Hybrid cobalt–manganese oxides prepared by ordered steps with a ternary nanosheet structure and its high performance as a binder-free electrode for energy storage†
Binder-free electrodes for supercapacitors have attracted much attention as no additive is required in their preparation processes. Herein, a hybrid metal oxide composed of graphene oxide (Co3O4/MnO2/GO) was successfully prepared. Briefly, electrochemical deposition and sintering were applied to grow Co3O4 nanosheets on nickel foam. Subsequently, MnO2 nanosheets were deposited on Co3O4 nanosheets via the thermal decomposition of a KMnO4 aqueous solution. Finally, graphene oxide was added to improve the performance of the composite. Particularly, the as-obtained Co3O4/MnO2/GO sample grown on nickel foam possessed a ternary nanosheet structure, and when applied as a binder-free electrode in a supercapacitor, it exhibited an excellent electrochemical performance. Firstly, the electrode exhibited an ultrahigh capacitance value of 2928 F g−1 at 1 A g−1 in a three-electrode system. Besides, the electrode showed a promising rate performance of 853 F g−1 at a high current density of 20 A g−1. Moreover, the electrode displayed a relatively high energy density of 97.92 W h kg−1 at a power density of 125 W kg−1 and long cycle life of 93% retention after 5000 cycles at 10 A g−1 in a two-electrode system. Thus, all the electrochemical tests suggest that the Co3O4/MnO2/GO binder-free electrode is a potential candidate for energy storage.