Chemical synthesis of vanadium oxide and its composites for solid state supercapacitor application

Abstract

Electrochemical energy storage that is fast, durable, and safe is vital to the transition toward electrified mobility and distributed renewables. Supercapacitors bridge the performance gap between batteries (high energy, moderate power) and classical capacitors (very high power, low energy) by enabling rapid charge discharge with long cycle life. Among pseudocapacitive materials, vanadium oxides (notably Vand#8322;Oand#8325;) are attractive because their multiple accessible oxidation states support fast and reversible faradaic reactions. However, pristine Vand#8322;Oand#8325; suffers from modest electronic conductivity and structural instability during repeated cycling, which can limit rate performance and lifetime in solid-state configurations. newlineThis thesis addresses these limitations through a synthesis structure property device workflow that develops Vand#8322;Oand#8325;-based thin films and complementary composites tailored for solid-state/asymmetric supercapacitors (ASCs). The central idea is to integrate Vand#8322;Oand#8325; with conductive/ionically accessible partners binary/ternary metal oxides and carbonaceous phases to (i) accelerate charge transport, (ii) stabilize the redox-active lattice, and (iii) engineer porosity and interfacial chemistry that promote rapid ion access and high-rate operation. Objectives were fourfold: (1) synthesize phase-pure Vand#8322;Oand#8325; thin films and composite variants using scalable wet chemical routes compatible with steel substrates; (2) elucidate crystallographic, microstructural, and optical features that govern charge storage; (3) quantify electrochemical behavior by cyclic voltammetry, galvanostatic charge discharge, and impedance spectroscopy; and (4) translate optimized electrodes into flexible/solid-state ASC devices against activated carbon (AC) counter electrodes, benchmarking energy/power metrics and cycling durability. newlineMethods and Characterization. Vand#8322;Oand#8325; thin films and composites with MnOand#8322;, NiCoand#8322;Oand#8324;, and carbonaceous domains were prepared via solution processing/chemical bath strategies followed by controlled thermal treatments. S