Volume Change Of Materials Research Articles

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.

High-energy bimetallic substituted Na3V2(PO4)3 cathode for advanced sodium-ion batteries

NASICON-type cathodes have attracted great attention due to their open three-dimensional (3D) frame structure and excellent ion transport properties. Accordingly, how to improve the stability and energy density of materials is a hot topic of research. In this study, the significant effects of aluminum-zirconium bimetallic substitution on electrode kinetics and structural stability are reported. The designed Na2.9V1.8Al0.1Zr0.1(PO4)3 cathode exhibits a highly reversible capacity of 107 mAh g-1 at 1C and decent cyclic stability (75 mAh g-1 capacity after 2000 cycles at 20C). These excellent electrochemical properties can be attributed to expanding the lattice structure and activating part of V4+, which facilitates the migration of Na+ and increases the reversible capacity. The cyclic voltammetry, electrochemical impedance spectra and galvanostatic intermittent titration technique tests analyze the diffusion kinetics of sodium ions and confirm the desired sodium ion diffusion coefficients (DNa+). In situ X-ray diffraction reveals reversible structural changes during the electrochemical reaction, which confirms that the bimetallic doping strategy slows down material volume change. This work provides a new perspective for the construction of high-performance NASICON cathode materials.

Quantifying Volume Change in Porous Electrodes via the Multi-Species, Multi-Reaction Model

Automotive 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. As the time from initial design to manufacture of electric vehicles is decreased, design work that used to rely solely on testing needs to be supplemented or replaced by virtual methods. As electrochemical engineers drive battery and system design using model-based methods, the need for coupled electrochemical/mechanical models that take into account the active material change utilizing physics based or semi-empirical approaches is necessary[1-9]. In this study[10], we illustrated the applicability of a mechano-electrochemical coupled modeling method considering the multi-species, multi-reaction model as popularized by Verbrugge[11-16] and Baker. To do this, validation tests were conducted using a computer-controlled press apparatus that can control the press displacement and press force with precision. The coupled MSMR volume change model was developed and its applicability to graphite and NMC cells was illustrated. The increased accuracy of the model considering the coupled MSMR volume change approach shows in the importance of accounting for individual gallery volume change behavior on cell level predictions. 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, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017).T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (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).T. R. Garrick, J. Gao, X. Yang and B. Koch, J Electrochem. Soc., 168 (1) 010530 (2021)D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022).T. R. Garrick, Y. Miao, E. Macciomei, M. Fernandez and J. W. Weidner, J Electrochem Soc, 170, 100513 (2023).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)M. Verbrugge, D. Baker and X. Xiao, J Electrochem Soc, 163, A262 (2016).M. Verbrugge, D. Baker, B. Koch, X. Xiao and W. Gu, J Electrochem Soc, 164, E3243 (2017).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 165, A3952 (2018).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 167, 013504 (2019).D. R. Baker, M. W. Verbrugge and W. Gu, J Electrochem Soc, 166, A521 (2019).M. W. Verbrugge, X. Xiao and D. R. Baker, J Electrochem Soc, 167, 080523 (2020).

Modeling Rate Dependent Volume Change in Porous Electrodes in Lithium-Ion Batteries

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.

Stabilized Nickel‐Rich‐Layered Oxide Electrodes for High‐Performance Lithium‐Ion Batteries

Next‐generation Li‐ion batteries are expected to exhibit superior energy and power density, along with extended cycle life. Ni‐rich high‐capacity layered nickel manganese cobalt oxide electrode materials (NMC) hold promise in achieving these objectives, despite facing challenges such as capacity fade due to various degradation modes. Crack formation within NMC‐based cathode secondary particles, leading to parasitic reactions and the formation of inactive crystal structures, is a critical degradation mechanism. Mechanical and chemical degradation further deteriorate capacity and lifetime. To mitigate these issues, an artificial cathode electrolyte interphase can be applied to the active material before battery cycling. While atomic layer deposition (ALD) has been extensively explored for active material coatings, molecular layer deposition (MLD) offers a complementary approach. When combined with ALD, MLD enables the deposition of flexible hybrid coatings that can accommodate electrode material volume changes during battery operation. This study focuses on depositing ‐titanium terephthalate thin films on a electrode via ALD‐MLD. The electrochemical evaluation demonstrates favorable lithium‐ion kinetics and reduced electrolyte decomposition. Overall, the films deposited through ALD‐MLD exhibit promising features as flexible and protective coatings for high‐energy lithium‐ion battery electrodes, offering potential contributions to the enhancement of advanced battery technologies and supporting the growth of the EV and stationary battery industries.

