Lithium ion battery composite solid electrolyte and preparation method thereof

The invention discloses a lithium ion battery composite solid electrolyte and a preparation method thereof, and belongs to the technical field of lithium ion battery electrolyte. The preparation method comprises the following steps: (1) mixing an electrospinning precursor solution with an inorganic fast ion conductor uniformly, electrospinning to prepare a polymer matrix doped with the inorganic fast ion conductor, and aging to obtain a composite substrate; (2) dissolving lithium salt in a solvent, adding silicon methoxy-terminated oligomeric ethylene oxide, and reacting while stirring to obtain a polymer solution; (3) immersing the composite substrate obtained in the step (1) in the polymer solution obtained in the step (2), and vacuum drying to obtain the lithium ion battery composite solid electrolyte. The electrolyte prepared by the method of the present invention exhibits extremely high lithium ion conductivity, a wide electrochemical stability window, good mechanical property, and low interference imped