Weakly-Solvated and Co-Intercalation-Free Ether-Based Electrolytes Enhance the Low- Temperature and Fast-Charging...

Lithium-ion batteries (LIBs) employing lithium iron phosphate (LiFePO₄, LFP) cathodes and graphite (Gr) anodes are extensively utilized for energy storage applications because of their exceptional cycle life and inherent safety characteristics. However, sluggish desolvation kinetics and interfacial Li⁺ transport hinder their fast-charging capability and low-temperature performance, limiting broader applications. In this work, we propose a weakly solvating ether (WSE) electrolyte based on 2-methyl-tetrahydrofuran (2MT) as the main solvent. This electrolyte results in considerable steric hindrance, effectively preventing co-intercalation with Gr, while also providing a weak solvation capability for Li⁺ ions and facilitating rapid interfacial Li⁺ transport. WSE, formulated with 2MT and fluoroethylene carbonate (FEC) as a co-solvent, combines fast desolvation kinetics with an extremely low freezing point of -117.67 °C. This electrolyte induces the formation of a LiF-, Li₃N-, Li₂CO₃-, and Li₂O-rich solid electrolyte interphase (SEI) on the Gr anode, thereby enhancing low-temperature interfacial transport. Consequently, the Gr||Li half-cell and the LFP||Gr full cell with this WSE demonstrates excellent rate performance, stable cycling stability, and a high specific capacity at -30 °C while also delivering reliable power even at -60 °C. These results underscore the electrolyte's efficient desolvation process, stable SEI layer, and excellent compatibility with graphite, rendering it ideal for extreme-temperature applications.