Direct laser welding of thin foil materials
Patent Information
- Application Number
- CN202510800636.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2025-04-28
- Filing Date
- 2025-06-16
- Publication Date
- 2026-10-30
Smart Images
Figure CN123000241A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of laser welding, and more specifically, to systems and methods for direct laser welding of thin foil materials. Background Technology
[0002] Batteries (such as prismatic lithium-ion batteries) can have a stacked structure, wherein each battery cell includes an anode, a separator, and a cathode between a negative current collector and a positive current collector. The battery cells are stacked in an alternating structure such that adjacent battery cells share a single current collector. Each current collector (also called a “foil”) includes an electrode extending from it, and the position of the electrode on the current collector can depend on the polarity of the current collector. For example, when assembling into a prismatic battery, the electrode of the positive current collector is aligned along a first axis extending in the stacking direction, while the electrode of the negative current collector is aligned along a second axis extending in the stacking direction. Each set of electrodes is then bonded together.
[0003] Ultrasonic welding is used to bond the electrodes together, and then the bonded electrodes are laser-welded to the corresponding terminals. Ultrasonic welding is used to bond the electrodes while removing gases trapped in the interlayer interface, and laser welding is used to form linear weld beads connecting the different materials of the electrodes and terminals. Without this removal, the expansion of trapped gases due to heat during laser welding can affect the performance of the weld joint (e.g., weaken the final joint and / or inhibit joint formation).
[0004] There is a need in this field to reduce the complexity of welding processes. Summary of the Invention
[0005] The aim is to reduce the complexity of the welding process by removing trapped gases and forming optimized laser-welded joints (without requiring ultrasonic welding of the electrodes). The systems, methods, and apparatus described herein utilize through-holes to expel gases trapped during laser welding to form a reverse spiral weld, thereby mitigating or eliminating the impact of trapped gases on the weld joint.
[0006] Furthermore, the systems, methods, and apparatus described herein can optimize the strength and conductivity of electrode assemblies by providing a larger cross-sectional area of the connecting material.
[0007] According to various aspects of this disclosure, a method includes: obtaining a workpiece stack; determining a welding path; and forming a reverse spiral weld. The workpiece stack includes a first component adjacent to a second component to define an interface between the first and second components. The interface includes trapped gas. The welding path lies on the surface of the first component opposite to the second component. The welding path defines a reverse spiral having a starting point at an outer end of the reverse spiral and an ending point at an inner end of the reverse spiral. The reverse spiral weld is formed by the steps of: clamping the workpiece stack; drilling a through-hole near the inner end of the spiral; scanning a beam of at least one laser along the welding path; and releasing the workpiece stack. The workpiece stack is clamped near the welding path to suppress movement of the portion of the workpiece stack to be fused by the reverse spiral weld. After clamping, the through-hole is drilled using at least one laser. The through-hole extends at least through the first component. The size and location of the through-hole are designed such that, during the formation of the reverse spiral weld, its thermal expansion allows trapped gas to escape from the interface between the first and second components to the outside of the workpiece stack. A scanning beam is used to form a reverse spiral weld, which fuses workpieces of a certain thickness together.
[0008] According to a further aspect of this disclosure, the workpiece stack includes a metal foil stack, within which a first component and a second component are included.
[0009] According to a further aspect of the invention, the through hole is concentric with the termination point of the reverse spiral.
[0010] According to a further aspect of the invention, the through hole is located near the fusion zone of the penultimate turn of the reverse spiral.
[0011] According to a further aspect of this disclosure, the method further includes: forming a plurality of reverse spiral welds by determining a plurality of welding paths on the surface of a first component, and repeatedly forming a reverse spiral weld for each of the plurality of welding paths. Each welding path is a corresponding reverse spiral having a starting point at the outer end of the corresponding reverse spiral and an ending point at the inner end of the corresponding reverse spiral. Each of the plurality of reverse spiral welds contacts each of its adjacent reverse spiral welds.
[0012] According to a further aspect of the invention, a plurality of reverse spiral welds define an axis, and the termination point of each weld path is arranged along this axis.
[0013] According to a further aspect of this disclosure, the starting point of each welding path is positioned perpendicular to the axis at the end point of the corresponding welding path.
[0014] According to a further aspect of the invention, each of the plurality of reverse spiral welds overlaps with each of its adjacent reverse spiral welds, and the overlap is 25% based on the diameter of the finished spiral weld.
[0015] According to a further aspect of this disclosure, each of the plurality of reverse spiral welds includes a portion corresponding to the starting point of the respective welding path, wherein the portion does not contact any of the adjacent reverse spiral welds.
