Engineering a Dynamic Solvent-Phobic Liquid Electrolyte Interphase for Long-Life Lithium Metal Batteries

The heterogeneity, species diversity, and poor mechanical stability of solid electrolyte interphases (SEIs) in conventional carbonate electrolytes result in the irreversible exhaustion of lithium (Li) and electrolytes during cycling, hindering the practical applications of Li metal batteries (LMBs). Herein, this work proposes a solvent-phobic dynamic liquid electrolyte interphase (DLEI) on a Li metal (Li-PFbTHF (perfluoro-butyltetrahydrofuran)) surface that selectively transports salt and induces salt-derived SEI formation. The solvent-phobic DLEI with C-F-rich groups dramatically reduces the side reactions between Li, carbonate solvents, and humid air, forming a LiF/Li₃PO₄-rich SEI. In situ electrochemical impedance spectroscopy and Ab-initio molecular dynamics demonstrate that DLEI effectively stabilizes the interface between Li metal and the carbonate electrolyte. Specifically, the LiFePO₄||Li-PFbTHF cells deliver 80.4% capacity retention after 1000 cycles at 1.0 C, excellent rate capacity (108.2 mAh g^-1 at 5.0 C), and 90.2% capacity retention after 550 cycles at 1.0 C in full-cells (negative/positive (N/P) ratio of 8) with high LiFePO₄ loadings (15.6 mg cm^-2) in carbonate electrolyte. In addition, the 0.55 Ah pouch cell of 252.0 Wh kg^-1 delivers stable cycling. Hence, this study provides an effective strategy for controlling salt-derived SEI to improve the cycling performances of carbonate-based LMBs.