A laser welding system, a laser welding method, a battery production apparatus, and a battery

Abstract

The application discloses a laser welding system, a laser welding method, a battery production device and a battery. The laser welding system is used for hot melt welding of a plurality of layers of separators wound on the outer side of a battery cell and comprises a laser for emitting a laser beam; and a light spot homogenizing device for homogenizing the laser beam to obtain a flat-top light spot. The flat-top light spot acts on the surface of the plurality of layers of separators to hot melt weld the plurality of layers of separators into one body. The laser welding system provided by the application innovatively applies laser welding to the connection and fixation of the plurality of layers of separators on the outer side of the battery cell. The laser welding system discards the adhesive tape fixation method, and does not need to perform the adhesive tape pasting operation on a plurality of positions of the separators, thereby greatly improving the production efficiency. Meanwhile, the application achieves the integrated bonding effect of the plurality of layers of separators, solves the problem that a plurality of layers of separators between the outermost separator and the battery cell cannot be fixed, and the plurality of layers of separators are fixed firmly during the transfer of the battery cell and cannot be loosened and misaligned.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically to a laser welding system, a laser welding method applicable to the laser welding system, a battery production equipment including the laser welding system, and a battery. Background Technology

[0002] In lithium battery manufacturing, the important function of the separator is to separate the positive and negative electrodes while allowing electrolyte ions to pass through. After the cell stacking or winding process is completed, several layers of separator need to be wound around the outside of the cell to protect it.

[0003] In existing technologies, the multilayer separators wound around the outside of the battery cell are fixed with tape at multiple locations on the outermost separator. However, this method only fixes the outermost separator, leaving the separator layers between the outermost separator and the battery cell unfixed. These unfixed separator layers are prone to loosening and misalignment during battery cell transport. Furthermore, the tape fixing method requires applying tape to multiple locations on the separator, resulting in low production efficiency. Summary of the Invention

[0004] In view of this, this application provides a laser welding system, a laser welding method applicable to the laser welding system, a battery production device including the laser welding system, and a battery that solves the problem that the outermost separator in the multilayer separator wound around the cell cannot be bonded and fixed to the cell, and the problem that multiple positions of the separator layer need to be covered with tape, resulting in low production efficiency.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] A laser welding system for thermally welding a multilayer separator wound around the outside of a battery cell, comprising:

[0007] A laser emits a laser beam;

[0008] A beam homogenization device homogenizes the laser beam to obtain a flat-top beam spot;

[0009] The flat-top light spot acts on the surface of the multilayer diaphragm to heat-melt and weld the multilayer diaphragm into a single unit.

[0010] Optionally, the laser welding system described above also includes a clamping device; the clamping device is placed on the part of the multilayer diaphragm to be welded to press and adhere the multilayer diaphragm at the part to be welded.

[0011] The flat top spot acts on the multilayer diaphragm of the to-be-welded part through the pressing device.

[0012] Optionally, the laser welding system further comprises a scanning galvanometer module; the scanning galvanometer module is formed with a working field;

[0013] The scanning galvanometer module can focus the flat top spot and move the focused flat top spot in the working field to adjust the position of the focused flat top spot on the surface of the multilayer diaphragm.

[0014] Optionally, the laser welding system further comprises a dust removal device; the dust removal device can clean the impurities generated in the hot melt welding process.

[0015] Optionally, the laser welding system further comprises a dust removal device; the dust removal device can clean the impurities generated in the hot melt welding process.

[0016] The moving speed of the focused flat top spot in the working field is 1 m / s-50 m / s.

[0017] The scanning galvanometer module comprises a field lens; the focal length of the field lens is 300 mm-350 mm; the length of the working field is 180 mm-220 mm, and the width is 180 mm-220 mm.

[0018] Optionally, the laser welding system further comprises a dust removal device; the dust removal device can clean the impurities generated in the hot melt welding process.

[0019] Optionally, the laser welding system further comprises a dust removal device; the dust removal device can clean the impurities generated in the hot melt welding process.

[0020] The output power of the semiconductor laser is 25 W-35 W.

[0021] The wavelength range of the laser beam emitted by the semiconductor laser is 300 nm-600 nm.

[0022] Optionally, the laser welding system further comprises a dust removal device; the dust removal device can clean the impurities generated in the hot melt welding process.

