Li-S batteries are promising energy storage technology for the future, however there two major problems remained which need to be solved before successful commercialization. Capacity fading due to polysulfide shuttle and corrosion of lithium metal are directly connected with the type and quantity of electrolyte used in the cells. Several recent works show dependence of the electrochemical behavior of Li-S batteries on type of the electrolyte. In this work we compare and discuss a discharge mechanism of sulfur conversion in three different electrolytes based on measurements with sulfur K-edge XAS. The sulfur conversion mechanism in the ether based electrolytes, the most studied type of solvents in the Li-S batteries, which are enabling high solubility of polysulfides are compared with the fluorinated ether based electrolytes with a reduced polysulfide solubility and in carbonate based electrolytes with the sulfur confined into a ultramicroporous carbon. In all three cases the sulfur reduction proceeds through polysulfide intermediate phases with a difference on the type polysulfides detected at different steps of discharge. Electrification of road transport has increased the pressure on materials' scientists to improve performance of the current Li-ion batteries and to develop new advanced high energy battery technologies. 1Among several post lithium-ion technologies, the lithium sulfur (Li-S) batteries are recognized as the most promising for commercialization in the near future. A combination of lithium and sulfur in the electrochemical cell corresponds to the theoretical energy density of 2600 Wh/kg, while the maximum practically accessible energy density is predicted to be close to 600 Wh/kg.2,3 This is much higher compared to Li-ion batteries and besides that, sulfur is inexpensive and naturally abundant. Nevertheless, problems related to the solubility of polysulfides in the electrolyte and the related redox shuttle phenomena cause short cycle life, potential safety problems, poor cycling efficiency, and relative fast self-discharge. Additional problems of Li-S batteries are very low electronic conductivity of the both end members in the discharge and charge process (i.e. sulfur and Li 2 S) and extensive corrosion of the metal lithium anode.Different directions how to improve Li-S battery cycle life have been explored, like synthesis of the optimized porous host matrices with active sites for polysulfide anchoring, 4,5 design and optimization of separators which can effectively suppress polysulfide cross communication between electrodes 6,7 and protection of lithium by artificial SEI 8 or by additives. 9 While most of the research was performed in the binary mixture of solvents using alkyl ethers (glymes) and heterocyclic acetyl (dioxolane), less attention has been paid to the development of new electrolytes for Li-S batteries. 10 Reasons for that are nested in the requirements which should be fulfilled in the development of new formulations. First of all, electrolytes used in the electrochemical cells must...

Extended X-ray absorption fine structure (EXAFS) has been measured at both the K edges of gallium and arsenic in GaAs, from 14 to 300 K, to investigate the local vibrational and thermodynamic behaviour in terms of bond expansion, parallel, and perpendicular mean square relative displacements and third cumulant. The separate analysis of the two edges allows a self-consistent check of the results and suggests that a residual influence of Ga EXAFS at the As edge cannot be excluded. The relation between bond expansion, lattice expansion, and expansion due to anharmonicity of the effective potential is quantitatively clarified. The comparison with previous EXAFS results on other crystals with the diamond or zincblende structure shows that the values of a number of parameters determined from EXAFS are clearly correlated with the fractional ionicity and with the strength and temperature interval of the lattice negative expansion. © 2013 AIP Publishing LLC.

A series of FeCo-SiO 2 granular films of different FeCo atomic concentration (33-54%) have been prepared by fast atom beam sputtering technique and post-annealed in inert (Ar) and reducing (H 2 ) gas environments. Fe and Co K-edge XANES analysis of as-deposited films indicate that both Fe and Co are present mainly in their elemental (Fe 0 , Co 0 ) state. A partial oxidation of Fe and Co is observed, as the FeCo alloy content decreases (54 to 33%) due to reduced particle size. XANES/XAFS analysis shows the formation of FeCo alloy with bcc Fe structure in H 2 environment annealed films. The XRD and Raman analysis of Ar environment annealed films suggest the formation of Co 3 O 4 and CoFe 2 O 4 phases. The Ar environment is found not to be effective reducing medium to stabilize the FeCo alloy phase, while H 2 environment annealing (450-700 o C) leads to formation of bcc FeCo alloy.

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Accurate EXAFS spectra of solid and liquid rhodium at very high temperature were recorded at the E.S.R.E (BM29, Grenoble) The short range g(r) was determined using reliable EXAFS data-analysis methods based on ab-initio multiple scattering calculations. Experimental results were compared with moleculardynamics (MD) calculations. The first neighbor distribution departs from a simple Gaussian model, even at moderate temperatures in the solid phase.

Polycrystalline La doped multiferroic BiFeO3 samples are studied with x-ray diffraction, x-ray absorption spectroscopy (XAFS) and magnetization measurements. 20% La doped BFO exhibits better magnetic properties and from XAFS it is observed that the solubility limit of La into BFO is around 20%

Local structural distortions in Indium Arsenide at 11 GPa are studied applying the Fourier-transform analysis to As K-edge XAFS restricted to a short exploitable energy range of ~ 250 eV above the edge, due to the Bragg reflections from the diamond anvils. The best model for the distribution of In-atoms around As is obtained by combining available XRD data with a fitting procedure of the XAFS data, where alternative models for As coordination have been tested. InAs at 0.4 GPa was used as reference compound to minimize the number of variable parameters.