Center of Materials Science and Optoelectronics Engineering, College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing, 100190, P. R. China.
Adv Sci (Weinh). 2023 Mar;10(9):e2206442. doi: 10.1002/advs.202206442. Epub 2023 Jan 25.
Despite the low cost and high capacity of Ni-rich layered oxides (NRLOs), their widespread implementation in electric vehicles is hindered by capacity decay and O release. These issues originate from chemo-mechanical heterogeneity, which is mainly related to oxygen anion redox (OAR). However, what to tune regarding OAR in NRLOs and how to tune it remains unknown. In this study, a close correlation between the OAR chemistry and Li/Ni antisite defects is revealed. Experiments and calculations show the opposite effects of aggregative and dispersive Li/Ni antisite defects on the NiO configuration and Ni spin state in NRLOs. The resulting broad or narrow spans for the energy bands caused by spin states lead to different OAR chemistries. By tuning the Li/Ni antisite defects to be dispersive rather than aggregative, the threshold voltage for triggering OAR is obviously elevated, and the generation of bulk-O -like species and O release at phase transition nodes is fundamentally restrained. The OAR is regulated from irreversible to reversible, fundamentally addressing structural degradation and heterogeneity. This study reveals the interaction of the Li/Ni antisite defect/OAR chemistry/chemo-mechanical heterogeneity and presents some insights into the design of high-performance NRLO cathodes.
尽管富镍层状氧化物 (NRLOs) 具有低成本和高容量的优势，但它们在电动汽车中的广泛应用受到容量衰减和 O 释放的阻碍。这些问题源于化学机械异质性，主要与氧阴离子氧化还原 (OAR) 有关。然而，NRLOs 中的 OAR 需要调整什么以及如何调整仍然未知。在这项研究中，揭示了 OAR 化学与 Li/Ni 反位缺陷之间的密切关系。实验和计算表明，聚集和分散的 Li/Ni 反位缺陷对 NRLOs 中 NiO 结构和 Ni 自旋态的影响相反。自旋态导致能带的宽或窄范围不同，从而导致不同的 OAR 化学。通过将 Li/Ni 反位缺陷调制成分散而不是聚集的状态，可以明显提高触发 OAR 的阈值电压，从根本上抑制了 O 类似物质的产生和相变节点处的 O 释放。OAR 从不可逆调节为可逆，从根本上解决了结构退化和异质性问题。本研究揭示了 Li/Ni 反位缺陷/OAR 化学/化学机械异质性的相互作用，并为高性能 NRLO 正极的设计提供了一些思路。
