Operando analysis and monitoring of lithium in Li-ion batteries using nuclear microanalysis

International audienceLithium-ion technology holds a prominent place in the battery’s area. Although its energy densities increased and the number of cycles raised as high as thousands, it still needs vast improvements to meet ever-greater demands regarding autonomy, lifespan, safety and miniaturization. Capacity fading during cycling remains a major problem limiting battery lifetime. It is therefore necessary to understand the origin of aging phenomena leading to loss of electrochemical performance in order to guide research towards new materials. For this, many in situ / operando studies have been developed (XPS, MET, NMR, XRD ...)[1]. However, none of the techniques mentioned can directly detect the lithium element, which makes the visualization and quantification of all the lithium present in an electrode or a battery impossible. Nuclear microanalysis is a technique capable of giving quantitative and qualitative information on spatial distributions of light elements such as lithium [2]. It is therefore a tool with great potential for understanding the mechanisms in lithium insertion materials. In previous ex situ studies, we showed immobilization of lithium in the LiFePO4 electrode during the first charge / discharge cycles [3]. We further developed an electrochemical cell coupled to the nuclear microprobe to perform in situ / operando analyzes[4].The cell is capable of providing electrochemical performances comparable to those obtained with conventional electrochemical cells on the first two cycles. We thus observed operando the formation of a SEI layer at the electrode / electrolyte interface and the trapping of lithium in a LiFePO4 // LiPF6 in EC-DEC // graphite assembly. The use of a liquid electrolyte creates complications for the analyses: it flows from the assembly to the cell window, rendering the interpretation of results difficult. The use of solid electrolyte in all solid-state batteries should give more information about the parasite electrochemical reaction (composition and thickness)

Why ion irradiation does not lead to the same structural changes in normal spinels ZnAl2O4, MgAl2O4 and MgCr2O4?

Expérience au GANILInternational audienceIon irradiation induced phase transformations in three normal spinel compounds MgAl2O4, MgCr2O4 and ZnAl2O4 were investigated by X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The structural and microstructural changes occurring in these three systems are described. Irradiation acts at the atomic and mesoscopic scales in different ways. At the atomic scale it produces the inversion of the cations in the structure. At the mesoscopic scale it produces a change of the size of the diffracting domains, responsible for the colossal changes in the observed X-ray diffraction patterns

Operando analysis and monitoring of lithium in Li-ion batteries using nuclear microanalysis

International audienceLithium-ion technology holds a prominent place in the battery’s area. Although its energy densities increased and the number of cycles raised as high as thousands, it still needs vast improvements to meet ever-greater demands regarding autonomy, lifespan, safety and miniaturization. Capacity fading during cycling remains a major problem limiting battery lifetime. It is therefore necessary to understand the origin of aging phenomena leading to loss of electrochemical performance in order to guide research towards new materials. For this, many in situ / operando studies have been developed (XPS, MET, NMR, XRD ...)[1]. However, none of the techniques mentioned can directly detect the lithium element, which makes the visualization and quantification of all the lithium present in an electrode or a battery impossible. Nuclear microanalysis is a technique capable of giving quantitative and qualitative information on spatial distributions of light elements such as lithium [2]. It is therefore a tool with great potential for understanding the mechanisms in lithium insertion materials. In previous ex situ studies, we showed immobilization of lithium in the LiFePO4 electrode during the first charge / discharge cycles [3]. We further developed an electrochemical cell coupled to the nuclear microprobe to perform in situ / operando analyzes[4].The cell is capable of providing electrochemical performances comparable to those obtained with conventional electrochemical cells on the first two cycles. We thus observed operando the formation of a SEI layer at the electrode / electrolyte interface and the trapping of lithium in a LiFePO4 // LiPF6 in EC-DEC // graphite assembly. The use of a liquid electrolyte creates complications for the analyses: it flows from the assembly to the cell window, rendering the interpretation of results difficult. The use of solid electrolyte in all solid-state batteries should give more information about the parasite electrochemical reaction (composition and thickness)

Microstructural Characterization of the Radiation Effects in ZrC, a Potential Material for Next Generation Nuclear Plants

International audienceThe development of a new generation of nuclear reactors (Gen-IV), with improved thermodynamic yield and a reduction of waste production, makes necessary to consider materials able to withstand high operating temperatures. Transition metal carbides, like ZrC, are then under consideration. Despite their good thermal and neutron properties, they have unfortunately a brittle mechanical behaviour. This is the reason why it is important to investigate the properties of these systems with sub-micrometric grains and as a function of their composition. Therefore, samples having micrometric and nanometric grain sizes (and different oxygen content) were irradiated by low energy ions at room temperature to simulate their behaviour in a neutron flux. The irradiation effects in these materials were studied by grazing X-ray diffraction and transmission electron microscopy

Multiscale characterizations of proton conduction in La1.95Sr0.05Zr2O7-d electrolyte for protonic ceramic fuel cells

International audienceThe pyrochlore structure materials have attracted much attention for solid electrolyte fuel cells, which may be served as mixed ionic-electronic conductors for anode materials or proton conductors for electrolyte materials. Their mechanism for ionic conductivity is based on the presence of oxygen deficiency. Moreover, it is possible to induce interesting protonic conduction under wet atmosphere. A multi-scale approach was used in this study to characterize the doped La1,95Sr0,05Zr2O7-d. The hydrogen profile was established by nuclear microanalysis and the diffusion coefficient was estimated from impedance spectroscopy measurement

A Chromium Terephthalate-Based Solid with Unusually Large Pore Volumes and Surface Area

International audienceWe combined targeted chemistry and computational design to create a crystal structure for porous chromium terephthalate, MIL-101, with very large pore sizes and surface area. Its zeotype cubic structure has a giant cell volume (È702,000 cubic angstroms), a hierarchy of extra-large pore sizes (È30 to 34 angstroms), and a Langmuir surface area for N 2 of È5900 T 300 square meters per gram. Beside the usual properties of porous compounds, this solid has potential as a nanomold for monodisperse nanomaterials, as illustrated here by the incorporation of Keggin polyanions within the cages

Defect thermodynamic and transport properties of nanocrystalline Gd-Doped ceria

International audienceNanocrystalline CeO2-doped (5, 7.5, 10, and 15 mol%) Gd2O3 powders, with a particle size of about 17 nm, were synthesized through the combustion of glycine/nitrate gels. Dense nanocrystalline materials were obtained by hot uniaxial sintering. Optical microscopy, scanning electron microscopy and transmission electron microscopy examinations, as well as X-ray diffraction analyses, have allowed us to characterize these polycrystals. The grain sizes, included between ∼10 and 80 nm, depend on both the sintering temperature and the amount of dopant. A comparison of the transport properties of these nanocrystalline samples to the values obtained with coarsened grained materials of same composition shows that the ionic conductivity passes through a maximum for mean grain sizes included between 300 and 500 nm. Furthermore, an enhancement of the ionic conductivity is observed when the amount of dopant increases. This was attributed to a grain-size-dependent gadolinium segregation at the periphery of the grains confirmed by X-ray photoelectron spectroscopy characterizations