Redox mediator induced electrochemical reactions at the electrode-electrolyte interface: Making sodium-ion supercapacitors a competitive technology

Abstract

The specific capacitance values of Na-ion supercapacitor can now compete with other well-established pseudocapacitors. This is obtained by using redox additive modified electrolytes in combination with hierarchical nanostructures of NaMnPO4. Modifying the conventionally used electrolyte, that is: NaOH, with redox additives such as potassium ferricyanide [K3Fe(CN)6] and potassium iodide (KI), can induce nearly 50% enhancement in the specific capacitance. The enhancement is also retained in full cell, fabricated using NaMnPO4 and activated carbon as the positive and negative electrodes, respectively. Redox mediators stimulate extra redox pairs and higher ionic conductivity, leading to enhanced electrochemical reactions at the electrode-electrolyte interface.