Surface modification of LiCo_1/3Ni_1/3Mn _1/3O₂ by TiO₂-coating

A method to improve the cycling performance of LiCo_1/3Ni _1/3Mn_1/3O₂ in lithium-ion batteries by coating with TiO₂ using an in-situ dipping and hydrolyzing method was presented in this work. The effect of the TiO₂ coating on the structure and electrochemical properties of LiCo_1/3Ni _1/3Mn_1/3O₂ was investigated using X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and galvanostatic charge/discharge testing. TiO₂ forms a layer on the surface of LiCO_1/3Ni_1/3Mn_1/3O₂ without destroying the structure of the core material. The TiO₂Coated LiCo_1/3Ni_1/3Mn_1/3O₂ possesses better rate capability and cyclability than the uncoated material. The capacity of the TiO₂-coated material at 5.0C (1.0C=160 mȦg^-1) reaches 66.0% of that achieved at 0.2C, while the capacity of the uncoated LiCo_1/3Ni_1/3Mn_1/3O₂ obtains a value of only 31.5%. The rate of capacity retention after 12 cycles at 2.0C for the coated sample is about 100%, which is much better than that of the uncoated material (94.4%). EIS shows that the reason for this improvement in the capacity of the coated material is the enhanced interface stability during cycling. XRD and ICP-OES tests taken after cycling indicate that the TiO₂-coating can enhance the structural stability of LiCo_1/3Ni _1/3Mn_1/3O₂.