John W. Weidner

Increasing demand for hydrogen are driving the need for the development of more efficient methods to produce hydrogen on a large scale. The main methods for hydrogen production include reforming of hydrocarbons such as natural gas, coal gasification, biological processes, water electrolysis, and thermo-chemical cycles. The processes involving hydrocarbons contribute to CO ₂ emissions, and biological processes may not be cost effective on a large scale. Electrolysis is commercially viable but may be too inefficient for large-scale applications. Hence the interest in using thermochemical cycles for large-scale hydrogen production. Thermochemical cycles produce hydrogen through a series of chemical reactions that result in the splitting of water at much lower temperatures (~500-1000ºC) than direct thermal dissociation (>2500 ^o C). All other chemical species in these reactions are recycled resulting in the consumption of only heat and water to produce hydrogen and oxygen. Since water rather than hydrocarbons are used as the source of hydrogen in these thermochemical cycles, no carbon dioxide emissions are produced and the hydrogen is highly pure. Although there are hundreds of possible thermochemical cycles, the hybrid-sulfur (HyS) process is the only practical, all-fluid, two-step thermochemical cycle. If the energy input into the process is solar energy, solar radiation is used in a solar receiver/reactor to provide the energy needed to vaporize and decompose sulfuric acid. The resulting sulfur dioxide (SO ₂ ) is used in the second step consisting of an SO ₂ -depolarized electrolyzer (SDE) that electrochemically oxidizes SO ₂ with water to form sulfuric acid at the anode and hydrogen at the cathode. All sulfur species are recycled, and the overall reaction is the splitting of water to form hydrogen and oxygen. Excess SO ₂ is stored during daylight operation and used at night to permit continuous electrolyzer operation and hydrogen production. Electricity is supplied from a companion solar-electric plant or obtained from the grid. Approximately 80% of the energy input to the process is solar-thermal energy, and 20% is electricity for the electrolyzer and auxiliaries. We have developed and patented a gas-fed SDE that we tested over a range of operating conditions (e.g., current, temperature, SO ₂ flow rate) and design variations (e.g., catalyst type and loading, membrane type and thickness). Results of our research will be presented and the challenges that remain in making this an economically viable process for large-scale hydrogen production will be presented.

The electric vehicle (EV) revolution has prompted automotive manufacturers to develop new battery cell and pack technology at an extremely rapid pace--dictating the need to employ modeling methods to become resilient to material delays and remove strain from experimental capability. Automotive manufacturers are concerned with how material, electrode, cell, and pack design decisions impact each other, some of which are hard to measure until after development. Therefore, multi-scale models are of particular interest to help improve the EV and battery pack development process. One phenomenon that can greatly impact design decisions is the volume change of active material upon lithiation, especially considering the promising materials with high volume change, like silicon. The active material volume change can lead to changes in the electrode's porosity and volume, impacting performance. The volume change of the electrode can lead to swelling of the full pouch cell (or pressure generated in a prismatic cell). And finally, the cell volume and pressure change can impact design decisions at the full module or pack scales. To address this, the authors have launched an industrially-led project focused on the development of a multi-scale, mechano-electrochemical battery model, with particular focus on automotive applications. Initially, theoretical models were developed to capture how volume change may impact performance in a single electrode^[1] and dual insertion electrodes.^[2] Then, applied models were developed to account for volume change impacts on the cell and pack scales^[3], incorporate realistic, thermodynamically non-ideal active material volume change^[4], and accurately simulate electrodes with blended active materials to account for preferential lithiation and unique volume change behavior.^[5] In this presentation, the development of these models will be briefly summarized. Throughout the presentation, the discussion will have a particular emphasis on how each modeling topic may be useful to automotive manufacturers. Additionally, brief discussion will be provided on concepts that would improve the usefulness of this type of model, such as accounting for the impact of battery aging.^[6,7] The authors thank the GM Global Propulsion System's team for computing resources and partial funding. This work was partially funded by the IGERT Program at University of South Carolina under NSF Award #1250052. References 1. Garrick, Taylor R., et al. "Modeling volume change due to intercalation into porous electrodes." Journal of The Electrochemical Society 161.8 (2014): E3297. 2. Garrick, Taylor R., et al. "Modeling volume change in dual insertion electrodes." Journal of The Electrochemical Society 164.11 (2017): E3552. 3. Pereira, Drew J., et al. "The effect of volume change on the accessible capacities of porous silicon-graphite composite anodes." Journal of The Electrochemical Society 166.6 (2019): A1251. 4. Pereira, Drew J., et al. "Accounting for non-ideal, lithiation-based active material volume change in mechano-electrochemical pouch cell simulation." Journal of The Electrochemical Society 167.8 (2020): 080515. 5. Pereira, Drew J., et al. "A Mechano-Electrochemical battery model that accounts for preferential lithiation inside blended silicon graphite (Si/C) anodes." Journal of The Electrochemical Society 169.2 (2022): 020577. 6. Pannala, Sravan, et al. "Consistently Tuned Battery Lifetime Predictive Model of Capacity Loss, Resistance Increase, and Irreversible Thickness Growth." Journal of The Electrochemical Society 171.1 (2024): 010532. 7. Fink, Kae, et al. "Application of electron backscatter diffraction techniques to quantify effects of aging on sub-grain and spatial heterogeneity in NMC cathodes." Energy Storage Materials 44 (2022): 342-352.

