TiO_2(B)表面修饰富锂层状氧化物Li(Li_(0.17)Ni_(0.2)Mn_(0.58)Co_(0.05))O_2正极材料

Surface Modification of Li-rich Layered Li(Li_(0.17)Ni_(0.2)Mn_(0.58)Co_(0.05))O_2 Oxide with TiO_2(B) as the Cathode for Lithium-ion Batteries

采用喷雾干燥法和沉淀法,制备了表面修饰TiO2（B）（2wt%、4wt%、6wt%和8wt%）的富锂层状氧化物Li（Li0.17Ni0.2Mn0.58Co0.05）O2正极材料。X射线衍射（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）结构测试分析结果表明,修饰TiO2（B）后样品的体相结构仍然保持初始样品的层状结构,仅氧化物颗粒表面附着有少量TiO2（B）纳米晶。示差扫描量热测试（DSC）表明,与初始样品比较,修饰TiO2（B）后样品的热稳定性得到明显改善。在2.0~4.8 V范围内进行恒流电化学性能测试。研究显示,在0.1C（1C=300 m A/g）倍率下,修饰4wt%TiO2（B）样品的首次放电比容量可达296.4 m Ah/g,首次库伦效率则由初始样品的77.7%提升到修饰TiO2（B）后样品的84.3%,100周循环后电极容量保持率由初始样品的69.5%提升到修饰TiO2（B）后样品的80.2%。即使在阶梯倍率的2C倍率下,修饰4wt%TiO2（B）的样品仍具有较高的电化学容量（166.5 m Ah/g）。以上研究结果表明,表面修饰TiO2（B）纳米晶可以显著改善富锂层状氧化物Li（Li0.17Ni0.2Mn0.58Co0.05）O2的热稳定性和电化学性能。

The Li-rich layered Li（Li0.17Ni0.2Mn0.58Co0.05）O2 oxide was prepared by a spray-drying method. Subse- quently, the surface modification with TiO2（B） nanocrystallites （2wt%, 4wt%, 6wt%, 8wt%） was introduced into the Li-rich layered Li（Li0.17TNi0.2Mn0.58Co0.05）O2 oxide by precipitation method. It is demonstrated that there is no obvi- ous change in the crystallographic structure of the Li-rich layered Li（Li0.17Ni0.2Mn0.58Co0.05）O2 oxide based on the analysis of XRD, SEM and TEM, while only the surface of the oxide is modified with TiO2（B） nanoerystallites. It is indicated from DSC curves that the thermal stability of Li-rich layered oxide is obviously improved by the surface modification with TiOffB） nanocrystallites. Correspondingly, the large discharge capacity of 296.4 mAh/g and high coulombic efficiency of 84.5% are obtained at 0.1C rate （1C=300 mA/g） in the first cycle for the Li-rich layered oxide after the surface modification with TiO2（B） nanocrystallites （4wt%）. Moreover, the capacity retention after 100 cycles is increased from 69.5% for the pristine sample to 80.2% for the TiO2（B）-modified sample. Even at 2Crate, the large discharge capacity of 166.5 mAh/g is still obtained for the TiO2（B）-modified sample. Apparently,it is demonstrated from the above results that the surface modification with TiO2（B） nanocrystallites can improve the thermal stability and electrochemical performance of the Li-rieh layered Li（Li0.17 TNi0.2Mn0.58Co0.05）O2 oxide .