Influence of Nb5+ Doping on Structure and Electrochemical Properties of Spinel Li1.02Mn2O4

The Li1.02NbxMn2-xO4 (x=0, 0.005, 0.01, 0.02, 0.04 and 0.1) materials were prepared by solid-state reaction method in which Li2CO3, electrolytic MnO2 and Nb2O5 were used as reactants. The influences of the Nb5+ doping on structure, morphology and electrochemical performance were systemically investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV) and AC impedance. XRD test showed that the prepared samples had single spinel structure although there was impurity phase of LiNbO3 existing in Li1.02NbxMn2-xO4 phase after Nb5+ doping. The doped materials with Nb5+ had smaller lattice parameters and crystal volume compared with pristine Li1.02Mn2O4. The endurance of overcharge was largely improved. In addition, the small amount of Nb5+ doping could increase the material conductivity.