Views: 0 Author: Site Editor Publish Time: 2026-04-03 Origin: Site
Abstract: As New Energy Vehicles (NEVs) and large-scale Energy Storage Systems (ESS) develop rapidly, power battery modules face increasingly stringent requirements for high-current transmission, thermal management, and connection reliability. Traditional single-metal connection materials (such as pure nickel or pure copper) struggle to meet the comprehensive performance demands of high-energy-density battery packs. This paper systematically explores the microscopic interfacial characteristics, electro-thermal physical properties, and application advantages of Copper-Nickel Bimetallic Composites in multi-cell battery assembly. Research indicates that copper-nickel composite strips and busbars, manufactured through advanced roll cladding and stamping processes, achieve excellent metallurgical bonding. They significantly reduce system internal resistance while perfectly resolving the welding challenges associated with highly reflective materials, providing an ideal material-level solution for the structural stability and safety of battery packs.
During the assembly of lithium-ion battery modules, the series and parallel connections between cells are critical factors determining the power output and safety of the entire system. Currently, the mainstream connection materials in the industry face the following technical bottlenecks:
Pure Nickel: While it boasts excellent oxidation resistance and outstanding spot/laser welding performance, its electrical resistivity is relatively high. Under high-current charge/discharge conditions, pure nickel connectors generate significant Joule heating, leading not only to energy loss but also to a high risk of thermal runaway.
Pure Copper: Possesses extremely low electrical resistivity and superior thermal conductivity. However, copper has a very low laser absorption rate (in the infrared spectrum) and is prone to "electrode sticking" and false welding during traditional resistance spot welding. This results in low processing yields, making it difficult to directly apply in large-scale automated production lines.
To break through the physical limitations of these single-metal materials, Copper-Nickel Bimetallic Composites have emerged as a research hotspot and the mainstream industrial application in the field of battery connection materials.
The core technology of copper-nickel composites lies in the bonding quality of the two metal interfaces. Modern, high-quality copper-nickel composite strips are typically manufactured using cold roll cladding or hot rolling techniques.
Under Scanning Electron Microscopy (SEM), the interface of high-quality copper-nickel composites exhibits a dense, void-free characteristic. Because both copper (Cu) and nickel (Ni) have Face-Centered Cubic (FCC) crystal lattices and very similar atomic radii, the atoms of the two metals interdiffuse at the interface under the pressure and heat treatment of the cladding process, forming an ultra-thin solid solution transition layer. This Metallurgical Bond not only endows the material with extremely high interlaminar peel strength—effectively preventing delamination during subsequent stamping and bending processes—but also ensures that no additional contact resistance is generated when electrons transit across the interface (i.e., achieving a good Ohmic contact).
In the copper-nickel bimetallic structure, the pure copper base layer, which accounts for the larger proportion of the thickness, undertakes over 85% of the current-carrying task. Compared to pure nickel tabs of the same dimensions, adopting a composite structure can reduce the overall internal resistance of the connector by more than 60%. This ultra-low internal resistance characteristic greatly enhances the charge and discharge C-rate performance of the battery module and effectively reduces line losses.
In power battery packs, heat accumulation is the core factor inducing safety accidents. The Copper-Nickel Bimetallic Busbar utilizes copper's high thermal conductivity to rapidly conduct and dissipate the localized heat generated by cell terminals during charging and discharging across the entire structural surface. Combined with the battery pack's liquid or air cooling systems, this significantly lowers the module's maximum temperature and temperature differentials.
The precisely clad localized nickel layer completely resolves the welding difficulties of pure copper. The nickel layer can stably absorb laser energy and provide appropriate contact resistance during resistance spot welding to generate a weld nugget. Test data shows that when using copper-nickel composites for cell spot welding, the weld pull force far exceeds industry standards. Furthermore, the weld spots are smooth and spatter-free, significantly improving the yield rate of multi-hole battery busbars on automated production lines.
Based on the excellent comprehensive performance mentioned above, customized precision copper-nickel bimetallic stamped parts have been widely applied in the following cutting-edge fields:
Electric Vehicle (EV & HEV) Power Battery Packs: Serving as current collectors and busbars for multi-cell modules (such as 18650, 21700, and 4680 large cylindrical cells), providing vibration-resistant, high-current physical connections.
Energy Storage Systems (ESS): Ensuring connection stability and extremely low heat generation over long lifecycles in high-voltage, large-capacity energy storage cabinets.
Light Motive Power and Micro-Mobility (E-bikes & Power Tools): Providing compact and efficient conductive connection solutions for space-constrained battery packs.
Through ingenious structural design and advanced cladding processes, copper-nickel bimetallic composites successfully achieve the perfect unification of "high electrical and thermal conductivity" and "high-reliability welding." It overcomes the inherent limitations of single-metal materials in engineering applications, providing vast degrees of freedom for the design of high-energy-density, high-power battery modules. In the future, with the further improvement of roll cladding precision and the maturation of localized nickel inlay and specialized stamping technologies, copper-nickel bimetallic connectors will inevitably play an even more irreplaceable cornerstone role in the global new energy supply chain.
