Oxygen-rich lotus-shaped porous carbon cathode for high areal capacity zinc ion hybrid capacitors

Herein, the oxygen-rich lotus-shaped porous carbon (OLPC) cathode for high areal performance zinc ion hybrid capacitors (ZHCs) are synthesized by using phenanthrene as carbon precursor coupled with potassium oxalate activation. The OLPC presents high content of oxygen, which improves the surface wettability of OLPC in aqueous electrolyte, Zn-ion chemical adsorption and pseudocapacitive redox active sites. The OLPC cathode displays a superior areal capacity of 1688.5 mF cm−2 at 0.215 mA cm−2, superb rate capability of 1370.6 mF cm−2 at 86 mA cm−2, remarkable areal energy density of 686.6 mWh cm−2 and long-term life with 1.1% loss after 20,000 cycles. This work provides an effective strategy for improving the ions storage properties by surface functionalization of electrode materials.