The invention discloses a
solid electrolyte material with low
interface impedance and a preparation method of the
solid electrolyte material. The material comprises a major structure with a
chemical formula Li1+x+yAlx(Ti,Ge)2-xSiyP3-yO12, and
lithium iodide dispersed in the major structure, wherein the major structure of the material is an NASICON
fast ion conductor; x is greater than 0 and less than or equal to 0.4; y is greater than 0 and less than or equal to 0.1; and the
mass percentage a of
lithium iodide in the material is greater than 0 and less than or equal to 10%. The preparation method of the material comprises the following steps of (1) synthesizing the major structure: selecting raw materials according to a stoichiometric equation of the
solid electrolyte material and performing
planet ball milling, cold pressing and a solid-
phase reaction to obtain the major structure of the dense flaky solid electrolyte material, and (2) performing modification treatment: soaking a sample obtained in Step (1) in a
lithium iodide aqueous solution, performing heating for some time, taking the sample out, cleaning the sample and performing
vacuum drying treatment. According to the solid electrolyte material and the preparation method, a
lithium iodide material with
lithium ion conduction property is added to a solid electrolyte layer, so that the
interface impedance is reduced, a three-dimensional
ion conduction network is formed, and the
ion conductivity is improved.