Pinning Effects of Heavy Elements for the Structural Stability of Ni-Based Layered Oxides

Ultrahigh-Ni layered oxides enable high-energy lithium-ion batteries (LIBs) but are plagued by lattice collapse, O release, and rapid capacity fade under high temperature and voltage operation. Here, 0.25 mol % Nb and Ta are incorporated into LiNi_0.92Co_0.04Mn_0.04O₂ to elucidate the effect of mass on structural stability. Despite identical oxidation states (+5) and radii (0.64 Å), their mass difference reveals distinct pinning effects. X-ray diffraction and absorption spectroscopy analyses exhibit reduced atomic displacement, reinforced Ni–O bond strength, and expanded Li slab spacing, improving electrochemical performance upon various operating conditions. Moreover, thermal analysis confirms suppressed O release from the lattice structure and a delayed decomposition reaction, with more pronounced stabilization from heavier elements. These findings underscore an atomic-mass-driven materials design strategy as an effective approach for enhancing the durability of ultrahigh-Ni layered cathodes in next-generation LIBs.