Mixing solvothermal synthesis nickel selenide on the surface of graphene for high-efficiency asymmetric supercapacitors

•NiSe2 nanoparticles have been synthesized on graphene oxide nanosheets.•The NiSe2/rGO composite possesses a high specific capacity of 137.7 mA h g−1 (1A g−1).•NiSe2/rGO-20//AC ASC displays high energy density (33.13 Wh kg−1) at a power density (850 W kg−1).•NiSe2/rGO-20//AC ASC displays long cycle life (80 % after 10,000 cycles at 5 A g−1). Nickel selenide nanoparticles uniformly supported on graphene nanosheets to form NiSe2/rGO composites were prepared via one-step mixing solvothermal method. The NiSe2/rGO composite possesses a high specific capacity of 137.7 mA h g−1 (1A g−1) and displays an excellent rate property. Moreover, there are NiSe2/rGO-20 as electrode materials assembling asymmetric supercapacitors, which manifests high energy density (33.13 Wh kg−1) at a power density (850 W kg−1) and the capacity can maintain of 80 % after 10,000 cycles. Therefore, NiSe2/rGO composite can be a potential candidate for high-efficiency asymmetric supercapacitors.