Behaviors of H, D, and Li in water-soaked LATP solid electrolytes at room temperature

The elastic recoil detection (ERD) technique was employed to measure the depth distributions of lithium (Li) and hydrogen isotopes (H and D) near the surface of NASICON-type LATP (Li1+xAlxTi1−x/2Ge1−x/2P3−yO12) solid electrolytes soaked in water (H2O and D2O) at room temperature for 1–80 days. The ERD spectra demonstrated H and D absorption on the LATP surface by H2O and D2O soaking and Li segregation to the top surface. Moreover, the field emission-scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) images, and atomic absorption spectrophotometry (AAS) indicated the formation of numerous black substances with approximately 0.5 × 3.0 µm2 in area and < ∼50 nm in thickness and the dissolution of Li in water. Li migration from the bulk to the surface may occur through the reactions of H2O and D2O with Ge, subsequently leading to H and D trapping at Li substitutional sites.