Method for manufacturing battery

Abstract

To enable a resin seal material and a separator to be suitably welded to each other without contact.SOLUTION: A method for manufacturing a battery including a laminate containing a current collector 11 and a separator 13, and a sealing portion 3 for sealing the laminate includes providing sealing materials 24A, 24B (resin sealing materials) for forming a sealing portion 3 around a peripheral edge portion of the current collector 11 (S1), irradiating a predetermined portion of the sealing material 24B with laser light to be absorbed by the sealing material 24B to melt the predetermined portion (S3), and welding the predetermined portion of the sealing material 24B to the separator 13 by pressurizing the separator 13 to the melt predetermined portion (S4).SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Japanese Patent Application Laid-Open No. 2023-092421 (Patent Document 1) discloses a battery including an electrode laminate including a current collector and a separator, and a sealing part that seals the electrode laminate. In this battery, the end of the separator is fixed by welding to a resin seal material (sealing part). However, Patent Document 1 does not describe the details of the welding method. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-092421 A Summary of the Invention [Problem to be solved by the invention]

[0004] The contact heating method is known as a method for welding the separator and the resin sealant. However, in the contact heating method, there is a possibility that the heating device (e.g., a hot iron) and the separator may be welded together. The sticking of the heating device may cause quality defects or equipment failures.

[0005] The present disclosure has been made to solve the above problems, and an object of the present disclosure is to suitably weld a resin sealant and a separator without contacting each other. [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 separator, and a sealing portion for sealing the laminate. The method for manufacturing the battery includes providing a resin sealant for forming the sealing portion on a peripheral portion of the current collector, irradiating a predetermined portion of the resin sealant with laser light absorbed by the resin sealant to melt the predetermined portion, and applying pressure to the separator against the predetermined portion in the molten state to weld the predetermined portion of the resin sealant to the separator. Effect of the Invention

[0007] According to the present disclosure, it is possible to suitably weld the resin sealant and the separator without contacting each other. [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] 10A and 10B are diagrams for explaining Examples 1 and 2 relating to a laser irradiation step and a pressure application step. 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 plane view. The negative electrode active material layer 12A is formed in a rectangular shape in an XY plane view at the center on the second surface of the current collector 11. The positive electrode active material layer 12B is formed in a rectangular shape in an XY plane view at the center on the first surface of the current collector 11. In this embodiment, no active material layer is formed on the periphery 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 carbon-based materials (graphite, highly oriented graphite, boron-doped carbon, etc.), metal compounds, and compositions containing elements 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 active material layer 12B is removed from the bipolar electrode 1. The positive terminal electrode 2B has a configuration in which the negative active material layer 12A is removed from the bipolar electrode 1. The separator 13 is formed in a rectangular shape in an XY plane view. 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 adjacent bipolar electrode 1. The separator 13 suppresses short circuits between the positive and negative electrodes. The current collector 11, the negative active material layer 12A, the positive active material layer 12B, and the separator 13 may be disposed so that their axes (centers of gravity) coincide when viewed from the stacking direction.

[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 first sealing layer 14A and the second sealing layer 14B are provided on each current collector 11 and hold the peripheral portion of the corresponding current collector 11. The first sealing layer 14A and the second sealing 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 sealing layer 14B. An electrolyte is filled in the space surrounded by the sealing portion 3 (between the electrode laminate 1a and the sealing portion 3), 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 resistant to the electrolyte is used as the material constituting the sealing portion 3.

[0014] Spacer layer 15 is located between first seal layer 14A and second seal layer 14B in the stacking direction. The outer edge of spacer layer 15 is joined (welded) to the outer edge of each of adjacent first seal layer 14A and second seal layer 14B. By disposing spacer layer 15 between adjacent current collectors 11 in the stacking direction, a gap corresponding to the thickness of spacer layer 15 is maintained between those current collectors 11.

[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 disposed on the bipolar electrode 1. The seal materials 24A and 24B are resin members 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 disposed along the periphery of the current collector 11. The seal materials 24A and 24B are disposed on the -Z side and the +Z side of the current collector 11, respectively. In this embodiment, a metal foil is adopted 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 can be achieved at the same time. In this embodiment, the seal materials 24A and 24B are made of polyethylene. 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, and more preferably 100 μm or more and 150 μm or less. By optimizing the thickness, sufficient adhesion and translucency can be achieved at the same time. Note that the material constituting each seal material is not limited to polyethylene, and may be, for example, polypropylene, acid-modified polyethylene, or acid-modified polypropylene.

