2026 Theses Doctoral

Structure-Property Optimization of Organic Materials for Li and Mg Batteries

Harrison, Kelsey L.

High atmospheric carbon levels driven by global energy demands necessitate the development of energy storage systems based on sustainable materials. Organic materials and earth abundant metals can support this initiative with chemical design principles driving the progress of their performance. Magnesium is a promising metal anode alternative to lithium for its reducing power and high capacity but faces challenges in battery performance due to ion transport limitations from its divalent charge. Organic materials also face challenges in their electrochemical performance compared to inorganic systems, but present an opportunity for safer, non-toxic alternatives.

This research focuses on overcoming these challenges by developing structure-property relationships in three organic electronic material systems that enable their performance optimization in lithium and magnesium metal anode based batteries. The novel materials are synthesized and electrochemical testing is performed to understand the influence of structural design on resulting behavior. Key findings include: (1) a distinct "medium" polymer length helical perylene diimide cathode achieves optimal rate performance in Li and Mg systems (2) a block-brush polymer structure with distinct fluorinated and PEG rich side chain regions on a central polysiloxane backbone promote ideal Li+ and TFSI− interactions for an all solid-state polymer electrolyte in a Li-metal battery, and (3) the symmetry of phenoxazine-based isomers significantly influences their redox behavior as p-type cathodes.

Chapter 1 provides an introduction to energy storage systems with a focus on Li and Mg metal anodes and organic materials.

Chapter 2 focuses on finding (1) that a "sweet" spot in polymer length of a helical perylene diimide organic cathode enables fast ion transport in Li and Mg metal batteries.

Chapter 3 focuses on finding (2) that polysiloxane-based polymer electrolyte performance can be tuned by systematically alternating the sequence of side chains with complementary properties for Li transport and SEI formation in Li metal batteries. Challenges are presented for the Mg metal system.

Chapter 4 focuses on finding (3) that regioisomers of phenoxazine-based molecules are good organic cathode candidates with distinct electrochemical behavior for further performance optimization.