Materials characterization and aging studies of lithium ion battery systems

Lithium being a lightest metal provides highest voltage and energy density hence paved way to the development of lithium ion batteries. There is a continuous attempt to improve the performance of the lithium ion batteries by the substitution of new cathodes and anodes. Chromium oxide cathodes show relatively high specific capacity and energy density over other materials. It has wide range of operating voltage and show less capacity fade with cycling.; The first part of the dissertation focuses on the development of novel chromium oxide cathode materials with high specific capacity. The synthesis conditions were optimized so as to reduce the amount of electrochemically inactive oxides and to reduce the irreversible capacity loss. The rate capability of these materials can be improved by doping with cobalt however only by sacrificing the conductivity and initial capacity. Conducting polymers have been found to be both electrochemically active and electrically conducting. A polypyrrole encapsulation over cobalt chromium oxide was found to increase the conductivity drastically. Polypyrrole being electrochemically active for lithium intercalation also improved the rate capability and specific capacity to a small extent.; Lithium silver vanadium oxide (Li-SVO) batteries are being used as power sources in implantable medical devices. The Li-SVO battery has poor rate capability during its mid life which makes them potentially dangerous to be employed inside the patient's heart. Attempts have been made to analyze the discharge performance of silver vanadium oxide cathode. The problems associated are also identified.; The last part of the dissertation focuses on the aging of lithium ion batteries. Long storage life is necessary for the lithium ion batteries to be used for long duration space missions. The calendar life performance of the lithium ion batteries were studied experimentally under various operating conditions like temperature, end of charge voltage and type of storage. High temperature and higher end of charge voltages were found to be detrimental to the lithium ion cell performance. Finally a simple mathematical model was developed to simulate the self discharge phenomena of carbon anode inside a lithium ion cell. The model is able to predict the capacity loss, open circuit potential change and film resistance increase of a carbon anode under open circuit storage.