Ultrahigh energy density supercapacitors through a double hybrid strategy

Herein, we are presenting all-solid-state symmetric supercapacitors (ASSSCs) with an innovative double hybrid strategy, where a hybrid material based on reduced graphene oxide (rGO) anchored with phoshotungstic acid, rGO-H3PW12O40) is combined with hybrid electrolyte (hydroquinone-doped gel electrolyte). Initially, a hybrid electrode is fabricated by decorating H3PW12O40 nanodots onto the surface rGO (rGO-PW12). Next, a symmetric cell based on rGO-PW12 electrodes was assembled with PVA-H2SO4 polymer gel-electrolyte. Interestingly, rGO-PW12 symmetric cell revealed a substantial enhancement in the cell performance as compared to parent rGO systems. It featured a widened potential range of 1.6 V, thereby providing 1.05 mWh/cm3 energy density. The electrochemical performance of rGO-PW12 cell was further advanced by introducing redox-active (hydroquinone) species in to the PVA-H2SO4 gel-electrolyte. Indeed, the performance of rGO-PW12 cell was surprisingly improved with an ultra-high energy density of 2.38 mWh/cm3 (more than two-fold)