Automotive manufacturers are working to improve cell and pack design by increasing their performance, durability, and range. One of the critical factors to consider as the industry moves towards materials with higher energy density is the ability to consider the irreversible volume change characteristic of the accelerated SEI layer growth tied to the large volume change and particle cracking typically associated with active material strain. Here, we add to a previously developed mechano-electrochemical model[1-8] to more practically understand the impact of irreversible volume change, primarily assigned to SEI layer growth. As the time from initial design to manufacture of electric vehicle is decreased in order to rapidly respond to consumer demands and widespread adoption of electric vehicles, the ability to link aging and volume change to end of life vehicle requirements using virtual tools is critical.[9] In this study[10], we apply a model to determine the irreversible volume change at the electrode and cell level, allowing for virtual design iterations to predict the volume change at battery cell aged states, and probe possible changes in the SEI layer over life. References: T. R. Garrick, K. Kanneganti, X. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014). T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, ECS Transactions, 72, 11 (2016). T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017). T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017). D. J. Pereira, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 166, A1251 (2019). D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 167, 080515 (2020). D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022). T. R. Garrick, M. A. Fernandez, M. Verbrugge, C. Labaza, R. Mollah, B. J. Koch, M. Jones, J. Gao, X. Gao and N. Irish, J. Electrochem. Soc., 170060548 (2023) T. R. Garrick, Y. Zeng, J. B. Siegel, and V. R. Subramanian, J. Electrochem. Soc., 170113502 (2023) T. R. Garrick, Y. Miao, E. Macciomei, M. Fernandez and J. W. Weidner, J Electrochem Soc, 170, 100513 (2023).

Automotive manufacturers are working to improve cell and pack design by increasing their performance, durability, and range. One of the critical factors to consider as the industry moves towards materials with higher energy density is the ability to consider the irreversible volume change characteristic of the accelerated SEI layer growth tied to the large volume change and particle cracking typically associated with active material strain. Here, we add to a previously developed mechano-electrochemical model[1-8] to more practically understand the impact of irreversible volume change, primarily assigned to SEI layer growth. As the time from initial design to manufacture of electric vehicle is decreased in order to rapidly respond to consumer demands and widespread adoption of electric vehicles, the ability to link aging and volume change to end of life vehicle requirements using virtual tools is critical.[9] In this study[10], we apply a model to determine the irreversible volume change at the electrode and cell level, allowing for virtual design iterations to predict the volume change at battery cell aged states, and probe possible changes in the SEI layer over life. References 1. T. R. Garrick, K. Kanneganti, X. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014). 2. T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, ECS Transactions, 72, 11 (2016). 3. T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017). 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. D. J. Pereira, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 166, A1251 (2019). 6. D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 167, 080515 (2020). 7. D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022). 8. T. R. Garrick, M. A. Fernandez, M. Verbrugge, C. Labaza, R. Mollah, B. J. Koch, M. Jones, J. Gao, X. Gao and N. Irish, J. Electrochem. Soc., 170 060548 (2023) 9. T. R. Garrick, Y. Zeng, J. B. Siegel, and V. R. Subramanian, J. Electrochem. Soc., 170 113502 (2023) 10. T. R. Garrick, Y. Miao, E. Macciomei, M. Fernandez and J. W. Weidner, J Electrochem Soc, 170, 100513 (2023).

