Method for preparing solid electrolyte lithium-lanthanum-titanium oxygen compound film

The invention discloses a method for preparing a solid electrolyte lithium-lanthanum-titanium oxygen compound film. The method comprises the following steps: adding a metal salt containing lithium, lanthanum and titanium into a solvent, and stirring to dissolve the metal salt so as to obtain a solution; adding a micro-molecule complexing agent, stirring to dissolve the micro-molecule complexing agent, further adding a soluble high-molecular polymer solution, and uniformly stirring so as to obtain a mixed solution; heating to concentrate the mixed solution till the total concentration of all metal ions in the mixed solution is not greater than 0.4mol/L, so as to obtain a precursor liquid; coating the surface of a substrate with the precursor liquid, and sintering in a tubular furnace, so as to obtain the solid electrolyte lithium-lanthanum-titanium oxygen compound film. By using a high-molecular auxiliary deposition method, and adopting a spinning mode, LLTO (Lithium-Lanthanum-Titanium Oxygen) solid films can be prepared on various substrates. The method is simple in equipment, low in cost, high in film coating efficiency, high in ionic conductivity, low in electronic conductivity, good in thermodynamic stability and applicable to solid lithium ion batteries.