface 111, which is one of the film surfaces, and a second surface 112, which is the surface opposite to the first surface 111. The first surface 111 and the second surface 112 are surfaces corresponding to the xy plane defined by the x and y axes, and in a narrow sense, they may be surfaces parallel to the xy plane.

[0028] The thermoplastic resin film constituting the base material 110 is made of, for example, PI (polyimide), PC (polycarbonate), COP (cycloolefin polymer), or PET (polyethylene terephthalate). However, the thermoplastic resin film may be made of other known materials. By using a thermoplastic resin film as the base material 110, the current collector 100 can be made lighter compared to when a base material such as metal is used. Therefore, it becomes possible to increase the energy density per unit weight of the bipolar battery 10 including the current collector 100.

[0029] The first conductive layer 130 is formed on the first surface 111 side of the substrate 110. Forming the first conductive layer 130 on the first surface 111 side may mean that the first conductive layer 130 is directly formed on the first surface 111, in other words, that the first conductive layer 130 and the first surface 111 are in contact. Alternatively, forming the first conductive layer 130 on the first surface 111 side may mean that the first conductive layer 130 is formed on the first surface 111 via other layers. In other words, one or more layers may be formed on the first surface 111, and the first conductive layer 130 may be formed in contact with the uppermost layer.

[0030] The second conductive layer 150 is formed on the second surface 112 side of the substrate 110. The formation of the second conductive layer 150 on the second surface 112 side may mean that the second conductive layer 150 is formed directly on the second surface 112, or it may mean that the second conductive layer 150 is formed on the second surface 112 via another layer.

[0031] As shown in Figures 2 and 3, the base material 110 has a plurality of through holes 115 that connect the first surface 111 and the second surface 112 of the base material 110 by the shortest distance. The statement that the through holes 115 connect the first surface 111 and the second surface 112 by the shortest distance means that the shortest distance between a point on the opening of the through hole 115 on the first surface 111 side and a point on the opening of the same through hole 115 on the second surface 112 side is equal to the thickness of the base material 110. Alternatively, the statement that the through holes 115 connect the first surface 111 and the second surface 112 by the shortest distance may mean that the inner wall 116 of the through hole 115 is oriented in a direction aligned with the normal direction of the first surface 111 and the second surface 112. The normal direction of the first surface 111 and the second surface 112 is, for example, the z-axis direction.

[0032] By forming multiple through holes 115 that connect the first surface 111 and the second surface 112 with the shortest distance, the volume of holes formed in the base material 110 can be reduced, thereby increasing the mechanical strength of the base material 110. Furthermore, by shortening the distance between the first surface 111 and the second surface 112 through the through holes 115, the electrical resistance between the two surfaces (electrical resistance in the thickness direction of the current collector 100) can be reduced. In the bipolar battery 10 shown in Figure 1, multiple batteries are connected in series in the bipolar electrode 30, so by suppressing the electrical resistance in the thickness direction, the performance of the bipolar battery 10 can be improved.

[0033] Furthermore, at least one of the first conductive layer 130 and the second conductive layer 150 is formed on the inner wall 116 of each of the multiple through holes 115, and the first conductive layer 130 and the second conductive layer 150 are electrically connected. In the example shown in Figure 3, the first conductive layer 130 is formed in the region of the inner wall 116 closest to the first surface 111, and the second conductive layer 150 is formed in the region of the inner wall 116 closest to the second surface 112, and the first conductive layer 130 and the second conductive layer 150 are in contact with each other on the inner wall 116, thereby achieving electrical connection. In this way, one electrode (part of the current collector 100 and the first electrode layer 200) and the other electrode (part of the current collector 100 and the second electrode layer 300) of the bipolar electrode 30 are electrically connected, making it possible to form a bipolar battery 10 in which multiple batteries are connected in series in the stacked structure shown in Figure 1. Furthermore, since at least one of the first conductive layer 130 and the second conductive layer 150 is formed on the inner wall 116, unlike in Patent Document 1, there is no need to provide a separate conductive body for electrical connection. Therefore, the structure of the current collector 100 can be simplified.

