With sodium-ion batteries (SIBs) entering the energy market, optimizing their performance has become a key research focus. At the electrode level, the parameters selected during their manufacturing process influence their electrodes microstructure and, consequently, the electrochemical performance. Here, we address different manufacturing conditions of hard carbon (HC) negative electrodes by varying the solid content in the slurry (35 and 40 % SC) and the calendering degree applied to the electrodes (uncalendered and 30 % calendered). The 3D microstructure of each sample is acquired using a focused ion beam (FIB) and scanning electron microscopy (SEM) technique, from which the real shape of HC particles is extracted and used to generate input microstructures for a discrete element method (DEM) calendering model designed to address the mechanical electrode behavior and its effects on current collector deformation. Also, the 3D electrode microstructures are used in a finite element method (FEM) model to obtain the electrochemical performance for C-rates ranging from C/50 to C/2, and to compare these results with experimental ones. Furthermore, the DEM predicted microstructures are also injected into the FEM model to validate the electrochemical performance and compare it with the performance of microstructures reconstructed with FIB-SEM. We demonstrate a novel approach combining experimentation and advanced mesoscopic modeling, to address how manufacturing parameters influence the performance of HC electrodes, providing an important guideline for optimizing their production for SIB applications.

Understanding aging mechanisms in Li-ion batteries is critical for optimizing lifetime and performance, yet remains challenging due to the complex interplay of chemical, thermal and mechanical processes across multiple scales. In this study, laser-induced breakdown spectroscopy (LIBS) and NMR cryoporometry were employed to investigate aging mechanisms under two conditions: low-temperature cycling (0 °C, 1C, 100-50% SOC) and high-temperature storage (60 °C, 4.2 V hold). Four commercial NMC811/graphite cells (M50LT) were tested per condition, with one cell periodically removed for post-mortem analysis. Electrodes morphology was examined by SEM, while LIBS, micro-LIBS and ICP provided chemical insights. Porosity, pore size and surface area were assessed through helium pycnometry, NMR cryoporometry and krypton BET respectively. Capacity losses of 3 % and 10 % were obtained after 102 days of aging on stored and cycled cells respectively. Incremental capacity (IC)/differential voltage (DV) and post-mortem analysis demonstrated that these losses were mainly due to SEI growth, lithium-plating (only under cycling), Mn dissolution from NMC electrodes, irreversible lithium trapping in graphite layer and unexpected lithium accumulation in copper current collectors. Analysis of dominant pore size evolution enabled the estimation of surface layer growth. For stored graphite electrodes, SEI growth was identified as the primary degradation mechanism, with an estimated thickness of 22 nm. For cycled graphite, the surface growth resulted from the combined formation of SEI and plated lithium layers, reaching an estimated thickness of ~36 nm.

