Battery manufacturing method

Abstract

To provide a battery manufacturing method capable of inhibiting the occurrence of defective deposition when a resin film is deposited on a current collector.SOLUTION: A method of manufacturing a battery having a bipolar-type electrode body includes a deposition step of sealing a periphery of the electrode body with a resin film by depositing an exposed part of a current collector of the electrode body and a resin film with a laser. In the depositing step, a profile length of the laser is increased in proportion to a scan speed of the laser, and the output of the laser is increased in proportion to the profile length.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a battery. [Background technology]

[0002] Various techniques have been proposed for manufacturing batteries, such as those disclosed in Patent Documents 1 to 3. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-142240 A [Patent Document 2] JP 2003-181931 A [Patent Document 3] JP 2023-000059 A Summary of the Invention [Problem to be solved by the invention]

[0004] A method is known in which a battery is manufactured by stacking a bipolar electrode body, the periphery of which is sealed with resin, and a separator to obtain a laminate, and then welding the end faces of the laminate (i.e., the resins around the electrode body). A bipolar electrode body whose periphery is sealed with resin is manufactured by thermally welding a resin film to the exposed part of the current collector of the bipolar electrode body. Here, a method of thermally welding using a laser is known as one of the methods of joining metal and resin film, and when this method is used to manufacture an electrode body, it is necessary to apply the heating energy required for welding in a short time in order to improve manufacturing efficiency. This causes a large linear expansion of the current collector due to heating, which reduces the density between the current collector and the resin film and causes welding failure.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide a battery manufacturing method that can suppress the occurrence of welding defects when welding a resin film to a current collector. [Means for solving the problem]

[0006] That is, the present disclosure includes the following aspects. <1> A method for manufacturing a battery having a bipolar electrode assembly, comprising the steps of: a welding step of welding an exposed portion of a current collector of the electrode body and a resin film by a laser to seal a periphery of the electrode body with the resin film; A battery manufacturing method in which, in the welding process, a profile length of the laser is increased in proportion to a scanning speed of the laser, and an output of the laser is increased in proportion to the profile length. Effect of the Invention

[0007] The battery manufacturing method of the present disclosure can suppress the occurrence of welding defects when welding a resin film to a current collector. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 (1) is a graph showing the results of time and temperature measured by a radiation thermometer for each workpiece before and after the change in scanning speed and output in Comparative Example 1, (2) is an image of the workpiece after the welding process under the conditions before the change in scanning speed and output, and (3) is an image of the workpiece after the welding process under the conditions after the change in scanning speed and output. [Diagram 2] FIG. 2 is a schematic diagram showing an example of the welding process of the present disclosure, (1) is a schematic diagram of the AA cross section of (1), and (3) is a schematic diagram showing the beam width, linear velocity, and output of the laser under each condition shown in Table 1. [Diagram 3]Figure 3 (1) is a graph showing the time and temperature results measured by a radiation thermometer for each workpiece under each of the conditions shown in Table 1, (2) is an image of the workpiece after the welding process under conditions of a beam width of 20 mm, a scanning speed of 100 mm / sec, and an output of 550 W, and (3) is an image of the workpiece after the welding process under conditions of a beam width of 40 mm, a scanning speed of 200 mm / sec, and an output of 1100 W. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, general configurations and manufacturing processes of batteries that do not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field. Furthermore, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships.

[0010] The present disclosure provides a method for manufacturing a battery having a bipolar electrode assembly, comprising: a welding step of welding an exposed portion of a current collector of the electrode body and a resin film by a laser to seal a periphery of the electrode body with the resin film; The present invention provides a battery manufacturing method in which, in the welding step, a profile length of the laser is increased in proportion to a scanning speed of the laser, and an output of the laser is increased in proportion to the profile length.

[0011] When using thermal welding with a laser to weld a current collector and a resin film as a method of sealing the outer periphery of a bipolar battery to prevent electrolyte from seeping in, in order to uniformly thermally weld the long area of ​​the outer periphery of the electrode body that needs to be welded with a laser, a good welding state can be obtained for the entire outer periphery of the electrode body by moving, for example, a rectangular laser irradiation range with uniform power density along the outer periphery of the electrode body that needs to be welded. In this case, the processing time required to weld one electrode body is determined by the speed at which the rectangular laser irradiation range shape (hereinafter referred to as the laser profile) is moved along the length of the outer periphery of the electrode body that needs to be welded. Heat welding generally requires a certain temperature and energy to achieve a welded state, but in order to reduce manufacturing costs, it is necessary to improve the processing capacity of the equipment, which makes it necessary to increase the processing speed. When the energy required for heat welding is determined, the processing conditions require that the heating energy required for welding be applied in a short period of time. As a result, an increase in irradiation energy per unit time is required, which increases the linear expansion of the current collector due to heating, reducing the degree of adhesion between the current collector and the resin film and causing welding defects.

