Rational constructing free-standing Se doped nickel-cobalt sulfides nanotubes as battery-type electrode for high-performance supercapattery

The electrochemical performance of nanostructured nickel-cobalt sulfides is greatly limited by the sluggish reaction kinetics and limited electroactive sites. Herein, we design and synthesize free-standing Se doped nickel cobalt sulfides with controllable-component directly on carbon cloth, which involves the hydrothermal process and sulfuration/selenylation reaction. Serving as free-standing electrode, as-synthesized Se doped nickel-cobalt sulfides not only favor the fast ion diffusion path and low contact resistance, but also provide rich electroactive sites with electrolyte. More importantly, proper Se doping in nickel-cobalt sulfides greatly increases the electrochemically active surface area and reduces the charge transfer resistance. Based on the X-ray photoelectron spectroscopy and transmission electron microscopy results, the reaction mechanism is convincingly revealed that Se dopants have been changed into SeOx. And electrochemical activated oxyhydroxides are mainly involved in electrochemical reactions. As a result, as-fabricated Se doped nickel-cobalt sulfides show a good electrochemical performance for supercapattery. Further, the supercapattery device is also assembled by using nickel-cobalt sulfide/selenide as positive electrode and activated carbon as negative electrode, which shows a high energy density of 39.6 Wh kg(-1) at the power density of 1501 W kg(-1).