Conductive carbon spheres-supported nickel-cobalt selenide nanoparticles as a high-performance and long-life electrode for supercapacitors

The electrode materials with core-shell heterostructure draw researchers' attention in the fabrication of supercapacitors (SCs), which can reduce cost and prolong service lifespans. Herein, nickel-cobalt selenide nanoparticles, which are anchored on carbon microsphere to form core-shell heterostructure composite, exhibit excellent specific capacitance (960 F g−1) and superior cycling lifetime (85% after 2000 cycles). Furthermore, a new asymmetric supercapacitor (ASC) is created by utilizing C-20@(Ni, Co)0.85Se and AC as cathode and anode. The C-20@(Ni, Co)0.85Se//AC ASC exhibits the largest energy density of 34.44 W h kg−1 at a power density of 1125.23 W kg−1 and superior cycling lifetime with 81.5% of capacitance retention after 5000 cycles. Thus, C-20@(Ni, Co)0.85Se//AC ASC is known as potential electrode materials for ASC devices.