Tailoring fluorine-rich solid electrolyte interphase to boost high efficiency and long cycling stability of lithium metal batteries

Lithium metal batteries (LMBs) are regarded as the most promising next-generation battery system due to their high energy density. However, Li dendrite growth and low Coulombic efficiency (CE) of Li metal anodes limit their commercialization. Regulating solid electrolyte interphase (SEI) is an extremely effective method to solve these problems and using electrolyte additives to regulate the SEI is one of the most effective strategies. Herein, we study the feasibility of trans-difluoroethylene carbonate (DFEC) used as the solvent additive in conventional ether electrolyte, which has excellent anti-reduction stability against Li metal. The result shows that a Li/Cu half-cell with the modified electrolyte can be steadily cycled for 300 cycles with an average CE of 97.41% at the current density of 0.5 mA cm⁻² and with 97.1% for 140 cycles at 1 mA cm⁻². Besides, the Li/LFP full cell with the modified electrolyte displays an improved capacity retention of 94.55% after 520 cycles with an average CE of 99.74% at 1 C. By contrast, the capacity retention of 56.2% and CE of 99.15% is obtained for the cell with pure ether electrolyte. The SEM images show that the DFEC enables dense Li deposition, and the FTIR and XPS spectra confirm the formation of LiF-rich SEI with the DFEC. This work demonstrates the feasibility of using DFEC as the solvent additive in ether electrolyte to construct LiF-rich SEI, and it will provide important insight in developing high-performance electrolytes for LMBs. [Figure not available: see fulltext.]