A production method for a halide solid electrolyte of the present disclosure includes (A) halogenating a raw material including a carbonate of at least one metal element selected from the group consisting of Li and M by heat treatment to obtain a halide solid electrolyte containing Li, M, and X. The M is at least one element selected from the group consisting of metal elements (excluding Li) and metalloid elements, and the X is at least one selected from the group consisting of F, Cl, Br, and I.

The present disclosure discloses provides a solid-state electrolyte material and a preparation method thereof, a cathode active material, a cathode plate, and a solid-state battery. The solid-state electrolyte has a NASICON crystal structure. In an X-ray diffraction pattern of the solid-state electrolyte material, the solid-state electrolyte material has a characteristic diffraction peak exhibit at a diffraction angle 2 values of 14.5 to 14.8, a characteristic diffraction peak at a diffraction angle 2 value of 19.5 to 19.7, and a characteristic diffraction peak at a diffraction angle 2 value of 22.5 to 22.8. A ratio of a peak intensity I.sub.1 of the characteristic diffraction peak at a 2 value of 14.5 to 14.8 to a peak intensity I.sub.2 of the characteristic diffraction peak at a 2 value of 22.5 to 22.8 satisfies: 1.5I.sub.2/I.sub.13. Thus, an ionic conductivity and structural stability of the solid-state electrolyte are improved.