Multifunctional Surface Engineering of Ni-Rich Layered Cathodes for Ultra-Stable Lithium-Ion Batteries

Nickel-rich layered LiNi_xCo_yMn_zO₂ (NCM, x $\ge$ 0.6) cathodes have been widely used for high-energy-density lithium-ion batteries (LIBs), delivering exceptional capacity $(\ge$ 200 mAh g^-1) and remarkable cost-efficiency. Nevertheless, structural degradation (e.g., oxygen vacancy formation, transition metal dissolution) and interfacial instability (side reactions) under high-voltage operation ( $>$ 4.3 V) severely limit their cycle life. Recent advances demonstrate that precisely engineered surface coatings can synergistically address these limitations through suppressing parasitic reactions, stabilizing lattice frameworks, and enhancing Li⁺ transport kinetics. This review provides a multidimensional analysis of coating engineering for NCM cathodes, focusing on the mechanism insights, innovative designs, and synthesis route. Notably, this work emphasizes emerging opportunities within underexplored research areas, specifically artificial intelligence-enabled coating architectures and sustainable large-scale synthesis methodologies. By systematically integrating fundamental mechanistic insights with practical engineering perspectives, a robust framework to accelerate the utilization of NCM cathodes as ultra-stable and safe energy storage systems is established in this review.