[0016] According to various aspects of this disclosure, a method includes: obtaining a plurality of battery electrodes; determining a welding path; and forming a reverse spiral weld. The plurality of battery electrodes includes a first battery electrode and a second battery electrode, which are abutted to define an interface between them, the interface including trapped gas. The welding path is on the surface of the first battery electrode opposite to the second battery electrode, the welding path defining a reverse spiral having a starting point at an outer end of the reverse spiral and an ending point at an inner end of the reverse spiral. The reverse spiral weld is formed by the following steps: clamping the plurality of battery electrodes, drilling a through-hole near the inner end of the spiral, scanning a beam of at least one laser along the welding path, and releasing the plurality of battery electrodes. The plurality of battery electrodes are clamped near the welding path to suppress movement of the portion of the workpiece stack to be fused by the reverse spiral weld. After clamping is completed, a through-hole is drilled using at least one laser. The through-hole extends at least through the first electrode. The size and location of the through-holes are designed so that, during the formation of the reverse spiral weld, their thermal expansion allows trapped gas to escape from the interface between the first and second battery electrodes to the outside of the multiple battery electrodes. A scanning beam is used to form the reverse spiral weld, which fuses multiple battery electrodes of a certain thickness together from the starting point to the end point.
[0017] According to a further aspect of the invention, the through hole is concentric with the termination point of the reverse spiral.
[0018] According to a further aspect of this disclosure, the method further includes forming a plurality of reverse spiral welds by the following steps: determining a plurality of welding paths on the surface of the first electrode, and for each of the plurality of welding paths, repeatedly forming the reverse spiral weld. Each welding path is a corresponding reverse spiral having a starting point at the outer end of the corresponding reverse spiral and an ending point at the inner end of the corresponding reverse spiral. Each of the plurality of reverse spiral welds contacts each of its adjacent reverse spiral welds.
[0019] According to a further aspect of the invention, a plurality of reverse spiral welds define an axis, and the termination point of each weld path is arranged along this axis.
[0020] According to a further aspect of this disclosure, the starting point of each welding path is positioned perpendicular to the axis at the end point of the corresponding welding path.
[0021] According to a further aspect of the invention, each of the plurality of reverse spiral welds overlaps with each of its adjacent reverse spiral welds, and the overlap is 25% based on the diameter of the finished spiral weld.
[0022] According to an aspect of this disclosure, battery electrodes are joined together by at least one reverse spiral weld. The at least one reverse spiral weld is formed by the following steps: clamping multiple battery electrodes, drilling a through-hole near the inner end of the spiral, scanning a laser beam along the welding path, and releasing the multiple battery electrodes. The multiple battery electrodes are clamped near the welding path to suppress movement of the stacked portion of the workpiece to be fused by the reverse spiral weld. After clamping, a through-hole is drilled using at least one laser. The through-hole extends at least through a first battery electrode. The size and location of the through-hole are designed such that, during the formation of the reverse spiral weld, its thermal expansion allows trapped gas to escape from the interface between the first and second battery electrodes to the outside of the multiple battery electrodes. Scanning the laser beam from the start point to the end point forms the reverse spiral weld, which fuses multiple battery electrodes of a certain thickness together.
[0023] According to a further aspect of the invention, the through hole is concentric with the termination point of the reverse spiral.
[0024] According to a further aspect of the invention, at least one reverse spiral weld is a plurality of reverse spiral welds, and the plurality of reverse spiral welds are formed by the following steps: determining a plurality of welding paths on the surface of a first electrode and, for each of the plurality of welding paths, repeatedly forming a reverse spiral weld. Each welding path is a corresponding reverse spiral having a starting point at the outer end of the corresponding reverse spiral and an ending point at the inner end of the corresponding reverse spiral. Each of the plurality of reverse spiral welds contacts each of its adjacent reverse spiral welds.
[0025] According to a further aspect of the invention, a plurality of reverse spiral welds define an axis, the termination point of each weld path is arranged along the axis, and the start point of each weld path is located at a position substantially perpendicular to the axis where the termination point of the corresponding weld path is located.
[0026] According to a further aspect of the invention, each of the plurality of reverse spiral welds overlaps with each of its adjacent reverse spiral welds, and the overlap is 25% based on the diameter of the finished spiral weld.
