Browsing by Subject "Lithium ion"

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Development of an advanced electrical system for a solar powered racing vehicle with an emphasis on the battery protection and management system
(2011-05) Engelkemeir, Frederick Donald; Hallock, G. A.; Grady, Mack
This thesis describes the development of an electrical system for a solar powered racing vehicle with en emphasis on the Battery Protection System (BPS). This battery protection system was designed for the UTSVT’s (University of Texas Solar Vehicles Team) solar powered vehicle, the Samsung Solorean. The system is required due to the dangers of the lithium-ion cobalt battery chemistry. The system monitors the voltage, temperature, and current of each battery module in the 22 module battery pack and will physically isolate the pack from the rest of the vehicle with a high-current electromechanical contactor if any parameter is outside of the safe range. The system can be expanded to monitor any number of series battery cells. The system uses a master-slave microcontroller architecture with a single master microcontroller that interrogates several slave microcontroller boards for readings over a common serial bus. The system uses a new voltage sensing ASIC to monitor cell voltages, along with an analog current output device to measure temperature and a hall-effect device to measure current. The system was a complete success and has allowed the UT solar car to finish the American Solar Challenge cross-country “Rayce.”
Polymorphs of lithium transition-metal phosphates : synthesis and characterization
(2015-08) Assat, Gaurav; Manthiram, Arumugam; Yu, Guihua
Lithium transition-metal phosphates, LiMPO₄ (M = Mn, Fe, Co, and Ni) have gained significant research interest over the past two decades as an important class of lithium-ion battery cathode materials. However, almost all of the investigations thus far have focused on the olivine polymorph which exists in orthorhombic Pnma space group. In this report, a distinct orthorhombic but non-olivine polymorph of LiMPO₄, described by a Cmcm space group symmetry, has been synthesized with M = Mn, Fe, Co, and Ni. Of these, LiMPO₄ in the Cmcm space group had never been reported before. A rapid microwave-assisted solvothermal (MW-ST) heating process with tetraethylene glycol (TEG) as the solvent and transition-metal oxalates as precursors facilitate the synthesis of these materials. The peak reaction temperatures and pressures, respectively, were below 300 °C and 30 bar, which is several orders of magnitude lower than the previously reported high pressure (GPa) method. The physiochemical and electrochemical properties of the synthesized materials are characterized with several techniques. X-ray diffraction (XRD) confirms the crystal structure with Cmcm space group and scanning electron micrographs (SEM) indicate a sub-micron thin platelet like morphology. The synthesis process conditions have been optimized to obtain impurity-free samples with correct stoichiometry, as characterized with XRD and inductively coupled plasma - optical emissions spectroscopy (ICP-OES). Upon heat treatment to higher temperatures, the transformation of the Cmcm polymorphs into olivine is observed with XRD and Fourier transform infrared spectroscopy (FTIR). Although the electrochemical activity of these polymorphs as lithium-ion cathodes turns out to be poor, the facile synthesis under mild conditions has enabled easy access to these materials, some of which were not even possible before.
Ultrasonic inspection of lithium-ion batteries to determine battery safety
(2019-12) McGee, Tyler Michael; Haberman, Michael R. (Michael Richard), 1977-; Ezekoye, Ofodike A
Electric vehicles and energy storage systems are becoming increasingly viable from an operational and financial perspective. The most popular choice for the power source for these applications is the lithium-ion battery due to its high volumetric energy density and long cycle life. While lithium-ion batteries have been used in low-power applications for many years, electric vehicles and energy storage systems are high-power applications which put additional operating stresses on the battery cells and the battery management system (BMS) that ensures operational safety. Along with this change in application, lithium-ion batteries are also being subjected to market pressures to increase single-cycle life and to reach full charge faster. BMS have not kept up with these changing applications and market pressures, which has lead to some battery cells failing catastrophically. This thesis explores the viability of ultrasonic inspection to determine battery safety in the event of an overcharge. Two detection criteria were investigated in this thesis: whether an overcharge event could be detected while it was occurring and whether ultrasonic inspection could detect that a battery had previously undergone an overcharge event. The results of these tests showed two consistent indicators of overcharge while it occurred, one around 105% nominal voltage and one around 114% nominal voltage. Both of these indicators signal overcharge well before a catastrophic event. Results also indicated that overcharge can be detected during a normal cycle after the overcharge event occurred