The role of sulfate ions coming from source materials on the properties of Li1.05Mn2O4 cathode for lithium ion batteries

Li1.05Mn2O4 cathodes with different amounts of sulfate were synthesized by sol–gel process. X-ray diffraction (XRD) patterns indicated the pristine Li1.05Mn2O4 has a single phase of cubic spinel structure. Mn2O3 impurity was observed in the XRD patterns of Li1.05Mn2O4 spinels with SO42− anions, and the content of the Mn2O3 impurity rose with increasing SO42− amount. The sulfate ions coming from source materials existed as Li2SO4 in the Li1.05Mn2O4 spinels. As the molar ratio of SO42− to Mn increased from 0 to 0.03, the initial discharge capacity of the Li1.05Mn2O4 cathodes decreased from 119.4 to 97.9 mAh g−1, and the storage performance decreased dramatically. Cyclic voltammetry (CV) and AC impedance studies revealed that the reversibility of the cathodes decreased and the electrochemical impedance rose with the increase of SO42− amount.