Manufacturing method of secondary battery

Abstract

To provide a manufacturing method of a secondary battery, capable of suppressing a generation of a wrapping of a collector at a deposition to the collector of a resin member.SOLUTION: A manufacturing method of a secondary battery that is formed by depositing a resin member to a peripheral part of a collector having a first metal foil and a second metal foil, comprises a deposition step of depositing the resin member to the collector arranged so as to be nipped by the resin member. The first metal foil includes a first linear expansion coefficient, and the second metal foil includes a second linear expansion coefficient. The first linear expansion coefficient is larger than the second linear expansion coefficient. In the deposition step, a heat amount applied to the first metal foil is smaller than the heat amount applied to the second metal foil.SELECTED DRAWING: Figure 5

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 sealant (resin member) that seals the periphery of the current collector is welded by non-contact heating. When the sealant is welded to the current collector, the difference in linear expansion coefficient between the two types of metal foil that make up the current collector can cause the current collector to warp. In particular, when laser welding is performed from the metal foil side, which has a larger linear expansion coefficient, the current collector is directly heated, causing significant warping.

[0005] The present disclosure has been made in consideration of the above-mentioned situation, and has as its main object to provide a method for manufacturing a secondary battery that can suppress the occurrence of warping of a current collector when a resin member is welded to the 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 having a first metal foil and a second metal foil, a welding step of welding the resin member to the current collector disposed so as to be sandwiched between the resin members, The first metal foil has a first linear expansion coefficient; The second metal foil has a second linear expansion coefficient; the first linear expansion coefficient is greater than the second linear expansion coefficient; 2. A method for manufacturing a secondary battery, wherein in the welding step, the amount of heat applied to the first metal foil is smaller than the amount of heat applied to the second metal foil. By making the amount of heat applied to the first metal foil side, which has a larger linear expansion coefficient, smaller than that applied to the second metal foil side, the occurrence of warping of the current collector during welding of the resin member is suppressed.

[0007] <2> In the welding step, the resin member is welded to the current collector by a laser, The laser is irradiated from the second metal foil side. <1> A method for producing the secondary battery according to claim 1. By irradiating the laser from the side of the second metal foil, which has a relatively small linear expansion coefficient, warping of the current collector caused by differences in linear expansion coefficients is reduced.

[0008] <3> In the welding step, the resin member is welded to the current collector by a laser, the laser is irradiated from the first metal foil side with a first laser intensity and from the second metal foil side with a second laser intensity; The second laser intensity is greater than the first laser intensity. <1> A method for producing the secondary battery according to claim 1. When both metal foils are directly irradiated with a laser, the intensity of the laser irradiated from the second metal foil side, which has a relatively small linear expansion coefficient, is relatively high, thereby reducing the occurrence of warping of the current collector due to the difference in linear expansion coefficient.

[0009] <4> the resin member is in contact with a first member at a surface of the first metal foil opposite to a surface of the first metal foil in contact with the first metal foil, and is in contact with a second member at a surface of the second metal foil opposite to a surface of the second metal foil in contact with the second metal foil; The thermal conductivity of the first member is greater than the thermal conductivity of the second member. <2> A method for producing the secondary battery according to claim 1. The thermal conductivity of the first member in contact with the first metal foil having a larger linear expansion coefficient is greater than the thermal conductivity of the second member, thereby reducing the amount of linear expansion of the first metal foil. Effect of the Invention

[0010] The method for manufacturing a secondary battery according to the present disclosure can suppress the occurrence of warping of the current collector when the resin member is welded to the current collector. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an example of the welding step of Comparative Example 1. As shown in FIG. [Diagram 2] FIG. 2 is an image of the workpiece after the welding process of Comparative Example 1. [Diagram 3] FIG. 3 is an image of the workpiece after the welding process of Example 1. [Figure 4] FIG. 4 is a schematic diagram showing an example of the welding step of Comparative Example 2. As shown in FIG. [Diagram 5] FIG. 5 is a schematic diagram showing an example of the welding process of the second embodiment. [Figure 6] FIG. 6 is an image of the workpiece after the welding process of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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.

[0013] The present disclosure provides a method for producing a secondary battery by welding a resin member to a peripheral portion of a current collector having a first metal foil and a second metal foil, a welding step of welding the resin member to the current collector disposed so as to be sandwiched between the resin members, The first metal foil has a first linear expansion coefficient; The second metal foil has a second linear expansion coefficient; the first linear expansion coefficient is greater than the second linear expansion coefficient; The present invention provides a method for producing a secondary battery, wherein in the welding step, the amount of heat applied to the first metal foil is smaller than the amount of heat applied to the second metal foil.

