Abstract

Lithium-based batteries degrade through coupled physical and chemical mechanisms that limit their performance, lifetime, and reliability. Many of these mechanisms cause the cell to expand or build up internal pressure, making the mechanical response of a cell a direct, real-time indicator of degradation. This dissertation establishes operando mechanical pressure measurements as a robust tool for studying aging across both lithium-ion (Li-ion) and lithium-oxygen (Li-O2) batteries, linking mechanical signals to specific aging mechanisms. The first part investigates pressure build-up in volumetrically constrained commercial LCO/graphite Li-ion pouch cells as the cells are cycled across a range of C-rates (1C, 2C, 3C) and temperatures (10, 25, 40 °C). By analyzing the pressure changes, the contributions of SEI growth, electrolyte decomposition, and lithium (Li) plating are separated. Li plating, rather than electrolyte decomposition, is identified as the dominant cause of the irreversible pressure rise at high C-rates and low temperatures, supported by EIS and post-mortem SEM/EDS analysis. The second part extends this approach to Li-O2 cells, where storage-induced degradation has been largely unexplored. Operando pressure follows the corrosion and interphase growth of the Li-metal negative electrode during storage, and is combined with EIS, SEM/EDS/XPS, mass change, and performance tests. Cells stored under argon show stable pressure and impedance, whereas O2-containing environments cause increasing pressure build-up, Li thickening, electrolyte loss, and loss of reversibility. The gas environment governs the rate of degradation, establishing mechanical pressure as a real-time, quantitative measure of calendar aging. The third part introduces operando force measurements to track charging reversibility and negative-electrode expansion in Li-O2 cells during cycling. An equivalent mechanical model relates the measured force to lithium thickness change, and force change per unit capacity (dF/dQ) is used to distinguish productive Li plating from parasitic reactions. This approach is validated against TiOSO4 titration and cross-sectional imaging. Together, these studies show that operando mechanical measurements provide a non-destructive means of resolving specific aging mechanisms across multiple lithium battery chemistries, complementing conventional electrochemical diagnostics and offering a practical route toward understanding and mitigating battery degradation.

Committee Chair

Xianglin Li

Committee Members

Christopher Cooper; Mark Meacham; Peng Bai; Vijay Ramani

Degree

Doctor of Philosophy (PhD)

Author's Department

Mechanical Engineering & Materials Science

Author's School

McKelvey School of Engineering

Document Type

Dissertation

Date of Award

8-3-2026

Language

English (en)

Download

Available for download on Sunday, January 31, 2027

Share

COinS