Method for manufacturing battery

Abstract

To appropriately weld a resin sealant to a peripheral edge portion of a current collector by laser irradiation while restraining deformation of the current collector caused by the laser irradiation.SOLUTION: A method for manufacturing a battery including a laminate containing a current collector 11 and a sealing portion for sealing the laminate, includes overlapping a sealing material 24B (resin sealing material) for forming the sealing portion on the current collector 11 such that one end (E1) of the sealing material 24B is located on the current collector 11 and the other end (E2) of the sealing material 24B is located outside the end face (E3) of the current collector 11, and welding the sealing material 24B to the current collector 11 by irradiating the current collector 11 in an irradiation region with a laser beam transmitted through the sealing material 24B from the sealing material 24B side according to a non-irradiated region (d2) and an irradiated region (d3) set in an overlapping portion (d1) where the current collector 11 and the sealing material 24B overlap with each other. The non-irradiated region is set in a range from 1% or more to 20% or less of the overlapping portion from the one end (E1) of the sealing material 24B.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Japanese Patent Application Laid-Open No. 2019-142240 (Patent Document 1) discloses a technology in which a resin member that is transparent to laser light and glass are superimposed on a metal, in that order, and laser light is irradiated from the resin member side through the glass to the joint where the metal and resin members are superimposed, to join them at a joining speed of 0.5 to 5.0 m / min. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-142240 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is conceivable that the technology described in the above Patent Document 1 is used in the manufacture of batteries. Specifically, the technology described in the above Patent Document 1 may be used to weld a resin sealant for forming a sealing portion of a battery to the periphery of a current collector of a battery. However, depending on the conditions of the laser irradiation, the current collector may be deformed, or the resin sealant may not be sufficiently welded to the periphery of the current collector. In particular, when welding a resin sealant to the periphery of a current collector, the laser irradiation position is likely to affect the performance of the battery. The above Patent Document 1 does not mention the laser irradiation conditions suitable for welding a resin sealant to the periphery of a current collector.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to appropriately weld a resin sealing material to the peripheral portion of a current collector by laser irradiation while suppressing deformation of the current collector caused by laser irradiation. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, there is provided a method for manufacturing a battery including a laminate including a current collector and a sealing portion for sealing the laminate. The method for manufacturing the battery includes overlapping a resin sealant for forming a sealing portion on the current collector such that one end of the resin sealant is located on the current collector and the other end of the resin sealant is located outside the end face of the current collector, and welding the resin sealant to the current collector by irradiating the current collector in the irradiation region from the resin sealant side with a laser beam that is transmitted through the resin sealant according to an irradiation region and a non-irradiation region set in the overlapping portion where the current collector and the resin sealant overlap. The non-irradiation region is set in a range of 1% to 20% of the overlapping portion from the one end of the resin sealant. Effect of the Invention

[0007] According to the present disclosure, it is possible to appropriately weld a resin sealant to the peripheral edge of a current collector by laser irradiation while suppressing deformation of the current collector caused by laser irradiation. [Brief description of the drawings]

[0008] [Figure 1] 1A to 1C are diagrams illustrating an example of a battery manufactured by a battery manufacturing method according to an embodiment of the present disclosure. [Diagram 2] 1A to 1C are diagrams showing steps of a method for manufacturing a battery according to an embodiment of the present disclosure. [Diagram 3] 3 is a diagram for explaining the laser irradiation step shown in FIG. 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated. In each of the drawings used below, the Z axis of the mutually orthogonal X-axis, Y-axis, and Z-axis indicates the thickness direction of the battery. Hereinafter, the directions indicated by the arrows of the X-axis, Y-axis, and Z-axis are indicated by "+" and the opposite directions are indicated by "-". With regard to the two main surfaces (front and back) of a plate-like member (or its laminate), the surface in the +Z direction may be referred to as the "first surface" and the surface in the -Z direction as the "second surface".

[0010] FIG. 1 is a cross-sectional view showing an electricity storage module 10 (battery) manufactured by the battery manufacturing method according to this embodiment. The type of battery manufactured is arbitrary, and may be, for example, a lithium ion secondary battery. With reference to FIG. 1, the electricity storage module 10 includes an electrode stack 1a and a sealing portion 3 that seals the electrode stack 1a. The electrode stack 1a includes a plurality of electrodes (a plurality of bipolar electrodes 1, one negative terminal electrode 2A, and one positive terminal electrode 2B) stacked in the Z direction (stacking direction). A separator 13 is disposed between the electrodes.