[0014] As a method of sealing the outer periphery of a bipolar battery to prevent the electrolyte from seeping in, particularly when using laser welding of the foil and sealing film resin or a welding method involving heat such as an impulse sealer, the battery structural design requires that the foil be as thin as possible to improve energy density. In addition, it is necessary to ensure the potential resistance of the positive and negative electrodes and corrosion resistance through the formation of a coating, so it is necessary to select a metal that has as low a reactivity as possible throughout the year and as low an electrical resistance as possible for both the positive and negative electrode surfaces. As a result, it is difficult to make the foil sandwiched between the positive and negative electrodes out of a single type of metal, and the application of a dissimilar metal composite is generally considered. For this reason, when carrying out the sealing film welding process involving heating as described above, warping occurs due to the difference in linear expansion coefficients of the different metals, particularly as the size of the film increases and the welding length becomes longer, making it difficult to stack the film and create a battery while maintaining the intended shape. In the present disclosure, a laser is irradiated from the second metal foil side having a smaller linear expansion coefficient, and if necessary, a highly thermally conductive material is directly in contact with the first metal foil side having a larger linear expansion coefficient, thereby making the maximum temperature reached during heat welding between the two types of metal foil relatively low on the first metal foil side having a larger linear expansion coefficient and relatively high on the second metal foil side having a smaller linear expansion coefficient. By creating a heating temperature difference between the two types of metal foils that is opposite to the difference in linear expansion coefficients, the difference in the amount of expansion can be suppressed, and as a result, the dimensional difference at room temperature after cooling is reduced and warping can be suppressed.

[0015] The manufacturing method of the present disclosure includes a welding process. The welding step is a step of welding the resin member to the current collector arranged so as to be sandwiched between the resin members.

[0016] Methods for welding a resin member to a current collector include the impulse method, which uses heat conduction within the resin member to weld it to a metal foil, and 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 transmit through the pressurized part and resin, and absorbs and generates heat in the metal foil, thereby heating the interface that requires direct bonding, thereby improving processing energy efficiency and preventing adhesion to the pressurized part because the temperature of the pressurized part does not easily increase. In addition, by making the metal foil 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.

[0017] The resin material is polyethylene (PE, linear expansion coefficient: 100 to 200 × 10 -6 Examples of the resin material include various resin materials such as acrylic resin, 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 100 μm and not more than 120 μm.

[0018] The first metal foil has a first linear expansion coefficient and the second metal foil has a second linear expansion coefficient, the first linear expansion coefficient being greater than the second linear expansion coefficient. Metals that can be used for the metal foil include aluminum (linear expansion coefficient: 26.4 × 10 -6 @500K, 23.1×10 -6 @293K), copper (linear expansion coefficient: 18.3×10 -6 @500K, 16.5×10 -6 @293K), SUS, nickel, and other metals. For example, aluminum may be selected as the metal for the first metal foil and copper as the metal for the second metal foil. The thickness of the metal foil is, for example, not less than 0.1 μm and not more than 100 μm.

[0019] The first metal foil and the second metal foil may be bonded together with an adhesive layer. The thickness of the adhesive layer is, for example, not less than 0.1 μm and not more than 3 μm. The adhesive layer may be a thermoplastic resin.

[0020] The resin member side of the first metal foil and the resin member side of the second metal foil may be carbon-coated with a carbon coating layer. The carbon coating layer has a thickness of, for example, 0.1 μm or more and 1 μm or less.

[0021] In the welding step, the amount of heat applied to the first metal foil is smaller than the amount of heat applied to the second metal foil. In the welding step, the resin member may be welded to the current collector by a laser. The laser may be applied from the second metal foil side. When a collector formed of two types of metal foils in the thickness direction and a resin member are heat-welded at the interface between the metal foils and the resin member using a heating means such as a laser, by heating from the second metal foil side, which has a smaller linear expansion coefficient, it is possible to control the difference in the amount of expansion during heat processing and suppress processing defects due to warping.

[0022] The laser may be applied from the first metal foil side with a first laser intensity and from the second metal foil side with a second laser intensity, where the second laser intensity is greater than the first laser intensity. When heat input from both sides of the current collector is required, the amount of heat input to the first metal foil side, which has a larger linear expansion coefficient, can be reduced to control the difference in expansion during heat processing, thereby making it possible to suppress processing defects caused by warping.

