SULFIDE SOLID ELECTROLYTE, METHOD FOR PRODUCING SULFIDE SOLID ELECTROLYTE, POSITIVE ELECTRODE FOR POWER STORAGE ELEMENT, AND POWER STORAGE ELEMENT

According to one aspect of the present invention having a crystal structure, includes: at least one element A selected from the group consisting of a lithium element, a sodium element, and a potassium element; a phosphorus element; at least one element M selected from the group consisting of an aluminum element and a boron element; a nitrogen element; and at least one halogen element, in which a molar ratio of a content of the element A to a content of the phosphorus element (A/P) is less than 3.74, and a molar ratio of a content of the nitrogen element to a content of the phosphorus element (N/P) is less than 0.33.