Manufacturing method for bipolar batteries

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, at least one of the positive electrode, the separator, and the negative electrode is made to be in a state of including the electrolyte and then sandwiched between the other layers.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bipolar battery. In the law

Background Art

[0002] Conventionally, a bipolar battery in which a current collector foil, a positive electrode, a separator, and a negative electrode are repeatedly laminated and enclosed together with an electrolytic solution has been used. Unlike a conventional battery (which is composed of only one cell constituted by a pair of a positive electrode and a negative electrode), the bipolar battery has a structure in which a plurality of cells are laminated in layers and stored adjacent to each other. Therefore, the material, structure, and manufacturing method of each layer have been studied so that the electrolytic solution and the current collector foil of adjacent cells do not short-circuit inside the battery enclosure.

[0003] As a method for manufacturing a bipolar battery, for example, there is one as described below. For example, the manufacturing method disclosed in Patent Document 1 is to provide two openings, assemble the cells, then close one of the openings in a vacuum chamber, and return the inside of the chamber to atmospheric pressure while the other opening is immersed in the electrolytic solution, thereby injecting the electrolytic solution into the cells. Further, the manufacturing method disclosed in Patent Document 2 is to install a syringe above the injection hole and supply the electrolytic solution from top to bottom.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] ​The manufacturing method disclosed in Patent Document 1 involves drawing up the electrolyte through a single opening using the pressure difference with atmospheric pressure, which is thought to require a considerable amount of time. Furthermore, bipolar batteries generate gas inside during initial charging, and with this structure, it is thought that gas discharge (degassing) would be difficult.

[0006] Furthermore, in the manufacturing method disclosed in Patent Document 2, it is considered difficult to exchange the electrolyte supplied downward by the syringe located above the injection hole with the air inside the battery casing (air removal). Moreover, even in this structure, gas removal is considered difficult.

[0007] The present invention has been made in view of the above, and firstly, a method for manufacturing a bipolar battery that facilitates the sealing of an electrolyte. Law The purpose of this invention is to provide a method for manufacturing a bipolar battery that facilitates the discharge of gas generated during initial charging. Law Another objective is to provide it. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the present invention provides a method for manufacturing a bipolar battery in which a current collector foil, a positive electrode, a separator, and a negative electrode are repeatedly laminated and sealed together with an electrolyte, wherein, during the lamination process, at least one of the positive electrode, the separator, and the negative electrode is made to contain the electrolyte before being sandwiched between other layers.

[0009] This method allows the electrolyte to be included when stacking the components of a bipolar battery. This eliminates the need for time-consuming immersion and difficult air-removal injection processes used in conventional methods to include the electrolyte in a bipolar battery, making it easier to construct a bipolar battery.

[0010] Furthermore, in the method for manufacturing a bipolar battery according to the present invention, the separator has the property of being deformed thin by pressure and the property of impregnating and containing liquid, and during the stacking, a tube is inserted that connects the inside and outside of the cell formed by the current collector foil facing each other with the positive electrode, the separator, and the negative electrode in between, and after the stacking, excess electrolyte is discharged from the tube by pressing in the stacking direction of the positive electrode, the separator, and the negative electrode.

[0011] According to this method, after the separator is stacked with electrolyte in a state similar to a sponge, it becomes thinner when pressed, supplying electrolyte to the other layers (positive and negative electrodes). Furthermore, the excess is discharged outside the bipolar battery, and air is also removed at the same time, making it easy to construct a bipolar battery with sufficient electrolyte.

[0012] Furthermore, the method for manufacturing a bipolar battery according to the present invention involves performing initial charging after stacking, discharging the gas generated inside the cells due to the initial charging from the tube, and sealing the tube.

[0013] This method makes it easy to vent the gas generated during initial charging.

[0014] Furthermore, in the method for manufacturing a 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 arranged such that one end is located on the inside surrounded by the edges and the other end is located on the outside during the lamination process, and is bonded together with the separator with the adhesive.

