Taming the Ion‐Dipole Interaction via Rational Diluent Selection for Low‐Temperature Li‐Metal Batteries

Developing advanced electrolytes with high Li affinity is crucial for achieving long‐cycling lithium metal batteries (LMBs). However, the strong Li+‐solvent interactions in conventional electrolytes often induce difficult Li+ desolvation especially under low‐temperature conditions, resulting in the formation of fragile electrode interfaces involving solvents, and thus dissatisfactory cycling stability of LMBs. Herein, by introducing various diluents into the lithium hexafluorophosphate in 1, 2‐dimethoxyethane electrolyte, we reveal that Li+ desolvation is influenced by not only the diluent‐solvent interaction but also the diluent‐anion interaction. Based on these findings, a diluent selection parameter (DSP), which is calculated based on the product of interaction energies of diluent‐solvent/diluent‐Li+ and diluent‐anion/diluent‐Li+, is proposed for diluent selection. A diluent with a larger DSP is more favorable for promoting Li+ desolvation and improving the low‐temperature performance of LMBs. With the rationally selected 1, 2‐dichloroethane diluent (DSP=3.95), Li||Cu cell enables high Li reversibility (98.5% after 300 cycles). Li||LiFePO4 cell barely loses capacity at −20 °C for 300 cycles. The Li||LiNi0.8Co0.1Mn0.1O2 cell with the anode‐to‐cathode capacity ratio of 2.7 retains 87% capacity retention after 100 cycles. This work not only provides new insights into taming strong Li‐solvent interactions but also offers a new paradigm for advanced electrolyte design.