Decorating Cobalt Selenide Nanoparticles on Polypyrrole Nanowires As Nanocomposite Electrodes for Hybrid Supercapacitors

Cobalt selenide electrode materials for hybrid supercapacitors (HSCs) still suffer from the unsatisfactory rate performance and cyclic stability thanks to their limited electrical conductivity and poor structural stability. To address these issues, we here report on the construction of polypyrrole (PPy)@Co0.85Se nanocomposites that grow on Ni foam by a two-step electrochemical synthesis method. In such nanocomposites, well dispersed Co0.85Se nanoparticles are decorated on conductive PPy nanowires, which are featured by enhanced electrical conductivity, rich electroactive sites, easy adsorption/desorption and diffusion of electrolyte ions, and good mechanical stability. As a result, the obtained PPy@Co0.85Se nanocomposites give a maximum specific capacity of 827 C g-1 at 1 A/g, a capacity retention of 67 % at 20 A/g, and an initial capacity retention of 93 % after 5000 cycles at 10 A/g. Furthermore, a two-electrode HSC device is assembled with PPy@Co0.85Se as the pos-itive electrode, which demonstrates an energy density of 51.9 Wh kg-1 at a power density of 812 W kg-1 as well as an initial capacity retention of 96 % after 5000 cycles at 5 A/g. These results showcase a great potential for future application of the synthesized PPy@Co0.85Se nanocomposites in HSCs, and our work may provide an efficient strategy for engineering other metal selenide-based electrode materials for HSCs.