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FM: Fachverband Funktionsmaterialien

FM 5: Focus Session: Holistic structural and safety assessment of battery materials and cells

FM 5.10: Vortrag

Montag, 9. März 2026, 17:30–17:45, BEY/0E40

Investigation of Degradation Mechanisms in High-Nickel NMC Cathodes for Lithium-Ion Batteries — •Yosra Dammak — Max Planck Institute for Sustainable Materials, Düsseldorf, Germany

High-nickel layered oxides like NMC955 are attractive cathode materials for lithium-ion batteries. However, their long-term use is often hindered by structural and mechanical degradation during cycling.

This study examined the influence of electrode microstructure and cycling parameters on the performance and degradation of NMC955 cathodes, comparing two average grain sizes: NMC-1.0 (1 micrometer) and NMC-0.5 (0.5 micrometer). The finer-grained NMC-0.5 consistently outperformed NMC-1.0, showing higher specific capacity, better capacity retention, and superior rate capability. Post-mortem analysis indicated that NMC-1.0 suffered from extensive intergranular cracking, while NMC-0.5 particles mostly remained intact. Microstructural analysis (SEM and EBSD) revealed that the coarser NMC-1.0 accumulated higher, heterogeneously distributed strain, especially at the grain boundaries, which promoted fracture. Conversely, the finer NMC-0.5 accommodated strain through more distributed deformation, facilitated by faster grain boundary diffusion. Both grain sizes maintained their layered structure as confirmed by XRD.

In summary, the enhanced electrochemical and microstructural stability of the finer-grained NMC-0.5 is attributed to its ability to manage strain more effectively, contrasting with the strain-induced cracking observed in the coarser NMC-1.0.

Keywords: High-nickel NMC cathode; Grain size; Degradation; Microstructure; Lithium-ion battery