A method of producing a rechargeable lithium battery cell, the method comprising (a) preparing a liquid electrolyte solution comprising an ion-conducting polymer dispersed in a first liquid solvent and an optional lithium salt dissolved in the first liquid solvent; (b) impregnating the electrolyte solution into the cathode, the anode, a porous structure of the separator, or the battery cell; (c) removing the first liquid solvent; and (d) impregnating a second liquid solvent, comprising an optional lithium salt dissolved therein, into the cathode, the anode, the separator porous structure, or the battery cell; wherein the ion-conducting polymer comprises a polymer having an ion conductivity from 10−8 S/cm to 10−2 S/cm when measured at room temperature without the presence of a liquid solvent and the polymer does not occupy more than 25% by weight of the cathode, not counting a current collector weight.