A Li-Garnet composite ceramic electrolyte and its solid-state Li-S battery

A high strength Li-Garnet solid electrolyte composite ceramic is successfully prepared via conventional solid state method with Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 and nano MgO powders. Well sintered ceramic pellets and bars are obtained with 0–9 wt.% MgO. Fracture strength is approximately 135 MPa for composite ceramics with 5–9 wt.% MgO, which is ∼50% higher than that of pure Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (90 MPa). Lithium-ion conductivity of the composite is above 5 × 10 −4  S cm −1  at room temperature ; comparable to the pure Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 material. SEM cross-sections of the composite ceramic shows a much more uniform microstructure comparing with pure ones, owing to the grain growth inhibition effect of the MgO second phase. A battery cell consisting of Li/composite ceramics/Sulfur-Carbon at 25 °C exhibits a capacity of 685 mAh g −1  at 0.2 C at the 200 th cycle, while maintaining a coulombic efficiency of 100%. These results indicate that the composite ceramic Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 -MgO is promising for the production of electrolyte membrane and fabrication of Li-Sulfur batteries.