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

ABSTRACT Based on its advantages of high specific capacity, excellent rate capability, and low cost, Nickel‐rich layered oxide cathode materials LiNi x Co y Mn 1−x−y O 2 (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 0.9 Co 0.05 Mn 0.05 O 2 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 0.9 Co 0.05 Mn 0.05 O 2 cathodes (NCM90‐P), NCM90‐S achieves superior capacity retention after 300 cycles at 1C (80.2% vs. 60.3%).