Electrochemical behaviour of nano-sized spinel LiMn2O4 and LiAlxMn2−xO4 (x=Al: 0.00–0.40) synthesized via fumaric acid-assisted sol–gel synthesis for use in lithium rechargeable batteries

Pristine spinel LiMn2O4 and LiAlxMn2−xO4 (x=Al: 0.00–0.40) with sub-micron sized particles have been synthesized using fumaric acid as chelating agent by sol–gel method. The synthesized samples were subjected to thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV) and galvanostatic cycling studies. The TGA curve of the gel shows several weight-loss regions stepwise amounting to 55% till 800 °C attributed to the decomposition of the precursors. Calcination to higher temperatures (800 °C) yields pure-phase spinel (LiAlxMn2−xO4), as it is evident from the high-intensity XRD reflections matching to the standard pattern. SEM and TEM studies confirm that the synthesized grains are of uniform regular surface morphology. FT-IR studies show stretching and bending vibration bands of Li–O, Li–Al–Mn–O. LiAl0.1Mn1.90O4 spinel was found to deliver discharge capacity of 139 mA h/g during the first cycle with columbic efficiency of 97%. LiAl0.1Mn1.90O4 spinel exhibits the high cathodic peak current indicating better electrochemical performance. Low doping (x=0.1) of Al is found to be beneficial in stabilizing the spinel structure.