(Keynote) Modeling Battery Performance Due to Volume Change in Porous Electrodes Towards the Development of Electrified Propulsion Systems
Authors: Weidner John W. , Garrick Taylor R. , Pereira Drew Joseph , Aleman Ashton , Fernandez Miguel , Streng Kathryn , Hou Xu Xian , Gao Xiujie , Higa Kenneth , Dai Yiling , Huang Xinyu , Srinivasan Venkat 
Published: September 2023

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. Several different models exist that can predict the electrochemical performance of these devices under a variety of operating and design conditions. However, in many of these models, the porosity of a porous electrode is often assumed to be 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. Over the past decade and a half, we have shown the ability to incorporate dimensional and porosity changes in a porous electrode during intercalation through the coupling of various mechanics treatments with 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.[1-4] This model was extended to look at design considerations as well as non-uniformity within a single porous electrode coupled to a lithium metal reference.[5] This model was further improved by removing some of the earlier assumptions and is capable of illustrating the development of stress, strain gradients, and porosity gradients across a porous electrode during cycling in a battery containing a blended anode undergoing volume change coupled to an NMC cathode.[6] The reversible volume change predictions were then validated using data from pouch cells seen in the Chevrolet Volt.[7] Following our validation studies, we illustrated the impact that coupled electrochemical-mechanical volume change can have on electric vehicle battery pack design.[8]

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