Revisiting Primary Particles in Layered Lithium Transition‐Metal Oxides and Their Impact on Structural Degradation

Journal Article · 24 January 2019 · Advanced Science

DOI: https://doi.org/10.1002/advs.201800843 · OSTI ID:1492094

Lee, Seung‐Yong ^[1]; Park, Gyeong‐Su ^[2]; Jung, Changhoon ^[3]; Ko, Dong‐Su ^[3]; Park, Seong‐Yong ^[3]; Kim, Hee Goo ^[3]; Hong, Seong‐Hyeon ^[2]; Zhu, Yimei ^[4]; Kim, Miyoung ^[2]

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1. Department of Materials Science and Engineering and Research Institute of Advanced Materials Seoul National University Seoul 08826 Republic of Korea, Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory Upton NY 11973 USA
2. Department of Materials Science and Engineering and Research Institute of Advanced Materials Seoul National University Seoul 08826 Republic of Korea
3. AE Group Platform Technology Lab Samsung Advanced Institute of Technology Suwon‐si Gyeonggi‐do 443‐803 Republic of Korea
4. Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory Upton NY 11973 USA

Abstract Layered lithium transition‐metal oxide materials, e.g., Li(Ni _{1− x − y} Co _x Mn _y )O ₂ (NCM) and Li(Ni _{1− x − y} Co _x Al _y )O ₂ , are the most promising candidates for lithium‐ion battery cathodes. They generally consist of ≈10 µm spherical particles densely packed with smaller particles (0.1–1 µm), called secondary and primary particles, respectively. The micrometer‐ to nanometer‐sized particles are critical to the battery performance because they affect the reaction capability of the cathode. Herein, the crystal structure of the primary particles of NCM materials is revisited. Elaborate transmission electron microscopy investigations reveal that the so‐called primary particles, often considered as single crystals, are in fact polycrystalline secondary particles. They contain low‐angle and exceptionally stable special grain boundaries (GBs) presumably created during aggregation via an oriented attachment mechanism. Therefore, this so‐called primary particle is renamed as primary‐like particle. More importantly, the low‐angle GBs between the smaller true primary particles cause the development of nanocracks within the primary‐like particles of Ni‐rich NCM cathodes after repetitive electrochemical cycles. In addition to rectifying a prevalent misconception about primary particles, this study provides a previously unknown but important origin of structural degradation in Ni‐rich layered cathodes.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: SC0012704
• OSTI ID: 1492094
• Report Number(s): BNL--211779-2019-JAAM; 1800843
• Journal Information: Advanced Science, Journal Name: Advanced Science Journal Issue: 6 Vol. 6; ISSN 2198-3844
• Publisher: Wiley Blackwell (John Wiley & Sons)Copyright Statement
• Country of Publication: Germany
• Language: English