JP7828804B2 - Method for manufacturing a bipolar battery and a bipolar battery - Google Patents

Description

This invention relates to a method for manufacturing a bipolar battery and to a bipolar battery.

Conventionally, bipolar batteries have been used, in which current collector foil, positive electrode, separator, and negative electrode are repeatedly layered and sealed together with electrolyte. Unlike earlier batteries (which consisted 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 adjacent to each other. Therefore, the materials, structure, and manufacturing methods of each layer are carefully considered to prevent short circuits between the electrolyte and current collector foil of adjacent cells within the battery casing.

There are several methods for manufacturing bipolar batteries, as described below. For example, the manufacturing method disclosed in Patent Document 1 involves assembling a cell with two openings, then closing one of the openings in a vacuum chamber while immersing the other in an electrolyte solution. The chamber is then returned to atmospheric pressure to inject the electrolyte solution into the cell. Another manufacturing method disclosed in Patent Document 2 involves placing a syringe above the injection port and supplying the electrolyte solution from top to bottom.

Japanese Patent Publication No. 2018-073539 Japanese Patent Publication No. 2019-096392

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 internally during initial charging, and with this structure, gas removal (degassing) is considered difficult.

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

This invention has been made in view of the above, and firstly, aims to provide a method for manufacturing a bipolar battery and a bipolar battery that facilitates the sealing of the electrolyte. Furthermore, another objective of this invention is to provide a method for manufacturing a bipolar battery and a bipolar battery that facilitates the discharge of gas generated during initial charging.

To solve the above-mentioned problems and achieve the objective, the present invention provides a method for manufacturing a bipolar battery in which current collector foil, a positive electrode, a separator, and a negative electrode are repeatedly laminated and sealed together with an electrolyte. During the lamination process, a pair of tubes are inserted to connect the outside and inside of the cell formed by the current collector foils facing each other, sandwiching the positive electrode, the separator, and the negative electrode. The electrolyte is drawn into the cell from one of the tubes by suction from the other, and the tubes are then sealed.

This method allows for easy removal of air from the cell and readily incorporates the electrolyte. Therefore, it eliminates the need for the time-consuming immersion process and the difficult air-removal during injection required in conventional methods for impregnating bipolar batteries, making it easier to construct bipolar batteries.

Furthermore, the manufacturing method of the bipolar battery according to the present invention involves performing initial charging after the stacking, and, prior to sealing the tubes, discharging the gas generated in the cells due to the initial charging from at least one of the tubes.

This method allows for easy venting of gases generated during initial charging.

Furthermore, in the method for manufacturing a bipolar battery according to the present invention, the ends of the pair of tubes within the cell are arranged so that they are in contact with each other's non-adjacent sides of the separator, and the separator is sandwiched between them in the thickness direction.

According to this method, the electrolyte permeates from one side of the space sandwiching the separator in the thickness direction to the other, and also permeates from one side of the separator towards the non-adjacent side. Therefore, compared to cases where, for example, both the end of the suction tube and the end of the electrolyte supply tube are on one side of the separator, or where these ends are located on adjacent sides or even adjacent to each other, it is easier to keep the separator moist overall.

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 positioned such that one end is located inside the area surrounded by the edges and the other end is located outside during the lamination process, and is bonded together with the separator using the adhesive.

This method allows for proper placement of the tubes during lamination.

Furthermore, the bipolar battery according to the present invention comprises a pair of tubular members, one end of which is sandwiched between opposing current collector foils, and the other end of which is positioned outside the cell, with the battery having a tubular structure. The battery is constructed by repeatedly stacking current collector foils, a positive electrode, a separator, and a negative electrode, and holding an electrolyte between opposing current collector foils.

This configuration enables a bipolar battery manufacturing method in which the electrolyte is drawn into the cell from one of a pair of tubular components by suction from the other, and the tubular components are sealed. This allows for easy intake of the electrolyte while removing air from the cell. As a result, the conventional time-consuming permeation process and the difficult air-removal process of injection are eliminated when filling the bipolar battery with electrolyte, making it easier to construct a bipolar battery. Furthermore, venting gases generated during initial charging can be easily performed.

The method for manufacturing a bipolar battery and the bipolar battery itself according to the present invention have the effect of facilitating the sealing of the electrolyte. Furthermore, the present invention also has the effect of facilitating the discharge of gases generated during initial charging.

Figure 1 is an exploded perspective view showing an example of the configuration of a bipolar battery according to the first embodiment. Figure 2 is a schematic cross-sectional view showing an example of the structure of a bipolar battery according to an embodiment. Figure 3 is a flowchart showing an example of a method for manufacturing a bipolar battery according to an embodiment.

The manufacturing method of 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. The bipolar battery 1 is constructed by repeatedly stacking current collector foils, a positive electrode, a separator, and a negative electrode, with an electrolyte held between opposing current collector foils. Figure 1 is an exploded perspective view showing an example of the configuration of a bipolar battery 1 according to the first embodiment.