[0017] In the next step S2, the first 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 first welding device includes a semiconductor laser as a laser light source. The wavelength of the laser light (hereinafter also referred to as the "first 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 first laser light from the seal material 24B side (+Z side) to the portion where the seal materials 24A and 24B and the current collector 11 overlap in the XY plane view. The irradiation of the first laser light may be performed in a state where the seal materials 24A and 24B are pressed toward the current collector 11. The seal material 24B transmits the first laser light, and the current collector 11 absorbs the first laser light. Then, the energy absorbed by the current collector 11 is converted into heat. As a result, sealants 24A and 24B are heated and melted on the surface of current collector 11, and sealants 24A, 24B are welded to current collector 11. Sealant 24B may transmit the first laser light with a transmittance of, for example, 60% or more.

[0018] In the next step S3, the separator 13 is prepared. Examples of materials constituting the separator 13 include polyethylene, polypropylene, polyolefin, and polyester. Then, before attaching the separator 13 to the seal material 24B, a laser is irradiated to a predetermined portion of the seal material 24B (hereinafter referred to as the "SEP joint portion"). Specifically, the second welding device performs the laser irradiation. The second welding device includes a CO2 laser as a laser light source. The wavelength of the laser light irradiated from the CO2 laser (hereinafter also referred to as the "second laser light") is, for example, 9.4 μm or more and 10.6 μm or less. In S3, the CO2 laser irradiates the SEP joint portion of the seal material 24B with the second laser light, and the seal material 24B absorbs the second laser light. The seal material 24B absorbs the second laser light with, for example, an absorption rate of 20% or more. The energy absorbed by the seal material 24B is converted into heat, and the SEP joint portion melts. The second laser light absorptance of the sealant 24B is preferably 20% to 80%, more preferably 60% to 80%. If the absorptance is too high, the sealant 24B may be damaged. In this embodiment, the laser irradiation is performed on the SEP bonding portion so that the second laser light does not hit the separator 13. This prevents the second laser light from being absorbed by the separator 13 (and thus prevents the separator 13 from being damaged).

[0019] In the next step S4, a pressure device presses the separator 13 against the SEP bonding portion in a molten state. This causes the seal material 24B and the separator 13 to be welded together. The separator 13 may have an HRL (thermal resistance layer) on one of its front and back surfaces (one side). In this case, the side of the separator 13 without the HRL is pressed against the SEP bonding portion of the seal material 24B. This makes it easier to obtain high bonding strength. S3 and S4 will be further described below with reference to FIG. 3.

[0020] FIG. 3 is a diagram for explaining Examples 1 and 2 regarding S3 and S4. Referring to FIG. 3, in both Examples 1 and 2, the second welding device includes a CO2 laser head 200, and the pressure device includes a guide roller 310, a pressure roller 320, and a fixed roller 330. The pressure device is configured to press the separator 13 against the first surface of the seal material 24B while conveying the current collector 11 and the seal materials 24A and 24B by each roller. The guide roller 310 guides the separator 13 to the first surface of the seal material 24B, and the pressure roller 320 presses the separator 13 toward the seal material 24B. The pressure is, for example, 0.1 to 1.0 MPa. The pressure roller 320 and the fixed roller 330 face each other with the laminate of the seal material 24A, the current collector 11, the seal material 24B, and the separator 13 sandwiched therebetween. The pressure roller 320 is driven to rotate, and the fixed roller 330 is driven to rotate, so that the sandwiched laminate is transported to the +Y side at a speed of, for example, 50 to 450 mm / sec. The CO2 laser head 200 applies a laser power density of, for example, 0.1 to 5 W / mm to the transported laminate. 2 The second laser beam is irradiated with a CO2 laser, which can easily heat and melt the surface of the resin film without contact.

[0021] In the first embodiment, the CO2 laser head 200 irradiates the second laser light at an angle d1. The angle d1 is, for example, 5° or more and 60° or less. In the second embodiment, the CO2 laser head 200 irradiates the second laser light at an angle d2. The angle d2 is almost perpendicular to the surface (for example, 70° or more and 90° or less). In both the first and second embodiments, the second welding device irradiates the portion (SEP bonding portion) in front of the pressure unit (pressure roller 320) with a laser. Then, immediately after irradiating the SEP bonding portion with the second laser light, the separator 13 is pressed against the SEP bonding portion (heat melting portion). In the first embodiment, the laser irradiation angle is small. Therefore, the first embodiment can irradiate the laser at a timing closer to pressing than the second embodiment. By shortening the time from laser irradiation (heat melting) to pressing, thermal damage can be suppressed. However, in the second embodiment, the beam spot is almost vertical, so that it is easy to melt the targeted portion by laser irradiation.

