High-Performing Mesoporous\nIron Oxalate Anodes for\nLithium-Ion Batteries

Abstract

Mesoporous iron oxalate (FeC₂O₄) with two\ndistinct morphologies, i.e., cocoon and rod, has been synthesized\nvia a simple, scalable chimie douce precipitation method. The solvent\nplays a key role in determining the morphology and microstructure\nof iron oxalate, which are studied by field-emission scanning electron\nmicroscopy and high-resolution transmission electron microscopy. Crystallographic\ncharacterization of the materials has been carried out by X-ray diffraction\nand confirmed phase-pure FeC₂O₄·2H₂O formation. The critical dehydration process of FeC₂O₄·2H₂O resulted in anhydrous FeC₂O₄, and its thermal properties are studied by thermogravimetric\nanalysis. The electrochemical properties of anhydrous FeC₂O₄ in Li/FeC₂O₄ cells are evaluated\nby cyclic voltammetry, galvanostatic charge–discharge cycling,\nand electrochemical impedance spectroscopy. The studies showed that\nthe initial discharge capacities of anhydrous FeC₂O₄ cocoons and rods are 1288 and 1326 mA h g^–1, respectively, at 1<i>C</i> rate. Anhydrous FeC₂O₄ cocoons exhibited stable capacity even at high <i>C</i> rates (11<i>C</i>). The electrochemical performance\nof anhydrous FeC₂O₄ is found to be greatly influenced\nby the number of accessible reaction sites, morphology, and size effects.