Constructing a Stabilized Interface in Ultra‐High Nickel Single‐Crystal LiNi _0.90 Co _0.05 Mn _0.05 O ₂ by a Long‐Time Molten‐Salt Route

Based on its advantages of high specific capacity, excellent rate capability, and low cost, Nickel-rich layered oxide cathode materials LiNi_xCo_yMn_1-x-yO₂ (Ni-rich NCM, x ≥ 0.9) have become a key choice for the new energy vehicle industry. During electrochemical cycling, however, multiple phase transitions-particularly the detrimental H2-H3 transformation induces abrupt anisotropic lattice distortion along the c-axis. This leads to the formation of microcracks within Ni-rich NCM, which results in the gradual degradation of capacity retention and thermal stability. This study reports an ultra-high nickel cathode material with an in situ stable rock-salt layer constructed on the surface. The NiO rock-salt layer can serve as a covering layer for the material, reducing its direct contact with the electrolyte. Additionally, due to the dispersed primary particles of single-crystal LiNi_0.9Co_0.05Mn_0.05O₂ cathodes (NCM90-S), anisotropic stress change is avoided, and crack formation is effectively suppressed during cycling, demonstrating exceptional cycle performance. Consequently, compared to polycrystalline LiNi_0.9Co_0.05Mn_0.05O₂ cathodes (NCM90-P), NCM90-S achieves superior capacity retention after 300 cycles at 1C (80.2% vs. 60.3%).