[0022] The CO2 laser head 200 may be configured to change the laser irradiation angle. The CO2 laser head 200 may change the laser irradiation angle based on the material and / or thickness of the sealing material 24B. The second welding device may have a plurality of CO2 laser heads 200 with different laser irradiation angles. The pressurizing device may increase the conveying speed as the laser irradiation angle increases. The faster the conveying speed, the shorter the time from laser irradiation to pressurization.

[0023] In this embodiment, the SEP bonding portion is set in a perforated shape (broken line shape). Then, the second welding device performs intermittent irradiation of the second laser light in accordance with the SEP bonding portion. As a result, as shown in FIG. 3, the bonding portion M between the seal material 24B and the separator 13 is formed in a perforated shape. By forming the bonding portion M of the separator 13 in a perforated shape, the fluidity of the liquid (e.g., electrolyte) and / or gas (e.g., gas generated by the reaction of the battery) at the bonding portion M is increased. However, it is not essential to intermittently irradiate the second laser light, and the second laser light may be irradiated continuously.

[0024] 3 shows a method of welding the separator 13 to the sealant 24B located at the +X side edge P1 among the edge portions P1 to P4 of the current collector 11 constituting the bipolar electrode 1. However, the sealants 24A, 24B and the separator 13 are also welded to the other edge portions P2 to P4 of the current collector 11 in the same manner as the edge portion P1. The sealants on the four sides may be joined together. The sealants on the four sides are integrated to form a frame. For example, the sealant 24A at the edge portions P1 to P4 and the sealant 24B at the edge portions P1 to P4 may be integrated to form a frame by end face welding (S6) described later.

[0025] The above-mentioned processes 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 S1 to S3 are also performed for each of the negative terminal electrode 2A and the positive terminal electrode 2B. Furthermore, the process S4 is also performed for the positive terminal electrode 2B.

[0026] 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.

[0027] 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). As a result, the end faces of the peripheral portion of the laminate are welded, and the seal material 24A (first seal layer 14A), the seal material 24B (second seal layer 14B), and the spacer layer 15 are integrated. As a result, the sealing portion 3 is formed, and the energy storage module 10 shown in FIG. 1 is completed. Furthermore, after S6, an overhang portion may be formed in the energy storage module 10 by injection molding. The overhang portion sandwiches the end portion of the energy storage module 10 in the stacking direction. The overhang portion reinforces the peripheral portion of the liquid injection port, enabling stable liquid injection.

[0028] As described above, the manufacturing method of the battery according to this embodiment includes providing the seal materials 24A and 24B (resin seal materials) for forming the sealing portion 3 on the periphery of the current collector 11 (S1), irradiating the SEP joint portion (predetermined portion) of the seal material 24B with a laser beam absorbed by the seal material 24B to melt the SEP joint portion (S3), and pressing the separator 13 against the SEP joint portion in the melted state to weld the SEP joint portion of the seal material 24B and the separator 13 (S4). According to this method, the SEP joint portion can be melted without contact and in a short time. In addition, by pressing the separator 13 against the SEP joint portion immediately after melting the SEP joint portion, the end portion of the separator 13 can be fixed to the seal material 24B located on the periphery of the current collector 11 without directly touching the heat melt portion. According to the above method, the resin seal material (seal material 24B) and the separator 13 can be suitably welded without contact. It is difficult to form a continuous perforated joint using the contact heating method.

[0029] 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.

[0030] 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]

[0031] 1 bipolar electrode, 1a electrode laminate, 3 sealing portion, 10 electricity storage module, 11 current collector, 13 separator, 14A first sealing layer, 14B second sealing layer, 15 spacer layer, 24A, 24B sealing material, M bonding portion, P1 to P4 peripheral portion.

Claims

[Claim 1] A method for producing a battery including a laminate including a current collector and a separator, and a sealing part that seals the laminate, comprising the steps of: providing a resin seal material for forming the sealing portion on a peripheral portion of the current collector; a laser beam absorbed by the resin sealing material is irradiated onto a predetermined portion of the resin sealing material to melt the predetermined portion; applying pressure to the separator in a molten state at the predetermined portion to weld the predetermined portion of the resin seal material to the separator; A method for manufacturing a battery, comprising:

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