Designing Ether-Based Electrolytes for Stable Lithium Metal Cycling at Low Temperatures

Abstract

The lithium metal anode is important for battery applications because of its promising electrochemical properties. However, its poor performance at low temperatures (below -20 °C) is one of the most challenging issues for practical battery applications. Herein, we designed a new ether-based electrolyte for improved lithium metal anode cycling at low temperature conditions and investigated its solvation behavior and the nature of the solid-electrolyte interphase (SEI). We combined the binary solvents 1,3-dioxolane (DOL) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TTE), along with a fluoroethylene carbonate (FEC) additive, to achieve high Coulombic efficiency (CE) at low temperature conditions (CE = 91.4% and 86.3% at -40 °C and -50 °C, respectively). Based on X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis, we found that TTE increased the interfacial decomposition of FEC and the counter-anion bis(trifluoromethane)sulfonimide (TFSI-), thereby helping to form a stable SEI layer for low temperature lithium cycling. Our findings provide engineering strategies for tailoring the SEI layer and desolvation energetics to enable more highly reversible Li electrodeposition at low temperature, and they are an advance toward improved operation of Li batteries at low temperatures.