[0023] A laser welding method suitable for the laser welding system described above; the laser welding method comprises:

[0024] Place the battery cell with the multilayer diaphragm wound outside to the working position;

[0025] Control the laser to emit a laser beam, and the laser beam obtains a flat top spot after passing through the spot homogenization device, and the flat top spot acts on the surface of the multilayer diaphragm outside the battery cell to hot melt and weld the multilayer diaphragm into one.

[0026] Optionally, in the laser welding method, the flat-top light spot acts on the surface of the unit area of the multi-layer separator for 0.08-0.12 seconds.

[0027] Optionally, in the laser welding method,

[0028] The multi-layer separator has a plurality of welding sites; the laser and the light spot homogenization device are moved in sequence so that the flat-top light spot acts on the plurality of welding sites in sequence.

[0029] Or,

[0030] The multi-layer separator has a plurality of welding sites; the laser and the light spot homogenization device are moved in sequence so that the flat-top light spot acts on the plurality of welding sites in sequence.

[0031] Or,

[0032] The multi-layer separator has a plurality of welding sites; the position of the flat-top light spot is adjusted by a scanning galvanometer module so that the flat-top light spot acts on the plurality of welding sites in sequence.

[0033] A battery production device comprising the laser welding system described above.

[0034] A battery comprising a battery cell and a multi-layer separator wound outside the battery cell, the multi-layer separator being an integral structure formed by laser heat fusion welding.

[0035] Optionally, in the battery, an auxiliary welding layer is arranged on the surface of the separator.

[0036] In the laser welding system, the laser welding method, the battery production device and the battery provided by the present application, the laser welding is innovatively applied to the connection and fixation of the multi-layer separator outside the battery cell, which discards the adhesive tape fixation method and eliminates the need for pasting adhesive tapes at multiple positions of the separator, thereby greatly improving the production efficiency. Meanwhile, the present application realizes the integral bonding effect of the multi-layer separator and solves the problem that the several layers of separators between the outermost separator and the battery cell cannot be fixed, so that the multi-layer separator is fixed firmly during the transfer of the battery cell and cannot be loosened or misaligned. Further, the present application uses a light spot homogenization device to homogenize the laser beam emitted by the laser, and obtains a flat-top light spot. When the flat-top light spot is used for heat fusion welding, the heat source is uniformly distributed, the size and shape of the welding seam change little during the heat fusion welding process, the welding quality is stable, and only the multi-layer separator outside the battery cell is heat fused during the heat fusion welding, without affecting the structure of the battery cell itself. BRIEF DESCRIPTION OF DRAWINGS

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Fig. 1 The battery cell of this application is wound with multiple layers of separators;

[0039] Fig. 2 Here is a schematic diagram of the diaphragm structure of this application:

[0040] Fig. 3 This is a schematic diagram of the laser welding system of this application.

[0041] 1-Laser, 2-Spot homogenization device, 3-Pressure device, 4-Scanning galvanometer module, 5-Dust removal device, 6-Battery cell, 7-Diaphragm;

[0042] 71-Ceramic layer, 72-PE layer, 73-Auxiliary welding layer. Detailed Implementation

[0043] This application provides a laser welding system, a laser welding method applicable to the laser welding system, a battery production apparatus including the laser welding system, and a battery.

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] The semiconductor lasers involved in this application specifically refer to lasers that use semiconductor materials as the working substance and have an output power of 5W-500W and an emitted laser beam wavelength range of 200nm-11000nm.

[0046] like Figs. 1-3 As shown, a laser welding system is used for thermally melting welding of a multilayer separator 7 wound around the outside of a battery cell 6. The laser welding system includes a laser 1 and a beam homogenization device 2. The laser 1 emits a laser beam. The beam homogenization device 2 homogenizes the laser beam to obtain a flat-top beam. The flat-top beam acts on the surface of the multilayer separator 7 to thermally melt and weld the multilayer separator 7 into a single unit.

[0047] It should be noted that the multi-layer separator 7 wound on the outer side of the battery cell 6 has several welding sites; along the winding direction of the separator 7, the several welding sites can be continuous or arranged at intervals.

[0048] It should be further noted that the heat fusion welding into one refers to that each layer of the multi-layer separator 7 is in a molten state under the irradiation of the laser beam, and the molten multi-layer separator 7 is finally solidified into an integrated structure after the laser beam stops irradiating. The laser beam irradiation only makes each layer of the separator 7 in a molten state, without affecting the structure of the battery cell 6 itself.

