Decomposition of ethylene carbonate on electrodeposited metal thin film anode

摘要

Metals capable of forming alloys with Li are of great interest as an alternative to present carbon electrodes, hence the importance of knowing their interactions with electrolytes is necessary. Herein we report further on the high-voltage extra irreversibility of Sn electrodeposited thin films vs. Li in EC-DMC 1 M LiPF_6 electrolytes. We show that this high-voltage irreversibility is strongly dependent upon the electrolyte composition as demonstrated by its disappearance in EC-free electrolytes. This finding coupled with IR spectroscopy measurements provides direct evidence for the tin-driven catalytic degradation of EC during the discharge of Sn/Li cells. From an electrochemical survey of various metals, capable of alloying with Li, we found that Bi and Pb behaved like Sn while Si and Sb did not act as catalysts towards EC degradation. A rationale for such behaviour is proposed, a procedure to bypass EC degradation with the addition of VC is presented, and an explanation for the non-observance of catalytic-driven EC degradation for Sn/C composites is provided.