A novel strategy of bulk-surface Al/Ti continuous modification for improving structural stability and electrochemical performance of ultra-high-nickel cathode materials

Ultra-high‑nickel layered oxide cathode materials are considered key candidates for next generation high-energy-density lithium-ion batteries due to their remarkable specific discharge capacity. However, its extremely high nickel content results in severe structural degradation and interfacial side reactions during cycling, thus restricting its practical application. This work proposes a novel bulk-surface Al/Ti continuous modification strategy. Through this strategy, Al and Ti are co-doped into the bulk phase of NCM955, while a fast-ion-conducting solid electrolyte, Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP), is coated on the surface. The modified NCM955 delivers a high reversible capacity of 223.09 mAh/g at 0.1C (2.7–4.3 V) with excellent initial coulombic efficiency. After 100 cycles at 1C, the capacity retention and remaining capacity reach 90.18% and 183.44 mAh/g, and the capacity retention after 100 cycles in a full cell is 93.29%. Even after 100 cycles at a high rate of 10C, it retains 97.3% of its capacity. Bulk Al/Ti doping strengthens the transition metal‑oxygen bond energy, effectively suppressing lattice oxygen loss and inhibiting Ni 2+ migration. As a result, it reduces cation mixing and prevents structural deterioration during cycling. Simultaneously, the surface LATP coating enhances interfacial Li + diffusion kinetics, serves as a physical barrier against side reactions with air and electrolyte, and helps compensate for active lithium loss during cycling. This work demonstrates that the bulk-surface Al/Ti continuous modification strategy, achieved through synergistic Al/Ti co-doping and LATP coating, offers an effective approach to enhance the structural stability and electrochemical performance of ultra-high‑nickel cathode materials.