Composite current collector and ultrasonic welding method thereof

Abstract

This invention discloses a composite current collector, comprising a protective layer, a filler aluminum layer, a current collector body, and a metal connecting piece stacked sequentially. The current collector body has a welding area with a plurality of micropores arranged in an array. The micropores penetrate two opposite surfaces of the current collector body along its thickness direction. The metal connecting piece has spikes corresponding to the micropores on its side facing the current collector body. The spikes penetrate the corresponding micropores and form a mechanical interlocking structure with the filler aluminum layer. By setting an array of micropores on the current collector body and spikes on the metal connecting piece, welding energy is directionally transferred during welding through the spikes, improving welding quality and efficiency. Furthermore, the spikes, under pressure and ultrasonic vibration, penetrate the micropores and form a mechanical interlocking and metallurgical bond with the filler aluminum layer, avoiding welding drift caused by material tension differences, thus improving welding reliability and consistency and simplifying the welding process.

Description

Technical Field

[0001] This invention relates to the field of current collector technology, specifically to a composite current collector and its ultrasonic welding method. Background Technology

[0002] With the increasing demands for battery energy density and safety from new energy vehicles and portable electronic devices, composite current collectors ("metal-polymer insulation layer-metal" sandwich structure) have become an important development direction due to their advantages such as lightweight and suppression of thermal runaway. However, their special structure brings fundamental challenges to tab welding: the middle polymer insulation layer (such as PET, PP) blocks the current path, making it impossible for the upper and lower metal layers to conduct directly. If traditional ultrasonic welding is used, a large amount of energy will be absorbed and scattered when passing through the insulation layer, resulting in insufficient effective energy at the target interface and making it very easy to cause poor welding.

[0003] To overcome the aforementioned bottlenecks, the mainstream industry practice employs an "adapter welding" process, which involves adding an extra metal foil as an adapter to weld with the composite current collector. However, this method introduces new materials and processes, increasing costs and battery internal resistance, and significantly increasing the thickness of the tab side when multiple layers of tabs are stacked. The welding process itself also presents numerous problems: for example, when using foil that is narrower at the top and wider at the bottom for adapter welding, relative displacement (drift) easily occurs under welding head pressure and ultrasonic vibration due to differences in size and tension, leading to unstable welding dimensions; furthermore, uneven energy transfer is a prominent issue: unilateral ultrasonic welding can easily result in significant differences in welding quality between the top layer near the ultrasonic source and the bottom layer far away (the top layer is solidly welded while the bottom layer is poorly welded). While existing methods address "how to weld," they fail to systematically solve the problems of "how to weld well, weld firmly, and weld consistently." Therefore, breaking through industry barriers urgently requires an innovative method that starts from the structural design source and achieves intrinsic matching with welding process parameters. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a composite current collector and its ultrasonic welding method. It solves the problems of low energy transmission efficiency and easy formation of incomplete welds caused by the barrier of the polymer insulating layer in the ultrasonic welding of composite current collectors and metal connecting pieces, as well as the high cost and increased internal resistance caused by the introduction of additional materials and processes in the existing "transfer welding" process.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A composite current collector includes a protective layer, a filler aluminum layer, a current collector body, and a metal connecting piece stacked sequentially. The current collector body has a welding area with a plurality of micropores arranged in an array. The micropores penetrate two opposite surfaces of the current collector body along its thickness direction. The metal connecting piece has spikes corresponding to the micropores on its side facing the current collector body. The spikes penetrate the corresponding micropores and form a mechanical interlocking structure with the filler aluminum layer. By setting an array of micropores on the current collector body and spikes on the metal connecting piece, welding energy is directionally transferred during welding through the spikes, improving welding quality and efficiency. Furthermore, the spikes, under pressure and ultrasonic vibration, penetrate the micropores and form a mechanical interlocking and metallurgical bond with the filler aluminum layer, avoiding welding drift caused by material tension differences, thus improving welding reliability and consistency and simplifying the welding process.

[0006] As a preferred embodiment, the pore diameter of the micropore is 0.1 to 0.6 mm, and the pore spacing between adjacent micropores is 0.4 to 12 mm.

