Secondary battery manufacturing method

Abstract

To provide a method for producing a secondary battery, capable of suppressing generation of an un-welded portion during the welding of a resin member to a current collector.SOLUTION: There is provided a method for producing a secondary battery, the secondary battery including a resin member welded to a peripheral portion of a current collector. The method includes a welding step of welding the resin member to the current collector, in a state where the resin member is arranged to sandwich the peripheral portion of the current collector, the resin member is arranged to be sandwiched by a pressurizing member, and the current collector and the resin member are pressurized by the pressurizing member. In the welding step, an elastic member is arranged between the resin member and the pressurizing member.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Various techniques have been proposed for manufacturing a secondary battery such as that disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-000059 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional technology, the sealing material (resin member) that seals the periphery of the current collector is welded using non-contact heating. When the resin member is welded to the current collector, linear expansion causes the current collector to undulate, which can impair the adhesion between the resin member and the current collector and result in unwelded areas.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and its main object is to provide a method for manufacturing a secondary battery that can suppress the occurrence of unwelded portions when welding a resin member 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 secondary battery by welding a resin member to a peripheral portion of a current collector, the resin members are arranged to sandwich the peripheral edge portion of the current collector, and The resin member is disposed so as to be sandwiched between pressure members, and a welding step of welding the resin member to the current collector while the current collector and the resin member are pressed by the pressing member, In the welding step, an elastic member is disposed between the resin member and the pressure member on at least one side of the current collector. Since the resin member is in contact with the elastic member, the resin member and the current collector can be brought into close contact with each other regardless of wrinkles in the current collector, and the occurrence of unwelded portions can be suppressed.

[0007] <2> In the welding step, the resin member is welded to the current collector by a laser, the resin member transmits the laser; the laser is irradiated onto the current collector from above in the vertical direction of the current collector, the resin member is disposed in contact with the elastic member located vertically below the current collector; <1> 10. A method for producing the secondary battery according to claim 9. By positioning the elastic member in contact only vertically below the current collector, it is possible to prevent wrinkles from forming on the current collector due to deformation of the elastic member caused by gravity, while also allowing the resin member and the current collector to be adhered together regardless of wrinkles on the current collector, thereby preventing the occurrence of unwelded areas. [Effects of the Invention]

[0008] The method for manufacturing a secondary battery according to the present disclosure can suppress the occurrence of unwelded portions when welding the resin member to the current collector. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the welding step at the peripheral edge of the current collector of Comparative Example 1. As shown in FIG. [Figure 2] In FIG. 2, (1) is an image of the workpiece during the welding process of Comparative Example 1, and (2) is an image of the workpiece after the welding process of Comparative Example 1. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the welding step at the peripheral edge of the current collector of Example 1. As shown in FIG. [Figure 4]In FIG. 4, (1) is an image of the workpiece during the welding process of Example 1, and (2) is an image of the workpiece after the welding process of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of a secondary battery that do not characterize the present disclosure) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. Furthermore, the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect the actual dimensional relationships.

[0011] The present disclosure provides a method for manufacturing a secondary battery by welding a resin member to a peripheral portion of a current collector, the resin members are arranged to sandwich the peripheral edge portion of the current collector, and The resin member is disposed so as to be sandwiched between pressure members, and a welding step of welding the resin member to the current collector while the current collector and the resin member are pressed by the pressing member, In the welding step, an elastic member is disposed between the resin member and the pressure member on at least one side of the current collector.

[0012] When laser welding of the current collector and resin member is used as a method of peripheral resin sealing to prevent the intrusion of electrolyte in bipolar batteries, from the perspective of battery structural design, the current collector needs to be as thin as possible to improve energy density per volume and weight. On the other hand, when a resin member is heat-welded to the outer periphery, partial heating is required at the overlapping portion of the current collector and the resin member. When the outer periphery of the current collector is heated, the heated current collector changes length due to linear expansion, becoming longer than its normal state, but the portion other than the heated portion maintains its normal length. Therefore, the amount of expansion cannot be converted into a change in overall length, and the excess length is absorbed by changing into a wavy shape. As a result, in a system in which a resin member is placed in close contact with a current collector and laser light is passed through the resin member and directed at the current collector to heat it, thereby raising the temperature of the sealing surface of the resin member at the interface with the current collector to its melting point and welding it, the resin member is unable to follow the undulations of the current collector caused by heating, and wrinkled, unwelded areas remain. In the present disclosure, in order to allow the resin member to be welded to follow the undulations of the current collector when heated, an elastic member, such as a soft rubber-based material, is used on one or both sides of the workpiece, which includes the current collector to be welded and the resin member that sandwiches the peripheral portion of the current collector. In the present disclosure, by sandwiching the workpiece between hard pressure members and a cushioning material such as a soft rubber-based material as an elastic member, a uniform pressure force can be applied even if undulations occur in the current collector during heating processing, thereby suppressing the occurrence of wrinkle-like uneven welding.

