12 µm‐Thick Sintered Garnet Ceramic Skeleton Enabling High‐Energy‐Density Solid‐State Lithium Metal Batteries

Ultrathin composite solid-state electrolytes (CSSEs) demonstrate great promise in high-energy-density solid-state batteries due to their ultrathin thickness and good adaptability to lithium metal anodes. However, uncontrolled dendrite growth and performance deterioration caused by the aggregation of inorganic powder restrict the practical application of ultrathin CSSEs. Herein, a flexible, self-supporting Li6.5La3Zr1.5Ta0.5O12 (LLZO) ceramic skeleton is prepared by the tape-casting method. Subsequently, a 12 µm-thick CSSE with a 3D interconnection structure is achieved through in situ UV curing of ethoxylated trimethylolpropane triacrylate (ETPTA) in a ceramic skeleton (CS-CSSE). This design includes a sintered LLZO ceramic, which can avoid the uneven distribution of the inorganic phase and regulate ion migration. Meanwhile, the cross-linked ETPTA polymer electrolyte contributes to lower interfacial impedance. In addition, the continuous two-phase interface can also provide a fast transmission channel for Li⁺. As a result, CS-CSSE demonstrates superior Li⁺ transference number (0.83) and ionic conductivity (1.19 × 10^-3 S cm^-1) at 25 °C. As-prepared Li|LiNi0.83Co0.12Mn0.05O2 batteries exhibit high discharge specific capacities of 185.4 mAh g^-1 at 0.1 C and average coulombic efficiency greater than 99%. The pouch cells exhibit high energy densities of 376 Wh Kg^-1 and 1186 Wh L^-1. This work provides new insights into the application of ceramics to high-energy-density solid-state batteries.