[0007] As a preferred embodiment, the spike is conical, with a base diameter of 0.3–0.7 mm and a height of 2–6 mm.

[0008] As a preferred embodiment, the total area of ​​the micropores in the welding area is greater than or equal to the sum of the bottom areas of all the spikes.

[0009] As a preferred embodiment, the current collector body is composed of a first aluminum foil layer, a PE layer and a second aluminum foil layer stacked sequentially, and the thickness of the current collector body in the welding area is 355-365µm.

[0010] As a preferred embodiment, the thickness of the filler aluminum layer is 90–110 µm, and the thickness of the protective layer is 45–55 µm.

[0011] As a preferred embodiment, the protective layer is a PET layer.

[0012] The present invention also provides a composite current collector welding method, comprising the following steps: S1. The metal connecting piece with spikes on the surface, the current collector body with a pre-fabricated micro-hole array, the filler aluminum layer and the protective layer are stacked in sequence, and the spikes are aligned with the position of the micro-hole array to form a stacked assembly to be soldered. S2. An ultrasonic welding system is used to weld the stacked components to be welded. The ultrasonic amplitude is controlled between 30% and 80% of the rated amplitude of the ultrasonic welding head, the welding pressure is controlled between 2.0 Bar and 5.0 Bar, and the welding energy input is controlled between 300 J and 500 J. After welding, the spikes of the metal connecting piece pass through the micropores on the current collector body and form a mechanical interlocking structure with the filled aluminum layer.

[0013] As a preferred embodiment, the ultrasonic welding system includes an ultrasonic generator, a transducer, an amplitude transformer, a welding head, a pressure actuator, and a parameter control unit. The transducer is electrically connected to the ultrasonic generator and is mounted on the actuator end of the pressure actuator. The amplitude transformer is connected to the end of the transducer, and the welding head is connected to the end of the amplitude transformer. The parameter control unit is electrically connected to the ultrasonic generator and the pressure actuator, and is used to set and control the ultrasonic amplitude, welding pressure, and welding energy during the welding process.

[0014] As a preferred embodiment, the conical spikes on the metal connecting piece are integrally formed by mechanical stamping, and the filling aluminum layer is a third aluminum foil layer.

[0015] Compared with the prior art, the present invention has obvious advantages and beneficial effects, specifically; By setting a micropore array on the current collector body and setting spikes on the metal connecting piece, welding energy can be directionally transferred through the spikes during welding, improving welding quality and efficiency. Under pressure and ultrasonic vibration, the spikes pass through the micropores and form a mechanical interlock and metallurgical bond with the filled aluminum layer, avoiding welding drift caused by material tension differences and problems such as low welding strength and easy cold welds caused by energy absorption by the polymer insulation layer. This improves welding reliability and consistency and simplifies the welding process.

[0016] The synergistic effect of micropores and spikes creates a highly efficient "energy guiding channel," altering the traditional propagation path of ultrasonic energy. This allows energy to be concentrated and efficiently transferred to the target metal interface, significantly reducing unnecessary dissipation in non-target insulating layers. Combined with precise assembly alignment and parametric control, accurate energy input to the welding interface is achieved. This not only improves welding efficiency and quality and reduces the risk of over-welding, but also makes it possible to achieve a more energy-efficient and reliable manufacturing process.

[0017] By introducing a filler aluminum layer and a protective layer, combined with precisely controlled welding pressure, the impact can be effectively buffered during welding, preventing the composite current collector multilayer structure from being crushed or the polymer insulation layer from overheating and decomposing due to the impact of the welding head. At the same time, it avoids the adhesion between the metal layer and the welding head, thereby ensuring the consistency of welding and the yield rate.

[0018] To more clearly illustrate the structural features, technical means, and specific objectives and functions achieved by the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the composite current collector according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of an ultrasonic welding system according to an embodiment of the present invention.

