Method for producing secondary battery

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] JP 2023-000059 A 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 by non-contact heating. When the resin member is welded to the current collector, undulations occur in the current collector due to linear expansion, which can reduce 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 has as its main object to provide a method for manufacturing a secondary battery that can suppress the occurrence of unwelded parts 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, comprising the steps of: The resin members are disposed to sandwich the peripheral 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, a pressing member disposed between the resin member and the pressing member on at least one side of the current collector in the welding step; 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 a vertical direction of the current collector, the resin member is disposed in contact with the elastic member located vertically below the current collector; <1> A method for producing the secondary battery according to claim 1. By positioning the elastic member in contact only vertically below the current collector, the occurrence of wrinkles in the current collector due to deformation of the elastic member caused by gravity can be suppressed, while the resin member and the current collector can be adhered closely regardless of wrinkles in the current collector, thereby suppressing the occurrence of unwelded areas. Effect of the Invention

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

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

[0010] 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, the general configuration and manufacturing process of a secondary battery that does 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.

[0011] The present disclosure provides a method for producing a secondary battery by welding a resin member to a peripheral portion of a current collector, comprising the steps of: The resin members are disposed to sandwich the peripheral 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 into a bipolar battery, from the viewpoint of the structural design of the battery, it is necessary to make the current collector as thin as possible to improve the 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 and becomes longer than its normal state, but the normal length is maintained outside the heated portion. Therefore, the amount of expansion cannot be converted into a change in overall length, and the excess length is absorbed by a wavy shape change. As a result, in a system in which a resin member is placed in close contact with a current collector and laser light is then passed through the resin member and directed at the current collector to heat it and weld the sealing surface made of the resin member at the interface with the current collector by raising the temperature to its melting point, 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 part 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 either the top or bottom, or both sides, of the workpiece including the current collector to be welded and the resin part 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 and processing, thereby suppressing the occurrence of wrinkle-like uneven welding.

[0013] The manufacturing method of the present disclosure includes a welding process. The welding process is a process in which the resin member is positioned so as to sandwich the peripheral portion of the current collector, the resin member is positioned so as to be sandwiched between a pressure member, and the current collector and the resin member are pressurized by the pressure member, 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, not less than 0.1 μm and not more than 100 μm.

[0015] The resin members are disposed so as to sandwich the peripheral portion of the current collector. The peripheral portion 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 material that is laser-transparent and allows the laser to pass therethrough. 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 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.

[0017] Examples of methods for welding a resin member to a current collector include a laser welding method (laser welding method). The laser welding method focuses on the high laser transparency of the resin member to be welded, and uses a laser beam to pass through the pressurized part and the resin member, and the current collector absorbs and heats the interface that requires direct bonding, thereby improving processing energy efficiency and preventing the resin member from sticking to the pressurized member because the temperature of the pressurized part is unlikely to increase. In addition, by making the current collector a thin foil, for example 100 μm or less, 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), which is a current collector sandwiched between resin members with high laser transparency, is irradiated with a laser having a wavelength that is highly transparent to the resin members, for example, around 900 nm to 1200 nm, and the laser is applied to the welded portion while applying pressure to the workpiece with a pressure member, thereby heat-welding the current collector and the resin members, thereby obtaining 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 the 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 the linear expansion of the current collector during the heat welding process, 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. Also, the resin member may be disposed in contact with the elastic member located vertically below the current collector. In the welding step, a laser may be irradiated onto the current collector from above in the vertical direction, with an elastic member being disposed between the pressure member and the resin member vertically below the current collector.

[0020] The elastic member may be a rubber-like member having high laser transparency and high heat resistance, or may be silicone rubber (Shore A hardness 50). 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 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 of two or more types of metal foils laminated together.

[0022] The current collector generally has an electrode layer on an inner region in the surface direction of the current collector, which is a region other than the region 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 current collector, a positive 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 the 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-based secondary battery using an electrolytic solution as an electrolyte, or a solid secondary battery using a solid electrolyte as an electrolyte. Examples of uses of the secondary 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 secondary 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 secondary 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

[0024] Comparative Example 1 FIG. 1 is a cross-sectional view showing an example of a welding step for the peripheral portion 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 clamps the peripheral portion of the current collector, and a pair of pressure members (glass as a first pressure member on the vertical upper side and aluminum as a second pressure member on the vertical lower side) that clamp the workpiece were prepared. The workpiece was irradiated with a laser 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 of 40 mm in the scanning direction. The results are shown in Figure 2. FIG. 2 shows (1) an image of the workpiece during the welding process of Comparative Example 1, and (2) 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 it is under pressure, and undulations occur to absorb the excess length. Then, the pressing pressure on the recesses decreases, and unwelded areas occur where the current collector and the resin member cannot be welded. As shown in FIG. 2, it is found that unwelded portions were generated in the workpiece after the welding process in Comparative Example 1.

[0025] Example 1 FIG. 3 is a schematic cross-sectional view showing an example of a welding step in the peripheral portion of the current collector in 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 disposed as an elastic member between the second pressure member on the vertical lower side and the resin member. The results are shown in Figure 4. FIG. 4 shows (1) an image of the workpiece during the welding process of Example 1, and (2) an image of the workpiece after the welding process of Example 1. As shown in FIG. 3, the pressurized elastic member conforms to the undulations of the current collector, ensuring sufficient 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 in Example 1 has a reduced number of unwelded portions compared to the workpiece after the welding process in 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, comprising the steps of: The resin members are disposed to sandwich the peripheral 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 pressure member, a pressing member disposed between the resin member and the pressing member on at least one side of the current collector in the welding step;

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 a vertical direction of the current collector, The method for producing 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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