An Auger and XPS survey of cerium active corrosion protection for AA2024-T3 aluminum alloy

XPS evidenced the proximity of the inhibitor with the surface AA2024 alloy.Cerium conversion coatings with [Ce] = 0.1 M offer the best corrosion resistance. SAM shown the migration of Ce + III entities towards the corrosion pits or crevices. High resolution analyses (Auger) connecting the nano-scale order with the chemical distribution

Cross-section nano-Auger/SEM analysis to reveal bulk chemical/morphological properties of composites for energy storage

International audienceComposite materials for energy storage such as powders, electrodes or battery stack often require probing their bulk chemical/morphological properties, which remains challenging so far with conventional analytical methods. In this work, Ar + milling cross-section is proposed to reveal the intrinsically buried bulk information of three different composites without physical/chemical change. Then, nano-Auger/scanning electron microscopy (SEM) analysis is proposed to investigate their bulk properties at both micro-and nano-scales. For MnCo-based powders with micrometric particles, it allowed revealing the bulk porosity and the bulk nano-or micro-Mn/Co distribution. For micrometer thick TiSnSb-based electrodes, it allowed proving the conversion reaction over long term cycling (i.e. the participation of the electrochemically inactive Ti) while revealing the TiSnSb particles morphological evolution (shell to core spreading/pulverization into porous structure) and SEI formation inside the porous TiSnSb. For PEO-based solid battery stacks, the cross-section allowed revealing well-defined interfaces so that reliable interfaces analysis can thus be perform. Advantage/limitation of this cross-section nano-Auger/SEM approach are also discussed. Overall, this work opens the door for future development of Ar + milling cross-section and Auger analysis as powerful tools to reveal/study buried chemical/morphological properties at micro-and nano-scales even beyond the energy storage field

Methodological developments to expose and analyse buried interfaces in lithium solid-state batteries using

Lithium solid-state batteries (SSBs) are a promising technology for electrochemical energy storage systems. So far, the performance of SSBs are mainly governed by the electro-chemo-mechanical properties of the diverse solid/solid interfaces and their evolution upon cycling. However, as these interfaces are buried in the battery stack, their comprehensive understanding remains a challenge. Here, we thus provide some advances in methodological developments for ex situ, in situ and operando cycling/analysis of these buried interfaces. It is showed that noble gaz ion milling at liquid nitrogen temperature is a suitable and reproducible method to prepare cross-section without any chemical/physical change even for polymer-based SSBs. In addition, innovative operando cycling using Auger analysis was proposed for the first time on a model Li/Li6PS5Cl stack. The interest of this approach is to be able to proceed without a dedicated electrochemical cell and to use the fully adjustable electron beam of the auger to create a surface potential difference followed by lithium migration then SEI (Solid Electrolyte Interface) formation and Li plating. Overall, this work should greatly benefits to all researchers working on buried interfaces study in lithium solid-state batteries

Operando Auger/XPS using an electron beam to reveal the dynamics/morphology of Li plating and interphase formation in solid-state batteries

International audienceInterfaces and their understanding/control are the key to pave the way for the development of solid-state batteries. This work focuses on the development of operando Auger cycling using an electron beam to investigate the Li/solid electrolyte (SE) interphases. To do so, the fully tunable electron gun of the Auger was applied on top of a model Li/Li6PS5Cl(Arg) stack, allowing charge build up at the Arg surface and Li+ migration from the lithium electrode followed by SE interphase formation and Li plating. Overall, it is found that (i) Li6PS5Cl is first reduced to Li2S, LiCl and Li3P while (ii) Li plating occurs almost concomitantly and (iii) proceeds until the end of the operando cycling. These results were then confirmed by operando XPS using an electron beam. Importantly, this study highlights that operando Auger is more powerful than operando XPS as it provides visual observation of the dynamics/morphology of both Li/solid electrolyte interphase formation and Li plating together with reliable chemical information. This study thus opens the door for future development of operando Auger cycling using an electron beam as a powerful approach to better understand the interfaces in solid-state batteries

Hybrid spiropyran-silica nanoparticles with a core-shell structure: Sol-gel synthesis and photochromic properties

International audiencePhotochromic hybrid spiropyran-silica nanoparticles with a core-shell structure were synthesized via a two step sol-gel procedure using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) as silica precursors. The chemical nature and porosity of the materials were modified by the precursor ratio and the silylated spiropyran derivative chromophore was grafted and confined inside the nanoporous shell producing photoresponsive nanomaterials with a tunable dye photochromic response. When the MTEOS content increases in the matrices, the optical response was tuned from reverse to direct photochromism. Thermal bleaching after UV irradiation exhibits a blue shift of the reflectance maximum in the visible region assuming a modification of the dye populations towards open forms stabilized in more polar environments. The kinetic data were finally studied through a Gaussian model to evaluate the decay rates and to give an indication of the degree of heterogeneity of the materials

New insights into micro/nanoscale combined probes (nanoAuger, μxPS) to characterize Ag/Au@SiO2core-shell assemblies

