Engineering Pocket‐Like Graphene–Shell Encapsulated FeS2: Inhibiting Polysulfides Shuttle Effect in Potassium‐Ion Batteries

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. A graphene–shell encapsulated FeS2 is fabricated and embedded in N/S co‐doped 3D hollow carbon spheres. The graphene–shell not only suppresses the shuttle effect of polysulfides, but also improves the mobility of K ions at the interface. As the anode of potassium‐ion batteries, this composite exhibits excellent rate performance and long‐term cycling stability.