All solid-state supercapacitors were prepared using activated carbon, polymer electrolytes, i.e. Nation and mediators, I-/I3-. The mediators have potential to provide high pseudocapacitance and to greatly reduce the internal resistance. Cyclic voltammetry studies were conducted to evaluate the specific energy, specific power and stability of the mediator-enhanced polymer electrolyte supercapacitors (MEPESCs). Scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, surface area and porosimetry studies were conducted to examine the structural and chemical characteristics of the MEPESC electrodes. The results indicate that the leakage free MEPESCs not only provide high specific energy and power but also ease and flexibility for fabrication and packaging of energy storage devices. The results also suggest that the MEPESCs can be further improved by mitigating the aggregation/segregation of the mediators, eliminating the surface coating, promoting solvation of iodine ions, and reducing crossover of iodine.