Intermolecular interactions optimization in weakly solvating ether solvents for wide-temperature Na metal batteries

The development of wide-temperature-range batteries is essential for applications under extreme weather conditions and scientific endeavors such as deep-sea and space exploration. Sodium (Na) metal batteries offer the advantage of weak ion-solvent interactions, which promote easier desolvation at low temperatures compared with lithium batteries. Weakly solvating electrolytes can further decrease desolvation energy barriers, thereby enhancing electrochemical reversibility at low temperature. However, conventional weakly solvating solvents are highly volatile, posing safety concerns for high-temperature applications. Herein, we redesign the molecular structure of typical weakly solvating ethers to reinforce intermolecular interactions, thereby increasing their boiling points while preserving their low solvation characteristics. As a result, the Na metal batteries exhibit stable performance at current densities of at least 0.5 mA cm⁻² across a wide temperature range from -40 to 70 °C. Moreover, the kinetic study highlights the previously overlooked yet critical role of solvent intermolecular interactions in influencing the desolvation barrier at low temperatures, in addition to ion-solvent interactions. Therefore, optimizing the intermolecular interactions of weakly solvating solvents is proposed to be a facile and promising strategy for achieving wide-temperature Na metal batteries.