Coupled Stress-Based Degradation Modeling of Composite-Anode Lithium-Ion Batteries

Abstract

The quest towards more sustainable technologies of the future is heavily predicated on the advancements of battery-based energy infrastructure. Given the need to increase the performance envelope of the current-generation batteries, substantial research and production efforts have been placed in utilization of higher performing battery materials, one method being the development of composite anode batteries. Some of the problems with composite anodes are complex mechanical stress interactions between materials of different phases, as well as low identifiability of degradation between different active materials. This two-part paper develops a stress formulation that accounts for stresses experienced between different active materials present in the composite electrode via Mori-Tanaka mean field stress formulations, allowing for a unified stress-based degradation model that combines intra-particle and interphase stress contributions to the electrode natively. While Mori-Tanaka provides a useful step-up in modeling of the interphase stresses, opportunities remain in developing models that retain better predictive power beyond linear elastic regimes. Additionally, this thesis explores methods of increasing robustness of noninvasive degradation tracking for composite electrode batteries via Sobol-sensitivity informed optimization methods, which serve to identify voltage regions where given active materials contribute the most to the voltage response of the cell, allowing for more physically informed parameter estimation. Plausible extension of the work could employ fitting data beyond constant-current discharge voltage-time traces as used in the study, and monitor unique electrochemical signatures such as hysteresis in order to enhance degradation tracking.