[0027] The above-described features and advantages, as well as other features and advantages of the invention, will become apparent from the following detailed description of the best mode for carrying out the present disclosure, taken in conjunction with the accompanying drawings. Attached Figure Description
[0028] The accompanying drawings are illustrative and not intended to limit the subject matter as defined in the claims. Exemplary aspects will be discussed in the following detailed description and illustrated in the drawings, wherein:
[0029] Figure 1 A schematic reverse spiral weld is shown according to an aspect of this disclosure;
[0030] Figures 2A-2E Multiple stages of forming a reverse spiral weld at the weld site on a stack of workpieces are shown according to aspects of this disclosure;
[0031] Figure 3 This illustrates a plurality of reverse spiral welds formed sequentially on a stack of workpieces according to aspects of this disclosure;
[0032] Figure 4 A method for forming at least one reverse spiral weld on a stack of workpieces according to aspects of this disclosure is shown;
[0033] Figure 5 A method for forming a reverse spiral weld seam according to aspects of this disclosure is shown;
[0034] Figures 6A-6E This illustrates multiple stages of forming a reverse spiral weld at a weld joint on a workpiece stack according to another aspect of this disclosure; and
[0035] Figures 7A-7E This illustrates multiple stages of forming a reverse spiral weld at a weld site on a stack of workpieces, according to another aspect of this disclosure. Detailed Implementation
[0036] Batteries (such as prismatic lithium batteries) can have a stacked structure, wherein each battery cell includes an anode, a separator, and a cathode between a negative current collector and a positive current collector. The battery cells are stacked in an alternating structure such that adjacent battery cells share a single current collector.
[0037] Each current collector (also called a "foil") includes an electrode extending from it, and the position of the electrode on the current collector may depend on the polarity of the current collector. For example, when assembled into a prismatic battery, the electrode of the positive current collector is aligned along a first axis extending in the stacking direction, while the electrode of the negative current collector is aligned along a second axis extending in the stacking direction.
[0038] These electrodes can be bonded to terminals (also known as "current collectors"). For example, electrodes of a positive current collector are bonded to a positive terminal to enhance conductivity between the positive terminal and each individual electrode, and electrodes of a negative current collector are bonded to a negative terminal to enhance conductivity between the negative terminal and each individual electrode.
[0039] As described in more detail below with reference to the accompanying drawings, a laser scanning system is used to fuse stacks of individual battery electrodes to each other and to their respective terminals in a single process flow. The laser scanning system includes a laser scanning head (also called a scanning head or laser head) and a control unit.
[0040] The laser scanning head is configured to guide a laser beam to a target workpiece. The laser scanning head can move relative to the target workpiece. The laser scanning head can form a laser beam to provide the desired beam size at a focal plane corresponding to the target workpiece. The laser scanning head can also be configured to move the laser spot relative to itself such that the laser spot follows a desired path on the workpiece, while the laser scanning head and the target workpiece remain in a fixed position relative to each other.
[0041] The control unit is configured to control and coordinate the operation of various components of the laser welding system, enabling the laser scanning head to perform laser cutting and laser joining operations at different positions on the target workpiece.
[0042] Prior to connection, the stacked electrodes can be aligned with the terminal pieces in a structure that is at least partially overlapping, such that the mating surfaces of the terminal pieces abut the mating surfaces of the stacked electrodes. Sufficient energy is absorbed from the incident laser beam by the target workpiece and conducted through the layers beneath the upper surface of the workpiece, generating heat at the welding site to form a molten pool from the substrate. As the laser scans forward, the molten pool in this area cools to form a weld joint that fuses the battery electrodes together and along their mating surfaces to the metal terminals.
[0043] Now refer to Figure 1 The diagram illustrates a schematic reverse spiral weld 100. The reverse spiral weld is formed, for example, by a laser system. The example shown includes a weld path 102 superimposed on the ultimately formed weld bead 104. The weld path 102 is spiral in shape. In some respects, the spiral shape is an Archimedean spiral. Furthermore, although the weld path 102 shown includes two turns, it is conceivable that more or fewer turns could be used to obtain the desired weld joint.
[0044] To form the reverse spiral weld 100, a laser beam scans along the welding path 102 from the starting point 106 to the ending point 108. More specifically, the reverse spiral welding path 102 includes a starting point 106 located outside the spiral and an ending point 108 located inside the spiral. In some respects, the ending point 108 is the center of the reverse spiral.
[0045] The dimensions of the spiral and weld bead 104 can be designed such that each turn of the weld is close enough to remelt the interior of the fusion zone of the previous turn and provide a continuous joint.
[0046] Figures 2A-2E The process of forming a reverse spiral weld 100 at the welding site on the workpiece stack 210 is shown. Figure 2A The welding area is shown after the planned welding path 102. After the welding path 102 is planned, the laser moves to the end point 108 of the welding path 102 to drill a through hole 212 in the workpiece stack 210.
[0047] Figure 2B The welding area is shown, in which a through-hole 212 passes through the workpiece stack 210. In the example shown, the through-hole 212 is concentric with the end point 108 of the welding path 102. After the through-hole 212 is cut, the laser moves to the starting point 106 of the welding path 102 and begins to form the weld bead 104.
