TY - JOUR
T1 - Oxygen Vacancies in Fast Lithium-Ion Conducting Garnets
AU - Kubicek, Markus
AU - Wachter-Welzl, Andreas
AU - Rettenwander, Daniel
AU - Wagner, Reinhard
AU - Berendts, Stefan
AU - Uecker, Reinhard
AU - Amthauer, Georg
AU - Hutter, Herbert
AU - Fleig, Jürgen
PY - 2017/8/11
Y1 - 2017/8/11
N2 - Fast Li-ion conducting garnets have shown excellent performance as chemically stable solid state Li electrolytes even at room temperature. However, because of phase formation and Li loss during preparation, reliably obtaining high Li-ion conductivities remains challenging. In this work, we show that an additional defect chemical species needs to be considered, namely, oxygen vacancies. We prove the existence of oxygen vacancies in all six investigated sample types: Ta-, Al-, and Ga-stabilized cubic Li7La3Zr2O12 (LLZO) polycrystals and Ta-stabilized LLZO single crystals. Isotope exchange three-dimensional analysis was used to characterize surface oxygen exchange (k*) and bulk oxygen diffusion (D*) enabled by the oxygen vacancies present in the LLZO variants. Remarkably high k* values of 10–11–10–8 cm s–1 and D* values of 10–15–10–11 cm2 s–1 were found at 350 °C in air. In a further data analysis, the differences between the compositions are investigated, the concentration of oxygen vacancies is estimated, and the possible effects on the cation defect chemistry and phase formation of LLZO are discussed.
AB - Fast Li-ion conducting garnets have shown excellent performance as chemically stable solid state Li electrolytes even at room temperature. However, because of phase formation and Li loss during preparation, reliably obtaining high Li-ion conductivities remains challenging. In this work, we show that an additional defect chemical species needs to be considered, namely, oxygen vacancies. We prove the existence of oxygen vacancies in all six investigated sample types: Ta-, Al-, and Ga-stabilized cubic Li7La3Zr2O12 (LLZO) polycrystals and Ta-stabilized LLZO single crystals. Isotope exchange three-dimensional analysis was used to characterize surface oxygen exchange (k*) and bulk oxygen diffusion (D*) enabled by the oxygen vacancies present in the LLZO variants. Remarkably high k* values of 10–11–10–8 cm s–1 and D* values of 10–15–10–11 cm2 s–1 were found at 350 °C in air. In a further data analysis, the differences between the compositions are investigated, the concentration of oxygen vacancies is estimated, and the possible effects on the cation defect chemistry and phase formation of LLZO are discussed.
U2 - 10.1021/acs.chemmater.7b01281
DO - 10.1021/acs.chemmater.7b01281
M3 - Article
SN - 0897-4756
VL - 29
SP - 7189
EP - 7196
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 17
ER -