Hydrogen Absorption in Near Surface of Lithium-ion Conductive Glass Ceramics by Water Uptake at Room Temperature

Abstract

The hydrogen isotope (H and D) concentrations in the two types of Li_1+xAl_xTi_1−x/2Ge_1−x/2P_3−yO₁₂ and Li_1+x+yAl_xTi_2−xSi_yP_3−yO₁₂ (LATP: AG-01 and SP-01, respectively) electrolytes, soaked in D₂O for 19—22 days and subsequently exposed to air at room temperature and humidity of 80% for 11—21 days, were measured by combining elastic recoil detection with Rutherford backscattering spectrometry. The total numbers of H and D atoms in AG-01 and SP-01 were estimated to be approximately 5.0 and 0.66 atoms, respectively, after the absorption of H₂O and D₂O and the replacement of H by D. Field emission scanning electron microscopy and atomic force microscopy images revealed that many black substance formations with dimensions of approximately 0.5 × 3.0 μm² in area and less than approximately 200 nm in thickness appeared on the surface of the D₂O-soaked and air-exposed AG-01. These formations appeared because of the segregation of Li from the bulk to the surface by the reactions of H₂O and D₂O with the doped Ge, which might lead to H and D trapping at the Li substitutional sites.