Enhancing structural integrity and long-term cycling stability of high-voltage single-crystalline Ni-rich cathodes via surface/subsurface dual-functional modification engineering

Single-crystalline Ni-rich cathodes are promising candidates for next-generation lithium-ion batteries owing to their exceptional cycling stability and safety. However, challenges such as slow Li⁺ diffusion kinetics, interfacial side reactions and irreversible surface reconstruction during prolonged cycling persist. To address these issues, we simultaneously constructed a protective NASICON-type Li_1.3Y_0.3Zr_1.7(PO₄)₃ (LYZP) coating with Zr gradient doping on the surface/subsurface of single-crystalline LiNi_0.83Co_0.11Mn_0.06O₂ (SCNCM83) through a one-step high-temperature sintering process. Comprehensive characterizations and density functional theory calculations confirm that the dual-functional modification effectively improves H2-H3 phase transformation reversibility, reduces surface lattice oxygen activity, alleviates interfacial parasitic reactions, and suppresses disordered rock-salt phase generation, thereby enhancing interfacial stability and structural integrity. Moreover, the synergistic effect of the LYZP fast ion conductor coating, which increases Li⁺ conductivity, and near-surface Zr doping that widens interlayer spacing, facilitates the Li⁺ transport between the single-crystalline particles, resulting in improved rate capability. Impressively, the LYZP-modified SCNCM83 achieves superior cycling stability (77.3 % after 200 cycles at 1 C) and satisfactory rate capability (171.8 mAh g^-1 at 5 C), even at an ultra-high cut-off voltage of 4.5 V. Furthermore, the full-cell using LYZP-modified SCNCM83 demonstrates exceptional long-term cycle stability (83.7 % after 500 cycles at 0.5 C), highlighting its potential for commercial applications.