Improved Li-ion conductivity of 0.7Li4SiO4–0.3Li3PO4 by aluminum doping
Abstract The solid solution 0.7Li 4 SiO 4 –0.3Li 3 PO 4 (LSP) is known to be a Li-ion conducting ceramic. Aluminum doping of it was carried out to increase the ionic conductivity. The aluminum-doped LSP (LASP) was prepared with different amounts of dopant, to examine the effect of the amount of dopant on the ionic conductivity. LASP was synthesized using a sol-gel reaction and subsequent calcination. The crystalline phase of the LASP was analyzed by powder X-ray diffraction (PXRD) and identified as the monoclinic phase of 0.7Li 4 −  y Al y SiO 4 –0.3Li 3 PO 4 . However, addition of aluminum results in the precipitation of a secondary crystalline Li 2 SiO 3 phase. Li-ion conductivity was estimated by using electrochemical impedance spectroscopic (EIS) analysis on an LASP pellet that had been sintered at 1000 °C. In spite of the precipitation of the Li 2 SiO 3 phase, Li-ion conductivity was increased by aluminum doping at 150 °C to approximately 20 times that of the undoped material (LSP), which effect is considered to be associated with vacancies generated by the aluminum doping providing conducting paths for the Li-ion.