Study on Phase Evolution and Material Properties of Li10SiP2S12-XOx

Abstract

Oxygen substitution was carried out on Li10SiP2S12 (LSiPS) which has the Li10GeP2S12 (LGPS) type crystalline structure. The general formula of Li10SiP2S12-xOx (LSiPSO) where 0 ≤ x ≤ 1.75 was set for solid state reaction to produce oxy-sulfide sites. The phase distribution and local structural units of LSiPSO were determined by powder X-ray diffraction (PXRD), and Raman, FT-IR,29Si and 31P Solid State NMR spectroscopies. The LGPS like LSiPSO phase increased while the impurity phase, β-Li3PS4 was reduced and formed Li3PO4 phase by O substitution. The optimized lithium ionic conductivity was found for x = 0.7 at 3.1 x 10-3 S/cm at 25℃. However, for the higher doped oxygen such as x > 0.9, a degradation of LSiPSO occurs and it is also expected to become the Li3PO4 phase which leads to a decrease in the ionic conductivity. The local structural units was determined by 31P and 29Si NMR and spectrum deconvolution to show sulfide, oxide and mixed oxy-sulfide local units. On the other hand, the doped O was found that only incorporating with phosphate centered tetrahedral unit such as PS4-xOx during no pure orthosilicate SiO4 4- units were observed, even at the highest x examined.