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

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 Ni_0.6Co_0.4Se₂ 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 Ni_0.6Co_0.4Se₂ 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.