Phosphate-induced surface reconstruction of Li-rich layered cathodes with a spinel lithium phosphate interface

Li-rich manganese-based layered oxides (LRM) are regarded as promising cathode materials for next-generation lithium-ion batteries owing to their high specific capacity. However, their practical application is severely hindered by surface structural degradation, irreversible anionic redox, and sluggish reaction kinetics under high-voltage operation. To address these issues, a phosphate-induced surface reconstruction and interface protection strategy, enabled by potassium dihydrogen phosphate (KH₂PO₄, KDP), is proposed. This approach in situ constructs a spinel-phase transition layer together with an amorphous Li₃PO₄ coating on the particle surface, forming a composite interface with dual functions of structural reconstruction and interfacial stabilization. The engineered interface effectively suppresses electrolyte corrosion and transition-metal dissolution, stabilizes the surface lattice, and regulates the local oxygen coordination environment, thereby enhancing the reversibility of oxygen-related redox reactions and improving interfacial reaction kinetics. As a result, the modified LRM delivers a high initial discharge capacity of 295.3 mAh g^-1 at 0.1C, an improved capacity retention of 81.1% after 200 cycles at 1C (compared to 68.8% for the pristine sample), and a remarkable rate capability of 167 mAh g^-1 at 5C. Mechanistic studies suggest that the spinel phase acts as a structural buffer layer to mitigate lattice distortion and suppress voltage decay, while the amorphous Li₃PO₄ primarily serves as a chemically stable protective layer that reduces interfacial side reactions. This work provides an effective and scalable phosphate-mediated interface engineering strategy for developing high-performance LRM cathodes with enhanced structural stability and electrochemical reversibility.