As we shift away from fossil fuel-derived energy and the electrification of various systems grows exponentially, society is increasingly relying on energy storage systems such as batteries to store and distribute energy on demand. While batteries are a widely studied technology, other energy storage technologies such as supercapacitors have unique performance qualities that can provide alternatives or supplements to batteries in systems. This dissertation delves into MnO2 pseudocapacitors, aiming to unravel the degradation mechanisms impacting their performance and reliability under diverse operating conditions, toward their usage (or other pseudocapacitive materials) in real systems. While there is a growing body of research on pseudocapacitors, including MnO2-based pseudocapacitors, little work has gone into frameworks for predicting their behavior under various environmental and operating conditions. Through a multifaceted approach of experimental investigation, physics-based modeling, and probabilistic analyses, this research centers on elucidating the impact of temperature and degradation of active material on the aging of devices, ultimately predicting capacitance reduction over time.
Two approaches are taken in this research to predict end of life for pseudocapacitors. The first approach utilizes a first-principles physics model, augmented with Bayesian methods to integrate experimental and statistical information with uncertainties into the model. This method allows for the prediction of changes happening in the cell over numerous cycles, and the associated capacitance reductions. The second approach develops for the first time the use of a Bayesian Monte Carlo approach for estimating the remaining useful life (RUL) of pseudocapacitors based on experimental data with quantified uncertainty. The combination of estimates from these models can lead to improved prediction based both on real world experience through data and on theoretical knowledge of the system.
Overall, this dissertation advances the prediction of aging in MnO2 pseudocapacitors and develops models that can be applied to various other pseudocapacitive systems. These contributions lay a foundation for further exploration that may decrease the time required to conduct pseudocapacitor experiments and contribute to the management and longevity of energy storage systems containing pseudocapacitors.
