Fluoride-substituted Li6.4La3Zr1.4Ta0.6O12 with Delocalized Electron-Share Accelerates Li+ Desolvation Kinetics for High-voltage Lithium Metal Batteries

Abstract

Metallic lithium is regarded as the ideal anode for the high-specific-energy battery.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-share is designed to reduce the desolvation energy barrier, accelerate the interfacial lithium diffusion and achieve the stable interface. Specifically, the F-substituting Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (named as LLZTO x F y ) breaks the electron-confined state of the original metal-O (M-O) and induces the electron-redistribution of the central metal sites, thus releasing more delocalized electrons. The relationships between charge transfer and ionic desolvation under the delocalized-electron-shared type promoter are deeply understood from theoretical calculations to in-situ characterizations. The F-substituting activates the O-M-F site activity of the LLZTO x F y , which enhance binding of C=O bond in solvent molecules to these sites, realizing a high Li + transference number (0.68). Consequently, the lithium-lithium symmetric cell based on LLZTO 0.95 F 0.05 @PP can stabilize cycling for 1400 h with a lower overpotential (7.3 mV). Meanwhile, the Li|LLZTO 0.95 F 0.05 @PP|LiCoO 2 full cell can retain a high specific capacity of 88.2% after 500 th at 1.0 C under the high-voltage of 4.6 V. Therefore, this strategy contributes to achieving long-cycle stability of anodes in LMBs.