Study on high voltage (5 V) spinel lithium manganese oxide LiNi0.5Mn1.5O4 by doping niobium

The effect of niobium ions with high-valence doping on high-voltage LiNi_0.5Mn_1.5O₄ (LNMO) materials was investigated. LiNi_0.5Mn_1.5−xNb_xO₄ was prepared by doping high-valent niobium ions into LiNi_0.5Mn_1.5O₄ material using the organic assisted combustion method. The experimental samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical impedance (EI), and cyclic voltammetry (CV) analysis. The experimental results show that -doping with high-valence niobium ions changes the orientation of the crystal plane growth of spinel particles, and the morphology of these particles changes from the octahedral shape before doping to the spherical shape after doping. With the increase in doping amount, the crystal structure changes gradually, resulting in the Li_0.96Nb_1.01O₃ impurity phase. The doping of high valence-niobium ions increases the content of Mn³⁺ in the material, resulting in the appearance of a 4 V discharge platform and the formation of a 4.7 and 4 V discharge platforms. The doping of Nb can improve the cycling stability of LiNi_0.5Mn_1.5O₄ material, but the specific capacity of the material is reduced.