Investigation of novel electrolyte additives in lithium ion batteries at elevated temperature

Lithium-ion batteries (LIBs) are currently one of the leading energy storage systems behind our everyday portable devices, electric vehicles, and power grids. Due to global energy crisis and rising demands for alternative energy resources, state funded renewable energy programs and tax incentives have propelled a groundbreaking era of rapid research and development in LIBs. While we are witnessing the global shift away from conventional fossil fuels, a few major obstacles have undermined the scalability and reliability of lithium-ion batteries technology, including limited energy density, operational temperature, calendar life and safety concerns. Among numerous attempts to circumvent the issues discussed above, developing novel electrolyte additives is one indisputably cost-effective approach in lithium-ion batteries industry. In this dissertation, we primarily focus on understanding and developing electrolyte additives to improve graphite/lithium-nickel-cobalt-manganese-oxide (NCM) cyclability and gas evolution at elevated temperature. Surface characterization techniques, such as X-ray photoelectron spectroscopy (XPS) and Fourier transform inferred spectroscopy (FTIR), are used to characterize surface chemistry of the electrodes harvested from cycled LIBs coin cells. Electrochemical impedance spectroscopy (EIS) is employed to determine the electrochemical reactivity of such additives. Further, a developed additive screening method using gas chromatography mass spectrometry (GC-MS) is implemented to study electrolyte transesterification products and monitor the changes in gas generation while incorporating novel electrolyte additives