Carbon materials have enjoyed wide applications in supercapacitors because of their high surface area which guarantees a high power output through the formation of an electric double layer (EDL). However the energy stored by this EDL mechanism is often insufficient and as such there is the need to upgrade them for higher energy applications. Quinone materials are attracting interest because of their pseudocapacitance contributions which help to boost the energy density of supercapacitors. In this study, composite supercapacitor electrodes are prepared by mechanically mixing 2,3,5,6-tetrachloro-1,4-benzoquinone (TCBQ) and activated carbon. An investigation of 5% w/w and 10% w/w of this quinolic material as a pseudocapacitance material to activated carbon in 1 M HCl aqueous electrolyte delivers a specific capacitance of 236 F g−1 and 240 F g−1 comparable to 190 F g−1 of just activated carbon over a potential range of −0.3 V–0.9 V vs Ag+/Ag. Contrary to what is commonly observed, this material is highly insoluble in the electrolyte medium and remains stable with cycling, recovering 99.57% (for 10% w/w addition) and 99.13% (for 5% w/w addition) of its initial capacitance after cycling at 500 mV s−1 scan rate. The findings in this report potentially provides a cheaper yet efficient route to boost the energy density of activated carbon using TCBQ for high energy supercapacitor applications.