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Owing to the high theoretical capacity, metal sulfides have emerged as promising anode materials for potassium-ion batteries (PIBs). However, sluggish kinetics, drastic volume expansion, and polysulfide dissolution during charge/discharge result in unsatisfactory electrochemical performance. Herein, we design a core-shell structure consisting of an active bismuth sulfide core and a highly conductive sulfur-doped carbon shell (Bi2S3@SC) as a novel anode material for PIBs. Benefiting from its unique core-shell structure, this Bi2S3@SC is endowed with outstanding potassium storage performance with high specific capacity (626 mAhdg-1 under 50 mAdg-1) and excellent rate capability (268.9 mAhdg-1 at 1 Adg-1). More importantly, a Bi2S3@SC//KFe[Fe(CN)6] full cell is successfully fabricated, which achieves a high reversible capacity of 257 mAhdg-1 at 50 mAdg-1 over 50 cycles, holding great potentials in practical applications. Density functional theory (DFT) calculations reveal that potassium ions have a low diffusion barrier of 0.54 eV in Bi2S3 due to the weak van der Waals interactions between layers. This work heralds a promising strategy in the structural design of high-performance anode materials for PIBs.
This study was supported by the Hong Kong Scholars Program (No. XJ2019022), the Fundamental Research Funds for the Central Universities (No. WK2060000032), the National Natural Science Foundation (Nos. 51772283, 21972145, and 51872249), and General Research Fund (GRF, No. CityU 11307619). The DFT calculations were completed on the supercomputing system in the Supercomputing Center of the University of Science and Technology of China. We thank the Beamlines MCD-A and MCD-B (Soochow Beamline for Energy materials) at the National Synchrotron Radiation Laboratory (NSRL) in the University of Science and Technology of China for measuring XANES of sulfur L-edge.