Polymer-Inorganic Nanocomposite Coating with High Ionic Conductivity and Transference Number for a Stable Lithium Metal Anode.

We report a nanocomposite coating for lithium metal protection, which consists of nanosized LiF particles embedded into a PEO polymer matrix. The composite offers a large LiF/PEO interface area throughout the coating, promoting an exceptionally high ionic conductivity of 0.97 mS cm-1 and high lithium-ion transference number of 0.77 at room temperature in contact with a carbonate-based liquid electrolyte. Both properties are key to realize uniform lithium plating and stripping and prevent lithium dendrite formation. Lithium metal electrodes coated with this protective coating enable stable lithium plating and stripping at 1 mA cm-2 for over 1000 h. A full cell with the coated lithium metal anode and an NMC622 cathode with an areal capacity of 1 mA h cm-2 shows much improved specific capacity and cycling stability. The cell exhibits a high initial capacity of 135 mA h g-1 and a capacity retention of 83% after 500 cycles at 1 mA cm-2. Even at a high current density of 3 mA cm-2, the full cell shows an initial capacity of 125 mA h g-1 and a capacity retention of 74% after 300 cycles.