Hydrothermal assisting biomass into a porous active carbon for high-performance supercapacitors

Abstract

Biomass contained significant amounts of lignin, cellulose and hemicellulose and these high crystallinity results in sub-optimal electrochemical properties. Herein, a hydrothermal method was employed to intentionally weaken the structural integrity of hemp fibers and eliminate cellulose impurities. After undergoing KOH activation, the resulting product achieved a maximum specific surface area of 1644.3 m2 g−1. In a three-electrode test, the specific capacitance of this electrode material was 255.6 F g−1 at a current density of 1 A g−1, representing a nearly double enhancement over the non-hydrothermally treated sample. Furthermore, the assembled symmetric supercapacitor has a specific capacitance of 56.9 F g−1 at 1 A g−1 and a capacitance retention of 102 % after 10,000 charge/discharge cycles (10 A g−1). Its maximum power density was 725 W kg−1 at an energy density of 16.6 Wh kg−1. The desirable capacitive properties indicated that the hydrothermal pretreatment method was expected to have wider applications in the preparation of other biomass-based electrode materials.