Studies of Nano－sized Co304 as Anode Materials for Lithium－ion Batteries

The structural evolution of the Co₃O₄ fine powders prepared by rheological phase reaction and pyrolysis method upon different temperature has been investigated using X‐ray diffraction (XRD) topography. The electrochemical performance of Co₃O₄ electrode materials for Li‐ion batteries is studied in the form of Li/Co₃O₄ cells. The reversible capacity as high as 930 mAh/g for the Co₃O₄ sample heat‐treated at 600 °C is achieved and sustained over 30 times charge‐discharge cycles at room temperature. The detailed information concerning the reaction mechanism of Co₃O₄ active material together with lithium ion is obtained through ex‐situ XRD topography, X‐ray photoelectron spectroscopy (XPS) analysis and cyclic voltammetry (CV) technique. And it is revealed that a “two‐step” reaction is involved in the charge and discharge of the Li/Co₃O₄ cells, in which Co₃O₄ active material is reversibly reduced into xCoO(3 ‐ x)CoO and then into metallic Co.     

A new one‐dimensional nickel metal–organic framework: catena‐poly[[[diaquabis(4‐{[(1‐phenyl‐1H‐tetrazol‐5‐yl)sulfanyl]methyl}benzoato‐κO)nickel(II)]‐μ‐4,4′‐bipyridine‐κ2N:N′] monohydrate]

The title complex, {[Ni(C₁₅H₁₁N₄O₂S)₂(C₁₀H₈N₂)(H₂O)₂]·H₂O}_n, was synthesized by the reaction of nickel chloride, 4‐{[(1‐phenyl‐1H‐tetrazol‐5‐yl)sulfanyl]methyl}benzoic acid (HL) and 4,4′‐bipyridine (bpy) under hydrothermal conditions. The asymmetric unit contains two half Ni^II ions, each located on an inversion centre, two L⁻ ligands, one bpy ligand, two coordinated water molecules and one unligated water molecule. Each Ni^II centre is six‐coordinated by two monodentate carboxylate O atoms from two different L⁻ ligands, two pyridine N atoms from two different bpy ligands and two terminal water molecules, displaying a nearly ideal octahedral geometry. The Ni^II ions are bridged by 4,4′‐bipyridine ligands to afford a linear array, with an Ni...Ni separation of 11.361 (1) Å, which is further decorated by two monodentate L⁻ ligands trans to each other, resulting in a one‐dimensional fishbone‐like chain structure. These one‐dimensional fishbone‐like chains are further linked by O—H...O, O—H...N and C—H...O hydrogen bonds and π–π stacking interactions to form a three‐dimensional supramolecular architecture. The thermal stability of the title complex was investigated via thermogravimetric analysis.