New perspective to understand the effect of electrochemical prelithiation behaviors on silicon monoxide.

Electrochemical prelithiation is a facile, effective and extensively used method to improve the initial coulombic efficiency of SiO. However, much less research attention has been devoted to prelithiation effect on initial several cycles. Here, we introduce a new perspective to evaluate the prelithiation behaviors, which could understand in depth the electrochemical prelithiation behaviors and their effects on the following two cycles. Then X-ray photoelectron spectroscopy was further performed to pinpoint the reaction products. It has been found that the quantity of irreversible Li 4 SiO 4 , Li 2 O and SEI (Li 2 CO 3 and LiF) and reversible Li x Si are increasing as the prelithiation time extending. When the prelithiation time extending over 20 min, only alloy reaction of Si has been revealed. The regeneration of SEI discloses at least 7% capacity loss in the first cycle which depends on the prelithiated time. However, the reformation of SEI in the second cycles reveals 3% capacity loss. Because the coulombic efficiencies are independent on prelithiated time in the second cycle which indicates only one discharge/charge cycle is enough to form integrated SEI and adequate irreversible Li 4 SiO 4 and Li 2 O except part of unreactive SiO x .