Battery cell manufacturing method

Abstract

This prevents insufficient resin welding during the manufacturing of battery cells. [Solution] In the method for manufacturing the battery cell 1, electrode sheets 3 and 4, each having electrodes 32 and 42 located inside a container 10 and current collectors 31 and 41 connected to the electrodes inside the container and protruding outwards from openings 12 and 13 of the container, are stacked in the stacking direction. A resin 51 located between the stacked current collectors is preheated through the current collectors. After the start of preheating, the resin is pressed and heated from the outside in the stacking direction toward the center at the opening of the container, thereby welding the resin between the current collectors and sealing the opening of the container.

Description

Technical Field

[0001] The technology disclosed herein relates to a method for manufacturing a battery cell.

Background Art

[0002] Patent Document 1 describes a conventional laminated battery. A laminated battery is a battery in which an electrode body is housed in an exterior member. The laminated battery includes a plurality of current collecting terminals drawn out from the electrode body to the outside of the exterior member. The plurality of current collecting terminals overlap with a thermoplastic resin interposed therebetween. At the peripheral edge of the exterior member, the resins are welded to each other and welded to the exterior member, whereby the peripheral edge of the exterior member from which the current collecting terminals are drawn out is closed. In a laminated battery, each of the plurality of current collecting terminals is drawn out to the outside of the exterior member. The plurality of current collecting terminals are not connected to each other inside the exterior member. In a laminated battery, the space inside the exterior member can be used for the expansion of the electrode body. The structure of the laminated battery is advantageous for improving the energy density of the battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above-mentioned laminated battery is manufactured by a heat sealing process. In the heat sealing process, the resins overlapping at the peripheral edge of the exterior member are welded to each other by pressing a hot plate, which is an energy source, against the overlapping direction. The laminated battery described in Patent Document 1 has a small number of current collecting terminals drawn out to the outside of the exterior member. The welding of the resin in the heat sealing process is relatively easy.

[0005] As the number of current collection terminals extending to the outside of the exterior component increases, a large number of laminated resins must be welded together. When there are many laminated resins, the resins located towards the center in the lamination direction become farther away from the energy source for welding. In the manufacture of laminate-type batteries with a large number of current collection terminals, the resins located towards the center may not receive sufficient energy, potentially resulting in insufficient welding of the resins in that area.

[0006] The technology disclosed herein suppresses insufficient resin welding during the manufacturing of battery cells. [Means for solving the problem]

[0007] The technology disclosed herein relates to a method for manufacturing battery cells. In this manufacturing method, Electrode sheets, each having an electrode located inside a container and a current collector connected to the electrode inside the container and protruding outward from the opening of the container, are stacked in the stacking direction. The resin located between the stacked current collectors is preheated through the current collectors. After the start of preheating, the resin is pressed and heated at the opening of the container, moving from the outside in the stacking direction towards the center, and then, The resin is welded between the current collectors and the opening of the container.

[0008] In this manufacturing method, the battery cell is produced with multiple stacked current collectors, each protruding out of the container through an opening. The multiple current collectors are connected, for example, to electrodes of the same polarity. The multiple current collectors are not connected to each other inside the container. The connection space between current collectors inside the container can be eliminated. The electrodes of the battery cell can be enlarged using the space inside the container. Battery cells with this structure can have a high energy density.

[0009] The opening of the container is sealed with resin. The resin is, for example, a thermoplastic resin. During the manufacture of the battery cell, at the location of the container opening, the resin between the stacked current collectors is pressurized and heated from the outside in the stacking direction toward the center. For example, a pair of heating plates located on the outside of the container may be used to supply thermal energy to the resin from the outside in the stacking direction toward the center, while sandwiching multiple resins in the stacking direction. The thermal energy is transferred sequentially from the resins on the outside in the stacking direction toward the resins toward the center. The thermal energy supplied to the resins located toward the center in the stacking direction tends to be lower than the thermal energy supplied to the resins located on the outside in the stacking direction due to attenuation.

