SULFIDE-BASED SOLID ELECTROLYTE USED FOR LITHIUM ION SECONDARY BATTERY AND PRODUCTION METHOD FOR SAME, SOLID ELECTROLYTE LAYER, AND LITHIUM ION SECONDARY BATTERY

A sulfide solid electrolyte to be used in a lithium-ion secondary battery, including an argyrodite crystal, in which the crystal is represented by a composition formula Li—M—Z—Ha; M is at least one element selected from Na, K, and elements each of which exists as any of divalent to pentavalent cations in the crystal; Z is at least one element selected from elements that exists as a divalent anion in the crystal; Z includes S; Ha is at least one element selected from the group consisting of F, Cl, Br, and I; a, b, and c in the composition formula indicate a ratio among contents (unit: at%) of the respective elements and satisfy 5 < a < 7, 4 < b < 6, and 0 < c < 2; and a maximum distance between Li ions in the crystal is 2.54 Å or shorter.