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 Li0.34 La0.56 TiO3 (LLTO) freestanding ceramic electrolyte film with a thickness of 25 microm is prepared by tape-casting. Compared to a thick electrolyte (>200 microm) obtained by cold-pressing, the total Li ionic conductivity of this LLTO film improves from 9.6 x 10(-6) to 2.0 x 10(-5) S cm(-1) . In addition, the LLTO film with a thickness of 25 microm exhibits a flexural strength of 264 MPa. An all-solid-state Li-metal battery assembled with a 41 microm 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.