Garnet-Based Solid-State Lithium Fluoride Conversion Batteries Benefiting from Eutectic Interlayer of Superior Wettability

Garnet-type Li-La-Zr-O electrolytes suffer from poor contact with the Li metal anode because of the facile formation of a passivation layer at the interface, thus leading to frustrating interfacial impedance or lithium dendrite penetration. Herein, we introduce a eutectic Na-Li intermediate layer between the Li anode and garnet electrolyte to enable sufficient wettability. The potential mechanism of solid-solid convection between Li and Na domains promotes the prompt extension of the eutectic zone, preservation of the highly soldered interface, and homogenization of Li plating during cycling. The Li-Na/garnet/Na-Li cell exhibits a small interfacial resistance of 18.98 Omega.cm(2) at 60 degrees C and steady cycling for 3500 h (with a small overpotential of 10.8 mV). The first prototype of a solid-state battery combining a conversion-type FeF3 cathode with garnet electrolyte is successfully operated at 60 degrees C, with a high reversible capacity of 500 mAh.g(-1) and ultrastable cycling for 300 cycles at 100 mu A.cm(-2), as well as high-rate endurance up to 500 mu A.cm(-2).