[0012] In the present disclosure, when a current collector and a laser-transparent resin film are thermally welded by scanning a rectangular laser profile at the interface between the current collector and the resin film with a laser, the conditions of the laser device are set as follows when the processing speed (laser scanning speed) is increased for the purpose of improving productivity. (1) In order to maintain the time it takes to pass a fixed point, the laser profile length (beam width) is increased in proportion to the increase in the laser scanning speed. (2) Increase the laser output in proportion to the profile length so that the energy density within the irradiation profile does not change. By using the above method, the maximum temperature and holding time can be kept constant even when the scanning speed during processing is changed. For example, 2For a unit area, the energy density of the irradiated laser profile and the processing time during which the laser irradiation continues are constant regardless of the scanning speed. As a result, it is possible to obtain good welding quality at any scanning speed. It is also possible to increase the processing speed while maintaining a good welding state, thereby improving production efficiency.

[0013] The manufacturing method of the present disclosure includes a welding process. The welding step is a step of welding the exposed portion of the current collector of the electrode body and a resin film by a laser, thereby sealing the periphery of the electrode body with the resin film. One method for welding a resin film to a current collector is a laser welding method (laser welding method). The laser welding method focuses on the high laser transparency of the resin film to be welded, and uses a laser beam to pass through the pressurized part and resin film, and the current collector absorbs and heats the interface that requires direct bonding, thereby improving processing energy efficiency and preventing the resin film from sticking to the pressurized part, since the temperature of the pressurized part does not easily increase. In addition, by making the current collector a thin foil, for example 100 μm or less, the resin film on both sides of the current collector can be welded with a single laser irradiation.

[0014] In the welding process, the laser profile length is increased in proportion to the laser scanning speed, and the laser output is increased in proportion to the profile length. As long as the conditions are satisfied, the laser scanning speed, profile length, output, and energy density may be in the following ranges. The profile length (beam width) of the laser may be from 20 to 80 mm. The laser power may be 500-1100W. Energy density: 0.5 to 2.0 W / mm 2 may be also possible. The scanning speed (linear speed) of the laser may be 100 to 200 mm / sec.

[0015] Examples of metals that can be used as the current collector include aluminum, copper, SUS, and nickel. The current collector may be in the form of a foil or the like. The thickness of the current collector is, for example, not less than 0.1 μm and not more than 100 μm.

[0016] The resin films may be disposed so as to sandwich the exposed portion of the current collector. The exposed portion of the current collector is sandwiched between a pair of resin films, that is, a first resin film and a second resin film. The resin film may be a material that is laser-transparent and allows the laser to pass therethrough. Examples of the resin film include various resin materials such as polyethylene, polypropylene, polystyrene, ABS resin, modified polypropylene, and acrylonitrile-styrene resin. The thickness of the resin film is, for example, not less than 10 μm and not more than 200 μm.

[0017] The resin film may be disposed so as to be sandwiched between pressure members. A workpiece including a current collector and a resin film sandwiching an exposed portion of the current collector may be clamped between a pair of pressure members, i.e., a first pressure member and a second pressure member, and pressed by the first pressure member and the second pressure member. Examples of the pressure member include aluminum, which is a material with low laser absorption rate, and glass, which is a material that is hard, heat resistant, and highly laser transmissive. The first pressure member and the second pressure member may be made of the same material or different materials. The pressure member placed on the laser irradiation side may be made of glass, etc.

[0018] After the welding step, the electrode assembly and a separator may be laminated to obtain a laminate. The end faces of the laminate may be welded to a resin film that surrounds the electrode assembly.