[0034] In the bipolar battery 10 shown in Figure 1, four current collectors 100 are illustrated, but these may all be current collectors with the same structure. That is, the four current collectors 100 shown in Figure 1 may all have the structure described above using Figures 2 and 3. In this case, the current collector 100 functions as a current collector for a bipolar electrode 30 when the first electrode layer 200 is laminated on one side and the second electrode layer 300 is laminated on the other side. Also, as shown in the upper and lower current collectors 100 of Figure 1, the current collector 100 may function as an electrode with one polarity by laminating only one of the first electrode layer 200 and the second electrode layer 300 on the current collector 100.

[0035] Alternatively, instead of the current collectors 100 at the upper and lower ends of Figure 1, current collectors having a different structure from the one described above may be used, as shown in Figures 2 and 3, and which correspond to only one of the positive or negative electrodes. For example, instead of the current collector 100 at the upper end of Figure 1, a current collector for the polarity corresponding to the second electrode layer 300 (e.g., positive electrode) may be used. Similarly, instead of the current collector 100 at the lower end of Figure 1, a current collector for the polarity corresponding to the first electrode layer 200 (e.g., negative electrode) may be used. In this case, the current collectors at the upper and lower ends may be current collectors made of a conductor without through holes.

[0036] Thus, the multiple current collectors included in the bipolar battery 10 may all have the same structure, or they may include current collectors with different structures.

[0037] 3. Other Examples of Current Collector Configurations The following describes other examples of current collector structures.

[0038] 3.1 Figure 4 is a plan view of the current collector 100 and illustrates the shape of the multiple through holes 115. As shown in Figure 4, each of the multiple through holes 115 may have a non-circular shape in a plan view, where the length in the first direction corresponding to the stretching direction of the thermoplastic resin film is longer than the length in the second direction perpendicular to the first direction. Here, a plan view refers to observing the film surface (a surface parallel to the xy plane) of the substrate 110, which is a film (thin film), from a viewpoint set at a distance in the film thickness direction (normal direction, z-axis direction). The thermoplastic resin film constituting the substrate 110 may be a stretched film produced by winding the film on a roll while pulling it in a predetermined direction. In this case, the stretching direction of the thermoplastic resin film may mean the direction in which it is pulled during winding, or it may mean the winding direction of the stretched film. The stretching direction may also mean the direction in which the resin molecules contained in the thermoplastic resin film are oriented. In the example in Figure 4, the first direction is, for example, the direction along the x-axis, and the second direction is the direction along the y-axis. Furthermore, a non-circular shape may be, for example, an ellipse, a flattened circle, or any other shape that satisfies the above-mentioned length conditions.

[0039] By forming the through-hole 115, the weight of the current collector 100 can be reduced and electrical connection between the first conductive layer 130 and the second conductive layer 150 can be made possible, but there is a possibility that the mechanical strength will decrease. In this respect, in the method of this embodiment, by making the through-hole 115 a shape in which the length in the stretching direction of the film is relatively long, it is possible to suppress the tearing of the base material 110 even if tensile stress is applied to the base material 110 during the manufacturing process of the current collector 100 and the bipolar battery 10.

[0040] Furthermore, by making the shape of the through-hole 115 non-circular, the area of ​​the inner wall 116 of the through-hole 115 can be increased for the same opening area compared to forming a perfectly circular through-hole. As a result, it becomes possible to reduce the electrical resistance value in the thickness direction of the current collector 100 (the resistance value between the first surface 111 and the second surface 112).

[0041] As shown in Figure 4, multiple through holes 115 may be formed on each of the first surface 111 and the second surface 112 of the base material 110 such that the area of ​​the parts other than the through holes 115 is larger than the total area of ​​the multiple through holes 115. In this way, the in-plane resistance is reduced on each of the first surface 111 and the second surface 112 of the base material 110, making it possible to equalize the battery reaction within the plane of the current collector 100. For example, in the current collector 100 according to this embodiment, the in-plane resistance value of the current collector 100 is lower than the resistance value in the thickness direction. However, the shape and area of ​​the through holes 115 in this embodiment are not limited to the example in Figure 4, and for example, the through holes 115 may be perfectly circular.

