Rare-earth co-doping promotes high-capacity and long-cycle Ni-rich layered oxide cathodes via lattice stabilization and interface engineering

Abstract

Ni-rich layered oxide cathodes are promising candidates for next-generation high-energy-density lithium-ion batteries owing to their high capacity and cost-effectiveness. However, their widespread application is hindered by structural instability, interfacial side reactions, lattice distortion, and microcrack formation during cycling. Herein, a previously unreported synergistic dual rare-earth (Yb/Y) co-doping strategy is proposed for a LiNi_0.9Co_0.05Al_0.05O₂ (NCA) cathode to simultaneously stabilize the bulk crystal structure and the electrode–electrolyte interface. Combined experimental results and density functional theory (DFT) analyses demonstrate that Yb/Y incorporation into transition-metal sites effectively enlarges Li⁺ diffusion pathways, suppresses Li⁺/Ni²⁺ cation disorder, and stabilizes lattice oxygen through strong Yb/Y–O bonds, thereby mitigating bulk structural degradation. In addition, a uniform, dense, and mechanically robust cathode–electrolyte interphase (CEI) is formed in situ, effectively mitigating electrolyte corrosion, lowering the interfacial resistance, and suppressing particle cracking for NCAYbY. Consequently, the modified NCAYbY cathode exhibits outstanding electrochemical performance, delivering a high reversible capacity of 222.8 mA h g⁻¹ at 0.2C with 95.79% capacity retention after 100 cycles. Remarkably, the corresponding full cell retains 78.35% capacity after 700 cycles at 1C, while a pouch cell exhibits an initial discharge capacity of ∼900 mA h with 78.60% retention after 300 cycles. This work establishes dual rare-earth co-doping as an effective and practical design principle for realizing structurally and interfacially robust Ni-rich cathodes for high-performance, long-life lithium-ion batteries.