Date of Award

Spring 1-1-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Se-Hee Lee

Second Advisor

Conrad R. Stoldt

Third Advisor

Martin Dunn

Abstract

Lithium-ion battery technologies have always been accompanied by severe safety issues; therefore recent research efforts have focused on improving battery safety. In large part, the hazardous nature of lithium-ion batteries stems from the high flammability of liquid electrolytes. Consequently, numerous researchers have attempted to replace liquid electrolytes with nonflammable solid electrolytes in order to avoid potential safety problems. Unfortunately, current solid electrolytes are incapable of performing as effectively as liquid electrolytes in lithium-ion batteries due to inferior electrochemical capabilities. While some "all-solid-state" batteries have found niche application, further technological advancement is required for large scale replacement of liquid-based batteries. The goal of this research is to develop all-solid-state batteries that can outperform liquid batteries and understand the mechanisms that dictate battery operation and behavior. This involves fabrication of highly conducting solid electrolytes, production and analyzation of batteries employing state-of-the-art electrode materials, and generation of high power and high energy density lithium batteries. In this dissertation, the first objective was to manufacture highly conducting solid electrolytes that are stable in contact with lithium metal. Numerous characterization techniques were used to gain understanding of physical and chemical properties of solid electrolytes, as well as mechanisms for fast ion conduction. A new process for production of highly conducting and stable solid electrolytes is developed and materials are used to evaluate performance of electrodes in an all-solid-state construction. The second objective of this work was to research the performance of both positive and negative electrodes incorporating solid electrolyte. Evaluation of electrochemical results allowed for a good understanding of reaction mechanisms taking place within composite battery materials and at electrolyte/electrode interfaces. Variation of solid electrolyte make-up and composite electrode architecture reveals numerous advantages of solid state batteries over liquid batteries. The third and final objective of this work was to demonstrate high energy/power density all-solid-state rechargeable batteries. Electrode materials with fast lithium diffusion and kinetic properties were investigated. Alteration of particle size and testing temperature exposed the capability of solid state batteries to achieved high performance, comparable to that of liquid electrolyte batteries.

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