Targeted Functionalization of Cyclic Ether Solvents for Controlled Reactivity in High-Voltage Lithium Metal Batteries

Understanding the degradation pathways and reactivityof electrolytesis the key to address the shortcomings of conventional electrolytesand to develop new electrolytes for high-voltage lithium metal batteries(LMBs). Accordingly, while 1,3-dioxolane (DOL) exhibits desired featuressuch as good compatibility with Li metal, low viscosity, and highionic conductivity, it suffers from poor oxidation stability, mainlyfrom its ring-opening polymerization. In an effort to control thereactivity of DOL by tuning its electronic properties, we introducedmethyl and trifluoromethyl groups to the ethyl moiety of DOL and developed4-methyl-1,3-dioxolane (MDOL) and 4-(trifluoromethyl)-1,3-dioxolane(TFDOL) as solvents, respectively. Whereas the MDOL-based electrolyteexhibited serious side reactions toward metallic Li, the TFDOL-basedelectrolyte showed oxidation stability up to 5.0 V. Moreover, theinorganic-rich solid electrolyte interphase induced by the weak solvationpower of TFDOL along with high oxidation stability enabled a robustcycling stability in a Li|NCM811 full cell (20 & mu;m Li foil, N/Pratio of 2.5).