Understanding the dropping of lithium plating potential in carbonate electrolyte

Abstract

Lithium metal is an ideal anode material for high energy-density batteries owing to its high specific capacity and low redox potential. The carbonate-based electrolytes are attractive in developing high energy-density lithium metal batteries because of their wide electrochemical windows. However, the lithium deposition potential is often found dropping in the cells using the carbonate-based electrolytes, which may lead to overcharge as well as low energy conversion efficiency and low energy density of a full cell. Herein, the reason for the potential dropping in the commercial LiPF6-EC/DMC electrolyte is studied by both electrochemical evaluation and physical characterization (EC for ethylene carbonate and DMC for dimethyl carbonate). It is clarified that the repeated formation and decomposition of the organic species such as ROCO2Li and ROLi in the solid electrolyte interphase (SEI) layer during lithium plating/stripping cycling are responsible for the potential dropping. Our findings shed light on eliminating or suppressing the potential dropping to improve the energy density and the energy conversion efficiency of the secondary lithium metal batteries.