[0011] The bipolar electrode 1 includes a current collector 11, a negative electrode active material layer 12A provided on the second surface of the current collector 11, and a positive electrode active material layer 12B provided on the first surface of the current collector 11. The current collector 11 is, for example, a conductive plate material having a rectangular shape in an XY plan view. The negative electrode active material layer 12A is formed in the center on the second surface of the current collector 11. The positive electrode active material layer 12B is formed in the center on the first surface of the current collector 11. In this embodiment, no active material layer is formed on the peripheral portion of the current collector 11. For example, a composite oxide containing one or more elements selected from the group consisting of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium may be used as the positive electrode active material. Examples of such composite oxides include lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2. Examples of the negative electrode active material include a carbon-based material, a metal compound, and a composition containing an element that can be alloyed with lithium. Examples of elements that can be alloyed with lithium include silicon and tin.

[0012] The negative terminal electrode 2A has a configuration in which the positive electrode active material layer 12B has been removed from the bipolar electrode 1. The positive terminal electrode 2B has a configuration in which the negative electrode active material layer 12A has been removed from the bipolar electrode 1. The separator 13 is formed in a rectangular shape when viewed in the XY plane. The separator 13 contains, for example, a polymer that absorbs and retains an electrolyte. A plurality of bipolar electrodes 1 are stacked, and a separator 13 is disposed between adjacent bipolar electrodes 1. A separator 13 is also disposed between each terminal electrode and the bipolar electrode 1 adjacent thereto.

[0013] The sealing portion 3 is formed so as to surround the electrode laminate 1a. The sealing portion 3 includes a first sealing layer 14A, a second sealing layer 14B, and a spacer layer 15. The first sealing layer 14A, the second sealing layer 14B, and the spacer layer 15 each have a rectangular frame shape when viewed from the stacking direction. The spacer layer 15 is located between the first sealing layer 14A and the second sealing layer 14B in the stacking direction. The outer edge portion of the spacer layer 15 is joined (welded) to the outer edge portions of the adjacent first sealing layer 14A and second sealing layer 14B.

[0014] The first seal layer 14A and the second seal layer 14B are provided on each current collector 11 and hold the peripheral portion of the corresponding current collector 11. The first seal layer 14A and the second seal layer 14B are in contact with the second surface and the first surface of the current collector 11, respectively. The peripheral portion of the separator 13 is bonded to the first surface of the second seal layer 14B. The space surrounded by the sealing portion 3 (between the electrode laminate 1a and the sealing portion 3) is filled with an electrolyte, and the electrolyte is impregnated into the separator 13. Examples of the electrolyte include a liquid electrolyte (electrolytic solution) containing a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent, or a polymer gel electrolyte containing an electrolyte held in a polymer matrix. An insulating material having resistance to the electrolyte is used as the material constituting the sealing portion 3.

[0015] FIG. 2 is a diagram showing the steps of the method for manufacturing a battery according to this embodiment. "S" in FIG. 2 means a step. Prior to S1, each electrode (multiple bipolar electrodes 1, a negative terminal electrode 2A, and a positive terminal electrode 2B) is prepared. Examples of the method for forming each electrode include roll coating, die coating, dip coating, and spray coating.

[0016] In S1, the seal materials 24A and 24B are arranged on the bipolar electrode 1. Specifically, the seal materials 24A and 24B are overlapped on the current collector 11 of the bipolar electrode 1 so that one end of each seal material is located on the current collector 11 of the bipolar electrode 1 and the other end of each seal material is located outside the end face of the current collector 11 of the bipolar electrode 1. The seal materials 24A and 24B are resin seal materials for forming the first seal layer 14A and the second seal layer 14B shown in FIG. 1, respectively. Each of the seal materials 24A and 24B is, for example, a rectangular resin film (see FIG. 3 described later). Each of the seal materials 24A and 24B is arranged along the periphery of the current collector 11. The seal materials 24A and 24B are arranged on the -Z side and the +Z side of the current collector 11, respectively. The seal material 24A and the seal material 24B have the same size and shape, and are disposed at the same position when viewed in the XY plane.

