The preparation method comprises the following steps: preparing PET non-
woven fabric raw paper, preparing a nano-
zinc oxide particle dispersion liquid, dipping the PET non-
woven fabric raw paper in a solution, carrying out heat treatment to form a functional PET non-
woven fabric, preparing a functional alkenyl
ionic liquid, carrying out heat treatment to form a PET non-woven fabric, and carrying out heat treatment to form the PET reinforced bi-crosslinked polyionic liquid composite
solid electrolyte. Adding a cross-linking agent, a
lithium salt, a
plasticizer and a
photoinitiator to prepare an
electrolyte precursor solution; the functional PET non-woven fabric is placed in the
electrolyte precursor solution, standing and dipping are carried out under the vacuum condition, then thermal
polymerization and photopolymerization are carried out, and the
solid electrolyte is prepared and applied to the
solid polymer lithium ion battery; the
zinc oxide particles are compounded into the PET non-woven fabric to form the non-woven fabric which is thin in thickness, high in tensile strength and appropriate in
porosity, and the non-woven fabric is cross-linked with the functionalized alkenyl
ionic liquid and the electrolyte precursor solution step by step, so that the
ionic conductivity, the
electrochemical window and the
thermal stability of the solid electrolyte and the safety performance of the battery in use are improved.