In order to accurately predict the behavior of electrochemical devices, it is necessary to develop sophisticated models that take into consideration transport processes, electrochemical phenomena, mechanical stresses, and structural deformations on the operation of an electrochemical system. Many different models exist that can predict the electrochemical performance of these devices under a variety of operating and design conditions. In many of these models, the porosity of a porous electrode is often assumed constant since the volume changes seen during the intercalation reaction can be small. However, electrode materials developed in recent years show significant volume changes during intercalation, which are unable to be accurately predicted using these constant porosity models.

Porosity and dimensional changes in an electrode can significantly affect the resistance of the battery during cycling and can cause premature failure of the battery due to generated stresses. Previously^[1-5], we have shown the ability to incorporate dimensional and porosity changes in a porous electrode into a model to predict volume changes in the active material of a single electrode during intercalation through the coupling of porous rock mechanics and porous electrode theory. Many assumptions were used to obtain an analytical solution, including the assumption of bulk strain, uniform porosity, and uniform concentration across the electrode.^[2] This model was extended to look at design considerations^[5] as well as non-uniformity within a single porous electrode coupled to a lithium metal reference.^[4] Here, we present a model that removes some of these assumptions and illustrates the coupling of porous electrode theory and rock mechanics in order to predict stress, strain gradients, and porosity gradients across a porous electrode during cycling in a battery containing a blended anode undergoing volume change coupled to a Lithium Nickel Manganese Cobalt Oxide (NMC) cathode.^[6] In this model, we will examine separator deformation, volume change during high charge rates, and consider pressure generated in the cell due to restriction in a battery module.

1. P. M. Gomadam and J. W. Weidner, J Electrochem Soc, 153, A179 (2006).
2. T. R. Garrick, K. Kanneganti, X. Y. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014).
3. T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, Ecs Transactions, 72, 11 (2016).
4. T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017).
5. T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017).
6. K. Higa, S. Wu, D. Y. Parkinson, Y. Fu, S. Ferreira, V. Battaglia and V. Srinivasan, J Electrochem Soc, 164, E3473 (2017).