Electrochemical Polishing of Lithium Metal Surface for Highly Demanding Solid-Electrolyte Interphase

Abstract Lithium metal has shown great promise as an anode material for high‐energy rechargeable batteries. However, interfacial instability caused by an unstable solid‐electrolyte interphase (SEI) and dendrite growth has impeded the realization of Li anodes for practical applications. Recently, we reported a potentiostatic stripping−galvanostatic plating electrochemical polishing method to simultaneously create atomically flat Li and a molecularly smooth SEI, leading to a near‐perfect Li anodes that exhibit much enhanced electrochemical performance. In this paper, key factors including anodic stripping potentials, cathodic plating current densities, and types of salt and solvent systems are further investigated in detail based on the understanding of electrode reactions taking place during polishing. In particular, the importance of considerations on the mutual constrains between electropolishing and SEI formation and, thus, the necessity of fine control of potential and/or current is elucidated, which serves as a general rule for the successful application of electrochemical polishing of Li as well as other metals that involve the formation of SEIs.