Paper published in Science

Last week a paper that I co-authored was published in Science!  Here is a link to the paper, Origin and hysteresis of lithium compositional spatiodynamics within battery primary particles, and here are several press releases related to the research:

Although the major findings in this work were accomplished by experimental collaborators at Stanford and LBNL, the motivation for the experiments came in part from my postdoc work, where we simulated the heterogeneity of lithium in battery nanoparticles and made several controversial predictions. We calculated that the properties of individual nanoparticles should be significantly different from the measured properties of battery electrodes, which are comprised of billions of particles. Thus the challenge was to build a battery out of a single nanoparticle and measure its properties.

It took several years, but this paper conclusively verifies the prediction of a heterogeneous reaction rate in LiFePO4 with a beautiful set of experiments. Our colleagues at Stanford made a rechargeable battery out of a few nanoparticles, and invented a way to image the chemical composition of the particles as they were cycled in a liquid electrolyte (inside a synchrotron). Below is the first ever video of LiFePO4 nanoparticles being charged and discharged.

NiAl-Cr microstructure formation

A paper based on my thesis work was recently accepted to the journal Physical Chemistry Chemical Physics. I helped researchers at the IMDEA Materials Institute in Madrid, Spain apply the phase-field model from my thesis to the NiAl-Cr ternary eutectic superalloy. They connected my model to a database of thermodynamic properties and were able to simulate the growth of the complicated microstructure in this system. Superalloys are a special class of metals that are used to make jet turbine blades because they are very strong and resistant to deformation at high temperatures.

Read Formation mechanism of eutectic microstructures in NiAl-Cr composites

Quantitative phase-field modeling of dendritic electrodeposition

I recently had a Rapid Communication accepted at Physical Review E. This paper represents several years of effort while I was at Samsung to develop a model of the growth of metal dendrites during electrodeposition. In addition to looking pretty, understanding how these dendrites grow is important for making rechargeable batteries with significantly higher energy density than current technologies. The dendrites eventually cause a short-circuit during cycling when a metal electrode is used. In this paper I constructed a phase-field model that accurately captures many of the observed features of electrodeposits. This will be a valuable tool for mitigating dendrite growth, particularly for pulsed charging. The model provides an estimate of the time at which the interface becomes unstable, and could be used to optimize the pulse time while still maintaining a flat interface. The video on the right shows one of the simulations that is presented in the paper. The blue lines are electric field lines, which indicate the direction of migration of ions in the electrolyte (white). The video shows that, after a short period of stable growth, the interface becomes unstable. The electric field concentrates at protruding tips, causing them to grow faster and shield the nearby electrode. When the field at a tip gets too high, the tip splits and the process repeats. Quantitative phase-field modeling of dendritic electrodeposition