Date of Award

August 2021

Degree Type

Thesis

Degree Name

Master of Science

Department

Engineering

First Advisor

Benjamin C Church

Committee Members

Nidal Abu-Zahra, Ilya Avdeev

Abstract

The importance of a safe and reliable way to both store and use energy, has led to a significant amount of research in the field of secondary battery development and refinement. The thesis herein explores a new application of a mature technology that has proven viable for internal combustion engines (ICE). Though the technology has proven viable for the start, lighting, and ignition, of conventional ICEs, the development of such advanced battery systems to meet the energy demands of Hybrid Electric Vehicles (HEV) is not without challenge. Lead acid SLI secondary batteries have demonstrated high recyclability, low self-discharge, good performance at both low and high temperatures, while also being cost effective. However, several of the main drawbacks to this technology include battery weight, limited cycle life, loss of capacity from sulfation, corrosion of the electrodes, and degradation of active material, among others, which precludes their widespread adoption over more expensive battery chemistries. The high currents involved with regenerative braking technologies, as well as operation under high rate partial state of charge (HRPSoC) conditions as a function of start-stop technologies, and the resultant cell degradation, has led to much research in the direction of performance advancements while maintaining the positive benefits and cost effectiveness. The complexity of the HRPSoC conditions induced during HEV operation has made development of mitigations strategies for observed cell degradation mechanisms both difficult and expensive. In particular, the sulfation that occurs at the negative plates is of high concern. Through the combination of cyclic voltammetry (CV) and scanning electron microscopy (SEM), a fundamental understanding of the lead sulfate growth kinetics could be studied more easily. In this work, several paste compositions for the negatively active material (NAM) were prepared to study the individual additive’s effects on lead sulfate growth kinetics at the negative plate. Additionally, by modifying the number of cycles endured and coarsening duration, the resultant impacts of those variables on the lead sulfate growth kinetics were investigated. From the results, the greatest reduction in lead sulfate crystallization and growth, with corresponding NAM additives were predicted, with the samples containing carbon additives having the greatest impacts relative to the lead only control sample. Experimental challenges were observed, such as corrosion of the current collectors, delamination of the working electrodes, and non-homogenous distribution of additives present, which may have contributed deviations from theoretical expectations. It is anticipated that the developed three-electrode test cell developed in conjunction with the aforementioned analytical techniques, can be readily applied to rapidly evaluate the efficacy of NAM additives in the retardation of lead sulfate crystallization and growth kinetics.

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