Confine, Defect, and Interface Manipulation of Fe₃Se₄/3D Graphene Targeting Fast and Stable Potassium‐Ion Storage

Abstract The fast electrochemical kinetics behavior and long cycling life have been the goals in developing anode materials for potassium ion batteries (PIBs). On account of high electron conductivity and theoretical capacity, transition metal selenides have been deemed as one of the promising anode materials for PIBs. Herein, a systematic structural manipulation strategy, pertaining to the confine of Fe₃Se₄ particles by 3D graphene and the dual phosphorus (P) doping to the Fe₃Se₄/3DG (DP‐Fe₃Se₄/3DG), has been proposed to fulfill the efficient potassium‐ion (K‐ion) evolution kinetics and thus boost the K‐ion storage performance. The theoretical calculation results demonstrate that the well‐designed dual P doping interface can effectively promote K‐ion adsorption behavior and provide a low energy barrier for K‐ion diffusion. The insertion‐conversion and adsorption mechanism for multi potassium storage behavior in DP‐Fe₃Se₄/3DG composite has been also deciphered by combining the in situ/ex situ X‐ray diffraction and operando Raman spectra evidences. As expected, the DP‐Fe₃Se₄/3DG anode exhibits superior rate capability (120.2 mA h g⁻¹ at 10 A g⁻¹) and outstanding cycling performance (157.9 mA h g⁻¹ after 1000 cycles at 5 A g⁻¹).