Instabilities of an inflated and extended doubly fiber-reinforced cylindrical membrane under damage processes and different natural configurations of its constituents with application to abnormal artery dilation

This article studies extended and inflated tubes made of doubly fiber-reinforced hyperelastic material in which the constituents undergo damage processes at large deformations. Damage processes are initiated by a combination of external loads and material characteristics including volume changes in the ground substance matrix and constituents with different natural configurations. The inflation of such a cylinder is stable at relatively small deformations. Under higher inflation pressures the cylinder is likely to develop various types of instabilities that are shown to be related to loading, geometry, and (current) mechanical properties of the solid. Analyses focus on the role of material volume changes, fiber pre-stretch, and damage processes in the initiation of bulging and inflation-jump instabilities.

Quantifying Volume Change in Porous Electrodes Via the Multi-Species, Multi-Reaction Model

Automotive 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. As the time from initial design to manufacture of electric vehicles is decreased, design work that used to rely solely on testing needs to be supplemented or replaced by virtual methods. As electrochemical engineers drive battery and system design using model-based methods, the need for coupled electrochemical/mechanical models that take into account the active material change utilizing physics based or semi-empirical approaches is necessary[1-8]. In this study, we illustrated the applicability of a mechano-electrochemical coupled modeling method considering the multi-species, multi-reaction model as popularized by Verbrugge[9-14] and Baker. To do this, validation tests were conducted using a computer-controlled press apparatus that can control the press displacement and press force with precision. The coupled MSMR volume change model was developed and its applicability to graphite and NMC cells was illustrated. The increased accuracy of the model considering the coupled MSMR volume change approach shows in the importance of accounting for individual gallery volume change behavior on cell level predictions. 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, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017).T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (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).T. R. Garrick, J. Gao, X. Yang and B. Koch, J. Electrochem. Soc. (2021).D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022).M. Verbrugge, D. Baker and X. Xiao, J Electrochem Soc, 163, A262 (2016).M. Verbrugge, D. Baker, B. Koch, X. Xiao and W. Gu, J Electrochem Soc, 164, E3243 (2017).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 165, A3952 (2018).D. R. Baker and M. W. Verbrugge, J Electrochem Soc, 167, 013504 (2019).D. R. Baker, M. W. Verbrugge and W. Gu, J Electrochem Soc, 166, A521 (2019).M. W. Verbrugge, X. Xiao and D. R. Baker, J Electrochem Soc, 167, 080523 (2020).

Remarks on bifurcation of an inflated and extended swellable isotropic tube

We consider a tubular membrane whose mechanical behavior is defined by a strain energy density function that combines the neo-Hookean model with the Demiray model. Both, the neo-Hookean and the Demiray models are isotropic material models, which found their application in the modeling of the mechanical behavior of biological soft tissue. This tubular membrane is subjected to an inner pressure, an axial stretch, and a change in the material volume due to swelling or deswelling. The interplay between the cylinder geometry and the loading conditions and different instability modes, namely, bulging bifurcation, bending bifurcation, and prismatic bifurcation, are studied. It is shown that a change in the material volume has a strong effect on the occurrence of these bifurcation modes because a change in the material volume may stabilize the cylinder against a particular bifurcation mode and may trigger another bifurcation mode at the same time. Despite the restriction to isotropic material behavior, this article shows that the material response to pressure, axial stretch, and material volume change is quite complex.

(Invited) Modeling Aging Induced Volume Change of Porous Electrodes

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.

