Enhancing Structural Stability and Electrochemical Performance of Ultra-high Ni-rich Co-free Cathode via MgHPO₄ Dual-functional Modification

Ultra-high nickel layered cathodes (Ni⩾95%) have emerged as prospective candidates for next-generation lithium-ion batteries (LIBs) due to their exceptional specific capacity and cost-effectiveness. However, the commercial application of these cathodes has been hindered by several challenges, including structural instability during cycling, high sensitivity to air, and slow Li⁺ migration. In this research, a one-step modification strategy was developed to simultaneously achieve Mg doping and Li₃PO₄ layer coating for the ultra-high nickel cathodes. Characterization results demonstrated that Mg doping not only alleviates lattice strain changes during the H2–H3 phase transition (H2: the second hexagonal phase; H3: the third hexagonal phase) but also serves as a structural anchor, preventing Ni²⁺ migration and occupation within the Li layer. The Li₃PO₄ surface coating layer acts as an electrochemical shield, protecting against interfacial side reactions and enhancing the Li⁺ diffusion rate. As a result, the LiNi_0.95Mn_0.05O₂ cathode, with both internal and external modifications, demonstrates significant improvement in cycling stability (85.7% capacity retention after 100 cycles) and Li⁺ transport performance (130.6 mA·h·g⁻¹ at 10 C, 1 C=189.6 mA·h·g⁻¹), providing a solid foundation for the further development and application of ultra-high nickel cathodes.