SKM 2023 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 5: Materials in Energy Conversion: Mechanical Properties and Solid State Batteries

MM 5.3: Vortrag

Montag, 27. März 2023, 10:45–11:00, SCH A 215

Planar gliding and vacancy condensation: The role of dislocations in the chemomechanical degradation of layered transition metal oxides — •Marcel Sadowski¹, Karsten Albe¹, and Sabrina Sicolo² — ¹Technical University of Darmstadt, Darmstadt, Germany — ²BASF SE, Ludwigshafen, Germany

Stacking faults driven by dislocations have been observed in layered transition metal oxides cathodes both in cycled and uncycled materials. The reversibility of stacking-sequence changes directly impacts the material performance. Irreversible glide due to lattice invariance or local compositional changes can initiate a catastrophic sequence of degradation mechanisms. In this study we compare the chemomechanical properties of LiCoO₂ and LiNiO₂ by combining density functional theory (DFT) and anisotropic linear elasticity theory. We calculate stacking fault energies as a function of Li content and quantify the “pillar effect” of excess Ni in hindering stacking-sequence changes. We then characterize screw dislocations, which mediate stacking-sequence changes, and find a peculiarly compliant behavior of LiNiO₂ due to the interaction of Jahn-Teller distortions with the dislocation strain field. Finally, we analyze the tendency of vacancies to segregate along dislocation lines. This study represents the first instance of explicit ab-initio atomistic dislocation models in layered oxides and paves the way for the understanding and optimization of the chemomechanical behavior of cathode active materials during battery operation.