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Low intrinsic electronic conductivity is the main disadvantage of LiFePO4 when used as a cathode material in lithium ion batteries. The paper offers experimental proofs of the theoretical prediction that fluorine doping of LiFePO4 can enhance its electrical conductivity. The LiFePO4 and fluorine-doped LiFePO4 olivine type, carbon-free powders are synthesized and examined. The crystal structure refinements in the Pnma space group reveal that doping with fluorine ions preserves the olivine structure, while reducing both the lattice parameters and the antisite defect, and increasing the crystallite size. A small amount of incorporated fluorine enhances the electrical conductivity from 4.6×10−7 S cm−1 to 2.3×10−6 S cm−1 and has a positive impact on the electrochemical performance. Several spectroscopy techniques (Mössbauer, FTIR, and Raman) reveal differences between the two powders and additionally support the findings of both the Rietveld refinement and the conductivity measurements.

Magnetic properties of Fe2O3/SiO2 samples were studied after being produced by sol-gel synthesis and formation of epsilon-Fe2O3 polymorph. Samples were thermally treated, using different annealing temperatures and annealing times. The size and morphological characteristics of the iron oxide nanoparticles were examined using a TEM microscope. We used the ellipticity of shapes, which is a measure of how much the shape of a nanoparticle differs from a perfect ellipse, in order to quantitatively describe morphological properties of nanoparticles. Coercivity measurements were used to identify and monitor the formation of the epsilon-iron oxide phase during the thermal treatments (annealing). Coercivity values were in the range from 1.2 to 15.4 kOe, which is in accordance with previous experience regarding the existence of epsilon-Fe2O3. We have determined the optimal formation conditions for the epsilon-Fe2O3 polymorph (t=1050 degrees C for 7 h, H-c=15.4 kOe), as well as the narrow temperature interval (1050-1060 C) in which the polymorph abruptly vanished (H-c=2300 Oe), on the basis of results of the magnetic properties. The threshold temperature for the epsilon-Fe2O3 phase transformation was measured as 1060 degrees C. We found that different annealing temperatures and annealing times significantly affected magnetic properties of the examined samples.

Olivine-type LiFePO4 composite powders with carbon were synthesized by freeze drying and subsequent thermal annealing. The main purpose of the research is to explore how various dicarboxylic acids as carbon sources influence the electrochemical properties of the resulting composites. Three dicarboxylic acids (oxalic, malonic, and adipic) were used as a carbon source. The synthesis was followed by X-ray powder diffraction, scanning electron microscopy, particle-size analysis, and electrochemical experiments. It is shown that the amount of the in situ formed carbon depends on the thermal behaviour of the acids in inert atmosphere rather than on their carbon content. Cyclic voltammetry experiments and galvanostatic cycling illustrate the behaviour of different powders: the powder obtained with oxalic acid yields the highest discharge capacity at small currents, while the one obtained with adipic acid shows better high-current response. Malonic acid has turned out to be a poor carbon source and it consequently yields powder with poor electrochemical performance. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The hydrogen desorption properties and kinetics of MgH2-VO2 composite prepared by mechanical milling of MgH2 and VO2 have been investigated. Structural characterization of produced nanocomposite was done by X-ray powder diffraction (XRD), particle size analysis and scanning electron microscopy (SEM). The structure and morphology of the composite have been correlated with hydrogen desorption properties investigated by differential thermal analysis (DTA). It has been shown that short mechanical milling of nanostructured VO2 and MgH2 leads to decrease of hydrogen desorption temperature of MgH2 by 80 K. The mechanism of desorption has been changed from phase boundary reaction, spherical symmetry for untreated MgH2 to phase boundary reaction, cylindrical symmetry for the composite material. The activation energy for desorption has been reduced by adding VO2 ceramics as a catalyst. (C) 2012 Elsevier Ltd and, Techna Group S.r.l. All rights reserved.

alpha-Fe2O3 nanospheres with diameters of 20-40 nm and FeOOH nanorods with diameters of 150-200 nm and lengths of 0.5-1.0 mu m were synthesized via hydrolysis of Fe(NO3)(3) and FeCl3 solutions, respectively, in the presence of urea and oleic acid, under reflux at temperature similar to 90 degrees C for 8 h. The molar ratio of Fe3+ ions and urea were changed until pure phases have been obtained. The key parameter of the synthesis which provides pure hematite and beta-FeOOH phases was the pH. The samples were characterized by X-ray powder diffraction, transmission electron microscopy and Mossbauer spectroscopy. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

VO2(B) has been successfully synthesized by simple, facile and environmental friendly one-step solvothermal method using V2O5 and ethanol as a starting agent. Obtained micrometer-sized powder was composed from mutually welded nanosized rod-like, flat and snowflake structures. VO2(B) powder was tested for possible application as anode material for aqueous lithium ion batteries. Lithium intercalation/deintercalation reaction has been carried out by cyclic voltammetry in a saturated aqueous solution of LiNO3. At scan rate of 10 mV s(-1) very stable cyclic performance of such obtained VO2 was established with discharge capacity around 184 mAh g(-1). (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.