Depth-dependent valence stratification driven by oxygen redox in lithium-rich layered oxide

• Published in: Nature communications Vol. 11; no. 1; p. 6342
• Main Authors: Zhang, Jin, Wang, Qinchao, Li, Shaofeng, Jiang, Zhisen, Tan, Sha, Wang, Xuelong, Zhang, Kai, Yuan, Qingxi, Lee, Sang-Jun, Titus, Charles J., Irwin, Kent D., Nordlund, Dennis, Lee, Jun-Sik, Pianetta, Piero, Yu, Xiqian, Xiao, Xianghui, Yang, Xiao-Qing, Hu, Enyuan, Liu, Yijin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.12.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/299/891; 639/4077/4079/891; 639/638/161/891; Anions; Batteries; Cations; Cobalt; ENERGY STORAGE; Flux density; Humanities and Social Sciences; Induced voltage; Layered materials; Lithium; Lithium-ion batteries; lithium-rich layered; Manganese; Morphology; multidisciplinary; Multilayers; Nickel; Oxygen; Particle decay; Rechargeable batteries; Redox properties; Science; Science (multidisciplinary); spectro-imaging; Transition metals; Voltage
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-20198-w

Lithium-rich nickel-manganese-cobalt (LirNMC) layered material is a promising cathode for lithium-ion batteries thanks to its large energy density enabled by coexisting cation and anion redox activities. It however suffers from a voltage decay upon cycling, urging for an in-depth understanding of the particle-level structure and chemical complexity. In this work, we investigate the Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 particles morphologically, compositionally, and chemically in three-dimensions. While the composition is generally uniform throughout the particle, the charging induces a strong depth dependency in transition metal valence. Such a valence stratification phenomenon is attributed to the nature of oxygen redox which is very likely mostly associated with Mn. The depth-dependent chemistry could be modulated by the particles’ core-multi-shell morphology, suggesting a structural-chemical interplay. These findings highlight the possibility of introducing a chemical gradient to address the oxygen-loss-induced voltage fade in LirNMC layered materials. Lithium-rich layered material deserves in-depth understanding because it has large capacity enabled by both cation and anion activities. Here, authors apply 3D spectro-tomography with nano resolution to reveal the multi-layer morphology and depth-dependent transition metal valence distribution associated with oxygen redox.