Fluorine-Rich Electrolyte\nAdditive for Achieving Dendrite-Free\nLithium Anodes at Low Temperatures

The practical application of lithium metal anodes is\nsignificantly\nimpeded by poor interfacial stability and uncontrolled dendrite growth.\nHerein, we introduce methyl trifluoroacetate (MTFA), a low-melting-point\nsmall molecule, as an electrolyte additive in an ether-based electrolyte.\nThis additive facilitates the formation of an in situ composite solid\nelectrolyte interphase (SEI) layer that is rich in LiF and features\nan ester-based flexible matrix. The resulting composite layer exhibits\nhigh ionic conductivity and mechanical stability, effectively regulating\nthe lithium deposition behavior over a broad temperature range and\ninhibiting dendrite formation. Based on MTFA, the Li||Li symmetrical\ncell achieves a lifespan exceeding 5000 h at room temperature and\n800 h at −20 °C, both with ultralow overpotential and\nexceptional cycling stability. In Li||LiFePO<sub>4</sub> full cells\nwith a high-area loading (10.52 mg cm<sup>–2</sup>) and an\nN/P ratio of 1.68, an average capacity decay of merely 0.096% per\ncycle is observed over 200 cycles. Even at −20 °C, the\nLi||LiFePO<sub>4</sub> cell shows a CE of over 99% and maintains stable\ncycling performance. This work provides an innovative approach for\noptimizing lithium metal anode interfaces and enhancing low-temperature\noperation capabilities through the use of electrolyte additives.