[0013] The manufacturing method of the present disclosure includes a welding step. The welding process is a process in which the resin member is positioned so as to sandwich the peripheral portion of the current collector, and the resin member is positioned so as to be sandwiched between pressure members, and the current collector and the resin member are pressed by the pressure members, and the resin member is welded to the current collector.

[0014] 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, 0.1 μm or more and 100 μm or less.

[0015] The resin members are arranged to sandwich the peripheral edge of the current collector, and the peripheral edge of the current collector is sandwiched between the pair of resin members, that is, the first resin member and the second resin member. The resin member may be a laser-transmitting material that transmits a laser. Examples of the resin member include various resin materials such as polyethylene, polypropylene, polystyrene, ABS resin, modified polypropylene, acrylonitrile styrene resin, etc. The resin member may be a resin film. The thickness of the resin member is, for example, not less than 10 μm and not more than 200 μm.

[0016] The resin member is disposed so as to be sandwiched between the pressure members. A workpiece including a current collector and a resin member sandwiching the peripheral 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 pressure members include aluminum, which is a material with low laser absorption, and glass, which is a hard, heat-resistant material with high laser transparency. 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.

[0017] Methods for welding a resin member to a current collector include laser welding (laser welding). Laser welding takes advantage of the high laser transparency of the resin member to be welded. Laser light is passed through the pressurized portion and resin member, and is absorbed and heated by the current collector. This heats the interface that requires direct bonding, improving processing energy efficiency. Furthermore, the temperature of the pressurized portion is less likely to rise, preventing the resin member from sticking to the pressurized member. Furthermore, by using a thin foil current collector, for example, less than 100 μm thick, the resin members on both sides of the current collector can be welded with a single laser irradiation.

[0018] In the welding step, the resin member may be welded to the current collector by a laser. The workpiece (workpiece) is a current collector sandwiched between resin members that are highly laser-transparent. A laser with a wavelength that is highly transparent to the resin members, for example, around 900 nm to 1200 nm, is used to irradiate the welded portion with the laser while pressing the workpiece with a pressure member, thereby heat-welding the current collector and the resin members, thereby achieving good adhesion between the current collector and the resin members. In the laser welding means, the heat welding process may be performed by scanning a laser beam profile over the entire area of ​​the workpiece that needs to be welded, or by fixing a wide laser beam profile and irradiating the entire area that needs to be welded for a certain period of time. The conditions such as laser output and scanning speed are not particularly limited and can be set appropriately.

[0019] In the welding step, an elastic member is disposed between the resin member and the pressure member on at least one side of the current collector. By disposing an elastic member such as a rubber-based material with high laser transmittance between the pressure member and the resin member on either the top or bottom side of the current collector, or on both sides, it is possible to suppress insufficient adhesion between the current collector and the resin member due to undulation caused by linear expansion of the current collector during heat welding processing, and to obtain a good welding state by stably adhering the current collector and the resin member over the entire processed area. In particular, an elastic member may be disposed between the pressing member and the resin member vertically below the current collector, and the resin member may be disposed in contact with the elastic member located vertically below the current collector. In the welding step, the laser may be irradiated onto the current collector from above in the vertical direction, with an elastic member disposed between the pressure member and the resin member vertically below the current collector.

[0020] The elastic member may be a rubber-like member or the like that has high laser transparency and high heat resistance, or may be silicone rubber (Shore A hardness 50) or the like. The elastic member may have a hardness of 30 to 70 in Shore A hardness. The elastic member may have a laser transmittance of 80% or more. The elastic member may have a heat resistance temperature of 110° C. or higher.

[0021] The secondary battery obtained by the manufacturing method of the present disclosure has a resin member welded to the peripheral edge of a current collector. The current collector may be made of one type of metal, or may be a laminated foil made by laminating foils of two or more types of metals.

