Bipolar battery manufacturing method and bipolar battery

Abstract

To make it possible to facilitate the sealing of an electrolyte and the discharge of gases generated by an initial charge.SOLUTION: A manufacturing method for a bipolar type battery in which a current collecting foil, a positive electrode, a separator, and a negative electrode are repeatedly stacked on top of each other and sealed together with an electrolyte. During the stacking, an outside and an inside of a cell formed by the opposing current collecting foils sandwiching the positive electrode, the separator, and the negative electrode are communicated. A pair of tubes is also sandwiched. By sucking from one of the pair of tubes, the electrolyte is sucked from the other one into the cell, and the tube is sealed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a bipolar battery and a bipolar battery. [Background technology]

[0002] Conventionally, bipolar batteries have been used, in which current collector foils, positive electrodes, separators, and negative electrodes are repeatedly stacked and sealed together with an electrolyte. Unlike previous batteries (which consist of only one cell made up of a pair of positive and negative electrodes), bipolar batteries have a structure in which multiple cells are stacked and housed side by side in layers. For this reason, the materials, structure, and manufacturing methods of each layer are being studied to prevent short-circuiting between the electrolytes and current collector foils of adjacent cells inside the battery exterior.

[0003] Examples of bipolar battery manufacturing methods include those described below. For example, Patent Document 1 discloses a manufacturing method in which a cell is assembled by providing two openings, one of the openings is closed in a vacuum chamber, and the other opening is immersed in an electrolyte, and the chamber is then returned to atmospheric pressure to inject the electrolyte into the cell. Patent Document 2 discloses a manufacturing method in which a syringe is placed above an injection hole and the electrolyte is supplied from top to bottom. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-073539 [Patent Document 2] Japanese Patent Application Publication No. 2019-096392 Summary of the Invention [Problem to be solved by the invention]

[0005] The manufacturing method disclosed in Patent Document 1 is thought to take a considerable amount of time because the electrolyte is drawn up from one opening by utilizing the pressure difference with atmospheric pressure. Also, bipolar batteries generate gas inside during initial charging, and with this structure, it is thought to be difficult to discharge (vent) the gas.

[0006] Furthermore, with the manufacturing method disclosed in Patent Document 2, it is thought to be difficult to exchange (vent) the electrolyte solution supplied downward from the syringe provided above the injection hole with the air inside the battery exterior. Furthermore, with this structure, it is thought to be difficult to vent gas.

[0007] The present invention has been made in view of the above, and its first object is to provide a bipolar battery manufacturing method and a bipolar battery that allow for easy encapsulation of an electrolyte. Another object of the present invention is to provide a bipolar battery manufacturing method and a bipolar battery that allow for easy release of gas generated during initial charging. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, the present invention provides a method for manufacturing a bipolar battery in which current collector foils, positive electrodes, separators, and negative electrodes are repeatedly stacked and sealed together with an electrolyte, and during the stacking, a pair of tubes are also sandwiched between the current collector foils that face each other across the positive electrode, the separator, and the negative electrode, connecting the outside and inside of the cell formed by the stacking, and suction is applied from one of the pair of tubes to suck the electrolyte into the cell from the other, and the tubes are then sealed.

[0009] This method allows the air inside the cell to be removed and the electrolyte to be easily introduced, eliminating the need for the time-consuming permeation method used in the past to soak a bipolar battery with electrolyte, or the difficult injection method of removing air, making it easier to construct a bipolar battery.

[0010] In addition, in the method for manufacturing a bipolar battery according to the present invention, after the stacking, an initial charge is performed, and prior to sealing the tubes, gas generated in the cells due to the initial charge is released from at least one of the tubes.

[0011] According to this method, gas generated during initial charging can be easily vented.

[0012] In addition, in the manufacturing method of a bipolar battery according to the present invention, the ends of the pair of tubes within the cell are arranged in contact with non-adjacent sides of the separator, and are positioned with the separator sandwiched between them in the thickness direction.

[0013] According to this method, the electrolyte permeates from one side of the separator to the other side in the thickness direction, and also permeates from one side of the separator to the side not adjacent to that side, which makes it easier to wet the separator as a whole than when, for example, one side of the separator has both the end of the suction tube and the end of the electrolyte supply tube, or when these ends are located on adjacent sides or even adjacent to each other.

