NMR Analysis of Weak Solvating Ester Electrolyte for High Voltage Sodium-Ion Batteries

As part of the development of lithium-alternative battery systems, ester electrolytes have been revealed to be promising for sodium-ion batteries. Various ethyl acetate (EA) solvated electrolytes of NaPF₆ salt and propylene carbonate (PC), PC/ethyl methyl carbonate (EMC), and PC/functionalized carbonate were developed by collaborators at University of North Carolina/Charlotte (Lin Ma and coworkers). Self-diffusion analysis using pulsed field gradient nuclear magnetic resonance spectroscopy elucidated transport properties of Na⁺ and PF6^- diffusion with promising ionic transference numbers at room temperature. NMR results have closely corroborated molecular dynamics (MD) simulations. In work conducted at UNC/Charlotte and the U.S. Army Research Laboratory, pouch cells with these electrolytes showed promising performance and capacity retention.