Nickel-cobalt selenide nanosheets anchored on graphene for high performance all-solid-state asymmetric supercapacitors.

[Display omitted] • The NiCoSe/G-10 sample has a regular flower-like layered structure and is effectively combined with graphene oxide. • The NiCoSe/G-10 sample has high specific surface area, excellent specific capacitance, and good electrochemical stability. • Asymmetric supercapacitors have good electrochemical stability. Transition metal selenides in electrode material exploration for supercapacitors have drawn extensive interest because of their excellent conductivity and outstanding activity. Herein, nickel–cobalt selenide nanosheets anchored on graphene oxide (NiCoSe/G) were synthesized by water bath and selenization process. Graphene provides a continuous conductive network, on the one hand, the electrical conductivity of the material is effectively enhanced, and on the other hand, the volume and structure changes during the electrochemical reaction are well relieved. Benefiting from excellent electroconductivity and unique two-dimensional (2D) nanosheet structure, the optimized electrode (NiCoSe/G-10) exhibits a high specific capacity of 421.3 C/g (1 A/g) and an excellent cycling performance (after 5000 cycles) of 84.6 % capacity retention. Furthermore, the assembled NPC//NiCoSe/G-10 asymmetric supercapacitor achieves an excellent energy density of 40.4 Wh kg−1 at 533.3 W kg−1 and good capacity retention rate of 80.2 % after 5000 cycles. This paper provides a new strategy for the preparation of nickel–cobalt-based bimetallic selenides for supercapacitors with excellent characteristic. [ABSTRACT FROM AUTHOR]