A thin free-standing composite solid electrolyte film for solid-state lithium metal batteries.

A thin free-standing composite solid electrolyte film (CSE, ∼15 μm) is prepared by a tape casting and solution infusion method, which owns a high ionic conductivity (2.76 × 10 -4 S cm -1 at 25 °C) and a wide electrochemical stability window (4.8 V vs. Li + /Li). The CSE-based solid-state lithium metal batteries with the LiCoO 2 cathode present good cycling stability and capacity retention with a 4.5 V cut-off voltage.