In this work, we demonstrate the synthesis of Ni–Li₂O@Si core–shell nanowall arrays through the lithiation of pre-synthesized NiO@Si core–shell nanowall arrays during the first lithium insertion process. When we control the potential window between 0.01–1.0 V, the electrochemically active NiO irreversibly reacts with Li to form Ni–Li₂O nanowall cores. These Ni–Li₂O cores function as both a stable mechanical support and an efficient electron conducting pathway in the later cycles while the coated Si shell functions as the active material during the charge and discharge process. The elaborately designed electrode shows better cycling and rate performance when acting as a lithium-ion battery anode compared to a planar Ni@Si electrode.