Nitrogen-doped oxygen-rich porous carbon framework towards aqueous zinc ion hybrid capacitors and zinc-iodine batteries

Zinc ion hybrid capacitors (ZIHCs) and zinc-iodine batteries (ZIBs) have attracted significant attention as promising components for large-scale energy storage owing to their excellent security, environmental friendness and high theoretical capacity of Zn anode. However, there still exist some respective obstacles for commercial applications, such as limited specific capacity, poor cycling stability of ZIHCs or shuttle effect of polyiodide of ZIBs. Here, to enhance electrochemical properties, we report a synergistic one-step activation strategy using KMnO4 and Zn(NO3)2 for nitrogen-doped oxygen-rich three-dimensional hierarchical porous carbon (NOPC). Benefiting from its high specific surface area, three-dimensional porous morphology and improved redox sites from heteroatom doping, the as obtained NOPC exhibits desired electrochemical performance as cathode for ZIHCs and ZIBs. The NOPC-based electrode achieves an ultra-high specific capacity of 230 mAh g−1 at 0.1 A g−1, and 118 mAh g−1 can be maintained at 10 A g−1. Besides, a distinguished energy density of 213.0 Wh kg−1 and a high-power density of 11.2 kW kg−1 are also achieved with a constructed ZIHCs device. Furthermore, the NOPC/I2 composite exhibited excellent rate performance (54 mAh g−1 at 10 A g−1) and cycling performance (∼88.3 % retention upon 5000 cycles) in ZIBs device. This work provides a facile but effective strategy to develop 3D porous electrodes for ZIHCs and ZIBs with remarkable rate and cycling performance.