70 research outputs found

    Insertion compounds and composites made by ball milling for advanced sodium-ion batteries

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    Sodium-ion batteries have been considered as potential candidates for stationary energy storage because of the low cost and wide availability of Na sources. However, their future commercialization depends critically on control over the solid electrolyte interface formation, as well as the degree of sodiation at the positive electrode. Here we report an easily scalable ball milling approach, which relies on the use of metallic sodium, to prepare a variety of sodium-based alloys, insertion layered oxides and polyanionic compounds having sodium in excess such as the Na4V2(PO4)2F3 phase. The practical benefits of preparing sodium-enriched positive electrodes as reservoirs to compensate for sodium loss during solid electrolyte interphase formation are demonstrated by assembling full C/P′2-Na1[Fe0.5Mn0.5]O2 and C/‘Na3+xV2(PO4)2F3’ sodium-ion cells that show substantial increases (>10%) in energy storage density. Our findings may offer electrode design principles for accelerating the development of the sodium-ion technology

    Improving ionic conductivity by Mg-doping of A2SnO3 (A=Li+, Na+)

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    The search for Li ions conducting ceramics is burgeoning, owing to the regain interest for solid state batteries. Here we investigate the effect of Mg substitutions on the ionic conductivity of the A2SnO3 (A=Li, Na) phases. Pure A1.8Mg0.1SnO3 and A2.2Mg0.1Sn0.9O3 were structurally characterized and their ionic conductivity was measured by AC impedance spectroscopy. We show a decrease of the activation energy with increasing the Mg substitution and found ionic conductivities three and two orders of magnitude higher for Li2.2Mg0.1Sn0.9O3 and Na1.8Mg0.1SnO3 as compared to pristine Li2SnO3 and Na2SnO3, respectively. Neutron diffraction was used to determine the Mg localization in the crystal structure and to provide a rationale for the ionic conductivity changes. Our results confirm the high sensitivity of the ionic conductivity on chemical substitutions, even limited ones

    Crystal structure of tooeleite, Fe6(AsO3)4SO4(OH)4·4H2O, a new iron arsenite oxyhydroxysulfate mineral relevant to acid mine drainage

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    International audienceresolution synchrotron XRD powder data recorded on a sample from Tooele county, Utah. The structure is monoclinic, space group C2/m, a = 8.9575(1), b = 6.4238(1), c = 9.7912(1) Å, β = 96.032(1)°, V = 560.27(3) Å3, dcalc = 3.16 g/cm3. The structure was solved by direct methods and atomic positions, site occupancies, and isotropic displacement parameters were reÞ ned by the Rietveld method. The AsO3 pyramids bond to FeO6 octahedra by both edge- and corner-linkage, forming layers that intercalate SO4 groups. Assignment of structural H2O and OH groups were done from bond-valence analysis. Tooeleite is the only arsenite-sulfate mineral known and has been recently identiÞ ed as the main constituent of stromatolite-like deposits in the Carnoulès acid mine, Gard, Franc

    La réactivité des pigments composés de chrome dans un décor de porcelaine

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    International audienceThis paper presents a comprehensive investigation at the microscopic scale of various pigments composed of chromium from the French ‘Manufacture de Sèvres’ to establish the origin of color in glazes. Electron microscopy coupled with X-ray diffraction allows the determination of the microstructure and composition of the crystalline phases after firing. X-ray absorption spectroscopy reveals subtle changes in the medium-range ordering around Cr with high spatial resolution, in the pigment grain or at the pigment/glass interface. Principal results indicate systematic and common changes whatever the pigment types: (i) Cr-enrichment for the final crystals, that controls the coloration of the glaze, (ii) migration of specific elements such as Al or Zn from the pigments to the amorphous part of the glaze, and (iii) crystallization of anorthite in the near proximity of the altered Cr-bearing crystalline pigments

    Long-range antiferromagnetic order in malonate-based compounds Na2M(H2C3O4)2·2H2O (M = Mn, Fe, Co, Ni)

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    International audienceThe recently discovered metal-malonate compounds of formulae Na 2 M(H 2 C 3 O 4) 2 ·2H 2 O with M = Mn, Fe, Co, Ni are investigated for their magnetic properties. While the Cu-based material is a weak ferromagnet, all other members present antiferromagnetic interactions. Neutron powder diffraction experiments reveal the establishment of a long range magnetic order at low temperature in the Pbca Shubnikov magnetic group. The magnetic structures are characterized by antiferromagnetic layers perpendicular to [001]. These layers are stacked antiparallel (M = Fe) or parallel (M = Mn, Ni) in the (a, c) plane. Magnetic moments are collinear to b for the former and to c for the latter. The M = Co malonate exhibits a non-collinear magnetic structure intermediate between the two latter, with components along b and c. Density functional theory calculations indicate that the dominant magnetic interaction, J 1 , occurs along a malonate group via a carboxylate and links two transition metals within the same layer, while other interactions (inter-or intra-layer) are much weaker, so that these compounds present the dominant characteristics of 2D-antiferromagnets

    Lithium Insertion/Extraction into/from LiMX 2

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