ELECTROCHEMICAL AND THERMAL BEHAVIOR OF ENERGY STORAGE AND CONVERSION SYSTEMS: LITHIUM ION BATTERIES AND PEM FUEL CELLS

In this dissertation, three major topics in electrochemical energy storage and conversion systems are discussed. Lithium-ion batteries as electrochemical energy storage and catalyst support in proton exchange membrane (PEM) fuel cells as an electrochemical energy conversion system has been investigated. Most work was done to understand the mechanism of an electrochemical reaction and performance degradation in both systems. After that, it was essential to overcome the technical challenges. The thermal stability of lithium-ion cells has been characterized by a novel cathode and anode material with an electrolyte. For electrochemical energy storage, LiFePO4 as a cathode material in a lithium-ion battery has been investigated by various electrochemical techniques. Generally, the electrode consists of an active material, polymer binder, and conducting agents. The electrode material compositions can affect the electrochemical performance by changing the ratio of carbon content to binder or active material content. The LiFePO4 electrodes were optimized by several factors; electronic conductivity, over voltage during discharge, area specific impedance, hybrid pulse power, and energy density. Silicon is a promising material as a novel anode material in lithium-ion batteries. The importance of selecting a polymer binder among various binders has been addressed by the experiments. The additive in the electrolyte also affects the interfacial property between the solid active material and the electrolyte. The effect of fluoroethylene carbonate (FEC) additive was investigated by electrochemical and physical characterization. The thermal stability of the silicon anode was studied by varying the FEC concentration. Metal oxide, as a non-carbon catalyst support in the PEM fuel cell, was chosen and developed to replace the carbon support for better electrochemical durability. The electronic conductivity; Brunauer, Emmett and Teller (BET) surface area; stability in acid media; and the electrochemical stability of fabricated Zr-doped In2O3 were evaluated.Ph.D. in Chemical Engineering, May 201