NMR for liquid battery electrolytes: Structure, motion, and heterogeneity

Liquid electrolytes play a central role in batteries because they set the local states from which interfacial chemistry begins. They are often described through formulation labels such as solvent class, salt identity, additive choice, or concentration regime. These descriptors provide a necessary starting point, but they do not fully represent the states that enter interfacial chemistry. In many systems, electrolyte behavior depends not only on local coordination motifs, but also on their renewal in time and, in more complex formulations, on the coexistence of multiple local states and response regimes within the same formulation. This Perspective organizes that problem through NMR across three connected levels: microscopic structure, microscopic motion, and dynamic complexity or heterogeneity. In this framework, microscopic structure extends beyond a first-shell solvation picture, and microscopic motion extends beyond diffusion alone. Many practical electrolytes also cannot be represented by one dominant structural condition and one dominant response timescale. The aim is to provide a practical layered description that relates NMR-detected states more directly to electrolyte interpretation and battery design.