Bifunctional carbon monofluoride (CFx) coating on a separator for lithium-metal batteries with enhanced cycling stability

Herein, we suggest a new way to improve the cycling stability of the lithium-metal battery by using a separator coated by carbon monofluoride (CFx). CFx has been used as a cathode material for a lithium primary battery and is converted to LiF and carbon during the discharge process. The CFx-coated separator with 5 μm thickness is obtained by casting a CFx-containing slurry on a bare polyethylene separator and the CFx-coated separator is characterized in a LiCoO2 (LCO) // Li cell. The CFx-coated separator enables a better cycling stability up to 200 cycles than the bare separator due to its dual functions: 1) capturing cobalt ions dissolved from the LCO cathode and 2) formation of a thin and stable SEI layer containing LiF on the lithium metal anode. Employment of the CFx-coated separator also leads to much suppressed dendritic growth of lithium and stable interfacial resistance during the cycle.