Hard Carbon (HC) is identified as one of the key materials for the development of Sodium-Ion Batteries (SIBs), and it is the anode choice for first-generation batteries of this kind. Its ability to undergo distinct sodiation processes, however, has made it challenging to optimize its performance. The creation of high-performance HC anodes for SIBs requires a comprehensive understanding of both its microstructure and sodium storage modes [1]. Over the years, scientists have tried to create a global consensus on the sodiation mechanism of this material, but discrepancies have occurred due to the use of different carbons and different characterization techniques [2]. Given that, it is essential to utilize other techniques to study the HC electrode. To gain further insights into the performance of HC, we propose an innovative model for HC, allowing to study the sodiation mechanisms by using continuum physics-based modeling approaches [3]. Our model considers 3D-resolved HC electrode microstructures at the mesoscale, getting inspiration from our previous works for Lithium-Ion Battery electrodes [4], which explicitly considers the different phases of the Active Material (AM), Carbon-Binder Domain (CBD) and the porous one. The electrochemical model was both calibrated and validated against experimental data [5] and evaluates the electrochemical performance by performing Finite Element Method calculations. Our model accounts for the competition between different sodium storage processes. The model has also been used to study the effect of electrode microstructural heterogeneities by testing the impact of different formulation and porosity values on electrochemical performance. This computational model is a new and flexible modeling tool for scientists and engineers that allows to assess the performance of their specific HC materials by directly comparing simulation results with their electrochemical data and using it as a guide for electrode optimization. References: [1] N. Sun, J. Qiu, B. Xu, Understanding of Sodium Storage Mechanism in Hard Carbons: Ongoing Development under Debate, Adv Energy Mater 12 (2022). https://doi.org/10.1002/aenm.202200715. [2] D. Saurel, B. Orayech, B. Xiao, D. Carriazo, X. Li, T. Rojo, From Charge Storage Mechanism to Performance: A Roadmap toward High Specific Energy Sodium-Ion Batteries through Carbon Anode Optimization, Adv Energy Mater 8 (2018). https://doi.org/10.1002/aenm.201703268. [3] I. Cardenas-Sierra, M. Petit, F. Fernadez, A.A. Franco, A Microstructure-Resolved Model of Sodium-Ion Battery Hard Carbon Electrodes, Manuscript in Preparation (2025). [4] C. Liu, T. Lombardo, J. Xu, A.C. Ngandjong, A.A. Franco, An experimentally-validated 3D electrochemical model revealing electrode manufacturing parameters’ effects on battery performance, Energy Storage Mater 54 (2023) 156–163. https://doi.org/10.1016/j.ensm.2022.10.035. [5] H. Tonnoir, D. Huo, R.L.S. Canevesi, V. Fierro, A. Celzard, R. Janot, Tannin-based hard carbons as high-performance anode materials for sodium-ion batteries, Mater Today Chem 23 (2022). https://doi.org/10.1016/j.mtchem.2021.100614.

Given the recent inclusion of sodium-ion batteries (SIBs) in the energy market, the optimization of their performance becomes a relevant research topic. At the electrode-level, the parameters selected during its manufacturing process influence its microstructure and, consequently, its electrochemical performance. Here, we address different manufacturing conditions of hard carbon (HC) negative electrodes by varying the solid content (35 wt% and 40 wt%) and the calendering degree (uncalendered and 30% calendered). The three-dimensional microstructure of each sample is acquired using focused ion beam (FIB) and scanning electron microscopy (SEM) technique, from which the real-shape of HC particles is extracted and used to generate input microstructures for a discrete element method (DEM) calendering model designed to address the mechanical electrode behavior and its effects on current collector deformation. Also, the 3D electrode microstructures are used in a finite element method (FEM) model to obtain the electrochemical performance for C-rates ranging from C/50 to C/5 and to compare these results with experimental ones. Furthermore, the DEM predictions are injected into the FEM model to validate them against the FIB-SEM reference. Overall, we study how manufacturing parameters influence the performance of HC electrodes, providing an important guideline for optimizing their production for SIBs applications.

To improve the design and accelerate the adoption of Sodium-Ion Batteries (SIBs), it is necessary to improve our understanding of the electrochemical behavior of Hard Carbon (HC) negative electrodes. We report here a novel electrochemical model that unravels the sodiation mechanism of HC electrodes. This model considers the explicit 3D-resolved HC electrode microstructure at the mesoscale, operating in a half cell versus sodium metal. We have parameterized and validated this model using structural (particle shape and size, skeletal density, and textural properties) and electrochemical (cycling protocol, experimental capacity, and discharge profile) characterizations of a specific HC material. Then, we used the model to investigate how manufacturing parameters (formulation and porosity) affect the 3D-resolved sodiation heterogeneities, impacting the electrochemical performance at different C-rates. Our model represents the first approach to create a flexible computational tool for researchers and engineers to assess the kinetic and transport limitations of their specific HC material. Furthermore, it can help them understand the underlying sodiation phenomena taking place in their material via direct comparison with their galvanostatic profiles, while considering the sodiation heterogeneities arising from the electrode's 3D microstructure, supporting the ramp-up in the production of SIBs.

