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

The hydrogen isotope (H and D) concentrations in the two types of Li1+xAlxTi1-x/2Ge1-x/2P3-yO12 and Li1+x+yAlxTi2-xSiyP3-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 meas-ured by combining elastic recoil detection with Rutherford backscattering spectrometry. The total numbers of H and D at-oms 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 elec-tron microscopy and atomic force microscopy images revealed that many black substance formations with dimensions of ap-proximately 0.5 x 3.0 mu m2 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 reac-tions of H2O and D2O with the doped Ge, which might lead to H and D trapping at the Li substitutional sites.