International audienceThis work has examined the elemental distribution and local morphology at the nanoscale of core@shell Ag/Au@SiO2particles. The characterization of such complex metal/insulator materials becomes more efficient when using an initial cross-section method of preparation of the core@shell nanoparticles (ion milling cross polisher). The originality of this route of preparation allows one to obtain undamaged, well-defined and planar layers of cross-cut nano-objects. Once combined with high-resolution techniques of characterization (XPS, Auger and SEM), the process appears as a powerful way to minimize charging effects and enhance the outcoming electron signal (potentially affected by the topography of the material) during analysis. SEM experiments have unambiguously revealed the hollow-morphology of the metal core, while Auger spectroscopy observations showed chemical heterogeneity within the particles (as silver and gold are randomly found in the core ring). To our knowledge, this is the first time that Auger nano probe spectroscopy has been used and successfully optimized for the study of some complex metal/inorganic interfaces at such a high degree of resolution (≈12 nm). Complementarily, XPS Au 4f and Ag 3d peaks were finally detected attesting the possibility of access to the whole chemistry of such nanostructured assemblies

How carbon coating or continuous carbon pitch matrix influence the silicon electrode/electrolyte interface sand the performance in Li‐ion batteries

International audienceThe Si surface coating by carbon is an appealing strategy to improve both theelectronic conductivity and to stabilize the solid electrolyte interphase (SEI).In the present study, the electrochemical performance comparison of threenanocrystalline silicon‐based electrodes confirms the advantage brought bythe carbon presence either as coating or in a composite, to improve theirperformance in Li‐ion batteries (LIBs). To rationalize this behavior, a fullstudy of the electrode/electrolyte interface was achieved through the analysisof the cumulated relative irreversible capacity and the impedance and X‐rayphotoelectron spectroscopies measurements. The study highlighted that thecarbon coating leads to more efficient and less resistive SEI than that formedon silicon or on the native oxide surface. The pitch carbon matrix offers thesame advantages and avoids moreover the isolation of particles. The control ofthe Si/electrolyte interface has a crucial role in the performance of Si‐basedelectrodes as negative electrodes for LIB

Surface Amalgam on Magnesium Electrode: Protective Coating or Not?

International audienceA better control of the metal–electrolyte interface is mandatory to help the development of rechargeable magnesium batteries. Protecting the magnesium surface by a coating layer to avoid its passivation with conventional liquid electrolytes is a promising strategy. Herein, in contact with a mercury droplet, a crystalline amalgam layer is created on the surface of magnesium. After the creation of this surface coating, a remarkable improvement of the plating/stripping process is observed with magnesium bis(trifluoromethanesulfonyl)imide/dimethoxyethane electrolyte, whereas strong surface passivation hindering electrochemical cycling occurs when using bare magnesium. The detailed investigation of the evolution of the amalgam layer during cycling, however, shows substantial chemical and morphological electrochemical changes, eventually showing that such a layer does not act as a protecting coating, but rather as an independent electrode material deposited on an inert Mg substrat

Cross-Section Auger/XPS Imaging of Conversion Type Electrodes: How Their Morphological Evolution Controls the Performance in Li-Ion Batteries

International audienceConversion type reactions have revolutionized the field of Li-ion batteries and beyond in terms of electrochemical performance and fundamental aspects. However, direct evidence of this reaction over long-term cycling still has to be demonstrated. Indeed, investigating the morphological conversion mechanism at both the electrode and nanometer scales remains very challenging. Here, the use of advanced Auger/μXPS imaging of electrode cross-sections, prepared by ion-milling, is proposed. Through the study of TiSnSb-based electrodes, the role of the inactive element (here Ti) in the long-term reversibility of the conversion reaction is highlighted. Importantly, Ti, Sn, and Sb are found together at the nanometer scale despite a total spreading over tens of microns which directly proves the electrochemical conversion of the TiSnSb material even after 400 cycles. Moreover, a gradual shell to core expansion/break-up of TiSnSb particles is revealed during the continuous conversion reactions and leads to highly porous structures after 400 cycles. This phenomenon, more uniform at 60 °C, is at the origin of the higher electrochemical performance at this temperature. Overall, the innovative approach proposed in this work will benefit the the study of not only conversion/alloy-based batteries but also all-solid-state batteries for which buried interfaces have to be reached

Silicon-based electrodes formulation in buffered solution for enhanced electrode-electrolyte interfaces

International audienceSilicon nanoparticles based composite electrodes for Li-ion batteries reach high specific capacities and enhance cyclability compared with larger silicon particles. Such electrodes are foreseen for the next generation Li-ion batteries (LiB). Playing on binder and conductive additives in the formulation of the Si based electrodes is a well-known strategy to to enhance performance. Aqueous electrode formulations using the carboxymethyl cellulose as environmentally friendly binder has already showed great cyclability enhancements, especially when employed in acidic conditions. In this study, pH = 1, 3 and 7 buffered solutions were studied as solvent to prepare the Si/C/CMC composite electrodes. The influence of the formulation pH on the electrode components interactions were followed through a combined ATR-FTIR / XPS experiment and discussed in relation with the electrode electrochemical performance. Interestingly, the pH=7 buffered solution show increased capacity retention and coulombic efficiency during 100 cycles compared with the electrode obtained in acidic conditions. Post mortem analysis and EIS study highlighted differences of electrode/current collector (CC) adhesion and SEI deposition