Substrate Engineering for High-Performance Ultrathin Copper Foils: Unveiling the Electronic-Geometric Synergy of Low-Range-Order Ni-W Alloys

The precise regulation of microstructure and mechanical properties in ultrathin electrodeposited copper foils is critical for advanced interconnections yet remains constrained by the strength-ductility trade-off. While electrolyte additive engineering is common, the regulation mechanism of substrate intrinsic physicochemical properties remains elusive. Herein, a “substrate engineering” strategy is established by investigating copper nucleation thermodynamics and growth kinetics on low-range-order Ni-W versus crystalline Ti substrates. Combined DFT calculations and multi-scale characterizations reveal a unique electronic-geometric synergistic effect of the low-range-order Ni-W: its optimized work function alignment lowers the interfacial energy barrier for electron transfer, while the low-range-order structure provides abundant high-activity sites. This mechanism reduces the nucleation barrier, inducing a transition from island-like coarsening on Ti to high-density instantaneous nucleation and uniform planar growth on Ni-W. Consequently, the resulting foil exhibits a densely smooth surface (S_a = 0.11 µm), refined grain structure, and optimized (220) texture. These merits yield a significant strength-ductility synergy, with tensile strength and elongation reaching 292.4 MPa and 2.88%, respectively. This work provides a theoretical basis for designing next-generation high-performance copper foils beyond traditional additive reliance.