[0017] In this embodiment, a metal foil is used as the current collector 11. The current collector 11 may be a laminated foil (for example, a laminated foil of aluminum foil and copper foil). The thickness of the current collector 11 is arbitrary, but is preferably 1 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less. By optimizing the thickness, sufficient strength and thermal conductivity are both achieved. Furthermore, each of the seal materials 24A and 24B is formed of a thermoplastic resin. In this embodiment, the seal materials 24A and 24B made of polyethylene are used. The thickness of each of the seal materials 24A and 24B is arbitrary, but is preferably 50 μm or more and 250 μm or less, more preferably 100 μm or more and 150 μm or less. By optimizing the thickness, sufficient adhesion and translucency are both achieved. In this embodiment, the current collector 11 is thinner than each of the seal materials 24A and 24B. The material constituting each sealant is not limited to polyethylene, but may be polypropylene, acid-modified polyethylene, or acid-modified polypropylene.

[0018] In the next step S2, the welding device welds each of the seal materials 24A and 24B to the periphery of the current collector 11 of the bipolar electrode 1. The welding device includes a semiconductor laser as a laser light source. The wavelength of the laser light irradiated from the semiconductor laser is, for example, less than 2 μm and may be in the ultraviolet region. The semiconductor laser may be a laser that utilizes harmonic generation (THG, FHG, etc.). In S2, the semiconductor laser irradiates the current collector 11 with a laser light from the seal material 24B side (+Z side). The seal material 24B transmits the laser light, and the current collector 11 absorbs the laser light. Then, the energy absorbed by the current collector 11 is converted into heat. As a result, the seal materials 24A and 24B are heated and melted on the surface of the current collector 11, and the current collector 11 and each of the seal materials 24A and 24B are welded to each other. The laser light transmittance of the seal material 24B is preferably 50% or more, more preferably 80% or more. S2 will be further explained below with reference to FIG.

[0019] FIG. 3 is a diagram showing the periphery of the current collector 11 in S2. In the upper XY plan view of FIG. 3, the illustration of the pressurizing members 210 and 220 described later is omitted. In FIG. 3, E1 and E2 respectively indicate the positions of the first end (one end) and the second end (the other end) in the X direction (short direction) of the seal materials 24A and 24B. E3 indicates the position of the end face on the +X side of the current collector 11 of the bipolar electrode 1. For each of the seal materials 24A and 24B, E1 (first end) is located on the current collector 11, and E2 (second end) is located outside (+X side) of E3. The overlapping portion is a portion where the current collector 11 and each of the seal materials 24A and 24B overlap. In this embodiment, an irradiation area to which the laser light is irradiated and a non-irradiation area to which the laser light is not irradiated are set in the overlapping portion. In FIG. 3, d1 indicates the dimension of the overlapping area in the X direction (the dimension from E1 to E3). d2 indicates the dimension of the non-irradiated area in the X direction. d3 indicates the dimension of the irradiated area in the X direction. The irradiated area is adjacent to the +X side of the non-irradiated area. In this embodiment, the area from the -X side end (E1) of the overlapping area to a position on the +X side by d2 is set as the non-irradiated area. Also, the area from the +X side end of the non-irradiated area to the +X side end (E3) of the overlapping area is set as the irradiated area.

[0020] In the example shown in FIG. 3, the current collector 11 and the seal materials 24A and 24B arranged in S1 in FIG. 2 are sandwiched between a glass pressurizing member 210 (+Z side) and an aluminum pressurizing member 220 (-Z side), and the pressurizing members 210 and 220 are pressed using pressurizing devices 211, 212, 221, and 222 (see the XX cross section in FIG. 3). The pressurizing devices 211 and 221 generate force, for example, by an air cylinder, and apply the force near E1 (first end). The pressurizing devices 212 and 222 generate force, for example, by an air cylinder, and apply the force near E2 (second end). These forces are transmitted to the seal materials 24A and 24B via the pressurizing members 210 and 220, and each of the seal materials 24A and 24B is pressed toward the current collector 11. Each pressurizing device is arranged to avoid the laser irradiation range so as not to interfere with the laser irradiation. In S2 in FIG. 2, the laser irradiation is performed in the above-mentioned pressurized state. The portion of the current collector 11 covered with the seal materials 24A and 24B (pressurized portion: the portion corresponding to the overlapping portion) is pressurized by the force from each of the seal materials 24A and 24B. On the other hand, the portion of the current collector 11 not covered with the seal materials 24A and 24B (non-pressurized portion: the portion on the -X side of E1) is not pressurized.

