Abstract
The lithiation and delithiation process of silicon nanowire arrays (SiNWs) on silicon substrates has been studied with high-resolution electron microscopy. The composition of lithiated SiNWs was revealed, consisting of the unreacted crystalline silicon core and the reacted amorphous Li-Si shell. In particular, the Li-Si shell was comprised of a mixture of amorphous silicon oxide and crystalline silicon, leading to hindrance during Li-Si alloying/dealloying upon cycling.