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Investigation of Iron Dissolution Mechanism in Acidic Solutions with and without Dissolved CO2—Part II: Time of Flight-Secondary Ion Mass Spectrometry 3D Mapping
No full textInternational audienceTime-of-flight-secondary ion mass spectrometry (ToF-SIMS) 3D mapping and depth profiling were used to study the anodic iron dissolution mechanisms of mild steel in chloride-containing aqueous CO environments. The technique detected adsorbed hydroxide and chloride intermediates formed during the corrosion process, consistent with the proposed multipath reaction mechanism for anodic iron dissolution reaction. Despite the presence of aqueous carbonic species and their observed effect on the kinetics of iron dissolution, no additional adsorbed intermediates have been detected in aqueous CO environments, indicating that carbonic species do not directly participate in the iron dissolution reaction. ToF-SIMS 3D mapping results on characterization of the specimens immersed in a chloride-containing solution with and without CO suggest that one role of aqueous carbonic species CO could be to accelerate the adsorption of chloride ions and the formation of chloride intermediates
Characterization of Li Transport through the Organic-Inorganic Interface by using Electrochemical Impedance Spectroscopy
No full textInternational audienceUnderstanding Li transport at polymer||inorganic interfaces is crucial for developing composite electrolytes in solid-state batteries. In our investigation, we employed impedance spectroscopy and established a multilayer methodology for assessing Li transport at this interface. The inorganic phase chosen was Li 6.25 Al 0.25 La 3 Zr 2 O 12 ( Al−LLZO), and the organic phase comprised a Poly(ethylene oxide) (PEO) network with dangling chains. Li incorporation in the polymer, as a free either salt or associated with anion grafting onto the PEO network, was explored. Additionally, the PEO network was either pressure-adhered to the inorganic surface (ex-situ configuration) or synthesized onto the Al−LLZO surfaces (in situ configuration) to investigate processing effects on Li transport. Using a Transmission Line Model for impedance data analysis, our study identified two key elements governing Li transport at the interface: R, representing resistance along the ionic pathway, and R and C, describing distributed resistance and capacitance within the interface. We observed that R is influenced by the polymerization process in the presence of Al−LLZO ceramic, while R remains constant regardless of the synthesis method. This suggests varying Li concentrations at the interphase in the in situ configuration, while interface/interphase heterogeneity remains consistent across configurations. The estimated activation energy indicates more energetically favorable direct Li transport in the in−situ configuration
Simulating Solid-State Battery Cathode Manufacturing via Wet-Processing with Resolved Active Material Geometries
No full textInternational audiencePrior to the development of a solid-state battery cell, researchers have limited knowledge about the microstructure of the electrodes and how they are affected by manufacturing. Therefore, numerical simulations can be considered as a powerful tool to link the fabrication process to the final microstructure of the electrode. In this paper, a numerical simulation of a wet-processed solid-state battery cathode with a formulation of 75 % LiNiMnCoO (NMC), 17.5 %LPSCl, 5 % Timcal C65 and 2.5 % Polyisobutene (PIB) is presented. From nano-computed tomography images, realistic shapes of active material particles are extracted and used in the simulation, which is well-calibrated to experimental data. In particular, we study the effects of calendering on the microstructure of the simulated cathode and deduce structure-property relations
Characterization of the Performance of Perovskite Solar Cells by Operando X-Ray Photoemission Spectroscopy
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Contrôle de la géométrie et de l'anisotropie par la combinaison des effets de coordination stérique et anionique dans les complexes Co II avec ligands N 6 -tripodaux : l'impact de la taille du ligand sur le temps de relaxation magnétique
No full textInternational audienceFour mononuclear CoII complexes of formula [Co(L)(SCN)2(CH3OH)0.5(H2O)0.5]·1.5H2O·0.75CH3OH (1), [Co(L1)Cl2]·H2O·2CH3CN (2), [Co(L1)(SCN)2]·1.5H2O·CH3OH (3) and [Co(L1)]ClO4·2CH3OH (4) were prepared from the N6-tripodal Schiff base ligands (S)P[N(Me)N[double bond, length as m-dash]C(H)2-Q]3 (L) and (S)P[N(Me)N[double bond, length as m-dash]C(H)1-ISOQ]3 (L1), where Q and ISOQ represent quinolyl and isoquinolyl moieties, respectively. In 1, the L ligand does not coordinate to the CoII ion in a tripodal manner but using a new N,N,S tridentate mode, which is due to the fact that the N6-tripodal coordination promotes a strong steric hindrance between the quinolyl moieties. However, L1 can coordinate to the CoII ions either in a tripodal manner using CoII salts with poorly coordinating anions to give 4 or in a bisbidentate fashion using