[0010] In the above manufacturing method, the resin is preheated through a current collector before pressurization and heating of the resin are started. Thermal energy is efficiently supplied to the resin located on the central side in the lamination direction through the current collector located on the central side in the lamination direction.

[0011] The combination of preheating the resin through the current collector and pressurization and heating from the outside in the stacking direction ensures that sufficient thermal energy is supplied to both the resin located on the outside and the resin located in the center of the stacking direction. As a result, all the resin is welded together throughout the entire stacking direction during the manufacturing of the battery cell. This suppresses variations in the sealing strength of the container opening depending on the location.

[0012] Furthermore, if the resin is not preheated through the current collector, pressurization and heating must be continued for a relatively long time before the thermal energy supplied from the outside in the lamination direction reaches the resin on the central side of the lamination direction. If the pressurization and heating time is too long, there is a risk that the resin on the outside in the lamination direction will receive an excessive amount of thermal energy.

[0013] Performing preheating through the current collector first shortens the time from when pressurization and heating from the outside in the stacking direction begin until sufficient thermal energy is supplied to the resin on the central side in the stacking direction. By shortening the pressurization and heating time, sufficient thermal energy is supplied to the resin on the central side in the stacking direction, while excessive thermal energy is prevented from being supplied to the resin on the outside in the stacking direction. The opening of the container is stably sealed. Furthermore, shortening the pressurization and heating time increases the manufacturing efficiency of the battery cells. Note that current collectors generally have high thermal conductivity. After the start of preheating, the resin is rapidly heated through the current collector. The time difference between the start of preheating through the current collector and the start of pressurization and heating from the outside in the stacking direction does not need to be large.

[0014] Furthermore, preheating of the resin through the current collector may be performed on only some of the resins among the multiple resins stacked in the lamination direction. For example, the resin located towards the center in the lamination direction may be preheated through the current collector. This is because the thermal energy supplied to the resin located towards the center in the lamination direction tends to be relatively lower.

[0015] The preheating through the current collector may be continued even after the pressurization and heating of the resin has begun.

[0016] If preheating through the current collector is terminated during the pressurization and heating of the resin, the resin temperature may drop due to heat dissipation through the current collector. By continuing preheating through the current collector even after the pressurization and heating of the resin has started, heat dissipation through the current collector is suppressed. By continuing preheating, all of the resin is welded together, and the opening of the container is stably sealed.

[0017] The preheating through the current collector may be terminated before or at the same time as the heating of the resin is completed.

[0018] If preheating through the current collector continues after the resin heating is complete, the resin temperature may become too high. By ending preheating through the current collector before or at the same time as the resin heating is complete, excessive temperature rise of the resin is suppressed.

[0019] The pressurization of the resin may end simultaneously with or after the completion of the heating of the resin.

[0020] Since the heating of the resin is not continued after the completion of the pressurization of the resin, excessive supply of thermal energy to the resin is suppressed. While the thermal energy is appropriately supplied to the resin, the resin is sufficiently pressurized, so that the opening of the container is appropriately sealed. Incidentally, the pressurization of the resin may be continued after the completion of the heating of the resin. By continuing the pressurization, the resin is stably welded. Continuing the pressurization is advantageous for improving the sealing quality of the opening of the container.

[0021] The preheating through the current collector is performed by the first hot plate. The pressurization and heating of the resin may be performed by a second hot plate different from the first hot plate.

[0022] Using two types of hot plates, the first hot plate and the second hot plate, enables individual setting of the temperature of the first hot plate and the temperature of the second hot plate. Also, it is possible to individually set the start and end of heating by the first hot plate and the start and end of heating by the second hot plate. Each of the plurality of stacked resins is appropriately welded. The sealing quality of the opening of the container is improved.

[0023] The first hot plate may heat the plurality of current collectors in a state where they are overlapped in the stacking direction.

[0024] By using the first hot plate to collectively heat the plurality of current collectors, each of the plurality of stacked resins can be appropriately preheated.

Advantages of the Invention

[0025] In the method for manufacturing a battery cell described above, it is possible to suppress insufficient welding of the resin during the manufacture of the battery cell.

