Highly porous activated carbon derived from plant raw material as high-performance anode for aqueous sodium-ion supercapacitors

Abstract

High power sodium energy generation devices, such as symmetric and hybrid supercapacitors, have great potential for cheap and green post-lithium applications. However, it is imperative to obtain porous structures with large surfaces and optimized pore size to enhance the electrode sorption property and to ensure fast electrochemical reactions. In this work, we investigated the influence of KOH carbon activation conditions on the morphology, porosity, and electrochemical parameters in aqueous sodium electrolytes. Our activated carbon had a maximum surface area of 1556 m2/g and a notably high mesopore content, this varying from 5 to 19 % of the total pore area. Electrochemical parameters are not only influenced by the total number of pores, but also by the optimal ratio of meso and micro pores. It is shown that in the case of sodium-based electrolytes, mesopores provide good electrode-electrolyte contact, and the capacity is mainly provided by micropores. High operating values of activated carbon in sodium aqueous electrolytes (specific capacity about 78 F/g, energy density 11 W*h/kg and power density 470 W/kg) indicates that the optimal electrode materials for a high-power device are activated carbon with a high content of mesopores obtained by the ratio of C and KOH as 1:4.