Carbon-Supported Nickel Selenide Hollow Nanowires as Advanced Anode Materials for Sodium-Ion Batteries

Carbon-supported nickel selenide (Ni_0.85 Se/C) hollow nanowires are prepared from carbon-coated selenium nanowires via a self-templating hydrothermal method, by first dissolving selenium in the Se/C nanowires in hydrazine, allowing it to diffuse out of the carbon layer, and then reacting with nickel ions into Ni_0.85 Se nanoplates on the outer surface of the carbon. Ni_0.85 Se/C hollow nanowires are employed as anode materials for sodium-ion batteries, and their electrochemical performance is evaluated via the cyclic voltammetry and electrochemical impedance spectroscopy combined with ex situ X-ray photoelectron spectroscopy and X-ray diffraction measurements. It is found that Ni_0.85 Se/C hollow nanowires exhibit greatly enhanced cycle stability and rate capability as compared to Ni_0.85 Se nanoparticles, with a reversible capacity around 390 mA h g^-1 (the theoretical capacity is 416 mA h g^-1 ) at the rate of 0.2 C and 97% capacity retention after 100 cycles. When the current rate is raised to 5 C, they still deliver capacity of 219 mA h g^-1 . The synthetic methodology introduced here is general and can easily be applied to building similar structures for other metal selenides in the future.