Brief Description of the Drawings

[0026] [Figure 1] FIG. 1 is a cross-sectional view of a battery cell. [Figure 2] Figure 2 shows part of the battery cell manufacturing procedure. [Figure 3] Figure 3 shows part of the battery cell manufacturing procedure. [Figure 4] Figure 4 shows part of the battery cell manufacturing procedure. [Figure 5] Figure 5 shows part of the battery cell manufacturing procedure. [Modes for carrying out the invention]

[0027] The following describes an embodiment of the battery cell manufacturing procedure with reference to the drawings. The battery cell manufacturing procedure described here is illustrative.

[0028] (Battery cell structure) Figure 1 schematically shows the overall structure of battery cell 1. Battery cell 1 is a secondary battery. Battery cell 1 is, for example, a lithium-ion battery.

[0029] The battery cell 1 is a so-called pouch-type battery. The battery cell 1 comprises a power generation element 2 and a container 10. The container 10 is sealed with the power generation element 2 and electrolyte contained within it. The container 10 is made by folding one sheet of laminate material 11 or by overlapping two sheets of laminate material 11 to form a bag. The laminate material 11 has a three-layer structure, for example, a metal layer sandwiched between resin layers on both sides. The metal layer is, for example, aluminum or stainless steel. The resin layer is, for example, polypropylene (PP) or polyethylene (PE).

[0030] The power generation element 2 has a first electrode sheet 3. The first electrode sheet 3 is, for example, a negative electrode sheet. The power generation element 2 also has a second electrode sheet 4. The second electrode sheet 4 is, for example, a positive electrode sheet. The first electrode sheet 3 and the second electrode sheet 4 overlap alternately. The number of first electrode sheets 3 and second electrode sheets 4 in the power generation element 2 is arbitrary. The power generation element 2 is an electrode stack. In the following, the direction in which the first electrode sheet 3 and the second electrode sheet 4 are stacked may be referred to as the stacking direction. The stacking direction is the vertical direction on the plane of the paper in Figure 1 and Figures 2 to 5 described later.

[0031] The first electrode sheet 3 has a current collector 31. The current collector 31 is a thin plate or foil extending in a direction perpendicular to the lamination direction. The end of the current collector 31, that is, the left end in Figure 1, protrudes out of the container 10 through the first opening 12 of the container 10.

[0032] An active material is applied to the first and second surfaces of the current collector 31 located inside the container 10. The first surface is the upper surface of the current collector 31 in Figure 1, and the second surface is the lower surface of the current collector 31 in Figure 1. The active material forms the first electrode 32. The current collector 31 is connected to the first electrode 32 inside the container 10.

[0033] The first electrode sheet 3 has a separator 33. The separator 33 separates the first electrode 32 of the first electrode sheet 3 from the second electrode 42 of the second electrode sheet 4, which will be described later. The separator 33 is, for example, a porous material that allows ionic substances to pass through.

[0034] The separator 33 covers the surface of each of the two first electrodes 32 on the first electrode sheet 3. The separator 33 may be formed by attaching a film to the first electrodes 32. Alternatively, the separator 33 may be formed by drying a slurry applied to the first electrodes 32. The area of ​​the separator 33 may be the same as the area of ​​the first electrode sheet 3, or it may be larger than the area of ​​the first electrode sheet 3.

[0035] The second electrode sheet 4 has a current collector 41. The current collector 41 is a thin plate or foil extending in a direction perpendicular to the lamination direction. The end of the current collector 41, that is, the right end in Figure 1, protrudes out of the container 10 through the second opening 13 of the container 10. The second opening 13 is the opposite opening to the first opening 12 in the direction perpendicular to the lamination direction. Note that the protruding direction of the current collector 41 is not limited to the opposite direction of the protruding direction of the current collector 31.

[0036] An active material is applied to the first and second surfaces of the current collector 41 located inside the container 10. The active material forms a second electrode 42. The current collector 41 is connected to the second electrode 42 inside the container 10.

