Enhanced electrochemical behaviors of carbon felt electrode using redox-active electrolyte for all-solid-state...

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.