[0014] In addition, in the manufacturing method of the bipolar battery according to the present invention, the current collector foil and the separator are bonded together at their edges with an adhesive, and the tube is positioned so that one end is located inside the area surrounded by the edges and the other end is located outside the area surrounded by the edges during the stacking, and is bonded together with the separator with the adhesive.

[0015] This method allows the tubes to be properly positioned during stacking.

[0016] Furthermore, the bipolar battery according to the present invention is configured such that current collecting foils, positive electrodes, separators, and negative electrodes are repeatedly stacked, with an electrolyte held between the opposing current collecting foils, and includes a pair of tubular members, one end of which is sandwiched between the edge of a cell formed by the opposing current collecting foils sandwiching the positive electrode, the separator, and the negative electrode, and the other end of which is positioned outside the cell and sealed.

[0017] This configuration realizes a bipolar battery manufacturing method in which suction is applied to one of the pair of tubular members, and the electrolyte is drawn into the cell from the other, and the tubular members are then sealed. This allows for the air in the cell to be removed and the electrolyte to be easily introduced. This eliminates the need for the time-consuming permeation and injection methods, which are difficult to remove air from, that are used in conventional methods to impregnate bipolar batteries with electrolyte, making it easier to construct bipolar batteries. Furthermore, it also makes it easier to vent gases generated during initial charging. [Effects of the Invention]

[0018] The bipolar battery manufacturing method and the bipolar battery according to the present invention have the advantage of easily sealing in the electrolyte. Another advantage of the present invention is that it easily allows gas generated during initial charging to be released. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is an exploded perspective view showing an example of the configuration of a bipolar battery according to a first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the structure of a bipolar battery according to an embodiment. [Figure 3] FIG. 3 is a flowchart showing an example of a method for manufacturing a bipolar battery according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] A method for manufacturing a bipolar battery according to the present invention and an example of a bipolar battery will be described in detail below with reference to the drawings. A bipolar battery 1 is configured by repeatedly stacking current collector foils, positive electrodes, separators, and negative electrodes, with an electrolyte held between opposing current collector foils. Fig. 1 is an exploded perspective view showing an example of the configuration of a bipolar battery 1 according to a first embodiment.

[0021] 1, the bipolar battery 1 of this embodiment includes current collector foils 21, 22, and 23, positive electrode material layers 31 and 32, separators 41 and 42, and negative electrode material layers 51 and 52, as well as an adhesive 60 and tubes 71, 72, 81, and 82. The bipolar battery 1 is configured such that the positive electrode material layer 31, separator 41, and negative electrode material layer 51 are stacked between the current collector foil 21 and the current collector foil 22 and are sealed together with an electrolyte, and further the positive electrode material layer 32, separator 42, and negative electrode material layer 52 are stacked between the current collector foil 22 and the current collector foil 23 and are sealed together with an electrolyte.

[0022] Current collector foil 21 is made of a conductive material suitable for a positive electrode (e.g., aluminum). Current collector foil 23 is made of a conductive material suitable for a negative electrode (e.g., copper). Current collector foil 22 has layers of different polarities on the front and back, and is, for example, an aluminum and copper clad material (laminated material). Alternatively, a conductive material suitable for both positive and negative electrodes may be selected for current collector foil 22.

[0023] The positive electrode material layers 31, 32 are formed by applying a material suitable for a positive electrode (for example, NCA or NMC811) by coating one surface of the current collector foil 21 and one surface (first surface) of the current collector foil 22. The negative electrode material layers 51, 52 are formed by applying a material suitable for a negative electrode (for example, graphite or hard carbon) by coating one surface of the current collector foil 23 and one surface (second surface, which is the reverse side of the first surface) of the current collector foil 22.

[0024] The separators 41, 42 are interposed between the positive electrode material layers 31, 32 and the negative electrode material layers 51, 52 to prevent a short circuit between the positive electrode and the negative electrode. Furthermore, the separators 41, 42 of this embodiment have the properties of being able to deform thinly when pressed and of being able to soak in and absorb liquid. More specifically, the separators 41, 42 of this embodiment are formed from a material that can absorb liquid like a sponge and can be deformed while reducing its volume when pressed, such as a resin nonwoven fabric.