[0048] Figure 2C The weld area is shown after the laser has traveled approximately one-quarter of a turn in a counter-spiral motion along the welding path 102. During the fusion of the layers of the workpiece stack 210, the gas trapped between the joint surfaces and in front of the molten pool is heated and expands. As the pressure of the expanding gas increases, if the pressure of the expanding gas overcomes the stagnant pressure of a given fluid path, then a portion of the gas will travel a short distance along the joint surface. Advantageously, the through-hole 212 can provide a predetermined, optimized distance for at least a portion of the expanding gas to escape from the workpiece stack 210, thereby optimizing the porosity of the weld bead 104.
[0049] Figure 2D The diagram shows the weld area after the laser has moved approximately one counter-spiral turn along the welding path 102. As the laser approaches this portion forming weld bead 104, a certain amount of trapped gas is confined to the inner circumference of the fusion zone. At this stage of weld formation, the through-hole 212 provides a low-resistance path for the movement of the expanding trapped gas, thereby delivering these gases to the external environment rather than absorbing them into the weld joint or ejecting molten material as they escape through the molten pool. Advantageously, the through-hole 212 drains all or substantially all of the trapped, confined gas.
[0050] Figure 2E The reverse spiral weld bead 104 at the weld site is shown after the laser completes the scanning of the weld path 102.
[0051] Advantageously, the removal of trapped, confined gas through the through-hole 212 optimizes the porosity of the weld bead 104, the material retention in the workpiece stack 210 of the weld joint, and / or the uniformity of properties in the reverse spiral weld 100 joint. The porosity of the weld bead 104 is optimized because the trapped gas is removed in a controlled manner, rather than being absorbed by the molten pool. Optimized material retention is achieved by preventing trapped cavitation from rapidly depressurizing and entering the molten pool at a rate that carries partially molten material out of the pool. The optimized uniformity of the weld joint includes optimized mechanical and / or electrical properties. Optimized mechanical properties include, for example, more uniform conditions around the periphery of the fusion zone during formation, and the termination point 108 of the weld bead 104 being located within this periphery. Optimized electrical properties include, for example, reduced porosity and a uniform crystal structure throughout the reverse spiral weld 100.
[0052] Figure 3 Multiple reverse spiral welds 100a-c are shown, each weld being continuously formed on the workpiece stack 210. Individual weld passes 104 (e.g., the first reverse spiral weld 100a) can be referenced above. Figures 2A-2E The methods described are similar to those used in the formation process.
[0053] Multiple reverse spiral welds 100 define an axis 302. In the example shown, the termination point 108 of each weld path 102 is located on the axis 302. It is conceivable that the termination point 108 of each weld path 102 may deviate from the axis 302 in a predetermined pattern (e.g., an alternating pattern). For example, the first weld in reverse spiral welds 100a-c may be offset from the axis 302 by a predetermined distance in a first direction, and the adjacent second weld in reverse spiral welds 100a-100c may be offset from the axis 302 by a predetermined distance in a second direction opposite to the first direction.
[0054] Advantageously, the plurality of reverse spiral welds 100a-c can at least contact adjacent welds among the plurality of reverse spiral welds 100a-c to enhance the uniformity and continuity of the cross-section of the welded joint along axis 302. In the example shown, each of the plurality of reverse spiral welds 100a-c overlaps with any adjacent reverse spiral weld 100a-c. While not bound by theory, it is believed that overlapping reverse spiral welds 100a-c can further optimize the porosity of the weld bead 104 by venting trapped gases in the joint surface that were heated and pressurized during the formation of the previous reverse spiral weld 100.
[0055] In some respects, the overlap is 25%, which is measured based on the diameter of the finished spiral weld. Advantageously, although not bound by theory, it is believed that the 25% overlap optimizes the cross-sectional area of the weld joint along axis 302, thereby optimizing the electrical performance of the weld joint.
[0056] In some respects, the starting point 106 of each welding path 102 is positioned substantially perpendicular to the axis 302 where the ending point 108 of its corresponding welding path 102 lies. Advantageously, although not bound by theory, this is believed to optimize the uniformity of the weld joint's properties along axis 302, since a portion of the weld bead 104 formed under dynamic substrate conditions related to the weld bead 104 initiation conditions lies outside the continuous portion of the joint. Furthermore, this positioning also optimizes the uniformity of the weld joint fusion zone edge opposite the starting point 106.
[0057] Advantageously, multiple reverse spiral welds 100a-c can be placed on the workpiece stack 210 such that during subsequent operations of the workpiece stack 210 (e.g., due to heating and cooling of the workpiece stack 210 during operation or due to environmental changes), the mechanical stress on the starting point 106 is less than the mechanical stress on the relative edges of the multiple reverse spiral welds 100a-c.
