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

Abstract

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 (QTL, Qdeposition—Qdissolution), the capacity needed to repair the SEI after dissolution of lithium (QSEIrepair), 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.