[0025] Furthermore, for the separators 41 and 42, materials that can be bonded by the adhesive 60 are selected for convenience of bonding them together with the adhesive 60.

[0026] The adhesive 60 bonds the current collector foils 21, 22, 23, the separators 41, 42, and the tubes 71, 72, 81, 82. For this reason, an adhesive 60 that can bond these components together is selected.

[0027] Here, one cell (first cell) is formed by the positive electrode material layer 31, separator 41, negative electrode material layer 51, and the opposing current collector foils 21 and 22 sandwiching them therebetween. Another cell (second cell) is formed by the positive electrode material layer 32, separator 42, negative electrode material layer 52, and the opposing current collector foils 22 and 23 sandwiching them therebetween.

[0028] The tubes 71, 72, 81, and 82 are thin tubular members made of resin, and connect the inside and outside of the bipolar battery 1 so that electrolyte and gas can pass between them.

[0029] Here, tubes 71 and 72 are first tubes, which will be described later, and tubes 81 and 82 are second tubes, which will be described later. The first and second tubes form a pair and are provided in the same cell. Furthermore, a pair of tubes is provided in each of the first and second cells. Specifically, tubes 71 and 81 form a pair and are provided in the same cell (first cell), and similarly, tubes 72 and 82 form a pair and are provided in the same cell (second cell).

[0030] Although not shown in Fig. 1, the current collector foils 21-23, positive electrode material layers 31, 32, separators 41, 42, and negative electrode material layers 51, 52 are stacked and sealed in a container. The container is, for example, a flexible bag-like container such as a laminate pouch. The container has a connector (contact point, terminal) for the bipolar battery 1, in which the current collector foils 21, 23 are partially exposed or are provided with tab leads connected to the current collector foils 21, 23.

[0031] Fig. 2 is a schematic cross-sectional view showing an example of the structure of a bipolar battery 1 according to an embodiment. As shown in Fig. 2, the components included in the bipolar battery 1 are stacked in the following order from bottom to top: current collector foil 21, positive electrode material layer 31, separator 41, negative electrode material layer 51, current collector foil 22, positive electrode material layer 32, separator 42, negative electrode material layer 52, and current collector foil 23. The edges of the components are bonded together with adhesive 60. It is further desirable to apply adhesive 60 so as to cover the edges of the current collector foils 21 to 23, as this has the effect of preventing short circuits.

[0032] Furthermore, the tubes 71, 72, 81, and 82 are selected to have a thickness that allows them to fit into the portions between the components that are filled with adhesive 60. In the illustration, the tip of tube 71 is positioned between the separator 41 and the current collector foil 21 and is inserted so as to touch the edge of the positive electrode material layer 31, and the tip of tube 81 is positioned between the separator 41 and the current collector foil 22 and is inserted so as to touch the edge of the negative electrode material layer 51, but this is not a limitation in practice. For example, it is sufficient if the pair of tubes 71 and 81 are sandwiched so as to communicate between a first cell formed by the current collector foil 21 and the current collector foil 22 that face each other across the positive electrode material layer 31, separator 41, and negative electrode material layer 51, and the outside of this first cell.

[0033] Similarly, the tip of tube 72 is positioned between separator 42 and current collector foil 22 and inserted so as to touch the edge of positive electrode material layer 32, and the tip of tube 82 is positioned between separator 42 and current collector foil 23 and inserted so as to touch the edge of negative electrode material layer 52, but this is not a limitation in practice. For example, the pair of tubes 72, 82 may be sandwiched so as to communicate between a second cell formed by current collector foil 22 and current collector foil 23 that face each other across positive electrode material layer 32, separator 42, and negative electrode material layer 52, and the outside of this second cell.

[0034] To summarize the above, the tubes 71, 72, 81, and 82 are arranged so that one end is located inside the edge of each cell that is bonded together with the adhesive 60, and the other end is located outside, and they are bonded together with each layer using the adhesive 60.

