A novel and environmentally preferable method is provided for preparing solid electrolyte particles capable of making dense, flexible, Li+ conducting electrolyte thin films. Methods are also provided for using the solid electrolyte particles and/or thin films in manufacturing safer and more efficient lithium-based batteries. In particular, the method uses inorganic precursors instead of using organic precursors in preparing an aerosol and then convert the aerosol to solid powders to provide the solid electrolyte particles. The solid electrolyte particles prepared have a cubic polymorph and have a desired particle size range, and are capable of making a solid electrolyte film with a thickness less than 50 μm.