Boosting Zn-ion storage capacity of pitch coke-based activated carbon via pre-oxidation assisted KOH activation strategy

Activated carbons (ACs) with unique structure are desired for high-performance of Zinc-ion supercapacitors (ZICs). Herein, a series of ACs were prepared using air pre-oxidation assisted KOH activation technology from pitch coke (PHC). The results show that pre-oxidation promotes the development of pore and the regulation of surface chemical composition of obtained ACs. Based on this experiment, the as-prepared AC-330 delivers suitable oxygen functional groups, high specific surface area of 3223 m2 g−1 and high small-sized mesopore (2–4 nm) volume of 0.72 cm3 g−1. All these unique structures endow AC-330 with a satisfactory specific capacity of 212.5 mAh g−1 at 0.1 A g−1, and it can still remain at 85 mAh g−1 even when the current density increased up to 20 A g−1 with an excellent capacity retention of 40%. Fortunately, it can also deliver high energy-power density parameters (170 Wh kg−1 at 170.4 W kg−1 and 67.2 Wh kg−1 at 32.3 kW kg−1).