[0042] The method of this embodiment is not limited to that applied to the bipolar battery 10 described above using Figure 1. The method of this embodiment may also be applied to a current collector 100. As shown in Figures 2-3, the current collector 100 includes a base material 110 formed of a thermoplastic resin film, a first conductive layer 130 formed on the first surface 111 side of the base material 110, and a second conductive layer 150 formed on the second surface 112 side, which is the opposite side of the first surface 111 of the base material 110. The base material 110 has a plurality of through holes 115 that connect the first surface 111 and the second surface 112 of the base material 110 by the shortest distance, and at least one of the first conductive layer 130 and the second conductive layer 150 is formed on the inner wall 116 of each of the plurality of through holes 115, and the first conductive layer 130 and the second conductive layer 150 are electrically connected. As shown in Figure 4, each of the multiple through holes 115 has a non-circular shape in plan view, where the length in the first direction corresponding to the stretching direction of the thermoplastic resin film is longer than the length in the second direction perpendicular to the first direction.

[0043] 3.2 First Conductive Layer and Second Conductive Layer The details of the first conductive layer 130 and the second conductive layer 150 will be described below. Note that the combination of each embodiment described below with other embodiments (for example, the shape of the through hole 115) is arbitrary. For example, in the current collector 100 described below, the shape of the through hole 115 may be non-circular or circular.

[0044] The first conductive layer 130 and the second conductive layer 150 in this embodiment may each be a metal film formed from a metal. For example, the first conductive layer 130 and the second conductive layer 150 may be metal films formed from the same metal. Specifically, the first conductive layer 130 and the second conductive layer 150 may be Ni, Cu, Al, Au, Pt, or Ag. In this case, the inner wall 116 of the through hole 115 is entirely covered by the metal films constituting the first conductive layer 130 and the second conductive layer 150. In this way, the conductive layer for the positive electrode and the conductive layer for the negative electrode can be formed from the same metal, which simplifies the structure of the current collector and makes manufacturing easier.

[0045] Alternatively, the first conductive layer 130 and the second conductive layer 150 may be formed from different metals. For example, the conductive layer for the positive electrode (the second conductive layer 150 in the narrow sense) may be one of Ni, Cu, Al, Au, Pt, or Ag, and the conductive layer for the negative electrode (the first conductive layer 130 in the narrow sense) may be a different metal from the conductive layer for the positive electrode among Ni, Cu, Al, Au, Pt, and Ag. In this way, it becomes possible to use metals suitable for the corresponding polarity as the first conductive layer 130 and the second conductive layer 150. As a result, it becomes possible to improve the performance of the battery (the bipolar battery 10 in the narrow sense) including the current collector 100.

[0046] If the first conductive layer 130 and the second conductive layer 150 are formed from different metals, as shown in Figure 3, both the first conductive layer 130 and the second conductive layer 150 may be formed on the inner wall 116 of each of the multiple through holes 115, and the first conductive layer 130 and the second conductive layer 150 may be electrically connected by contact at the inner wall 116.

[0047] Furthermore, the first conductive layer 130 and the second conductive layer 150 may each or both be formed as a coating film containing a conductive filler. The conductive filler may be carbon-based (e.g., carbon nanotubes), metal-based, or metal oxide-based. The conductive filler may be in the form of fibers, for example, but conductive fillers in other forms such as powder may also be used. In addition to the conductive filler, the coating film may also contain a resin material.

[0048] Figure 5 is a cross-sectional view illustrating another configuration example of the current collector 100. As shown in Figure 5, only the first conductive layer 130 may be formed on the inner wall 116 of each of the multiple through holes 115. The first conductive layer 130 formed on the inner wall 116 and the second conductive layer 150 formed on the second surface 112 come into contact, thereby electrically connecting the first conductive layer 130 and the second conductive layer 150.

[0049] Figure 6 is a cross-sectional view illustrating another configuration example of the current collector 100. As shown in Figure 6, the first conductive layer may be formed on the inner wall 116 and the second surface 112 of each of the multiple through holes 115. In other words, the first conductive layer 130 is formed to cover the first surface 111, the inner wall 116, and the second surface 112. As shown in Figure 6, the first conductive layer 130 and the second conductive layer 150 may be electrically connected by laminating them in this order on the second surface 112 of the substrate 110.

[0050] As shown in Figures 3, 5, and 6, in this embodiment, the first conductive layer 130 and the second conductive layer 150 are electrically connected by forming either one or both of them on the inner wall 116 of the through hole 115. Various modifications can be made to the specific structure in this case.