[0022] The current collector usually has an electrode layer on the current collector in an inner area in the surface direction of the current collector, other than the area where the resin member to be welded to the periphery of the current collector is present. The electrode layer may be a positive electrode layer or a negative electrode layer. The current collector may be a negative electrode current collector, a positive electrode current collector, a bipolar current collector, or the like. In the secondary battery obtained by the manufacturing method of the present disclosure, a plurality of current collectors may be stacked in a stacking direction. The number of stacked current collectors is not particularly limited, and may be from 2 to several hundred. The secondary battery may include a negative electrode current collector, a negative electrode layer, an electrolyte layer, a positive electrode layer, and a positive electrode current collector.

[0023] The type of secondary battery of the present disclosure is not particularly limited, and examples thereof include nickel-metal hydride secondary batteries and lithium-ion secondary batteries. The secondary battery may be a liquid secondary battery using an electrolytic solution as the electrolyte, or a solid secondary battery using a solid electrolyte as the electrolyte. Examples of uses of secondary batteries include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, secondary batteries may be used as driving power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). Secondary batteries may also be used as power sources for mobile objects other than vehicles (e.g., railways, ships, and aircraft), and may also be used as power sources for electrical appliances such as information processing devices. [Example]

[0024] (Comparative Example 1) FIG. 1 is a cross-sectional view showing an example of the welding step at the peripheral edge of the current collector of Comparative Example 1. As shown in FIG. As shown in FIG. 1, in Comparative Example 1, a workpiece including a current collector and a resin member that sandwiches the peripheral portion of the current collector, and a pair of pressure members (glass as the first pressure member on the vertically upper side and aluminum as the second pressure member on the vertically lower side) that sandwich the workpiece were prepared. A laser was irradiated onto the workpiece from above in the vertical direction, and the resin material was welded to the periphery of the current collector. The laser irradiation was performed under the conditions of a scanning speed of 200 mm / sec, an output of 1100 W, and a beam width in the scanning direction of 40 mm. The results are shown in Figure 2. In FIG. 2, (1) is an image of the workpiece during the welding process of Comparative Example 1, and (2) is an image of the workpiece after the welding process of Comparative Example 1. As shown in Figure 1, the current collector expands linearly when heated, but cannot stretch due to frictional resistance because of the pressure applied, and undulations occur to absorb the excess length. This reduces the pressing pressure on the recesses, resulting in unwelded areas where the current collector and resin member are not welded. As shown in FIG. 2, it can be seen that unwelded portions were present in the workpiece after the welding process in Comparative Example 1.

[0025] Example 1 FIG. 3 is a cross-sectional view showing an example of the welding step at the peripheral edge of the current collector of Example 1. As shown in FIG. As shown in FIG. 3, in Example 1, the resin member was welded to the peripheral portion of the current collector in the same manner as in Comparative Example 1, except that silicone rubber (thickness: 2 mm, hardness: Shore A50, color: milky white) was placed as an elastic member between the second pressure member on the lower vertical side and the resin member. The results are shown in Figure 4. In FIG. 4, (1) is an image of the workpiece during the welding process of Example 1, and (2) is an image of the workpiece after the welding process of Example 1. As shown in Figure 3, the pressurized elastic member conforms to the undulations of the current collector, ensuring adhesion between the current collector and the resin member in a heated state, thereby preventing the occurrence of unwelded areas. As shown in FIG. 4, it can be seen that the workpiece after the welding process of Example 1 has fewer unwelded portions than the workpiece after the welding process of Comparative Example 1.

Claims

1. A method for manufacturing a secondary battery by welding a resin member to a peripheral portion of a current collector, the resin members are arranged to sandwich the peripheral edge portion of the current collector, and The resin member is disposed so as to be sandwiched between pressure members, and a welding step of welding the resin member to the current collector while the current collector and the resin member are pressed by the pressing member, In the welding step, an elastic member is disposed between the resin member and the pressure member on at least one side of the current collector.

2. In the welding step, the resin member is welded to the current collector by a laser, the resin member transmits the laser; the laser is irradiated onto the current collector from above in the vertical direction of the current collector, The method for manufacturing a secondary battery according to claim 1 , wherein the resin member is disposed in contact with the elastic member located vertically below the current collector.

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