METHOD FOR PRODUCING SOLID ELECTROLYTE

The present invention relates to a method for producing a crystalline solid electrolyte having a small particle diameter and also having a high ionic conductivity and containing a lithium element, a sulfur element, a phosphorus element and a halogen element, the method including a complexing step of mixing a solid electrolyte raw material and a complexing agent in a liquid phase, wherein the method includes a mixing step of obtaining a precursor containing a lithium element, a sulfur element, and a phosphorus element; and a crystallization step of heating the precursor in a solvent using a pressure-resistant container or while refluxing.