Improved Li-ion conductivity of 0.7Li4SiO4–0.3Li3PO4 by aluminum doping

Highlight•Aluminum doping has been conducted for Li4SiO4-Li3PO4 solid solution (LSP).•The Al-doped LSP (LASP) has much higher ionic conductivity than the undoped LSP.•The ionic conductivity of LASP increases as the amount of dopant is increased.•LASP has higher ionic conductivity and lower electron transport number.•LASP appears to be a better solid electrolyte than LSP due to the above features.

The solid solution 0.7Li4SiO4–0.3Li3PO4 (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 0.7Li4 − yAlySiO4–0.3Li3PO4. However, addition of aluminum results in the precipitation of a secondary crystalline Li2SiO3 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 Li2SiO3 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.