N/F/S co-doped 3D interconnected carbon nanosheets with well-developed pores and interlayer spacing for high-performance potassium ion batteries

It is a big challenge to tune the structure and composition of carbon-based anode materials to increase the active sites by a green synthesis strategy for potassium ion batteries (PIBs). Herein, the N/F/S co-doped three-dimensional (3D) interconnected carbon nanosheets (NFS-CNSs) were synthesized from coal tar pitch (CTP) through a green and low-temperature treatment process for the first time. The as-obtained NFS-CNS 600 features 3D interconnected ultra-thin carbon nanosheets with abundant active sites, tunable N/F/S species, and enlarged carbon interlayer spacing. The density functional theory calculation results demonstrate that NFS-CNSs exhibit the highest electron density and most negative K + adsorption energy (–0.59 eV) compared to single or double-atom doping, thereby enhancing the storage performance of K + . As an anode for PIBs, the NFS-CNS 600 exhibits good cycle stability (98.2 % capacity retention after 200 cycles at 0.2 A g −1 ), high capacity (409.1 mAh g −1 at 0.05 A g −1 ) and rate performance (179.5 mAh g −1 at 5 A g −1 ). Besides, the NFS-CNS 600 anode also displays outstanding sodium storage performance. This work offers a green strategy to synthesize CTP-based anode materials from coal chemical by-products for high-performance PIBs.