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Structural Analysis of LNMO Cathode Materials using 4D-STEM ACOM and Data Science Techniques
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Degradation mechanisms analysis of perovskite solar cells and mini-modules : development of methodologies & phenomenological models
No full textPerovskite solar cells (PSC) are arguably the emerging photovoltaic technology of the decade, lately achieving lab scale efficiencies above 25% and with a potential practical limit of 39% for Perovskite/Silicon tandem configurations. However, their stability is still insufficient. Several degradation pathways have been observed in PSC under multiple stressors such as heat, light, mechanical stress, voltage bias, (and specially) moisture and oxygen, resulting in transient behaviors during current density-voltage (JV) characterization. Under real operating conditions, PSC will be exposed to multiple stressors at the same time, thus being prone to concomitant types of degradation within all layers and interfaces composing its architecture. Hence, the current thesis project aims to develop more consistent methodologies and phenomenological models to properly analyze degradation in PSC via indoor stability testing.First, a better understanding on the impact of slow ionic dynamics at buried interfaces is required. Particularly, ion redistribution and modulation of recombination at the perovskite (PK) layer can hinder charge extraction. Impedance spectroscopy (IS) is an advanced technique that allows a more deconvoluted analysis of the JV response of full devices under operating conditions. A combined JV/SunsVoc/IS (non-destructive) methodology with a multi-biasing approach was implemented, at short-circuit (Jsc) and open-circuit (Voc), for inverted (p-i-n) PSC architectures. Moreover, through drift-diffusion simulations and IS fittings to a selected equivalent circuit model, it is shown that properties such as electronic mobility and ionic concentration in the PK and the device’ shunt resistance can be extracted from the IS methodology at Jsc. Additionally, the analysis of coupled ionic effects with interfacial energetic band offsets on dominant recombination is provided at Voc, including a comparison of the derived “dark diode” ideality factor (nid) between the three techniques.In addition, inverted PSC stability was assessed using in-situ and ex-situ IS characterization coupled with ISOS stability tests. The devices were degraded under light/dark cycling (ISOS-LC-1I) and constant illumination (ISOS-L-1I), at 1 sun and at Voc load within an inner N2 environment of a climatic chamber. JV curves degradation was correlated to the IS response decomposed into resistive (R), capacitive (C) and inductive (L) elements. Likewise, the electric response was correlated with the physico-chemical stability at the PK bulk and buried interfaces quality using a wide range of complementary opto-electric, compositional and morphological techniques. Potential degradation via methylammonium iodide dimerization was linked to the formation of ionic aggregates at the PK interface with the holes selective transport layer. The aggregation dynamics result in the formation of injection barriers in degraded devices after dark relaxation. These barriers are worsened by moisture ingress, forming iodine-rich spots and inducing inductive components on IS at low frequencies under forward voltage bias conditions. A reversibility under continuous light-soaking was observed, homogenizing electroluminescence measurements and reducing the interfacial energetic barriers. The metastable behavior was correlated with s-shape transitions JV curves. Additionally, from in-situ IS analysis it is proposed that the gradual halide de-mixing under constant illumination and increase of multi-level trap-assisted recombination during ionic redistribution around Voc may enhance PSC long-term performance degradation.Les cellules solaires à pérovskite (PSC) sont la technologie photovoltaïque émergente, atteignant récemment des rendements en laboratoire supérieurs à 25% et avec une limite pratique de 39% pour les configurations tandem Pérovskite/Silicium. Cependant, leur stabilité reste insuffisante. Plusieurs voies de dégradation ont été observées sous divers facteurs tels que la chaleur, la lumière, le stress mécanique, la polarisation de tension, l'humidité et l'oxygène, entraînant des comportements transitoires lors de la caractérisation courant-tension (JV). Dans des conditions de fonctionnement