Facile synthesis of nickel-cobalt selenide nanoparticles as battery-type electrode for all-solid-state asymmetric supercapacitors.

Transition metal selenides attract extensive attentions in the aspect of electrochemical energy storage due to the good conductivity and significant electrochemical activity. Herein, we develop a facile mothed to synthesize nickel cobalt selenides nanoparticles by hydrothermal approach. Benefiting from the synergistic effect between Co and Ni, the optimized Ni0.6Co0.4Se2 electrode shows a specific capacity of 602.6 C g-1 at 1 A g-1 and superior rate characteristic (468.5 C g-1 at 20 A g-1). More interestingly, an all-solid-state asymmetric supercapacitor was constructed utilizing the BNPC material as the negative electrode and the Ni0.6Co0.4Se2 samples as the positive electrode shows a high energy density of 42.1 Wh kg-1 and superior cycling stability (91.0% capacity maintenance after 5000 cycles) in KOH/PVA gel electrolyte. These exciting characteristics provide a new idea for the construction of transition metal selenide electrode materials for high performance supercapacitors.