Design principles of fluoroether solvents for lithium metal battery electrolytes unveiled by extensive molecular simulation and machine learning

Electrolyte engineering with fluoroethers as solvents offers promising potential for high-performance lithium metal batteries. Despite recent progresses achieved in designing and synthesizing novel fluoroether solvents, a systematic understanding of how fluorination patterns impact electrolyte performance is still lacking. We investigate the effects of fluorination patterns on properties of electrolytes using fluorinated 1,2-diethoxyethane (FDEE) as single solvents. By employing quantum calculations, molecular dynamics simulations, and interpretable machine learning, we establish significant correlations between fluorination patterns and electrolyte properties. Higher fluorination levels enhance FDEE stability but decrease conductivity. The symmetry of fluorination sites is critical for stability and viscosity, while exerting minimal influence on ionic conductivity. FDEEs with highly symmetric fluorination sites exhibit favorable viscosity, stability, and overall electrolyte performance. Conductivity primarily depends on lithium-anion dissociation or association. These findings provide design principles for rational fluoroether electrolyte design, emphasizing the trade-offs between stability, viscosity, and conductivity. Our work underscores the significance of considering fluorination patterns and molecular symmetry in the development of fluoroether-based electrolytes for advanced lithium batteries.