Anomalous Solubility-Inverted Behavior of LiPF6 in Glyme Ether Solvents for High-Voltage Electrochemistry

Advanced electrolyte configurations are essential for next-generation lithium batteries. Glyme ether electrolytes are attractive due to their low reactivity with lithium metal. However, the commonly used lithium bis(fluorosulfonyl)imide (LiFSI) salt exhibits poor anodic stability due to severe aluminum corrosion. In contrast, lithium hexafluorophosphate (LiPF6) offers excellent aluminum compatibility at high voltages but exhibits abnormally low solubility in glyme ether solvents, limiting its application in lithium batteries. The underlying mechanism for this behavior remains unclear. Herein, we show that the low solubility of LiPF6 in glyme ether solvents originates from a "dissociation-solvation-reprecipitation" mechanism. Taking LiPF6 in dimethoxyethane (DME) as an example, weak dielectric screening and high molecular symmetry of glyme ethers promote the association of DME-solvated Li+ and PF6-, leading to the formation of an insoluble solvate crystal, Li(DME)2PF6. Based on this mechanism, we further predict and experimentally verify a solubility-inverted region (SIR), in which LiPF6 and glyme ethers can reform a homogeneous solution once the LiPF6 concentration exceeds a critical threshold, provided that the eutectic point between the Li(ether)xPF6 solvate crystal and LiPF6 falls below the operating temperature. Consequently, an electrolyte consisting of 5.0 M LiPF6 in DME/DEE (1:1 vol %) exhibits anodic stability up to 7.0 V vs Li+/Li. A Li||LiNi0.8Co0.1Mn0.1O2 cell with a cutoff voltage of 4.5 V further confirms the feasibility of high voltage electrochemistry in LiPF6-glyme ether electrolytes. These results clarify LiPF6-glyme ether interactions and offer new opportunities for designing advanced electrolytes for high-voltage LMBs.