Lightweight flame-retardant building thermal insulation material and preparation method thereof

The invention provides a lightweight flame-retardant building thermal insulation material, which is prepared by the following method: (1) adding a small amount of high molecular weight polymer into a sol solution to prepare a spinning precursor solution with high conductivity and low viscosity; (2) preparing an organic micro-nano blocky fiber sponge precursor with a three-dimensional space structure from the spinning precursor solution by using an electrostatic spinning technology; and (3) six surfaces of the organic micro-nano blocky fiber sponge precursor are respectively impregnated in the impregnation liquid, the impregnation liquid is another sol solution, and after the impregnation liquid is completely cured, the organic micro-nano blocky fiber sponge precursor is subjected to high-temperature calcination in an air atmosphere to obtain the inorganic micro-nano fiber sponge thermal insulation material with the periphery sealed. The light flame-retardant building thermal insulation material is low in volu