[0037] As mentioned above, the first electrode sheet 3 and the second electrode sheet 4 are stacked alternately. The first electrode 32 and the second electrode 42 are stacked in the stacking direction inside the container 10 via the separator 33.

[0038] The first opening 12 of the container 10 is sealed with resin 5. Resin 5 is a sealing material. Resin 5 is located between the laminate material 11 and the current collector 31, and between the current collectors 31. Similarly, the second opening 13 is sealed with resin 5. Resin 5 is located between the laminate material 11 and the current collector 41, and between the current collectors 41.

[0039] Multiple current collectors 31 are not connected inside the container 10, but protrude individually outside the container 10. Similarly, multiple current collectors 41 are not connected inside the container 10, but protrude individually outside the container 10. Since the connection space for the current collectors 31 and 41 inside the container 10 can be eliminated, the area of ​​the first electrode 32 and the second electrode 42 can be increased by the amount of space saved. The battery cell 1 can have a high energy density.

[0040] (Method of manufacturing battery cells) Next, the manufacturing method of the battery cell 1 will be described with reference to Figures 2, 3, 4, and 5. The manufacturing method of the battery cell 1 proceeds in the order shown in Figures 2, 3, 4, and 5. Here, the manufacturing method of the battery cell 1 will be explained using the welding of resin at the first opening 12 as an example, but the welding of resin at the second opening 13 is similar.

[0041] First, the first electrode sheet 3 and the second electrode sheet 4 are prepared. As described above, the first electrode sheet 3 has a current collector 31, a first electrode 32, and a separator 33. The first electrode sheet 3 also has a resin 51 (see Figure 2). The resin 51 is located in the current collector 31 between the end of the current collector 31 and the first electrode 32. The resin 51 is pre-welded to the first and second surfaces of the current collector 31, respectively.

[0042] The second electrode sheet 4 comprises a current collector 41, a second electrode 42, and resin. The resin of the second electrode sheet 4, like the resin 51 of the first electrode sheet 3, is located between the end of the current collector 41 and the second electrode 42. The resin is pre-welded to the first and second surfaces of the current collector 41.

[0043] Next, as shown in Figure 2, the first electrode sheet 3 and the second electrode sheet 4 are stacked alternately. As shown in Figure 3, the first electrode 32 and the second electrode 42 overlap via a separator 33. The resin 51 is located between the current collectors 31 of the first electrode sheet 3. The resin 51 is aligned in the stacking direction. In addition, resin is also located between the current collectors 41 of the second electrode sheet 4.

[0044] Resin 51 is a thermoplastic resin. Resin 51 is selected from unoriented polypropylene (CPP), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), biaxially oriented polypropylene (OPP), polyethylene terephthalate (PET), or biaxially oriented nylon (ONY).

[0045] After the first electrode sheet 3 and the second electrode sheet 4 are laminated to form the power generation element 2, the laminate material 11 is placed over the power generation element 2. As shown in Figure 3, the position of the edge of the laminate material 11 (the left edge in Figure 3) corresponds to the position of the resin 51. Also, the laminate material 11 is located outside the outermost current collector 31 in the lamination direction. In other words, the laminate material 11 is located above the uppermost current collector 31 and below the lowermost current collector 31 in the vertical direction in Figure 3.

[0046] Next, preheating of the resin 51 is started. The preheating of the resin 51 is performed using a pair of first heating plates 61, 61. The pair of first heating plates 61, 61 sandwich the multiple current collectors 31 in the stacking direction at the ends of the current collectors 31. The multiple current collectors 31 overlap in the stacking direction. The high-temperature first heating plates 61, 61 heat the multiple current collectors 31 while they are stacked in the stacking direction. As shown by the white arrows in Figure 3, thermal energy is supplied from the pair of first heating plates 61, 61 to the resin 51 through the current collectors 31. Note that in Figure 3, an arrow is drawn only for the current collector 31 in the center of the stacking direction, but thermal energy is supplied through each current collector 31 to each of the resins 51 in contact with the current collectors 31. Each resin 51 is heated up.

