题目：Studies on the failure problems in core/shell structured energy materials: from observation through understanding to optimization
报告人：Dr. Haimin Yao Department of Mechanical Engineering, Hong Kong Polytechnic University
Anode materials for lithium ion batteries (LIBs) with large specific capacity such as silicon (Si) and tin dioxide (SnO2) tend to have large volume expansion during lithiation, resulting in a series of failure problems such as pulverization of the anode materials and fracture of solid-electrolyte interphase (SEI) layer. To mitigate these adverse effects, recently core/shell structured materials were developed and applied as anode materials for LIBs. In this talk, based on the in-situ TEM observations, we find that if the core/shell structures have not been designed well, failure problems, instead of being prohibited, would be stimulated and even aggravated. Fracture mechanics is applied to understand the mechanism of two coating-related failure phenomena observed in two core/shell structured anode materials. One is the thickness-dependent fracture of the amorphous carbon coating of SnO2 nanowires while the other is the fracture of silicon nanoparticles evoked by its carbon coating. Our results not only provide insight into the effects of coating on active materials but will be of great value to the design and optimization of the core/shell structured anode materials for high performance LIBs
Dr. Haimin Yao is currently an Assistant Professor in the Department of Mechanical Engineering at theHong KongPolytechnicUniversity. He received his BEng and MEng degrees in Solid Mechanics fromTsinghuaUniversityin 2000 and 2002 respectively. He subsequently went toGermanyand studied in the Max-Planck Institute for Metals Research. In 2006, he obtained his Doctor degree in Chemistry from Universität Stuttgart. Then he moved toUSAand worked as a postdoctoral Research Associate atBrownUniversityand subsequently at Massachusetts Institute of Technology. In 2011, he joined the Department of Mechanical Engineering of theHong KongPolytechnicUniversity. The research interests of Dr. Yao include bio-inspired mechanics and materials, and mechanical behaviors of energy storage materials. He has published more than 40 papers on the top multi-disciplinary journals such as PNAS, Scientific Reports, Journal of Royal Society Interface, CARBON and the top journals in solid mechanics such as JMPS, IJSS and JAM. So far, his works have been cited for more than 1,200 times.