Morphological, dielectric and transport properties of garnet-type Li6.25+yAl0.25La3Zr2-yMnyO12 (y=0, 0.05, 0.1, and 0.2)

Garnet-type solid Li ion conductor Li7La3Zr2O12 (LLZO) has received considerable attention due to its high total (bulk + grain boundary) ionic conductivity at room temperature and its chemical stability with Li metal. To improve the ionic conductivity of LLZO, the hetrovalent doping at Zr-site and Al-doping at Li site was done for the optimization of Li concentration in LLZO. Thus, considering prominent role of various dopant in ionic and/or electronic conduction of LLZO, the effect of Mndoping at Zr-site in the Al-doped Li6.25+yAl0.25La3Zr2-yMnyO12 (y = 0, 0.05, 0.1, 0.2) on the microstructure, dielectric and transport properties is studied. The Mndoping at Zr-site in Al-LLZO is confirmed by electron paramagnetic resonance and X-ray photoelectron spectroscopy techniques. A correlation between structure, microstructure and the Li+ ion conduction is established. Amongst all investigated compounds, Li6.35Al0.25La3Zr1.9Mn0.1O12 exhibit highest total ionic conductivity of 0.34 x 10(-4) Scm(-1) at 25 degrees C. Further, the electrochemical window and stability of Mn doped-LLZO with Li metal is examined by cyclic voltammetry.