Nuclear Magnetic Resonance Dynamics of Pyrazole-LiTFSI Eutectic Solvents as Promising Electrolytes

Deep Eutectic Solvents (DESs) have emerged as promising candidates to replace conventional organic solvents in various technological applications due to their low vapor pressure, non-flammability, and ease of preparation at low costs. In particular, Type IV DESs, which are composed of metal salts and hydrogen bond donors, are possible replacements for lithium-ion battery electrolytes due to their potential of having high lithium transference numbers. In this study, we investigated solvents of Pyrazole and LiTFSI at varying molar ratios using Fast Field Cycling (FFC) NMR Relaxometry. Notably, the 1:2 LiTFSI: Pyrazole sample shows distinct behavior, exhibiting enhanced relaxation rates for 1H, suggestive of stronger Li⁺–Pyrazole interactions. These findings align with prior reports of asymmetric Li⁺ coordination in these systems. Our study advances understanding of ion dynamics in azole-based eutectic solvents and supports their potential use in safer, more sustainable battery electrolytes.