Advanced materials and colloidal fabrication strategies for supercapacitor anodes

Abstract

The development of high-performance anodes for supercapacitors (SCs) is critical to advancing energy storage technologies for applications such as electric vehicles, regenerative braking systems, aerospace, and portable electronics. This research presents a comprehensive approach to designing magnetically ordered pseudocapacitive electrodes based on iron oxide systems, particularly γ-Fe₂O₃, with high active mass loading (up to 40 mg·cm⁻²). Metastable γ-Fe₂O₃ was successfully synthesized using biocompatible organic alkalizers such as meglumine, and catecholate-type molecules like caffeic acid, enabling precise control over particle size and crystal phase. These materials exhibit significant redox activity and ferrimagnetic behavior, with areal capacitance values reaching up to 4.49 F·cm⁻². To overcome the inherent low conductivity of transition metal oxides, multiwalled carbon nanotubes (MWCNTs) were incorporated, and high-energy ball milling (HEBM) was employed to eliminate agglomerates and enhance dispersion. A suite of multifunctional capping and dispersing agents, including gallocyanine, quercetin, hematoxylin, and tetrahydroxy-1,4-quinone, was introduced to improve colloidal stability, facilitate charge transfer, and contribute additional redox activity. Furthermore, core-shell nanostructures were fabricated by coating γ-Fe₂O₃ and MWCNTs with polypyrrole (PPy), achieving exceptional areal capacitance values of up to 6.22 F·cm⁻² and low resistance (<0.5 Ω). This work demonstrates a unified strategy that integrates material synthesis, functional additives, and colloidal design to create scalable, magnetically active, and electrochemically efficient electrodes. The results open new pathways for the development of multifunctional SCs with superior performance.