[0051] Figure 7 is a cross-sectional view illustrating another configuration example of the current collector 100. The current collector 100 according to this embodiment may further include a third conductive layer 170 formed from a material different from both the first conductive layer 130 and the second conductive layer 150. In the example of Figure 7, the first conductive layer 130 is formed to cover the first surface 111, the inner wall 116, and the second surface 112, similar to the example of Figure 6. Then, on the second surface 112 of the substrate 110, the first conductive layer 130, the third conductive layer 170, and the second conductive layer 150 are laminated on the substrate 110 in this order, so that the first conductive layer 130 and the second conductive layer 150 are electrically connected via the third conductive layer 170. In this way, since the first conductive layer 130, which is a given metal, and the second conductive layer 150, which is a different metal from the first conductive layer 130, do not come into contact, it is possible to suppress the contact reaction between the first conductive layer 130 and the second conductive layer 150. The contact reaction referred to here is, for example, corrosion due to contact between dissimilar metals (galvanic corrosion). It is known that corrosion is more likely to occur when the electrochemical potential of dissimilar metals is 0.6V or higher. Therefore, in a configuration where the first conductive layer 130 and the second conductive layer 150 are in contact, it is not preferable to use a combination of copper and aluminum, for example, which have an electrochemical potential of 0.65V, as these conductive layers. In contrast, with the configuration shown in Figure 7, since the first conductive layer 130 and the second conductive layer 150 are not in contact, it is possible to use dissimilar metals with high electrochemical potentials as the metals forming these two conductive layers. For example, aluminum can be selected as the first conductive layer 130 and copper as the second conductive layer 150. In this case, for example, by using lead as the third conductive layer 170, the electrochemical potential of copper and lead (0.3V) and the electrochemical potential of lead and aluminum (0.35V) can be lowered, so that corrosion due to contact between dissimilar metals can be suppressed while using metals suitable for each electrode. Furthermore, since the third conductive layer 170 is formed in a film-like manner on the second surface 112, it can be easily formed by the same process as the first conductive layer 130 and the second conductive layer 150 (for example, by vapor deposition or plating as described later).

[0052] Figure 8 is a cross-sectional view illustrating another configuration example of the current collector 100. When the current collector 100 includes a third conductive layer 170, the third conductive layer 170 may be formed not only on the second surface 112 as shown in Figure 8, but also on the first surface 111 and the inner walls 116 of each of the multiple through holes 115, so as to cover the first conductive layer 130. In this case, the area over which the third conductive layer 170 is formed will increase, but the contact reaction between the first conductive layer 130 and the second conductive layer 150 can be suppressed, just as in the example in Figure 7. Also, just as in the example in Figure 7, the third conductive layer 170 can be easily formed by the same process as the first conductive layer 130 and the second conductive layer 150 (for example, vapor deposition or plating, which will be described later).

[0053] The method of this embodiment may also be applied to the following current collector 100. As shown in Figures 2-3, the current collector 100 includes a base material 110 formed of a thermoplastic resin film, a first conductive layer 130 formed on the first surface 111 side of the base material 110, and a second conductive layer 150 formed on the second surface 112 side, which is the opposite side of the first surface 111 of the base material 110. The base material 110 has a plurality of through holes 115 that connect the first surface 111 and the second surface 112 of the base material 110 by the shortest distance, and at least one of the first conductive layer 130 and the second conductive layer 150 is formed on the inner wall 116 of each of the plurality of through holes 115, and the first conductive layer 130 and the second conductive layer 150 are electrically connected. As shown in Figure 3, or any of Figures 5-8, the first conductive layer 130 and the second conductive layer 150 are each formed from different metals.

[0054] 3.3 Conductive Filler Figure 9A is a perspective view showing another example of the configuration of the current collector 100, and Figure 9B is a cross-sectional view showing the example of the configuration of the current collector 100 shown in Figure 9A. Components that overlap with the above-described configurations using other figures are denoted by the same reference numerals, and detailed explanations are omitted. In Figure 9B, the configuration of the first conductive layer 130 and the second conductive layer 150 is exemplified as in Figure 3, but the first conductive layer 130 and the second conductive layer 150 may be configured as described above using any of Figures 5 to 8. Furthermore, the shape of the through hole 115 can be combined with any of the above-described embodiments.

