Hydrophobic surface coating against chemical environmental instability for Ni-rich layered oxide cathode materials

[Display omitted] •Ni-rich materials with an effective surface coating by a simple and scalable method.•The as-prepared material show an excellent chemical stability and cycling performance.•The outer coating can inhibit the adverse chemical reaction and improve its stability.•The inner coating could beneficial to the transport of Li+ in the NCM material.•This work can be further expanded to other types of air-sensitive electrode materials. Ni-rich layered oxide LiNi0.8Co0.1Mn0.1O2 (NCM) as a most promising cathode material for Li-ion batteries suffers easily from the deterioration of electrochemical performance during storage because of the chemical environmental instability. Herein, a simple and scalable strategy is reported to overcome these issues by a hydrophobic coating with dihexadecyl phosphate (DHP) on NCM particle surface, which is composed of an outer-layer hydrophobic alkyl surface and an inner-layer phosphate-based coating with O=POLi covalent bonds. The former layer can alleviate the absorption of H2O/CO2 on the particle surface in the humid environment, and the later can improve Li+ transportation coefficient during charge–discharge process. As a result, profiting from these two synergistic effects, the DHP-coated NCM shows excellent rate performance and cycling stability, particularly, after 14 days of exposure to air, the DHP-coated NCM delivers the initial capacity of 168.7 mAh g−1 at 2 C rate, but only 134.7 mAh g−1 for the pristine NCM. This work provides an effective approach to improve the environmental stability in Ni-rich layered oxide cathodes.