Fluoride-substituted Li_6.4La₃Zr_1.4Ta_0.6O₁₂ with delocalized electron-share accelerates Li⁺ desolvation kinetics for high-voltage lithium metal batteries

Metallic lithium is regarded as the ideal anode material for high-specific-energy batteries. However, the Li(solvents) _x ⁺ formation in the liquid-state lithium metal batteries (LMBs) results in sluggish ion transport kinetics and continuous interface deterioration. Herein, an ion-kinetics promoter with delocalized-electron-sharing is designed to reduce the desolvation energy barrier, accelerate interfacial lithium diffusion, and achieve a stable interface. Specifically, the F-substituting Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (named as LLZTO _x F _y ) breaks the electron-confined state of the original metal-O (M-O). It induces electron redistribution at the central metal sites, thereby releasing more delocalized electrons. The relationships between charge transfer and ionic desolvation under the delocalized-electron-shared type promoter are comprehensively understood through theoretical calculations and in situ characterization. The F-substitution activates the O-M-F site activity of LLZTO _x F _y , thereby enhancing the binding of solvent C[double bond, length as m-dash]O bonds to these sites, resulting in a high Li⁺ transference number (0.68). Consequently, the lithium-lithium symmetric cell based on LLZTO_0.95F_0.05@PP can stabilize cycling for 1400 h with a lower overpotential (7.3 mV). Meanwhile, the Li|LLZTO_0.95F_0.05@PP|LiCoO₂ full cell can retain a high specific capacity of 88.2% after the 500th cycle at 1.0C under a high voltage of 4.6 V. Therefore, this strategy contributes to achieving long-cycle stability of anodes in LMBs.