Energy-Dense Zinc\nIon Hybrid Supercapacitors\nwith S, N Dual-Doped Porous\nCarbon Nanocube Based Cathodes

Abstract

Zinc ion hybrid supercapacitors (ZIHSCs) are truly promising\nas\nnext-generation high-performance energy storage systems because they\ncould offer high energy density like batteries while exhibiting high\npower output and long cycle life traits of supercapacitors. The key\npoint of constructing a high-performance ZIHSC is to couple the Zn\nanode with an appropriate cathode material, which has high theoretical\ncapacity, cost-effectiveness, and intrinsic safety features. In this\nwork, we have demonstrated the potentiality of S, N co-doped porous\ncarbon nanocubes (S, N-CNCs) as a cathode material for devising a\nZIHSC with excellent energy density and cycle life. The S, N-CNCs\nare prepared from a zeolitic imidazolate framework (ZIF)-8 precursor\nvia a simultaneous pyrolyzing-doping strategy in an inert atmosphere.\nResultant CNCs are monodisperse with an average size of around 65\nnm and porous in nature, with uniform N and S doping throughout the\nstructure. Benefitted from such hierarchical porous architecture and\nthe presence of abundant heteroatoms, the assembled ZIHSC with S,\nN-CNC as the cathode and Zn-foil as the anode in a ZnSO₄ aqueous electrolyte could reach a specific capacity as high as 165.5\nmA h g^–1 (331 F g^–1) at 1 A g^–1, which corresponds to a satisfactory energy density\nof 148.9 W h kg^–1 at the power density of 900 W\nkg^–1. The ZIHSC has displayed a good cycle stability\nwith more than 70% capacity retention after 10,000 charge–discharge\ncycles. Furthermore, to verify the practical feasibility of such a\ncathode material, an aqueous 3D Zn@Cu//S, N-CNC full-cell device is\nfabricated, which has demonstrated a satisfactory specific capacity\n(49.6 mAh g^–1 at 0.25 A g^–1) and\nan impressive energy density (42.2 Wh kg^–1 with\n212.2 W kg^–1). Full ZIHSC devices are also found\nto be efficient in powering light-emitting diodes, further substantiating\ntheir feasibility in next-generation energy storage applications.