[0058] Figure 4 A method 400 for forming at least one reverse spiral weld is illustrated. At block 402, a workpiece stack 210 is obtained. The workpiece stack 210 includes a first component and a second component. In some aspects, the workpiece stack 210 is a stack of electrode foils, while the component is a single foil. For example, the first component may be the uppermost electrode foil, and the second component may be an electrode foil adjacent to the uppermost electrode foil. The first component and the second component are adjacent to define an interface between them. During component stacking, a small amount of gas is trapped in the interface.
[0059] At box 404, a weld path 102 is defined. Weld path 102 may, for example, be located on the surface of the first component opposite the second component. Weld path 102 is selected such that the resulting weld joint extends through the workpiece stack 210, thereby fusing the workpiece stack 210. Weld path 102 defines a reverse helix such that the starting point 106 of weld path 102 is located at the outer end of the reverse helix, and the ending point 108 of weld path 102 is located at the inner end of the reverse helix.
[0060] At box 406, for example, by referring to the following... Figure 5 The described method forms a reverse spiral weld.
[0061] Optionally, at box 408, additional welding paths can be determined using a method similar to that of box 404, and the forming operation in box 406 can be repeated for each of the plurality of reverse spiral welds, thereby forming a plurality of reverse spiral welds. In some aspects, each of the plurality of reverse spiral welds 100 contacts each of its adjacent reverse spiral welds 100. For example, if the plurality of reverse spiral welds are arranged in a line, then each reverse spiral weld at the end of the line will contact only one adjacent reverse spiral weld, and each reverse spiral weld at the end of the line will contact two adjacent reverse spiral welds. In some aspects, the reverse spiral welds are laid continuously.
[0062] Figure 5 An example of forming a 406 reverse spiral weld on a workpiece stack 210 is shown. At frame 502, the workpiece stack 210 is clamped. The clamp is configured to prevent movement of portions of the parts to be fused within the workpiece stack 210 during welding. The clamp is also configured to hold the workpiece stack 210 in a known position relative to the laser head. In some respects, the clamp is applied close to the weld area. Advantageously, applying the clamp close to the weld area helps increase the interfacial contact between the layers of the workpiece stack 210.
[0063] At frame 504, a through-hole 212 is cut. After clamping, the through-hole 212 is cut using a laser. The through-hole 212 is configured to transport gas trapped within the interfaces between the layers of the workpiece stack 210 to the outside of the workpiece stack 210, thereby preventing porosity in the weld bead 104 due to trapped gas entering the molten pool. The size and location of the through-hole 212 are designed to allow all or substantially all of the gas trapped during the formation of the reverse spiral weld (e.g., gas confined by the first turn of the reverse spiral weld) to pass through. The through-hole 212 is located near the inner end of the spiral.
[0064] In some aspects, the through-hole 212 is concentric with the end of the spiral. Alternatively, the through-hole 212 may be close to the fusion zone of the penultimate turn of the reverse spiral (e.g., the edge of the through-hole 212 is close to the penultimate turn, but structural integrity is maintained so that the molten pool of the penultimate turn does not damage the through-hole). For example, the through-hole 212 may be concentric with the end of the spiral, and its dimensions are designed such that the edge of the through-hole 212 is close to the fusion zone of the penultimate turn of the reverse spiral (e.g., the through-hole 212 is approximately the size of the weld bead). In a further example, the through-hole 212 may be smaller than the size of the weld bead 104 and offset from the end of the spiral, such that the edge of the through-hole is close to the fusion zone of the penultimate turn of the reverse spiral weld. Advantageously, this optimizes the amount of substrate forming the final weld while still venting trapped gases. For example, the through-hole 212 may be offset from the end of the spiral by being placed outside the end of the weld path 102. Alternatively, the through-hole 212 may be offset from the end of the spiral by being positioned at the final extent of the molten pool.
[0065] At frame 506, a laser beam scans along welding path 102 from start point 106 to end point 108, thereby forming a reverse spiral weld. The laser beam is provided with a predetermined power and a predetermined scanning speed to melt the layers of workpiece stack 210. Furthermore, a predetermined scanning speed is selected such that trapped gases are discharged through through-hole 212 instead of seeping into the molten pool.
[0066] At frame 508, the workpiece stack 210 is released, allowing it to move relative to the laser head. For example, the workpiece stack 210 can be transferred to a downstream process or re-clamped in another location for additional welding.
