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In Situ Investigations of Solid Electrolyte Interphase Formation and Properties in Lithium Ion Batteries

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Abstract:
The Solid Electrolyte Interphase (SEI) forms in most Li-ion batteries, but properties such as its formation mechanism are a mystery. The goal of this dissertation is to understand SEI properties and growth by looking at the formation of the interface layer on both carbon and silicon anodes. This is done through the use of a simple thin film system to allow easy data interpretation. The thin film configuration allows sample to have high surface area with a controlled morphology, which is perfect for studying this phenomenon. On graphitic anodes in situ stress measurement was done by Multi-beam Optical Stress Sensor (MOSS). The results have shown that there is a linear relationship between current and stress during voltage holds in the initial cycle. This is believed to be caused by the disruption of the graphitic structure near the electrode surface. It was also noted that surface properties affect the slope of this relationship, and by modifying the surface the SEI layer can be altered in thickness. For the second half of this dissertation the SEI stability was examined since it is a particularly important and challenging issue due to the large volume expansion during cycling. Our work employed in situ AFM to investigate SEI formation on amorphous Si. In addition to monitoring volume and surface morphology evolution, the mechanical properties of the SEI were also probed at fixed voltages. These experiments allowed us to investigate SEI behavior with different cycling conditions. It was found that the formation potential had significant effects on the SEI formation. The cycled films were also examined with detailed TEM to characterize the SEI thickness and structure. The results from this full range of experiments were used to develop a detailed model of SEI formation. This model was then employed to develop strategies for designing more stable SEI layers, which is critical for lifetime of Li-ion batteries
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Thesis (Ph.D. -- Brown University (2015)

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Citation

Tokranov, Anton V., "In Situ Investigations of Solid Electrolyte Interphase Formation and Properties in Lithium Ion Batteries" (2015). Materials Science Engineering Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0XD102V

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