Synthesis of porous carbon spheres derived from lignin through a facile method for high performance supercapacitors

Porous carbon spheres (PCS) derived from lignin have been prepared through a facile method and fabricated as electrodes for electric double-layer capacitors. Spherical shaped mixtures of lignosulfonate and crystalized KOH are formed by spray drying of a solution of lignosulfonate and KOH. Activation by KOH is performed at high temperatures along with lignosulfonate carbonization. With an appropriate pore structure , the obtained PCS have a specific surface area of 1372.87   m 2   g −1 and show a capacitance of 340   F   g −1 in 3   M KOH at a current density of 0.5   A   g −1 . Moreover, a symmetric supercapacitor fabricated using the PCS as electrodes show a maximum capacitance of 68.5   F   g −1 , and an energy density of 9.7   W   h   kg −1 at a power density of 250   W   kg −1 . The capacity retention is more than 94.5% after 5000 galvanostatic charge-discharge cycles. The excellent characteristics seem to be ascribed to the pore structures of PCS that have a large specific surface area and a low electrical resistance.