Tuning antimony anodes through electrodeposition to inform on the reaction and degradation mechanisms in sodium-ion batteries
Electrification of portable devices, transportation, and large grid-level storage necessitate a portfolio of energy storage devices tailored to specific applications. Sodium-ion batteries are a naturally abundant alternative to lithium, but high performing anodes must be developed in order to reach widespread commercialization. Alloy-based anodes such as antimony (Sb) are attractive targets for their high theoretical capacities. However, the electrochemical performance of Sb is poor, and the reaction mechanism is poorly understood. Herein, antimony-based anodes for sodium-ion batteries are explored to elucidate sodiation pathways and investigate the role of electrode fabrication, electrolyte composition, and architecture on the reaction and degradation mechanism. Chapter I describes our research methodology and consists of our synthetic method of electrodeposition, materials characterization, battery assembly, and electrochemical characterization. Through this process, we can develop a better understanding of the electrochemical performance of alloy-based anode materials. The tunability of electrodeposition as a synthetic technique for the fabrication of Sb-based anodes is exploited in Chapter II. The effects of solution additives in the electrodeposition of Sb anodes are investigated and provide insight into how the morphology and crystallinity of the deposited anodes can be tuned. It was revealed that CTAB and SPS could significantly tune the electrodeposition of Sb films by altering the deposition by causing structural changes that either improved cycle life or rate capabilities. In Chapter III, electrodeposited and slurry cast Sb anodes were compared through differential capacity analysis, and it was demonstrated that electrode fabrication can significantly impact the sodiation/desodiation reaction pathway. Additionally, electrodeposited Sb anodes provided valuable insight into the mechanism without having to deconvolute the influences of binders and additives necessary in slurry casting. Chapter IV describes preliminary studies on how electrolyte composition can influence sodiation/desodiation reactions during Sb anode cycling. Traditional battery electrolytes are composed of carbonate species and salts, which are reduced onto the anode surface to form the solid electrolyte interphase (SEI). Due to the inherent volume expansion of Sb anodes when sodiated/desodiated, the SEI is hypothesized to continuously form and affect the cyclability of these anodes. In this investigation, we have found that electrolyte composition can influence the cycle life and sodiation/desodiation pathway, and we describe additional studies to probe how the SEI could hinder sodium ion transport. Chapter V builds upon Chapter II and explores how electrodeposition can be employed to develop three-dimensional (3D) electrodes to enhance the energy and power density of Sb-based anodes. Although we show that experimental parameters can be tuned to obtain uniform coverage, significant challenges in achieving conformal coverage of the current collector while maintaining high active material loading remain. The final chapter, Chapter VI, concludes the dissertation by describing further directions required to deepen the understanding of the degradation mechanism for Sb. We have begun to develop a 3D-printed optical, electrochemical cell that can couple operando optical studies with electrochemical studies to understand how electrode composition, structure, and electrolyte composition affect mechanical stability and ionic/electronic diffusivity in these electrodes. Understanding these fundamental processes and developing tools and characterization techniques to study alloy-based anode materials will lay the foundation for creating earth-abundant energy storage systems with high energy densities and long cycle life.
Includes bibliographical references.
Includes bibliographical references.
Embargo expires: 08/28/2025.