Abstract

Next-generation high-capacity batteries often rely on electrochemical formation processes rather than conventional intercalation alone. Such processes include lithium metal deposition and Li–O2 discharge-product formation, in which new phases form at the electrochemical interface during operation. As a result, the measured response reflects both electrochemical driving forces and the evolving product morphology. This coupling makes it difficult to interpret electrochemical data, microscopic observations, or model results in isolation. This dissertation examines this problem through three main studies and one preliminary extension on Li–O2 batteries and lithium metal deposition, each addressing a different factor that affects how electrochemical product formation is measured, modeled, or interpreted. The first study investigates insulating Li2O2 formation in Li–O2 batteries. A phase-field model is coupled with coupled ion–electron transfer (CIET) kinetics and compared with a Butler–Volmer (BV)-based description. The two kinetic descriptions lead to different predictions of voltage response, kinetic overpotential, nucleation behavior, surface coverage, and morphology evolution. Experimental observations of Li2O2 products formed under different current densities and electrolyte conditions are used to evaluate the model predictions. The results demonstrate that the kinetic description influences the simulated growth behavior and the mechanistic interpretation of insulating product formation. The second study examines lithium metal deposition under pulsed-current conditions. Electrochemical impedance spectroscopy provides a timescale reference for selecting pulse frequencies. Deposition under pulsed and constant current is compared using operando microscopy, postmortem scanning electron microscopy, and cycling measurements. The comparison shows that pulsed current does not have a universal effect on lithium deposition. Intermediate frequencies promote more coalesced growth in a less mechanically constrained configuration. Under stacking pressure, pulsed current does not clearly change the surface morphology or average Coulombic efficiency, but selected pulse frequencies reduce cell-to-cell variability. These results indicate that the effect of pulsed current depends on both interfacial timescale and mechanical constraint. The third study develops an operando linear sweep voltammetry (LSV) approach for studying lithium deposition in confined capillary cells. By varying scan rate and electrode separation, this study identifies a bounded measurement window in which a plateau-like, weakly scan-ratedependent response can be used to follow multiple stages of lithium deposition during a single sweep. Under a representative condition within this window, characteristic points along the LSV response capture the progression from non-localized surface growth to localized growth and dendritic structures. Constant-current measurements near the LSV-derived current range further support that deposition behavior changes over a narrow current range identified from the LSV response. A preliminary extension of the third study examines surface-charge effects on morphological instability in lithium metal electrodeposition. Layer-by-layer polyelectrolyte treatment is used to prepare distinguishable capillary wall surface states, and LSV and constant-current deposition are compared using operando microscopy. The treated capillaries show changes in the LSV-associated growth sequence, but the results do not indicate a simple charge-sign-dependent change in deposition stability. Instead, the surface-treatment effect depends on the electrochemical protocol used to probe the system. Together, these studies show that electrochemical response, morphology, and model output are shaped by the kinetic description, current protocol, interfacial boundary condition, and measurement condition used to generate them.

Committee Chair

Peng Bai

Committee Members

Donsub Rim; Feng Jiao; Vijay Ramani; Xianglin Li

Degree

Doctor of Philosophy (PhD)

Author's Department

Energy, Environmental & Chemical Engineering

Author's School

McKelvey School of Engineering

Document Type

Dissertation

Date of Award

6-23-2026

Language

English (en)

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