Hybrid Doping Strategy with High‐Entropy Cu/Fe Surface Modification and Zr Bulk Incorporation for Ni‐Rich Cathodes

Abstract A hybrid doping strategy combining Zr 4+ bulk doping with high‐entropy Cu 2+ /Fe 3+ surface doping is developed to enhance the structural and interfacial stability of Ni‐rich layered oxide cathodes. Cu and Fe are selectively introduced at the particle surface via a surface‐selective ion‐exchange process, forming a ≈15 nm Fe‐rich layer while preserving the layered framework. Compared to the pristine cathode, the hybrid sample exhibits significantly improved electrochemical performance in both half‐cell and full‐cell configurations. In half‐cells, the hybrid retains 88.5% and 90.2% after 100 cycles at 1C under 4.6 and 4.5 V, respectively. During high‐voltage full‐cell cycling, the hybrid cathode maintains over 80% capacity retention, whereas the pristine counterpart retains less than 10% under identical conditions over the same cycling period. XPS, EELS, and DEMS analyses confirm improved oxygen retention, suppressed gas evolution, and stable surface chemistry, while DFT calculations indicate enhanced Me–O bonding in the selected Fe 0.75 Cu 0.25 (Mn 1/16 Co 2/16 Ni 13/16 )O 2 surface composition, which is identified through DFT‐calculated mixing energy reaching a minimum at this ratio, indicating the most thermodynamically favorable configuration. These results demonstrate the effectiveness of this hybrid doping strategy in mitigating coupled degradation pathways in Ni‐rich cathodes.