Exploring Chlorinated Solvents as Electrolytes for Lithium Metal Batteries: A DFT and MD Study

Abstract

Electrolytes with fluorinated solvents have been regarded as a promising strategy to stabilize high-voltage cathodes and the interphase of lithium anode in lithium metal batteries (LMBs). However, the rigorous synthesis approach and high cost have led to a demand for developing cost-effective solvents with suitable properties for LMBs. Herein, we explored the possibility of using chlorinate solvents as electrolytes using density functional theory (DFT) and classical molecular dynamics (MD) simulation. Taking ether (1,2-dimethoxyethane [DME], 1,3-dioxolane [DOL]), carbonate (dimethyl carbonate [DMC], and ethylene carbonate [EC]) as examples, we first compared the energy variation of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) upon Cl and F substitution. In particular, we found that 1,2-bis(chloromethoxy)ethane (DME-2Cl-2) has the lowest HOMO and the highest LUMO level among the chlorinated DME after coordinating with Li⁺, enabling a potentially wide voltage stability. Further MD simulation reveals that lithium ions in DME-2Cl-2 has a weaker solvation coordination with solvents but stronger interaction with anions than DME and 1,2-bis(Fluoromethoxy)ethane (DME-2F-2), which is more beneficial for forming stable anion-derived solid electrolyte interphase (SEI). Our findings suggest that chlorinated solvents can be used as promising electrolytes for LMBs.