Turning Residual Lithium Compounds into a Fluorinated Interface for a Water-Stable, Industrializable Prelithiated Micron-SiOx Anode

The implementation of carbon-coated microsized SiO_x (MSiO_x@C) materials in high energy density lithium-ion batteries (LIBs) is challenged by their low initial Coulombic efficiency (ICE), large volume expansion, and limited cycle life. Even though prelithiation is an effective strategy to enhance ICE, it will make the prelithiated MSiO_x@C (Li-MSiO_x@C) extremely sensitive to moisture. For industrial applications, it is important to develop chemically and electrochemically stable Li-MSiO_x@C with high ICE and good cycling performance. Herein, a convenient interfacial design was employed to construct in situ a functional lithium fluoride (LiF) layer on the surface of the Li-MSiO_x@C material (Li-MSiO_x@C@LiF). LiF could serve as a physical protective layer to prevent the side reactions of Li-MSiO_x@C@LiF in water and participate in the formation of a robust LiF-rich solid-electrolyte interphase for the Li-MSiO_x@C@LiF anode during cycling. Finally, Li-MSiO_x@C@LiF shows excellent water compatibility, high ICE (90.62%), high reversible capacity (1356.5 mA h g^-1) in a half-cell, and excellent cycling stability (80.3% capacity retention after 1000 cycles) in a 14.2 A h pouch cell with an energy density of 305 W h kg^-1. The proposed interfacial design would be promising to stabilize Li-MSiO_x@C anodes and thus promote their practical application in high energy density LIBs.