Filter paper templated interconnected nanocrystalline LiMn2O4 with high coulombic efficiency and rate capability

Abstract

A novel filter paper templating method has been developed to prepare nanocrystalline LiMn₂O₄. Whatman 42 filter paper impregnated with the precursor gel produces ultrafine powder (80–100 nm) when calcined at 800 °C. The structure and morphology of the powder and the template have been studied in detail by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). A single phase cubic spinel with interconnected powder morphology is found. The electrochemical properties have been studied using 2032 coin type cells in the potential window of 3.4 to 4.5 V versusLi/Li⁺. Sharp oxidation–reduction peaks at 4.09/3.90V and 4.22/4.04V in the cyclic voltagram indicate high crystallinity and good reversibility of the cathode. A typical cell shows an initial discharge capacity of 97 mAh/g with ∼98% columbic efficiency. Rate capability study of the synthesized cathode has been performed by cycling the cell for 130 cycles at different current densities (0.1–1.5 mA/cm²) and it is observed that 80–100% retention of initial capacity is possible when cycled at 0.1–0.6 mA/cm². A capacity fading of only 0.03 mAh/g per cycle is observed even at 1.5 mA/cm² (8C). Thus, we have shown that simple filter paper templating technique can produce nanocrystalline LiMn₂O₄ with high coulombic efficiency (100–95%) and rate capability.