Heteroatoms‐Doped Mesoporous Carbon Nanosheets with Dual Diffusion Pathways for Highly Efficient Potassium Ion Storage

Abstract

AbstractThe high potassization/depotassization energy barriers and lack of efficient ion diffusion pathways are two serious obstacles for carbon‐based materials to achieve satisfactory potassium ion storage performance. Herein, a facile and controllable one‐step exfoliation‐doping‐etching strategy is proposed to construct heteroatoms (N, O, and S)‐doped mesoporous few‐layer carbon nanosheets (NOS‐C). The mixed molten salts of KCl/K2SO4 are innovatively used as the exfoliators, dopants, and etching agents, which enable NOS‐C with expanded interlayer spacing and uniformly distributed mesopores with the adjusted electronic structure of surrounding carbon atoms, contributing efficient dual (vertical and horizontal) K‐ion diffusion pathways, low potassization/depotassization energy barriers and abundant active sites. Thus, the NOS anodes achieve a high reversible capacity of 516.8 mAh g−1 at 0.05 A g−1, superior rate capability of 202.8 mAh g−1 at 5 A g−1 and excellent long‐term cyclic stability, and their practical application potential is demonstrated by the assembled potassium‐ion full batteries. Moreover, a surface‐interlayer synergetic K+ storage mechanism is revealed by a combined theoretical and experimental approach including in situ EIS, in situ Raman, ex situ XPS, and SEM analysis. The proposed K+ storage mechanism and unique structural engineering provide a new pathway for potassium‐ion storage devices and even beyond.