Understanding the Expansion and Electrochemistry of Nickel-Rich NMC - Graphite Full Cells Using in-Situ Dilatometry

The higher energy density and lower cost of Ni-rich lithium nickel manganese cobalt (NMC) have made them one of the best cathode materials for Li-Ion batteries (LIBs). Understanding the mechanical behaviour, particularly the volume changes during charging and discharging, is important for the cell design. So far, this has mainly been studied using X-ray diffraction (XRD), which is powerful in understanding the nanoscale crystal level of the material volume change. However, recent papers have shown that XRD is insufficient to capture macroscopic cell expansion [1]. It is also getting more important to consider the synergistic effect of cathodes and anodes in the context of full cells. It is therefore valuable to have in-situ dilatometry filling the gap and unravelling how nano and macro electrochemical and mechanical behaviour differs.Here, we coupled electrochemical analysis with in-situ electrochemical dilatometry to observe macroscopic dimensional changes of NMC811−graphite full cells during galvanostatic cycling under different pressure conditions, voltages, and cathode particle morphologies. Our setup uses a non-contact dilation sensor and independent control over the stack pressure to achieve highly accurate measurements of the electrode expansion, with a linearity of ≤ ±90 nm, resolution of ≤ 0.5 nm, and a drift of ≤ 100 nm/month.The initial investigations of graphite v.s. NMC811 pouch cells (220 mAh) have offered clear evidence of the strong correlation between dilation and electrochemistry, where reversible dilation features in every charge-discharge cycle can be assigned to cathode and anode phase transitions. In addition, our system can effectively isolate the reversible thickness change from the irreversible thickness change known to be potentially correlated to solid electrolyte interphase (SEI),[2] particle rearrangement,[3] and electrode delamination.[4] With different experimental conditions (C-rates, pressure and voltage windows), the full cells demonstrated different electrochemical performances alongside varied dilation behaviours. The observed in-situ dimensional changes improve our understanding of the physical and chemical processes happening while cycling NMC-Graphite full cells.[1] F. B. Spingler, S. Kücher, R. Phillips, E. Moyassari, and A. Jossen, “Electrochemically Stable In Situ Dilatometry of NMC, NCA and Graphite Electrodes for Lithium-Ion Cells Compared to XRD Measurements,” J. Electrochem. Soc., vol. 168, no. 4, p. 040515, 2021, doi: 10.1149/1945-7111/abf262.[2] A. J. Louli, L. D. Ellis, and J. R. Dahn, “Operando Pressure Measurements Reveal Solid Electrolyte Interphase Growth to Rank Li-Ion Cell Performance,” Joule, vol. 3, no. 3, pp. 745–761, 2019, doi: 10.1016/j.joule.2018.12.009.[3] D. Y. W. Yu, M. Zhao, and H. E. Hoster, “Suppressing Vertical Displacement of Lithiated Silicon Particles in High Volumetric Capacity Battery Electrodes,” ChemElectroChem, vol. 2, no. 8, pp. 1090–1095, 2015, doi: 10.1002/celc.201500133.[4] H. Michael et al., “A Dilatometric Study of Graphite Electrodes during Cycling with X-ray Computed Tomography,” J. Electrochem. Soc., vol. 168, no. 1, p. 010507, 2021, doi: 10.1149/1945-7111/abd648.

Quantifying Volume Change in Porous Electrodes via the Multi-Species, Multi-Reaction Model

Automotive 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. As the time from initial design to manufacture of electric vehicles is decreased, design work that used to rely solely on testing needs to be supplemented or replaced by virtual methods. As electrochemical engineers drive battery and system design using model-based methods, the need for coupled electrochemical/mechanical models that take into account the active material change utilizing physics based or semi-empirical approaches is necessary. In this study, we illustrated the applicability of a mechano-electrochemical coupled modeling method considering the multi-species, multi-reaction model as popularized by Verbrugge and Baker. To do this, validation tests were conducted using a computer-controlled press apparatus that can control the press displacement and press force with precision. The coupled MSMR volume change model was developed and its applicability to graphite and NMC cells was illustrated. The increased accuracy of the model considering the coupled MSMR volume change approach shows in the importance of accounting for individual gallery volume change behavior on cell level predictions.

