<p>Ultra-high nickel layered oxides, such as LiNi_0.9Co_0.05Mn_0.05O₂ (NCM), are widely regarded as one of the most promising cathode materials for high-energy-density lithium-ion batteries (LIBs). However, their poor electrochemical cycling stability and high sensitivity to moisture in the air significantly hinder practical applications. Herein, this work introduces a self-assembled multifunctional hydrophobic molecular layer based on (pentafluorophenylpropyl)trimethoxysilane (PFPPS) by simple one-step self-assembly strategy, simultaneously removing residual lithium, creating an <i>in-situ</i> coating, and establishing a protective hydrophobic layer. The outer highly fluorinated molecular structure imparts exceptional hydrophobicity, significantly increasing the water contact angle from 19.4° to 96.3°, which effectively mitigates Li⁺/H⁺ exchange and greatly enhances the air-storage stability. Additionally, the electron-withdrawing effect of fluorine groups suppresses the dissolution of transition metal ions, while the LiF functional layer improves lithium-ion conductivity and enhances phase transition reversibility during cycling. After 7 days of air exposure, the modified NCM still delivers an impressive specific capacity of 218.2 mAh g⁻¹ at 0.2 C in the first cycle, vastly outperforming the 157.1 mAh g⁻¹ of the unmodified sample. This work presents an effective and scalable approach to significantly enhance the environmental and electrochemical stability of ultra-high nickel cathode, offering substantial potential to accelerate their practical applications.</p>