Dissertation Defense: John Waugh, Interdisciplinary Materials Science
DISSERTATION DEFENSE
John Waugh, Interdisciplinary Materials Science
*under the direction of Peter Pintauro
“Electrospun Electrodes for Lithium-Ion Battery Anodes and Capacitive Deionization”
03.24.23 | 1:15PM CST | 048 Engineering Science Building (ESB) | Zoom
Electrospinning is a promising approach for fabricating energy storage materials with significant morphological control. Electrospun fibers provide an inherently porous template that can be easily modified with additives and treated to enhance electrode performance for specific applications. This dissertation will discuss two approaches to developing electrospun fiber electrodes for energy storage devices. First, a silicon-based lithium-ion battery anode made through simultaneous electrospinning/electrospraying is presented. Silicon/polyacrylic acid nanofibers are electrospun with a carbon/polymer (polyamide imide or polyvinylidene fluoride) particle electrospray and used as freestanding electrodes. This method builds layered structures of silicon, carbon, and flexible polymeric binder that allows for tuning of the content of each component of the electrode. The effects of electrospray binder choice, anode loading, and carbon content are investigated. Dispersing carbon throughout the electrode this way allows for improved electrical connection to the silicon, enabling longer cycle life. These anodes are able to maintain stable gravimetric capacities higher than graphite for over 600 cycles. The second approach detailed here utilizes electrospun carbon nanofibers as capacitive deionization (CDI) electrodes. Hierarchical porosity is generated through a successive etching approach with the goal of improving ion adsorption capacity and rate. Sacrificial mesopore former type (organic and inorganic) and content is explored to determine optimal conditions for electrochemical and CDI performance. The best mesopore forming conditions are then expanded upon using micropore etching to create hierarchical porosity. The conditions of micropore etching are studied to determine effects on morphology, composition, and resulting performance. The resulting hierarchically porous fibers benefit from the compounding etching strategy and outperform fibers with only one etching technique. Overall, this work seeks to utilize the variable template of electrospinning to provide insight into the role of electrode morphology and composition on resulting electrode. Electrospun electrodes are uniquely useful for energy storage devices due to their inherent macroporosity and high tunability which allows them to be easily modified to fit a specific application.