Publications by authors named "Dany Carlier"

We report on single-phase NaV(PO) compositions (1.5 ≤ x ≤ 2.5) of the Na super ionic conductor type, obtained from a straightforward synthesis route.

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In our recent study, we demonstrated using Li solid-state Nuclear Magnetic Resonance (ssNMR) and single-crystal X-ray diffraction that the cathode LiFeVO possesses a defect associated with the positioning of vanadium atoms. We proposed that this defect could be the source of extra signals detected in the Li spectra. In this context, we now apply density functional theory (DFT) calculations to assign the experimental signals observed in Li NMR spectra of the pristine sample.

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In the last years, disordered rocksalt structure (DRS) materials were proposed as a positive electrode for lithium-ion batteries. In particular, the fluorinated DRS materials were proposed to be more stable upon cycling than pure oxide counterparts. These materials are mainly obtained by mechanosynthesis in order to incorporate a significant number of F ions and maintain a disordered structure.

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Among candidates at the positive electrode of the next generation of Li-ion technology and even beyond post Li-ion technology as all-solid-state batteries, spinel LiNiMnO (LNMO) is one of the favorites. Nevertheless, before its integration into commercial systems, challenges still remain to be tackled, especially the stabilization of interfaces with the electrolyte (liquid or solid) at high voltage. In this work, a simple, fast, and cheap process is used to prepare a homogeneous coating of AlO type to modify the surface of the spinel LNMO: the supercritical fluid chemical deposition (SFCD) route.

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NaV(PO)FO is a promising candidate for practical use as a positive electrode material in Na-ion batteries thanks to its high voltage and excellent structural stability upon cycling. However, its limited intrinsic transport properties limit its performance at fast charge/discharge rates. In this work, two efficient approaches are presented to optimize the electrical conductivity of the electrode material: particle nanosizing and particle coating with an ionic liquid (IL).

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Sodium-rich iron hexacyanoferrates were prepared by coprecipitation, hydrothermal route, and under reflux, with or without dehydration. They were obtained with different structures described in cubic, orthorhombic, or rhombohedral symmetry, with variable compositions in sodium, water, and cationic vacancies and with a variety of morphologies. This series of sodium-rich Prussian blue analogues allowed addressing the relationship between synthesis conditions, composition, structure, morphology, and electrochemical properties in Na-ion batteries.

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The reaction between P2-type honeycomb layered oxides NaNiTeO and KNiTeO enables the formation of NaKNiTeO. The compound is characterized by X-ray diffraction and Na solid-state nuclear magnetic resonance spectroscopy, and the structure is discussed through density functional theory calculations. In addition to the honeycomb Ni/Te cationic ordering, NaKNiTeO exhibits a unique example of alternation of sodium and potassium layers instead of a random alkali-mixed occupancy.

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Polyanionic NaV(PO)FO has been successfully prepared for the first time by ionothermal reaction in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) ionic liquid. Its structure and elemental stoichiometry are confirmed by X-ray diffraction, NMR spectroscopy, and ICP-OES, respectively. Furthermore, the scanning electron microscopy reveals that the as-obtained material possesses an original platelet-like morphology.

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Li, P, and F solid-state nuclear magnetic resonance (NMR) spectroscopy was used to investigate the local arrangement of oxygen and fluorine in LiVPO F O materials, interesting as positive electrode materials for Li-ion batteries. From the evolution of the 1D spectra versus y, 2D Li radiofrequency-driven recoupling (RFDR) experiments combined, and a tentative signal assignment based on density functional theory (DFT) calculations, it appears that F and O are not randomly dispersed on the bridging X position between two X-VO -X octahedra (X = O or F) but tend to segregate at a local scale. Using DFT calculations, we analyzed the impact of the different local environments on the local electronic structure.

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The OP4-(Li/Na)CoO phase is an unusual lamellar oxide with a 1:1 alternation between Li and Na interslab spaces. In order to probe the local structure, electronic structure, and dynamics, Li and Na magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy was performed in complementarity to X-ray diffraction and electronic and magnetic properties measurements. Li MAS NMR showed that NMR shifts result from two contributions: the Fermi contact and the Knight shifts due to the presence of both localized and delocalized electrons, which is really unusual.

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NaMoO was synthesized as a layered oxide from the reaction between the layered oxide NaMoO and metal sodium. Its structure was determined from high-resolution powder X-ray diffraction, and it can be described as an α-NaFeO distorted structure in which sodium ions and molybdenum atoms occupy octahedral interstitial sites. Chains of "diamond-like" clusters of molybdenum were evidenced in the [MoO] layers resulting from the Peierls distortion expected in a two-dimensional triangular lattice formed by transition metal atoms with a d electronic configuration.

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We prepared Al-doped LCO (LCA) powders with low Al content (4%) with a controlled Li/(Co + Al) stoichiometry by a solid-state reaction using LiCO and two types of Co/Al precursors: simply mixed (CoO and AlO) or heat-treated (CoO and AlO). These samples were thereby used to propose a reliable protocol with the aim to discuss the homogeneity of the Al doping for LiCoAlO (LCA) prepared with low Al content by evidencing the distribution of Al within the powders, which clearly affects the electrochemical profiles of associated LCA//Li cells. For all samples we initially also characterized the Li/(Co + Al) stoichiometry by Li MAS NMR, to discard the possible effect of excess Li in the samples.

