Thesis (Ph. D.)--University of Rochester. Department of Chemistry, 2019.
Innovation in the development of electrochemical energy storage (EES) methods is
essential if these technologies are to meet the variable needs of the electrical grid.
Nonaqueous redox flow batteries (NRFBs) represent an underdeveloped area of research
in energy storage—one which has seen a recent spike in interest owing to the potential for
modular, energy-dense electrochemical energy conversion. Summarized herein, a subclass
of polyoxometalates, the polyoxovanadium alkoxides (POV-alkoxides), are explored
for application as charge carriers for nonaqueous electrochemical energy storage. Chapter
2 describes our initial investigations into the physical and electrochemical properties of the
homoleptic POV-alkoxide series, [V6O7(OR)12], demonstrating the capability for these
systems to serve as multi-electron charge carriers in symmetric NRFB schematics. Chapter
3 builds upon this work, exploring selective ligand functionalization at a single face of the
POV-alkoxide for the purpose of increasing the solubility of this system in acetonitrile.
Chapter 4 explores the use of mixed solutions of POV-alkoxides as NRFB charge carriers,
demonstrating how synergistic behavior can yield improved physicochemical properties
for a classically “impure” system. Lastly, Chapter 5 describes the synthesis and
electrochemical characterization of a series of heterometal-functionalized POV-alkoxides,
demonstrating how heterometals can be used to tune the redox properties of the series.
These mixed metal complexes are also characterized in the context of NRFB application,
revealing the influence of a heterometal on electrochemical performance.
Through these studies, we have demonstrated how targeted synthetic strategies,
including homoleptic ligand substitution, selective ligand functionalization, and heterometal installation, represent rational methods for tuning the physicochemical
properties of POV-alkoxides with relevance to NRFB application (stability, n, Cactive, Vcell).
In doing so, we identify the critical molecular parameters of this class of compounds (e.g.
ligand identity, surface symmetry, metal composition) that translate to optimal
functionality in nonaqueous energy storage. These physicochemical improvements
imparted to the POV-alkoxide series highlight the power of synthetic inorganic chemistry
in addressing the long-standing issues with stationary energy storage. Moreover, the
insights into the structure-activity relationships of these POV-alkoxide charge carriers will
serve to inform future design strategies for polynuclear systems with relevance to
applications in EES.
