Effect of Anion Substitution of SiO44- for Li3Sc2(PO4)(3) Superion Conductor

Li3Sc2(PO4)(3) was one of the most powerful solid state electrolytes for lithium ion batteries because of its favourable channels for ion conduction, very low electronic conductivity and high stability in air. However, the compound only presented superionic conductivity at temperatures higher than 245 degrees C. Cation substitution of Zr4+, Ti4+ and so on for partial Sc3+ was generally adopted in order to increase its room-temperature ionic conductivity, and researches on anion substitution for PO43- in the Li3Sc2(PO4)(3) compound were little. In this research, we introduced some SiO2 into starting-materials mixture of the Li3Sc2(PO4)(3) ceramics by mechanical milling, and tried to substitute for partial PO43-. Our results proved that the prepared Li3+xSc2(PO4)(3-x)(SiO4)(x) (x=0 similar to 0.6) compounds showed the highest ion conductivity of 9.55x10(-4) S.m(-1) at 298 K, as well as the lowest activation energy of 45.06 kJ . mol(-1). Furthermore, the Si-29 MAS-NMR spectrum indicated that the added SiO2 mainly existed in the form of [SiO4] tetrahedra substituting for [PO4] tetrahedra in the compound.