Experimental and numerical study on the shrinkage-deformation of carrot slices during hot air drying

In order to further understand the mechanism of material volume change in the drying process, numerical simulations (considering or neglecting shrinkage) of heat and mass transfer during convective drying of carrot slices under constant and controlled temperature and relative humidity were carried out. Simulated results were validated with experimental data. The results of the simulation show that the Quadratic model fitted well to the moisture ratio and the material temperature data trend with average relative errors of 5.9% and 8.1%, respectively. Additionally, the results of the simulation considering shrinkage show that the moisture and temperature distributions during drying are closer to the experimental data than the results of the simulation disregarding shrinkage. The material moisture content was significantly related to the shrinkage of dried tissue. Temperature and relative humidity significantly affected the volume shrinkage of carrot slices. The volume shrinkage increased with the rising of the constant temperature and the decline of relative humidity. This model can be used to provide more information on the dynamics of heat and mass transfer during drying and can also be adapted to other products and dryers devices. Keywords: carrot drying, numerical simulation, heat, and mass transfer, shrinkage DOI: 10.25165/j.ijabe.20231601.6736 Citation: Jiang D L, Li C C, Lin Z F, Wu Y T, Pei H J, Zielinska M, et al. Experimental and numerical study on the shrinkage-deformation of carrot slices during hot air drying. Int J Agric & Biol Eng, 2023; 16(1): 260–272.

Methods for testing solubility of hydraulic calcium silicate cements for root-end filling

Regulatory testing of hydraulic cements used in dentistry and standard test methods for root-end filling materials do not exist. The aim of this study was to identify a simple, reproducible method for testing the solubility of materials that set with water (hydraulic) used as root-end filling materials in dentistry. Commercial and prototype hydraulic cements were characterized by scanning electron microscopy and X-ray diffraction analyses and their solubilities were determined using ISO 6876; 2012 standard, a modified ISO 6876 method with media alternative to water and a new method measuring the percentage mass loss and volume change of materials (micro-CT method) from a single surface exposed to three solutions. The solubility testing was performed by three operators to enable an intra-laboratory comparison. The solubility data obtained from the two commercial and two prototype materials varied depending on the method used, with the ISO 6876 method identifying differences in solubility of the materials (p < 0.05) but when modified with alternative solutions, no differences were found (p > 0.05). The changes in solution thus effected the solubility of the tested materials. Inter-operator differences were observed with the weight changes determined from the new method indicating this method was not robust. The weight and volume assessments using the new method were not solution-dependent. The advantage of the proposed method compared with the ISO standard is its simplicity, enabling a number of tests to be performed on the same set of samples that also more closely mimics the clinical environment.

Developments in Mechano-Electrochemical Modeling Methods for Battery Electric Vehicles

Automotive battery manufacturers are improving individual cell and overall battery pack design by focusing on increasing their 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, such as silicon. Battery pack engineers mitigate the effects of volume change using a variety of methods, though, these mitigation strategies rely on extensive testing with each change in chemistry or pack design due to the complexity in measuring and understanding the links between active material volume change’s effects on multiple scales.In this presentation, improvements to a previously developed mechano-electrochemical model(1-3) were made to more practically understand impacts of active material volume change. First, a representative volume element model was incorporated into the model geometry to more realistically understand how cell components mechanically interact with each other.(4) This allowed for a better understanding of how individual components, including foam inserts, and the overall cell reacts to the active material volume change of a silicon-graphite electrode upon charge to generate realistic predictions of pressure and porosity changes. Second, the thermodynamically non-ideal active material volume change was accounted for to account for the non-linear volume change of silicon and graphite active materials.(5) A mechano-electrochemical measurement apparatus was developed and used to compare results with simulation. Further discussion will be provided on concepts important to the automotive industry, such as the mechanical effects of N:P capacity ratio, porosity limitations for different cell types, etc.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).

Electro-mechanical behaviour of ferroelectrics: Insights into local contributions from macroscopic measurements

The behaviour of a bulk lead zirconate titanate ceramic has been characterised under combined high stress and high electric field. The electrical response of the sample was monitored, and Digital Image Correlation (DIC) was used to characterise the strain field at the surface of the sample. The DIC technique allows both longitudinal and transverse strains to be measured simultaneously. The results showed that a compressive stress of 25 MPa increases the susceptibility by 128% and the longitudinal piezoelectric coefficient by 47%. A further increase of stress has reversed this trend and under a 500 MPa compression, the susceptibility has fallen by 71% and the longitudinal piezoelectric coefficient by 98% compared to the unstressed case. The analysis of the ferroelastic contribution revealed that this decrease is explained by a saturation of the ferroelastic switching, beginning at the coercive field. The material volume change during loading was computed using the DIC results. It was found that a negligible piezoelectric activity remains at 500 MPa while ferroelastic switching still occurs and is reversible. This work shows that it is possible to obtain quantitative insights into the physical mechanisms underlying the macroscopic behaviour of ferroelectrics using the DIC technique without requiring the use of local investigation technique.

