Nanostructure and phase engineering integration of amorphous Ni-Co sulfide/crystalline MnS/rGO cathode and ultra-small Fe2O3 nanodots/rGO anode for all-solid-state asymmetric supercapacitors

Engineering high-performance electrode materials is crucial to boost specific capacitance/energy of supercapacitors but challenging. Herein, amorphous Ni-Co sulfide/crystalline MnS and ultra-small Fe2O3 nanodots are skillfully integrated on reduced graphene oxide sheets to construct a-Ni-Co-S/c-MnS/rGO and Fe2O3 NDs/rGO, respectively. The integrated hybrid architectured a-Ni-Co-S/c-MnS/rGO cathode exhibits a high specific capacity of 1248 C g−1 at 2 A g−1 and long-term cyclic stability, induced by unique amorphous/crystalline heterophase nanostructure and electrical conductivity of rGO. Meanwhile, the resultant Fe2O3 NDs/rGO anode shows an impressive specific capacity of 734.2 C g−1 at 2 A g−1 with excellent rate capability (77.9%), which can be ascribed to unimpeded electron/ion diffusion pathways and abundant active sites endued by the nanodots-on-nanosheets structure of Fe2O3 NDs/rGO. Benefiting from the phase and nanostructure engineering integration, the all-solid-state asymmetric supercapacitor based on a-Ni-Co-S/c-MnS/rGO and Fe2O3 NDs/rGO shows a high specific energy of 42.0 Wh kg−1 at 793.8 W kg−1 and outstanding capacity retention (83.6% after 10,000 cycles).