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We here present the synthesis of a new material, Na(VO)Fe(PO)F, by the sol-gel method. Its atomic and electronic structural descriptions are determined by a combination of several diffraction and spectroscopy techniques such as synchrotron X-ray powder diffraction and synchrotron X-ray absorption spectroscopy at V and Fe K edges, Fe Mössbauer, and P solid-state nuclear magnetic resonance spectroscopy. The crystal structure of this newly obtained phase is similar to that of Na(VO)(PO)F, with a random distribution of Fe ions over vanadium sites.

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Among the positive electrode materials for Na-ion batteries, Na3V2(PO4)2F3 is considered as one of the most promising and generates high interest. Here, we study the influence of the sol-gel synthesis parameters on the structure and on the electrochemical signature of the partially substituted Na3V2-zAlz(PO4)2(F,O)3 materials. We demonstrate that the acidity of the starting solution influences the vanadium oxidation state of the final product.

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Layered oxide compositions LiNaNiSbO have been prepared by solid-state synthesis. A complete solid solution is evidenced and characterized by X-ray and neutron diffraction as well as Li and Na solid-state nuclear magnetic resonance spectroscopy. The transition-metal layer is characterized by the classic honeycomb Ni/Sb ordering, whereas a more uncommon randomly mixed occupancy of lithium and sodium is evidenced within the alkali interslab space.

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Sodium ion batteries offer an inexpensive alternative to lithium ion batteries, particularly for large-scale applications such as grid storage that do not require fast charging rates and high power output. Moreover, the use of polyanionic structures as cathode materials afford incredibly high structural stability relative to layered transition metal oxides that can undergo a structural collapse upon full removal of the charge carrying ions. Sodium iron fluorophosphate, NaFePOF, has demonstrated its viability as a potential cathode material for sodium ion batteries, having a robust framework even after multiple charge-discharge cycles.

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The complete description of defective structures and their impact on materials behavior is a great challenge due to difficulties associated with their reliable characterization in the nanoscale. In this paper, density functional theory (DFT) calculations are used to elucidate the solid-state nuclear magnetic resonance (NMR) spectra of LiMnO which, combined with X-ray diffraction (XRD), provide a full description of disorder in this compound. While XRD allows accurate quantification of planar defects, the use of solid-state NMR reveals limited vacancy concentrations that were undetected by XRD as NMR is highly sensitive to the atomic local environments.

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The influence of the initial Li/Co stoichiometry in LiCoO (LCO) (1.00 ≤ Li/Co ≤ 1.05) on the phase-transition mechanisms occurring at high voltage during lithium deintercalation ( V > 4.

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We have performed long time scale molecular dynamics simulations of the cubic and tetragonal phases of the solid lithium-ion electrolyte Li_{7}La_{3}Zr_{2}O_{12} (LLZO), using a first-principles parametrized interatomic potential. Collective lithium transport was analyzed by identifying dynamical excitations: persistent ion displacements over distances comparable to the separation between lithium sites, and stringlike clusters of ions that undergo cooperative motion. We find that dynamical excitations in c-LLZO (cubic) are frequent, with participating lithium numbers following an exponential distribution, mirroring the dynamics of fragile glasses.

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The electrochemical properties of the P2-type NaxMn1/2Fe1/2O2 (x = 0.62) phase used as a positive electrode in Na batteries were tested in various voltage ranges at C/20. We show that, even if the highest capacity is obtained for the first cycles between 1.

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Thermal treatment of the Tavorite-type material FePO(4)·H(2)O leads to the formation of two crystallized iron phosphates, very similar in structure. Their structural description is proposed taking into account results obtained from complementary characterization tools (thermal analyses, diffraction, and spectroscopy). These structures are similar to that of the pristine material FePO(4)·H(2)O: iron atoms are distributed between the chains of corner-sharing FeO(6) octahedra observed in FePO(4)·H(2)O and the octahedra from the tunnels previously empty, in good agreement with the formation of a Fe(4/3)PO(4)(OH)-type phase.

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Lamellar A(x)CoO(2) cobalt double oxides with A = Li, Na, and K (x approximately 0.6) have been synthesized and their chemical (alkali content, oxidation state, and structure) and physical (resistivity, thermopower, magnetization, and specific heat) properties have been studied. All the three materials exhibit strong electron correlation emphasized by their behavior ranging from Fermi liquid to spin-polarized system.

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Various P2 and P'3-Na(x)CoO(2) phases, with x ranging approximately from 0.6 to 0.75, have been studied by variable-temperature (23)Na magic angle spinning (MAS) NMR.

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The layered P2-K4Co7O14 oxide has been prepared and characterized by means of X-ray diffraction, electrical conductivity, thermopower, and magnetic measurements. The crystal structure of K4Co7O14 (P6(3)/m space group, Z=2, a=7.5171(1) A, and c=12.

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