Ion Transport across Grain Boundaries in Fast Lithium Ion Conducting Glass Ceramics

摘要

Li_(1.5)Al_(0.5)Ge_(1.5)(PO_4)_3 (LAGP) 1. Grain and grain boundary resistance exhibit the same activation energy. → Purely geometrical current constriction; fraction of contacted area: about 25% Ohara Glass Ceramic (Li_(1+x)Al_xTi_(2-x)(PO_4)_3 doped with other oxides) 2. Grain boundary resistance exhibits a slightly higher activation energy than the grain resistance. 3. Nonlinear impedance spectra provide strong indication that the grain boundary resistance is not caused by a single (space charge) barrier, but by several serial barriers 4. Fit of nonlinear impedance data suggests that the thickness of the grain boundaries is in the range 5-10 nm. 5. HR-TEM images reveal type-A (amorphous) and type-B (high degree of crystallinity) grain boundaries. 6. Thickness of type-B grain boundaries is, in fact, in the range 5-10 nm. Mechanical stresses may lead to slightly higher activation energy.