Synergistic hybrid coating of Li₃PO₄ and LaPO₄ for high-performance Li-rich Mn-based layered oxide cathodes

A Li₃PO₄/LaPO₄ hybrid phosphate coating layer was constructed on Co-free Li_1.2Mn_0.6Ni_0.2O₂via a solution-assisted low-temperature annealing route to balance surface passivation and interfacial Li⁺ transport. The optimized sample, LLOs-12, delivered an initial coulombic efficiency of 86.06% and a capacity retention of 86.64% after 200 cycles at 1C. Structural and electrochemical analyses indicate that the hybrid phosphate coating layer is mainly located on the particle surface, moderates the high-voltage oxygen-related irreversible process, alleviates post-cycling interfacial polarization, and mitigates surface reconstruction. In addition, LLOs-12 exhibits a higher apparent Li⁺ diffusion coefficient and a thinner reconstructed surface layer than the pristine sample after prolonged cycling. These results suggest that balancing chemical passivation and interfacial ion transport through a hybrid phosphate coating layer is a viable strategy for improving the electrochemical behavior of Co-free Li-rich layered oxide cathodes.