[0023] The resin member may be in contact with the first member at a surface of the first metal foil opposite to a surface of the first metal foil that is in contact with the first member, and may be in contact with the second member at a surface of the second metal foil opposite to a surface of the second metal foil that is in contact with the second member, provided that the thermal conductivity of the first member is greater than the thermal conductivity of the second member. By adhering a metal with high thermal conductivity as the first component to the first metal foil with a large linear expansion coefficient, it is possible to control the difference in the amount of expansion during heat processing and suppress processing defects due to warping. The current collector and the resin member may be sandwiched between a first member and a second member and pressed by the first member and the second member. On the side of the first metal foil opposite the side of the second metal foil (heated surface) that is irradiated with the laser light, it is desirable to support it with a material with a thermal conductivity of 15 W / (m K)@100°C or more, such as a metal, as the first member. The first member may be made of aluminum, stainless steel or the like. The second member may be made of SUS, glass, hard rubber, PE, silicone rubber, or the like. For reference, the thermal conductivity of glass (quartz glass) is 1.4 W / (m·K)@0℃, 1.9 W / (m·K)@100℃, aluminum is 236 W / (m·K)@0℃, 240 W / (m·K)@100℃, SUS is 15 W / (m·K)@0℃, 16.5 W / (m·K)@100℃, hard rubber is 0.2 W / (m·K)@0℃, and PE is 0.25~0.34 W / (m·K)@room temperature.

[0024] The secondary battery obtained by the manufacturing method of the present disclosure is formed by welding a resin member to the periphery of a current collector including a first metal foil and a second metal foil. The current collector includes a first metal foil and a second metal foil. The current collector is not limited to a laminated foil in which the first metal foil and the second metal foil are laminated together, and the two metal foils may be welded at their ends with a resin member.

[0025] 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.

[0026] 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

[0027] Comparative Example 1 FIG. 1 is a schematic diagram showing an example of the welding step of Comparative Example 1. As shown in FIG. As shown in Figure 1, a workpiece was prepared using glass as the second member, PE (120 μm) as the resin member, a carbon coating layer (<1 μm), aluminum foil (40 μm) as the second metal foil, an adhesive layer (3 μm), copper foil (7.8 μm) as the first metal foil, a carbon coating layer (<1 μm), PE (120 μm) as the resin member, and glass as the first member. A laser was applied from the second metal foil (aluminum foil) side, and the resin member was welded to the periphery of the current collector including the first metal foil and the second metal foil. In Comparative Example 1, the first linear expansion coefficient (18.3 × 10 -6 @500K) is the second linear expansion coefficient of the second metal foil (aluminum foil) (26.4 × 10 -6 @500K). The results are shown in Figure 2 and Table 1. FIG. 2 is an image of the workpiece after the welding process of Comparative Example 1. As shown in FIG. 2, warping occurred in the workpiece after the welding process in Comparative Example 1. During heat welding, the difference in linear expansion coefficients causes aluminum to expand more than copper. As a result, stress in the elongation direction occurs on the thinner copper side, which is fixed with an adhesive layer, causing stress strain in the plastic region. When the temperature returns to room temperature, it is assumed that the copper side has a longer linear length due to plastic deformation, which causes warping. As for PE, it is assumed that it is not involved in warping because it slides at the interface and the interface is fixed as the temperature drops.

[0028] Example 1 Except for preparing a workpiece using aluminum foil (40 μm) as the first metal foil and copper foil (7.8 μm) as the second metal foil, a laser was irradiated from the second metal foil (copper foil) side in the same manner as in Comparative Example 1, and a resin member was welded to the peripheral portion of the current collector. In Example 1, the first linear expansion coefficient (26.4 × 10 -6 @500K) is the second linear expansion coefficient of the second metal foil (copper foil) (18.3 × 10 -6 @500K). FIG. 3 is an image of the workpiece after the welding process of Example 1. As shown in FIG. 3, warping of the workpiece after the welding process in Example 1 is suppressed. The laser irradiated side is the second metal foil (copper foil) side, which has a low linear expansion coefficient, and the temperature reached on the laser irradiated side of the second metal foil (copper foil) with a low linear expansion coefficient is higher than the temperature reached on the opposite laser irradiated side of the first metal foil (aluminum foil) with a high linear expansion coefficient.This mitigates the difference in the amount of expansion between the aluminum and copper, reduces the stress strain and line length difference in the plastic region on the second metal foil (copper foil) side, and improves warping.

