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.