Mass Transfer during Electrodeposition and Dissolution of Li Metal within Highly Concentrated Electrolytes

Understanding the mechanisms of electro­deposition and dissolution of Li metal is necessary to control the morphological variations of Li metal anodes for next-generation batteries. Herein, the morphology of electro­deposited Li in a sulfolane-based highly concentrated electrolyte (HCE) and its correlation with the concentration profiles close to the electrodes were investigated. The decomposition of the solvent and anions on the electro­deposited Li surface caused significant changes in the morphology and solid electrolyte interphase layer thickness. During electrochemical dissolution, the Li+ surface concentration at the electrode became supersaturated, and the number of anions coordinated to Li+ increased at high current densities. The supersaturation state induced divergence of the electrode potentials. Therefore, the electrode reaction progress is correlated with the mass transfer within HCEs. Understanding the relationship between mass transfer and morphological variation in the Li metal electrode should promote the development of a strategy for using HCEs in Li metal batteries.