Spontaneously formed passivation layers, as thin as nanometers, can kinetically hinder reactions and enable many important applications, such as stainless steel, aluminum boil kettle, and titanium ship in seawater. The more active lithium metal surface is also covered by a passivation layer (called solid electrolyte interphase, SEI) due to electrolyte reduction in a battery cell. Their formation, growth, diffusion, deformation intertwined with the underlining metal and the outside environment pose great challenges to solving chemical-mechanical and electrochemical-mechanical coupled problems. Several important examples and approaches will be discussed in this talk.
Molecular dynamics with the reactive force field (ReaxFF) can simultaneously track the chemical, structural, and mechanical evolution of nanostructures during oxidation, lithiation, delithiation etc. As an example, we show how dynamic oxidation alters the tensile deformation of aluminum nanowires. Surprisingly, the oxidation enhances the aluminum nanowire ductility, and the oxide shell exhibits superplastic behavior assisted by reaction and diffusion. The interplay between the strain rate and oxidation rate is captured by a simple analytical model, which can be extended to macro-scale.
To capture the electrochemical reactions at a passivated interface, a new half-cell model is created and Density Functional Theory and tight binding were used to compute the energy landscape for the fundamental charge transfer reaction Li++e-↔Li0 at a complex Li/Li2CO3/liquid-EC-electrolyte interface. For the first time, it is clearly demonstrated that the charge transfer occurs underneath the perfect SEI. The desolvation energy barrier, the double layer structure, and the Li+ transport through the SEI under the applied electric potential were predicted. These predicted energetics is used to inform phase field models in order to capture the Li-dendrite growth process at meso-scale.
Dr. Yue Qi is a Professor in the Chemical Engineering and Materials Science Department and the Associate Dean for Inclusion and Diversity in the College of Engineering and at Michigan State University. Dr. Qi received her B.S. in Materials Science and Engineering and Computer Science from Tsinghua University and her Ph.D. in Materials Science with a minor in Computer Science from Caltech. She spent the next 12 years working at the General Motors R&D Center. At GM, she developed multi-scale models starting from atomistic level to solve engineering problems related to lightweight alloys, fuel cells, and batteries. She transitioned from industry to academia in 2013 and built the “Materials Simulation for Clean Energy” Lab at MSU. She was a co-recipient of 1999 Feynman Prize in Nanotechnology for Theoretical Work for her Ph.D. work; received three GM Campbell awards for fundamental research on various topics while working in GM; and won the 2017 Minerals, Metals & Materials Society (TMS) Brimacombe Medalist Award.
Hosted by: Prof. Peng Bai