Gimble, Nathan Jacob, authorPrieto, Amy, advisorAckerson, Christopher, committee memberRappe, Anthony, committee memberPopat, Ketul, committee member2022-08-292022-08-292022https://hdl.handle.net/10217/235738Sodium-ion batteries offer a more sustainable energy storage alternative to lithium while maintaining many of lithium's important characteristics. The solid electrolyte interphase (SEI) forms on the surface of the anode in both sodium and lithium-ion batteries. The SEI effects battery performance, particularly in sodium batteries, and understanding how it forms is critical for developing sodium ion batteries. Chapter I of this dissertation motivates sodium ion batteries, outlines the important differences between sodium and lithium, introduces the SEI, and establishes how the SEI is studied, ultimately placing this work in context with the field. As the SEI is derived from the electrolyte and is affected by electrolyte additives, the small molecule electrolyte additive fluoroethylene carbonate (FEC) is introduced as it is investigated throughout the dissertation. Chapter II explains how X-ray photoelectron spectroscopy can be used to study the SEI, providing examples of important protocols and pitfalls. Chapter III examines SEI formation by correlating electrochemistry from differential capacity with X-ray photoelectron spectroscopy (XPS). It is revealed that SEI species appear as a result of applied chemistry when the small molecule additive FEC is present. Without FEC, the SEI is present without significant electrochemistry in the differential capacity. Chapter IV builds off the results in Chapter III, identifying the conditions of spontaneous SEI formation due to sodium metal reactivity with the electrolyte. The spontaneous formation of the SEI is mitigated by FEC, the role of which is understood to be pre-passivation of sodium metal to prevent further electrolyte decomposition. Chapter V summarizes the work in this dissertation and outlines different directions the work can take moving forward.born digitaldoctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.electrolytesolid electrolyte interphaseXPSSEIbatteryX-ray photoelectron spectroscopyText