Dual Role of Niobium(V) for Stabilizing High‐Nickel Cathode Active Materials: Microstructural Control and Doping

ABSTRACT High‐nickel layered oxides are the leading commercial cathode candidates for lithium‐ion batteries, yet their widespread deployment remains constrained by limited cycling stability. Niobium (Nb) coating/doping has emerged as an effective mitigation strategy, but current approaches typically rely on wet‐chemical or gas‐phase routes that are difficult to scale. Herein, we report a dry process that achieves homogeneous Nb 5+ doping into Li 1 Ni 0.83 Mn 0.05 Co 0.12 O 2 by treating the precursor with ultrafine Nb 2 O 5 nanoparticles synthesized via flame spray pyrolysis. With only 0.5 mol.% Nb 5+ , the doped material exhibits improved lattice ordering and refined particle architecture, delivering high capacity up to 211 mAh g −1 , exceptional capacity retention 97% after 100 cycles in half cell, and markedly improved rate capability (170 mAh g −1 at 5C) and long‐term cyclability (83% over 500 cycles at 1C) in full cells. Multiscale structural and chemical analyses reveal the crucial role of ultrafine Nb 5+ addition at the precursor stage in modifying the grain morphology, which ends in homogeneous doping providing mitigation of intergranular cracking and suppression of surface rock‐salt reconstruction, thereby preserving coherent grain boundaries under extended cycling. This work highlights the mechanistic effectiveness of homogeneous Nb 5+ doping via dry process in microstructural control and stabilization of high‐nickel cathodes.