Lignin-derived porous carbon for zinc-ion hybrid capacitor

Zinc ion capacitors (ZICs) are promising energy storage systems inheriting the characteristics of zinc ion batteries and supercapacitors. The development of high-performance, green and low-cost method for preparing carbon materials is essential for the development of ZICs. In this work, we report the fabrication of porous carbon from physical and chemical dual cross-linked lignin in a one-step pyrolysis process. The obtained porous carbon ZnLFK-PC demonstrates the highest specific capacitance of 333.0 F g−1 at 0.2 A g−1 with a capacitance retention of 59 % (from 0.2 to 20 A g−1). When used as the carbon cathode for ZIC, it shows the highest capacity of 123.7 mA h g−1 with an energy density of 97.8 Wh kg−1 at 0.5 A g−1. The electrochemical performance is superior to many other biomass-derived porous carbon cathodes. Moreover, the underlying mechanism is evaluated via impedance analysis. The utilization of lignin is of great importance for sustainable development, and this work presents an alternative practice of using lignin resource for high-performance ZICs.