Pre-oxidation and catalytic carbonization strategies of hemp-derived multifunctional carbon for lithium-ion batteries/hybrid supercapacitors with high energy density and outstanding cyclability

Abstract

Biomass-derived carbons (biochar) materials have attracted enormous attention owing to their fabulous performances, inherent structural advantages and cost-effectiveness. Herein, two kinds of biochar electrode materials of porous carbon cathode (KCT-800) and graphitic carbon anode (K-1300) were respectively prepared from a single waste biomass hemp stem core. KCT-800 with uniform 3D hierarchical porous structure and abundant adsorption sites was fabricated via mild pre-oxidation of KNO3 and catalytic carbonization of potassium citrate, delivers a reversible capacity 105 mAh g−1 at 100 mA g−1 without obvious capacity degradation after 6000 cycles under 5 A g−1. In addition, K-1300 sheet-like graphitic carbon anode material was also prepared via simple pre-oxidation and high temperature calcination at 1300 °C, which exhibits a reversible capacity 463 mAh g−1 at 0.2 A g−1 because of the N/O Co-doping natural heteroatom and enhanced the pseudo-capacitance. Furthermore, the Li-ion hybrid supercapacitors were assembled by KCT-800 cathode and K-1300 anode delivers a stunning energy density of 222 Wh kg−1 at 246 W kg−1 with a superior capacity retention of 90 % after 4000 cycles. This strategy not only provides a facile and environmental benign method to prepare biomass-derived carbon materials, but also offers new insights on bio-sources multi-functional energy storage materials.