réelles, les PSC seront exposés à plusieurs facteurs de stress en même temps, ce qui les rendra sujets à des types de dégradation concomitants dans toutes les couches et interfaces composant leur architecture. Par conséquent, la thèse est visée à développer des méthodologies et des modèles phénoménologiques plus cohérents pour analyser correctement la dégradation des PSC.Dans un premier temps, une meilleure compréhension de l'impact des dynamiques ioniques lentes aux interfaces enfouies est nécessaire. En particulier, la redistribution des ions et la modulation de la recombinaison dans la couche de pérovskite (PK) peuvent entraver l'extraction des charges. La spectroscopie d'impédance (IS) est une technique avancée qui permet une analyse plus décomposée de la réponse JV des dispositifs dans des conditions de fonctionnement. Une méthodologie combinée JV/SunsVoc/IS avec une approche multi-biais a été mise en œuvre, en court-circuit (Jsc) et en circuit ouvert (Voc), pour les architectures PSC inversées (p-i-n). De plus, grâce aux simulations de dérive-diffusion et aux ajustements IS à un modèle de circuit équivalent sélectionné, il est montré que des propriétés telles que la mobilité électronique et la concentration ionique dans le PK et la résistance de shunt du dispositif peuvent être extraites de la IS à Jsc. De plus, l'analyse des effets ioniques couplés avec les décalages de bande énergétique interfaciale sur la recombinaison est fournie à Voc, y compris une comparaison du facteur d'idéalité dérivé entre les trois techniques.De plus, la stabilité des PSC inversés a été évaluée en utilisant une caractérisation IS in-situ et ex-situ couplée à des tests de stabilité ISOS. Les dispositifs ont été dégradés sous des cycles lumière/obscurité (ISOS-LC-1I) et une illumination constante (ISOS-L-1I), à 1 soleil et à charge Voc dans un environnement inerte d'une enceinte climatique. La dégradation des courbes JV a été corrélée à la réponse IS décomposée en éléments résistifs (R), capacitifs (C) et inductifs (L). De même, la réponse électrique a été corrélée à la stabilité physico-chimique des interfaces enfouies et de la couche PK en utilisant des techniques complémentaires. La dégradation potentielle via la dimérisation de iodide de methylammonium a été liée à la formation d'agrégats ioniques à l'interface PK avec la couche de transport sélective des trous. La dynamique d'agrégation entraîne la formation de barrières d'injection dans les dispositifs dégradés après relaxation dans l'obscurité. Ces barrières sont aggravées par l'infiltration d'humidité, formant des points riches en iode et induisant des composants inductifs à basses fréquences. Une réversibilité sous une exposition continue à la lumière a été observée, homogénéisant les mesures d'électroluminescence et réduisant les barrières énergétiques interfaciales. Le comportement métastable a été corrélé avec les transitions des courbes JV. De plus, à partir de l'analyse IS, il est proposé que le dé-mélange graduel des halogénures sous illumination constante et l'augmentation de la recombinaison assistée par défauts multi-niveaux peuvent déclencher une dégradation supplémentaire des performances à long terme
An optimized electrically conductive Si-Fe matrix to boost the performance of Si electrodes in Li-ion Batteries
No full textInternational audienceThe development of Si-based anodes has opened the venue to increase the energy density in lithium-ion batteries (LIBs). Nonetheless, the use of Si-based electrodes usually leads to a gradual loss in the cell’s electrochemical performance due to the significant volume expansion of silicon in electrode reactions. Combining silicon, a poor electronic conductor, with an electronically conductive Li-inactive phase, is a promising strategy to alleviate the volume expansion of silicon during lithiation and delithiation while providing a robust electronic network. Si-Fe alloys are prospective candidates [1, 2, 3] which could be used to maintain the electronic network in the silicon electrodes. In this study, different Si-Fe alloys are synthesized using ball-milling (BM) and arc melting (AM) techniques, leading to highly different chemical compositions and powder morphologies to better understand the role of iron silicide inactive phases in electrochemical reactions and optimize their performance. The use of AM results in the formation of Si and α-Fe2Si5 conducting matrix in a desired ratio, as expected from the Si-Fe binary phase diagram, while BM generates a mixture of