[0015] This method allows for proper placement of tubes during the lamination process.

[0016] In addition, the bipolar battery according to the present invention is one in which a current collector foil, a positive electrode, a separator, and a negative electrode are repeatedly laminated, and an electrolytic solution is held between the opposing current collector foils. A tubular member is provided, with one end sandwiched at the edge of a cell formed by the opposing current collector foils sandwiching the positive electrode, the separator, and the negative electrode, and the other end located outside the cell and sealed.

[0017] According to this configuration, in the manufacture of a bipolar battery, after the separator is laminated in a state containing an electrolytic solution, for example, like a sponge, it becomes thinner by pressing to supply the electrolytic solution to other layers (positive electrode and negative electrode). Furthermore, the excess is discharged outside the bipolar battery, and at the same time, a method for manufacturing a bipolar battery that performs air bleeding is realized, and a bipolar battery sufficiently containing an electrolytic solution can be easily configured. Also, gas bleeding for discharging gas generated by initial charging can be easily carried out.

Advantages of the Invention

[0018] The manufacturing method of the bipolar battery and the bipolar battery according to the present invention have the effect of enabling easy enclosure of an electrolytic solution. Also, another aspect of the present invention has the effect of enabling easy discharge of gas generated during initial charging.

Brief Description 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 the first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the structure of a bipolar battery according to the embodiment. [Figure 3] FIG. 3 is a flowchart showing an example of the manufacturing method of a bipolar battery according to the embodiment.

Modes for Carrying Out the Invention

[0020] The manufacturing method of the bipolar battery according to the present invention and an example of the bipolar battery will be described in detail below based on the drawings. The bipolar battery 1 is configured by repeatedly laminating current collector foils, a positive electrode, a separator, and a negative electrode, and holding an electrolytic solution between opposing current collector foils. FIG. 1 is an exploded perspective view showing an example of the configuration of the bipolar battery 1 according to the first embodiment.

[0021] As shown in FIG. 1, the bipolar battery 1 of the present embodiment includes current collector foils 21, 22, 23, positive electrode material layers 31, 32, separators 41, 42, and negative electrode material layers 51, 52, an adhesive 60, and tubes 81, 82. In the bipolar battery 1, the positive electrode material layer 31, the separator 41, and the negative electrode material layer 51 are laminated between the current collector foil 21 and the current collector foil 22 and enclosed together with the electrolytic solution. Further, the positive electrode material layer 32, the separator 42, and the negative electrode material layer 52 are laminated between the current collector foil 22 and the current collector foil 23 and enclosed together with the electrolytic solution to form the battery.

[0022] The current collector foil 21 is made of a conductive material (for example, aluminum) suitable for the positive electrode. The current collector foil 23 is made of a conductive material (for example, copper) suitable for the negative electrode. The current collector foil 22 has layers of different polarities provided on the front and back surfaces. For example, it is a clad material (bonding material) of aluminum and copper. Alternatively, a conductive material suitable for both the positive and negative electrodes may be selected as the current collector foil 22.

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

[0024] The separators 41 and 42 are interposed between the positive electrode material layers 31 and 32 and the negative electrode material layers 51 and 52 to prevent short circuits between the positive and negative electrodes. Furthermore, the separators 41 and 42 of this embodiment have the property of being easily deformed into a thin shape by pressure and the property of being able to absorb and contain liquid. More specifically, the separators 41 and 42 of this embodiment are formed from a material that can contain liquid like a sponge and is deformable while reducing its volume by pressure, for example, from a resin nonwoven fabric.

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

[0026] The adhesive 60 adheres the current collector foils 21, 22, and 23, the separators 41 and 42, and the tubes 81 and 82. Therefore, the adhesive 60 is selected to be capable of adhering these components.

