▎ 摘　　要

Graphene-like porous carbon nanosheets (GPCNs) have been proved to have great potential in high-rate performance supercapacitors. However, the relatively low specific capacitance and low working voltage of GPCN-based supercapacitors hinder their practical application in high-energy density devices. Herein, we demonstrate the direct deposition of MnO2 nanostructures onto the salvia splendens-derived GPCNs (GPCN-SS) surface through a hydrothermal method. The as fabricated MnO2/GPCN-SS composite possesses a relatively high specific surface area (483 m(2) g(-1)) and an appropriate mesopore size (2-5 nm). Thanks to the synergistic effect of GPCN-SS and MnO2 nanostructures, the MnO2/GPCN-SS composite electrode exhibits high specific capacitance of 438 F g(-1) at 0.5 A g(-1) (almost twice as high as the pristine GPCN-SS) and high rate capability (67.8% capacity retention at 50 A g(-1)) in the Na2SO4 electrolyte. More importantly, an asymmetric supercapacitor assembled with MnO2/GPCN-SS composite cathode and GPCN-SS anode in neutral electrolyte displays excellent rate capability (77.8% capacity retention from 0.5 to 50 A g(-1)) and high energy density (50.2 Wh kg(-1) at 516 W kg(-1)) Considering the abundance and sustainability of biomass-derived GPCNs along with the low-cost of MnO2, the MnO2/GPCNSS composite can serve as a promising new class of electrode materials for high-rate and high-energy density supercapacitors.