Manufacturing method for energy storage modules

Abstract

The separator is welded to the resin component while preventing damage to the separator due to heat input before welding. [Solution] A method for manufacturing an energy storage module includes a preparation step of preparing a strip material comprising a plurality of electrode sheets having electrodes having current collector foil and composite material layers, and resin members provided on the periphery of the current collector foil, wherein the plurality of electrode sheets are connected in a first direction by the resin members; a heating step of heating the resin members by irradiating them with a laser so that the beam shape at the irradiation position becomes elliptical while the strip material is being transported in the first direction; and a pressing step of pressing a separator, which is positioned opposite the strip material so as to cover the electrode sheets, onto the irradiated portion of the resin member that has been irradiated with the laser, thereby heat-welding the separator and the resin member. In the heating step, the laser is continuously irradiated onto the resin member so that the irradiated portion extends along the first direction, and the resin member is heated so that the temperature of the irradiated portion in the pressing step is 129°C or higher and 325°C or lower.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a power storage module.

Background Art

[0002] Patent Document 1 discloses a power storage module including an electrode laminate in which a plurality of electrodes are laminated and a resin member for sealing the electrode laminate, and a structure in which a separator included in the electrode laminate is welded to the resin member. In the configuration described in Patent Document 1, at the time of manufacturing the power storage module, the separator and the resin member are simultaneously heated by a heater, and after heating, the heated separator and resin member are pressed by a roller to thermally weld the separator and the resin member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the separator is thinner than the resin member, it is difficult to control the balance between the heat input to the separator and the heat input to the resin member in the method of simultaneously heating the separator and the resin member as in the configuration described in Patent Document 1. When the heat input to the resin member before welding is insufficient, it is difficult to weld the separator and the resin member. On the other hand, when the heat input to the resin member before welding is excessive, the separator is heated above the heat-resistant temperature, the separator is damaged, and the function of the separator may deteriorate.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a power storage module that can weld a separator to a resin member and prevent damage to the separator due to heat input before welding.

Means for Solving the Problems

[0006] A method for manufacturing an energy storage module according to the present invention includes a preparation step of preparing a strip material in which electrodes including a current collector foil and an asphalt layer are connected in a first direction by a resin member provided on the periphery of the current collector foil; a heating step of irradiating the resin member with a laser while the strip material is being transported in the first direction, and heating the resin member with the laser such that the beam shape at the irradiation position becomes elliptical; and a pressing step of arranging a separator so as to cover the asphalt layer and the resin member, pressing the separator against the irradiated portion of the resin member that has been irradiated with the laser, and heat welding the separator and the resin member, wherein in the heating step, the laser is continuously irradiated onto the resin member so that the irradiated portion extends along the first direction, and the resin member is heated such that the temperature of the irradiated portion in the pressing step is 129°C or higher and 325°C or lower. [Effects of the Invention]

[0007] In this invention, the separator can be welded to the resin member while preventing damage to the separator due to heat input before welding. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing an energy storage module in an embodiment. [Figure 2] This is a schematic diagram showing the strip material. [Figure 3] This is a cross-sectional view showing the section along line AA in Figure 2. [Figure 4] This is a diagram illustrating the welding process. [Figure 5] This is a schematic diagram of a welding device. [Figure 6] This figure shows the relationship between the shear strength of the welded area and the temperature of the irradiated area. [Figure 7] This is a schematic cross-sectional view showing a single-wafer cell subassembly. [Modes for carrying out the invention]

[0009] The following describes in detail the method for manufacturing an energy storage module according to embodiments of the present invention. However, the present invention is not limited to the embodiments described below.

[0010] Figure 1 is a schematic cross-sectional view showing an energy storage module in an embodiment. The energy storage module 1 is included in a battery pack installed in an electric vehicle such as a plug-in hybrid vehicle or an electric vehicle. The energy storage module 1 has a structure in which multiple cells are stacked. The energy storage module 1 is a lithium-ion battery. The battery pack including the energy storage module 1 constitutes a bipolar type battery in which multiple energy storage modules 1 are stacked.

[0011] The energy storage module 1 comprises an electrode stack 2 in which multiple electrodes are stacked, and a sealing part 3 that seals the electrode stack 2.

