Abstract: An oxychloride solid-state electrolyte, and a preparation method and use thereof are provided. The oxychloride solid-state electrolyte is represented by a chemical formula of xLi2O-(1?y)ZrCl4-yAlCl3, where 0<x?3, and 0<y?1. Compared with other solid-state electrolytes such as sulfides, halides, and oxides (most of which exhibits a Young's modulus greater than 20 GPa, and even greater than 100 GPa), the oxychloride solid-state electrolyte exhibits a significantly lower Young's modulus (no greater than 4 GPa). All-solid-state lithium batteries assembled with the oxychloride solid-state electrolyte exhibit superior areal capacity and long cycle stability.