Hydrothermal synthesis of Li-Mn spinel nanoparticle from K-Birnessite and its electrochemical characteristics

Abstract

Li-Mn spinel (LiMn 2O 4) is prepared by a hydrothermal process with K-Birnessite (K xMnO 2·yH 2O) as a precursor. The K-Birnessite obtained via a hydrothermal process with potassium permanganate [KMnO 4] and urea [CO(NH 2) 2] as starting materials are converted to Li-Mn spinel nanoparticles reacting with LiOH. The molar ratio of LiOH/K-Birnessite is adjusted in order to find the effect of the ratio on the structural, morphological and electrochemical performances of the Li-Mn spinel. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetry (TG) are used to investigate the crystal structure and morphology of the samples. Galvanostatic charge and discharge are carried out to measure the capacity and rate capability of the Li-Mn spinel. The capacity shows a maximum value of 117 mAhg -1 when the molar ratio of LiOH/K-Birnessite is 0.8 and decreases with the increase of the ratio. However the rate capability is improved with the increase of the ratio due to the reduction of the particle size.