[0027] Here, one cell (the first cell) is formed by the positive electrode material layer 31, the separator 41, the negative electrode material layer 51, and the current collector foils 21 and 22 facing each other on either side. Another cell (the second cell) is formed by the positive electrode material layer 32, the separator 42, the negative electrode material layer 52, and the current collector foils 22 and 23 facing each other on either side.

[0028] Tubes 81 and 82 are thin, tubular components made of resin, which connect the inside and outside of the bipolar battery 1 so that electrolyte and gas can move freely between them.

[0029] Although not shown in Figure 1, the current collector foils 21-23, positive electrode material layers 31, 32, separators 41, 42, and negative electrode material layers 51, 52 are sealed in a container in a stacked state. The container is a flexible bag-like material such as a laminate pouch. The container is equipped with tab leads that either partially expose the current collector foils 21, 23 or connect to the current collector foils 21, 23, as connectors (contacts, terminals) for the bipolar battery 1.

[0030] Figure 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 Figure 2, the components of the bipolar battery 1 are stacked from bottom to top in the following order: 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 each component are bonded together with adhesive 60. Furthermore, it is desirable that the adhesive 60 be applied so as to cover the edges of the current collector foils 21 to 23, as this provides an effect of preventing short circuits.

[0031] Furthermore, tubes 81 and 82 are selected to be thick enough to fit into the portions between each component that are filled with adhesive 60. In the illustration, the tip of tube 81 is positioned between the separator 41 and the current collector foil 22 and inserted so as to touch the edge of the negative electrode material layer 51, but this is not the only way in practice. For example, it is sufficient that tube 81 is sandwiched so as to enable communication between the first cell formed by the current collector foils 21 and 22 facing each other with the positive electrode material layer 31, separator 41, and negative electrode material layer 51 in between, and the outside of this first cell.

[0032] Similarly, the tip of the tube 82 is positioned between the separator 42 and the current collector foil 23 and inserted so as to touch the edge of the negative electrode material layer 52, but this is not the only way in which it can be implemented. For example, the tube 82 can be sandwiched so as to enable communication between the second cell formed by the current collector foils 22 and 23 facing each other across the positive electrode material layer 32, the separator 42, and the negative electrode material layer 52, and the outside of this second cell.

[0033] To summarize the above, tubes 81 and 82 should be positioned such that one end is on the inside of the edge of each cell that is bonded with adhesive 60, and the other end is on the outside, and they should be bonded together with each layer by adhesive 60.

[0034] Figure 3 is a flowchart showing an example of a manufacturing method for a bipolar battery 1. This manufacturing method includes a stacking process (steps S1 to S9), an air and excess liquid discharge process (step S10), an initial charging process (step S12), a gas discharge process (step S13), a tube sealing process (step S14) for tubes 81 and 82, and an inspection process (step S15).

[0035] 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 an electrolyte is applied to the positive electrode material layer 31 to wet the electrode material (step S2). The amount of electrolyte applied at this time is such that it does not flow out of the edge of the positive electrode material layer 31 but remains in and on the positive electrode material layer 31.

[0036] Next, adhesive 60 is applied around the positive electrode material layer 31 (step S3). Then, the separator 41, which is wet and contains electrolyte, is placed on top of the positive electrode material layer 31 (step S4), and adhesive 60 is applied to the edges of the separator 41 (step S5).

[0037] Next, the tube 81 is positioned such 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 area where the adhesive 60 is applied (step S6). Next, additional adhesive 60 is applied to the portion of the tube 81 that is on top of the adhesive 60 (step S7). This ensures that the contact area between the next layer to be applied and the adhesive 60 forms a continuous ring shape.