As shown in Figure 1, the bipolar battery 1 of this embodiment comprises 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 71, 72, 81, 82. The bipolar battery 1 is constructed by laminating the positive electrode material layer 31, separator 41, and negative electrode material layer 51 between current collector foils 21 and 22 and sealing them together with the electrolyte. Furthermore, the positive electrode material layer 32, separator 42, and negative electrode material layer 52 are laminated between current collector foils 22 and 23 and sealed together with the electrolyte.

The current collector foil 21 is made of a conductive material suitable for the positive electrode (e.g., aluminum). The current collector foil 23 is made of a conductive material suitable for the negative electrode (e.g., copper). The current collector foil 22 has layers for different electrodes on its front and back sides, and is, for example, a clad material (bonded material) of aluminum and copper. Alternatively, a conductive material suitable for both the positive and negative electrodes may be selected for the current collector foil 22.

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

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 deforming thinly upon pressure and the property of impregnating and containing 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 upon pressure, for example, from a resin nonwoven fabric.

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

The adhesive 60 adheres the current collector foils 21, 22, and 23, the separators 41 and 42, and the tubes 71, 72, 81, and 82. Therefore, an adhesive capable of bonding these components is selected for the adhesive 60.

Here, the positive electrode material layer 31, separator 41, negative electrode material layer 51, and the opposing current collector foils 21 and 22 sandwiching them form one cell (the first cell). Furthermore, the positive electrode material layer 32, separator 42, negative electrode material layer 52, and the opposing current collector foils 22 and 23 sandwiching them form another cell (the second cell).

Tubes 71, 72, 81, and 82 are thin, tubular components made of resin, which connect the inside and outside of the bipolar battery 1, allowing electrolyte and gas to pass through.

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

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, for example, 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, serving as connectors (contacts, terminals) for the bipolar battery 1.

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. Furthermore, the edges of each component are bonded together with adhesive 60. It is desirable that the adhesive 60 be applied so as to cover the edges of the current collector foils 21-23, as this provides an effect of preventing short circuits.

Furthermore, tubes 71, 72, 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 71 is positioned between the separator 41 and the current collector foil 21, 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, inserted so as to touch the edge of the negative electrode material layer 51. However, the implementation is not limited to this. For example, it is sufficient that a pair of tubes 71 and 81 are sandwiched between the positive electrode material layer 31, the separator 41, and the current collector foil 22 facing each other across the negative electrode material layer 51, allowing communication between the first cell and the outside of this first cell.

Similarly, the tip of tube 72 is positioned between the separator 42 and the current collector foil 22, and is inserted so as to touch the edge of the positive electrode material layer 32. The tip of tube 82 is positioned between the separator 42 and the current collector foil 23, and is inserted so as to touch the edge of the negative electrode material layer 52. However, the implementation is not limited to this configuration. For example, it is sufficient that a pair of tubes 72 and 82 are sandwiched between the current collector foils 22 and 23, which are facing each other with the positive electrode material layer 32, separator 42, and negative electrode material layer 52 in between, so that they can communicate with the outside of this second cell.

To summarize the above, tubes 71, 72, 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.

However, the ends of tubes forming a pair within the same cell (tube 71 and tube 81, or tube 72 and tube 82) are positioned at separate locations within the cell. These separate locations mean, for example, that they are not at locations touching the same or adjacent edges of the separator, but rather at locations touching non-adjacent edges. Furthermore, the ends of tubes forming a pair within the same cell are positioned with a separator from the same cell sandwiched between them in the thickness direction.

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

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 upwards (step S1), and adhesive 60 is applied around the positive electrode material layer 31 (step S2). Next, the first tube 71 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 straddles the area where the adhesive 60 is applied and is located outside the bipolar battery 1 (step S3).

Next, additional adhesive 60 is applied to the portion of the first tube 71 that is located on the adhesive 60 (step S4). This ensures that the contact area between the next layer to be applied and the adhesive 60 forms a continuous, annular shape. Subsequently, the separator 41 is placed on top of the positive electrode material layer 31 and the surrounding adhesive 60 (step S5), and adhesive 60 is applied to the edges of the separator 41 (step S6).

Next, the second tube 81 is positioned such that one end is located closer to the center of the bipolar battery 1 than the application area of the adhesive 60, and the other end straddles the application area of the adhesive 60 and is located outside the bipolar battery 1 (step S7). Next, additional adhesive 60 is applied to the portion of the second tube 81 that is located on the adhesive 60 (step S8). This results in a continuous, annular shape at the contact point between the next layer to be applied and the adhesive 60, similar to step S4.

Next, the current collector foil 22, with the negative electrode material layer 51 formed on one side 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.

