Method of making polymer electrolyte electrochemical cells

The invention relates to a method for the preparation of a polymer electrolyte electrochemical cell using an electrolyte precursor, said precursor comprising one or more solvents, one or more salts and a polymer which dissolves in the solvent at a first temperature (Tdissol) and which is capable of forming a gel on subsequent cooling following heating to a second temperature (Tgel). Tdissol being lower than Tgel, which method comprises: (a) heating the electrolyte precursor to Tdissol; (b) optionally cooling the electrolyte precursor, (c) incorporating the electrolyte precursor into the electrochemical cell; (d) heating the electrochemical cell to Tgel; (e) cooling the polymer electrochemical cell to ambient temperature to bring about gelling of the polymer electrolyte. Preferably the polymer is a homopolymer or copolymer from the group of monomers of vinyl fluoride, vinylidenefluoride, trifluoroethylene, tetrafluoroethylene and hexafluoropropylene.