Mn3O4 nanoflakes/rGO composites with moderate pore size and (O=)C-O-Mn bond for enhanced supercapacitor performance

Abstract Moderate pore size and (O = )C-O-Mn bonds are designed in Mn3O4 nanoflakes/reduced graphene oxide composites to enhance the specific capacitance and cycling performance of electrodes for supercapacitors. Manganese oxide nanoflakes grow on the surface of graphene oxides via chemical precipitation. After annealing, (O = )C-O-Mn bonds are formed between Mn3O4 and graphene to enhance structural stability of electrode materials. Moreover, the pore size in Mn3O4 enlarges with the increased annealing temperature driven by phase transition and lattice reforming. The moderate pore size of 5–10 nm in Mn3O4 contributes to electrolyte ion diffusion and improves the capacitive-controlled energy storage. In three-electrode system, Mn3O4 nanoflakes/reduced graphene oxide composites with optimal pore size of 5–10 nm and (O = )C-O-Mn bond deliver high specific capacitance (351 F g−1 at 0.5 A g−1) and good cycling performance (80.1% of maximum capacitance after 10,000 cycles). To probe practical applications, Mn3O4 nanoflakes/reduced graphene oxide composites and active carbon are employed as positive electrode and negative electrode, respectively, to assemble asymmetrical supercapacitors. This asymmetrical supercapacitor demonstrates high energy density (36.76 W h kg−1) and good cycling performance (93.5% after 5000 cycles).