[0049] The flat-top light spot refers to that the light spot of the laser beam acting on the welding site is a planar light spot, and the planar light spot is parallel to the surface of the multi-layer separator of the welding site.

[0050] The light spot homogenization device 2 is a light spot homogenization device that can be purchased in the market, or is artificially formed by one or more required optical lenses (such as collimating mirrors, light homogenization mirrors, light splitting mirrors, focusing mirrors, etc.) according to actual parameter requirements, which is not limited here and will not be described again. The light spot homogenization device is composed of multiple lenses, which can homogenize the laser beam irradiated thereon to obtain a flat-top light spot.

[0051] The application innovatively applies laser welding to the connection and fixation of the multi-layer separator 7 on the outer side of the battery cell 6, which discards the adhesive tape fixation method, eliminates the need for pasting adhesive tape at multiple positions of the separator 7, and greatly improves the production efficiency; at the same time, the application achieves the integrated bonding effect of the multi-layer separator 7, the multi-layer separator 7 is heat fusion welded into one, solves the problem that several layers of separators between the outermost separator of the multi-layer separator 7 and the battery cell 6 cannot be fixed, and the multi-layer separator 7 is fixed firmly during the transfer process of the battery cell 6 and will not be loose and misaligned. Further, the application uses the light spot homogenization device 2 to homogenize the laser beam emitted by the laser 1 and obtains a flat-top light spot; the heat source is uniformly distributed when using the flat-top light spot for heat fusion welding, the size and shape of the weld change little during the heat fusion welding process, the welding quality is stable, and only the multi-layer separator 7 on the outer side of the battery cell 6 is heat fused during the heat fusion welding, without affecting the structure of the battery cell 6 itself.

[0052] In some embodiments of the application, the laser 1 is a semiconductor laser.

[0053] Further, the semiconductor laser can be continuous or pulsed output.

[0054] The semiconductor laser has small structural size, can be flexibly installed in a production line of a battery production device, and meets the batch processing and production requirements of the battery.

[0055] In some embodiments of the present application, the output power of the semiconductor laser is 25W-35W; the wavelength of the laser beam emitted by the semiconductor laser is 300nm-600nm; and the time for the flat-top spot to act on the surface of the unit area of the multilayer separator is 0.08s-0.12s.

[0056] Preferably, the time for the flat-top spot to act on the surface of the unit area of the multilayer separator is 0.1s.

[0057] By precisely limiting the above parameters of the semiconductor laser, the depth of the separator molten pool can be controlled in the micron level, the multilayer separator 7 is prevented from being welded through, and the structure of the battery itself is not damaged, thereby effectively ensuring the welding precision and quality of the multilayer separator 7 and ensuring the performance of the battery.

[0058] Further, the flat-top spot is a rectangular flat-top spot. The length of the rectangular flat-top spot is 15mm-25mm, and the width is 8mm-12mm.

[0059] Preferably, the length of the rectangular flat-top spot is 20mm, and the width is 10mm.

[0060] The size of the flat-top spot in the above size range can ensure the size of the welding seam and ensure the welding effect. Further, when the flat-top spot is moved by the scanning galvanometer module 4, the size of the flat-top spot is adapted to the entrance aperture of the scanning galvanometer module 4.

[0061] In some embodiments of the present application, the laser welding system further comprises a pressing device 3. The pressing device 3 is placed at the to-be-welded part of the multilayer separator 7 to press and adhere the multilayer separator 7 at the to-be-welded part. The flat-top spot passes through the pressing device 3 and acts on the multilayer separator 7 at the to-be-welded part.

[0062] By setting the light-transmitting pressing device 3, the multilayer separator 7 at the to-be-welded part can be pressed and adhered together, the gap between the layers is reduced, and the best hot melt welding effect can be ensured to improve the welding quality.

[0063] It should be noted that the pressing device 3 is made of a material with high laser transmittance; for example, the pressing device 3 is a transparent quartz pressing block.

[0064] In some embodiments of the present application, the laser welding system further comprises a scanning galvanometer module 4. The scanning galvanometer module 4 is formed with a working field. The scanning galvanometer module 4 can focus the flat-top spot and move the focused flat-top spot in the working field to adjust the position of the focused flat-top spot on the surface of the multi-layer separator 7.

