层状LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2正极材料的多元掺杂改性

Modification of layered LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2 cathode materials with doping multiple components

采用共沉淀法制备锂离子电池掺杂型层状LiNi1/3Co1/3Mn1/3-xMxO2(M=Mg、Al、Cr)正极材料。采用X射线衍射、扫描电镜、充放电实验和交流阻抗实验对LiNi1/3Co1/3Mn1/3-xMxO2正极材料的结构、形貌、电化学性能以及动力学参数进行表征。结果表明:当掺杂量x=0.05时,Mg2+、Al3+掺杂的正极材料在2.8～4.3V、0.1C下的首次放电比容量分别为139.2、151.6mA·h/g,20次循环后的容量保持率分别为98.8%和96.7%;掺杂Mg2+或Al3+均能提高LiNi1/3Co1/3Mn1/3O2的交换电流密度和锂离子扩散系数。结合实验结果和掺杂离子的离子半径和化学稳定性,解释了掺杂离子在LiNi1/3Co1/3Mn1/3O2晶格中的占位及其在充放电过程中的作用。

Layered LiNi1/3Co1/3Mn1/3-xMxO2（M=Mg,Al,Cr） cathode materials for lithium-ion battery were synthesized by co-precipitation method.The structures,morphologies,electrochemical properties and kinetic parameters of the LiNi1/3Co1/3Mn1/3-xMxO2 cathode materials were characterized by X-ray diffractometry（XRD） ,scanning electron microscopy（SEM） ,charge/discharge tests and electrochemical impedance spectroscopy（EIS） .The results show that the LiNi1/3Co1/3Mn1/3-xMxO2 cathode materials（M=Mg^ 2＋,Al^ 3＋;x=0.05） exhibit initial capacity of 139.2 and 151.6 mA·h/g in the voltage range of 2.8-4.3 V,and at 0.1C rate,the capacities retain 98.8%and 96.7%after 20 cycles,respectively.Mg^2 ＋ or Al^3 ＋ doping can enhance the exchange current density and diffusion coefficient of LiNi1/3Co1/3Mn1/3-xMxO2 materials. Based on the ionic radius and chemical stability of doped metal ions,the occupation in the structure and the role of the doped metal ions during charge-discharge cycling were discussed.