Modulating pore nanostructure coupled with N/O doping towards competitive coal tar pitch-based carbon cathode for aqueous Zn-ion storage

Abstract

Cathode materials with limited active sites to accommodate Zn2+ ions substantially hamper the development of high-performance aqueous Zn-ion hybrid capacitors (ZHCs). Thus, the dedicated design of cathode materials is pivotal for preparing high power/energy density ZHCs. Here, a hierarchically porous coal tar pitch-derived carbon (NPC) cathode with abundant N/O doping (8.7 and 2.4 at.%) was prepared via a template strategy combined with chemical activation. The engineered hierarchically porous framework with optimal pore size distribution facilitates rapid Zn2+ ion transport, provides numerous active sites, and guarantees high adsorption-site accessibility. Moreover, the N/O doping further improves the transmission kinetics and adsorption capability of Zn2+ ions. Therefore, the aqueous ZHCs assembled with the NPC cathode show a high capacity of 158.2 mAh g−1 at 0.25 A g−1 and remarkable rate performance with a capacity of 73.5 mAh g−1 at 15 A g−1. Impressively, the NPC-based flexible device exhibits significant cycling durability with a capacity retention rate of up to 96.8 % over 10000 cycles at 10 A g−1 and a preeminent energy density of up to 112.1 Wh kg−1 at 203.0 W kg−1. This work provides new insights to design advanced coal tar pitch-based carbon materials for superior ZHCs.