Modeling Reversible Volume Change in Automotive Battery Cells with Porous Silicon Oxide-Graphite Composite Anodes

Automotive battery manufacturers are working to improve the individual cell and overall pack design by increasing durability, performance, and range, while reducing cost, and active material volume change is a key aspect that needs to be considered during this design process. Recently, silicon oxide-graphite composite anodes are being explored to increase total anode capacity while maintaining a tolerable amount of cell level reversible volume expansion due to the relatively lower reversible volume change of the silicon oxide compared to pure battery grade or metallurgical grade silicon. To predict the blended anode response and contribution to the overall cell volume change, we integrated the mechanical behavior of the individual active materials with the multi-species, multi-reaction model to predict the state-of-lithiation of the active materials in the cell at a given potential. The resulting simulations illustrate the tradeoff in volume change between the silicon oxide and the graphite during cell operation. This type of modeling approach will allow designers to virtually consider the impact of cell level and pack level design changes on overall system mechanical performance for automotive and grid storage applications, namely that relatively small addition of silicon containing materials can drive a significant increase in the volume change at the cell level, as demonstrated by the 5 wt% addition of silicon oxide accounting for half of the overall volume change in the cell.

Graphene–polymer hydrogels with stimulus-sensitive volume changes

To maintain the intracellular concentration of ions and small molecules on osmotic challenges, nature has developed highly sophisticated transport systems for regulating water and ion content. An ideal measurement technique for volume changes of cells during osmotic challenges has to fulfil two requirements: it has to be osmotically inert, and it should allow online monitoring of cell volume changes. Here, a simple fluorescence microscopy-based approach is presented. Using fluorescein as a negative stain, it is possible to monitor cell volume changes without affecting the functionality of cell membranes and cell osmolarity. Measurement of Madine-Darby canine kidney (MDCK) cells after hypo- and hyperosmotic challenges reveals the main advantages of this approach: besides providing precise and reproducible quantitative data on reversible cell volume changes, the viability of the cells can be assessed directly by the appearance of stain in the cytoplasm. This becomes evident especially after hypo-osmotic challenge of glutaraldehyde-treated cells, which become leaky after fixation, followed by a massive volume change. This new approach represents a very sensitive measurement technique for cell volume changes resulting from water or ion flux, and thus seems to be an ideal tool for studying cell volume regulatory processes.

The osmotic behavior and permeability to non-electrolytes of mitochondria

Automotive manufacturers are working to improve individual cell, module, and overall pack design by increasing the performance, range, and durability, while reducing the cost1. One key piece to consider during the design process is the volume change associated with the electrochemical phenomena in the battery cell and the interplay with the structural components in the rechargeable energy storage system. Because the time from initial design to manufacture of electrified propulsion systems decreases, design work that used to occur with physical testing needs to move into the virtual domain, therefore, coupling electrochemical and mechanical models that account for volume change and variation is necessary.During operation of lithium-ion batteries, cells experience volume change due to mechanical and electrochemical phenomena which is tied to the active material, particle, and electrode level volume changes. This volume change can be described in two main modes: reversible and irreversible, where the former is associated with the movement of lithium from one electrode to the other during a single charge or discharge event, and the latter is associated with various aging processes. Reversible volume expansion at the active material level can range from zero to ten percent for graphitic anodes as charging occurs2–4, or up to 400% for silicon containing anodes5–7. This leads to capacity loss8, reducing performance of the cell and driving other destructive behaviors during electrochemical operation. Irreversible volume change permanently affects cell performance, often lowering the maximum capacity of cells over time making them less effective in storing energy. Irreversible volume change9 can come from a few different sources such as gasification of the electrolyte, dendritic growth or plating of lithium metal, and SEI growth on the active material8. These phenomena reduce the effectiveness of battery cells by removing working ions from the electrolyte and blocking intercalation sites of the active material.In this work, discrete element simulations10 (DEM) have been developed to quantify local volume change. These DEM simulations utilize data from electrochemical simulations11,12 with an equivalent microstructure, which have been informed from experimental measurements at a cell level. This can be coupled with reversible volume expansions in the DEM framework to give a full picture of volume change at the electrode/electrolyte microscale. The irreversible volume change predicted by the DEM simulations is used to estimate capacitive losses in the cell over time.References T. R. Garrick, Y. Zeng, J. B. Siegel, and V. R. Subramanian, J. Electrochem. Soc., 170, 113502 (2023).D. J. Pereira et al., J. Electrochem. Soc., 167, 080515 (2020).T. R. Garrick et al., J. Electrochem. Soc., 170, 060548 (2023).T. R. Garrick et al., J. Electrochem. Soc., 171, 073507 (2024).D. J. Pereira, J. W. Weidner, and T. R. Garrick, J. Electrochem. Soc., 166, A1251 (2019).D. J. Pereira, A. M. Aleman, J. W. Weidner, and T. R. Garrick, J. Electrochem. Soc., 169, 020577 (2022).T. R. Garrick et al., Journal of The Electrochemical Society, 171, 103509 (2024).S. Pannala, H. Movahedi, T. R. Garrick, A. G. Stefanopoulou, and J. B. Siegel, J. Electrochem. Soc., 171, 010532 (2024).T. R. Garrick, Y. Miao, E. Macciomei, M. Fernandez, and J. W. Weidner, J. Electrochem. Soc., 170, 100513 (2023).H. Teel et al., J. Electrochem. Soc., 171, 083507 (2024).H. Teel et al., J. Electrochem. Soc., 171, 083504 (2024).J. S. Lopata et al., J. Electrochem. Soc., 170, 020530 (2023).

