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 Li 3 PO 4 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 Ni 2+ migration and occupation within the Li layer. The Li 3 PO 4 surface coating layer acts as an electrochemical shield, protecting against interfacial side reactions and enhancing the Li + diffusion rate. As a result, the LiNi 0.95 Mn 0.05 O 2 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.