[0047] After preheating of the resin 51 begins, as shown in Figure 4, hot plate welding is initiated to the resin 51 aligned in the lamination direction. Hot plate welding is performed using a pair of second hot plates 62, 62. The pair of second hot plates 62, 62 are located on the outside of the laminate material 11 and pressurize the resin 51 aligned in the lamination direction from the outside toward the center (see gray arrows in Figure 4) and heat the resin 51 aligned in the lamination direction. Preheating by the first hot plates 61, 61 continues even after hot plate welding by the second hot plates 62, 62 has begun.

[0048] Thermal energy from the high-temperature second heating plates 62, 62 is transmitted through the laminate material 11, resin 51, and current collector 31 from the outside in the lamination direction towards the center. The resin 51 melts upon receiving the thermal energy.

[0049] Here, as shown by the white arrows in Figure 4, the thermal energy supplied from the second heat plates 62, 62 to the resin 51 located towards the center in the lamination direction tends to be lower due to attenuation than the thermal energy supplied to the resin 51 located towards the outside in the lamination direction. This may result in insufficient welding of the resin 51 located towards the center in the lamination direction.

[0050] In contrast, the resin 51 located towards the center in the stacking direction is preheated through the current collector 31. The resin 51 located towards the center in the stacking direction is heated through the current collector 31, and thermal energy is also supplied to it in the stacking direction from the second heat plate 62. Sufficient thermal energy is supplied to the resin 51 located towards the center in the stacking direction.

[0051] In this way, sufficient thermal energy is supplied to both the resin 51 located on the outside in the lamination direction and the resin 51 located on the central side in the lamination direction. As shown in Figure 5, at the opening of the container 10 (here, the first opening 12), the space between the laminate material 11 and the current collector 31, and the space between the current collectors 31 themselves, is sealed by the welded resin 5.

[0052] Once the welding of the resin 51 is complete, the pressurizing and heating by the second heating plates 62, 62 will end, and the heating by the first heating plates 61, 61 will also end. Note that if the first heating plates 61, 61 separate from the current collectors 31, the current collectors 31 may separate from each other in the stacking direction.

[0053] In the manufacturing method described above, the resin 51 is preheated using the first heat plates 61 before the heat plate welding using the second heat plates 62, 62 is started. Sufficient thermal energy is supplied to both the resin 51 located towards the center in the lamination direction and the resin 51 located towards the outside in the lamination direction.

[0054] Furthermore, preheating the resin 51 through the current collector 31 prior to hot plate welding can shorten the time from when pressurization and heating from the outside in the lamination direction begin until sufficient thermal energy is supplied to the resin 51 on the central side in the lamination direction. This can suppress the supply of excessive thermal energy to the resin 51 on the outside in the lamination direction.

[0055] According to this manufacturing method, variations in the sealing strength of the openings 12 and 13 of the container 10 are suppressed depending on the location. Since all the resin 51 can be stably welded, the sealing quality of the openings 12 and 13 of the container 10 is improved.

[0056] Furthermore, since the thermal conductivity of the current collector 31 is high, the resin 51 is rapidly heated through the current collector 31 after preheating begins. Hot plate welding may be started immediately after preheating through the current collector 31 begins. Starting preheating through the current collector 31 in advance does not increase the manufacturing time, and shortens the hot plate welding time, thus increasing the manufacturing efficiency of battery cells.

[0057] Furthermore, in the manufacturing method described above, preheating by the first heating plates 61, 61 through the current collector 31 continues even after the heating plate welding using the second heating plates 62, 62 has begun. During heating plate welding with the second heating plates 62, 62, heat dissipation through the current collector 31 is suppressed. Since the decrease in the temperature of the resin 51 due to heat dissipation is suppressed, the resin 51 can be welded stably.

[0058] Furthermore, preheating through the current collector 31 by the first heat plates 61, 61 ends when the heat plate welding using the second heat plates 62, 62 is completed. If preheating through the current collector 31 continues after the heat plate welding is completed, there is a risk that the heat energy supplied to the resin 51 will be excessive. By ending the preheating through the current collector 31 when the heat plate welding is completed, the supply of excessive heat energy to the resin 51 is suppressed.

