The demand for large batteries makes the safety issues occurring from the flammable organic electrolytes very important. A solution for such challenges can be utilization of ionic conducting materials as coating layer, which will act not only as a passivation layer, preventing the active material from direct contact with electrolyte, but at the same time can be used as non-flammable solid state electrolytes (SSE). LiNbO3, LATP, LLTO etc. could play such a hybrid role very effective. Especially, LiNbO3 is well known to have a very good structural stability, a high room-temperature lithium ionic (up to 10-2 mS/cm) and low electronic (up to 10-8 mS/cm) conductivity. In addition, this oxide displays such properties not only in the crystalline form, but also in amorphous one, the last one offering more vacancies for lithium ion diffusion and transfer. This is a very important property, because at high temperatures, at which the LiNbO3 crystallises, reaction with the active material might take place. The Ni-rich layered NMC oxides, LiNixMnyCozO2 with x+y+z=1 and x>0.6, are well known cathode materials used in the batteries of electric vehicles. Using a chemically activated coating process a series of NMC622 and NMC811 materials was coated with lithium niobate, resulting in particles with very homogeneous and stable coating layers. The structure of the obtained active materials was investigated using SEM, TEM, XRD, EDX and XPS spectroscopy, and the electrochemical properties of the prepared cathodes were probed by the charge-discharge studies. In addition, it was shown that the crystallinity of the coating material and the temperature, at which the coated material is treated, play an important role and have to be carefully and individually chosen.

Keywords: LiNbO3; NMC811, X-ray diffraction; Cathode materials; Lithium ion batteries