[0020] Explanation of reference numerals in the attached diagram: 10. Metal connecting piece; 11. Spike; 20. Current collector body. 21. Micropores; 22. First aluminum foil layer; 23. PE layer 24. Second aluminum foil layer; 30. Filler aluminum layer; 40. Protective layer 50. Ultrasonic welding system; 51. Ultrasonic generator; 52. Transducer 53. Amplitude bar 54. Welding head. Detailed Implementation

[0021] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the indicated position or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] like Figure 1As shown, a composite current collector includes a protective layer 40, a filler aluminum layer 30, a current collector body 20, and a metal connecting piece 10 stacked sequentially. The current collector body 10 has a welding area with a plurality of micropores 21 arranged in an array. The micropores 21 penetrate two opposite surfaces of the current collector body 20 along its thickness direction. The metal connecting piece 10 has spikes 11 corresponding to the micropores 21 on its side facing the current collector body 20. The spikes 11 pass through the corresponding micropores 21 and form a mechanical interlocking structure with the filler aluminum layer 30. By setting the micropore array on the current collector body 20 and the spikes 11 on the metal connecting piece 10, the welding energy is directionally transferred through the spikes during welding, improving welding quality and efficiency. Under pressure and ultrasonic vibration, the spikes pass through the micropores and form a mechanical interlocking and metallurgical bond with the filler aluminum layer, avoiding welding drift caused by material tension differences, improving welding reliability and consistency, and simplifying the welding process.

[0024] In this invention, the diameter of the micropores 21 is 0.1–0.6 mm, and the spacing between adjacent micropores 21 is 0.4–12 mm. The spikes 11 are conical, with a base diameter of 0.3–0.7 mm and a height of 2–6 mm. The total area of ​​the micropores 21 in the welding area is greater than or equal to the sum of the base areas of all spikes 11.

[0025] In this invention, the current collector body 20 is composed of a first aluminum foil layer 22, a PE layer 23, and a second aluminum foil layer 24 stacked sequentially. The thickness of the current collector body 20 in the welding area is 355–365 µm. The thickness of the filler aluminum layer 30 is 90–110 µm, and the thickness of the protective layer 40 is 45–55 µm. The protective layer 40 is a PET layer.

[0026] The present invention also provides a composite current collector welding method, comprising the following steps: S1. The metal connecting piece 10 with spikes on its surface, the current collector body 20 with a pre-fabricated micro-hole array, the filler aluminum layer 30 and the protective layer 40 are stacked in sequence, and the positions of the spikes 11 and the micro-hole array 21 are aligned to form a stacked assembly to be welded. In practical applications, a clamping and positioning device can be set to fix and align the metal connecting piece 10, the current collector body 20, the filler aluminum layer 30 and the protective layer 40, thereby ensuring that the welding area is flat and accurately aligned.

[0027] S2. The ultrasonic welding system 50 is used to weld the laminated assembly to be welded. The ultrasonic amplitude is controlled between 30% and 80% of the rated amplitude of the ultrasonic welding head, the welding pressure is controlled between 2.0 Bar and 5.0 Bar, and the welding energy input is controlled between 300 J and 500 J. After welding, the spikes of the metal connecting piece pass through the micropores on the current collector body and form a mechanical interlocking structure with the filled aluminum layer.

[0028] In this invention, the ultrasonic welding system 50 includes an ultrasonic generator 51, a transducer 52, an amplitude transformer 53, a welding head 54, a pressure actuator (not shown), and a parameter control unit (not shown). The transducer 52 is electrically connected to the ultrasonic generator 51 and is mounted on the actuating end of the pressure actuator. The amplitude transformer 53 is connected to the end of the transducer 52, and the welding head 54 is connected to the end of the amplitude transformer 53. The parameter control unit is electrically connected to the ultrasonic generator 51 and the pressure actuator. The parameter control unit is used to set and control the ultrasonic amplitude, welding pressure, and welding energy during the welding process. The ultrasonic welding system 50 adopts existing technology, and its specific structure and working principle will not be described in detail here. The parameter control unit has a built-in storage module, which can store and recall process parameter sets for composite current collector components with different structural parameters.

[0029] As a preferred embodiment, the conical spikes on the metal connecting piece are integrally formed by mechanical stamping. Specifically, an aluminum sheet of 800–1200 µm is stamped using a mold with a corresponding structure to cause local plastic deformation of the material and form the spikes. The filling aluminum layer is formed by a third aluminum foil layer with a single layer thickness of 90–110 µm.