Automotive manufacturers are working to improve cell and pack design by increasing their performance, durability, and range. One of the critical factors to consider as the industry moves towards materials with higher energy density is the ability to consider the irreversible volume change characteristic of the accelerated SEI layer growth tied to the large volume change and particle cracking typically associated with active material strain. As the time from initial design to manufacture of electric vehicle is decreased in order to rapidly respond to consumer demands and widespread adoption of electric vehicles, the ability to link aging and volume change to end of life vehicle requirements using virtual tools is critical. In this study, apply a mechano-electrochemical model to determine the irreversible volume change at the electrode and cell level, allowing for virtual design iterations to predict the volume change at battery cell aged states.

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] References P. M. Gomadam and J. W. Weidner, J Electrochem Soc, 153, A179 (2006). T. R. Garrick, K. Kanneganti, X. Y. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014). T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, Ecs Transactions, 72, 11 (2016). T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017). T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017). D. J. Pereira, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 166, A1251 (2019). D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 167, 080515 (2020). D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022).

Automotive battery manufacturers are improving individual cell and overall battery pack design by focusing on increasing performance, durability, and range while reducing cost. However, the coupled mechano-electrochemical phenomena caused by lithiation-based active material volume change significantly complicates the adoption and design of advanced battery systems, especially those with a high degree of volume change. Battery pack engineers mitigate the effects of volume change using a variety of methods, though, these mitigation strategies rely on extensive testing with anytime a change in chemistry or pack design is made. Therefore, it is critical to understand the link between active material volume change and the effect on multiple scales. In this work, we add to a previously developed mechano-electrochemical model to more practically understand the impact of irreversible active material volume change, primarily assigned to SEI layer growth. Initially, a representative volume element model was incorporated into the model geometry to more realistically understand how cell components mechanically interact with each other. This allows for a better understanding of how individual components, including foam added to mitigate volume change, and the overall cell reacts to the active material volume change at the anode electrode during lithiation to generate realistic predictions of pressure and porosity changes. Second, the volume change tied to structural changes for graphite was tied to cell level volume change. Then, a mechano-electrochemical measurement apparatus was developed and used to verify simulation results. This work improves on past efforts and considers the impact of aging on volume change at the particle level, and extends the growth as an irreversible source term to impact the overall cell expansion. References Pereira, D. J., Aleman, A. M., Weidner, J. W., & Garrick, T. R. (2022). “A Mechano-Electrochemical Battery Model that Accounts for Preferential Lithiation Inside Blended Silicon Graphite (Si/C) Anodes.” Journal of The Electrochemical Society, 169(2), 020577. Pereira, D. J., Fernandez, M. A., Streng, K. C., Hou, X. X., Gao, X., Weidner, J. W., & Garrick, T. R. (2020). “Accounting for Non-Ideal, Lithiation-Based Active Material Volume Change in Mechano-Electrochemical Pouch Cell Simulation.” Journal of The Electrochemical Society, 167(8), 080515. Pereira, D. J., Weidner, J. W., & Garrick, T. R. (2019). “The effect of volume change on the accessible capacities of porous silicon-graphite composite anodes.” Journal of The Electrochemical Society, 166(6), A1251. Garrick, T. R., Higa, K., Wu, S. L., Dai, Y., Huang, X., Srinivasan, V., & Weidner, J. W. (2017). “Modeling battery performance due to intercalation driven volume change in porous electrodes.” Journal of The Electrochemical Society, 164(11), E3592. Garrick, T. R., Huang, X., Srinivasan, V., & Weidner, J. W. (2017). “Modeling volume change in dual insertion electrodes.” Journal of The Electrochemical Society, 164(11), E3552. Garrick, T. R., Dai, Y., Higa, K., Srinivasan, V., & Weidner, J. W. (2016). “Modeling battery performance due to intercalation driven volume change in porous electrodes.” Ecs Transactions, 72(11), 11. Garrick, T. R., Kanneganti, K., Huang, X., & Weidner, J. W. (2014). “Modeling volume change due to intercalation into porous electrodes.” Journal of The Electrochemical Society, 161(8), E3297.

