Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3

• Published in: Journal of solid state chemistry Vol. 238; pp. 103 - 108
• Main Authors: Yahia, H. Ben, Essehli, R., Avdeev, M., Park, J-B., Sun, Y-K., Al-Maadeed, M.A., Belharouak, I.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-06-2016
• Subjects: Anode; Crystal structure; Neutron diffraction; Sodium-ion battery; Synthesis; Synthesis; Sodium-ion battery; Anode; Neutron diffraction; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2016.03.011

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 368mAhg−1, respectively, which attests to the electrochemical activity of sodium in these compounds.
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•NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 were synthesized by sol-gel method.•The crystal structures were determined by using neutron powder diffraction data.•The three compounds crystallize with a stuffed α-CrPO4-type structure.•The three compounds were tested as anodes in sodium-ion batteries.•Relatively high specific capacities were obtained for these compounds.