[0067] Figures 6A-6E This illustrates the formation of a reverse spiral weld 100 at the welding location on the workpiece stack 210. Figure 6A The welding area is shown after the planned welding path 102. After the welding path 102 is planned, the laser moves to the end point 108 of the welding path 102 to drill a through hole 612 in the workpiece stack 210.
[0068] Figure 6B The welding area of the through-hole 612 through the workpiece stack 210 is shown. In the example shown, the center of the through-hole 612 is located outside the end point 108 of the welding path 102 and close to the fusion zone of the penultimate turn of the reverse spiral weld 100. Advantageously, although not bound by theory, it is believed that centering the through-hole 612 outside the end point 108 of the welding path 102 can optimize the venting of trapped gas throughout the weld bead 104′. After the through-hole 612 is cut, the laser moves to the start point 106 of the welding path 102 and begins to form the weld bead 104′.
[0069] Figure 6C The weld area is shown after the laser has traveled approximately one-quarter of a turn in a counter-spiral motion along the welding path 102. During the fusion of the layers of the workpiece stack 210, the gas trapped between the joint surfaces and in front of the molten pool is heated and expands. As the pressure of the expanding gas increases, if the pressure of the expanding gas overcomes the stagnant pressure of a given fluid path, then a portion of the gas will travel a short distance along the joint surface. Advantageously, the through-hole 612 can provide a predetermined, optimized distance for at least a portion of the expanding gas to escape from the workpiece stack 210, thereby optimizing the porosity of the weld bead 104′.
[0070] Figure 6D The diagram shows the weld area after the laser has moved approximately one counter-spiral turn along the welding path 102. As the laser approaches this portion forming weld bead 104', a certain amount of trapped gas is confined by the inner circumference of the fusion zone. At this stage of weld formation, the through-hole 612 provides a low-resistance path for the movement of the expanding trapped gas, thereby delivering these gases to the external environment rather than absorbing them into the weld joint or ejecting molten material as they escape through the molten pool. Advantageously, the through-hole 612 vents all or substantially all of the trapped, confined gas.
[0071] Figure 6E The diagram shows the reverse spiral weld bead 104′ at the weld site after the laser completes scanning of the weld path 102. Advantageously, the porosity of the weld bead 104′, the retained material of the workpiece stack 210 in the weld joint, and / or the uniformity of properties in the reverse spiral weld 100 joint can be optimized by venting trapped, confined gas through the through-hole 212. The porosity of the weld bead 104′ is optimized because the trapped gas is vented in a controlled manner, rather than being absorbed by the molten pool. Optimized material retention is achieved by preventing trapped gas cavitation from rapidly depressurizing and entering the molten pool at a rate that carries partially molten material out of the molten pool. The optimized uniformity of the weld joint includes optimized mechanical and / or electrical properties. Optimized mechanical properties include, for example, more uniform conditions on the periphery of the fusion zone during formation, and the termination point 108 of the weld bead 104′ being located within this periphery. Optimized electrical properties include, for example, reduced porosity and a uniform crystal structure throughout the reverse spiral weld 100.
[0072] Figures 7A-7E This illustrates the formation of a reverse spiral weld 100 at the welding location on the workpiece stack 210. Figure 7A The welding area is shown after the planned welding path 102. After the welding path 102 is planned, the laser moves to the end point 108 of the welding path 102 to drill a through hole 712 in the workpiece stack 210.
[0073] Figure 7BThe welding area of the through-hole 712 through the workpiece stack 210 is shown. In the example shown, the center of the through-hole 712 is immediately preceding the end point 108 of the weld path 102 and is close to the fusion zone of the penultimate turn of the reverse spiral weld 100. Advantageously, although not bound by theory, it is believed that placing the center of the through-hole 712 immediately preceding the end point 108 of the weld path 102 can optimize the flow characteristics of the molten pool at the end of the weld bead 104″. After the through-hole 712 is cut, the laser moves to the starting point 106 of the weld path 102 and begins to form the weld bead 104″.
[0074] Figure 7C The weld area is shown after the laser has traveled approximately one-quarter of a turn in a counter-spiral motion along the weld path 102. During the fusion of the layers of the workpiece stack 210, the gas trapped between the joint surfaces and in front of the molten pool is heated and expands. As the pressure of the expanding gas increases, if the pressure of the expanding gas overcomes the stagnant pressure of a given fluid path, then a portion of the gas will travel a short distance along the joint surface. Advantageously, the through-hole 712 can provide a predetermined, optimized distance for at least a portion of the expanding gas to escape from the workpiece stack 210, thereby optimizing the porosity of the weld bead 104″.
