Mesoscale Materials Science Group

A work led by Fan and Kaiqi was just published on ACS Energy Letters. In the paper, we report the observation of non-uniform and filament-like FePO4 domains on LiFePO4 secondary particles that persist during charging and discharging — not good news for battery rate performance and stability. The interesting reaction behavior was shown by phase-field modeling to result from misfit stress between individual primary particles in the LiFePO4 aggregates. It suggests stress reduction is potentially important for improving the reaction uniformity in the secondary particles of LiFePO4 and possibly other electrode materials.

Paper: https://pubs.acs.org/doi/abs/10.1021/acsenergylett.2c00226

News story: https://news.rice.edu/news/2022/lithiums-narrow-paths-limit-batteries

Youtian successfully defending his PhD thesis “Stress Effects on Phase Morphological and Compositional Non-uniformity in Intercalation Compounds”.  Congratulations, Dr. Zhang!  Youtian is heading to west coast soon. We wish him best luck in a new phase of his career and life.

Big congratulations to Kaiqi for successfully defending his PhD thesis “Mesoscale Modeling of Microstructure Evolution in Lithium Battery Electrode Materials” on April 26, 2021.  Job well done, Dr. Yang! And wish you all the best in your next endeavor!

Our group collaborated with Dr. Fei Zhou and other scientists at LLNL in utilizing machine learning to simulate materials microstructure evolution. This work is just published in the open-access journal Patterns from Cell Press:  https://doi.org/10.1016/j.patter.2021.100243

Material microstructure plays a key role in the processing-structure-property relationship of engineering materials. Microstructure evolution is commonly simulated by continuum models based on partial differential equations. We apply convolution recurrent neural networks to learn and predict several microstructure evolution phenomena of different complexities. The method is significantly faster than the traditional approach and capable of predicting the evolution process in systems with unknown material parameters. It provides a useful data-driven alternative to microstructure simulation.

Congratulations to the current and past group members (Kaiqi, Henry, Youtian and Shaoxun) who contributed to this work.

Youtian just published a paper “Stress-Induced Intercalation Instability” in Acta Materialia. In this work, we use linear stability analysis and phase-field simulations to prove a flat intercalation front of lithium or other solutes is made intrinsically unstable by misfit stress in battery compounds. As a result, lithium intercalation will tend to develop wavy fronts at typical battery (dis)charging rates already observed in experiments, a phenomenon that has impact on both rate performance and stress concentration. Nice job, Youtian!

Big congratulations to Fan for successfully defending his PhD thesis “Reaction Heterogeneities in Lithium-Ion Batteries” in September. This is also special to me as Fan is my first PhD student to defend the thesis. Almost concurrent with his defense, Fan also has two first-authored papers appearing in Cell Reports Physical Science and Journal of the Electrochemical Society. It is certainly a very fruitful month!

Henry Cao recently moved to Cambridge and is going to start his PhD study at MIT. Henry, wish you all the best in your next endeavor.

Congratulations to Xiting Yang on successully defending her master thesis!

Youtian is a co-author and led the modeling study in a new paper published on Energy Storage Materials. Congratulations, Youtian!

“Single-Crystal Nickel-Rich Layered-Oxide Battery Cathode Materials: Synthesis, Electrochemistry and Intra-Granular Fracture”, G. Qian, Y. Zhang,  L. Li, R. Zhang, J. Xu, Z. Cheng, S. Xie, H. Wang, Q. Rao, Y. He, Y. Shen, L. Chen, M. Tang, Z. Ma, Energy Storage Materials 27, 140 (2020). 

 

Kaiqi has published a paper on modeling stress-induced non-uniform intercalation behavior in LiFePO4 in Journal of Materials Chemistry A (link). The simulation results exhibit very good agreement with a previous operando scanning transmission X-ray microscopy study and reveals that the coherency stress generated by the misfit strain between the Li-rich and Li-poor phases of the system destabilizes the lithium (de)intercalation front and leads to inferior electrode performance. It also shows that antisite defects promote the interface instability by allowing Li to move more freely along the [100] direction in the diffusion-limited regime. This draws an interesting contrast to our previous finding (published in npj Computational Materials) that antisite defects can benefit intercalation kinetics in the surface-reaction-limited regime. It paints a more complex picture of the defect effect and shows it is dependent on the phase transition mode. Here’s a news story on this work:  https://news.rice.edu/2020/01/14/not-so-fast-some-batteries-can-be-pushed-too-far/