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

Two distinct mesoporous nanostructures, that is, rod and sheet cobalt oxalate (CoC 2 O 4 ), 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 CoC 2 O 4 ·2H 2 O formation. The critical dehydration process of CoC 2 O 4 ·2H 2 O led to anhydrous CoC 2 O 4, and its thermal properties are investigated by thermogravimetric analysis. Electrochemical properties of anhydrous CoC 2 O 4 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 CoC 2 O 4 nanorods and sheets is 1599 and 1518 mA h g –1, respectively, at 1C-rate. Anhydrous CoC 2 O 4 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 CoC 2 O 4 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.