Novel Deep Eutectic Electrolyte Induced by Na···N Interactions for Sodium Batteries

Described herein presents a class of novel deep eutectic electrolytes (DEEs) with distinctive properties for sodium batteries. Instead of being limited by the presence of a hydrogen bond donor (HBD) or hydrogen bond acceptor (HBA), the concept of Na···N interactions was first brought in between sodium bis(fluorosulfonyl)imide (NaFSI) and 1,2-dimethylimidazole (DMIm). The deep eutectic phenomenon was caused by the strong ion–dipole interaction, which was conducive to the release of Na+ from NaFSI and drove the DEE with a desirable ionic conductivity. Furthermore, the proposed mechanism of Na···N interactions was credibly confirmed by Raman, 23Na NMR, and theoretical calculations. The half-cell based on NaFSI/DMIm–1/4 can provide a reversible capacity of 316.7 mAh·g–1 at 0.05 A·g–1, and Coulombic efficiency remains 91% after 500 charge–discharge cycles at 1.0 A·g–1 in the application of sodium batteries. It is anticipated that this work will present distinct insights into the extension of electrolytes for sodium batteries.