One-step synthesis of nanoblocks@nanoballs NiMnO3/Ni6MnO8 nanocomposites as electrode material for supercapacitors

Abstract

A novel nanoblocks@nanoballs NiMnO3/Ni6MnO8 electrode material was synthesized by one-step solvothermal–hydrothermal method, followed by thermal annealing. At the same time, electrode materials with different nanostructure were prepared by changing the volume ratio of deionied water and ethylene glycol. The results show that different structure has been gained including nanospheres, nanosheets and nanoblocks. When the deionied water: ethylene glycol = 1:1 (nanoblocks@nanoballs NiMnO3/Ni6MnO8 composite structure), the electrode material has a maximum specific surface area of 55.3 m2 g−1. The electrode material exhibited outstanding electrochemical performance with specific capacitance reached 494.4 F g−1 at a current density of 1 A g−1 as well as superior cycling performance of 88.0% capacitance retention after 5000 cycles at 3 A g−1. Such excellent performance was due to the synergistic effective between the Ni6MnO8 nanoballs and NiMnO3 nanoblocks. Nanoballs structure will increase in specific surface area and redox reaction active sites, and the blocks structure acts as a holder to improved the cycle performance. The NiMnO3/Ni6MnO8 become a promising candidate as next-generation electrode material for high-performance supercapacitors.