The Research On Synthesis And Doping Modification Of Layered LiMnO₂ Cathodes For Li-ion Battery

Lithium-ion battery is a new type of secondary batteries developed during 1990's. Lithium manganese oxides have advantages as the positive active materials for lithium-ion batteries, such as non-toxicity, low cost etc. However, the capacity fade of lithium manganese oxides makes its application difficulty. Recently, a new layered LiMnO2 which has higher capacity than spinel LiMn2O4, has become the hot topic of cathode of lithium-ion batteries.On the base of reviewing the development of lithium ion battery and its cathode materials in detail, layered LiMnO2 were chosen as cathode material and their synthesis and modification were studied. In this paper LiMnO2 powders were prepared via ion-exchange synthesis. The effects of synthesis conditions on structure and electrochemical behavior of LiMnO2 were studied. We discussed the effects of reactive temperature and time, washing method and atmosphere on the performance of product and optimized synthesis condition. Meanwhile, the modified materials were also conducted on the basis of LiMnO2 material. In addition, we used X-Ray Diffraction (XRD) was to analyze phase composition, Scanning Electron Microscope (SEM) to observe superficial morphology, charge-discharge test to study specific capacity and cyclic properties, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscope (EIS) to discuss electrochemical reactive mechanism.The study shows that LiMnO2 has an ordered layered structure and good electrochemical properties, its 50th specific charge capacity is 65mAh/g. Layered LiMn1-xMxO2 (M=Al, Ni; x=0.05) compounds have been synthesized by ion exchange from the corresponding sodium precursors. During electrochemical charge-discharge cycling, the LiMn1-xMxO2 (M=Al, Ni; x=0.05) compounds develop two voltage plateaus at 4 and 3 V vs. a lithium anode, suggesting spinel-like cation ordering. However, the resulting materials show excellent cycle ability and high reversible capacity when cycled over both voltage plateaus, unlike the LiMn2O4 spinels. Specific capacities obtained for LiMn0.95Al0.05O2 and LiMn0.95Ni0.05O2 cathodes are about 70 and 65 mAh/g, respectively. Their capacity values remain stable on subjecting the electrodes to charge-discharge...