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. To improve the balance between cost, stability, performance, and volume change behavior, some cell designers have introduced the use of multiple active materials within the same composite electrode. For example, LiMn2O4 (LMO) and LiNi1/3Co1/3Mn1/3O2 (NMC) active materials are both included in cathodes to benefit from this balance. In anodes, some designers have included both silicon and graphite to maximize gravimetric capacity while maintaining a tolerable degree of volume expansion to prevent damage to the cell and pack structure.While the inclusion of multiple active materials can be used to better tune electrode performance, stability, and volume change for specific applications, the modeling of these electrodes is significantly more complicated. Previously, Albertus et. al developed a model to account for multiple active materials within the same positive electrode.(1) Their model took the concept of a pseudo-two dimensional Li-ion cell model and incorporated multiple pseudo second-dimensions, which correlates to the radial direction of a theoretical active material particle. Therefore, they could account for each active material separately, where previously, an average particle radius, average film resistance, and average equilibrium potential would be assumed for the total electrode.In the study shown here, we build upon this modeling concept by incorporating our previously developed mechano-electrochemical equations to account for active material volume change.(2-5) Figure 1 shows an example of equilibrium potentials for two anode active materials as a function of lithiation fraction. The difference between these equilibrium potentials will dictate the preferential lithiation of the materials, and thus, the rate at which each material undergoes lithiation-based volume change. This allows for the simulation of volume change in diffusion-governed (high rate) or kinetic-governed (low rate) charge and discharge.The relationships between anode/cathode capacity, electrode voltages, and active material volume will be discussed. References P. Albertus, J. Christensen and J. Newman, Journal of The Electrochemical Society, 156, A606 (2009).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. Equilibrium potential as a function of lithiation fraction for two anode active materials. Figure 1

EC-AFM investigation of reversible volume changes with electrode potential in polyaniline

Automotive manufacturers are working to improve individual cell, module, and overall pack design by increasing the performance, range, and durability, while reducing cost. One key piece to consider during the design process is the active material volume change, its linkage to the particle, electrode, and cell level volume changes, and the interplay with structural components in the rechargeable energy storage system. As the time from initial design to manufacture of electric vehicles decreases, design work needs to move to the virtual domain; therefore, a need for coupled electrochemical-mechanical models that take into account the active material volume change and the rate dependence of this volume change need to be considered. In this study, we illustrated the applicability of a coupled electrochemical-mechanical battery model considering multiple representative particles to capture experimentally measured rate dependent reversible volume change at the cell level through the use of an electrochemical-mechanical battery model that couples the particle, electrode, and cell level volume changes. By employing this coupled approach, the importance of considering multiple active material particle sizes representative of the distribution is demonstrated. The non-uniformity in utilization between two different size particles as well as the significant spatial non-uniformity in the radial direction of the larger particles is the primary driver of the rate dependent characteristics of the volume change at the electrode and cell level.

ABSTRACTPresently, rechargeable Li-ion batteries, possessing highest energy densities among all batte-ries, are used in a major fraction of all portable electronic devices. However, for bestowing the Li-ion batteries suitable for such advanced applications, further improvements in the energy densities (Li-capacities) and in the cycle life are essential. In a broader sense, this can be achieved by replacing the presently used electrode materials by materials possessing higher Li-capacities and minimization of the degradation of such materials with electrochemical cycling. It has been realized that the major reason for degradation in battery performance in terms of capacity with cycling is the disintegration/fragmentation of the active electrode materials due to stresses generated during Li-intercalation/de-intercalation in every cycle. Such stresses arise from the reversible volume changes of the active electrode materials during Li-insertion and removal. In quest of higher energy densities, replacement of the presently used graphitic carbon by potentially higher capacity metallic anode materials (like Si, Sn, and Al) is likely to further accrue this stress related disintegration due to ∼30 times higher volume changes experienced by such materials. It has also been recently realized that passivating layer formed on the surface of the electrodes also contributes toward the stress development. After briefly introducing the mechanistic aspects of Li-ion batteries, this article focuses on the reasons and consequences associated with stress developments in different electrode materials, highlighting the various strategies, in terms of designing new electrode com-positions or reducing the microstructural scale, that are being presently adopted to address the stress-related issues. Considering that experimental determination of such stresses is essential toward further progress in Li-ion battery research, this article introduces a recently reported technique developed for real-time measurement of such stresses. It finally concludes by raising some critical issues that need to be resolved through further research in this area.