[0059] The preheating by the first heating plates 61, 61 through the current collector 31 may be completed before the heating plate welding using the second heating plates 62, 62 is completed.

[0060] Furthermore, by using two types of heating plates, a first heating plate 61 and a second heating plate 62, it becomes possible to set the temperature of the first heating plate 61 and the temperature of the second heating plate 62 individually. It also becomes possible to set the start and end of heating by the first heating plate 61 and the start and end of heating by the second heating plate 62 individually. In the above manufacturing method, the preheating of the resin 51 using the first heating plate 61 and the hot plate welding of the resin 51 using the second heating plate 62 can be controlled independently of each other. Independent control of preheating and hot plate welding improves the sealing quality of the openings 12 and 13 of the container 10.

[0061] Furthermore, since the first heating plates 61, 61 heat the multiple current collectors 31 stacked in the stacking direction, the multiple current collectors 31 are heated together. This allows each of the stacked resins 51 to be preheated and suppresses heat dissipation from each of the multiple current collectors 31 during heating plate welding, thus enabling proper welding of each of the multiple resins 51.

[0062] (modified version) The first heating plates 61, 61 may selectively heat, for example, the current collectors 31, 41 located towards the center in the stacking direction.

[0063] Furthermore, regarding the termination of the heat plate welding by the second heat plate 62, if the termination of pressurization and the termination of heating by the second heat plate 62 can be set independently, the second heat plate 62 may continue pressurizing even after the heating has ended. By continuing to pressurize, each of the resins 51 can be properly welded, and the sealing quality of the openings 12 and 13 of the container 10 is improved.

[0064] Instead of hot plate welding using the second hot plate 62, the resin 51 may be welded by supplying energy to the resin 51 from the outside in the lamination direction toward the center, for example, by vibration welding, ultrasonic welding, or high-frequency welding. In various welding methods, even if there is attenuation of energy for welding, in the above manufacturing method, by combining this with preheating of the resin through the current collectors 31 and 41, it is possible to sufficiently weld the resin 51 located toward the center in the lamination direction.

[0065] Preheating through current collectors 31 and 41 and hot plate welding may be performed using the same hot plate.

[0066] Preheating through the current collectors 31 and 41 may be terminated at or before the start of hot plate welding. [Explanation of symbols]

[0067] 1 battery cell 10 containers 12. First opening 13. Second opening 3. First electrode sheet 31 Current collector 32 1st electrode 4. Second electrode sheet 41 Current collector 42 2nd electrode 5 resin 51 Resin 61 1st hot plate 62 2nd hot plate

Claims

1. Electrode sheets, each having an electrode located inside a container and a current collector connected to the electrode inside the container and protruding outward from the opening of the container, are stacked in the stacking direction. The resin located between the stacked current collectors is preheated through the current collectors. After the start of preheating, the resin is pressed and heated at the opening of the container, moving from the outside in the stacking direction towards the center, and then, The resin is welded between the current collectors and the current collectors, and the opening of the container is sealed. A method for manufacturing battery cells.

2. In the method for manufacturing a battery cell according to claim 1, The preheating through the current collector continues even after the pressurization and heating of the resin begins. A method for manufacturing battery cells.

3. In the method for manufacturing a battery cell according to claim 2, The preheating through the current collector is terminated before or at the same time as the heating of the resin is completed. A method for manufacturing battery cells.

4. In the method for manufacturing a battery cell according to claim 3, The pressurization of the resin ends at the same time as or after the heating of the resin is completed. A method for manufacturing battery cells.

5. In the method for manufacturing a battery cell according to claim 1, Preheating through the current collector is performed by the first heating plate. The resin is pressurized and heated by a second heating plate, which is separate from the first heating plate. A method for manufacturing battery cells.

6. In the method for manufacturing a battery cell according to claim 5, The first heating plate heats the multiple current collectors stacked in the stacking direction. A method for manufacturing battery cells.

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