Date of Award
Doctor of Philosophy in Chemistry
Brett L. Lucht
Stronger emphasis on sustainability has become a necessity amongst all industries, and the automotive industry is no exception. The push to move toward hybrid electric vehicles (HEVs) and electric vehicles (EVs) has resulted in a need for lithium ion batteries delivering higher power over a wide temperature range with improved safety over a long lifetime. To accomplish these requirements, advanced electrode materials such as the high nickel cathode material LiNi0.8Co0.1Mn0.1O2 (NCM811) or the anode material Li4Ti5O12 (LTO) have been sought after. The high nickel cathode materials come with the desired high capacity suitable for the power needed for automobile applications but comes with safety and cycle life troubles. Looking at the other electrode LTO comes with long cycle life and improved safety compared to the widely used graphite anode but has gassing and capacity setbacks. The purpose of this work has two focuses, anode and cathode, with the common goal of using electrolyte optimization to resolve these advanced material problems. Electrochemical performance testing, gas chromatography, and electrolyte formulation investigation has been conducted to understand the mechanism of gas production with the LTO anode material. Results from this showed the gas evolution is directly related to the electrolyte interacting with the surface of the LTO. By creating a passivation film to protect the surface of the electrode from the electrolyte reactions through additive optimization and electrolyte formulation, we reduced the amount of gas produced by the material. Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and ATIR-IR spectroscopy were used to characterize the surface film. Using the same concept of electrolyte optimization, additives such as tris(trimethylsilyl)phosphate (TMSP) and Ethoxy pentafluoro cyclotriphosphazene (PFPN) were shown to provide performance benefits to NCM811 cathode material through electrochemical measurements and EIS. Through the experiments conducted and results gathered, this work shows the ability to make the advanced materials, such as NCM811 and LTO, viable materials for successful commercialization in lithium ion batteries.
Hoffmann, Jennifer, "Investigation of Failure and Gassing in Advanced Lithium Ion Battery Systems with Electrolyte Optimization as a Solution" (2018). Open Access Dissertations. Paper 708.