Reserch On Synthesis And Electrochemical Charactetrization Of Nano Composite Oxides

Rechargeable lithium ion battery, owing to its stable electrical system,high power density and ecofriendly has been widely used in portable electrical devices such as digital camera, intelligent mobile, tablet computer etc. At the same, it shows potentially an good candidate for power source of EV and HEV. Spinel LiMn2O4used as a lithium ion battery cathode material has adventages such as much more sources of raw materia, low cost, good thermal stability and good resistance to overcharging. But its fast capacity decay under the condition of high temperature is one of the main factors that restrict its further commercialization. Spinel lithium titanate (Li4Ti5O12) as a lithium ion battery cathode material has been called "zero strain material" which has a good reversibility, stable discharge voltage platform, a low potential compare to metallic lithium, It is a kind of potential lithium ion battery anode materials. But due to its inherent low conductivity property and the bad performace in large current density limit its commercial application. Nanometer-sized materials can improve the electrochemical performance of lithium ion batteries, especially the rapid charge and discharge performance which is an important development direction of lithium ion battery materialsIn this paper, we choose spinel LiMn2O4and spinel lithium titanate as the research object. The major research content is as follows:Hierarchical LiMn2O4microspheres were prepared using urchin-like α-MnO2as a self-sacrifical template. X-ray diffraction analysis (XRD) shows they belong to the spinel cubic crystal system. From the scanning electron microscopy (SEM) images, it could be found that the LiMn2O4were core-shell spherical which composed of nano particles with a diameter from2to5μm. At0.1C,0.5C,1C,2C and5C, it shows discharge capacity of114,104,101,95,82mAhg-1respectively, and it also shows a good reversibility. Furthermore, it has good direct electrochemical and electrocatalytic performance.Nanoparticle precursor was prepared by solvethermal method using1,4-dioxane and water as mixture solvent.Subsequently, Li4Ti5O12nanoparticles was prepared by low temperature heat treatment the precursor. SEM shows that the product was composed of nanoparticles which size is about100nm. The electrochemical test result shows that at0.1C,0.5C,1C,1.5C,2C the Li4Ti5O12nanoparticles first discharge capacity were176,151,143,139,138mAhg-1respectively.Porous precursor was synthetized by coprecipitation method with NH4HCO3as frother and template agent directional hydrolysis of tetrabutyl titanate. The amount of NH4HCO3which influence the morphology of the precursor was investigated. Li4Ti5O12material was then prepared by calcining the precursor. The electrochemical test result shows that at0.1C,0.5C,1C, the porous Li4Ti5O12first discharge capacity were154.7,82.9,62.5mAhg-1respectively. At the same time, good cycling performance.