Structure and electrochemical properties of La, F dual-doped iLa0.01Mn1.99O3.99F0.01 cathode materials

The cathode materials LiMn₂O₄ and rare earth elements La-doped or La and F dual-doped spinel lithium manganese oxides were synthesized by the citric acid-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis (DTA) and thermogravimetry (TG) measurements, X-ray diffraction (XRD), scanning electronic microscope (SEM), cyclic voltammetry (CV), and charge-discharge test. XRD data shows that all the samples exhibit the same pure spinel phase, and the LiLa_0.01Mn_1.99O_3.99F_0.01 and LiLa_0.01Mn_1.99O₄ samples have smaller lattice parameters and unit cell volume than LiMn₂O₄. SEM indicates that LiLa_0.01Mn_1.99O_3.99F_0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn₂O₄, LiLa_0.01Mn_1.99O₄, and LiLa_0.01Mn_1.99O_3.99F_0.01 are 129.9, 122.8, and 126.4 mAh·g⁻¹, and the capacity losses of the initial values after 50 cycles are 14.5%, 7.6%, and 8.0%, respectively. The CVs show that the La and F dual-doped spinel displays a better reversibility than LiMn₂O₄.