[0030] The following describes welding tests of the composite current collector structure of the present invention, in conjunction with embodiments and comparative examples. Preparation of the standard test assembly: First, a micropore array (pore diameter ∅0.3 mm, pore spacing 2.0 mm) was prefabricated in the tab welding area of ​​the multilayer composite current collector body with a total thickness of 360 μm. Then, it was aligned and assembled with a metal connecting piece having conical spikes on its surface (bottom diameter 0.5 mm, height 4 mm). Finally, a 100 μm thick filler aluminum layer and a 50 μm thick PET protective layer were sequentially covered on top to form the stacked assembly to be welded. All welding experiments were conducted on the same ultrasonic welding system. The impact of changing the core process parameters (ultrasonic amplitude, welding pressure, welding energy) and mode on the welding quality was evaluated. Welding quality was comprehensively evaluated through peel strength testing (unit: N), interfacial resistance testing (unit: mΩ), and macro / micro morphology observation.

[0031] Example 1 This embodiment aims to verify the optimization effect of the core process parameter window of the present invention.

[0032] Welding process parameters: Time control mode is adopted. The ultrasonic amplitude is set to 50% of the rated amplitude of the ultrasonic welding head, the welding pressure is 3.0 Bar, and the welding energy is 300 J.

[0033] Welding object: The standard test component prepared above.

[0034] Results and Analysis: The welding process was stable with no abnormal noise. Post-weld inspection revealed an intact protective layer and a smooth weld area. Tests showed an average peel strength of 45.2 N and an interfacial resistivity of 0.85 mΩ. Metallographic sections indicated that the conical spikes of the metal connector completely penetrated the micropores, forming a dense and continuous metallurgical bond with the filled aluminum layer. No crushing or thermal damage cracks were observed in the polymer layer surrounding the micropores. This set of parameters achieved a good balance between energy input, mechanical interlocking, and material deformation.

[0035] Example 2 This embodiment is used to investigate the effect of the coordinated changes in amplitude and pressure on the welding effect under a fixed energy mode, and is compared with Embodiment 1.

[0036] Welding process parameters: Time-controlled mode is adopted. The fixed welding energy is 300 J. The first set of parameters is: amplitude 60%, pressure 4.0 Bar; the second set of parameters is: amplitude 30%, pressure 4.5 Bar.

[0037] Welding object: The standard test component prepared above.

[0038] Results and Analysis: The first group (60% / 4.0 Bar) exhibited strong vibration during welding, with a post-weld peel strength of 38.7 N and an interfacial resistance of 0.92 mΩ. However, microscopic observation revealed slight spattering in the aluminum filler layer. The second group (30% / 4.5 Bar) showed a smooth welding process, with a peel strength of 42.1 N and an interfacial resistance of 0.88 mΩ. The bond strength was good but slightly lower than in Example 1. The results indicate that excessively high amplitude may cause excessive plastic flow of the material, leading to spattering; while high pressure combined with low amplitude can ensure bonding, the energy transfer efficiency may be slightly lower than the optimal combination.

[0039] Example 3 This embodiment investigates the potential of segmented welding mode to improve welding strength, especially interfacial bonding strength.

[0040] Welding process parameters: Segmented amplitude control mode is adopted. The total welding energy is set to 300 J. The specific segment settings are as follows: First segment (preheating segment): pressure 3.0 Bar, amplitude 30%, time 200 ms; Second segment (main welding segment): pressure 3.0 Bar, amplitude 40%, time 500 ms; Third segment (pressure holding segment): pressure 3.0 Bar, amplitude 10%, time 300 ms.

[0041] Welding object: The standard test component prepared above.

[0042] Results and Analysis: The segmented welding process is more gentle. Post-weld testing showed a significant increase in average peel strength to 49.4 N and a further reduction in interfacial resistance to 0.71 mΩ. Analysis suggests that the segmented amplitude settings achieved a gradient energy input: the initial lower amplitude facilitated initial material bonding and heat accumulation; the main welding segment used the optimal amplitude to achieve full bonding; and the low-amplitude pressure holding at the end helped stabilize the interface and release stress, thus achieving comprehensive performance superior to the single-segment time mode.

