Air stable lithium microspheres prelithiation reagents for Li-ion batteries synthesized via electroplating

Abstract Prelithiation is a critical strategy in lithium-ion batteries (LIBs) to compensate the active lithium loss due to the low Coulombic efficiency (CE) caused by the formation of solid electrolyte interphase. The scarce of suitable prelithiation reagents impedes the applications of prelithiation in LIBs. Herein, ultra-fine air stable lithium spheres (ASLSs) comprised of a metallic lithium core and a LiF/Li2O shell are produced via a facile electrochemical plating technique. The LiF/Li2O shell efficiently protects the ASLSs in air, and the uniform small size endows the ASLSs high prelithiation performance for anodes such as graphite, SiO@C and Sn@C. The CE of the ASLSs prelithiated graphite electrode (PG) is improved from 77.4% to 101.9%. The energy density of the PG/LiCoO2 full cell is significantly improved. The ASLSs prelithiated SiO@C and Sn@C electrodes also significantly improve the first-cycle CEs. In-situ transmission electron microscopy studies indicate that stress induced creep of metallic lithium plays the dominant role in the formation of well-defined ASLSs. This study provides a simple technique to synthesize an efficient prelithiation reagent for LIBs.