A non-aqueous, mechanically-stable, proton conducting gel polymer electrolyte has been prepared for Electrochemical Capacitor (supercapacitor) applications. It is based on 2-hydroxymethylmethacrylate monomer mixed with two different solvents (propylene carbonate and N,N-dimethylformamide). It was shown that the capacitive performance changes with the gel electrolyte composition. The proton conduction type mechanism affects ions mobility and transport into the porous carbon electrode. Addition of small amounts of DMF solvent leads to a change in the conduction mechanism from a vehicleto a Grotthuss-type, and capacitance of 90 F g-1 at 20 °C was achieved using a 15 wt. % DPhHPO4/P (HEMA)/30 wt. % DMF–70 wt. % PC gel composition. Electrochemical tests were done in a large temperature range (from -40 to 80 °C). The cell delivered a capacitance of 54 F g-1 at -40 °C, that is 60% of the value obtained at room temperature, and 90 F g-1 at 80 °C within voltage window of 1 V.