[0038] Next, an electrolyte is applied to the negative electrode material layer 51 formed on one side of the current collector foil 22 to wet the electrode material (step S8), and the current collector foil 22 with the negative electrode material layer 51 facing downwards is placed on top of the separator 41 (step S9). At this point, the positive electrode material layer 31 and the negative electrode material layer 51, with the separator 41 in between, are sealed between the opposing current collector foils 21 and 22, containing the electrolyte. Here, the amount of electrolyte included in the positive electrode material layer 31 in step S2, the amount of electrolyte included in the separator 41 in step S4, and the amount of electrolyte included in the negative electrode material layer 51 in step S8 are adjusted so that their sum is equal to or greater than the appropriate amount of electrolyte to be sealed between the opposing current collector foils 21 and 22.

[0039] Next, air is bled and excess liquid is discharged (step S10). Air bleeding means discharging the air between the current collector foil 21 and the current collector foil 22. Excess liquid is the excess electrolyte that exceeds the appropriate amount of electrolyte. The air and excess liquid are discharged from tube 81.

[0040] This discharge process may be carried out, for example, by pressing the stacked current collector foils 21 to 22 in the overlapping direction, or by creating a vacuum or by discharging the surrounding air to create negative pressure (a negative pressure atmosphere). This appropriately adjusts the amount of electrolyte sealed between the current collector foils 21 and 22. After this, the tube 81 is sealed tightly by temporary fastening. Temporary fastening can be done using a clip-like device or other methods.

[0041] In the following step S11, it is determined whether the desired number of cells has been reached. The desired number of cells is "2" in the examples shown in Figures 1 and 2. If the desired number of cells has not been reached (No. in step S11), the process is repeated from step S2.

[0042] In this embodiment, an electrolyte is applied to the positive electrode material layer 32 formed on the upper surface of the current collector foil 22 to wet the electrode material (step S2), adhesive 60 is applied around the positive electrode material layer 32 (step S3), a separator 42 containing the electrolyte and wet is placed on top of the positive electrode material layer 32 (step S4), and adhesive 60 is applied to the edges of the separator 42 (step S5). Next, the tube 82 is placed on the adhesive 60 (step S6), additional adhesive 60 is applied on top of the tube 82 (step S7), an electrolyte is applied to the negative electrode material layer 52 formed on one side of the current collector foil 23 to wet the electrode material (step S8), and the current collector foil 23 with the negative electrode material layer 52 facing downwards is placed on top of the separator 42 (step S9). Then, air is removed and excess liquid is discharged using the tube 82 (step S10). After this, the tube 82 is temporarily fixed to create a tight seal. For temporary fastening, you can use clip-like devices, or any other method is acceptable.

[0043] Now that the desired number of cells has been reached (Yes in step S11), the stacking process is complete. Next, the process proceeds to step S12, where initial charging is performed. When the bipolar battery 1 is initially charged, gas is generated and the container expands. Therefore, in the next step S13, the temporary fastening of tubes 81 and 82 is released to allow the gas accumulated in the container to be discharged from tubes 81 and 82. At this time, the container may be pressed to reduce the amount that has expanded, or it may be left to be discharged naturally.

[0044] Afterward, tubes 81 and 82 are disposed of (step S14), and the bipolar battery 1 is inspected (step S15), thus completing the manufacturing method. Disposing of tubes 81 and 82 includes, for example, sealing the tubes and cutting off any unnecessary portions. Sealing can be done, for example, by welding the tubes shut. Alternatively, the tubes may be sealed by other methods. Sealing tubes 81 and 82 prevents communication between the inside and outside of the bipolar battery 1, thus preventing the exchange of electrolyte and gas.

[0045] As described above, according to this embodiment, the electrolyte can be included at the time of stacking the parts constituting the bipolar battery 1. Therefore, when sealing the electrolyte into the bipolar battery 1, conventional methods such as time-consuming penetration and difficult air removal during injection are unnecessary. Thus, according to this embodiment, the sealing of the electrolyte and the discharge of gas generated during initial charging can be easily performed, making it possible to easily construct the bipolar battery 1.

