Elucidation of Losses in Cycling Lithium-Metal Anodes in Ether-Based Electrolytes

Electrified-mobility and renewable-energy markets have undergone many developments in recent years and triggered an increase in demand for power-supply improvements, especially for full-electric vehicles (EVs). Rechargeable lithium-metal batteries have been considered one of the most attractive next-generation energy-storage systems (ESS). Many Li-chemistry-based ESS such as Li-S and Li-O₂ use liquid electrolyte based on ether solvents such as 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL) and tetraethylene glycol dimethyl ether (TEGDME) with bis(-trifluoromethanesulfonyl) imide (LiTFSI) as a salt. This work studied the effects of several parameters, in ether-based electrolytes, on the properties of the SEI and on capacity losses. The effects of LiNO₃ additive, current density and cycle number on the total capacity loss (Q_TL, Q_deposition—Q_dissolution), the capacity needed to repair the SEI after dissolution of lithium (Q_SEIrepair), two types of “dead” lithium, roundtrip coulombic efficiency and on the correlation among them, will be discussed. Elucidation of these phenomena will lead to the improvement of the lithium deposition/dissolution processes in lithium-metal rechargeable batteries. It was found that cells with 1:1 DME:DOL + 2 M LiTFSI and 0.15 M LiNO₃ electrolyte composition present the best cycling performance at low current densities, whereas under higher current conditions, the cell based on 1:1 DME:DOL + 2 M LiTFSI without the LiNO₃ additive, presents the best cycling performance.