In the following step S10, 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 S10), the process is repeated from step S2.

In this embodiment, adhesive 60 is applied around the positive electrode material layer 32 formed on the upper surface of the current collector foil 22 (step S2). The first tube 72 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 straddles the area where the adhesive 60 is applied and is located outside the bipolar battery 1 (step S3). Next, additional adhesive 60 is applied to the portion of the first tube 72 that is 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 adhesive 60 is applied to the edges of the separator 42 (step S6). Next, the second tube 82 is placed on top of the adhesive 60 (step S7), additional adhesive 60 is applied on top of 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 downwards, is placed on top of the separator 42 (step S9).

Now that the desired number of cells has been reached (Yes in step S10), the lamination process is complete. Next, the electrolyte is drawn from the first tubes 71 and 72 by evacuating the second tubes 81 and 82 (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).

Next, the process proceeds to step S13, where initial charging is performed. When the bipolar battery 1 is initially charged, gas is generated, causing the container to swell. Therefore, in the next step S14, the gas accumulated in the container is discharged through the second tubes 81 and 82. At this stage, vacuuming may be performed, the container may be compressed to reduce its swelled state, or it may be allowed to swell naturally.

Subsequently, the second tubes 81 and 82 are disposed of (step S15), and the bipolar battery 1 is inspected (step S16), thus completing this manufacturing method.

Furthermore, the handling of each tube 71, 72, 81, and 82 includes, for example, sealing the tubes and cutting off any unnecessary portions. Sealing can be achieved, for example, by welding the tubes shut. Alternatively, the tubes may be sealed by other methods. Sealing of tubes 71, 72, 81, and 82 prevents communication between the inside and outside of the bipolar battery 1, thus preventing the exchange of electrolyte and gas.

As described above, according to this embodiment, since a pair of tubes is provided in each cell, the electrolyte can be drawn into the cell by suction using one tube, with the other tube handling the draw-in. Therefore, when filling the bipolar battery 1 with electrolyte, the conventional method of time-consuming permeation and difficult air removal is eliminated. Thus, according to this embodiment, the filling of electrolyte and the discharge of gases generated during initial charging can be easily performed, making it possible to easily construct the bipolar battery 1.

Furthermore, according to this embodiment, even after initial charging, the gas generated inside the bipolar battery 1 during initial charging can be easily discharged (degassed) by using tubes 81 and 82 (or tubes 71 and 72).

Furthermore, as in this embodiment, when stacking each layer sequentially, the edges of each layer are bonded with adhesive 60, and the tubes 71, 72, 81, and 82 are positioned so that one end is inside the adhesive 60 and the other end is outside, straddling the adhesive 60 and sandwiched in place. This method allows for easy and appropriate placement of the tubes 71, 72, 81, and 82.

Furthermore, although tubes 71, 72, 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) to allow liquids or gases to move in only one direction. In such a configuration, in step S15, instead of welding and cutting the second tubes 81 and 82, they can be temporarily secured with clips or similar methods, which can be used to address situations such as when the bipolar battery 1 swells due to deterioration over time.

Furthermore, in this embodiment, the layers are bonded together using adhesive 60, but in implementation, other methods such as welding may be used instead of adhesive 60.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples only 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 within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as described in the claims.

1. Bipolar battery,
21-23... Current collector foil,
31, 32... cathode material layer,
41, 42... Separator,
51, 52... negative electrode material layer,
60... Adhesive,
71, 72... Tubes (First Tube),
81, 82... tubes (second tubes).

Claims (5)

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,
During the lamination process, a pair of tubes are also inserted to connect the outer and inner sides of the cell formed by the current collector foils facing each other with the positive electrode, the separator, and the negative electrode in between.
By drawing suction from one of the pair of tubes, the electrolyte is drawn into the cell from the other tube.
A method for manufacturing a bipolar battery, which involves sealing the aforementioned tube. After the aforementioned stacking, initial charging is performed.
Prior to sealing the tube,
A method for manufacturing a bipolar battery according to claim 1, wherein the gas generated in the cell by initial charging is discharged from at least one of the tubes. A method for manufacturing a bipolar battery according to claim 1 or 2, wherein the ends of the pair of tubes within the cell are arranged in contact with each other on non-adjacent sides of the separator, and the separator is positioned between them in the thickness direction. The current collector foil and the separator are bonded together at their edges with adhesive.
The method for manufacturing a bipolar battery according to claim 2 or 3, wherein the tube is arranged such that, during the lamination process, 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 bipolar battery in which current collector foils, a positive electrode, a separator, and a negative electrode are repeatedly stacked, and an electrolyte is held between opposing current collector foils,
A bipolar battery comprising a pair of tubular members, one end of which is sandwiched into the edge of a cell formed by the current collector foils facing each other across the positive electrode, the separator, and the negative electrode, and the other end of which is positioned outside the cell and sealed.