[0012] The electrode stack 2 has a structure in which multiple bipolar electrodes 10, a positive terminal electrode 20, a negative terminal electrode 30, and multiple separators 40 are stacked.

[0013] The bipolar electrode 10 comprises a current collector foil 11, a positive electrode composite layer 12 provided on one side of the current collector foil 11, and a negative electrode composite layer 13 provided on the other side of the current collector foil 11. The current collector foil 11 is a laminated foil in which aluminum foil and copper foil are bonded together via an adhesive layer. The aluminum foil is the positive electrode substrate, and the copper foil is the negative electrode substrate. The positive electrode composite layer 12 is a positive electrode active material layer formed by coating the current collector foil 11 with a positive electrode composite containing a positive electrode active material. The positive electrode active material includes NCM (ternary positive electrode material) or LFP (lithium iron phosphate). The thickness of the positive electrode composite layer 12 is 0.1 μm or more and 1000 μm or less. The negative electrode composite layer 13 is a negative electrode active material layer formed by coating the current collector foil 11 with a negative electrode composite containing a negative electrode active material. The negative electrode active material includes carbon, silica, etc. The positive electrode composite layer 12 and the negative electrode composite layer 13 are formed as porous materials. The adhesive layer included in the current collector foil 11 is a resin layer that adheres the aluminum foil and the copper foil. The adhesive layer contains epoxy resin. In the current collector foil 11, one side of the aluminum foil is adhered to the copper foil via the adhesive layer, and the positive electrode composite layer 12 is provided on the other side of the aluminum foil. The other side of the aluminum foil includes an uncoated area. This uncoated area is a region where the positive electrode composite layer 12 is not provided and is located at the periphery of the aluminum foil. The periphery of the aluminum foil is the periphery of the current collector foil 11 and the periphery of the electrode laminate 2. In the current collector foil 11, one side of the copper foil is adhered to the aluminum foil via the adhesive layer, and the negative electrode composite layer 13 is provided on the other side of the copper foil. The other side of the copper foil includes an uncoated area. This uncoated area is a region where the negative electrode composite layer 13 is not provided and is located at the periphery of the copper foil. The peripheral edge of the copper foil is the peripheral edge of the current collector foil 11 and the peripheral edge of the electrode laminate 2.

[0014] The positive electrode terminal electrode 20 comprises a terminal positive electrode foil 21 and a terminal positive electrode composite material layer 22 provided on one side of the terminal positive electrode foil 21. The terminal positive electrode foil 21 is a current collector foil formed in the shape of a rectangular sheet and is made of aluminum foil. The terminal positive electrode composite material layer 22 is a positive electrode active material layer formed by coating the terminal positive electrode foil 21 with a positive electrode composite material similar to that of the positive electrode composite material layer 12.

[0015] The negative terminal electrode 30 has a terminal negative electrode foil 31 and a terminal negative electrode composite layer 32 provided on one surface of the terminal negative electrode foil 31. The terminal negative electrode foil 31 is a current collector foil formed in a rectangular sheet shape and is composed of a copper foil. The terminal negative electrode composite layer 32 is a negative electrode active material layer formed by coating the same negative electrode composite material as the negative electrode composite layer 13 on the terminal negative electrode foil 31. When the positive electrode composite layer 12, the negative electrode composite layer 13, the terminal positive electrode composite layer 22, and the terminal negative electrode composite layer 32 are not particularly distinguished, they may be described as composite layers.

[0016] Between the positive terminal electrode 20 and the negative terminal electrode 30, the bipolar electrodes 10 and the separator 40 are alternately laminated. Between the bipolar electrodes 10 adjacent to each other in the lamination direction, the positive electrode composite layer 12 of one bipolar electrode 10 is laminated with the negative electrode composite layer 13 of the other bipolar electrode 10 with the separator 40 interposed therebetween.

[0017] The sealing portion 3 is an insulating resin member and forms the frame of the power storage module 1. The sealing portion 3 is provided at the peripheral portion of the electrode laminate 2 and is arranged so as not to touch the composite layer. That is, the sealing portion 3 is provided at the peripheral portion of the current collector foil 11 and is arranged so as not to touch the positive electrode composite layer 12 and the negative electrode composite layer 13. Further, the sealing portion 3 is provided at the peripheral portion of the terminal positive electrode foil 21 and is arranged so as not to touch the terminal positive electrode composite layer 22. Similarly, the sealing portion 3 is provided at the peripheral portion of the terminal negative electrode foil 31 and is arranged so as not to touch the terminal negative electrode composite layer �2.

