3D Porous Biomass Derived Carbon Composite Modified with (Ni,Co)Se Particles for High‐Performance Supercapacitors

Abstract Modification with transition metal compounds is an effective strategy to improve the capacitance of biomass derived carbon. In this work, high‐performance (Ni,Co)Se/banana leaves derived carbon ((Ni,Co)Se/BLC) composite with 3D porous structure was prepared by two‐step carbonization and subsequent hydrothermal reaction process. The prepared (Ni,Co)Se/BLC exhibits a high specific capacitance of 840.6 F/g at a current density of 1 A/g, which is more than five times comparing with the carbon matrix. Asymmetric supercapacitor, assembled with the (Ni,Co)Se/BLC composite as the positive electrode and BLC as the negative electrode, exhibits a wide potential window of 1.5 V, delivers a high energy density of 34.3 Wh/kg at a power density of 749.8 W/kg, and the power density can reach 7500 W/kg at the energy density of 19.4 Wh/kg. The results reveal that the modification of metal selenide can greatly improve the electrochemical properties of biomass derived carbon, which is significant for the application of biowaste in supercapacitor electrode materials.