The Effects of Non-Ideal, Lithiation-Based Active Material Volume Change on Mechano-Electrochemical Pouch Cell Simulation

Abstract

Automotive battery manufacturers are working to improve individual cell and overall pack design by increasing their performance, durability, and range, while reducing cost; and active material volume change is one of the more complex aspects that needs to be considered during this process. In the study presented here, thermodynamically non-ideal (non-linear), lithiation-based volume change behavior for the anode and cathode active materials were incorporated into a previously developed mechano-electrochemical model.(1-4) Before, an ideal (linear) relationship between active material volume change and state-of-lithiation was assumed. Using the non-ideal active material volume change behavior, the changing thickness of an automotive relevant, large-format pouch cell was predicted while simulating cell discharge. Measurements were taken using an experimental setup capable of simultaneous mechanical and electrochemical operation and observation. Figure 1 shows that the mechano-electrochemical measurements prove to agree well with simulation when using non-ideal lithiation-based volume change as opposed to the previously assumed ideal volume change behavior. The resulting model was used to simulate other mechano-electrochemical phenomena including the effects of anode/cathode capacity ratio and changing pressure/porosity during cell discharge. This mechano-electrochemical model shows promise to help define operational parameters to mitigate negative effects from active material volume change and may act as a tool for developers to reduce the extensive electrochemical and mechanical testing required for the design of promising new batteries. References T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, Journal of The Electrochemical Society, 164, E3592 (2017). T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, Journal of The Electrochemical Society, 164, E3552 (2017). T. R. Garrick, K. Kanneganti, X. Huang and J. W. Weidner, Journal of The Electrochemical Society, 161, E3297 (2014). D. J. Pereira, J. W. Weidner and T. R. Garrick, Journal of The Electrochemical Society, 166, A1251 (2019). D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner, and T. R. Garrick, Journal of The Electrochemical Society, 167, 080515 (2020). Figure 1. Experimentally measured data and simulations using ideal and non-ideal active material volume change behavior for a NMC/LMO:Graphite pouch cell strain as a function of cell state-of-charge. Figure 1