BATSS project objective is to design a safe, effective and sustainable battery pack. To achieve this, the battery system (BS) will be mechanically, electrically and thermally optimized using cutting edge technology. Consequently, the battery system includes innovative 4695 cylindrical cells and advanced thermal management, carried out with the Miba FLEXCOOLER®. This work focuses on the BS thermal optimization using system simulation tools. First a simplified version of the BS is simulated with all physical phenomena involved in thermal behavior to identify first order parameters. It appears that various BS component and heat transfer can be neglected in comparison with the heat transfer due to cooling system. Then the simulation of the full battery system is conducted under nominal condition. Cooling system appears to be performant as it allows a controlled averaged temperature and very low cell-to-cell temperature variability. Finally, impact of both design and operating parameters is evaluated. Simulation shows that the coolant mass flow can be reduced by 70% from its nominal value allowing to maintain good thermal performances while reducing the pressure drop in the cooling system. Impact of the Miba FLEXCOOLER® / cell surface exchange is also investigated. Results demonstrate that increasing exchange surface reduces averaged temperature in the pack but slightly increases cell temperature heterogeneities.

In the roadmap toward designing new and improved materials for Lithium ion batteries, the ability to estimate the diffusion coefficient of Li atoms in electrodes, and eventually solid-state electrolytes, is key. Nevertheless, as of today, accurate prediction through computational tools remains challenging. Its experimental measurement does not appear to be much easier. In this work, we devise a computational protocol for the determination of the Li-migration energy barrier and diffusion coefficient, focusing on a common cathode material such as LiNiO2, which represents a prototype of the widely adopted NMC (LiNi1-x-y Mn x Co y O2) class of materials. Different methodologies are exploited, combining ab initio metadynamics, path sampling, and density functional theory. Furthermore, we propose a novel, fast, and simple 1D approximation for the estimation of the effective frequency. The outlined computational protocol aims to be generally applicable to Lithium diffusion in other materials and components for batteries, including anodes and solid electrolytes.

Increasing the silicon content in batteries is expected to enhance their capacity. However, its implementation comes with challenges, as silicon exhibits a large volumetric expansion. This expansion is a significant factor contributing to the decreased lifespan of these batteries. One of the critical degradation mechanisms from a mechanical perspective is the delamination of electrode structure. The cyclability of these negative electrodes is noted to be influenced by the interaction between the binder and particles during battery cycling. The heavy local strain experienced by particles in these electrodes often leads to binder failure, resulting in particle isolation, detachment, or delamination over multiple cycles. A good understanding of the local evolution of the strain is essential in advancing the mechanical modelling of the degradation mechanism and in realizing the complete potential of silicon-based electrodes. In this work, in situ global and local strain measurements were performed by combining synchrotron tomography with Digital Volume Correlation (DVC). The measurements showed that there is significant local strain in these electrodes which can lead to delamination. In addition to this, the spatial variability of the composite electrodes was characterized by estimating the characteristic length to strain, which can be used to replicate the strain field and model the delamination.

Inhomogeneity in Li -ion cells leads to an underutilization of its energy and non -uniform degradation. In our previous work, the proof of concept was established for a setup with 4 tiny Varta cells connected in parallel, enabling to decouple the effect of the two parameters influencing inhomogeneous behavior. This is to mimic the thermal and potential gradients occurring in large -format commercial Li -ion cells. To represent the thermal gradient, the cells are placed at different temperature and is called T-dep setup; to represent the potential gradient, the cells have different shunt resistors connected in series to each of the tiny cells in the setup and is called Vdep setup. In this work, the above setup is used to perform long-term accelerated cycling tests (about 1100 cycles under 100 % Depth of Discharge, DOD) and their State of Health (SOH) is analyzed at periodic intervals. Two different degradation phenomena are primarily observed, namely reduction and oxidation of the solvent occurring at negative and positive electrodes, respectively. The solvent reduction results in a continuous growth of a passivation layer called Solid Electrolyte Interface (SEI). The coupled electrochemical model, from our previous work, is integrated to an aging model in this work. The model is parameterized using preliminary cycle aging data performed on individual pristine cells. The model captures the experimentally observed cell capacity fade trends, in both setups, quite well. A comparison of the cell interfacial resistance increase reveals that the model captures the experimental behavior quite well until about 400 cycles and underestimates after this point. Using this validated model, a comparison of capacity fade and impedance increase, of cells in setup and individually cycled cells, reveals that the setup conditions do not necessarily aggravate the inhomogeneous aging. Further analyses show that there is a reversal of cell utilization upon cycling, meaning degradation of less aged cells seems to accelerate compared to their more aged counterparts. Additional simulation analyses under narrow DOD cycling indicate that overall setup degradation rate increases but the inhomogeneity is not aggravated compared to individually cycled cells. All in all, V-dep setup aging results only in a reduced driving mileage while T-dep setup aging results in both reduced driving mileage and acceleration/deceleration capability.

