In the last years great efforts were devoted to improve the energy density and the stability of supercapacitors using low cost and environmentally friendly materials. Unfortunately, it was found that supercapacitors exclusively based on capacitive process with carbon-based electrodes and aqueous electrolytes showed limited energy density and stability. In fact, although supercapacitors based on carbon materials with very high specific surface area gave specific capacity exceeding 200 F/g in aqueous electrolyte, the stability became problematic when the potential was kept at 1.5V or higher for long time for the concomitant presence of side irreversible reactions. Recently, many researchers have focused their attention on alternative ways to improve capacitance and energy density consisting in introducing faradaic processes (i.e., with exchange of electrons at the interface electrode /electrolyte) on an electrode of device. Thus one electrode exhibited a higher capacitance and also the capacitance and the energy density of supercapacitor increased. In this work we have studied supercapacitors based on a carbon material coupled with different types of separators and electrolyte solutions to overcome the above limits. Preliminary studies were performed to confirm the limitation of the purely capacitive process to which followed studies that evidenced the positive effect of reversible redox reaction. Four different supercapacitors were realised and studied varying the type of separator (porous paper and sulfonated polyether-ether ketone membrane) and electrolyte solution (sodium sulphate and potassium iodide). A solution of potassium iodide, whether used at the positive electrode, where I-/I3- redox reaction occurred, produced a remarkable additional pseudocapacitance. A specific capacitance of 208 F/g at 1.6 V and stable performance after 20000 of charge/discharge cycles and subsequent 300h of floating condition at 1.6V were obtained from supercapacitor with sPEEK membrane and KI solution as well as a high value of energy density of 20 Wh/kg of capacitor was displayed.
Performance of carbon-based supercapacitors with inert and redox electrolytes
Pietro Staiti;Alessandra Carbone;Irene Gatto;Francesco Lufrano
2017
Abstract
In the last years great efforts were devoted to improve the energy density and the stability of supercapacitors using low cost and environmentally friendly materials. Unfortunately, it was found that supercapacitors exclusively based on capacitive process with carbon-based electrodes and aqueous electrolytes showed limited energy density and stability. In fact, although supercapacitors based on carbon materials with very high specific surface area gave specific capacity exceeding 200 F/g in aqueous electrolyte, the stability became problematic when the potential was kept at 1.5V or higher for long time for the concomitant presence of side irreversible reactions. Recently, many researchers have focused their attention on alternative ways to improve capacitance and energy density consisting in introducing faradaic processes (i.e., with exchange of electrons at the interface electrode /electrolyte) on an electrode of device. Thus one electrode exhibited a higher capacitance and also the capacitance and the energy density of supercapacitor increased. In this work we have studied supercapacitors based on a carbon material coupled with different types of separators and electrolyte solutions to overcome the above limits. Preliminary studies were performed to confirm the limitation of the purely capacitive process to which followed studies that evidenced the positive effect of reversible redox reaction. Four different supercapacitors were realised and studied varying the type of separator (porous paper and sulfonated polyether-ether ketone membrane) and electrolyte solution (sodium sulphate and potassium iodide). A solution of potassium iodide, whether used at the positive electrode, where I-/I3- redox reaction occurred, produced a remarkable additional pseudocapacitance. A specific capacitance of 208 F/g at 1.6 V and stable performance after 20000 of charge/discharge cycles and subsequent 300h of floating condition at 1.6V were obtained from supercapacitor with sPEEK membrane and KI solution as well as a high value of energy density of 20 Wh/kg of capacitor was displayed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
