Published online by Cambridge University Press: 26 December 2017
Lithium solid electrolyte with NASICON structure in the form of Li1+2xAlxTi2−xSixP3−xO12 solid solution has been prepared by high temperature solid state reaction using low cost kaolin as the starting material. The crystal structure of the solid solution was investigated by powder X-ray diffraction. The AC impedance measurements indicate that ionic conductivity increased by more than one order of magnitude when a small amount of Al3+ and Si4+ ions were incorporated into the LiTi2(PO4)3 crystal structure. The significant improvement on ionic conductivity can be attributed to the increased interstitial Li+ ions in the crystal structure. The highest ionic conductivity was found in Li1.2Al0.1Ti1.9Si0.1P2.9O12: 8.3 x 10-5 S·cm-1 at room temperature (21°C) and 1.5 x 10-3 S·cm-1 at 100°C.