Lignin-Assisted Construction of Coal-Tar-Pitch-Derived N/S Co-doped Porous Carbon for Boosted Zinc Ion Storage

Zinc ion capacitors (ZICs) based on a carbon cathode represent new generation energy storage system, owing to outstanding safety, economic viability, and ecological sustainability. However, carbon-based cathodes suffer from limited charge storage. Thus, it is urgent to develop advanced carbon materials with a large available specific surface area and abundant active sites to boost the storage capacity of zinc ions. Herein, the lignin-assisted K2CO3 activation strategy is reported for constructing N/S co-doped hierarchical porous carbon frameworks (PCSs) using coal tar pitch as the primary carbon precursor. The pore-forming effect of K2CO3 coupled with the skeletal support of lignin promotes pyrolytic cross-linking of the precursor to form a porous nanosheet morphology. Meanwhile, N/S co-doping effectively modulates the electronic structure and produces additional active sites on the surface of PCSs. Besides, the reversible chemisorption/desorption of Zn2+ with O-containing groups occurring on PCSs has been monitored via in situ infrared spectroscopy, which provides additional pseudocapacitance. Consequently, the constructed ZICs with the PCS4 cathode can achieve a capacity of 125.31 mAh g-1 at 0.1 A g-1 and an energy density up to 96.43 Wh kg-1.