Lithiation‐Driven LiCrSe ₂ Shell Growth on Metallic CrSe ₂ Core Governs the Plateau–Slope Behavior

ABSTRACT The growing demand for high‐performance lithium‐ion batteries necessitates the development of cathode materials that combine high capacity, structural stability, and rapid charge–discharge capability. First‐principles calculations predict that layered CrSe ₂ possesses a robust framework capable of accommodating one Li ⁺ per formula unit while intrinsically supporting fast Li‐ion diffusion. Muon spin rotation (µ ⁺ SR) measurements validate this prediction, revealing fast Li ⁺ diffusion in pre‐lithiated CrSe ₂ . Consistent with these findings, electrochemical testing demonstrates a reversible capacity of 125.3 mAh g ⁻¹ at 0.1 C, approaching the theoretical value of 127.7 mAh g ⁻¹ , with stable cycling and good rate capability. In operando X‐ray diffraction and electrochemical impedance spectroscopy further reveal a reversible topotactic transition and a lithiation‐driven core‐shell evolution during cycling. These results show that lithiation‐induced conductivity changes govern the electrochemical behavior of CrSe ₂ , highlighting its potential as a high‐performance cathode for LIBs. This study provides new insight into intercalation processes in layered transition‐metal chalcogenides and informs the design of fast‐charging electrodes.