[0018] The sealing portion 3 is composed of an insulating resin. The sealing portion 3 is composed of polypropylene, polyethylene, polyphenylene sulfide, polystyrene, etc. For example, the sealing portion 3 is composed of a composite of polypropylene, polyethylene, and polyphenylene sulfide. The power storage module 1 has a structure in which the peripheral portion of the current collector foil <11> is laminated with a plurality of resins.

[0019] The sealing portion 3 includes a primary seal 51 and a spacer 52. The primary seal 51 is a frame-shaped resin member provided at the peripheral portion of the current collector foil 11 and is welded to the peripheral portion of the current collector foil 11. The primary seal 51 is formed by laminating a plurality of seal members on the peripheral portion of the current collector foil 11. The spacer 52 is a frame-shaped resin member laminated on the primary seal 51 and is welded to the primary seal 51. The spacer 52 is interposed between adjacent primary seals 51 in the lamination direction.

[0020] In the power storage module 1, the separator 40 is welded to the primary seal 51. The separator 40 is disposed so as to cover the positive electrode composite layer 12, and the peripheral portion of the separator 40 is welded to the primary seal 51. The separator 40 is a porous membrane. The separator 40 is made of a resin such as polyethylene. The thickness of the separator 40 is 0.1 μm or more and 1000 μm or less.

[0021] In the power storage module 1 configured as described above, in order to prevent a short circuit of the battery, it is necessary to ensure that the welded portion of the separator 40 and the primary seal 51 satisfies the welding quality. Since the manufacturing method of the power storage module in the prior art includes a step of simultaneously heating the separator and the resin member before welding, the separator may be damaged due to the heat input to the separator before welding. Therefore, the manufacturing method of the power storage module 1 in the embodiment includes a step of heating only the primary seal 51 without heating the separator 40 before welding. Further, the manufacturing method of the power storage module 1 in the embodiment uses a laser for heating the primary seal 51, and assumes that the beam shape on the primary seal 51 becomes an elliptical shape when the laser is irradiated on the primary seal 51. That is, the manufacturing method of the power storage module 1 determines the welding conditions that satisfy the desired welding quality even when the beam shape at the irradiation portion is not a perfect circle but an elliptical shape.

[0022] The manufacturing method of the power storage module 1 in the embodiment includes a preparation step of preparing the strip 4, a welding step of welding the separator 40 to the strip 4, and a lamination step of laminating the leaf-shaped member including the separator 40.

[0023] As shown in Figure 2, the strip material 4 is a component in which electrodes including a current collector foil 11 and an asphalt mixture layer are connected in a first direction by a primary seal 51 provided on the periphery of the current collector foil 11. As shown in Figure 3, the strip material 4 has a current collector foil 11, a positive electrode asphalt mixture layer 12 provided on one side of the current collector foil 11, a negative electrode asphalt mixture layer 13 provided on the other side of the current collector foil 11, and a primary seal 51 provided on the periphery of the current collector foil 11. The strip material 4 is manufactured by applying the positive electrode asphalt mixture and the negative electrode asphalt mixture to both sides of the current collector foil 11, and then welding the primary seal 51 to the periphery of the current collector foil 11. The periphery of the current collector foil 11 is covered all around by the primary seal 51. The primary seal 51 extends beyond the periphery of the current collector foil 11.

[0024] The welding process, as shown in Figure 4, is a process of welding the separator 40 to the primary seal 51 of the strip material 4. In the welding process, the primary seal 51 of the strip material 4 is heated by a laser 5, and the separator 40 is heat-welded to the heated primary seal 51. The irradiation position 6 to which the laser 5 is irradiated corresponds to the position of the primary seal 51 covering the peripheral edge of the current collector foil 11.

