In recent decades, redox-active electrolytes have been used in energy storage systems due to high specific capacitance originated from the Faraday reaction of electrode/electrolyte surface. Here, we provide an effective strategy that using H2SO4 as electrolyte with VOSO4 as redox additives to improve the electrochemical performances of the carbon felt (CF) electrode. The function of VOSO4 is that it can serve as a redox-active electrolyte to provide additional specific capacitance. The specific capacitance of 3.30 F cm (2) at 1 mV s (1) can be achieved, which is about 100 times of improved specific capacitance higher than that of the CF electrode tested in pure H2SO4. In addition, it also exhibits unexceptionable cycling stability without any specific capacitance loss after 2000 cycles at 5 mA cm (2). What's more, a novel all-solid-state supercapacitor is assembled using CF, gel electrolyte and membrane. The as-fabricated supercapacitor delivers a high specific capacitance of 234 mF cm(2) and fabulous cycle stability after 1200 cycles at the current density of 2 mA cm(2). Interestingly, three charged supercapacitors connected in series can light a red light-emitting diode effectively for about 24 min. Hence, such mixed electrolyte and electrode materials will hold great potential for high performance supercapacitor applications. (C) 2020 Elsevier Inc. All rights reserved.