SULFIDE SOLID ELECTROLYTE

An object of the present invention is to provide a sulfide solid electrolyte that can suppress the generation of hydrogen sulfide gas while maintaining the lithium ion conductivity; and an electrode composite material, a slurry and a battery, in each of which the sulfide solid electrolyte is used, and, in order to achieve the object, the present invention provides a sulfide solid electrolyte containing lithium (Li), phosphorus (P) and sulfur (S) elements; at least one halogen (X) element; and at least one metal (M) element having a first ionization energy of more than 520.2 KJ/mol and less than 1007.3 KJ/mol, wherein, in an X-ray diffraction pattern measured with CuKα1 radiation, peaks are present at positions of 2θ = 25.19° ± 1.00° and 29.62° ± 1