International audienceSafety issues pertaining to Li-ion batteries justify intensive testing all along their value chain. However, progress in scientific knowledge regarding lithium based battery failure modes, as well as remarkable technologic breakthroughs in computing science, now allow for development and use of prediction tools to assist designers in developing safer batteries. Subsequently, this paper offers a review of significant modeling works performed in the area with a focus on the characterization of the thermal runaway hazard and their relating triggering events. Progress made in models aiming at integrating battery ageing effect and related physics is also discussed, as well as the strong interaction with modeling-focused use of testing, and the main achievements obtained towards marketing safer systems. Current limitations and new challenges or opportunities that are expected to shape future modeling activity are also put in perspective. According to market trends, it is anticipated that safety may still act as a restraint in the search for acceptable compromise with overall performance and cost of lithium-ion based and post lithium-ion rechargeable batteries of the future. In that context, high-throughput prediction tools capable of screening adequate new components properties allowing access to both functional and safety related aspects are highly desirable

International audienceDerived from the Pseudo Two-Dimensional mathematical structure, a simplified electrochemical and thermal model of LiFePO4-graphite based Li-ion batteries is developed in this paper. Embedding the porous electrode theory, this model integrates the main design parameters of Li-ion systems and its partial differential equations mathematical structure makes it a promising candidate for battery management system (BMS) applications and comprehensive aging investigations. Based on a modified Single-Particle approach, the model is used to simulate and discuss capacity restitution in galvanostatic charges and discharges at various rates and temperatures. Constant high-rate solicitations similar to fast charge of plug-in electric vehicles or electric vehicles, are experimentally tested and simulated with the present model. Also, thermal issues occurring during these specific operating conditions are quantitatively pointed out. The concept of current-dependent spherical particle radius is used to obtain good agreement with experimental data related to galvanostatic charges and discharges. The capabilities and limits of this preliminary modeling work are discussed in detail and ways to extend the potentialities of this approach to BMS applications are proposed

International audienceIn this paper, an isothermal physics-based agingmodel from the literature is modified and extended to simulate both capacity and power fade of a commercial LiFePO4-graphite Li-ion battery. Compared to the isothermal reference, themechanism of porosity modification due to the Solid Electrolyte Interphase (SEI) film growth at the negative electrode is integrated in the present electrochemical and thermalmodel to establish theoretical correlations between capacity and power fade of the system. The agingmodel includes different contributions of the cell impedance increase such as the SEI film resistance and the electrolyte mass transport resistance due to the mitigation of the negative electrode porosity. Experimental databases from literature and specific experiments coupling endurance tests and Electrochemical Impedance Spectroscopy results, are used to calibrate and validate the correlated power and capacity loss simulations for both calendar and classic galvanostatic cycling operating conditions. The analysis of the experimental data points out that an additional possible aging mechanism such as cracking and fracture of the SEI layer could play an important role for cycling operating conditions and accelerate the electrochemical mechanisms. The impact of physical and design parameters on the power and capacity theoretical correlations are discussed. The limits of applicability of the present model are also discussed in this paper

ln this paper an empirical capacity fade model for Li-ion batteries has been developed, calibrated and validated for a NCA/C and a LFP/C Li-ion cell. Based on extensive experimental work, it is able to describe both cycle and calendar effects on aging. The stress factors taken into account for each aging mode are the state of charge and the tempe rature for calendar aging, and the temperature and the current for cycle aging. A simple approach has been adopted in order to instantaneously apply either cycle aging or calendar aging according to operating conditions and th us accurately mode! aging effects due to dynamic operating conditions. This model has then been coupled to an electrothermal mode l and integrated in a system simulation software application in order to assess the effect of charging strategies and V2G on battery lifetime. When compared, LFP/C and NCA/C exhibited different behaviors when submitted to V2G scenarios. Light V2G scenarios led to a low aging for LFP/C based battery but tended to slightly increase the aging of NCA/C based battery according to simulations.

Li-ion secondary rechargeable batteries are becoming the preferred solution to store energy on board of new generation electric and hybrid vehicles or manage renewable energy in stationary applications. However, Li-ion batteries (LIBs) are still suffering limited lifetime, high cost and significant safety issues increasing their time to mass market. Thermal runaway is still nowadays considered as a major hazard of LIBs. This multiscale and multistep phenomenon originating at the microscale level potentially leads to uncontrolled fire and explosion of the battery. This work is focused on the development and validation of a 3D physical model of the LIB electro-thermal behavior nearby thermal runaway conditions. A combined modeling and experimental investigation provides a better understanding of the mechanisms leading to thermal runaway of LIBs, and of the ageing influence on this process. One major outcome of this work is also the proven fact that calendar ageing leads to a delayed onset of the cell self-heating temperature with a thermal runaway starting at a lower temperature. This is supported by computer simulations showing that the thickening of the solid electrolyte interface (SEI) hinders the diffusion of Li ions, which delays the degradation of the negative electrode and the occurrence of thermal runaway. HIGHLIGHTS  Development of an original 3D thermal runaway model including calendar ageing.  Model includes 3D thermal, 3D chemical reaction, and 0D calendar ageing sub-models. Calibration of the model for cylindrical 26650 LFP/C cells using a BTC. Validation of the model for fresh as well as 10% and 30% aged cells in oven tests.  Fresh and aged cells are compared in terms of critical temperatures under overheating 2

Polymer coating systems are classically applied on a metal surface to provide a dense barrier against the corrosive species. Cathodic protection is used for many applications at the same time than coatings to protect the metal structures from corrosive attack when the coating is damaged. However, the current demand will increase with the disbonded areas; moreover, the reactions that take place at the cathode can cause a progressive enlargement of the unbonded area. Self-healing coatings were considered as an alternative route for efficient anticorrosion protection while maintaining a low demand in cathodic protection. Such coatings typically incorporate micro or nanocapsules that contain film-formers and repair the coating damage when the coating is scratched. Selfhealing systems were developed for metal structures under cathodic protection using specific-film formers sensitive to the electrical field and pH encountered in the vicinity of a default on a coated structure under cathodic protection. The present paper describes the principle of this novel self-healing concept and discusses the healing efficiency on the basis of laboratory results. Electrochemical Impedance Spectroscopy was used to evaluate the performance of the barrier efficiency and continuous current demand monitoring assessed the ability of specific film-formers to provide self-healing and repair defects generated through the coating to the metal.

This study is concerned with the development of a tool to predict the long term behaviour of adhesively bonded steel joints aged in sea water. First, diffusion kinetics and the mechanisms governing the degradation of mechanical properties of an epoxy adhesive are described. These two sets of data were used in a coupled finite element (FE) analysis to determine the stress state in double lap shear (DLS) specimens before and after aging. However, subsequent tests on DLS specimens indicated an adhesive and not cohesive failure mode, so this approach could not be used to predict failure in the present case without introducing an interfacial damage parameter. A second approach was therefore employed, in which modified Arcan samples were designed in order to identify directly how the failure envelope changed with aging. Tests were performed on these modified Arcan specimens under shear, tensile/shear and tensile loads before and after aging. The results from these tests have enabled a tension-shear failure envelope to be constructed, which may be used to predict failure in joints with more complex stress states. The application of a coupled diffusion-mechanical property approach is illustrated for the Arcan specimen loaded in tension, and its application to the prediction of failure behaviour after aging is discussed.

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