[0065] It should be noted that the scanning galvanometer module 4 is a commercially available scanning galvanometer.

[0066] The focusing effect of the flat-top spot is achieved by setting the scanning galvanometer module 4, and the focusing power of the focused flat-top spot is 2-3 times that of the original flat-top spot. The welding effect of the focused flat-top spot on the multi-layer separator 7 of the welding site is better. The flat-top spot enters the light entrance aperture of the scanning galvanometer module 4, and under the adjustment of the angle change of the scanning lens of the scanning galvanometer module 4, the movement of the focused flat-top spot in the working field is realized, which changes the position of the flat-top spot on the surface of the multi-layer separator 7, and then realizes the automatic and accurate switching of the welding site, and the hot melt welding work is more flexible and convenient, the accuracy of the welding position is improved, and the long-time operation of the entire laser welding system is more stable and reliable.

[0067] In some embodiments of the present application, the moving speed of the focused flat-top spot in the working field is 1-50 m / s.

[0068] The above moving speed is set to ensure the working efficiency, accurately control the time when the focused flat-top spot acts on the surface of the multi-layer separator 7 of the welding site, and control the above time to be 0.1 s. As set above, the depth of the separator molten pool is controlled to be in the micron level, preventing the multi-layer separator 7 from being welded through and not damaging the structure of the battery itself, ensuring the welding precision and quality of the multi-layer separator 7, and ensuring the battery performance.

[0069] Further, the scanning galvanometer module 4 comprises a field lens; the focal length of the field lens is 300-350 mm; the length of the working field is 180-220 mm, and the width is 180-220 mm.

[0070] The focal length of the above field lens can ensure that the flat-top spot reaches a focusing power of 2-3 times, and can ensure that the multiple welding sites of the multi-layer separator 7 of the battery are covered by the working field of the above size. By controlling the focal length of the field lens of the scanning galvanometer module 4, the focusing effect of the flat-top spot is adjusted, and the size of the working field is adjusted, thereby meeting the needs of hot melt welding.

[0071] It should be noted that the larger the focal length of the field lens, the larger the working field, and the focusing effect of the flat-top spot is weakened.

[0072] According to the size of the battery cell, select the field lens with appropriate focal length. For example, for the conventional square aluminum shell battery, we select the field lens with focal length of 330 mm, and the working field has length of 200 mm and width of 200 mm.

[0073] It should be further pointed out that the field lens is a telecentric field lens. The above arrangement is conducive to controlling the welding precision of the multi-layer diaphragm 7.

[0074] In summary, the application also provides a laser welding method. The laser welding method is suitable for the welding system described above. Specifically, the welding method comprises:

[0075] S1: placing the battery cell 6 with the multi-layer diaphragm 7 wound outside on the welding platform of the working position;

[0076] S2: placing the pressing device 3 on the to-be-welded part of the multi-layer diaphragm 7 to press and adhere the multi-layer diaphragm 7 of the to-be-welded part;

[0077] S3: controlling the semiconductor laser to output a laser beam, and the laser beam obtains a flat-top spot after passing through the spot homogenization device 2;

[0078] S4: the flat-top spot acts on the multi-layer diaphragm 7 of the to-be-welded part through the pressing device 3 to heat and melt the multi-layer diaphragm 7 of the to-be-welded part to be integrated.

[0079] It should be noted that the output power of the semiconductor laser is 25W-35W; the wavelength range of the laser beam emitted by the semiconductor laser is 300nm-600nm; the flat-top spot is a rectangular flat-top spot; the length of the rectangular flat-top spot is 15mm-25mm, and the width is 8mm-12mm; the action time of the flat-top spot on the surface of the multi-layer diaphragm per unit area is 0.08s-0.12s.

[0080] Since the laser welding method of the application is suitable for the laser welding system described above, the beneficial effects of the laser welding method brought by the laser welding system are described above and will not be repeated here.

[0081] It should be noted that when the battery cell is placed on the welding platform of the working position, the multi-layer diaphragm on the side of the battery cell away from the welding platform has a plurality of to-be-welded parts, and the plurality of to-be-welded parts on the side of the battery cell are respectively heat-melted. Turn over the battery cell to heat-melt the plurality of to-be-welded parts on different sides of the battery cell respectively.