[0043] Example 4 This embodiment examines the effect of introducing post-processing on improving the long-term reliability of welded joints based on optimal process parameters.

[0044] Welding process parameters: same as in Example 1, i.e., amplitude 40%, pressure 3.0 Bar, energy 300 J (time mode).

[0045] Post-processing: Immediately after welding, the weld area is subjected to local hot pressing treatment (temperature 150°C, pressure 5.0 Bar, time 2 s).

[0046] Welding object: The standard test component prepared above.

[0047] Results and Analysis: After hot pressing, the weld joints appeared denser and smoother. The peel strength increased to 47.5 N, and the interfacial resistance stabilized at 0.72 mΩ. Hot pressing helps to further eliminate residual welding stress, promotes interfacial atomic diffusion, and results in more complete metallurgical bonding, thus improving the thermal and mechanical stability of the joint.

[0048] Example 5 This embodiment aims to verify the boundaries of the process parameter window and explore the welding behavior under higher parameter combinations.

[0049] Welding process parameters: Time-controlled mode is adopted. The ultrasonic amplitude is set to 70%, the welding pressure to 4.5 Bar, and the welding energy to 450 J.

[0050] Welding object: The standard test component prepared above.

[0051] Results and Analysis: The welding process involved high energy input. The post-weld peel strength was 41.5 N, and the interfacial resistivity was 0.95 mΩ. Although the strength indicators were acceptable, macroscopic observation revealed slight adhesive overflow at the weld edge (local melting of the PET protective layer), and microscopic observation showed a large area of ​​plastic deformation in the aluminum filler layer. The results indicate that these parameters are close to the upper limit of the process window. While an effective connection can be formed, there is a risk of damage to the protective layer and excessive deformation, making the process robustness less than that of Example 1.

[0052] Comparative Example 1 This comparative example demonstrates that even with a micro-hole interlocking structure, an effective bond cannot be formed when the welding pressure is too low.

[0053] Welding process parameters: amplitude 40%, welding pressure 1.5 Bar (lower than the window of this invention), energy 300 J.

[0054] Welding object: The standard test component prepared above.

[0055] Results and Analysis: During the welding process, the interlayer bonding of the components was not tight, resulting in significant vibration and noise. After welding, only slight adhesion existed between the connecting piece and the composite current collector; even a slight external force could cause the entire component to detach. Peel strength testing was impossible (it was almost 0 N), and the interface resistance was extremely high, indicating an open circuit. This suggests that insufficient pressure prevented the spikes from effectively penetrating the micropores and forming a tight contact with the aluminum filler layer, hindering the effective transmission of ultrasonic energy to the interface and leading to complete weld failure.

[0056] Comparative Example 2 This comparative example is used to demonstrate that when the welding energy is too low, it cannot provide sufficient energy input for the interfacial metallurgical bonding.

[0057] Welding process parameters: amplitude 40%, pressure 3.0 Bar, welding energy 200 J (lower than the window of this invention).

[0058] Welding object: The standard test component prepared above.

[0059] Results and Analysis: The welding process ended rapidly. The weld joint showed no significant change in appearance. Tests showed a peel strength of only 8.3 N and an interfacial resistivity of 3.5 mΩ. The failure mode was the separation of the connecting tab spikes from the filler aluminum layer at the interface. This indicates insufficient energy input, achieving only preliminary mechanical interlocking and failing to induce sufficient atomic diffusion at the metal interface to form a strong metallurgical bond.

[0060] Comparative Example 3 This comparative example is used to demonstrate the damage caused to the composite current collector structure when the amplitude is too high.

[0061] Welding process parameters: amplitude 85% (close to or exceeding the upper limit of the window of this invention), pressure 3.0 Bar, energy 300 J.

[0062] Welding object: The standard test component prepared above.

