Si/Ge core–shell nanoarrays as the anode material for 3D lithium ion batteries

The rapid development of small scale electronic devices, such as M/NEMS devices, smart dust, micro or nano bio-sensors and so on, is leading to the urgent need for micro or nano power sources with the possibility for integration. In this work, 3D Si/Ge composite nanorod (NR) arrays were fabricated on wafer-scale Si substrates as anode materials in micro or nano Li ion batteries (LIBs) by a low cost, simple and Si-compatible process. Significantly improved capacities and cycling performances were accomplished in the optimized 3D Si/Ge composite NR array electrode by successfully addressing the volume expansion and conductivity issues. Further theoretical calculations gain more insights into the origins of the improved electrochemical properties by considering the adsorption and diffusion energies of Li ion in Si and Si/Ge unit cells. This study technically and fundamentally provides a perspective idea for practical applications of wafer-scale Si substrates in LIBs with the aim of supplying integrated power for micro or nano scale electronic devices.