Silicon-based composite anodes continue to raise interest for their high theoretical specific capacity, but the complexity of their behaviour during battery operation presents an obstacle to both their characterization and their practical application. In this paper we present a comprehensive multiscale model of a Si-based composite anode, based on a detailed characterization and encompassing nano-, micro-, and meso-scale details. The model is used to explore the relationship between the chemo-mechanical changes in the anode components and the electrode stability during battery operation, through the prediction of the morphological evolution of the material during the lithiation process. Through the combined analysis of DFT, FEM, and DEM models we highlight the influence of Si and SiO2 lithiation on electrode swelling and damage, and the predominant influence of particle-level morphology on electrochemical behaviour.

Renewable energy sources and ways to store this energy due to its intermittency are growing exponentially. Redox flow batteries, which allow decoupling energy from power, are a promising way of electrochemical storage of electricity. Vanadium flow batteries, the current technological reference, are giving way to aqueous organic electroactive species, which present the advantages of multiple designs thanks to functionalization, lower cost, non-toxicity, and less supply issues. Their long-term performances are still compromised because of degradations of the electrodes, the membrane, or the organic species. Physical models are a good way to predict redox flow batteries behavior on long time scales and have a better understanding of the phenomena and their impact on the battery. Some degradations of the electrodes, the membrane or side reactions have been modelled, however very few models for organic active species degradations have been proposed yet. This review presents some reported degradations and their consequences for the cell components and organic electrolytes. Different existing models for aqueous organic redox flow batteries are presented, with a focus on Multiphysics models. Degradations' modelling in aqueous redox flow batteries is discussed, with existing degradations models as well as some proposals for future degradations modelling.

An empirical generic Li-ion aging model, compatible with a large number of aging mechanisms without their a priori knowledge has been developed as well as a calibration methodology allowing its fast and automated parameter setting. This model has been applied to simulate the aging behavior of a 26 Ah cell. To train this model, a large aging test campaign has been conducted dedicated to both calibration and validation purposes. This one takes into account calendar, cycling, and their combinations. Based on the design of the aging campaign it is able to account for the effect of State Of Charge, temperature and current on aging. As its calibration is based on an automated process, it can be trained automatically and does not need expert knowledge for operation. Simulation data are validated to a 2% error in comparison to experimental data and is then validated for automotive applications.

We have developed a OD model of aqueous organic redox flow battery to have a better understanding of the impact of oxygen and hydrogen evolution as a parasitic side reaction on the evolution of the battery performances. This lumped approach model is able to account for multiple redox processes at each electrode, which, to our knowledge has not been described in the literature. In this article the study is focused on alkaline battery and the model has been validated on 2,6-dihydroanthraquinone/ferrocyanide electrolytes at laboratory full cell level. The model considers the electrochemical reactions, the electrolyte flow rate, the diffusion of the electroactive molecules from the bulk to the reaction sites, the transfer of cations through a perfluorosulfonic membrane and the ohmic losses. Furthermore, the electrochemical reactions accounted for include the reduction and the oxidation of water modeled with Tafel slopes. Thanks to this approach, we highlight the non-negligible role of oxygen evolution reaction in these conditions. The model is used as a tool to optimize operating conditions as well as to predict the most advantageous potential of electrolytes to enhance performances and limit side reactions. For example, under alkaline condition (pH = 14), the negolyte standard potential can be targeted to -0.8 V without competing with HER, however, the posolyte potential must be kept below 0.65 V to avoid competition with OER. (C) 2021 Elsevier Ltd. All rights reserved.

