Electrochemical polishing of Li metal from the corrosion science perspective is proposed.

What is it about?

Dendritic growth of lithium (Li), well-known originating from deposition on rough and inhomogeneous Li-metal surface, has long been a central problem in charging lithium metal batteries. Herein, we propose the concept of electrochemical polishing of Li metal and even dynamic stabilization of thea homogeneous solid electrolyte interphase (SEI) during the selective current density by judicious balance between protective and corrosive features of a dual functional electrolyte. Lithium nitrate (LiNO3) was adopted as the primary electrolyte salt because it forms a relatively homogeneous SEI with lithium oxide (Li2O) as the dominant component. Li halides (LiX; X = Cl, Br, I), are used as a secondary salt. Corrosive effect of LiX is expected to provide a polished Li electrode with microscopically smooth surface.

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Why is it important?

Li metal can provide or dynamically maintain an ideal smooth SEI film with the appropriate thickness (thinner on the convex and thicker on the concave part of Li surface), which facilitate the protrusion of Li first dissolved due to the high Li-ion conductivity of the thinner SEI film. the use of this bi-functional electrolyte in Li metal batteries provides a dynamic protection/corrosion of Li-surface which demonstrates a unique approach toward maintaining a homogeneous, smooth SEI during repeated long cycles. More importantly, in contrast to the high concentration fluorine-rich electrolytes used for improved performance of LMBs, we have formulated a fluorine-free more practical concentration (~1.1 M) electrolyte that, we believe, should be more industrially relevant and may open up other possibilities in search of new electrolytes for long-life rechargeable LMBs.