H$_2$O$_2$-assisted surface coating of nickel-rich NMC cathodes: Impact of the cathode active material and the niobium source

Layered transition metal oxides, particularly those containing nickel, have been widely used as cathode materials and are considered among the most promising options for high-performance lithium-ion batteries. To enhance the cycling and thermal stability of nickel-rich transition metal layered cathodes, surface coating is widely employed in industrial applications. Niobium coating or substitution has shown potential for stabilizing nickel-rich LiNi$_x$Mn$_y$Co$_z$O$_2$ (NMC) cathodes. However, its effectiveness is not universal, as pristine commercial materials are often optimized for direct battery use but sometime are unsuitable for further research due to limited processing information. In our efforts to scale up one of our promising coating methods, we initially turned to a commercially available NMC material. However, our attempts to apply the coating method to a commercial NMC were unsuccessful. We attribute this to unknown post-synthesis processing steps used in the commercial product. To circumvent this limitation and properly evaluate our coating technique, we synthesized our own nickel-rich NMC material, NMC811. Electrochemical testing confirmed that the coating method is effective for lab-synthesized NMC materials and also revealed that differences in the Nb precursor composition, despite the same synthesis grade and high nominal purity, significantly influence the resulting electrochemical performance.