Preparation of Li1.5Al0.5Ti1.5(PO4)3 solid electrolyte via a sol–gel route using various Al sources

Li1.5Al0.5Ti1.5(PO4)3 (LATP) has received much attention as a solid electrolyte for lithium ion batteries due to its high Li ion conductivity. In this study, the LATP is prepared by a sol–gel process using water-soluble Al(NO3)3 and water-insoluble Al(C3H7O)3 as Al sources to examine the influence of the Al source on the properties of the produced LATP. The LATP is successfully produced in both cases; however, a small amount of AlPO4 impurity is formed in the Al(NO3)3 sample due to insufficient mixing of the water-insoluble Ti(C3H7O)4 with the water-soluble Al(NO3)3. In contrast, the AlPO4 formation is not observed in the Al(C3H7O)3 sample. The Li ion conductivity of the Al(C3H7O)3 sample is higher than that of the Al(NO3)3 sample, implying that the AlPO4 impurity acts as a resistance layer. The performance of LATP prepared by the sol–gel method is strongly affected by the Al sources, and the water-insoluble Al source is suitable for water-insoluble Ti(C3H7O)4, which has been the most widely used Ti source to date.