Sb₂O₃-modified LiNi_1/3Co _1/3Mn_1/3O₂ material with enhanced thermal safety and electrochemical property

The layered LiMO₂ (M = Ni, Co and Mn) materials LiNi _1/3Co_1/3Mn_1/3O₂ and LiNi _0.4Co_0.2Mn_0.4O₂ are synthesized by rheological phase method. Sb₂O₃-modified phases are further obtained by mechanical ball milling treatment. The structure and morphology of the bare and modified samples are characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Charge/discharge tests indicate that the modified phases all improve cycling stability, rate capability and thermal safety. Careful comparison of the charge/discharge profiles reveals that the serious polarization increment in cycling is suppressed in the Sb₂O₃-modified LiMO ₂ electrodes. AC impedance shows that Sb₂O ₃/LiNi_1/3Co_1/3Mn_1/3O₂ electrode has smaller R_ct and R_f value. Further analysis proves that Sb₂O₃ hinders the reaction between electrolyte and cathode during charge/discharge process and helps to stabilize the SEI. Other experiments prove that using Sb₂O₃-coated separator can achieve similar positive effect on layered LiMO₂ cathode.