Anomalous Solubility-Inverted Behavior of LiPF 6 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 (LiPF 6 ) 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 LiPF 6 in glyme ether solvents originates from a "dissociation-solvation-reprecipitation" mechanism. Taking LiPF 6 in dimethoxyethane (DME) as an example, weak dielectric screening and high molecular symmetry of glyme ethers promote the association of DME-solvated Li + and PF 6 - , leading to the formation of an insoluble solvate crystal, Li(DME) 2 PF 6 . Based on this mechanism, we further predict and experimentally verify a solubility-inverted region (SIR), in which LiPF 6 and glyme ethers can reform a homogeneous solution once the LiPF 6 concentration exceeds a critical threshold, provided that the eutectic point between the Li(ether) x PF 6 solvate crystal and LiPF 6 falls below the operating temperature. Consequently, an electrolyte consisting of 5.0 M LiPF 6 in DME/DEE (1:1 vol %) exhibits anodic stability up to 7.0 V vs Li + /Li. A Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 cell with a cutoff voltage of 4.5 V further confirms the feasibility of high voltage electrochemistry in LiPF 6 -glyme ether electrolytes. These results clarify LiPF 6 -glyme ether interactions and offer new opportunities for designing advanced electrolytes for high-voltage LMBs.