[0029] Comparative Example 2 FIG. 4 is a schematic diagram showing an example of the welding step of Comparative Example 2. As shown in FIG. As shown in FIG. 4, a resin member was welded to the periphery of a current collector in the same manner as in Comparative Example 1, except that a workpiece made of aluminum was prepared as the first member. In Comparative Example 2, the first linear expansion coefficient (18.3 × 10 -6 @500K) is the second linear expansion coefficient of the second metal foil (aluminum foil) (26.4 × 10 -6 @500K) and the thermal conductivity of the first member (aluminum) is greater than the thermal conductivity of the second member (glass). By changing the first receiving component from glass, which has low thermal conductivity, to aluminum, which has high thermal conductivity, the temperature difference reached between the second metal foil (aluminum foil) side, which has a high linear expansion coefficient on the laser irradiated side, and the first metal foil (copper foil) side, which has a low linear expansion coefficient on the opposite laser irradiated side, further increased.As a result, the difference in the amount of expansion between the aluminum and copper increased, and the stress strain and line length difference in the plastic region on the copper side also increased, resulting in a worsening warping condition than in Comparative Example 1.

[0030] Example 2 FIG. 5 is a schematic diagram showing an example of the welding process of the second embodiment. As shown in FIG. 5, a workpiece was prepared using aluminum foil (40 μm) as the first metal foil, copper foil (7.8 μm) as the second metal foil, and aluminum as the first member. Laser was irradiated from the second metal foil (copper foil) side in the same manner as in Comparative Example 1, and a resin member was welded to the peripheral portion of the current collector. In Example 2, the first linear expansion coefficient (26.4 × 10 -6 @500K) is the second linear expansion coefficient of the second metal foil (copper foil) (18.3 × 10 -6 @500K) and the thermal conductivity of the first member (aluminum) is greater than the thermal conductivity of the second member (glass). FIG. 6 is an image of the workpiece after the welding process of Example 2. As shown in FIG. 6, warping of the workpiece after the welding process in Example 2 is suppressed. By using the second metal foil (copper foil) with a low linear expansion coefficient on the laser irradiated side and using aluminum with good thermal conductivity as the first component on the receiving side, the temperature reached on the second metal foil (copper foil) with a low linear expansion coefficient on the laser irradiated side is higher than the first metal foil (aluminum foil) with a high linear expansion coefficient on the opposite side to the laser irradiated side. This mitigates the difference in the amount of expansion between aluminum and copper, reduces the stress strain and line length difference in the plastic region on the second metal foil (copper foil) side, and further improves warping compared to Example 1.

[0031] (Examples 3 to 6, Comparative Examples 3 to 6) Except for the conditions shown in Table 1, laser irradiation was performed from the second metal foil side in the same manner as in Comparative Example 1, and the resin member was welded to the peripheral edge portion of the current collector.

[0032] [Table 1]

[0033] In Examples 3 to 6, the laser irradiated side was the second metal foil (copper foil) side, which has a low linear expansion coefficient, and this mitigated the difference in the amount of expansion between aluminum and copper, thereby reducing the stress strain and linear length difference in the plastic region on the second metal foil (copper foil) side, and suppressing warping. On the other hand, in Comparative Examples 3 to 6, the laser irradiated side was the second metal foil (aluminum foil) side with a high linear expansion coefficient, and the difference in the amount of expansion between this and the first metal foil (copper foil) side with a low linear expansion coefficient on the opposite side to the laser irradiated side increased, causing warping. Furthermore, as shown in Comparative Examples 2 to 6, when the amount of heat applied to the first metal foil is greater than the amount of heat applied to the second metal foil in the welding process, warping occurs even if the thermal conductivity of the first component is greater than the thermal conductivity of the second component.

Claims

1. A method for manufacturing a secondary battery by welding a resin member to a peripheral portion of a current collector having a first metal foil and a second metal foil, a welding step of welding the resin member to the current collector disposed so as to be sandwiched between the resin members, The first metal foil has a first linear expansion coefficient; The second metal foil has a second linear expansion coefficient; the first linear expansion coefficient is greater than the second linear expansion coefficient; A method for manufacturing a secondary battery, wherein in the welding step, the amount of heat applied to the first metal foil is smaller than the amount of heat applied to the second metal foil.

2. In the welding step, the resin member is welded to the current collector by a laser, The method for producing a secondary battery according to claim 1 , wherein the laser is irradiated from the second metal foil side.

3. In the welding step, the resin member is welded to the current collector by a laser, The laser is irradiated from the first metal foil side with a first laser intensity and from the second metal foil side with a second laser intensity; The method for manufacturing a secondary battery according to claim 1 , wherein the second laser intensity is greater than the first laser intensity.

4. the resin member contacts a first member at a surface of the first metal foil opposite to a surface of the first metal foil that contacts the first metal foil, and contacts a second member at a surface of the second metal foil opposite to a surface of the second metal foil that contacts the second metal foil, The method for manufacturing a secondary battery according to claim 2 , wherein the thermal conductivity of the first member is greater than the thermal conductivity of the second member.

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