[0082] The laser welding system can not be provided with a scanning galvanometer module 4, or can be provided with a scanning galvanometer module 4. Specifically,

[0083] When the laser welding system does not set the scanning galvanometer module 4:

[0084] The position of the semiconductor laser and the beam homogenization device 2 is fixed, so the irradiation position of the flat-top beam is unchanged; by moving the position of the battery cell, the multiple welding positions of the multilayer separator 7 are sequentially placed in the position opposite to the flat-top beam;

[0085] Or,

[0086] The position of the battery cell placed on the welding platform is fixed; by moving the position of the semiconductor laser and the beam homogenization device 2, the position of the flat-top beam is changed, and the flat-top beam acts on different welding positions of the multilayer separator 7.

[0087] When the laser welding system is provided with the scanning galvanometer module 4:

[0088] The position of the focused flat-top beam is adjusted by the scanning galvanometer module 4 so that the focused flat-top beam acts on different welding positions of the multilayer separator 7 in sequence.

[0089] The scanning galvanometer module 4 includes a field lens; the focal length of the field lens is 300mm-350mm; the length of the working field is 180mm-220mm, and the width is 180mm-220mm; the moving speed of the focused flat-top beam in the working field by the scanning galvanometer module 4 is 1m\s-50m\s.

[0090] In summary, the application also provides a battery production equipment; the battery production equipment includes the laser welding system described above.

[0091] Since the battery production equipment of the application has the laser welding system described above, the beneficial effects of the battery production equipment brought by the laser welding system are described above, and will not be repeated here.

[0092] In summary, the application also provides a battery; the battery includes a battery cell 6 and a multilayer separator 7 wound outside the battery cell 6, and the multilayer separator 7 is an integrated structure formed by laser hot melting welding.

[0093] Further, the multilayer separator 7 is hot-melt welded into an integrated structure by a semiconductor laser.

[0094] Since the multilayer separator 7 wound outside the battery cell 6 in the battery of the application is an integrated structure formed by laser hot melting welding, and the laser welding system of the application hot-melt welds the multilayer separator 7 wound outside the battery cell 6 into an integrated structure by a laser beam, the beneficial effects of the integrated structure of the multilayer separator 7 in the battery of the application formed by laser hot melting welding are described above, and will not be repeated here.

[0095] In some embodiments of the application, the surface of the separator 7 is provided with an auxiliary welding layer 73.

[0096] It should be noted that the diaphragm 7 can be a conventional diaphragm or a composite diaphragm.

[0097] The conventional diaphragm has a PE layer or a PP layer as a substrate, and a ceramic layer coated on one surface of the PE layer or the PP layer. The ceramic layer is an aluminum oxide ceramic. An auxiliary welding layer 73 is arranged on the surface of the PE layer or the PP layer away from the ceramic layer.

[0098] Please refer to the accompanying drawings Fig. 2 The composite diaphragm includes a ceramic layer 71, a PE layer 72, and an auxiliary welding layer 73. The PE layer 72 is arranged on the upper and lower surfaces of the ceramic layer 71 respectively, and the auxiliary welding layer 73 is arranged on the PE layer 72 on the upper surface of the ceramic layer 71.

[0099] Further, the PE layer 72 in the composite diaphragm can be replaced by a PP layer.

[0100] It should be noted that the auxiliary welding layer 73 is a hot melt coating layer coated on the PE layer 72, or a hot melt adhesive tape adhered to the PE layer 72. The material of the hot melt coating layer or the hot melt adhesive tape is PET (polyethylene terephthalate) or the like, and the melting temperature is above 98℃. The thickness of the diaphragm 7 is generally several microns.

[0101] The components and devices involved in the present application are only illustrative examples and are not intended to require or imply that the connection, arrangement, configuration must be as shown in the drawings. As those skilled in the art will recognize, these components and devices can be connected, arranged, configured in any manner. Words such as "include", "contain", "have" and the like are open-ended words, mean "including but not limited to", and can be used interchangeably. The words "or" and "and" used herein mean the word "and / or", and can be used interchangeably unless the context clearly indicates otherwise. The word "such as" used herein means the phrase "such as but not limited to", and can be used interchangeably.

[0102] It should also be noted that in the device of the present application, each component can be disassembled and / or reassembled. These disassembly and / or reassembly should be considered as equivalent solutions of the present application.

