Nitrogen and oxygen co-doped hierarchical porous carbon for zinc-ion hybrid capacitor

Heteroatom-doped porous carbon materials have shown great potential in energy storage devices. In this paper, the mixture of potassium polyacrylate and polyacrylamide was freeze-dried to obtain a precursor, followed by a one-step carbonization method to prepare nitrogen oxygen co-doped hierarchical porous carbon (HPC). The superior electrochemical properties of HPC-4 electrode could be attributed to the synergistic effects of the threedimensional (3D) interconnected hierarchical porous structure, high content of heteroatomic functional groups, and large specific surface area. The symmetrical supercapacitor assembled by two HPC-4 electrodes achieves an energy density of 21.13 Wh kg- 1 (100 W kg-1). More interestingly, the Zn//ZnSO4//HPC-4 hybrid capacitor constructed by HPC-4 as the cathode, zinc foil as the anode, and 2 M ZnSO4 as the electrolyte achieved an outstanding capacitance of 282.81 F g-1 (125.69 mAh g-1), an ultra-high energy density of 100.56 Wh kg- 1 (100 W kg- 1) and excellent cycle performance. This work provides a simple method for preparing highperformance electrode for zinc-ion hybrid capacitors.