Engineered Interface and Spatial Arrangement of Inorganic Components for Dendrite‐Free Li Anodes in Carbonate‐Based Electrolyte

The practical application of lithium metal batteries (LMBs) in carbonate‐based electrolytes is hindered by uncontrolled lithium (Li) deposition behavior. Here, a calcium fluoride (CaF 2 ) functionalized polyethylene (PE) separator (CF‐PE) is developed to spatially rearrange the inorganic components at the Li anode interface. A spontaneous cation exchange reaction between CaF 2 and detrimental lithium carbonate (Li 2 CO 3 ) generates a high modulus lithium fluoride (LiF) layer on the surface of the CF‐PE separator with a robust calcium carbonate (CaCO 3 ) enriched solid electrolyte interphase (SEI), enabling dense Li deposition behavior. As a result, the CF‐PE separator enabled an extended Li deposition lifespan of more than 1100 h at 1 mAh cm −2 and 650 h at 3 mAh cm −2 . In Li||NMC622 full cells, the CF‐PE separator enabled stable operation over 850 cycles with a low capacity decay rate of 0.025% per cycle. Additionally, the separator retained its structural integrity at 150 °C, with stable cycling of the full cell at 80 °C, greatly outperforming a commercial PE separator. This work presents a practical strategy for constructing dendrite‐free LMBs using carbonate‐based electrolytes with enhanced electrochemical and environmental tolerance.