[0103] The above description of the disclosed aspects is provided so that any person skilled in the art can make or use the present application. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0104] The foregoing description has been presented for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of the application to the forms disclosed herein. Although various example aspects and embodiments have been discussed above, those of ordinary skill in the art will appreciate a variety of modifications, alternatives, permutations, additions, and sub-combinations, which fall within the scope of the application.

[0105] The above description is merely illustrative of the application, and is not intended to limit the scope of the application that is defined by the appended claims. Rather, the description provided herein describes in an illustrative manner the embodiments of the application that are recommended for patent protection. Other embodiments or examples that fall within the scope of the application are possible and are contemplated by the applicant or inventor, but not necessarily recited in the claims. Therefore, no limitation is placed on the scope of the application by this description or by the drawings.

Claims

1. A laser welding method characterized by, The application relates to a laser welding method and a laser welding system. The method comprises the following steps: placing a battery cell with a plurality of layers of diaphragms wrapped outside into a working position; controlling a laser to emit a laser beam, wherein the output power of the laser is 25W-35W; the laser beam passes through a spot homogenization device to obtain a rectangular flat spot, wherein the length of the rectangular flat spot is 15mm-25mm, and the width of the rectangular flat spot is 8mm-12mm; the flat spot acts on the surface of the plurality of layers of diaphragms outside the battery cell for 0.08s-0.12s to hot melt weld the plurality of layers of diaphragms into one body.

2. The laser welding method according to claim 1, wherein the plurality of layers of diaphragms have a plurality of welding positions; the laser and the spot homogenization device are moved in sequence to make the flat spot act on the plurality of welding positions in sequence; or the plurality of layers of diaphragms have a plurality of welding positions; the battery cell is moved in sequence to make the plurality of welding positions receive the flat spot in sequence; or 3. The laser welding method according to claim 1, characterized in that, the plurality of layers of diaphragms have a plurality of welding positions; the position of the flat spot is adjusted by a scanning galvanometer module to make the flat spot act on the plurality of welding positions in sequence. The laser welding method is completed by a laser welding system, and the laser welding system comprises: a laser for emitting a laser beam, wherein the output power of the laser is 25W-35W; a spot homogenization device for homogenizing the laser beam to obtain a flat spot; 4. The laser welding method according to claim 3, characterized in that, wherein the flat spot is a rectangular flat spot; the length of the rectangular flat spot is 15mm-25mm, and the width of the rectangular flat spot is 8mm-12mm; the flat spot acts on the surface of the plurality of layers of diaphragms; and the action time of the flat spot on the surface of the plurality of layers of diaphragms per unit area is 0.08s-0.12s to hot melt weld the plurality of layers of diaphragms into one body. The system further comprises a pressing device; the pressing device is placed at the welding position of the plurality of layers of diaphragms to press and tightly fit the plurality of layers of diaphragms at the welding position; 5. The laser welding method according to claim 3, characterized in that, the flat spot passes through the pressing device to act on the plurality of layers of diaphragms at the welding position. The system further comprises a scanning galvanometer module; the scanning galvanometer module is formed with a working field; 6. The laser welding method according to claim 3, characterized by the scanning galvanometer module can focus the flat spot and move the focused flat spot in the working field to adjust the position of the focused flat spot on the surface of the plurality of layers of diaphragms. The system further comprises a dust removal device; the dust removal device can clean impurities generated in the hot melt welding process.

7. The laser welding method according to claim 5, wherein the moving speed of the focused flat spot in the working field is 1m\s-50m\s; 8. The laser welding method according to any one of claims 3 to 7, characterized in that, the scanning galvanometer module comprises a field lens; the focal length of the field lens is 300mm-350mm; the length of the working field is 180mm-220mm, and the width of the working field is 180mm-220mm.

9. The laser welding method according to claim 8, characterized in that, The laser is a semiconductor laser. The wavelength range of the laser beam emitted by the semiconductor laser is 300nm-600nm.

10. A battery, characterized by The battery comprises an electric core and a multi-layer separator wound outside the electric core, and the multi-layer separator is an integral structure formed by laser heat fusion welding through the laser welding method of any one of claims 1-9.

11. The battery of claim 10, wherein, The surface of the separator is provided with an auxiliary welding layer.

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