Proton and lithium-ion conducting biodegradable solid polymer electrolytes were prepared using blends of poly(styrene sulphonic acid) (PSSA) and starch for supercapacitor applications. The ionic conductivities have been calculated using the bulk impedance obtained through impedance spectroscopy with varying blend ratio and plasticizer. Glycerol as plasticizer improved the film formation property, while lithium perchlorate (LiClO4) as dopant enhanced the conductivity. The maximum conductivity has been found to be 5.7 x 10(-3) Scm(-1) at room temperature for 80/20 (PSSA/starch) blend ratio. The dielectric studies showed relaxation peaks indicating proton and Li+ conduction in the plasticized polymer blend matrix and dielectric modulus also exhibited a long tail feature indicating good capacitance. Differential scanning calorimetry thermograms showed two peaks and decreased with varying blend ratio and plasticizer. A carbon-carbon supercapacitor was fabricated using suitable electrolyte, and its electrochemical characteristics using cyclic voltammetry, AC impedance and galvanostatic charge-discharge were studied. Supercapacitor showed a fairly good specific capacitance of 115 Fg(-1) at 10 mV s(-1).