Environment-friendly composite polymer solid electrolyte membrane and preparation method thereof

The invention relates to an environment-friendly composite polymer solid electrolyte membrane and a preparation method thereof, and the composite polymer solid electrolyte membrane is of a three-layer structure, namely a middle layer membrane and spinning layers spun on two sides of the middle layer membrane, based on the polymer matrix, the formula comprises the following components in percentage by mass: 16-50w% of polymer matrix, 16-50w% of lithium salt, 1-10wt% of cellulose nanofiber, 15wt% of plasticizer and the balance of solvent. The preparation method comprises the following steps: S1, preparing a dispersion liquid A; s2, preparing a solution B; s3, preparing a middle layer film: pouring the solution B into a polytetrafluoroethylene mold, and drying to remove the solvent to obtain a middle layer film A; s4, preparing an electrostatic spinning precursor solution C; and S5, preparing the composite polymer solid electrolyte membrane. By adding the cellulose nanofiber, the crystallinity of the electrolyte