[0035] However, the ends of paired tubes (tubes 71 and 81, or tubes 72 and 82) in the same cell are positioned at positions separated from each other within the cell. Positions separated from each other mean, for example, positions contacting non-adjacent sides of the separator, rather than positions contacting the same side or adjacent sides. Furthermore, the ends of paired tubes in the same cell are positioned with the separator in the same cell sandwiched between them in the thickness direction.

[0036] 3 is a flowchart showing an example of a method for manufacturing the bipolar battery 1. This manufacturing method includes a stacking step (steps S1 to S9), an electrolyte injection step (step S11), a sealing step of the first tubes 71 and 72 (step S12), an initial charging step (step S13), a gas discharge step (step S14), a sealing step of the second tubes 81 and 82 (step S15), and an inspection step (step S16).

[0037] First, the current collector foil 21 on which the positive electrode material layer 31 is formed is placed with the positive electrode material layer 31 facing upward (step S1), and adhesive 60 is applied to the periphery of the positive electrode material layer 31 (step S2). Next, the first tube 71 is positioned so that one end is positioned closer to the center of the bipolar battery 1 than the area where the adhesive 60 is applied, and the other end is positioned outside the bipolar battery 1, spanning the area where the adhesive 60 is applied (step S3).

[0038] Next, adhesive 60 is applied to the portion of first tube 71 that is located on adhesive 60 (step S4). As a result, the shape of the contact portion between the next layer to be layered and adhesive 60 forms a continuous ring. Next, separator 41 is layered on top of positive electrode material layer 31 and the adhesive 60 surrounding it (step S5), and adhesive 60 is applied to the edge of separator 41 (step S6).

[0039] Next, the second tube 81 is positioned so that one end is positioned closer to the center of the bipolar battery 1 than the area where the adhesive 60 is applied, and the other end is positioned outside the bipolar battery 1, straddling the area where the adhesive 60 is applied (step S7). Next, additional adhesive 60 is applied onto the portion of the second tube 81 that is positioned on the adhesive 60 (step S8). As a result, similar to step S4, the shape of the contact portion between the next layer to be stacked and the adhesive 60 forms a continuous ring.

[0040] Next, the current collector foil 22 is placed on top of the separator 41 with the negative electrode material layer 51 formed on one surface of the current collector foil 22 facing downward (step S9). Up to this point, the positive electrode material layer 31 and the negative electrode material layer 51, with the separator 41 sandwiched between them, are enclosed between the opposing current collector foils 21, 22.

[0041] In the next step S10, it is determined whether the desired number of cells has been reached. In the example shown in Figures 1 and 2, the desired number of cells is "2." If the desired number of cells has not been reached (No in step S10), the process is repeated from step S2.

[0042] In this embodiment, adhesive 60 is applied to the periphery of the positive electrode material layer 32 formed on the upper surface of the current collecting foil 22 (step S2), and the first tube 72 is positioned so that one end is located closer to the center of the bipolar battery 1 than the area where the adhesive 60 is applied, and the other end is located outside the bipolar battery 1, spanning the area where the adhesive 60 is applied (step S3). Next, adhesive 60 is additionally applied to the portion of the first tube 72 that is located on the adhesive 60 (step S4). Subsequently, the separator 42 is placed on top of the positive electrode material layer 32 and the adhesive 60 surrounding it (step S5), and the adhesive 60 is applied to the edge of the separator 42 (step S6). Next, the second tube 82 is placed on the adhesive 60 (step S7), additional adhesive 60 is applied onto the second tube 82 (step S8), and the current collector foil 23, with the negative electrode material layer 52 formed on one side of the current collector foil 23 facing downward, is placed on top of the separator 42 (step S9).

[0043] Since the desired number of cells has now been reached (Yes in step S10), the stacking process is complete. Next, a vacuum is drawn from the second tubes 81 and 82 to suck the electrolyte from the first tubes 71 and 72 (step S11). This injects the electrolyte into each cell. Next, the first tubes 71 and 72 are disposed of (details will be described later) (step S12).

[0044] Next, the process proceeds to step S13, where initial charging is performed. When the bipolar battery 1 is initially charged, gas is generated and the container swells. Therefore, in the next step S14, the gas accumulated in the container is discharged through the second tubes 81 and 82. At this time, a vacuum may be created, the container may be pressed to return the container to its original state, or the gas may be allowed to be discharged naturally.