[0055] As shown in Figures 9A and 9B, the base material 110 may be a thermoplastic resin film compounded with a conductive filler 190. The conductive filler 190 may be carbon-based, metal-based, or metal oxide-based. The conductive filler 190 is, for example, fibrous, but other forms of conductive filler, such as powder, may also be used. By compounding the conductive filler 190 into the base material 110, it is possible to increase the conductivity between one surface of the current collector 100 (first surface 111, first conductive layer 130) and the other surface (second surface 112, second conductive layer 150). Since the resistance value in the thickness direction of the current collector 100 is reduced, it is possible to improve the performance of the battery including the current collector 100.

[0056] 4. The method for manufacturing the battery and the method of this embodiment are not limited to those applied to the bipolar battery 10 or current collector 100 described above, but may also be applied to the method for manufacturing the bipolar battery 10.

[0057] The manufacturing method according to this embodiment includes forming a battery structure 20 and stacking a plurality of battery structures 20. The battery structure 20 includes a current collector 100, a first electrode layer 200 corresponding to one of the positive and negative electrodes, a second electrode layer 300 corresponding to the other of the positive and negative electrodes, and an electrolyte layer 400. The specific steps will be described below.

[0058] Figures 10A-14B illustrate the steps for forming the battery structure 20. The steps for forming the battery structure 20 may include the following steps.

[0059] (1) A plurality of through holes 115 are formed in a substrate 110 made of a thermoplastic resin film, connecting the first surface 111 and the second surface 112 of the substrate 110 by the shortest distance. (2) A first conductive layer 130 is formed on the first surface 111 side of the substrate 110. (3) A second conductive layer 150 is formed on the second surface 112 side of the substrate 110. (4) A first electrode layer 200 is formed so as to be laminated on the first conductive layer 130. (5) An electrolyte layer 400 is formed so as to be laminated on the first electrode layer 200. (6) A second electrode layer 300 is formed so as to be laminated on the electrolyte layer 400 or the second conductive layer 150.

[0060] Figure 10A is a perspective view illustrating the step of forming through holes 115 in a base material 110. Figure 10B is a cross-sectional view illustrating the step of forming through holes 115 in a base material 110. For example, after a thermoplastic resin film formed in a roll is unwound, multiple through holes 115 are formed in the thermoplastic resin film by laser processing using a laser processing device or by die cutting using a die processing machine.

[0061] Figure 11A is a perspective view illustrating the step of forming the first conductive layer 130 and the second conductive layer 150. Figure 11B is a cross-sectional view illustrating the step of forming the first conductive layer 130 and the second conductive layer 150. The first conductive layer 130 and the second conductive layer 150 are formed, for example, by vapor deposition or plating. As described above, in this step, at least one of the first conductive layer 130 and the second conductive layer 150 is formed on the inner wall 116 of each of the plurality of through holes 115.

[0062] If the first conductive layer 130 and the second conductive layer 150 are made of the same metal, the metal is formed on the first surface 111, the second surface 112, and the inner wall 116 of the through hole 115 of the substrate 110. If the first conductive layer 130 and the second conductive layer 150 are made of different metals, for example, the first conductive layer 130 is formed using the first metal, and then the second conductive layer 150 is formed using the second metal. The area in which each conductive layer is formed can be modified in various ways, as described above with reference to Figures 3, 5-8. Also, as described above with reference to Figures 7-8, a step of forming a third conductive layer 170 may be performed between the formation of the first conductive layer 130 and the formation of the second conductive layer 150. The third conductive layer 170 can also be formed, for example, by vapor deposition or plating.

[0063] Figure 12A is a perspective view illustrating the step of forming the first electrode layer 200. Figure 12B is a cross-sectional view illustrating the step of forming the first electrode layer 200. As shown in Figures 12A and 12B, the first electrode layer 200 is formed in contact with the first conductive layer 130. For example, the step of forming the first electrode layer 200 includes the step of applying a slurry mixture of an active material corresponding to the negative electrode, a conductive additive, a solid electrolyte, and a binder onto the first conductive layer 130, and the step of drying. Since a wide range of known materials can be used as the conductive additive and binder slurry, a detailed explanation is omitted.

