Study on the action mechanism of doping transitional elements in spinel LiNi0.5Mn1.5O4

Spinel LiNi0.5Mn1.5O4 is a very important and promising cathode material for lithium ion batteries. The strategy of doping elements is a common used way to improve its electrochemical properties. The action mechanism of doping elements in LiNi0.5Mn1.5O4 is complex. In this study, we synthesized the Cr, Fe-doped compounds LiNi0.45M0.1Mn1.45O4 (M = Cr, Fe) and pristine compound LiNi0.5Mn1.5O4 at the same annealing conditions. The as prepared samples display different morphological features. The thermogravimetric analysis shows different situation for these samples. Oxygen dissipation in the Cr-doped compound at high temperature is less than the other two samples. The XPS spectra display that the doping elements have influences on the chemical valence of Ni, and result in more Ni(III) amount in the Cr, Fe-doped products. The doped compounds exhibit excellent rate capability. At 10C-charge/10C-discharge rate, their capacities are 85 mAh g−1, 74 mAh g−1 and 50 mAh g−1 for LiNi0.45Fe0.1Mn1.45O4, LiNi0.45Cr0.1Mn1.45O4 and LiNi0.5Mn1.5O4, respectively.