Synergistic Effect of Nitrogen-Sulfur Codoping on Honeycomb-like Carbon-Based High-Energy-Density Zinc-Ion Hybrid Supercapacitors

Zn-ion hybrid supercapacitors (ZHSCs) are emerging charge storage devices that inherit many of the advantages of supercapacitors and batteries. However, problems such as unsatisfactory cycling stability and low energy density need to be solved urgently, which can be accomplished by developing cathode materials with excellent properties. Herein, we report the development of performance-enhanced ZHSCs obtained by incorporating N and S heteroatoms into orange peel-based hierarchical porous carbon (NS-OPC) to facilitate Zn²⁺ adsorption. The results of ex situ photoelectron spectroscopy and X-ray diffraction demonstrated the presence of −OH and Zn²⁺ chemisorbed and Zn₄SO₄(OH)₆·5H₂O during charging and discharging, respectively. Density functional theory calculations show that double doping can promote the chemisorption/desorption kinetics of Zn²⁺ and thus promote the electrochemical charge storage of C materials. Impressively, when used to assemble ZHSCs, the device still has an energy density of 53.9 Wh kg^-1, a high power density of 6063.75 W kg^-1, and an 86.2% capacity retention after 10,000 cycles. This study not only provides a reasonable technique for developing superior C-based electrode materials but also contributes to the understanding of the charge storage process in heteroatom-doped C materials.