Enhanced battery capacity and cycle life due to suppressed side reactions on the surface of Ni-rich LiNiCoMnO cathode materials coated with Co(PO).

This study explores a strategy to mitigate capacity fading in secondary batteries, which is primarily attributed to side reactions caused by residual Li impurities (LiOH or LiCO) on the surface of Ni-rich LiNiCoMnO (NCM811) layered cathode materials. By applying a 1.5 wt% Co(PO) coating, we successfully formed a thin and stable LiF cathode-electrolyte interface (CEI) layer, which resulted in decreased battery resistance and enhanced diffusion of Li ions within the electrolyte. This coating significantly improved the interface stability of NCM811, leading to superior battery performance. Specifically, the discharge capacity of uncoated NCM811 was 190 mA h g at a charge of 4.3 V and a rate of 0.1C, whereas the 1.5Co(PO)/NCM811 exhibited an increased capacity of 213 mA h g. Furthermore, the Co(PO) coating effectively reduced the levels of LiOH and LiCO on the NCM811 surface to only 0.1 %, thereby minimizing adverse side reactions with the electrolyte salt (LiPF), cation mixing between Ni and Li, and defects at the NCM811 interface. As a result, battery lifespan was significantly extended. This study presents a robust approach for enhancing battery stability and performance by efficiently reducing residual Li ions on the surface of NCM811 through strategic Co(PO) coating.