[0019] The battery obtained by the manufacturing method of the present disclosure includes a bipolar electrode body formed by welding a resin film to an exposed portion of a current collector. A bipolar electrode body has a positive electrode layer on one surface of an inner region in the surface direction of the current collector, other than the region where a resin film is welded to an exposed portion of the current collector, and a negative electrode layer on the other surface. The current collector may be composed of one type of metal, or may be a laminated foil in which two types of metal foils are laminated together, and one of the two types of metal foils may be a positive electrode current collector and the other may be a negative electrode current collector. The battery of the present disclosure may include an anode current collector, an anode layer, an electrolyte layer, a cathode layer, and a cathode current collector. The battery of the present disclosure may have a plurality of bipolar electrode bodies stacked in a stacking direction. The number of layers of the electrode body is not particularly limited, and may be from 2 to several hundred.

[0020] The type of the battery of the present disclosure is not particularly limited, and examples thereof include nickel-metal hydride secondary batteries and lithium-ion secondary batteries. The battery may be a liquid battery using an electrolytic solution as an electrolyte, or a solid battery using a solid electrolyte as an electrolyte. The battery may be a primary battery or a secondary battery. Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline automobiles, and diesel automobiles. In particular, the battery may be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for moving objects other than vehicles (for example, railways, ships, and aircraft), and may also be used as a power source for electrical products such as information processing devices. EXAMPLES

[0021] Comparative Example 1 When the laser scanning speed was increased from 100mm / sec to 200mm / sec, the laser output was increased from 500W to 1000W, but the laser profile length (beam width) in the scanning direction was kept at 20mm (beam shape 23×20mm). The workpiece was irradiated with the laser under the conditions before and after the change in scanning speed and output, the temperature was measured with a radiation thermometer, and the occurrence of welding defects was visually confirmed. The results are shown in Figure 1. FIG. 1 (1) is a graph showing the results of time and temperature measured by a radiation thermometer for each workpiece before and after the change in scanning speed and output in Comparative Example 1, (2) is an image of the workpiece after the welding process under the conditions before the change in scanning speed and output, and (3) is an image of the workpiece after the welding process under the conditions after the change in scanning speed and output. As shown in FIG. 1(1), in Comparative Example 1, when the scanning speed was changed, the passing time of the fixed point changed, and the energy density in the laser profile changed. As shown in FIG. 1(2), no welding defects occurred under the conditions before the scanning speed was increased, but as shown in FIG. 1(3), welding defects occurred under the conditions after the scanning speed was increased.

[0022] Example 1 As shown in Table 1, the laser was irradiated onto the workpiece under each condition in which the laser profile length in the scanning direction was increased in proportion to the increase in scanning speed so that the time to pass through the fixed point would not change, and the laser output was increased in proportion to the laser profile length so that the energy density within the laser profile would not change. The temperature was measured with a radiation thermometer, and the occurrence of welding defects was visually confirmed. FIG. 2 is a schematic diagram showing an example of the welding process of the present disclosure, (1) is a schematic diagram of the AA cross section of (1), and (3) is a schematic diagram showing the beam width, linear velocity, and output of the laser under each condition shown in Table 1.

[0023] [Table 1]

[0024] The laser was actually irradiated onto the workpiece under each of the conditions shown in Table 1, the temperature was measured with a radiation thermometer, and the occurrence of welding defects was visually confirmed. The results are shown in Figure 3. Figure 3 (1) is a graph showing the time and temperature results measured by a radiation thermometer for each workpiece under each of the conditions shown in Table 1, (2) is an image of the workpiece after the welding process under conditions of a beam width of 20 mm, a scanning speed of 100 mm / sec, and an output of 550 W, and (3) is an image of the workpiece after the welding process under conditions of a beam width of 40 mm, a scanning speed of 200 mm / sec, and an output of 1100 W. As shown in FIG. 3(1), in Example 1, the same heating state and temperature state can be maintained even if the scanning speed is changed, and as shown in FIGS. 3(2) to (3), it can be seen that no welding defects occur even if the scanning speed is changed. These results demonstrate that even if the laser scanning speed is changed, the same quality can be maintained as before the change by changing the beam width and output accordingly.

Claims

[Claim 1] A method for manufacturing a battery having a bipolar electrode assembly, comprising the steps of: a welding step of welding an exposed portion of a current collector of the electrode body and a resin film by a laser to seal a periphery of the electrode body with the resin film; A battery manufacturing method in which, in the welding process, a profile length of the laser is increased in proportion to a scanning speed of the laser, and an output of the laser is increased in proportion to the profile length.

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