[0021] In S2, the laser light transmitted through the pressing member 210 and the sealing material 24B is irradiated from the +Z side of the pressing member 210 onto the current collector 11 in the irradiation region, thereby welding each of the sealing materials 24A and 24B to the current collector 11. Since the current collector 11 is sufficiently thin, heat conduction is promoted, and it is possible to weld a resin (sealing material) to both sides of the current collector 11 by irradiating the laser from one side. At this time, the pressing member 220 reflects the laser light. Since the pressing member 220 does not easily absorb the laser light, adhesion (sticking) between the sealing material 24A and the pressing member 220 is suppressed.

[0022] 3, dx and dy respectively indicate the dimensions in the X and Y directions of the laser profile (the range where the laser head irradiates the laser light). By scanning the laser profile in the Y direction, the sealing material 24B is irradiated with laser light of width dx from one end to the opposite end in the Y direction (longitudinal direction). An example of the laser irradiation conditions is a laser output of 50 to 2500 W, a scanning direction length of 5 to 80 mm, a scanning speed of 50 to 500 mm / sec, and an energy density of 0.5 to 2.0 W / mm 2 The position of the laser beam (particularly the end on the -X side) is set according to the above-mentioned irradiation area. The non-irradiated area is not irradiated with the laser beam. On the other hand, the laser beam is also irradiated to the outside (+X side) of E3 (the end face of the current collector 11). dx is larger than d3 by d4 (dx=d3+d4). This makes it easier to weld the resin (sealing material) to both sides of the current collector 11 with a single laser irradiation. The size of d4 is preferably 0.5 mm or more, more preferably 0.5 mm or more and 1.5 mm or less.

[0023] The non-irradiated region is set in a range of 1% to 20% of the overlapping portion from E1 (first end of the seal materials 24A and 24B). That is, d2 is set to a size of 1% to 20% of d1. For example, in a form in which d1 is 100 mm, d2 is set to 1 to 20 mm. d1 may be 5 to 100 mm and d2 may be 1 to 2 mm. By setting such a non-irradiated region, it becomes possible to appropriately weld the resin seal materials (seal materials 24A and 24B) to the peripheral portion of the current collector 11 by laser irradiation while suppressing deformation of the current collector 11 caused by laser irradiation.

[0024] Specifically, in the comparative example shown in FIG. 3, no non-irradiated region is provided (d2=0). In this comparative example, the pressurized portion of the current collector 11 covered with the seal materials 24A and 24B is irradiated with a laser beam, and the pressurized portion is heated. At this time, since the thermal conductivity of the current collector 11 (metal foil) is high, heat is diffused around the heating portion. The non-pressurized portion of the current collector 11 is not directly heated by the laser beam, but the temperature is increased by the transfer of heat from the pressurized portion. Since the pressurized portion of the current collector 11 is pressurized from each of the seal materials 24A and 24B, deformation (expansion) due to temperature increase is suppressed. On the other hand, since the non-pressurized portion of the current collector 11 is not covered with the seal materials 24A and 24B and is in contact with an air layer with low thermal conductivity, it is easy to deform and to increase in temperature. In particular, in a form in which the current collector 11 is a thin metal foil, wavy deformation (linear expansion) as shown in FIG. 3 is likely to occur. Such deformation of current collector 11 not only damages current collector 11 itself, but also spreads to seal materials 24A and 24B, deteriorating the welding condition in the vicinity of E1 and causing warping defects.

[0025] In contrast, in the embodiment shown in FIG. 3, a non-irradiated region where the laser light is not irradiated is set in the overlapping portion. The seal materials 24A and 24B in the non-irradiated region pressurize the current collector 11 to suppress deformation of the current collector 11 and absorb heat from the current collector 11. The non-irradiated region functions as a heat transfer buffer area at the boundary between the non-pressurized portion and the pressurized portion of the current collector 11. By setting d2 to 1% or more of d1, the temperature rise of the current collector 11 is sufficiently suppressed by heat dissipation by each seal material in the non-irradiated region. On the other hand, if d2 is made too large, the range where the laser light is not irradiated will be expanded, and the welding near E1 will be insufficient. Therefore, in this embodiment, d2 is set to 20% or less of d1. By not making d2 too large, it is possible to appropriately weld the resin seal materials (seal materials 24A and 24B) to the peripheral portion of the current collector 11 by laser irradiation. d2 may be set to 5% to 10% of d1 in consideration of the positional deviation of the laser irradiation. This will more reliably ensure proper welding.

