Misfit strain-induced mechanical cracking aggravating surface degradation of LiCoO2.

Cycling-induced cathode interfacial degradations are usually attributed to chemical process, while the physical effect is overlooked to a large extent. Herein, we investigate the failure mechanism of LiCoO₂ cathode and reveal that misfit strain plays a dominant role in the surface layer exfoliation process. We illustrate that highly strained LiCoO₂ surface can initiate massive surface cracks, leading to the LiCoO₂ surface layer broken and exfoliation. Mechanical cracking coupled with chemical etching aggravates the surface layer degradation, leading to a weathering-like degradation on LiCoO₂ surface. Our work reveals that interfacial degradation of electrode materials is a complex physicochemical process. Impact Statement We declare that we have no financial and personal relationships with other people or organizations. [ABSTRACT FROM AUTHOR]