CoII salt-containing medium to strongly coordinating anions to afford 2 and 3. In the case of L1, there is no steric hindrance between ISOQ moieties after coordination to the CoII ion. The CoII ion exhibits a distorted octahedral geometry for compounds 1–3, with the anions in cis positions for the former and in trans positions for the two latter compounds. Compound 4 shows an intermediate geometry between an octahedral and trigonal prism but closer to the latter one. DC magnetic properties, HFEPR and FIRMS measurements and ab initio calculations demonstrate that distorted octahedral complexes 1–3 exhibit easy-plane magnetic anisotropy (D > 0), whereas compound 4 shows large easy-axis magnetic anisotropy (D Quatre complexes mononucléaires de Co II de formule [[Co(L)(SCN) 2 (H 2 O) 0,5 (CH 3 OH) 0,5 ]•1,5H 2 O•0,75CH 3 OH (1), [Co(L1)Cl 2 ]•H 2 O•2CH 3 CN (2), [Co(L1)(SCN) 2 ]• 1,5H 2 O•CH 3 OH (3) et [Co(L1)]ClO 4 •2CH 3 OH (4) ont été préparés à partir des ligands de bases de Schiff N 6 -tripodes (S)P[N(Me)N=C(H)2-Q] 3 (L) et (S)P[N(Me)N=C(H)1-ISOQ] 3 (L1), où Q etISOQ représentent respectivement les fractions quinolyle et isoquinolyle. Dans le cas 1, le ligand L ne se coordonne pas à l'ion Co II de manière tripodale mais utilise un nouveau mode tridenté N, N, S, ce qui est dû au fait que la coordination N 6 -tripodale favorise un fort encombrement stérique entre les groupements quinolyle. Cependant, L1 peut coordonner les ions Co II soit de manière tripodale en utilisant des sels de Co II avec des anions faiblement coordonnants pour donner 4, soit de manière bisbidentate en utilisant des sels de Co II contenant des anions moyennement à fortement coordonnants pour donner 2 et 3. Dans le cas de L1, il n'y a pas d'encombrement stérique entre les groupements ISO après coordination à l'ion Co II. L'ion Co II présente une géométrie octaédrique déformée pour les composés 1 à 3, avec les anions en position cis pour le premier et en position trans pour les deux derniers. Le composé 4 présente une géométrie intermédiaire entre le prisme octaédrique et le prisme trigonal, mais plus proche de ce dernier.Les propriétés magnétiques DC, les mesures HFEPR et FIRMS et les calculs ab initio démontrent que les complexes octaédriques déformés 1-3 présentent une anisotropie magnétique dans le plan facile (D > 0), tandis que le composé 4 présente une grande anisotropie magnétique dans le plan facile (D < 0). L'analyse comparative des données magnétostructurales souligne le rôle important joué non seulement par la géométrie de coordination mais aussi par les effets électroniques dans la détermination de l'anisotropie des ions Co II. Les composés 2-3 présentent une relaxation lente de l'aimantation induite par le champ. Malgré sa grande anisotropie magnétique dans le plan facile, le composé 4 ne présente pas de relaxation lente (SMR) significative au-dessus de 2 K sous un champ magnétique appliqué nul, mais sa dilution magnétique avec Zn II déclenche une SMR à champ nul. Enfin, il convient de noter que les composés 2 à 4 présentent des temps de relaxation plus courts que les complexes analogues avec le ligand tripode portant dans ses bras des fractions pyridine au lieu d'isoquinoléine, ce qui est très probablement dû à l'augmentation de la taille moléculaire dans le premier.</div
Combining 3D printing of copper current collectors and electrophoretic deposition of electrode materials for structural lithium-ion batteries
No full textInternational audienceServing as a proof of concept, additive manufacturing and electrophoretic deposition are leveraged in this work to enable structural lithium-ion batteries with load-bearing and energy storage dual functionality. The preparation steps of a complex 3D printed copper current collector, involving the formulation of a photocurable resin formulation, as well as the vat photopolymerization process followed by a precursors-based solution soaking step and thermal post-processing are presented. Compression and microhardness testing onto the resulting 3D printed copper current collector are shown to demonstrate adequate mechanical performance. Electrophoretic deposition of graphite as a negative electrode active material and other additives was then performed onto the 3D printed copper collector, with the intention to demonstrate energy storage functionality. Half-cell electrochemical cycling of the 3D multi-material current collector/negative electrode versus lithium metal finally demonstrates that structural battery components can be successfully obtained through this approach
On the dissolution kinetics during acid pickling and Zr-based conversion coating of aluminum alloys using element-resolved electrochemistry
