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Investigation of the lithium extraction mechanism from LiNi0.6Mn0.2Co0.2O2 by using operando neutron diffraction in an all-solid-state battery
No full textInternational audienceAll‐Solid‐State Batteries (ASSBs) are promising emerging devices for meeting high‐energy demands and an in‐depth understanding of the reaction mechanisms occuring during their operation will help in their design for better performance. In this context, neutrons, with their high penetration depth and sensitivity to light elements such as lithium, provide a powerful tool for investigating the structural mechanisms occurring in bulk ASSBs, while the electrochemical operation of large batteries (required for neutron diffraction) remains a challenge. In this study, we demonstrate the reversible electrochemical Li + extraction/insertion within a 2.5 mm thick ASSB system comprising 140 mg of LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) as the positive electrode material (238 mWh energy density), Li 5.4 PS 4.4 BrCl 0.6 (LPSClBr) as the solid electrolyte and Li 0.5 In as the negative electrode. Thanks to the use of the newly‐designed ILLBAT#5 electrochemical cell, we were able to perform operando neutron powder diffraction (NPD) of the system, which coupled with ex situ diffraction, allowed us to gain valuable insights into the structural evolution of NMC622 within the ASSB as well as to probe the structural stability of the Argyrodite solid electrolyte throughout the initial cycle. Herein, we report on the formation and the co‐existence of H1‐H2 phases in NMC622, attributed to system inhomogeneity
Molecule-driven control of the magnetic anisotropy of surface-functionalized maghemite nanoparticles
No full textInternational audienceUsing cobalt(II) complexes and a simple coordination reaction at the surface of maghemite nanoparticles, a molecule-driven control of the effective magnetic anisotropy can be achieved. This functionalisation strategy is explored for nanoparticles ranging from 4 to 8 nm and performed in soft conditions and aqueous media. It preserves colloidal stability and permits an acute control of the magnetic properties with an increase of the blocking temperature and of the coercive field values. This effect is correlated to the quantity of complexes coordinated at the surface and the increase of the surface anisotropy of the nanoparticles. Magnetometry studies show that the effective magnetic anisotropy constant, Keff, can be modulated from 32 to 168 kJ.m -3 , and with a few kJ.m -3 accuracy
Assessing Mesoscale Heterogeneities in Hard Carbon Electrodes through FIB-SEM Characterization, Manufacturing and Electrochemical Modeling
No full textInternational audienceGiven 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. Preprint on ChemRxiv, 45 pages
Cyanide cubic cages: soluble molecular counterparts of prussian blue analogues
No full textInternational audienceHerein, we present a comprehensive review focusing on cyanide-bridged cubic complexes that have emerged over the last years as soluble molecular models of the well-known three-dimensional Prussian Blue Analogues (PBAs). We first describe the synthetic strategies and highlight the peculiarities of molecular cubes in comparison to the inorganic polymeric PBAs. Then, we review solution studies carried out with these soluble counterparts of PBAs, considering in particular supramolecular aspects. We also summarize efforts to transfer the original properties of PBAs to cubic complexes by highlighting both their similarities and specificities. Furthermore, outstanding electronic properties such as the access of multiple electronic states resulting in multiple bands electrochromism, or the stimuli-induced switching of electronic states associated with a change in physical properties are surveyed. Finally, recent attempts at surface deposition of functional molecular cubes or their integration into devices are presented
Mo-enhanced passivity of stainless steels studied at metal/oxide interfaces by DFT atomistic modeling
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Opposite enantioselectivities displayed by supramolecular helical catalysts with non-enantiomeric “sergeants”
No full textInternational audienceTriarylamine trisamide (TATA) coassemblies composed of one achiral phosphine-based monomer and one chiral monomer, as the “soldier” and “sergeant” respectively, were found to adopt opposite handednesses and favour enantiomers of a catalytic product with “sergeants” bearing (S) stereogenic centres placed either in alpha or in gamma positions on their side chains
Identifying phase transitions in zeolitic imidazolate frameworks: microscopic insight from molecular simulations
No full textInternational audienceMetal–organic frameworks (MOFs) feature a rich structural diversity, including crystalline, amorphous, and liquid phases of varying topologies. Their structural characterization is often performed either at the local scale (through pair distribution functions, bond angle distributions, etc.) or, for crystalline phases, through topology analysis of the periodic framework—leaving out disordered and amorphous phases. In this work, we develop a computational methodology for the structural characterization of middle-range order in MOFs that is applicable to both crystalline and amorphous phases. We base our method on the statistical analysis of the geometry of the supramolecular framework at the microscopic level, and its evolution during molecular simulation. We analyze the statistics of metal–organic rings, their distribution in size, as well as their geometrical characteristics through mathematical tools derived from polymer physics: radius of gyration, asphericity, and writhe. We show that this advanced characterization can be leveraged for the identification of phases and the detection and analysis of phase transitions
Ca5(BO3)3F (CBF) nonlinear properties for third harmonic generation at 355 nm
No full textInternational audienceAngular, thermal acceptances and conversion efficiency of CBF crystals oriented in the XY and YZ planes for THG at 355nm were investigated. YZ direction exhibits 6 times the acceptance of LBO for UV generation
A simple and cost-effective thiophene–benzene–thiophene-based hole transporting material for stable perovskite solar cells
No full textInternational audienceSide-chain engineering modulates interfacial energetics and passivation in low-cost hole-transport materials; NS-2 enables efficient charge extraction, suppressed recombination and stable perovskite solar cells with 17.5% efficiency
Tracking element-specific dissolution during pitting corrosion: an operando ICP-AES–electrochemical study of the CoCrFeMnNi Cantor alloy
No full textInternational audienceIn this work, a flow-through electrochemical–ICP-AES platform for operando monitoring of pitting corrosion on the CoCrFeMnNi high-entropy alloy is introduced. This setup combines localized chloride injection, potentiostatic control, and online, element-resolved dissolution analysis, thereby addressing a long-standing gap in mechanistic studies of early pit initiation and repassivation. Experiments in 0.5 M H 2 SO 4 with Cl - injection enabled the continuous transfer of dissolved species from the electrode surface to the ICP-AES detector, achieving sub-ppb sensitivity and allowing quantification of Co, Cr, Fe, Mn, and Ni dissolution rates during the pitting process. The results reveal four characteristic stages, namely, incubation, initiation, propagation, and repassivation, with subtle but systematic differences between alloying elements. Co and Fe contribute slightly more during initiation, while Cr plays a dominant role during repassivation, reflecting its critical involvement in passive film regeneration. Charge analysis demonstrates that repassivation consumes a quantity of charge far greater than expected for compact passive films, pointing instead to a slow, iterative re-formation and partial dissolution of hydrated oxides. This methodology provides new mechanistic insight into the dynamic sequence of film breakdown, localized dissolution, and film repair in multicomponent alloys, and establishes a versatile framework for studying localized corrosion processes with element-specific resolution