Petaloid-shaped hierarchical porous carbon sub-microspheres derived from lignin for high-performance supercapacitor electrodes

In this study, alkali lignin (AL), a byproduct of the sulfate pulping process, is utilized as a precursor to synthesize hierarchical porous carbon sub-microspheres (HALCS) with high specific surface area through high shear homogenization and chemically activated carbonization. The implementation of high-speed mechanical shear effectively reduces the particle size of lignin, leading to the formation of sub-microparticles. HALCS with distinct grooves and petal-like structures are obtained through a chemical activation-assisted high-temperature carbonization process. HALCS exhibits a hierarchical pore structure comprising macropores, mesopores, and micropores, with a specific surface area reaching 898.8 m 2 /g and a pore volume of 0.634 cm 3 /g, significantly surpassing alkali lignin-derived carbon (ALC) produced under similar carbonization conditions. In the 1 M H 2 SO 4 electrolyte environment, HALCS exhibits a specific capacitance of 433 F/g at a current density of 0.8 A/g. Moreover, a symmetric supercapacitor based on HALCS achieves maximum energy density and corresponding power density values of 17.2 Wh/kg and 100 W/kg, respectively, while maintaining excellent cycling stability undergoing 5000 charge-discharge cycles. Consequently, this straightforward and environmentally friendly synthesis strategy for alkali lignin-derived hierarchical porous carbon sub-microspheres opens up new avenues for the utilization of carbon materials derived from biomass in high-performance energy storage devices.