[0045] Thereafter, the second tubes 81 and 82 are disposed of (step S15), and the bipolar battery 1 is inspected (step S16), and the manufacturing method is completed.

[0046] The termination of each tube 71, 72, 81, 82 includes, for example, sealing the tube and cutting off unnecessary portions. Sealing can be performed, for example, by welding the tube. Alternatively, the tubes may be sealed by other methods. Sealing the tubes 71, 72, 81, 82 blocks communication between the inside and outside of the bipolar battery 1, preventing the passage of electrolyte and gas.

[0047] As described above, according to this embodiment, a pair of tubes is provided in each cell, and by suctioning with one tube, the other tube can suck the electrolyte into the cell. Therefore, when sealing the electrolyte in the bipolar battery 1, the conventional method of injection, which requires time-consuming permeation and difficult air removal, is no longer necessary. Therefore, according to this embodiment, sealing the electrolyte and discharging the gas generated during initial charging can be easily performed, making it possible to easily construct the bipolar battery 1.

[0048] Furthermore, according to this embodiment, by using the tubes 81, 82 (or the tubes 71, 72) even after the initial charge, it is possible to easily discharge (vent) the gas generated in the bipolar battery 1 due to the initial charge.

[0049] Furthermore, as in this embodiment, when stacking each layer in order, the edges of each layer are glued with adhesive 60, and tubes 71, 72, 81, and 82 are positioned so that one end is inside the adhesive 60 and the other end is outside, and they are sandwiched so as to straddle the adhesive 60, making it easy to position tubes 71, 72, 81, and 82 appropriately.

[0050] In addition, in this embodiment, the tubes 71, 72, 81, and 82 are described as simple pipes, but in practice, they may be equipped with one-way valves (backflow prevention structures) to allow liquid or gas to move in only one direction. In such a configuration, in step S15, the second tubes 81 and 82 may be temporarily secured with clips rather than welded or cut, which can be used to deal with cases where the bipolar battery 1 swells due to deterioration over time.

[0051] Furthermore, in this embodiment, the layers are bonded together using the adhesive 60, but in practice, instead of using the adhesive 60, other methods such as welding may be used for bonding.

[0052] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0053] 1...Bipolar battery, 21~23...Collecting foil, 31,32...Cathode material layer, 41, 42...Separator, 51,52...Negative electrode material layer, 60...adhesive, 71, 72...Tube (first tube), 81,82...Tube (second tube).

Claims

1. A method for manufacturing a bipolar battery in which a current collector foil, a positive electrode, a separator, and a negative electrode are repeatedly stacked and sealed together with an electrolyte, comprising: During the lamination, a pair of tubes are also sandwiched between the positive electrode, the separator, and the negative electrode, which connect the outside and inside of a cell formed by the current collecting foils that face each other with the positive electrode, the separator, and the negative electrode sandwiched therebetween; suctioning one of the pair of tubes to draw the electrolyte into the cell from the other; Seal the tube A method for manufacturing a bipolar battery.

2. After the stacking, an initial charge is performed, Prior to sealing the tube, Gas generated in the cell due to initial charging is discharged from at least one of the tubes. A method for manufacturing the bipolar battery according to claim 1.

3. The ends of the pair of tubes in the cell are arranged in contact with sides of the separator that are not adjacent to each other, and are positioned with the separator sandwiched between them in the thickness direction.

3. A method for producing the bipolar battery according to claim 1 or 2.

4. The current collecting foil and the separator are bonded together at their edges with an adhesive, During the lamination, the tube is arranged so that one end is located inside the area surrounded by the edge portion and the other end is located outside the area surrounded by the edge portion, and the tube is bonded together with the separator by the adhesive. The method for manufacturing the bipolar battery according to claim 2 or 3.

5. A bipolar battery in which a current collecting foil, a positive electrode, a separator, and a negative electrode are repeatedly stacked, and an electrolyte is held between the opposing current collecting foils, a pair of tubular members, one end of which is sandwiched between the edge of a cell formed by the current collecting foils that face each other with the positive electrode, the separator, and the negative electrode interposed therebetween, and the other end of which is positioned outside the cell and sealed; A bipolar battery comprising:

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