Magnetically Ordered Bimettalic Oxide-Composite Pseudocapacitive Materials for Supercapacitors Applications

Abstract

The enhanced cycle stability, cycle lifetime, capacitance retention, and power densities of electrochemical capacitors make them an increasingly attractive option for modern energy storage needs, including grid level energy storage systems, mobile electronics, heavy construction equipment, military communication devices, power tools, public transportation, electric vehicles and capacitive water deionization systems to name a few. Recently, materials that displayed magnetoelectric coupling phenomena leading to enhanced magneto-capacitive properties are of particular interest, specifically ferrimagnetic spinels and hexagonal ferrites. This thesis is aimed at improving the capacitive performance of NiFe2O4 (NFO) and SrFe12O19 (SFO) based magnetically ordered pseudocapacitor electrodes by elucidating the effects of various nanomaterials preparation techniques on capacitance. The nanomaterials preparation techniques explored in this body of work include the addition of biomimetic dispersing agents, application of high energy ball milling, and forming composites using n-doped conducting pseudocapacitive polypyrrole polymers. Project 1 explored how the addition of gallocyanine dye (GCD) dispersing agent affects the capacitance of NFO. Additionally, the effects of the high energy ball milling (HEBM) process on capacitance were explored and these results were combined with the optimized gallocyanine dye results. Lastly NFO composites with Tiron-doped PPy were prepared at varying mass ratios and combined with optimized HEBM results to achieve the best capacitance results. Project 2 utilized the optimized GCD mass ratios with HEBM to enhance the capacitance of SFO. Tiron doped PPy was used with HEBM SFO at varying mass ratios to achieve the best performing composite electrode. Lastly, the best electrode composition from project 2 was used as anode in an aqueous asymmetric cell using MnO2 as the cathode, proving to be a viable anode chemistry in practical electrochemical capacitor applications.