Doctor of Philosophy, Case Western Reserve University, 2020, Chemical Engineering

High-energy density batteries are essential for powering future electric vehicles (EVs) and electric aircraft. These technologies are limited by the capacity of their batteries. Enabling high-specific energy batteries could make longer-range electric vehicles and electric aircraft a reality. The Li-metal anode offers the highest theoretical specific energy among practically available anode materials. However, secondary Li-metal anodes experience capacity loss and safety hazards caused by the growth of dendrites on the anode surface during charging. After four decades of research on Li-metal batteries, rechargeable Li-metal anodes that do not evolve dendrites are still not commercially available. Understanding the physical causes and mechanisms of dendritic Li electrodeposition, in order to develop commercial Li-metal batteries, motivates the present work. It is shown herein that solid-state transport limitations within a dynamic solid electrolyte interphase (SEI) are dominant in controlling the time when Li dendrites first form. Chronopotentiometry and optical imaging provide experimental observations for when dendrites first appear on a Li electrode. Dendrite onset time is shown to increase with increasing temperature and decrease with increasing current density and initial SEI thickness. These phenomena are shown to be due to the onset of diffusion limitations brought on by a thickening SEI. Electrochemical impedance spectroscopy (EIS) provides evidence for SEI growth and enables estimation of the SEI growth rates during Li electrodeposition. These experiments guide the development of an analytical model that explains mechanistically how transport limitations within the SEI control the onset time of dendrite growth during Li electrodeposition. The model also provides predictions of Li dendrite onset times. These predictions agree qualitatively with the observed effects of current density, initial SEI thickness, temperature, and pulsing. Finally, it is shown th (open full item for complete abstract)

Committee: Rohan Akolkar PhD (Advisor); Uziel Landau PhD (Committee Member); Donald Feke PhD (Committee Member); Alp Sehirlioglu PhD (Committee Member) Subjects: Chemical Engineering