Engineering Pocket-Like Graphene–Shell Encapsulated FeS_2: Inhibiting Polysulfides Shuttle Effect in Potassium-Ion Batteries

摘要

Resource-rich FeS2 is a promising anode for potassium-ion batteries (PIBs). However, polysulfides emerge due to FeS2 conversion during discharging, which dissolve into the ether-based electrolyte and cause the continuous capacity degradation in PIBs. To address the polysulfides dissolution in PIBs, a graphene-shell-encapsulated FeS2 is fabricated and embedded in N/S codoped 3D hollow carbon spheres. As a protective pocket, the graphene-shell can effectively accommodate polysulfides inside the core-shell, inhibiting the polysulfides shuttle effect to enhance cycle stability of electrode. The density functional theory (DFT) calculations demonstrate that graphene-shells have a strong adsorption capacity for polysulfides, and the interfacial interaction between KFeS2 and graphene-shell can boost the K ion mobility. As a result, the composite exhibits superior-rate properties (524 and 224 mA h g(-1) at 0.1 and 8 A g(-1), respectively) and long-term cycle stability. This work demonstrates the promotion and protective effect of the graphene-shell for the FeS2 to storage K from both experimental and computational perspectives. These research outputs can provide guidance for designing other metal-based sulfide electrodes for PIBs.