Glyme‐based Localized High Concentration Electrolytes Improve the Stability of Na‐ion Battery Materials in Half‐cells

Abstract Sodium‐ion batteries (SIBs) have emerged as promising alternatives to lithium‐ion batteries for grid energy storage and automotive applications. However, their widespread adoption necessitates improved cycling stability and energy density, largely dependent on electrode materials and electrolytes. This study investigates the compatibility and performance of the diglyme‐based localized high concentration electrolyte (LHCE/G2) for SIB applications, proposing it as the electrolyte of choice for materials screening in half‐cell configuration. Three layered oxide cathode materials were tested in LHCE/G2 against sodium metal counter electrodes, demonstrating significantly enhanced cycling stability compared to carbonate electrolytes. The electrochemical stability of LHCE/G2 on sodium metal was confirmed through long‐term plating/stripping profiles. The findings suggest that glyme‐based LHCEs offer a promising approach to evaluating high‐voltage oxide cathodes, minimizing electrolyte‐related degradation, and enhancing the reliability and performance of SIBs.