Computational fluid dynamics (CFD) has been employed extensively for modeling fuel cells, but electrolysis has lacked this degree of attention in literature. As electrolysis commercialization advances, the desire to use numerical methods to aid the engineering process grows. The work described in this presentation aims to link channel/manifold geometry, porous media design, and operating conditions to cell performance in the context of mass transport and identify important unknown input quantities to which models are particularly sensitive. CFD is applied to electrolysis systems to quantify the impact of two-phase flow patterns and porous media properties on energy losses, primarily those linked directly to the presence of the gas phase. 3D models for proton exchange and alkaline electrolysis devices are summarized. For proton exchange electrolysis, a homogeneous two-phase model was built in order to estimate the species composition at the anode and how operating conditions and porous transport layer (PTL) properties influence distributions. The model suggests that cell performance is particularly sensitive to the evaporation rate and PTL permeability when the contribution of the gas-phase reaction is considered. A similar model was applied to alkaline diaphragm electrolysis to study effects of the manifolds on the flow distribution and thereby local performance. Current and gas crossover were correlated with cell geometry and altered by the cell potential and feed rate. Figure 1

To expand the commercialization of polymer electrolyte membrane water electrolysis (PEMWE) devices, it is beneficial to understand how cell geometry and porous media properties can impact cell performance. Due to the use of precious materials in PEMWE, particularly with an acidic membrane, it is cost-effective to simulate cell performance using a number of proposed designs to limit the number of prototypes. The use of three-dimensional (3-D) computational fluid dynamics (CFD) to simulate PEMWE ¹ and alkaline ² electrolysis operation has been previously demonstrated. This analysis sheds additional light on evaporation and the important role that it plays in facilitating the anodic and cathodic reactions. Evaporation rates in porous media vary immensely with changes in water content, which has been demonstrated experimentally. Zenyuk et al. ³ used computed tomography to quantify the liquid saturation and gas/liquid interfacial area inside a carbon gas diffusion layer. They linked these variables to evaporation rate using the injection feed pressure to adjust the liquid saturation. The authors determined that evaporation rates in fuel cells increase dramatically with a decrease in water content. Evaporation rate depends on the specific interfacial area (SIA). Measurements in porous media, namely sands and soils, have shown an increase in SIA with a decrease in liquid saturation. One may notice from Ouni et al. ⁴ that the SIA is indirectly proportional to liquid saturation when the maximum SIA is small and somewhat inversely proportional when the SIA is large. The nature of these relationships is considered in the present CFD model for evaporation in the porous transport layer (PTL) and catalyst layer. This study explores the effects of manifold geometry, flow field geometry, and properties such as PTL porosity, permeability, interfacial area, and anisotropy on local current density. Special emphasis is given to the contribution of the gas phase to the overall current and the conditions under which the gas-phase reaction is favorable. Changes in operating conditions, such as the feed temperature, feed rate, and cell potential, and how they impact local void fraction, relative humidity, and temperature at the anode are also investigated. The sensitivity of overall performance to material properties was found to be dependent on these operating conditions, primarily the anode inlet feed rate. References J. Lopata, Z. Kang, J. Young, G. Bender, J. W. Weidner, H-S. Cho, and S. Shimpalee, J. Electrochem. Soc., 168, 054518 (2021). J. S. Lopata, S-G. Kang, H-S. Cho, C-H. Kim, J. W. Weidner, S. Shimpalee, Electrochim. Acta, 390, 138802 (2021). I. V. Zenyuk, A. Lamibrac, J. Eller, D. Y. Parkinson, F. Marone, F. N. Büchi, and A. Weber, J. Phys. Chem. C, 120, 28701-28711 (2016). A. E. Ouni, B. Guo, H. Zhong, M. L. Brusseau, Chemosphere, 263, 128193 (2021). Figure 1

Automotive manufacturers are currently working to produce commercially-viable electric trucks, driving the need to develop batteries that are higher in energy density and lower in cost. To realize this, cell designers have introduced blended silicon-graphite anodes to combine the high energy density of silicon with the stability and relatively lower mechanical degradation of graphite. As more blended anodes with high lithiation-based volume change are considered, the need to simultaneously account for mechanical and electrochemical phenomena increases. In this study, the focus is to learn how preferential lithiation (caused by differing equilibrium potentials and other intercalation kinetics of the two blended active materials) impact the coupled electrochemical performance and mechanical phenomenon at the electrode and cell scales. To do this, adaptations of previous modeling methods are proposed that treat the active materials as separate particles, representing the mixing of two active materials powders within a slurry. For comparison, the historically-used assumption is shown, where the blended active materials lithiate uniformly. The resulting simulations show that preferential lithiation of the blended materials will have a significant impact on both electrochemical and mechanical phenomena. Discussion is also provided with regard to C-rate, blended electrode composition, and other mechano-electrochemical behavior.