Structural, Electronic, Magnetic, and Electrochemical Properties of LiTi₂(PO₄)₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ Cathode Material

The structural, electronic, magnetic, and electrochemical properties of LiTi₂(PO₄)₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ cathode material are studied by x-ray diffraction, scanning electron microscopy, x-ray photoemission, magnetic susceptibility, electrochemical impedance spectroscopy, and charge/discharge profile measurements. Our results reveal that both the pristine and the LiTi₂(PO₄)₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ samples have the same crystal structure and lower cation mixing. The valence values of the elements Ni, Mn, Co, and Ti in the samples are found to be +2, +3, +4, and +4, respectively. Compared with the pristine electrode, the LiTi₂(PO₄)₃-coated electrode exhibits higher capability and better cycling stability. The LiTi₂(PO₄)₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ electrode delivers a high initial capacity of 191.5 mAh g^-1 with a desirable capacity retention ratio of 84.5 % after 100 cycles at 0.5 C. The superior capability and cycling stability of the LiTi₂(PO₄)₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ electrode may be attributed to the reduced charge transfer resistance, enhanced electronic conductivity, increased lithium ion diffusion coefficient, and the protecting effect due to LiTi₂(PO₄)₃ coating.