[0075] Figure 7D The diagram shows the weld area after the laser has moved approximately one counter-spiral turn along the welding path 102. As the laser approaches this portion of the weld bead 104″, a certain amount of trapped gas is confined to the inner circumference of the fusion zone. During this stage of weld formation, the through-hole 712 provides a low-resistance path for the movement of the expanding trapped gas, thereby delivering these gases to the external environment rather than absorbing them into the weld joint or ejecting molten material as they escape through the molten pool. Advantageously, the through-hole 712 vents all or substantially all of the trapped, confined gas.
[0076] Figure 7EThe diagram shows the reverse spiral weld bead 104″ at the weld site after the laser completes scanning of the weld path 102. Advantageously, the porosity of the weld bead 104″, the retained material of the workpiece stack 210 in the weld joint, and / or the uniformity of properties in the reverse spiral weld 100 joint are optimized by venting trapped, confined gas through the through-hole 212. The porosity of the weld bead 104″ is optimized because the trapped gas is vented in a controlled manner, rather than being absorbed by the molten pool. Optimized material retention is achieved by preventing trapped gas cavitation from rapidly depressurizing and entering the molten pool at a rate that carries partially molten material out of the pool. The optimized uniformity of the weld joint includes optimized mechanical and / or electrical properties. Optimized mechanical properties include, for example, more uniform conditions on the periphery of the fusion zone during formation, and the termination point 108 of the weld bead 104″ being located within this periphery. Optimized electrical properties include, for example, reduced porosity and a uniform crystal structure throughout the reverse spiral weld 100.
[0077] Although the above aspects are described using a single scanning head, it is conceivable that multiple lasers could be used in drilling and / or welding of workpiece stack 210.
[0078] As used in this disclosure, the term "spiral" may refer to a reverse spiral weld pattern as indicated by the context. For example, a spiral weld and a reverse spiral weld may follow the same path, but a spiral weld will form the weld bead starting from the inside of the spiral, while a reverse spiral weld will form the weld bead starting from the outside of the spiral.
[0079] Those skilled in the art will understand that this disclosure can have various modifications and alternatives, and some representative embodiments have been shown by way of example in the accompanying drawings and described in detail above. However, it should be understood that the novel aspects of this disclosure are not limited to the specific forms shown in the drawings. Rather, this disclosure covers all modifications, equivalents, combinations, sub-combinations, arrangements, groupings, and alternatives that fall within the scope and spirit of this disclosure and are defined by the appended claims.
[0080] As used in this article, unless the context clearly indicates otherwise: the words “and” and “or” should be both coordinating and alternative conjunctions, unless the context clearly indicates otherwise; the word “all” means “any and all”; the word “any” means “any and all”; the word “including” means “including but not limited to”; and the singular forms “a,” “one,” and “the” include plural references, and vice versa.
[0081] All numerical values of parameters (e.g., quantities or conditions) in this specification, unless expressly or clearly stated otherwise in the context (including the appended claims), shall be understood to be modified in all cases by the term “about,” regardless of whether “about” actually precedes the numerical value. The numerical parameters listed herein and in the appended claims are approximate values and may vary depending on the desired characteristics expected to be obtained from this disclosure. At least, no attempt is made to limit the application of the doctrine of equivalents to the scope of the claims, and each numerical parameter shall be interpreted at least according to the number of significant figures reported and by applying ordinary rounding methods.
[0082] Approximate terms, such as “approximately,” “about,” “basically,” etc., can in this text mean “at, near, or almost at,” “within 0-10%,” or “within acceptable manufacturing tolerances,” or logical combinations thereof.
[0083] While those skilled in the art will readily understand the limits and range of the term "about," the term "about" indicates that an imprecision is permissible in the numerical value or characteristic. If such imprecision as represented by "about" cannot be understood in its ordinary sense within the art, then "about" indicates at least the possibility of variation arising from conventional methods of measuring and using such parameters. For example, if it cannot be otherwise understood in the art, the term "about" refers to a range of 10% (e.g., ±10%) of the value.
[0084] While those skilled in the art will readily understand the limits and scope of the term "substantially," the term "substantially" means that some degree of imprecision is permissible for the stated value or characteristic. If such imprecision as indicated by "generally" cannot be understood in its ordinary sense within the art, then "substantially" means at least that variations due to manufacturing processes and the measurement of such parameters are possible. For example, if it cannot be otherwise understood in the art, the term "substantially" means within 5% (e.g., ±5%) of the stated value.
[0085] While those skilled in the art will readily understand the limits and scope of the term "essentially," the term "essentially" means that the numerical value or characteristic is permissible with some slight imprecision. If such imprecision as represented by "essentially" cannot be understood in the art according to its ordinary meaning, then "essentially" means that variations in the desired parameter are at least negligible and may not be practically insurmountable. For example, if it cannot be understood otherwise in the art, the term "essentially" means within 1% (e.g., ±1%) of the specified value.
