Structural energy storage devices have drawn the attention of many researchers because load-carrying components can store electrical energy. Structural supercapacitor (SC) is a fast charging energy storage device and a component that withholds mechanical loading. We used an epoxy based adhesive polymer electrolyte for structural mediator-enhanced SCs. The epoxy based adhesive polymer electrolyte was composed of polyvinylidene fluoride (PVDF), lithium trifluoromethanesulfonate (LiTFS), and epoxy. In this work, the effects of LiTFS and epoxy on electrochemical and mechanical properties are investigated. The mass ratio of PVDF:LiTFS were 2:1, 1:1, 1:2 and 1:4 in this study whereas the concentration of epoxy was 0%, 10%, 20%, 30%, 40% and 50%. The ionic conductivity was evaluated by measuring the total conductivity and the electronic conductivity. The ionic conductivity decreases with the increase of epoxy concentration. The ionic conductivity reaches the maximum when PVDF:LiTFS=1:2 which is 0.015 S/cm. Mediators or redox species were used to dope the adhesive polymer electrolyte in the electrodes. The cyclic voltammetry (CV) curves of structural mediator-enhanced SCs fabricated using the epoxy based polymer electrolytes correlate with the trend of ionic conductivity. Tension tests were performed to evaluate Young’s modulus of mediator-enhanced SCs. The results indicate that epoxy component plays the key role to mechanical properties. Considering both electrochemical and mechanical properties, the best composition of the epoxy based electrolytes is defined.