From Microparticles to Nanowires and Back: Radical Transformations in Plated Li Metal Morphology Revealed via in situ scanning electron microscopy
Alexander Yulaev, Vladimir P. Oleshko, Paul M. Haney, Jialin Liu, Yue Qi, Talin Alec, Leite Marina, Andrei A. Kolmakov
Li metal is the preferred anode material for all-solid-state Li batteries due to its high theoretical capacity and low voltage vs. standard hydrogen electrode. However, stable plating and stripping of Li metal in contact with a solid electrolyte at high current density (>10 mA/cm2) remains a significant challenge. This problem originates due to formation of highly non-uniform dendritic morphology and penetration of the solid-state electrolyte by metallic Li filaments. To better understand the fundamental mechanism of Li metal plating, we use operando electron microscopy and Auger spectroscopy to probe nucleation, growth, and stripping of Li metal during electrochemical cycling of a solid-state Li battery as a function of current density and oxygen pressure. We find a linear correlation between the nucleation density of Li clusters and the charging rate, which agrees with a classical nucleation and growth model. Following nucleation, Li growth proceeds in the form of nanowires, a process promoted by the formation of a thin lithium oxide shell on the surface of the metallic Li by reaction with residual oxidizing gases in ultra-high vacuum. Surprisingly, we find that increasing the partial pressure of O2 to 10-5 Pa causes Li plating to proceed mostly by nucleation of 3D clusters, thus turning a mostly out-of-plane nanowire growth mode into an in-plane one. Our results further demonstrate the usefulness of operando scanning electron microscopy for characterizing solid-state electrochemical processes.
, Oleshko, V.
, Haney, P.
, Liu, J.
, Qi, Y.
, Alec, T.
, Marina, L.
and Kolmakov, A.
From Microparticles to Nanowires and Back: Radical Transformations in Plated Li Metal Morphology Revealed via <i>in situ</i> scanning electron microscopy, Nano Letters, [online], https://doi.org/10.1021/acs.nanolett.7b04518
(Accessed July 27, 2021)