Halide solid electrolyte production method, halide solid electrolyte, positive electrode material, and battery

A production method for a halide solid electrolyte containing Li, Ti, M, and X, wherein

• the M is at least one element selected from the group consisting of metal elements (excluding Li and Ti) and metalloid elements and metal elements,
• the X is at least one selected from the group consisting of F, Cl, Br, and I, and
• the production method comprises:
• (A) performing halogenation treatment on at least one Li source selected from the group consisting of a simple oxide and a simple carbonate of Li, at least one Ti source selected from the group consisting of a simple oxide and a simple carbonate of Ti, and at least one M source selected from the group consisting of a simple oxide and a simple carbonate of M, to obtain a simple halide of Li, a simple halide of Ti, and a simple halide of M, respectively;
• and
• (B) synthesizing the halide solid electrolyte using the simple halide of Li, the simple halide of Ti, and the simple halide of M.