Recent progress in tailoring Ni-rich layered oxides via coating and doping strategies for enhanced lithium-ion battery performance

Nickel-rich layered oxide cathodes, typified by compositions such as LiNi₁₋ₓ₋ᵧCoₓMnᵧO₂ (NCM) have garnered significant attention as high-energy-density candidates for next-generation lithium-ion batteries. However, their widespread deployment is hindered by a confluence of structural degradation, surface instability, and poor interfacial compatibility under high voltage cycling. To address these multifaceted limitations, this review comprehensively examines recent advances in surface coating and bulk doping strategies, which have emerged as pivotal approaches for enhancing the electrochemical stability and longevity of Ni-rich cathodes. Surface coatings including oxides, phosphates, and fluorides have been shown to effectively mitigate electrolyte-induced parasitic reactions and reinforce cathode–electrolyte interfaces. Simultaneously, elemental doping at transition-metal, lithium, and oxygen sites offer promising pathways to suppress cation disorder, stabilize layered frameworks, and facilitate Li⁺ transport. Emphasis is placed on site-specific doping mechanisms, the role of multi-site (co-)doping, and their synergistic interplay with surface modification layers. By synthesizing recent findings, this review delineates how the judicious integration of coating and doping techniques can enable the rational design of Ni-rich cathodes with enhanced structural integrity, rate capability, and cycle life.