Structural engineering of sulfur-doped carbon encapsulated bismuth sulfide core-shell structure for enhanced potassium storage performance

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.