MS Thesis Defense by Benjamin Daermann, “Covalent Modification and Characterization of a Nonaqueous Redox Flow Battery Active Material”
SENG 115
Heather Blaser
508-999-8587
hblaser@umassd.edu
Title: “Covalent Modification and Characterization of a Nonaqueous Redox Flow Battery Active Material”
Advisor: Dr. Patrick Cappillino, Chemistry & Biochemistry Dept.
Committee Members: Dr. Sivappa Rasapalli, Chemistry & Biochemistry Dept.; Dr. Maricris L. Mayes, Chemistry & Biochemistry Dept.
Abstract:
With the rise in global energy demand, environmental concerns, and technological innovation in renewable energy. Renewable energy sources such as solar, wind, and hydroelectric power have become increasingly prevalent in supporting the electrical grid, both in the United States and globally. Unfortunately, the major drawback of renewable sources is their inability to maintain a constant electrical output. This intermittency has been one of the main reasons for not having a more heavily invested renewable power grid. The long-term solution is to increase the electrical storage grid. This would allow for storing energy produced during peak times and discharging it when electricity is needed. This has paved the way for the development of low-cost and high-efficiency energy storage technology. Among the vast array of potential storage methods, a promising technology is Redox flow batteries. This is because of their high adaptability and versatility in the power grid. The development of redox flow batteries using a nonaqueous system has the potential to achieve energy densities similar to those of lithium-ion batteries while maintaining key advantages, such as scalability.
In prior work from the Cappillino lab, vanadium bis-hydroxyiminodiacetate (VBH) has emerged as a promising active material candidate. VBH demonstrated excellent electrochemical stability and highly reversible one-electron redox chemistry. Additionally, VBH exhibits long-term cycle stability. The current drawbacks of this material stem from the high viscosity of concentrated solutions, modest voltage, and solubility that, while high, remains insufficient for high-energy-density energy storage applications. This thesis focuses on systematic modification of VBH. Herein is outlined the process developed to synthesize these asymmetric, modified compounds. A modular synthetic route was developed in which substituted bromoacetic acids were incorporated into the HIDA ligand precursor, enabling systematic alkyl substitution of the resulting vanadium complex. The other component used in the HIDA synthesis is N-hydroxylglycine, or (NHG), which is the component of HIDA that contains the other carboxylic group and the amine group. The resulting complexes were characterized by NMR spectroscopy, FTIR spectroscopy, and electrospray ionization mass spectrometry (ESI-MS), while their electrochemical behavior, such as reduction potential, was evaluated using cyclic voltammetry. Three modifications were successfully developed, including the addition of methyl-, ethyl-, and butyl- alkyl groups to the precursor material and, consequently, to the final vanadium compound. Furthermore, results indicate a shift in reduction potential upon substitution that could lead to a higher RFB capacity. The overall work establishes a versatile synthetic framework of systematic ligand modification of VBH, providing a foundation for future optimization of nonaqueous redox flow battery active materials.