A method for studying cells based on low‐angle light scattering was applied to cell volume and cell signaling studies on Ehrlich ascite tumor cells (EATC). Changes in the volume of EATC were measured in hypotonic medium, as well as after activation with exogenous ATP, ionomycin and thimerosal. Increase of [Ca2+]i under ATP and ionomycin action induced reversible changes of cell volume: fast shrinking was followed by swelling. Thimerosal caused a reversible change in EATC volume with high amplitude; endoplasmic reticulum played the key role in this response. Having obtained kinetic parameters of changes in cell volume under activation of the cells, quantitative measurements of K+, Na+ and anion flows responsible for this process can then be obtained. In spite of some fundamental differences in the behavior of cells of different dimensions there are many similarities, and there is a good theoretical background for dealing with both small and large cells.

Making sense of the sensor: Mysteries of the macula densa

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. Designers try to control or mitigate the effects of volume change using a variety of methods: inserting foam layers into battery packs, programming specific charging algorithms, using multiple active materials, etc. However, designers must resort to extensive testing to fully develop these methods for each new battery design because of the complexity in measuring and understanding the links between active material volume change’s mechano-electrochemical effects on the electrode and cell level. A multi-scale modeling approach shows promise to comprehensively account for active material volume change. In the work shown here, a mechano-electrochemical model was employed [1-4] to explore mechano-electrochemical relationships: (1) understanding the effects of realistic mechanical behavior of each cell component including foam packaging, (2) understanding the effects of thermodynamically non-ideal volume change behavior, and (3) relative lithiation (thus, volume change) behavior for electrodes with multiple active materials (such as a silicon-graphite composite anode). The unique ties between active material voltage, active material volume, and N:P capacity ratio will be discussed as well. 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).

Saccharomyces cerevisiae has evolved diverse mechanisms to osmotic changes: the cell wall, ion and water transport systems, and signaling cascades. At the present time, little is known about the mechanisms involved in short-term responses of osmotic stress in yeast or their physiological state during this process. We conducted studies of flow cytometry, wet weight measurements, and electron microscopy to evaluate the modifications in cell volume and the cell wall induced by osmotic stress. In response to osmotic challenges, we show very fast and drastic changes in cell volume (up to 60%), which were completed in less than eight seconds. This dramatic change was completely reversible approximately 16s after returning to an isosmotic solution. Cell volume changes were also accompanied by adaptations in yeast metabolism observed as a reduction by 50% in the respiratory rate, measured as oxygen consumption. This effect was also fully reversible upon returning to an isosmotic solution. It is noteworthy that we observed a significant recovery in oxygen consumption during the first 10min of the osmotic shock. The rapid adjustment of the cellular volume may represent an evolutionary advantage, allowing greater flexibility for survival.

The laminar pulvinus of primary leaves of Phaseolus coccineus L. was investigated with respect to the total K(+) content, the apoplastic K(+) content, and the water potential of extensor and flexor sections in relation to the leaf positions in a circadian leaf-movement cycle, as well as the cation-exchange properties of isolated extensor- and flexor-cell walls. Turgid tissue showed a high total but low apoplastic K(+) content, shrunken tissue a low total but high apoplastic K(+) content. Thus, part of the K(+) transported into and out of the swelling or shrinking protoplasts is shuttled between the protoplasts and the surrounding walls, another part between different regions of the pulvinus. The K(+) fraction shuttled between protoplasts and walls was found to be 30-40% of the total transported K(+) fraction. Furthermore, 15-20% of the total K(+) content of the tissue is located in the apoplast when the apoplastic reservoir is filled, 5-10% when the apoplastic reservoir is depleted. The ion-exchange properties of walls of extensor and flexor cells appear identical in situ and in isolated preparations. The walls behave as cation exchangers of hhe weak-acid type with a strong dependence of the activity of fixed negative charges as well as of the K(+)-storing capacity on pH and [K(+)] of the equilibration solution. The high apoplastic K(+) contents of freshly cut tissues reflect the cation-storing capacity of the isolated walls. We suggest that K(+) ions of the Donnan free space are used for the reversible volume changes (mediating the leaf movement) mainly by an electrogenic proton pump which changes the pH and-or the [K(+)] in the water free space of the apoplast.

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.