Strongly vs. weakly associating anions: transport-structure relationship in LiTFSI-LiNO₃ electrolytes

Liquid battery electrolytes based on mixtures of salts with weakly and strongly associating anions have emerged as a promising route toward high-performance, sustainable battery technologies. Their success is primarily attributed to the unique influence of salt composition on the solvation structure. Here, we employ classical molecular dynamics simulations, corroborated by experimental data, to study mixed lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/lithium nitrate (LiNO₃) in diglyme electrolytes, a formulation of particular interest for lithium-sulfur and lithium-oxygen batteries. We investigate how the ratio of weakly associating anions (TFSI^-) to strongly associating anions (NO₃^-) affects ion transport within the electrolyte. Our findings reveal that the anion ratio significantly impacts both the solvation structure and the solvation dynamics, which together contribute to the distinct transport behavior observed in these systems. These findings underscore the tunability of battery electrolyte transport properties through careful mixing of anions.