Since the commercialization of Lithium-Ion Battery (LIB) by Sony Inc. in 1991 until today, recurrent incidents involving LIBs have been reported worldwide. During these incidents, the most energetic catastrophic failure of a LIB system is a cascading thermal runaway event. It is characterized by a deficit of energy dissipation versus energy accumulation in the cells leading to uncontrollable overheating of the battery system [1,2]. This complex event involves multi-scale phenomena ranging from internal parallel or cascading physico-chemical to battery components reactions (electrodes, electrolytes & separator) and further to the thermal propagation of cell core & safety features. Complexity of the comprehensive understanding of the thermal runaway hazard also lies in the fact that both normal operation (through aging and relating medium/long term degradation effects) and abuse conditions can contribute to a thermal runaway event, as recently discussed by [2] or [3]. Battery safety is becoming even more critical with the emergence of highly reactive Ni-rich LIBs in the market. These batteries are commercialized to meet novel energy- or power-demanding applications and are expected to dominate the market in the coming years, likely until the occurrence of a new technological breakthrough. Therefore, these newly introduced LIBs presenting such high energy density characteristics and integrating more intrinsically reactive materials could possibly lead to more catastrophic events subsequent to the thermal runaway. Therefore, there is a clear need to better understand the underlying specific electrochemical and thermal behaviors of these technologies in both normal and abuse conditions across their lifetime. Inspired by the former collaborative IFPEN/INERIS research works on the thermal runaway of LIBs (essentially focused on LFP/Graphite and relating batteries) [2], this work aims to go deeper into the understanding & modeling of this complex phenomenon at cell scale, taking into account the influence of novel highly reactive technologies and the influence of aging with 2 target degradation mechanisms: SEI growth and Li Plating, in order to understand what the keys are towards inherently safer design and operation of highly reactive LIBs. It is a matter of establishing the link between the materials used (electrodes, electrolytes) in high energy density & intrinsically reactive LIB technologies, the degradation products during cell calendar and cycling aging (mainly analyzed through SEI evolution during cell lifetime and Li deposition during cold recharges) as well as the thermal runaway kinetics. The selected technologies studied in this research are two commercial 18650 Ni-rich LIBs, namely a Panasonic NCR GA and a LG HG2, which were based on Li(Ni0.8Co0.15Al0.05)O2 (NCA) and Li(Ni0.8Mn0.1Co0.1)O2 (NMC811), respectively, for positive electrodes, in combination with graphite-SiOx composite negative electrodes. With the goal of finding the keys factors that can improve the safety of these highly reactive LIBs during usage, the research strategy relies on the achievements of the previous projects and on the synergism offered by combined experimental and modeling studies as illustrated in Figure 1. The experimental study includes the 3 interconnected experimental processes here after specified: a complete multi-scale cell analysis in order to analyze the pristine, aged and thermally abused cells; a safety-focused aging campaign in order to artificially age battery samples, focusing on each target mechanism (SEI growth, Lithium plating) in a controlled and measurable way; accelerating rate calorimetry (ARC)thermal abuse tests in quasi-adiabatic conditions at cell level in order to qualifying the thermal runaway phenomenon as well as calibrating the thermal runaway model. The modeling study leads to the development of an extended thermal runaway model in order to predict the behaviors of different LIBs nearby and during thermal runaway under field conditions. This coupled multi-physics model will improve and extend the initial thermal runaway model built by [2] by integrating the impact of Li plating & SEI-driven cycling aging. The final result will be a multi-dimensional multiphysical model of LIB capable of accounting for the triggering of runaway under different thermal and electrical conditions and as a function of the state of aging. The predictions of the models will be validated based on other thermal abuse tests. This model will further be implemented to understand the electrical or thermal initiation of the phenomenon of thermal runaway and its propagation within a battery pack regarding its design. They will eventually be transposed into tools enabling the best design of the packs and avoidance of this undesirable phenomenon. References 1. S. Abada et al, Journal of Power Sources, 306, 178–192 (2016). 2. S. Abada et al, Journal of Power Sources, 399, 264–273 (2018). 3. F. H. Gandoman et al, Applied Energy, 251, 113343 (2019). Figure 1

