Designing Si-based nanowall arrays by dynamic shadowing growth to tailor the performance of Li-ion battery anodes

To target the low conductance and stress issues of Si anodes for rechargeable Li-ion batteries, we have systematically designed four unique Si nanorod-based anodes using a dynamic shadowing growth method. Multilayer Cu/Si and Cu side-coated Si nanorods serve to improve the conductance, meanwhile, uniform CuSi and composition-graded CuSi nanocomposites serve to relax the stress and increase the conductance. Under the identical charge/discharge conditions, both the uniform and graded CuSi composite nanostructures exhibit the best cycling performance with capacity retention of 60-80% after 100 cycles of Li-ion insertion and extraction. The morphology evolution reveals that the nanorod wall-like structures remain intact in the uniform and graded CuSi composite anodes, while they have peeled off from the current collectors in the intrinsic Si, multilayer Cu/Si, and Cu side-coated Si samples. The morphological changes of different Si-based nanoanodes have also been modeled by a beam network, revealing that Si-based composite nanostructures generate a low yield stress which could be the key to developing high performance Li-ion battery anodes.