Unravelling the Role of Speciation in Glyme:Ionic Liquid Hybrid Electrolytes for Na-O2 Batteries

The morphology and size of the discharge products in Na-O-2 batteries are largely dominated by the interactions of the electrolyte with superoxide and sodium ions; therefore, an in-depth understanding is essential for achieving high performance batteries. Herein, we report a framework designed to understand solvation and coordination in the recently discovered hybrid electrolytes, based on glyme and a pyrrolidinium ionic liquid. FTIR and NMR spectroscopic techniques, coupled with molecular dynamics simulations, have been used to characterize these systems. We demonstrate that the presence of ionic liquid in the hybrid electrolyte affects the superoxide coordination environment by weakening the glyme-Na+ interactions, and generating solvent separated ion pairs. All these factors lead to different deposition mechanisms, which will determine the battery performance. The Na+ solvation shell compositions, anion conformers and relative free glyme content are also evaluated. The combinatorial approach used in this study-experimental and computational - can be applied for further design of these hybrid electrolytes and other metal - O-2 chemistries and electrochemical systems.

Automated summary

This study reports a framework designed to understand solvation and coordination in hybrid electrolytes based on glyme and a pyrrolidinium ionic liquid. Experimental and computational methods were combined to analyze the performance factors of these systems, providing new insights for the further design of hybrid electrolytes and other metal-O-2 chemistries and electrochemical systems.