In situ coating of NiO on Ni-silicide nanowires with roughened surfaces for improved electrochemical energy storage

Abstract

NiO layers were coated in situ onto Ni-silicide nanowires by an oxidation in air. The surface of the nanowires had been previously roughened by etching in HF solution. It is found that the roughened surface is very helpful to enhance the in situ coating ability of NiO on the nanowires. When the resulting samples were used as anodes for lithium-ion batteries, a high reversible capacity of 1.28 mA h cm⁻² was obtained for the surface-roughened nanowires with 30 min HF-treatment, which is 3 times higher than that of the nanowires without HF-treatment. The current density can reach up to 2.15 mA cm⁻² for the 60 min HF-treated and then oxidized nanowires, while the capacity is maintained at as high as 0.52 mA h cm⁻². The improved cyclic performance could be attributed to the roughened surface of the nanowires, which enhanced the coating ability of the NiO layers, and provided a porous structure that is of benefit to increase the area of the electrode/electrolyte interface for the adsorption of ions. In addition, the Ni-silicide nanowires can improve the electrode conductivity and act as a stable support for the NiO coating layers during cycling, making a positive contribution to the electrochemical performance.