Tape‐Casting Li0.34La0.56TiO₃ Ceramic Electrolyte Films Permit High Energy Density of Lithium‐Metal Batteries

Ceramic oxide electrolytes are outstanding due to their excellent thermostability, wide electrochemical stable windows, superior Li‐ion conductivity, and high elastic modulus compared to other electrolytes. To achieve high energy density, all‐solid‐state batteries require thin solid‐state electrolytes that are dozens of micrometers thick due to the high density of ceramic electrolytes. Perovskite‐type Li 0.34 La 0.56 TiO 3 (LLTO) freestanding ceramic electrolyte film with a thickness of 25 µm is prepared by tape‐casting. Compared to a thick electrolyte (>200 µm) obtained by cold‐pressing, the total Li ionic conductivity of this LLTO film improves from 9.6 × 10 −6 to 2.0 × 10 −5 S cm −1 . In addition, the LLTO film with a thickness of 25 µm exhibits a flexural strength of 264 MPa. An all‐solid‐state Li‐metal battery assembled with a 41 µm thick LLTO exhibits an initial discharge capacity of 145 mAh g −1 and a high capacity retention ratio of 86.2% after 50 cycles. Reducing the thickness of oxide ceramic electrolytes is crucial to reduce the resistance of electrolytes and improve the energy density of Li‐metal batteries.