[0025] The welding process is performed using a welding device 60, as shown in Figure 5. The welding device 60 comprises a first conveyor roll 61, a second conveyor roll 62, a laser head 63, a mirror 64, a pressurizing mechanism 65, and a feed roll 66. The first conveyor roll 61 is the upstream roll, and the second conveyor roll 62 is the downstream roll. The first conveyor roll 61 and the second conveyor roll 62 apply tension to the strip material 4 between them and convey the strip material 4 in the conveying direction. In this description, the conveying direction of the strip material 4 between the first conveyor roll 61 and the second conveyor roll 62 may be simply referred to as the conveying direction.

[0026] The welding process involves irradiating the strip material 4 being transported between the first transport roll 61 and the second transport roll 62 with a laser 5 to heat the primary seal 51, and then pressing the separator 40 onto the heated primary seal 51 to heat-weld the separator 40 and the primary seal 51. The welding process includes a heating step of heating the primary seal 51 with the laser 5 as it passes the irradiation position 6, a supply step of supplying the separator 40 to the processing point with the strip material 4, and a pressing step of pressing the separator 40 onto the strip material 4 at the processing point to weld the separator 40 and the primary seal 51 together.

[0027] The heating process involves irradiating the primary seal 51 with a laser 5 while the strip material 4 is being transported in a first direction, and heating the primary seal 51 with the laser 5 so that the beam shape at the irradiation position 6 becomes elliptical. In the heating process, the temperature of the primary seal 51 in the irradiated portion is increased. In the heating process, the laser 5 is continuously irradiated with the primary seal 51 so that the irradiated portion extends along the first direction, and the primary seal 51 is heated so that the temperature of the irradiated portion in the pressing process is between 129°C and 325°C.

[0028] As shown in Figure 4, a pair of laser heads 63 and mirrors 64 are provided on both sides of the strip material 4 in the width direction. The laser head 63 irradiates the mirror 64 with a laser 5. As shown in Figure 5, the laser head 63 and mirror 64 are positioned upstream of the feed roll 66 in the transport direction. The mirror 64 reflects the laser 5 from the laser head 63 and irradiates the irradiation position 6 with the laser 5. The irradiation position 6 is directly in front of the second transport roll 62 and the pressurizing mechanism 65 in the transport direction. The pressurizing mechanism 65 is provided at a position corresponding to the irradiation area. A pair of pressurizing mechanisms 65 are provided on both sides in the width direction of the strip material 4. The pressurizing mechanism 65 presses the edge of the separator 40 against the primary seal 51 of the strip material 4. The pressurizing mechanism 65 includes an elastic roll. The elastic roll is positioned above the second transport roll 62. The feed roll 66 is positioned between the first transport roll 61 and the second transport roll 62 in the transport direction and feeds out the separator 40. The irradiation position 6 is located upstream of the pressurizing mechanism 65 and the second conveying roll 62, and downstream of the feed roll 66, in the conveying direction.

[0029] In the heating process, a laser 5 is irradiated from a laser head 63 positioned upstream of the feed roll 66 toward an irradiation position 6 set downstream of the feed roll 66. Since the strip material 4 is being transported in the first direction even during irradiation, the irradiated portion where the laser 5 is irradiated in an elliptical shape at the irradiation position 6 extends linearly along the first direction. This irradiated portion is heated so that its temperature during the pressing process is between 129°C and 325°C. As shown in Figure 6, when the temperature of the irradiated portion is between 129°C and 325°C, the shear strength of the welded portion becomes 1 or more. When the shear strength of the welded portion between the separator 40 and the primary seal 51 is 1 or more, the welding quality between the separator 40 and the primary seal 51 satisfies the conditions for good quality. For good quality welding, it is more preferable that the temperature of the irradiated portion is between 170°C and 250°C. Note that the peak temperature shown in Figure 6 represents the temperature of the primary seal 51 at the processing point.

[0030] Laser 5 is a CO2 laser. Laser 5 is irradiated onto the primary seal 51 via a mirror 64 from the laser head 63. The laser wavelength is 9 μm or more and 11 μm or less. The beam diameter in the irradiated area is 1 mm or more and 10 mm or less. The laser output is 100 W or more and 150 W or less. The laser head 63 is installed upstream of the feed roll 66 and the pressurizing mechanism 65 in the transport direction.

