Vanadium redox flow batteries (VRBs) have gaining interest as electric grid-level stationary energy storage system because of their high safety, long-term cycling, and capability to store and release a large amount of energy in a controlled manner1. Although large scale (megawatt hour) installations have been demonstrated, this technology is still facing significant operational limitations dictated by solubility and thermal stability of catholyte (V4+/5+) and anolyte (V3+/2+) of the vanadium electrolyte solutions.2-3 At the molecular level, stability of vanadium species depends on its evolving solvation structure emerging from multitude of solvent and counter ion interactions. We have utilized multinuclear NMR approach, including 51V, 33S, 17O and 35Cl and 31P, to map the vanadium solvation structure and dynamics over a wide temperature (-10 to 50 C) and concentration (0 – 2.5 M) range. By combining isotropic chemical shift, linewidth, and T1 relaxation measurements, and proton PFG-NMR measurements, we mapped the emerging solvation spectrum of vanadium species across different electrolyte compositions which helped us design highly stable electrolyte.4-6 Our work demonstrates that mapping solvation spectrum of redox active species offers a promising pathway to engineer an optimal electrolyte for targeted electrochemical systems.ned and applied?
