Defect Engineering via Li2CeO3 Oxygen-Vacancy Coating: Dual Optimization of Structural Integrity and Lattice Oxygen Stability in High-Nickel Cathodes.

High-nickel layered oxide LiNixCoyMn1-x-yO2 (NCM, x ≥ 0.8) materials are considered optimal cathodes for lithium-ion power batteries owing to their high energy density, commendable cycling performance, and cost-effectiveness. However, structural collapse and interface instability during cycling result in diminished cycling stability, significantly hindering their commercial viability. This study reports a strategy to improve the stability of the cathode structure and suppress surface degradation of high-nickel NCMs by introducing LCO (Li2CeO3) coatings. The LCO coating provides a stable surface structure and enhances structural stability under high Li-extraction conditions, significantly mitigating the formation of unstable cathode-electrolyte interfaces and reducing electrolyte corrosion and side reactions. Meanwhile, the partially bulk-phase doped Ce4+ primarily optimizes the lattice parameters by modulating the crystal structure and altering the electronic environment of the transition metal layer, which promotes the Li+ diffusion kinetics and effectively suppresses the bulk expansion and irreversible phase transition. As expected, the modified cathode exhibits superior improvements in rate performance and cycling stability, with an initial discharge capacity of 202.5 mA h g-1 and a first-cycle Coulombic efficiency of 95.4%, compared to 89% for pristine NCM. Notably, 1.0%-LCO@NCM maintains a capacity retention of 83.52% after 200 cycles at 1.0 C, significantly higher than the 65.29% retention of pristine NCM under the same conditions. Furthermore, 1.0%-LCO@NCM consistently demonstrates lower interfacial impedance and higher Li+ diffusion coefficients throughout the cycling process. After 200 cycles, its impedance remains lower, with reduced interfacial film impedance. The oxygen vacancy-rich surface LCO achieves dual optimization of the structural integrity and oxygen redox activity of the high-Ni cathode, further improving cycle life and multiplier performance.