The invention relates to a method for manufacturing an electrochemical cell comprising an anode and a cathode separated by a separator and a gel electrolyte. The method comprises the steps of assembling the electrodes and the separator, and injecting a liquid electrolyte composition between the electrodes, the liquid electrolyte composition comprising a polymer, an aprotic liquid solvent and a lithium salt, wherein the polymer in the liquid electrolyte composition has functional groups capable of polymerizing via cationic polymerization, and the cell is submitted to an electrochemical cycling comprising a charging step and a discharging step.