High-Entropy Rock-Salt\nSurface Layer Stabilizes the\nUltrahigh-Ni Single-Crystal Cathode

Single-crystalline Ni-rich layered oxides are one of\nthe most promising\ncathode materials for lithium-ion batteries due to their superior\nstructural stability. However, sluggish lithium-ion diffusion kinetics\nand interfacial issues hinder their practical applications. These\nissues intensify with increasing Ni content in the ultrahigh-Ni regime\n(≥90%), significantly threatening the practical viability of\nthe single-crystalline strategy for ultrahigh-Ni layered oxide cathodes.\nHerein, by developing a high-entropy coating strategy, we successfully\nconstructed an epitaxial lattice-coherent high-entropy rock-salt layer\n(∼3 nm) via Zr and Al doping on the surface of the single-crystalline\ncathode LiNi<sub>0.92</sub>Co<sub>0.05</sub>Mn<sub>0.03</sub>O<sub>2</sub> through an <i>in situ</i> modification process.\nThe surface high-entropy rock-salt layer with tailored Ni valence\nand lattice coherence not only greatly improves lithium-ion diffusion\nkinetics but also suppresses interface parasitic reactions and surface\nstructural degradations. The high-entropy surface layer-stabilized\nultrahigh-Ni single-crystalline cathode (SC-Ni92-ZA) demonstrates\nsignificantly improved rate and cycling performances (127.5 mAh g<sup>–1</sup> at 20C, capacity retention of 74.9% after 500 cycles\nat 1C) in a half-cell. The SC-Ni92-ZA exhibits a capacity retention\nof 87.1% after 600 cycles at 1C in a full-cell. This epitaxial lattice-coherent\nhigh-entropy coating strategy develops a promising avenue for developing\nhigh-capacity, long-life cathode materials.