Electrochemical Performance Of LiMn₂O₄Cathod Materials For Li-ion Battery

The lithium battery (LIB) has high capacities, wide working potential range, good cycling performance, good safety, which is widely used in many fields such as electric vehicles. LIBs with high energy density and long cycle life are attracting wide interest by researchers over the past few years. The electrode materials for electrochemical performance is significant, in which LiMn2O4one of the most promising cathode materials attracts extensive attention in the field of lithium-ion batteries due to its high reduction potential, intrinsic lower cost, environmental benign nature and better safety.The spinel LiMn2O4has3D tunnel structure, which can facilitate fast transfer of Li+from electrolyte to the surfaces of active materials during discharge-charge processes. It has been spotlighted in the field of lithium-ion batteries. Unfortunately, the practical application of spinel LiMn2O4cathode materials is still impeded due to its poor cycling performance, which mainly results from a disproportionation reaction (2Mn3+â†'Mn2++Mn4+) and structural transformation from cubic to tetragonal phase that is induced by Jahn-Teller distortion of Mn (III) with high spin. In this paper, spinel LiMn2O4nanoparticles with high crystallinity were prepared via a simple solid-state reaction. Moreover, Ni was doped in LiMn2O4due to improving its energy density and potential window.The XRD measurements were used to characterize crystal phase of the as-prepared samples. The morphology and structure of the materials were examined by scanning electron microscope (SEM). Some tests including charge/discharge cycle and AC impedance were used to research their electrochemical performance. The main research contents and results are as follows:(1) Spinel LiMn2O4nanoparticles with different particle dimensions, high crystallinity and phase purity were prepared on purposed by using three kinds of a-MnO2precursors with different morphologies via a simple solid-state reaction. It was found that among various a-MnO2precursors having morphologies such as rod, sphere and3D interconnected framework, the spinel LiMn2O4prepared from3D interconnected α-Mn02nanoparticles showed excellent cycling performance with the deliverable discharge capacity exceeded88mAh g-1after100cycle at5C current rate. The fading rate is0.06mAh g-1per cycle. (2) In order to improve energy density, different rations of Ni were doped in LiMnO4. The potential of LiNi0.5Mn1.5O4is about4.7V, which is far higher than4.05V. Furthermore, the energy density is496Wh Kg-1, which is much higher than that for the corresponding Li-ion batteries for electric vehicles.