| dc.description.abstract | Charge ordering resulting from the localization of electrons in periodic potential wells is a characteristic manifestation of strongly electron correlation in periodic solids. Synthetic approaches that allow for independent control over composition and crystal structure provide a means to independently modulate the strength of electron correlation across different polymorphs of the same compound as a result of the strong coupling of spin, charge, orbital, lattice, and atomic degrees of freedom. Binary, and ternary vanadium oxides represent a promising system to systematically tune electron correlation because of the availability of multiple, easily accessible redox states (V5+/V4+/V3+); a wide range of structural and bonding motifs accessed through connecting tetrahedral, square pyramidal, and octahedral units VOx units; and the ability of extended V2O5 frameworks to intercalate ions spanning the periodic table to yield a diverse palette of ternary phases with the composition MxV2O5. Navigating “rugged” energy landscapes across this system to identify local minima, each representing a metastable polymorph, holds much promise for accessing a greatly expanded set of bonding motifs and functional properties and for exploring the interplay between spin, charge, orbital, lattice, and atomic degrees of freedom.
In this dissertation, an extensive toolset of topochemical transformations has been developed, yielding metastable binary V2O5 phases. Furthermore, efforts to independently tune the composition (i.e., the identity of M and its stoichiometry, x) and structure (i.e., the connectivity of the V—O framework) across binary and ternary (and even quaternary) vanadium oxides have been detailed. These approaches have served to elucidate structure—property relationships in these systems and further facilitated control over electron correlation, electronic structure, and ion diffusion pathways, enabling the design of candidate materials for neuromorphic computing, insertion cathodes of lithium and “beyond lithium” batteries, and photocatalysis. Some salient functional properties accessed within this materials palette include the first high voltage, high capacity, and high cyclability insertion host for Mg ions, ζ-V2O5; a metastable β-SnxV2O5 compound that resolves the longstanding challenge of photocorrosion of light-harvesting quantum dots; and layered materials that afford control over electron correlation as a function of layer thickness and degree of hydration of inserted cations. | en |
