High‐Entropy Doping Strategy for Ultra‐Stable Upcycling of Spent High‐Nickel Cathodes

ABSTRACT The growing demand for lithium‐ion batteries has intensified the need for sustainable recycling methods, particularly for high‐nickel cathode materials, which suffer from structural instability during upcycling. This study introduces a high‐entropy doping strategy to stabilize upcycled Ni‐rich cathodes (HE‐NCM811) by incorporating multiple dopants to maximize configurational entropy. Advanced characterization techniques, including in situ XRD, XANES, and cross‐sectional TEM, reveal that high‐entropy doping significantly suppresses irreversible lattice variations along the c‐axis, mitigates microcracking, and maintains stable coordination environments for (Ni, Co, Mn)─O and (Ni, Co, Mn)─Ni bonds during cycling. The optimized HE‐NCM811 cathode exhibits exceptional electrochemical performance, with an ultra‐low capacity decay rate of 0.032% per cycle at 5 C over 1000 cycles. The enhanced stability is attributed to reduced polarization, improved electronic conductivity, and minimized anisotropic lattice strain. These findings demonstrate that high‐entropy doping not only addresses the structural degradation challenges in upcycled Ni‐rich cathodes but also provides a universal approach for designing next‐generation high‐performance cathode materials, including NCM, NCA, and NMA systems. This work not only provides a sustainable solution for spent battery upcycling but also opens avenues for designing zero‐cobalt, high‐performance cathodes. Scaling this technology requires optimizing dopant recovery from spent batteries to close the material loop.