Study On The Solid-State Synthesis And Modification Of Spinel Lithium Manganate

Along with the electronic information tide coming, serious energy and environmentproblems accelerate quickly development of chemical battery and elevated high qualityof lithium ion batteries. People and researchers are concentrated on the lithium ionbattery because of its outstanding performance of high work voltage, safety, long cycletimes and environment-friendliness and so on. The electrical facilities became more andmore small and lightly and paving for explored the new energy resources and newmaterials with the Li-ion battery coming now. Anode materials as a very important partof lithium ion battery and play a very vital function to limited the development of Li-ionbattery. At present, LiMn₂O₄with enrich sources, non-toxic, low cost and highstability was wildly used, but its drawbacks of relatively poor cyclability ofrechargeable lithium-ion battery. Therefore, improve the electrochemical performanceof LiMn₂O₄has become the hot topic of research.In this study, the worldwide development of LiMn₂O₄in recent years wassummarized and analyzed, aimed at the defects of LiMn₂O₄such as low specificcapacity and relatively poor cyclability, we concentrated on the doping and coatedmodification method of LiMn₂O₄cathode materials. The spinel LiMn₂O₄cathodematerials were synthesized by solid-state reaction. The structure and surfacemorphology of materials were investigated by thermogravimetric differential thermalanalyzer, X-ray diffraction and scanning electron microscope.Spinel LiMn_2-xBi_xO_4-yF_y（x=0,0.03; y=0,0.05,0.1） materials were synthesized bysolid state reactions, all the synthesized materials are pure spinel phase with smoothsurface and uniform size. The discharge specific capacity of LiMn_1.97Bi_0.03O_3.95F_0.05were104.2mA·h/g and81.6mA·h/g at the charge-discharge current of2C and5C atroom temperature, respectively, which were higher than95.7mA·h/g and60.5mA·h/gof LiMn₂O₄.When cycled for30and100times at the charge-discharge rate of0.2C and1C, the capacity retention of LiMn_1.97Bi_0.03O_3.95F_0.05are90.88%and91.8%, whichwere much higher than86.5%and78.7%of LiMn₂O₄. Bi and F co-doping can enhancethe cycling behavior of LiMn₂O₄, especially the cycling behavior of highcharge-discharge rate.TiO₂coated LiMn₂O₄was prepared by ultrasonic assisted solution methods.LiMn₂O₄and TiO₂-coated LiMn₂O₄have the similar X-ray diffraction patterns anduniform size, no serious aggregation can be observed. The initial discharge specificcapacity of LiMn₂O₄coated with1wt.%TiO₂was slight smaller than the uncoated one.When cycled at room temperature for50times at the current of0.2C, the capacityretention of TiO₂coated LiMn₂O₄was91.7%, which was higher than86.6%for thebare one. When the current reaches1C, the capacity retention of1wt.%TiO₂coatedLiMn₂O₄becomes5.9%higher than the uncoated one after cycling100times at roomtemperature. Coating of TiO₂on LiMn₂O₄can significantly improve the cyclability ofLiMn₂O₄.