Kun Liu, Xianhang Lu, Ming Hao, Yunhe Fu, Yuanhua Xie, Yaoshuai Ba, Dechun Ba, Northeastern University, Shenyang, China
The rapid advancement of electrically driven transportation and logistics systems, including low-altitude aircraft and new energy vehicles, has created strong demand for lithium-ion batteries that are lightweight, high specific energy, and safe. This study focuses on a new composite copper (Cu) foil with a sandwich structure comprising of a polymer substrate and surface Cu coating, which shows great potential for reducing battery weight, extending driving range, and improving safety. However, the high-efficiency, low-cost fabrication of such Cu coating remains a critical challenge for industrial adoption. Here, we propose a new fabrication process integrating vacuum evaporation deposition (VED) and electroplating. By investigating heat transfer mechanisms during VED and rationally designing key equipment components and process parameters, we effectively controlled the thermal exposure of polymer substrate while enhancing deposition efficiency and uniformity, enabling the fabrication of high‑performance composite Cu foils. Structural characterization using a four-point probe, X-ray diffraction, and uniaxial tensile tests confirmed: electrical conductivity (~5.2×10^⁷ S m^-1) comparable to pure Cu foil; excellent crystallinity of Cu coating; and mechanical strength meeting battery requirements. Electrochemical evaluation in half-batteries with composite Cu foil-graphite anodes revealed: cyclic voltammetry (scan rate 0.1 mV s^-1) displaying identical redox behavior to conventional electrodes, without no additional side-reaction peaks; stable reversible specific capacity >300 mAh g^-1 at 372 mA g^-1, and rate/cycling performance equivalent to traditional pure Cu foil. These results strongly demonstrate the material's outstanding electrochemical and structural stability, offering new insights and reliable technical support for practical application of next-generation high-performance lithium-ion batteries.