One-step fabrication of biomass-derived hierarchically porous carbon/MnO nanosheets composites for symmetric hybrid supercapacitor

In this work, hierarchically porous carbon/manganese monoxide nanosheets (HPC-MnO) composite materials are synthesized by a facile one-step approach, in which chemical activation of biomass precursor (wasted litchi shell) and loading of MnO nanosheets are conducted synchronously. The phase structure, chemical composition, morphology and specific surface area as well as the pores distribution are investigated for the resultant HPC-MnO composite materials. Interestingly, the as obtained HPC-MnO composite materials can serve both as the positive and negative electrodes simultaneously in a hybrid symmetric supercapacitor. High specific capaci-tances of 162.7F/g at a current density of 0.5 A/g and energy density of 57.7 W h/kg at a power density of 400 W/kg are obtained for the assembled symmetric HPC-MnO//HPC-MnO device, owing to the synergistic effects between electrochemical double-layer capacitance from the hierarchical porous carbons and pseudoca-pacitance from the redox reaction of manganese oxides. This work provides a facile and scalable strategy to synthesize carbon/metal oxides composites with promising electrochemical performances application for energy storage devices and opens a new gateway to design novel symmetric hybrid supercapacitors.