A fast computing electrochemical model has been developed in order to account for the electrothermal behavior of Li-ion batteries with multiple and/or multidispersed active materials in each electrode. In this study, the cell studied is a high power cell with lithium manganese spinel and lithium cobalt oxide at the positive and Lithium titanate at the negative with 2 particle populations. The model has been calibrated on the said cell and validated on realistic duty profile. It has been then compared against a state-of-the-art Newmann model that showed similar results for both global and inner behavior. However, due to the simplifications adopted for our modelling approach, calculation times of the newly developed model are significantly lower allowing to specific use where fast computing modelling approaches are required. Finally, this model has been used in order to understand the inner behavior of each electrode during constant current charge and discharges as well as hybrid electric vehicle duty cycles and further calculations have been performed to understand the impact of active material repartition in each electrode.

The main safety issue pertaining to operating lithium-ion batteries (LIBs) relates to their sensitivity to thermal runaway. This complex multiphysics phenomenon was observed in two commercial 18650 Ni-rich LIBs, namely a Panasonic NCR GA and a LG HG2, which were based on L i ( N i 0.8 C o 0.15 A l 0.05 ) O 2 (NCA) and L i ( N i 0.8 M n 0.1 C o 0.1 ) O 2 (NMC811), respectively, for positive electrodes, in combination with graphite-SiOx composite negative electrodes. At pristine state, the batteries were charged to different levels of state of charge (SOC) (100% and 50%) and were investigated through thermal abuse tests in quasi-adiabatic conditions of accelerating rate calorimetry (ARC). The results confirmed the proposed complete thermal runaway of exothermic chain reactions. The different factors impacting the thermal runaway kinetics were also studied by considering the intertwined impacts of SOC and the related properties of these highly reactive Ni-rich technologies. All tested cells started their accelerated thermal runaway stage at the same self-heating temperature rate of ~48 °C/min. Regardless of technology, cells at reduced SOC are less reactive. Regardless of SOC levels, the Panasonic NCR GA battery technology had a wider safe region than that of the LG HG2 battery. This technology also delayed the hard internal short circuit and shifted the final venting to a higher temperature. However, above this critical temperature, it exhibited the most severe irreversible self-heating stage, with the highest self-heating temperature rate over the longest duration.

Martin PETIT, Sara ABADA, Rémy MINGANT, Julien BERNARD, Philippe DESPREZ, Pietro PERLO, Marco BIASIOTTO, Riccardo INTROZZI, Amandine LECOCQ, Guy MARLAIR 1 IFP Energies Nouvelles, Electrochemistry and Materials Departement, BP3 69390 Solaize (France) 2 SAFT, 111/113 Boulevard Alfred Daney, 33074 Bordeaux (France) 3 I-FEVS, Carignano, 50/1, 10040 La Loggia Torino (Italia) 4 INERIS, Parc Technologique Alata, 60550 Verneuil en Halatte

This paper describes the way fire safety is handled in a recently EU H2020 funded 3 years on-going project federated by SAFT named DEMOBASE [1] with 10 other partners jointly working on an innovating EV concept based on a Li-ion battery pack and targeting demanding criteria of electrical vehicle emerging market in terms of cost, time to market and safety. INTRODUCTION Recent policies put in place at EU level and worldwide to favour alternative energies for transportation, responsible for a major part of greenhouse gas emissions have resulted in increasing efforts of major automotive stakeholders to promote innovative EVs. The success will rely on the promotion of new EVs no more suffering of major drawbacks of early EV generation like limited performance, high cost and -although not yet really measurable(fire) safety concerns. Fire safety has been essentially rated as an open issue so far because of the energy storage system, that is to say to the lithium-ion battery pack which is equipping currently most commercially available electric vehicles, and potentially facing the so-called thermal runaway hazard (see fig. 1). Fig. 1: underpinning phenomena in the process of thermal runaway of a li-ion cell according to chemistry (adapted from ref.[2]) In the context of the DEMOBASE project (DEsign and MOdelling for improved BAttery Safety and Efficiency) aiming at developing an innovating EV concept meeting new market demand, the 11 members of the consortium are currently jointly implementing a more holistic approach to consider safety of the battery pack in the context of its intended use in an EV: safety is indeed as a key aspect of an innovating EV, in which all parts may play a role for their inherently safer design.