In Situ Surface\nCoatings and Structural Modifications\nfor Reducing Residual Lithium and Stabilizing Lattice on Ultrahigh\nNi Cathodes

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