[0031] The supply process involves feeding the separator 40, which has been fed out from the feed roll 66, to the processing point with the strip material 4, positioning it so as to face the irradiated portion of the primary seal 51. The processing point is the portion where the separator 40 and the strip material 4 are sandwiched between the pressurizing mechanism 65 and the second transport roll 62. In the supply process, tension is applied to the separator 40 from the feed roll 66 as it is fed towards the processing point.

[0032] The pressing process involves pressing the separator 40 against the irradiated portion of the primary seal 51 using a pressurizing mechanism 65 as the strip material 4 passes through the second conveyor roll 62, thereby heat-welding the separator 40 and the primary seal 51. The pressing process includes pressing the separator 40 against the primary seal 51 of the strip material 4 so as to sandwich the irradiated portion at the processing point. The separator 40, fed out from the feed roll 66, is positioned above the strip material 4 at the processing point and is pressed by the pressurizing mechanism 65.

[0033] After the welding process, the primary seal 51 is cut to form the cell subassembly 7, as shown by the dashed line in Figure 4. As shown in Figure 7, the cell subassembly 7 is a single-sheet-shaped member containing a separator 40 and a bipolar electrode 10.

[0034] The lamination process involves stacking multiple cell subassemblies 7 together with spacers 52. The lamination process is the process of manufacturing the electrode laminate 2.

[0035] As described above, according to the embodiment, the laser 5 is irradiated onto the primary seal 51 such that the beam shape at the irradiation position 6 is elliptical, heating only the primary seal 51 and allowing the separator 40 to be heat-welded to the primary seal 51. Since only the primary seal 51 is heated during the heating process, damage to the separator 40 by the heat of the laser 5 can be prevented. This ensures that the welding quality between the separator 40 and the primary seal 51 is met.

[0036] Note that laser 5 is not limited to gaseous lasers such as CO2 lasers, but may also be solid-state lasers such as YAG lasers.

[0037] Furthermore, the number of mirrors 64 is not particularly limited. For example, the laser 5 may be irradiated directly onto the primary seal 51 from the laser head 63 without any mirrors 64. Alternatively, multiple mirrors 62 may be provided, and the laser 5 may be irradiated onto the primary seal 51 from the laser head 63 via the multiple mirrors 62.

[0038] Furthermore, the strip material 4 may be any component that includes at least a positive electrode composite layer as an composite layer. The strip material 4 may be a component for forming the bipolar electrode 10, or a component for forming the positive electrode terminal electrode 20. The strip material 4 may have a structure in which a plurality of terminal positive electrode foils 21 coated with positive electrode composite material are connected by a primary seal 51. In other words, the welding process can be applied not only when manufacturing the bipolar electrode 10, but also when manufacturing the positive electrode terminal electrode 20. [Explanation of Symbols]

[0039] 1. Energy storage module 2-electrode stack 3. Sealing part 4 Strip material 5 lasers 6 Irradiation position 7 Cell sub-assembly 10 bipolar electrodes 11 Current collector foil 12. Positive electrode composite layer 13 Negative electrode composite layer 40 Separators

Claims

1. A preparation step of preparing a strip material in which electrodes including a current collector foil and an asphalt layer are connected in a first direction by a resin member provided on the periphery of the current collector foil, A heating step in which, while the strip material is being transported in the first direction, a laser is irradiated onto the resin member, and the resin member is heated by the laser such that the beam shape at the irradiation position becomes elliptical, A pressing step is performed in which a separator is placed so as to cover the composite layer and the resin member, the separator is pressed against the irradiated portion of the resin member that has been irradiated with the laser, and the separator and the resin member are heat-welded together. Includes, In the heating step, the laser is continuously irradiated onto the resin member so that the irradiation portion extends along the first direction, and the resin member is heated so that the temperature of the irradiation portion in the pressing step is 129°C or higher and 325°C or lower. A method for manufacturing an energy storage module, characterized by the following:

2. The supply process includes arranging the separator, which has been fed out from the feed roll, so as to face the irradiation portion and supplying it to the processing point with the strip material, The pressing step includes pressing the separator against the strip material so as to sandwich the irradiated portion at the processing point, The irradiation position is located downstream of the feed roll in the conveying direction of the strip material. A method for manufacturing an energy storage module according to claim 1.

3. The heating step includes irradiating the laser from a position upstream of the feed roll in the transport direction toward the irradiation position. The method for manufacturing an energy storage module according to claim 2.

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