TiO2(B)表面修饰富锂层状氧化物Li(Li0.17Ni0.2Mn0.58Co0.05)O2正极材料

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(Li_0.17Ni_0.2Mn_0.58Co_0.05)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 mA/g)倍率下, 修饰4wt%TiO₂(B)样品的首次放电比容量可达296.4 mAh/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 mAh/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(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂的热稳定性和电化学性能。

Surface Modification of Li-rich Layered Li(Li0.17Ni0.2Mn0.58Co0.05)O2 Oxide with TiO2(B) as the Cathode for Lithium-ion Batteries

The Li-rich layered Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂ oxide was prepared by a spray-drying method. Subsequently, the surface modification with TiO₂(B) nanocrystallites (2wt%, 4wt%, 6wt%, 8wt%) was introduced into the Li-rich layered Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂ oxide by precipitation method. It is demonstrated that there is no obvious change in the crystallographic structure of the Li-rich layered Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂ oxide based on the analysis of XRD, SEM and TEM, while only the surface of the oxide is modified with TiO₂(B) nanocrystallites. It is indicated from DSC curves that the thermal stability of Li-rich layered oxide is obviously improved by the surface modification with TiO₂(B) 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 2C rate, 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-rich layered Li(Li_0.17Ni_0.2Mn_0.58Co_0.05)O₂ oxide.