[0046] Furthermore, according to this embodiment, after the separators 41 and 42 are stacked while containing electrolyte, they are thinned by pressing, thereby supplying electrolyte from the separators 41 and 42 to the other layers (positive electrode material layers 31 and 32 and negative electrode material layers 51 and 52). In addition, the pressing discharges any excess electrolyte from the bipolar battery 1, and air can be removed at the same time. Therefore, according to this embodiment, a bipolar battery 1 containing sufficient electrolyte can be easily constructed.

[0047] Furthermore, according to this embodiment, by using tubes 81 and 82 even after initial charging, it is possible to easily discharge (degas) the gas generated inside the bipolar battery 1 during initial charging.

[0048] Furthermore, as in this embodiment, when stacking each layer in order, the edges of each layer are bonded with adhesive 60, and the tubes 81 and 82 are positioned so that one end is inside the area surrounded by adhesive 60 and the other end is outside, straddling the adhesive 60 and sandwiched in place. This method makes it easy to position the tubes 81 and 82 appropriately.

[0049] In this embodiment, the separators 41, 42, the positive electrode material layers 31, 32, and the negative electrode material layers 51, 52 were laminated while impregnated with electrolyte. However, this is not the only way to implement this method. For example, it is acceptable for at least some of the separators 41, 42, the positive electrode material layers 31, 32, and the negative electrode material layers 51, 52 to be impregnated with electrolyte before being sandwiched between other layers, as long as they are impregnated with an amount of electrolyte greater than or equal to the required amount.

[0050] Furthermore, in this embodiment, the separators 41 and 42 were described as having the property of deforming like a sponge, becoming thinner and reducing in volume when pressed, and the property of impregnating and containing liquid, but the implementation is not limited to this. For example, if the required amount can be supplied by the electrolyte applied to each layer when stacking the positive electrode material layers 31 and 32 and the negative electrode material layers 51 and 52, the separators 41 and 42 do not have to be conventional thin, sheet-shaped resins that deform thinly when pressed.

[0051] Furthermore, although the tubes 81 and 82 were described as simple pipes in this embodiment, in actual implementation, they may be equipped with one-way valves (backflow prevention structures) so that liquids and gases can only move from the inside to the outside of the bipolar battery 1. In such a configuration, in step S14, the tubes 81 and 82 can be temporarily secured with clips or the like instead of being welded and cut, which can be used to address situations such as when the bipolar battery 1 swells due to deterioration over time.

[0052] Furthermore, although the layers are bonded together using adhesive 60 in this embodiment, other methods such as welding may be used instead of adhesive 60 for bonding.

[0053] 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 implemented in various other forms, and various omissions, substitutions, modifications, and combinations are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0054] 1. Bipolar battery, 21-23...Current collector foil, 31,32...Cathode material layer, 41, 42... Separator, 51,52...Negative electrode material layer, 60... Adhesive, 81, 82... Tubes.

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, The separator has the property of deforming thinly when pressed, and the property of impregnating and containing liquid. During the lamination process, at least one of the positive electrode, the separator, and the negative electrode is made to contain the electrolyte before being sandwiched between other layers. During the lamination process, a tube is inserted to connect the inside and outside of the cell formed by the current collector foils facing each other with the positive electrode, the separator, and the negative electrode in between. After the stacking is complete, excess electrolyte is discharged from the tube by pressing the positive electrode, the separator, and the negative electrode in the stacking direction. A method for manufacturing bipolar batteries.

2. After the aforementioned stacking, initial charging is performed. The gas generated inside the cell during the initial charging is discharged from the tube. The tube is sealed. A method for manufacturing a bipolar battery according to claim 1.

3. The current collector foil and the separator are bonded together at their edges with adhesive. The tube is positioned such that, during lamination, one end is located on the inside surrounded by the edge and the other end is located on the outside, and is bonded together with the separator using the adhesive. A method for manufacturing a bipolar battery according to claim 1 or 2.

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