正极材料Li1．2Mn0.54Ni0.13Co0.13O2的表面包覆改性研究

Performance of Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_2 as cathode materials for lithium ion batteries by surface coating

采用共沉淀结合固相反应方法合成了富锂的Li1.2Mn0.54Ni0.13Co0.13O2正极材料,并分别以CeO2和AlF3对这种材料进行了表面包覆改性。采用X射线衍射光谱法(XRD)、扫描电子显微镜法(SEM)、透射电子显微镜法(TEM)等方法表征材料的结构和形貌。所合成的球形Li1.2Mn0.54Ni0.13Co0.13O2材料为层状晶体结构。AlF3可以均匀包覆在Li1.2Mn0.54Ni0.13Co0.13O2材料表面,包覆层厚度约为2 nm。AlF3包覆后富锂材料的电化学性能提升效果优于CeO2。AlF3包覆量为1%时,该富锂三元氧化物正极材料的首次充放电效率、容量保持率及倍率性能得到了显著的提高。EIS分析表明,AlF3包覆可避免富锂三元氧化物正极材料与电解液的直接接触,降低了传荷阻抗,从而有效提高了材料的电化学性能。

Layered-Li1.2Mn0.54Ni0.13Co0.13O2 was prepared by co-precipitation and solid state reaction methods. The material could be coated with CeO2 and AIF3 layer. These materials were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscope （TEM）, charge--discharge cycling and electrochemical impedance spectroscopy （EIS）. Li-rich Li1.2Mn0.54Ni0.13Co0.13O2 material was spherical agglomerations with size about 4 μm. The coated AIF3 layer was uniform and the thickness was about 2 nm, which could well enhance the electrochemical performance of pristine Li1.2Mn0.54Ni0.13Co0.13O2. These coating layers could resist the corrosion of cathode materials in electrolyte and could stabilize the interface layer, resulting in reduced interface impedance and improved electrochemical performance.