Mesoporous iron oxalate (FeC(2)O(4)) with two distinct morphologies, i.e., cocoon and rod, has been synthesized via a simple, scalable chimie douce precipitation method. The solvent plays a key role in determining the morphology and microstructure of iron oxalate, which are studied by field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Crystallographic characterization of the materials has been carried out by X-ray diffraction and confirmed phase-pure FeC(2)O(4)·2H(2)O formation. The critical dehydration process of FeC(2)O(4)·2H(2)O resulted in anhydrous FeC(2)O(4), and its thermal properties are studied by thermogravimetric analysis. The electrochemical properties of anhydrous FeC(2)O(4) in Li/FeC(2)O(4) cells are evaluated by cyclic voltammetry, galvanostatic charge-discharge cycling, and electrochemical impedance spectroscopy. The studies showed that the initial discharge capacities of anhydrous FeC(2)O(4) cocoons and rods are 1288 and 1326 mA h g(-1), respectively, at 1C rate. Anhydrous FeC(2)O(4) cocoons exhibited stable capacity even at high C rates (11C). The electrochemical performance of anhydrous FeC(2)O(4) is found to be greatly influenced by the number of accessible reaction sites, morphology, and size effects.
Two
distinct mesoporous nanostructures, that is, rod and sheet
cobalt oxalate (CoC2O4), have been synthesized
via facile chimie douce precipitation technique. The selective interaction
between solvent type and crystallographic planes of the metal ion
is the key factor in morphological variations. The morphology and
microstructure are studied by high-resolution transmission electron
microscopy. Structural characterization of the materials has been
carried out by X-ray diffraction and confirmed phase pure CoC2O4·2H2O formation. The critical
dehydration process of CoC2O4·2H2O led to anhydrous CoC2O4, and its thermal
properties are investigated by thermogravimetric analysis. Electrochemical
properties of anhydrous CoC2O4 in half-cells
are studied by cyclic voltammetry, galvanostatic charge–discharge
cycling, and electrochemical impedance spectroscopy. The studies
showed that initial discharge capacity of anhydrous CoC2O4 nanorods and sheets is 1599 and 1518 mA h g–1, respectively, at 1C-rate. Anhydrous CoC2O4 nanostructures fabricated by this chimie douce process achieved
higher reversible capacity, more stable cycling, and better rate capabilities
than reported. The electrochemical performances of anhydrous CoC2O4 nanostructures are found to be significantly
influenced by morphology and porosity. In addition, the interfacial
electrochemical mechanism related to the transitional metal oxidation
states, phase structural changes, and distribution during cycling
are validated.
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