References of "Karegeya, Claude"
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See detailHydrothermal synthesis in presence of carbon black: Particle-size reduction of iron hydroxyl phosphate hydrate for Li-ion battery
Karegeya, Claude ULg; Mahmoud, Abdelfattah ULg; Cloots, Rudi ULg et al

in Electrochimica Acta (2017), 250

Iron hydroxyl phosphate hydrate Fe1.19(PO4)(OH)0.57(H2O)0.43 (FPHH) was obtained by hydrothermal synthesis at 220 °C for 6 hours. Addition of carbon black to the solution before hydrothermal treatment led ... [more ▼]

Iron hydroxyl phosphate hydrate Fe1.19(PO4)(OH)0.57(H2O)0.43 (FPHH) was obtained by hydrothermal synthesis at 220 °C for 6 hours. Addition of carbon black to the solution before hydrothermal treatment led to a reduction of the FPHH particle size from ∼10 μm in the carbon-free compound to ∼300–500 nm in the FPHH-10%C and FPHH-20%C composite with a good dispersion of conducting carbon black. X-ray diffraction, 57Fe Mossbauer spectroscopy and a thermal decomposition study showed that the addition of carbon black did not interfere with the formation of the FPHH phase. Thanks to its favorable microstructural characteristics, the FPHH-10%C and FPHH-20%C material exhibited good performance as positive electrode for Li-ion battery, with high initial discharge capacities of 150, 128 and 112 mAh g−1 at 0.25C, 0.5C and 1C rates respectively and 99% capacity retention after 150 cycles at 2C. These results show that addition of solid carbon directly into the solution prior to hydrothermal treatment is a simple and effective way to reduce particle size and also to improve electronic conductivity by dispersing conductive carbon around the active material. This approach is easily transferable to other compounds prepared by hydrothermal synthesis, in order to control particle size while retaining the advantage of crystallization at low temperature. [less ▲]

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See detailOne-step hydrothermal synthesis and electrochemical performance of sodium-manganese-iron phosphate as cathode material for Li-ion batteries
Karegeya, Claude ULg; Mahmoud, Abdelfattah ULg; Vertruyen, Bénédicte ULg et al

in Journal of Solid State Chemistry (2017), 253

The sodium-manganese-iron phosphate Na2Mn1.5Fe1.5(PO4)3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material ... [more ▼]

The sodium-manganese-iron phosphate Na2Mn1.5Fe1.5(PO4)3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na+ and presence of vacancies in A(2)’, Na+ and small amounts of Mn2+ in A(1), Mn2+ in M(1) , 0.5 Mn2+ and Fe cations (Mn2+,Fe2+ and Fe3+) in M(2), leading to the structural formula Na2Mn(Mn0.5Fe1.5)(PO4)3. The particles morphology was investigated by SEM. Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 hours at 220°C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220°C for 6 hours. When the reaction time was increased from 6 to 12, 24 and 48 hours, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mAhg-1 for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99 % during 50 cycles. [less ▲]

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See detailHydrothermal synthesis of tailored new  promising phosphate particles for lithium and sodium ion batteries
Karegeya, Claude ULg; Mahmoud, Abdelfattah ULg; Sougrati Tahar, Moulay et al

Conference (2016, December 16)

The rechargeable Li-ion batteries dominate the currently used storage systems due to their unrivalled electrochemical properties. However, this technology needs more improvements to meet coast, high ... [more ▼]

The rechargeable Li-ion batteries dominate the currently used storage systems due to their unrivalled electrochemical properties. However, this technology needs more improvements to meet coast, high capacity, safety and environmental requirements. Current researches on Li-ion batteries are focusing on the development of safe and cheap electrode compounds with good electrochemical performance. Iron phosphate-based electrodes have attracted increasing interest due to their environmental compatibility, low cost and its promising electrochemical performance as positive electrode materials in LIB. In this work, we report the electrochemical properties of Fex(PO4)(OH)y.zH2O) cathode material obtained by one-pot hydrothermal synthesis route, a technique which produces the particles with suitable properties for electrode application. We show that the addition of a conducting carbon (carbon black or carbon nanotubes) into the solution has a strong influence on reducing the size and tailoring morphology of material particles. These are among the main factors to enhance the electrochemical performance of the material. Combined with electrochemical and XRD studies, operando Mössbauer analysis shows that Fex(PO4)(OH)y.zH2O) undergoes a reversible reduction/oxidation during lithium intercalation/ deintercalation processes. Acknowledgments This work was supported by the Walloon Region through the BATWAL project [PE Plan Marshall 2.vert]; and the Beware Fellowship Academia [2015-1, RESIBAT n° 1510399]. [less ▲]

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See detailPhosphate-based composite electrodes for Li/Na-ion batteries: upscalable solution syntheses with in-situ solid carbon addition
Vertruyen, Bénédicte ULg; Brisbois, Magali; Eshraghi, Nicolas ULg et al

Conference (2016, September 22)

Since the success story of lithium iron phosphate, other phosphate-based compounds have attracted a lot of interest as promising candidates for positive electrodes in lithium-ion or sodium-ion batteries ... [more ▼]

Since the success story of lithium iron phosphate, other phosphate-based compounds have attracted a lot of interest as promising candidates for positive electrodes in lithium-ion or sodium-ion batteries. Their electronic conductivity usually has to be improved through the preparation of composite powders ensuring intimate contact between the active material and conductive carbon. We report on the one-step synthesis of composite precursors using spray-drying or hydrothermal synthesis routes, two techniques which offer easy scaling-up of production. We show that addition of a solid carbon source (carbon black or carbon nanotubes) into the solution has a strong influence on the powder microstructure and is very effective in improving the battery cycling performance, taking our recent results on phosphates [Fex(PO4)(OH)y.zH2O)] and fluorophosphates [Na2FePO4F, Na3V2(PO4)2F3] as examples. We also compare this approach with the addition of the carbon source as a soluble precursor (such as ascorbic acid or citric acid) where the in situ formation of carbon is achieved by a heat treatment in inert atmosphere (typically argon). [less ▲]

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See detailEffects of Starch as Carbon precursor on hydrothermal synthesis and Electrochemical performance of Sodium manganese iron phosphate /carbon
Karegeya, Claude ULg; Vertruyen, Bénédicte ULg; Cloots, Rudi ULg et al

Poster (2014, November 05)

Currently Sodium based electrode materials for Li and Na-ion batteries are getting more attention as the most promising potential alternatives of their lithiated counterparts due to their cost effective ... [more ▼]

Currently Sodium based electrode materials for Li and Na-ion batteries are getting more attention as the most promising potential alternatives of their lithiated counterparts due to their cost effective, environmental friendly characteristics and availability of sodium. Nevertheless, it remains a practical challenge to find an electrode material of LIBs and SIBs showing ideal performance. We report here a composite material of Sodium manganese iron phosphate/carbon, successfully synthesized by hydrothermal method. We have characterized our material by using a combination of Powder X-ray diffraction (XRD), scanning electron Microscopy (SEM) and thermal gravimetric analysis (TGA). Sodium manganese iron phosphate (NMFP) particles are electrochemically activated by starch and acetylene black to form NMFP/C cathode material for LIBs. NMFP/C composite in which starch is used as carbon precursor exhibits good discharge capacity due to the presence of pyran rings which increase NMFP/C conductivity. [less ▲]

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