Industrial modification comparison of Ni-Rich cathode materials towards enhanced surface chemical stability against ambient air for advanced lithium-ion batteries

Abstract

Ni-rich layered oxides (e.g. LiNi0.8Co0.1Mn0.1O2, denoted as NCM811) with high capacity and moderate cost are promising cathodes for high energy density Li-ion batteries. However, the highly chemical sensitivity to H2O and CO2 triggers the serious surface degradation when exposed to ambient air, which becomes an intractable obstacle for the large-scale production and application of Ni-rich cathodes. Herein, we comprehensively evaluate the effects of three industrial treatment strategies, including washing, washing–reheating, and washing–boron oxide coating–reheating, on the air stability, slurry processability and electrochemical performance of NCM811 cathodes. It is demonstrated that the slurry processability can be greatly improved by water washing. However, water washing leads to more inferior air stability, which can be restored via a post-heating treatment. Impressively, with the aid of B2O3 protective coating nanolayer, the thickening of surface degradation-induced passive layers is significantly suppressed that effectively prevents the detrimental surface phase transformation, thereby extending the ambient storage life and avoiding the slurry gelation. More importantly, B2O3 coated NCM811 cathode exhibits the low interfacial reaction resistance and excellent cyclic stability even after 8 weeks air exposure. This work paves the road for the industrial surface treatment of Ni-rich cathode materials, and deepens the understanding of surface stabilization mechanisms under practical application conditions.