Deciphering and modulating energetics of solvation structure enables aggressive high-voltage chemistry of Li metal batteries

Summary

The stability of localized high-concentrated electrolytes (LHCEs) on the Li metal anode has been well established, but the understanding of its oxidation chemistry for high-voltage cathodes is unclear. Here, we demonstrate that the de-coordination between Li⁺ and solvents defines the anodic stability of LHCEs, which can be finely tuned by the ambient diluents. After screening the possible diluents, we found that 2H,3H-decafluoropentane (HFC) satisfies the principle of relatively weak but sufficient interactions with solvation shell, thus strengthening the Li⁺ coordination and offering electrolytes excellent antioxidant chemistry. The proposed HFC-LHCE enables practical Li metal batteries to realize >90% capacity retention with a Coulombic efficiency of 99.91% for >180 cycles under aggressive conditions (4.4 V 20-μm-Li||3.7-mAh cm⁻²-LiNi_0.8Mn_0.1Co_0.1O₂ and 4.5 V 20-μm-Li||4-mAh cm⁻²-LiCoO₂ cells). This work presents guiding principles for improving electrolyte cathodic and anodic stability, which benefits the development of LHCEs and inspires the formulation of next-generation lithium batteries.