Mn₃O₄ and (ZnFe)OOH Composites for Supercapacitors with High Active Mass

A new colloidal method has been developed for the fabrication of Mn₃O₄-carbon nanotube (CNT) composites for positive electrodes of supercapacitors and areal capacitance of 5.04 F cm⁻² has been achieved. In this method, chemical precipitation of Mn₃O₄ was performed in the presence of carbon nanotubes, dispersed using a tolonium chloride dye. An electrostatic heterocoagulation mechanism has been developed, which allowed for enhanced mixing of Mn₃O₄ and CNT, and resulted in enhanced electrochemical performance at high active mass of 36 mg cm⁻². Testing results revealed changes in microstructure and oxidation state of Mn during cycling, which allowed for enhanced capacitance. In order to utilize the high capacitance of the positive Mn₃O₄-CNT electrodes in supercapacitor devices, advanced negative electrodes have been developed. (ZnFe)OOH-polypyrrole coated CNT electrodes with enhanced areal capacitance in a negative potential window have been fabricated. Asymmetric devices showed promising performance in a voltage window of 1.6 V.