Tracing monoclinic distortion in NCM532 cathode materials by in situ high-energy synchrotron X-ray diffraction

• Published in: Progress in natural science Vol. 34; no. 2; pp. 274 - 279
• Main Authors: Dong, Min, Sun, Qingya, Wang, Zhihua, Rui, Zixin, Zhang, Zhe, Zhu, He, Lan, Si
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 01.04.2024; Center for Neutron Scattering,City University of Hong Kong Shenzhen Research Institute,Shenzhen,518057,China; Herbert Gleiter Institute of Nanoscience,School of Materials Science and Engineering,Nanjing University of Science and Technology,Nanjing,210094,China%School of Mechanical Engineering,Nanjing University of Science and Technology,Nanjing,210094,China%School of Materials Science and Engineering,Henan University of Technology,Zhengzhou,450001,China%Herbert Gleiter Institute of Nanoscience,School of Materials Science and Engineering,Nanjing University of Science and Technology,Nanjing,210094,China; Chinese Materials Research Society
• Subjects: Materials Science; Science & Technology - Other Topics
• ISSN: 1002-0071
• DOI: 10.1016/j.pnsc.2024.02.019

Layered LiNixCoyMnzO2 (NCM) cathode materials have emerged as the best choice for high-energy-density lithium-ion batteries for powering electric vehicles. Despite significant research efforts, the understanding of complex structural dynamics during lithium (de-) intercalation still remains a subject of debate, especially in scenarios where morphology and composition vary. In this study, we carried out in situ high-energy synchrotron X-ray diffraction experiments on commercial NCM523 cathode materials in both single crystal and polycrystalline forms to probe the structural changes during charging and discharging in detail. Our findings reveal that both single crystal and polycrystalline materials exhibit typical H1–H2–H3 phase transitions. However, in polycrystalline NCM532, a monoclinic intermediate phase emerges between the H1 and H2 phases. During this process, symmetry reduces from R-3m to C2/m, which is attributed to a shear distortion along the ab plane. In contrast, for single crystal materials, the H1 phase directly transforms into the H2 phase without the monoclinic phase. The observed monoclinic distortion significantly impacts structural stability and material cycling performance. This study provides new insight into the structural dynamics in NCM532 cathode materials, particularly concerning morphology-dependent behaviors, which could deepen our understanding of the relationship between NCM material structures and their performance.