层状LiNi0.5Co0.2Mn0.3O2正极材料的Y2O3表面包覆

摘要

Y2O3-coated LiNi0.5Co0.2Mn0.3O2 cathode materials were prepared by precipitation method.The structures,morphologies and electrochemical properties were characterized by X-Ray diffraction (XRD),scanning electron microscopy (SEM),electrochemical impedance spectroscopy (EIS) and galvanotactic charge-discharge test.The results indicate that Y2O3 are coated uniformly on the surface of LiNi0.5Co0.2-Mn0.3O2,and have no effect on the crystal structure of LiNi0.5Co0.2-Mn0.3O2.The Y2O3-coated LiNi0.5Co0.2Mn0.3O2 materials exhibit excellent electrochemical performance.The LiNi0.5Co0.2Mn0.3O2 materials coated with 0.5% Y2O3 shows initial discharge capacity of 190.5 mAh/g at the rate of 20 mA/g in the voltage range of 2.5~4.5 V,the capacity retention ratio is 99.9% after 50 cycles.While the initial discharge capacity of the bared materials is slightly lower (187.0 mAh/g) and rapid capacity fade occurs during the following cycles,and the capacity retention ratio is 92.7% after 50 cycles.The discharge capacities of the LiNi0.5Co0.2Mn0.3O2 material coated with 0.5% Y2O3 is 150 mAh/g,with good rate capability.%采用沉淀法对层状LiNi0.5Co0.2Mn0.3O2正极材料进行Y2O3表面包覆,采用X射线衍射(XRD)、扫描电子显微镜(SEM)、电化学交流阻抗(EIS)及恒流充放电对所制备材料的结构、形貌及电化学性能进行表征.结果表明,Y2O3均匀包覆在LiNi0.5Co0.2Mn0.3O2材料的表面,并没有改变材料的晶体结构,且Y2O3包覆的正极材料表现出良好的电化学性能.在2.5~4.5V电压范围和20mA/g电流密度下,包覆0.5%Y2O3材料的首次放电容量190.5mAh/g,50次循环后,材料的容量保持率达到99.9%,而未包覆材料的首次放电容量略低(187.0mAh/g),且容量衰减较快,50次循环后,材料的容量保持率仅有92.7%.此外,包覆0.5%Y2O3的材料在400mA/g下放电容量仍有150mAh/g,表现出优异的倍率性能.