High-entropy doping coupled with LiNbO3 coating synergistically enhances the cycling stability of single-crystal high-nickel cathode materials

High-nickel layered material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is one of the most promising cathode materials for lithium-ion batteries because of its high specific capacity, low cost, and high working voltage. However, issues such as internal structure collapse and interface side reactions during long-term cycle hinder its practical application. In this study, Al, B, La, Nb, and Zr are selected for high-entropy doping of single-crystal NCM811 (SNCM811). Individual doping elements offer distinct advantages in optimizing the morphology, crystal structure, and lithiation/delithiation performance. A portion of the introduced Nb is uniformly coated on the material surface as LiNbO 3 . The resulting material, modified by high-entropy doping coupled with a LiNbO 3 coating (HE-SNCM811) exhibits a capacity retention of 91.5% after 100 cycles at 1 C in the voltage range of 2.7–4.3 V, which is significantly higher than the 73.6% retention of the pristine sample. At 10 C, HE-SNCM811 delivers a reversible specific capacity of 152.82 mAh‧g −1 which is 17.26 mAh‧g −1 higher than that of the pristine sample. The first-principles calculations are performed on the crystal structures of the pristine sample and the heterojunction structure formed between the high-entropy doped bulk phase and the LiNbO 3 coating. Compared to SNCM811, HE-SNCM811, exhibits a 0.18 eV reduction in the Li + migration energy barrier, along with an enlarged Li layer spacing and a reduced transition metal (TM) layer spacing. This enhanced Li + diffusion kinetics and stabilizes the microstructure of the material. The high-entropy modification widens the Li + transmission channel, strengthens the TM–O bonds, and effectively suppresses the irreversible H2–H3 phase transition. Additionally, the LiNbO 3 coating, as a fast ionic conductor, physically isolates the electrolyte, reduces HF attack, and prevents degradation of the cathode surface. This study offers a research approach for developing high-capacity and long-cycle cathode materials for lithium-ion batteries. Graphical abstract In this work, Al, B, La, Nb and Zr are introduced as high-entropy dopants, while Nb partially forms a LiNbO 3 coating on the surface, yielding the HE-SNCM811 cathode material. The modified sample exhibits high rate capability and stable cycling performance. First-principles calculations reveal a lower Li + migration barrier and a higher Li + diffusion rate in the high-entropy modified sample.