Date of Award

1-1-2010

Document Type

Campus Access Dissertation

Department

Chemical Engineering

First Advisor

Ralph E. White

Abstract

Lithium based batteries have been actively pursued as potential power sources for more than a decade. Many studies have been conducted to improve the performance and stability of the lithium ion and other lithium based battery systems. In spite of commercial success, the technology still faces many critical safety and performance issues that need to be addressed. One of these issues is the mechanical degradation of the battery electrodes.

The main focus of this dissertation is aimed at understanding the effect of mechanical stress and volume change on the performance and life of lithium batteries. In the first part of this dissertation a theoretical analysis of stresses in lithium ion battery is presented. The simulations were performed using lithium cobalt oxide as the cathode material and carbon as the anode material. The stress generation for different particle sizes and shapes is discussed. The simulation results indicate that the shape of the particle plays an important role in determining the mechanical stability of the electrode. A macro-homogeneous model that incorporates effects of stress within the solid phase of the battery electrode is developed. The model attributes stress build-up within intercalation electrodes to two different aspects: changes in the lattice volume due to intercalation and phase transformation during the charge/discharge process. The model is used to predict the influence of cell design parameters including the thickness, the porosity and the particle size of the electrodes on the magnitude of stress generation.

In the second part of this dissertation, a mathematical model to understand the volume expansion in lithium iron disulfide based high temperature battery system is presented. The change in porosity and change in dimension of the electrodes are considered and optimum design parameters are obtained.

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