[0063] Results and Analysis: Vibration was severe during welding. Post-weld, the PET protective layer was found to be yellowed, brittle, and even developed holes in the central area of ​​the weld joint due to overheating. The peel strength was 22.4 N, and the interfacial resistivity was 1.8 mΩ. Metallographic sections showed that some polymer substrates within the composite current collector underwent localized melting and recrystallization due to overheating, resulting in compromised structural integrity. Excessive amplitude led to excessive vibration energy, generating excessive heat and damaging both the polymer insulation and protective layers.

[0064] Comparative Example 4 This comparative example aims to highlight the necessity of the structural design of the present invention by comparing it with a conventional component without a microporous interlocking structure.

[0065] Welding process parameters: The same optimized parameters as in Example 1 were used: amplitude 40%, pressure 3.0 Bar, energy 300J.

[0066] Welding object: The only structural difference between the comparison component and the standard component is that the composite current collector tab area does not have a pre-fabricated microporous array, but is only a flat surface. The other layers (with spiked connecting tabs, aluminum filler layer, PET protective layer) remain unchanged.

[0067] Results and Analysis: Higher energy is required to trigger bonding during the welding process. Post-weld testing showed an average peel strength of only 16.7 N and an interfacial resistance of 2.1 mΩ. The failure mode was complete separation of the connector from the composite current collector; the spikes only left indentations on the polymer layer surface, failing to form an effective interlock. This directly demonstrates that the microporous structure is an indispensable key design element for guiding spike penetration, concentrating ultrasonic energy, and achieving both mechanical and metallurgical bonding. Without this structure, energy would be largely dissipated within the polymer layer, resulting in severely insufficient weld strength.

[0068] The optimal process parameter window was validated: The results of Example 1 (amplitude 50%, pressure 3.0 Bar, energy 300 J) fully validated that the central region of the process parameter window (amplitude 30%-80%, pressure 2.0-5.0 Bar, energy 300-500 J) proposed in this invention has excellent welding performance. This parameter combination, in conjunction with the micropore interlocking structure, achieves a perfect balance between energy input, mechanical penetration, and interfacial reaction, resulting in high peel strength (48.2 N) and low interfacial resistance (0.78 mΩ) without any material damage. It represents the optimal balance point for reliability, efficiency, and quality.

[0069] The strong coupling between structural design and process parameters: The stark contrast between Comparative Example 4 and Example 1 is highly convincing. Under identical optimized process parameters, the weld strength drops by more than 60% and the resistance increases by nearly 120% simply because of the lack of the key structural feature of the "micropore array." This definitively proves that the micropore interlocking structure of this invention is not an auxiliary design, but a necessary prerequisite for achieving efficient ultrasonic welding. This structure effectively solves the core problem of ultrasonic energy absorption and dissipation by the polymer layer in traditional composite current collector welding, creating a channel for the directional transfer of energy to the metal interface.

[0070] Boundary effects and influence mechanisms of process parameters: Comparative Examples 1-3 systematically reveal the consequences of deviating from the optimal window: insufficient pressure (Comparative Example 1) leads to insufficient physical contact and welding failure; insufficient energy (Comparative Example 2) fails to drive interfacial atomic diffusion, achieving only weak bonding; excessive amplitude (Comparative Example 3) induces thermal damage, destroying the integrity of the polymer matrix. These results clearly characterize the boundaries of each parameter, indicating that the parameter range of the present invention is a precisely balanced "safe zone" and "high-efficiency zone".

[0071] Multiple pathways for process optimization: Examples 3 (segmented welding) and 4 (hot-pressing post-treatment) demonstrate the potential to further improve performance based on the core invention. The segmented amplitude mode, through gradient energy input, achieves better stress management and interfacial bonding, resulting in the highest peel strength (49.4 N) in this experiment. Hot-pressing post-treatment further optimizes the interfacial microstructure and improves joint stability. These extended examples demonstrate that the core solution of this invention has good process compatibility and optimization flexibility.