[0026] 3 shows a method of welding the seal materials 24A and 24B located on one side (the +X side edge) of the four sides (four peripheral parts) of the current collector 11 constituting the bipolar electrode 1. However, the seal materials 24A and 24B are also welded to the other peripheral parts (three sides) of the current collector 11 in the same manner as the peripheral parts shown in FIG. 3. The seal materials on the four sides may be joined together. The seal materials on the four sides are integrated to form a frame. This provides a bipolar electrode 1 whose periphery is sealed with resin. The seal materials 24A on the four sides and the seal materials 24B on the four sides may be integrated to form a frame by end face welding (S6) described later.

[0027] Referring again to FIG. 2, in the next step S3, the separator 13 is prepared, and in the further next step S4, the seal material 24B and the separator 13 are welded together. The welding method may be a contact method (for example, hot iron welding) or a non-contact method (for example, laser welding). The processes of S1 to S4 are performed for each of the plurality of bipolar electrodes 1. As a result, a plurality of electrode units 1b are obtained. The electrode unit 1b is a composite of the bipolar electrode 1, the seal materials 24A and 24B, and the separator 13. The processes of S1 to S3 are also performed for each of the negative terminal electrode 2A and the positive terminal electrode 2B. Furthermore, the process of S4 is also performed for the positive terminal electrode 2B.

[0028] In the next step S5, the obtained electrode units 1b are stacked via a spacer layer 15. This results in a stack including the electrode units 1b. Furthermore, a negative terminal electrode 2A is disposed at the end of the stack on the +Z side via a spacer layer 15, and a positive terminal electrode 2B is disposed at the end of the stack on the -Z side via a spacer layer 15.

[0029] In the next step S6, the peripheral portion (end portion) of the laminate formed in S5 is welded, for example, by IR welding (infrared welding). This welds the end faces of the peripheral portion of the laminate, and the seal material 24A (first seal layer 14A), the seal material 24B (second seal layer 14B), and the spacer layer 15 are integrated together. As a result, the sealing portion 3 is formed, and the energy storage module 10 shown in FIG. 1 is completed. After S6, a resin portion may be added to the energy storage module 10 by injection molding.

[0030] The energy storage module 10 shown in FIG. 1 can function as a battery by itself. However, a battery may be manufactured by combining a plurality of such energy storage modules 10. For example, a plurality of energy storage modules 10 may be stacked so that the plurality of energy storage modules 10 are electrically connected in series, and the stacked plurality of energy storage modules 10 may be sandwiched between a pair of end plates. A battery including the energy storage module 10 may be mounted on, for example, a mobile body. Examples of mobile bodies include automobiles (electric vehicles, hybrid vehicles, etc.), mobile machines (agricultural machines, construction machines, etc.), and unmanned guided vehicles. However, the use of the manufactured battery is arbitrary, and a stationary battery may be manufactured by the above method. A battery having a monopolar electrode may be manufactured by the above method.

[0031] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0032] 1 bipolar electrode, 1a electrode laminate, 3 sealing portion, 10 electricity storage module, 11 current collector, 14A first sealing layer, 14B second sealing layer, 15 spacer layer, 24A, 24B sealing materials.

Claims

[Claim 1] A method for producing a battery including a laminate including a current collector and a sealing portion that seals the laminate, comprising the steps of: overlapping a resin seal material for forming the sealing portion on the current collector such that one end of the resin seal material is positioned on the current collector and the other end of the resin seal material is positioned outside an end face of the current collector; irradiating the current collector in the irradiation region from the resin sealant side with a laser beam that is transmitted through the resin sealant according to an irradiation region and a non-irradiation region set in an overlapping portion where the current collector and the resin sealant overlap, thereby welding the resin sealant to the current collector; Including, A method for manufacturing a battery, wherein the non-irradiated area is set in a range of 1% to 20% from the one end of the resin sealing material to the overlapping portion.

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