phases, including undesirable products. Thanks to the presence of the inactive iron silicide phase (α-Fe2Si5), the electrical conductivity of the Si/α-Fe2Si5 composite can be increased up to 103 S.m-1, five orders of magnitude compared to pristine Si. The electrochemical testing results show that the performance of such a composite is strongly influenced by the balance between Si and inactive iron silicide phase, as well as their interparticle contact. Dilatometry tests in full cell configuration also demonstrate the advantage of using α-Fe2Si5 as a matrix to buffer Si volume change, prevent the loss of active material, and maintain a reversible swelling of 24% throughout cycling up to the 45th cycle. After optimization of electrode and electrolyte formulations, such composites could significantly outperform current Si/C electrodes in terms of volumetric capacity, rate capability and long-term cycling
99 / 5 000Commutation d'état de spin contrôlée par la lumière et induite par solvant dans un réseau hétérobimétallique hexagonal 3D
No full textInternational audienceA cyanide bridged {4d-3d} heterobimetallic assembly of MoV-FeII with formula {[MoV(CN)8][FeII(v-im)4]2·BF4}n 2DMF·H2O (1·2DMF·H2O) was achieved by the self-assembly of [Mo(CN)8]3− and iron(II) with monodentate nitrogen donor ligand v-im (v-im = 1-Vinylimidazol). The complex was fully characterized by single-crystal X-ray diffraction analyses, spectroscopic and (photo)magnetic studies. Single crystal X-ray analyses revealed that the complex exhibits a three-dimensional (3D) hexagonal network structure of molybdenum(V) and iron(II) centers bridged by the cyanide ligands. The partially desolvated form 1·2DMF exhibit thermo-induced spin crossover (SCO) between LS Fe(II) and HS Fe(II) center over a wide range of temperature and light-controlled spin-state switching phenomenon at low temperature under light irradiation with TLIESST = 70 K whereas the fully solvated complex 1·2DMF·H2O remains in the HS state. This complex represents the first 3D coordination complex consists of iron(II) and [MoV(CN)8]3− units exhibiting reversible and complete SCO phenomenon and photo-magnetic effect.Un assemblage hétérobimétallique {4d-3d} ponté par cyanure de MoV-FeII de formule {[MoV(CN)8][FeII(v-im)4]2·BF4}n 2DMF·H2O (1·2DMF·H2O) a été obtenu par l'auto-assemblage de [Mo(CN)8]3− et de fer(II) avec un ligand donneur d'azote monodentate v-im (v-im = 1-vinylimidazol). Le complexe a été entièrement caractérisé par des analyses de diffraction des rayons X sur monocristal, des études spectroscopiques et (photo)magnétiques. Les analyses des rayons X sur monocristal ont révélé que le complexe présente une structure de réseau hexagonal tridimensionnelle (3D) de centres de molybdène(V) et de fer(II) pontés par les ligands cyanure. La forme partiellement désolvatée 1·2DMF présente un croisement de spin thermo-induit (SCO) entre le centre Fe(II) LS et le centre Fe(II) HS sur une large plage de températures et un phénomène de commutation d'état de spin contrôlé par la lumière à basse température sous irradiation lumineuse avec TLIESST = 70 K, tandis que le complexe entièrement solvaté 1·2DMF·H2O reste dans l'état HS. Ce complexe représente le premier complexe de coordination 3D composé d'unités fer(II) et [MoV(CN)8]3− présentant un phénomène SCO réversible et complet et un effet photomagnétique
Extending Si/C Anode Longevity through the Electrode Structure and Composition Design for All-Solid-State Batteries
No full textInternational audienceNumerous volume changes and sluggish kinetics causing irreversible Li-trapping and, consequently, a dramatic capacity decline during cycling are the main challenges facing Si-based anodes in all-solid-state batteries (ASSBs). The incorporation of carbon and Si significantly combats volume change and enhances electronic transport but cannot eliminate Li-trapping. Herein, we partially solve this issue by adding Li3.75Si alloy into a Si/C composite as a Li reservoir by making either a bilayer electrode or a blended electrode. We demonstrate that the bilayer electrode has superior cycling performance but suffers from soft shorting problems at high current density. This contrasts with the blended electrode, which exhibits a three-fold higher electrode critical current density (CCD), as captured from a self-designed three-electrode cell, but with limited cycling performance. In addition, we present the positive effect of adding a solid electrolyte (SE) to the blended electrode and show that ASSBs having Ni-rich cathodes and SE-containing blended negative electrode can achieve 500 stable cycles at 0.8 mA/cm2 and 183 cycles at 3 mA/cm2 due to the enhanced ionic/electronic percolations. Altogether, these results provide further insights into achieving long-lifespan, high-rate, and dendrite-free Si-based ASSBs through regulation of the electrode structure and composition
