ABSTRACT
The durability of lithium-ion batteries is controlled by many coupled chemical and mechanical degradation mechanisms. Although empirical models have been trying to include more degradation mechanisms in order to predict battery life, they generally lack of proper input materials’ properties and direct experimental supports. To address this issue, we investigated both mechanical and chemical degradation via combined and interconnected first principles calculations, continuum modeling and experiments. Toward the understanding of mechanical degradation, we predicted that graphite anode modulus is tripled during Li insertion from first principles calculations. It is important to include this effect in diffusion induced stress modeling when compared with in-situ measurements of microstructural strain in a commercial graphite anode. Toward the understanding of chemical degradation, we focused on Li+ transport through the solid electrolyte interphase (SEI). Based on the insights from experiments and first principle calculations, meso-scale diffusion equations were then formulated upon a new two-layer/two-mechanism model: pore diffusion in the porous organic layer and knock-off diffusion in the dense inorganic layer of SEI. This diffusion model not only predicted the unusual isotope ratio profile measured by Time-of-flight secondary ion mass spectrometer, but also suggested that Li transport in SEI is voltage dependent. Overall, our results underscore the importance of integrating state of charge (SOC) dependent material properties into Li-ion battery performance and failure modeling.

报告人简介:
Dr. Yue Qi (齐月) is an associate professor in the Chemical Engineering and Materials Science Department at Michigan State University, East Lansing, MI. She received her dual-B.S. degrees in Materials Science and Engineering and Computer Sciences from Tsinghua University in 1996 and her PhD in Materials Science from California Institute of Technology in 2001. She was a co-recipient of 1999 Feynman Prize in Nanotechnology for Theoretical Work during her PhD study. After her PhD, she spent 12 years working at Chemical Sciences and Materials Systems Lab, General Motors R&D Center, Warren, MI. At GM, she led a multi-scale modeling research effort to solve problems related to forming and machining of light weight alloys, and developing energy materials for batteries and fuel cells. She won three GM Campbell awards for outstanding research on various topics and TMS Young Leader Professional Development Award. Her recent research interest is integrating material failure model with battery life prediction. She has published more than 70 peer-reviewed journal papers and gave many invited presentations in the international conferences, including the first Batteries Gordon Conference.