Mapping the Complex Patterns of Degradation in Commercial Lithium-Ion Batteries Using X-Ray Imaging and Diffraction

Abstract

Understanding and mitigating degradation in Li-ion batteries is a major area of focus in the electric vehicle industry. Studying battery degradation often requires long-term cycling experiments, which are best done with machine-made cells using commercial form factors to accurately represent real- world operating conditions.

In this thesis, we use synchrotron-based X-ray imaging and diffraction to comprehensively study the structural and functional changes that occur in commercial cells after thousands of cycles. This work explores multi-scale effects that have not previously been observed and fills the gap between nano-scale and macro-scale in-situ imaging that exists in the literature. Time-resolved, operando experiments capture the kinetic effects of degradation and reveal their complex, spatially heterogeneous nature. The use of commercial-form- factor cells in this work also provides new insights into how cell geometry, operating conditions, and even gravity can significantly influence the patterns of degradation that form after extended cycling.