In Situ Surface Coatings and Structural Modifications for Reducing Residual Lithium and Stabilizing Lattice on Ultrahigh Ni Cathodes

Ultrahigh nickel layered oxides are promising next-generation cathode materials that have attracted significant research interest. However, their high nickel content leads to substantial residual lithium on the surface, affecting cycling performance and material safety. Here, we introduce Y element modification to control the material’s interface and lattice structure. Y(NO 3 ) 3 was mixed with LiNi 0.90 Co 0.05 Mn 0.05 O 2, dissolved in ethanol, and calcined at low temperature to form a LiYO 2 coating layer and incorporate Y 3+ into the lattice. This coating layer reduces residual lithium compounds on the surface and minimizes sensitivity to air, while Y 3+ doping enhances lattice stability. The NCM-Y(NO 3 ) 3 material demonstrates superior electrochemical performance, with an initial discharge specific capacity of 213.36 mAh·g –1 at 0.1C within a voltage range of 2.7–4.3 V. After 100 cycles at 1C within the same voltage window, the discharge specific capacity retention remains high at 81.65%.