NOVELTY - An electrochemical cell comprises a curable perfluoro-sulfonate ionomer based electrolyte composition containing 10-50 wt.% perfluoro-sulfonate ionomer comprising acidic groups for transporting protons; 10-89 wt.% monomer for dissolving the ionomer; and 1-60 wt.% cross-linking agent having at least two vinyl functionalities. Upon combining the above components, a curable electrolyte solution is formed with greater than or equal to50 wt.% of the above components.    USE - For polymer electrolyte membranes used in electrochemical devices, e.g. fuel cells (claimed) or batteries.    ADVANTAGE - The inventive electrochemical cell becomes soft and pliable at lower temperatures and can be brought into intimate contact with catalyzed electrodes of arbitrary three-dimensional shape without the use of high temperature compression methods.    DETAILED DESCRIPTION - INDEPENDENT CLAIM are also included for:    (A) a fuel cell with a curable electrolyte comprising 10-50 wt.% perfluoro sulfonate ionomer (PFSI) comprising acidic groups for transporting protons, 10-89 wt.% polar monomer, a polar solvent for dissolving the polar monomer, and 1-60 wt.% cross-linking agent having at least two vinyl functionalities; and    (B) a method for producing a curable liquid electrolyte for an electrochemical cell.    Upon combining the PFSI, polar vinyl monomer, polar solvent, and cross-linking agent, a curable electrolyte solution is formed with greater than or equal to50 wt.% of the above components. The curable liquid electrolyte is produced by mixing a PFSI solution with a solvent comprising a monomer and a cross-linking agent forming a mixture. The cross linking comprises at least two vinyl functionalities. The solvent is removed from the mixture by distillation to obtain a curable PFSI electrolyte. The curable PFSI electrolyte is disposed on a substrate forming an intermediate. The intermediate is treated to form a cured electrolyte with increased viscosity and increased structural strength.    DESCRIPTION OF DRAWING(S) - The figure schematically shows an electrochemical cell incorporating a membrane of the proton exchange membrane of the invention.    Solid polymer electrolyte (10)    Gas diffusion electrodes (20, 30)    Membrane electrode assembly (40)    Flow plates (50, 60)    Electrochemical cell (70)