[0086] While those skilled in the art will readily understand the boundaries and scope of the term "pure," it means that a compound may contain very trace amounts of other materials. If the imprecision implied by "pure" cannot be understood in its ordinary sense within the art, then "pure" at least indicates the variation that may arise from separation processes and measurements of such parameters. For example, if it cannot be otherwise understood in the art, the term "pure" means a purity greater than 99.9% of the material.
[0087] It should be understood that the ranges provided herein include the specified range, subranges within the specified range, and each value within the specified range. For example, the range from 5% to 20% should be interpreted as including not only the explicitly listed limit of about 5% to about 20%, but also the individual values, such as 5%, 7%, 9%, 13%, etc., and subranges, such as about 5% to about 9%, about 7% to about 10%, etc.
[0088] Although the best mode of carrying out this disclosure has been described in detail, those skilled in the art to which this disclosure pertains will recognize various alternative designs and embodiments for practicing this disclosure within the scope of the appended claims.
Claims
1. A method comprising: A workpiece stack is obtained, the workpiece stack including a first component, the first component being adjacent to a second component to define an interface between the first component and the second component, the interface including a trapped gas; A welding path is defined on the surface of the first component opposite to the second component, the welding path defining a reverse spiral having a starting point at the outer end and an ending point at the inner end of the reverse spiral; and The reverse spiral weld is formed by the following steps: The workpieces are stacked and clamped near the welding path to suppress movement of the portion of the workpiece stack to be fused by the reverse spiral weld. After the clamping is completed, a through hole is drilled near the inner end of the helix using at least one laser. The through hole extends at least through the first component, and the size and position of the through hole are designed such that during the formation of the reverse helical weld, its thermal expansion allows the trapped gas to be discharged from the interface between the first and second components to the outside of the workpiece stack. The beam of at least one laser is scanned along the welding path from the starting point to the ending point to form a reverse spiral weld, which fuses the workpiece stack of one thickness together; as well as Loosen the stack of workpieces.
2. The method according to claim 1, wherein, The workpiece stack includes a metal foil stack, which includes the first component and the second component.
3. The method according to claim 1, wherein, The through hole is concentric with the termination point of the reverse spiral.
4. The method according to claim 1, wherein, The through hole is located near the fusion zone of the penultimate turn of the reverse spiral.
5. The method according to claim 1, further comprising forming a plurality of reverse spiral welds by the following step: Multiple welding paths are defined on the surface of the first component, wherein... Each welding path is a corresponding reverse spiral, which has a starting point at the outer end of the corresponding reverse spiral and an ending point at the inner end of the corresponding reverse spiral. as well as For each of the plurality of welding paths, the reverse spiral weld is repeatedly formed; Each of the plurality of reverse spiral welds is in contact with each of its adjacent reverse spiral welds.
6. The method according to claim 5, wherein, The plurality of reverse spiral welds define an axis, and the termination point of each welding path is arranged along the axis.
7. The method according to claim 6, wherein, The starting point of each welding path is positioned perpendicular to the axis at the corresponding ending point of the welding path.
8. The method according to claim 5, wherein, Each of the plurality of reverse spiral welds overlaps with each of its adjacent reverse spiral welds, and the overlap is based on 25% of the diameter of the finished spiral weld.
9. The method according to claim 5, wherein, Each of the plurality of reverse spiral welds includes a portion corresponding to the starting point of the respective welding path, wherein the portion does not contact any of the adjacent reverse spiral welds.
10. A method comprising: A plurality of battery electrodes are obtained, the plurality of battery electrodes including a first electrode and a second electrode that are adjacent to each other such that an interface is defined between them, the interface including a trapped gas. A welding path is defined on the surface of the first electrode opposite to the second electrode, the welding path defining a reverse spiral having a starting point at the outer end of the reverse spiral and an ending point at the inner end of the reverse spiral. as well as The reverse spiral weld is formed by the following steps; The plurality of battery electrode sheets are clamped near the welding path to suppress the movement of the portion of the workpiece stack to be fused by the reverse spiral weld. After the clamping is completed, at least one laser is used to drill a through hole near the inner end of the spiral, the through hole extending at least through the first electrode, and the size and position of the through hole are designed such that during the formation of the reverse spiral weld, its thermal expansion allows the trapped gas to be discharged from the interface between the first and second electrodes to the outside of the plurality of battery electrodes. The beam of at least one laser is scanned along the welding path from the starting point to the ending point to form a reverse spiral weld, which fuses the plurality of battery electrodes of one thickness. as well as Loosen the plurality of battery electrodes.