In Situ Optical Investigations of Lithium Depositions on Pristine and Aged Lithium Metal Electrodes
Hannes Kühnle, Edwin Knobbe, Egbert Figgemeier, Journal of the Electrochemical Society, Vol. 168, February 2021.
A custom-designed in situ optical cell is used to investigate the behavior of lithium (Li0) deposition in a symmetrical face-to-face setup. The experiment aims at monitoring the lithium deposition on both pristine and aged lithium foils, as a function of the waiting time between the lithium electrodes and the electrolyte (LP30: 1.0 M LiPF6 in EC: DMC (50/50 (v/v))). Constant current and electrochemical impedance spectroscopy measurements are applied at ~28 °C. The experiments show that lithium metal deposits in a wide range of morphologies, which are cataloged in terms of forms, structures, textures and colors for better visualization and improved analysis. Pristine lithium electrodes show tree-like deposition morphologies over the entire range of applied waiting times, but aged samples provided fibrous, and spheroidal forms as dominant lithium deposition morphologies at waiting times ≥ 24 h. Gas-treated metal foils (artificially aged by exposing pristine lithium to N2 at 25 °C for 1 h) showed a similar deposition behavior as the aged-over-time foils. The storage of lithium has a measurable influence on the deposition behavior on lithium foils. The obtained results help to further understand the lithium deposition behavior under different realistic conditions, which is for instance applicable to rechargeable lithium metal batteries.