Sialyl Lewis X (sLex):Biological functions, synthetic methods and therapeutic implications
No full textInternational audienceCarbohydrates are shown to be crucial to several biological processes. They are essential mediators of cell-cell recognition processes. Among them, Sialyl Lewis X (sLe x ) is a very significant structure in the human body. It is a critical tetrasaccharide that plays a pivotal role in various biological processes, including cell adhesion, immune response, and cancer metastasis.Known as the blood group antigen, sLe x is also referred to as cluster of differentiation 15s (CD15s) or stage-specific embryonic antigen 1 (SSEA-1). sLe x is not only a prominent blood group antigen, but also involved in the attraction of sperm to the egg during fertilization, prominently displayed at the terminus of glycolipids on the cell surface. By describing the synthetic methods and biological functions of sLe x , this review underscores the importance of sLe x in both fundamental and applied sciences and its potential to impact clinical practice
Cover Feature: The ARTISTIC Battery Manufacturing Digitalization Initiative: From Fundamental Research to Industrialization (Batteries & Supercaps 1/2025)
No full textInternational audienceThe Cover Feature represents the whole ARTISTIC project workflow to optimize battery manufacturing process parameters. Synthetic data (produced by the physics-based manufacturing modeling chain) and experimental data are used to train surrogate models by using different machine learning techniques at the different manufacturing stages: mixing & slurry, coating & drying, calendering, electrolyte filling and performance. Then, optimizers, such as Bayesian, are used to determine the best input parameters to optimize output battery properties. More information can be found in the Concept by A. A. Franco and co-workers (DOI: 10.1002/batt.202400385)
Direct recycling process using Pressurized CO2 for Li-Ion battery positive electrode production scraps
No full text"ADC - Accord Couperin / American Chemical Society (2024-2026)"International audienceThis study explores a novel solvent-based delamination method that employs a mixture of triethyl phosphate (TEP), acetone, and carbon dioxide (CO2) under pressure and temperature for the efficient and fast direct recycling of positive electrode production scraps. Optimization of experimental conditions led to achieve 100% of delamination within 15 min at 120 °C and 100 bar, with a low solvent consumption of 1.5 of TEP to electrode ratio (w/w). The CO2 allows decreasing the viscosity of the TEP and acetone mixture and so increasing its diffusivity; favoring the binder dissolution and accelerating the delamination process versus other reported processes. This original approach not only enables the reduction of solvent consumption (by 6.7×), but removes the need for stirring, which is often detrimental to solvent-based approaches for scaling up the process while maintaining 100% of delamination. Subsequent to the delamination process, the active material LiNi0.6Mn0.2Co0.2O2 (NMC622) in powder form was easily and fully separated from the current collector, enabling a comprehensive characterization. A more in-depth focus on the electrochemically active material revealed that its chemical composition, crystal structure, and microstructure remained preserved throughout the recycling process. Ultimately, the electrochemical performance of the recycled NMC622 closely resembled that of the pristine NMC622, affirming the promising potential of this approach
Direct measurement of the best phase-matching conditions at 355 nm in the monoclinic Ca5(BO3)3F (CBF) nonlinear crystal
No full textInternational audienceWe determined the optimal phase-matching conditions at 355 nm in the monoclinic Ca 5 (BO 3 ) 3 F (CBF) nonlinear crystal, by recording the angular distribution of the associated conversion efficiency along the tuning curve. This was achieved using Sum Frequency Generation of two incoming wavelengths at 532 nm and 1064 nm
Développement de pérovskites de type Dion-Jacobson à dimensionnalité réduite à base de formamidinium pour des applications en cellules solaires.
