Li7La3Zr2O12-Based Solid Electrolytes Codoped with Ta5+ and Al3+ Ions for Lithium Power Sources

Li7La3Zr2O12-based compounds are today the most promising solid electrolytes for high-energy lithium and lithium-ion power sources. The solid electrolytes Li7-x-3yAlyLa3Zr2-xTaxO12 (x = 0.3-0.6, y = 0.05-0.20) were prepared by the sol-gel method. The effect of doping of Li7La3Zr2O12 in Zr and Li sublattices with tantalum (Ta5+) and aluminum (Al3+) on the crystal structure, morphology, and electrical conductivity of this compound was examined. The compounds obtained had the cubic structure (space group Ia-3d). The resistance of the solid electrolytes obtained was determined by the electrochemical impedance method. The compounds Li6.25Al0.15La3Zr1.7Ta0.3O12, Li6.3Al0.10La3Zr1.6Ta0.4O12, Li6.2Al0.10La3Zr1.5Ta0.5O12, and Li6.25Al0.05La3Zr1.4Ta0.6O12 have the maximal lithium-ion conductivity (similar to 2.0 x 10(-4) S cm(-1) at 20 degrees C). The heat treatment at 1150 degrees C for 1 h is optimum for forming highly conducting and dense ceramic membranes. Symmetrical cells with Li electrodes show stable behavior in cycling. The solid electrolytes obtained can be used in lithium power sources.