The main problems and solutions in practical application of anode materials for sodium ion batteries and the latest research progress

Lithium-ion batteries(LIBs) have been widely used in people's daily lives. At the same time, in the face of the growing demand for LIBs, the minable lithium mines on the earth are facing resource exhaustion. From the perspective of sustainable development, it is inevitable to seek new batteries. Sodium-ion batteries(SIBs) are attracting attention due to their rich resources and low cost, and are expected to be used in large-scale energy storage. In recent years, anode materials have made a lot of important progress as the key elements of SIBs. The research of anode materials is mainly concentrated on carbon-based materials, titanium-based materials, alloying materials, conversion materials, and organic materials. However, due to the large sodium ion radius, the large volume change of materials, and slow kinetics, the electrochemical performance of the materials is poor. This article systematically summarizes the latest research progress of these types of anode materials and discusses the main existing problems and the solution strategy and the prospect of the development of negative electrode materials.

Effect of polyvinyl alcohol/aluminum microcapsule expansion agent on porosity and strength of cement-based drilling sealing material

In the process of gas drainage, the cement-based expansion sealing material with excellent permeability can effectively seal the cracks in the roadway pressure relief zone and the broken drilled area. However, expansion material has low strength and poor compactness. Therefore, the authors use microcapsule technology to modify the expansion agent to make the material expand after reaching sufficient strength, weaken the influence on the material structure and pores, achieve the coordinated development of expansion and performance, and improve the efficiency of gas drainage. In the paper, the uniaxial compression experiment and NMR experiment combined with the fractal dimension and material volume change is used to quantitatively analyze the influence of delayed expansion on the mechanical strength, porosity and pore connectivity of the sealing material. Experimental data proves the feasibility of applying microcapsule technology. The results show that the slope of the curve between the expansion rate and peak stress, porosity of ordinary expansion materials is 0.9931 and 0.0672, which is greater than 0.8925 and 0.0563 of microcapsule expansion materials. Microcapsule material has high strength, low porosity, and better sealing effect. Besides, the proportion of adsorption holes in the microcapsule material increases, and the seepage holes decrease.

Modeling the Impact of Active Material Volume Change on Accessible Capacity in Automotive Pouch Cells

Lithium-silicon chemistries show promise to increase battery capacity; however, silicon expands significantly during lithium intercalation, leading to inaccessible capacities as well as cell or pack failure due to pressure generation. Silicon-graphite (Si/C) composite anodes are used to increase the anode capacity while maintaining a tolerable degree of active material volume expansion. Recently, Dash and Pannala modeled anodes with increasing Si/C ratios and explored the tradeoff between increasing gravimetric capacity and the increasing active material volume expansion upon Li intercalation [1]. Their conclusion highlights that while the gravimetric capacity increases, there is ultimately a “threshold value” where the volumetric capacity will begin to decrease to account for the significant silicon volume expansion.This concept was built upon to account for electrochemical and mechanical design limitations applicable to battery packs for electric vehicles (EVs). We propose that increasing the Si/C ratio does not directly lead to an increase in the accessible capacity, because excessive volume expansion can lead to unacceptable cell pressure or electrode porosity. In order to predict the accessible capacity as a function of Si/C ratio, we integrated mechanical behavior for each individual cell component (e.g., composite anode, cathode, and foam packing) into our previous battery model [2-4]. This model can predict the split between changes in electrode porosity and dimensions by coupling component mechanical behavior to the volume change governed by electrochemical phenomena.In this presentation, we will focus on how the Si/C ratio will impact both mechanical and electrochemical behavior using our mechano-electrochemical model. Figure 1 shows an example of the pressure generation seen when considering (a) foam packaging and (b) a rigid volume for cells with varying percentages of Si in the anode. Accessible capacities of these materials can then be determined for a specific design’s pressure cutoff. Preliminary modeling of the links between active material Eeq, anode/cathode capacity balance, and volume change will also be discussed.

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

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

Mechano-Electrochemical Simulation of Pouch Cells with Electrodes Containing Multiple Active Materials

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