Sol-gel synthesis is an extensively used method for the preparation of nanopowders. However, complicated or expensive precursors, and the necessity of using organic solvent and/or heat assistance limit the method to laboratory-scaled level. An aqueous-based sol-gel method with spontaneous sol and gel formation is developed in this study. It can be applied on a large scale to synthesize compounds with Ti4+ and PO43- as major components with low cost. Al-substituted LiTi2(PO4)(3) (LATP) has been widely investigated as a promising candidate for solid electrolyte in Li-ion or Li-air batteries. Major challenges such as unsatisfactory phase purity, low sintering activity, and high production costs are faced during the fabrication of LATP. In this study, as a sample application, Li1.5Al0.5Ti1.5(PO4)(3) (LATP05) is conveniently prepared on a large scale by the novel sol-gel method with high phase purity, active densification behavior and high conductivity.