Influence of Phosphate Surface Coating on Performance of Aqueous-Processed NMC811 Cathodes in 3 Ah Lithium-Ion Cells

Aqueous processing of state-of-the-art cathode materials for lithium-ion batteries like LiNi0.8Mn0.1Co0.1O2 (NMC811) has evolved as a more sustainable and cost-effective alternative to the conventional 1-methyl-2-pyrrolidone-based process. However, the implementation of aqueous processing is challenging due to the water sensitivity of nickel-rich layered oxides. This study investigates the influence of a phosphate-based NMC811 surface coating on the performance of aqueous-processed NMC811 cathodes in 3 Ah cells. The results show that the cells with phosphate-coated NMC811 outperform those with uncoated NMC811, i. e., they exhibited higher initial capacity and improved capacity retention during cycling. Post-mortem characterization techniques reveal that the phosphate coating limits the lithium loss during aqueous cathode manufacturing and further reduces side reactions during cycling, resulting in a smaller increase of cell impedance. A phosphate-based coating on NMC811 protects the material surface during cathode aqueous processing and during cycling in 3 Ah cells. Improved performance, specifically higher initial capacity and improved capacity retention, is obtained with cells containing the phosphate-coated NMC811. Post-mortem analysis reveals that improved surface protection limits loss of lithium during processing and side reactions during cycling. image