Computational Investigation of Perfluorcarbonates as Multi-Functional Diluents in Localized High Concentration Electrolytes for Lithium Metal Batteries: Insights from MD and DFT Simulations

Abstract

Diluents play a vital role in the preparation of localized high concentration electrolytes (LHCEs) for 500 Wh kg-1 lithium metal batteries (LMBs). Although the current 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (TTE) -containing diluent electrolytes offer good performance, they still face challenges (e.g., side reactions with nickel-rich layered materials, gas production, and high volatility). Therefore, it is crucial to develop the next generation of diluents. In this study, a variety of solvents, including 4-fluoro-, 4,4-difluoro-, cis- and trans- 4,5-difluoro-, 4,4,5-trifluoro-, and 4,4,5,5-tetrafluoro-1,3-dioxolan-2-one (Tetra-FEC), and TTE, are analyzed using molecular dynamics (MD) simulations and density functional theory (DFT) calculations. Key physical and chemical properties are examined, including the densities, dielectric constant, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) values, binding energies with Li+, as well as adsorption and dissociation capability on the LiNiO2 cathodes. Further MD and DFT calculations on corresponding LHCE systems reveal densities, Li+ concentration, Li+ diffusion coefficients, solvation structures, and HOMO-LUMO levels of solvation clusters, highlighting the potential of Tetra-FEC as a promising diluent. Moreover, this study demonstrates a green research approach by utilizing MD and DFT calculations, eliminating the need for chemical experiments, which also showcases a viable process for future electrolyte research through artificial intelligence.