Date of Award
Spring 5-15-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Li metal batteries are promising candidates for next-generation rechargeable batteries due to their high energy density and low redox potential. However, dendritic Li growth which can easily lead to short-circuit and cell failures have been a major hurdle that prevented the commercialization of metal anodes. The onset of dendrites occurs when the salt concentration gets depleted at the electrode surface, which can be predicted by the classical dilute solution theory and Sand’s equation. However, deviations from the theoretical predictions were often reported, and the dendrites were still observed in current densities orders of magnitude lower than the system-defined limiting current density. Moreover, the exact penetration dynamics and the transport process inside the porous, tortuous separators or solid electrolytes remained elusive. In this dissertation, the special operando capillary cells were utilized to visualize the penetration process during the polarization, while ensuring the minimization of heterogeneous current distributions. To fully understand the penetration dynamics on practical systems, the effect of local geometry on the transport process was assessed, while for the solid polymer electrolytes, the effects of temperature and dynamic changes of the modulus were analyzed. Our results suggest that the channel geometries, mechanical driving force, and level of heterogeneity significantly altered the penetration dynamics compared to the ideal liquid electrolytes. We also utilized the electrokinetic effect of deposited surface charges on the channel walls to further modulate the penetration dynamics, which lead to the development of bipolar separator systems that significantly prolonged the cycle life. Throughout this work, mathematical modeling and COMSOL simulations were utilized to validate our experimental results and test different cell environments. The fundamental scientific insights gained from both the experiments and mathematical analysis enabled the modulation of penetration dynamics, allowing the development of practical applications that can be used the mitigate dendritic growth issues and realize safer metal batteries.
Language
English (en)
Chair
Peng P. Bai
Committee Members
Young-Shin Y. Jun, Vijay V. Ramani, Elijah E. Thimsen, Julio J. D’Arcy,