[0064] Figure 13A is a perspective view illustrating the step of forming the electrolyte layer 400 (more precisely, a solid electrolyte). Figure 13B is a cross-sectional view illustrating the step of forming the electrolyte layer 400. As shown in Figures 13A and 13B, the electrolyte layer 400 is formed in contact with the first electrode layer 200. For example, the step of forming the electrolyte layer 400 includes the steps of applying a solid electrolyte and binder mixture slurry onto the first electrode layer 200 and drying it.

[0065] Figure 14A is a perspective view illustrating the step of forming the second electrode layer 300. Figure 14B is a cross-sectional view illustrating the step of forming the second electrode layer 300. As shown in Figures 14A and 14B, the second electrode layer 300 is formed in contact with the electrolyte layer 400. For example, the step of forming the second electrode layer 300 includes the step of applying a slurry mixture of an active material corresponding to the positive electrode, a conductive additive, a solid electrolyte, and a binder onto the electrolyte layer 400, and the step of drying.

[0066] Although Figures 14A and 14B show an example in which the second electrode layer 300 is formed on the electrolyte layer 400, the battery structure is not limited to this. The battery structure according to this embodiment may be any structure that forms a repeating unit in the stacked structure of the bipolar battery 10, and is not limited to the structure shown in Figures 14A and 14B. For example, the second electrode layer 300 may be formed in contact with the second conductive layer 150 of the current collector 100. For example, the step of forming the second electrode layer 300 may include the step of applying a slurry of an active material, a conductive additive, and a binder corresponding to the positive electrode to the second conductive layer 150, and the step of drying.

[0067] Figure 15A is a perspective view illustrating the step of stacking multiple battery structures 20. Figure 15B is a cross-sectional view illustrating the step of stacking multiple battery structures 20. In the examples in Figures 15A and 15B, an example is shown in which two battery structures 20 are stacked in the stacking direction (z-axis direction), but the number of stacked battery structures 20 may be three or more.

[0068] In this example, a bipolar electrode 30 is formed when the second electrode layer 300, included in the battery structure 20 on the z-negative side, comes into contact with the second conductive layer 150 of the current collector 100 included in the battery structure 20 on the z-positive side. As described above, since the current collector 100 in this embodiment is lightweight, it becomes possible to realize a bipolar battery 10 with high energy density.

[0069] Figure 16 is a cross-sectional view illustrating the steps performed after stacking multiple battery structures 20. As shown in Figure 16, after stacking multiple battery structures 20, the steps of forming extraction electrodes 500a and 500b and sealing the entire structure with a sealing member may be performed. Extraction electrode 500a is an extraction electrode having polarity corresponding to the second electrode layer 300, for example, an extraction electrode for the positive electrode. Extraction electrode 500b is an extraction electrode having polarity corresponding to the first electrode layer 200, for example, an extraction electrode for the negative electrode. Since known materials and structures can be widely applied to the extraction electrodes 500a, 500b and the sealing member 600, a detailed explanation is omitted. The extraction electrode 500a may also serve as a current collector corresponding to the second electrode layer 300, or a current collector not shown in Figure 16 may be provided separately from the extraction electrode 500a.

[0070] Although this embodiment has been described in detail above, it will be readily apparent to those skilled in the art that many modifications are possible without substantially departing from the novel aspects and effects of this embodiment. Therefore, all such modifications are included within the scope of this disclosure. For example, any term that appears at least once in the specification or drawings together with a broader or synonymous term may be replaced with that different term anywhere in the specification or drawings. Furthermore, all combinations of this embodiment and its modifications are also included within the scope of this disclosure. In addition, the configuration and operation of the current collector, bipolar battery, etc., are not limited to those described in this embodiment, and various modifications are possible.

Claims

1. A bipolar battery comprising: a current collector including a substrate formed of a thermoplastic resin film; a first conductive layer formed on a first surface of the substrate; and a second conductive layer formed on a second surface of the substrate opposite to the first surface; a first electrode layer corresponding to one of the positive and negative electrodes and laminated on the first conductive layer; a second electrode layer corresponding to the other of the positive and negative electrodes and laminated on the second conductive layer; and an electrolyte layer provided for a bipolar electrode composed of the current collector, the first electrode layer and the second electrode layer, wherein the current collector has a plurality of through holes formed in the substrate that connect the first surface and the second surface of the substrate by the shortest distance, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes, and the first conductive layer and the second conductive layer are electrically connected.

