Oxygen-enriched pitch-derived hierarchically porous carbon toward boosted zinc-ion storage performance

The lack of cathode materials with satisfactory Zn²⁺ storage capability substantially hinders the realization of high-performance aqueous zinc-ion hybrid capacitors (ZHCs). Herein, we propose a facile KMnO₄ template-assisted KOH activation strategy to prepare a novel oxygen-enriched hierarchically porous carbon (HPC-1-4). This strategy efficiently converts coal tar pitch (CTP) into a well-tuned carbon material with a large specific surface area of 3019 m² g^-1 and a high oxygen content of 9.20 at%, which is conducive to providing rich active sites, rapid charge transport, and appreciable pseudocapacitance for Zn-ion storage. Thus, the as-fabricated HPC-1-4-based aqueous ZHC exhibits prominent performance, including a high gravimetric capacity (206.7 mAh g^-1 at 0.25 A g^-1), a remarkable energy density (153.4 Wh kg^-1 at 184.2 W kg^-1), and an impressive power output (15240 W kg^-1 at 63.5 Wh kg^-1). In-depth ex-situ characterizations indicate that the excellent electrochemical properties of ZHCs are due to the synergistic effect of the Zn²⁺ adsorption mechanism and reversible chemisorption. In addition, the assembled quasi-solid-state device demonstrates excellent electrochemical stability of up to 100% capacity retention over 50000 cycles, accompanied with a desirable energy density of 115.6 Wh kg^-1. The facile preparation method of converting CTP into carbonaceous functional materials has advanced the development of efficient and eco-friendly energy storage technologies.