In Ni-rich cathode materials, dislocation can be generated at the surface of primary grains due to the accumulation of stress fields. The migration of dislocation into grains, accelerating the annihilation of reverse dislocation as well as the oxygen loss, is considered as the principle origin of crack nucleation, phase transformation and a consequent fast capacity decay. Thus, reducing the dislocation would be effective in improving the cathode stability. Here, we report the inspiring role of oxygen vacancies in blocking and anchoring the dislocation. Specifically, a large number of oxygen vacancies can assemble to form dense dislocation layers at the surface of grain. Thanks to the dislocation interaction mechanism, pre-formed dense dislocation at the surface can effectively rivet the newly developed dislocation during cycling. The <i>ex-situ</i> TEM analysis indicates the intragranular cracks and phase transformation were hindered by the riveted effect, which in turn improved the structural and cycle stability of the Ni-rich cathode. Overall, this work provides novel crystallographic design and understanding of the enhanced mechanical strength of Ni-rich cathode materials.

Riveting dislocation motion: The inspiring role of oxygen vacancies in structural stability of Ni-rich cathode materials

ACS Fall 2021

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