High-valence Mo Doping Inducing Radial Primary Particles for High-Performance Ultra-High-Nickel NCMA Cathodes

The ultrahigh-nickel quaternary cathode material LiNi 1-x-y-z Co x Mn y Al z O 2 (1-x-y-z ≥ 0.9, NCMA) combines the complementary advantages of its ternary counterparts, LiNi x Co y Mn z O 2 (x≥0.9, NCM) and LiNi x Co y Al z O 2 (x≥0.9, NCA). Benefiting from its high specific capacity and exceptional rate capability, the NCMA cathode has attracted widespread attention as a promising candidate for the high-end energy storage market. However, oversized primary particles typically exacerbate internal stress, leading to secondary particle pulverization and microcrack propagation, which severely degrade cycling stability and trigger capacity fade. To address these limitations, this study introduces Mo 6+ doping into NCMA to guide the radial growth of primary particles, resulting in a distinct elongated, rod-shaped morphology. This structural modification effectively shortens Li + transport pathways and mitigates internal-stress-induced microcracks. Concurrently, the dual roles of Mo are elucidated: its incorporation into the bulk lattice induces lattice expansion that widens Li + diffusion channels, while its segregation at grain boundaries restricts grain growth and fosters the radial morphology. This synergistic effect significantly accelerates Li + transport kinetics during cycling. Consequently, the optimized Mo-doped NCMA delivers a high reversible capacity of 213.5 mAh·g -1 at 0.2   C, 134.9 mAh·g -1 at 10   C, and a 94.9% retention rate after 100 cycles at 1   C. Furthermore, its practical viability was further assessed in a full-cell configuration, which maintained stability over 500 cycles and delivered 72.13% capacity retention. Overall, the Mo 6+ doping strategy successfully enhances the electrochemical performance of NCMA, offering a promising avenue for the modification of ultrahigh-nickel quaternary cathode materials.