Browsing by Author "Belharouak, I"

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    Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3
    (Elsevier, 2016-06-01) Ben Yahia, H; Essehli, R; Avdeev, M; Park, JB; Sun, YK; Al-Maadeed, MA; Belharouak, I
    The new compounds NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 crystallize with a stuffed α-CrPO4-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structures of NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 a statistical disorder Ni2+/Cr3+ was observed on both the 8g and 4a atomic positions, whereas in NaCoCr2(PO4)3 the statistical disorder Co2+/Cr3+ was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 delivered specific capacities of 352, 385, and 368 mA h g−1, respectively, which attests to the electrochemical activity of sodium in these compounds. © 2016 Elsevier Inc.
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    The novel stairs-like layered compound Co5(OH)6(H2O)2[SO3]2
    (De Gruyter, 2017-02-15) Ben Yahia, H; Shikano, M; Avdeev, M; Belharouak, I
    The new compound Co5(OH)6(H2O)2[SO3]2 was synthesized by a hydrothermal route and its crystal structure was determined from the combination of sin-gle crystal X-ray- and neutron powder-diffraction data. Co5(OH)6(H2O)2[SO3]2 crystallizes with the space group P21/c, a= 7.0229(19) Å, b= 5.4722(15) Å, c= 15.833(4), β= 106.34(1)°, V= 583.9(3) Å3 and Z= 4. The crystal struc-ture consists of a 2D-framework of cobalt octahedra shar-ing corners and edges and giving rise to a stairs-like layers, interconnected through O–H···O–S4 + hydrogen bonds. © Walter de Gruyter GmbH 2021