Revealing seed-mediated structural evolution of copper-silicide nanostructures: generating structured current collectors for rechargeable batteries

Metal silicide thin films and nanostructures typically employed in electronics have recently gained significant attention in battery technology, where they are used as active or inactive materials. However, unlike thin films, the science behind the evolution of silicide nanostructures, especially 1D nanowires (NWs), is a key missing aspect. Cu_xSi_y nanostructures synthesized by solvent vapor growth technique are studied as a model system to gain insights into metal silicide formation. The temperature-dependent phase evolution of Cu_xSi_y structures proceeds from Cu>Cu_0.83Si_0.17>Cu₅Si>Cu₁₅Si₄. The role of Cu diffusion kinetics on the morphological progression of Cu silicides is studied, revealing that the growth of 1D metal silicide NWs proceeds through an in situ formed, Cu seed-mediated, self-catalytic process. The different Cu_xSi_y morphologies synthesized are utilized as structured current collectors for K-ion battery anodes. Sb deposited by thermal evaporation upon Cu₁₅Si₄ tripod NWs and cube architectures exhibit reversible alloying capacities of 477.3 and 477.6 mAh g⁻¹ at a C/5 rate. Furthermore, Sb deposited Cu₁₅Si₄ tripod NWs anode tested in Li-ion and Na-ion batteries demonstrate reversible capacities of ≈518 and 495 mAh g⁻¹.