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.

Automated summary

Binder-free electrodes made of a hybrid metal oxide composed of graphene oxide have been successfully prepared, showing excellent electrochemical performance, high specific capacitance, promising rate performance, relatively high energy density, and long cycle life, making them a potential candidate for energy storage applications.