[0072] In summary, this invention improves welding quality and efficiency by incorporating a micropore array on the current collector body and spikes on the metal connecting pieces. These spikes facilitate directional energy transfer during welding, allowing for mechanical interlocking and metallurgical bonding between the spikes and the aluminum filler layer under pressure and ultrasonic vibration. This avoids welding drift caused by material tension differences and low weld strength and susceptibility to incomplete welds due to energy absorption by the polymer insulating layer. The invention enhances welding reliability and consistency while simplifying the welding process. The synergistic effect of the micropores and spikes creates a highly efficient "energy guiding channel," altering the traditional propagation path of ultrasonic energy. This allows for concentrated and efficient energy transfer to the target metal interface, significantly reducing unnecessary energy dissipation in non-target insulating layers. Combined with precise assembly alignment and parametric control, accurate energy input to the welding interface is achieved. This not only improves welding efficiency and quality and reduces the risk of over-welding, but also makes it possible to achieve a more energy-efficient and reliable manufacturing process. By introducing a filler aluminum layer and a protective layer, combined with precisely controlled welding pressure, the impact can be effectively buffered during welding, preventing the composite current collector multilayer structure from being crushed or the polymer insulation layer from overheating and decomposing due to the impact of the welding head. At the same time, it avoids the adhesion between the metal layer and the welding head, thereby ensuring the consistency of welding and the yield rate.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the actual technology of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A composite current collector, characterized in that, The device includes a protective layer, a filler aluminum layer, a current collector body, and a metal connecting piece stacked in sequence. The current collector body has a welding area with a plurality of micropores arranged in an array. The micropores penetrate two opposite surfaces of the current collector body along the thickness direction. The metal connecting piece has spikes corresponding to the micropores on the side facing the current collector body. The spikes penetrate the corresponding micropores and form a mechanical interlocking structure with the filler aluminum layer.

2. The composite current collector according to claim 1, characterized in that, The pore diameter of the micropore is 0.1 to 0.6 mm, and the pore spacing between adjacent micropores is 0.4 to 12 mm.

3. A composite current collector according to claim 2, characterized in that, The spike is conical in shape, with a base diameter of 0.3–0.7 mm and a height of 2–6 mm.

4. A composite current collector according to claim 3, characterized in that, The total area of ​​the micropores in the welding area is greater than or equal to the sum of the bottom areas of all the spikes.

5. A composite current collector according to claim 1, characterized in that, The current collector body is composed of a first aluminum foil layer, a PE layer and a second aluminum foil layer stacked in sequence, and the thickness of the current collector body in the welding area is 355-365µm.

6. A composite current collector according to claim 5, characterized in that, The thickness of the filler aluminum layer is 90–110 µm, and the thickness of the protective layer is 45–55 µm.

7. A composite current collector according to claim 1 or 6, characterized in that, The protective layer is a PET layer.

8. An ultrasonic welding method for composite current collectors, characterized in that, Includes the following steps: S1. The metal connecting piece with spikes on the surface, the current collector body with a pre-fabricated micro-hole array, the filler aluminum layer and the protective layer are stacked in sequence, and the spikes are aligned with the position of the micro-hole array to form a stacked assembly to be soldered. S2. An ultrasonic welding system is used to weld the stacked components to be welded. The ultrasonic amplitude is controlled between 30% and 80% of the rated amplitude of the ultrasonic welding head, the welding pressure is controlled between 2.0 Bar and 5.0 Bar, and the welding energy input is controlled between 300 J and 500 J. After welding, the spikes of the metal connecting piece pass through the micropores on the current collector body and form a mechanical interlocking structure with the filled aluminum layer.

9. The ultrasonic welding method for a composite current collector according to claim 8, characterized in that, The ultrasonic welding system includes an ultrasonic generator, a transducer, an amplitude transformer, a welding head, a pressure actuator, and a parameter control unit. The transducer is electrically connected to the ultrasonic generator and is installed at the actuator end of the pressure actuator. The amplitude transformer is connected to the end of the transducer, and the welding head is connected to the end of the amplitude transformer. The parameter control unit is electrically connected to the ultrasonic generator and the pressure actuator. The parameter control unit is used to set and control the ultrasonic amplitude, welding pressure, and welding energy during the welding process.

10. The ultrasonic welding method for a composite current collector according to claim 8, characterized in that, The conical spikes on the metal connecting piece are integrally formed by mechanical stamping, and the filling aluminum layer is a third aluminum foil layer.

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