No full textIn 2009, halide perovskite materials were employed for the first time in solar cells. Since then, the technology has evolved rapidly, achieving power conversion efficiencies comparable to conventional monocrystalline silicon-based photovoltaics. However, significant stability issues remain a major barrier to their industrial deployment. One promising approach to enhance stability is to introduce bulky hydrophobic organic spacer cations that create layers between the inorganic frameworks, leading to the formation of reduced-dimensional perovskites. Two main structural families are distinguished: Ruddlesden–Popper (RP) perovskites, where monoammonium cation bi-layers held by Van der Waals forces separate the inorganic slabs, and Dion–Jacobson (DJ) perovskites, where diammonium cation monolayers bridge the inorganic layers. While the organic layers improve environmental stability by acting as moisture barriers, they can hinder photogenerated carrier transport due to the quantum well structure, confining them within the inorganic planes. This thesis focuses on DJ perovskites, where the absence of Van der Waals interactions favors efficient charge transfer due to reduced interlayer spacing and improved alignment of the inorganic sheets. Firstly, a system based on butane-1,4-diammonium is optimized. Secondly, this system is compared to two analogues incorporating x-aminomethylpiperidinium (x = 3, 4). While the first system achieves higher efficiency, the last two exhibit superior stability. Thirdly, a cation quantification method using 1H NMR spectroscopy is developed to compare DJ with RP composition evolution upon annealing. We show that monoammonium cations in RP phases are largely eliminated during annealing, while most diammoniums in DJ structures are retained. As a result, RP layers tend to revert toward 3D-like compositions. Finally, a new DJ system based on 2-iodopropane-1,3-diammonium is studied. We show that due to steric hindrance leading to reduced intermolecular interactions, this diammonium is volatilized during annealing. Although this system shows lower efficiency than the 3D counterpart, it benefits from improved stability.Les matériaux pérovskites halogénées ont été utilisés pour la première fois dans des cellules solaires en 2009. Depuis, cette technologie a évolué rapidement, atteignant des rendements de conversion photovoltaïque comparables à ceux des dispositifs traditionnels à base de silicium monocristallin. Cependant, d’importants problèmes de stabilité demeurent un obstacle majeur pour leur déploiement industriel. Une approche prometteuse pour améliorer cette stabilité consisterait à introduire de gros cations organiques hydrophobes qui forment des couches entre les réseaux inorganiques, menant à la formation de pérovskites à dimensionnalité réduite. Deux grandes familles structurales sont distinguées : les pérovskites de type Ruddlesden-Popper (RP), où deux cations monoammonium séparés par des forces de Van der Waals isolent les couches inorganiques, et les pérovskites de types Dion-Jacobson (DJ), où un seul cation diammonium lie les couches. Si les couches organiques améliorent la stabilité en agissant comme barrière contre l’humidité, elles peuvent en revanche limiter le transport des porteurs de charges photo-générés à cause de la structure en puits quantique les confinant dans les plans inorganiques. Cette thèse se concentre sur les pérovskites DJ, où l’absence d’interactions de Van der Waals entre les cations organiques favorise le transfert de charge par une plus faible distance inter-couche et un alignement des feuillets inorganiques favorable. Dans un premier temps, un système basé sur le butane-1,4-diammonium a été optimisé. Dans un deuxième temps, ce système a été comparé à deux analogues intégrant des cations x-aminométhylpipéridinium (x = 3, 4). Bien que le premier système permet d’obtenir une efficacité plus élevée, les deux derniers présentent une meilleure stabilité. Dans un troisième temps, une méthode de quantification des cations par spectroscopie RMN du proton a été développée pour comparer l’évolution des compositions des DJ et RP lors du recuit. Nous montrons que les monoammoniums sont en grande partie éliminés lors du recuit, tandis que la plupart des diammoniums restent dans la couche. En conséquence, les couches RP ont tendance à avoir des compositions proches de la structure 3D. Enfin, un nouveau système DJ basé sur l’espaceur 2-iodopropane-1,3-diammonium a été étudié. Nous montrons que, en raison de l’encombrement stérique limitant ses interactions intermoléculaires, ce diammonium est également volatilisé pendant le recuit. Bien que ce système affiche une efficacité photovoltaïque inférieure à son homologue 3D, il bénéficie d’une meilleure stabilité