2. A bipolar battery according to claim 1, wherein the electrolyte layer is a solid electrolyte layer.

3. A bipolar battery according to claim 1 or 2, wherein each of the plurality of through holes has a non-circular shape, in plan view, where the length in a first direction corresponding to the stretching direction of the thermoplastic resin film is longer than the length in a second direction perpendicular to the first direction.

4. A bipolar battery according to claim 1 or 2, wherein the first conductive layer and the second conductive layer are each formed from different metals.

5. A bipolar battery according to claim 1 or 2, wherein the first conductive layer and the second conductive layer are each or both formed from a coating film containing a conductive filler.

6. A bipolar battery according to claim 4, wherein both the first conductive layer and the second conductive layer are formed on the inner wall of each of the plurality of through holes, and the first conductive layer and the second conductive layer are electrically connected by contact at the inner wall.

7. A bipolar battery according to claim 4, wherein only the first conductive layer is formed on the inner wall of each of the plurality of through holes, and the first conductive layer and the second conductive layer are electrically connected by contact between the first conductive layer formed on the inner wall and the second conductive layer formed on the second surface.

8. A bipolar battery according to claim 4, wherein the first conductive layer is formed on the inner wall and second surface of each of the plurality of through holes, and the first conductive layer and the second conductive layer are electrically connected by being laminated in this order on the second surface of the substrate.

9. A bipolar battery according to claim 4, further comprising a third conductive layer formed from a material different from both the first conductive layer and the second conductive layer, wherein the first conductive layer is formed on the inner wall and second surface of each of the plurality of through holes, and the first conductive layer, the third conductive layer, and the second conductive layer are laminated in this order on the substrate on the second surface of the substrate, thereby electrically connecting the first conductive layer and the second conductive layer via the third conductive layer.

10. A bipolar battery according to claim 9, wherein the third conductive layer is formed to cover the first conductive layer on the first surface and on the inner walls of each of the plurality of through holes.

11. A bipolar battery according to claim 1 or 2, wherein the substrate is the thermoplastic resin film in which a conductive filler is compounded.

12. A current collector comprising: a substrate formed of a thermoplastic resin film; a first conductive layer formed on a first surface side of the substrate; and a second conductive layer formed on a second surface side of the substrate that is opposite to the first surface, wherein the substrate has a plurality of through holes formed thereon that connect the first surface and the second surface of the substrate by the shortest distance, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes, the first conductive layer and the second conductive layer are electrically connected, and each of the plurality of through holes has a non-circular shape in plan view, where the length in a first direction corresponding to the stretching direction of the thermoplastic resin film is longer than the length in a second direction perpendicular to the first direction.

13. A current collector comprising: a substrate formed of a thermoplastic resin film; a first conductive layer formed on a first surface side of the substrate; and a second conductive layer formed on a second surface side of the substrate that is opposite to the first surface, wherein the substrate has a plurality of through holes formed thereon that connect the first surface and the second surface of the substrate by the shortest distance, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes, the first conductive layer and the second conductive layer are electrically connected, and the first conductive layer and the second conductive layer are each formed of different metals.

14. Forming a battery structure comprising a current collector, a first electrode layer corresponding to one of the positive and negative electrodes, a second electrode layer corresponding to the other of the positive and negative electrodes, and an electrolyte layer; and stacking a plurality of the battery structures, wherein forming the battery structure comprises: forming a plurality of through holes in a substrate made of a thermoplastic resin film that connect a first surface of the substrate and a second surface which is the surface opposite to the first surface of the substrate by the shortest distance; forming a first conductive layer on the first surface side of the substrate; forming a second conductive layer on the second surface side of the substrate; forming the first electrode layer so as to be stacked on the first conductive layer; forming the electrolyte layer so as to be stacked on the first electrode layer; and forming the second electrode layer so as to be stacked on the electrolyte layer or the second conductive layer, wherein in at least one of the formation of the first conductive layer and the formation of the second conductive layer, at least one of the first conductive layer and the second conductive layer is formed on the inner wall of each of the plurality of through holes. A method for manufacturing bipolar batteries.

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