Mesoporous Cobalt Oxalate Nanostructures as High-Performance Anode Materials for Lithium-Ion Batteries: Ex Situ Electrochemical Mechanistic Study

Two distinct mesoporous nanostnictures, 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 center dot 2H(2)O formation. The critical dehydration process of CoC2O4 center dot 2H(2)O 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.