Using Simulations to Probe the Physics of Transport and Phase Change in Model Cathode Materials

Abstract

Numerical simulations are an important tool used to improve overall performance in lithium ion batteries. Often numerical methods are utilized for system optimization, however, coupling traditional electrochemical measurements and characterization techniques with numerical simulations allows for insights into the basic science that dictate battery performance. The focus of the presentation is on the analysis of current interrupt experiments and materials characterization, coupled with numerical simulations to gain insights into mass and charge-transport, electron-transfer, and phase change. Understanding how to interpret and apply these insights can directly inform the synthesis of new nanomaterial constructs, resulting in systems with improved performance. Previous research used numerical methods in conjunction with electrochemical measurements and characterization techniques to understand mass-transport and electron-transfer processes in a model cathode material, and included effects across different lengths scales (1-3). These previous studies focused on the processes occurring during lithiation and voltage recovery, and the implications from these studies have been used to inform electrode synthesis and positively impact performance. However, there remained significant challenges to overcome, namely understanding delithiation and phase change. Validating the model with a different chemistry not only demonstrated the broad applicability of model, but also allowed us to study phase change (4). Integrating phase change built upon our understanding of mass-transport and charge-transfer effects. Using the advantages of numerical simulations allowed us to decouple the losses associated with each process and thereby better understand how these governing processes influence battery performance. Extending the model to envelope both lithiation and delithiation is important for the battery field in general because asymmetries are commonly observed between charge and discharge for a variety of battery chemistries. Understanding the physics of mass-transfer, charge-transfer, and phase change as well as charge/discharge asymmetries informs electrode fabrication and battery operation and lends itself to improving the overall performance of these systems. 1. N. W. Brady, K. W. Knehr, C. A. Cama, C. N. Lininger, Z. Lin, A. C. Marschilok, K. J. Takeuchi, E. S. Takeuchi and A. C. West, Journal of Power Sources, 321, 106 (2016). 2. K. W. Knehr, N. W. Brady, C. A. Cama, D. C. Bock, Z. Lin, C. N. Lininger, A. C. Marschilok, K. J. Takeuchi, E. S. Takeuchi and A. C. West, Journal of The Electrochemical Society, 162, A2817 (2015). 3. K. W. Knehr, N. W. Brady, C. N. Lininger, C. A. Cama, D. C. Bock, Z. Lin, A. C. Marschilok, K. J. Takeuchi, E. S. Takeuchi and A. C. West, ECS Transactions, 69, 7 (2015). 4. N. W. Brady, Q. Zhang, K. W. Knehr, P. Liu, A. C. Marschilok, K. Takeuchi, E. S. Takeuchi and A. C. West, Journal of the Electrochemical Society, 163, 2890 (2016). Figure 1