FeO nanospheres in situ decorated graphene as high-performance anode for asymmetric supercapacitor with impressive energy density.

Unique nanostructure, high electrical conductivity, satisfactory energy density, and extraordinary cycling stability are important evaluation criteria for high-efficient energy storage devices. Herein, FeO nanospheres are successfully in situ decorated on graphene nanosheets through an environmentally benign and facile solvothermal procedure. When utilized as an electrode for supercapacitor, the graphene/FeO nanocomposite exhibits a notably enhanced specific capacity (268 F·g at 2 mV·s) and remarkable cycling performance with 98.9% capacity retention after 10,000 cycles. Furthermore, the fabricated graphene/MnO//graphene/FeO asymmetric supercapacitor device displays a desirable energy density (87.6 Wh·kg) and superior cycling stability (93.1% capacity retention after 10,000 cycles).