No full textInternational audienceThe acid pickling of Al-3at.%Mg, Al-3at.%Cu, and aluminum alloy (AA) 7449-T651 in nitrosulfuro-ferric acid was investigated using element-resolved electrochemistry (AESEC) in terms of their elemental dissolution kinetics. The influence of this acid pickling on the subsequent Zrbased conversion coating process was also demonstrated on these alloys by monitoring the dissolution rates of the alloying elements during conversion and the final elemental depth profiles from calibrated glow discharge-optical emission spectroscopy (GD-OES). The separate influence of fluoride (F -) and nitrate (NO3 -) as additives on the dissolution kinetics was also investigated when added to the conversion coating bath solution. F -increased the dissolution rate of Al but no significant effect was seen on Cu, while NO3 -enhanced the dissolution rates of both elements. Fourier-transform infrared reflection absorption spectroscopy (FT-IRRAS) data suggested a greater Zr-fluoride presence if the conversion coating was performed on a nonacid-pickled surface
Designing Strain-Less Electrode Materials: Computational Analysis of Volume Variations in Li-Ion and Na-Ion Batteries
No full textInternational audienceMechanical degradation in electrode materials during successive electrochemical cycling is critical for battery lifetime and aging properties. A common strategy to mitigate electrode mechanical degradation is to suppress the volume variation induced by Li/Na intercalation/deintercalation, thereby designing strain-less electrodes. In this study, we investigate the electrochemically-induced volume variation in layered and spinel compounds used in Li-ion and Na-ion battery electrode materials through density functional theory computations. Specifically, we propose to decompose the volume variation into electronic, ionic, and structural contributions. Based on this analysis, we suggest methods to separately influence each contribution through strategies such as chemical substitution, doping, and polymorphism. Altogether, we conclude that volume variations can be controlled by designing either mechanically hard or compact electrode materials
Machine Learning-Driven Optimization of Gas Diffusion Layer Microstructure for PEM Fuel Cells
No full textThe gas diffusion layer (GDL) is a vital component within PEMFCs, playing a crucial role in mass and heat transport. Enhancing the microstructure of the GDL directly improves transport properties, thereby leading to more efficient and durable PEMFCs. In this study, we developed a novel machine learning methodology to optimize the microstructure and properties of the GDL. The developed optimization framework, to the best of our knowledge, is the first of its kind and demonstrated high efficacy, with an R2 score ~95 % in 6 out of 7 properties and a R2 score ~90 % for the contact resistance, in identifying optimal manufacturing parameters to stochastically generate GDL microstructures and their associated properties. We validated our machine learning approach by comparing the predicted GDL properties to those calculated through digital characterization using physics-based methods from the stochastically reconstructed GDL, using the optimal manufacturing parameters identified by the optimizer. Our machine learning model was able to accurately predict 7 GDL properties with a significant decrease on the computational cost (~3 seconds wall time) compared to the physics-based calculations which takes ~3 - 4 hours wall time. In addition, the developed optimizer framework presented low fiber concentration accompanied by low compression ratio to achieve maximum diffusivity and minimum GDL-MPL contact resistance. Furthermore, prioritizing maximum electrical and/or thermal conductivities while minimizing GDL-MPL contact resistance require high fiber concentration with high compression ratio. This optimization strategy shows significant potential for improving gas transport, water management, efficient current collection, and thermal regulation within PEMFCs
Robust Epoxy Resins with Autonomous Visualization of Damaging‐Healing and Green Closed‐Loop Recycling
No full textInternational audienceAbstract Epoxy resins‐based engineering plastics are indispensable in the global economy, but they have created a serious waste crisis caused by their chemical cross‐linked networks. To solve this problem, current strategies often require the assistance of catalysts or solvents at the expense of thermal and mechanical performance. In this work, a high‐performance epoxy resin featuring dynamic ester and disulfide bonds (TDS) is reported, which exhibits higher thermal and mechanical properties than common engineering plastics, i.e., tensile strength and modulus of 66.6 MPa and 2.63 GPa, flexural strength and modulus of 103.2 MPa and 3.52 GPa, and glass transition temperature ( T g ) of 133 °C. Moreover, the reversible transformation between aromatic disulfide bonds and thiyl radicals endows TDS epoxy resin with autonomous visualization of damage and healing. In addition, the harmonious interplay between disulfide and ester bonds‐promoted by tertiary amine accelerated the topological network rearrangements, enabling TDS to easily reshape and weld. Specifically, TDS can be completely degraded in pure water at 200 °C without any catalyst, and the degraded products can be directly re‐polymerized to achieve green closed‐loop recycling. This work proposes a simple and economical strategy for the development of epoxy resin‐based cutting‐edge engineering plastics that are both functional and sustainable