From the mechanical perspectives, the influence of point defects is generally considered at high temperature, especially when the creep deformation dominates. Here, we show the stress-induced reversible oxygen vacancy migration in CuO nanowires at room temperature, causing the unanticipated anelastic deformation. The anelastic strain is associated with the nucleation of oxygen-deficient CuOx phase, which gradually transforms back to CuO after stress releasing, leading to the gradual recovery of the nanowire shape. Detailed analysis reveals an oxygen deficient metastable CuOx phase that has been overlooked in the literatures. Both theoretical and experimental investigations faithfully predict the oxygen vacancy diffusion pathways in CuO. Our finding facilitates a better understanding of the complicated mechanical behaviors in materials, which could also be relevant across multiple scientific disciplines, such as high-temperature superconductivity and solid-state chemistry in Cu-O compounds, etc.

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Surface coating strategy has been proved essential for mitigating the large volume change in the electrodes for lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs), thus improving the cyclability and working efficiency of batteries. However, the mechanical instability of electrode generated by incorporating heterostructure interface between the coating and core materials remains largely unexplored. Here, the effects of carbon and gold coatings on the nanomechanical properties of CuO nanowires (NWs) are investigated based on the in situ experiments during the electrochemical reactions. It is found that the NW deformability is mediated by the coating materials as well as the reaction speed. Besides, the inhomogeneity between coating and core materials can promote the crack propagation in the lithiated/sodiated CuO/C NWs and sodiated CuO/Au NWs. Further study indicates that the namomechanical behaviors also depend on the different reaction stages, e.g., lithiation/sodiation or delithiation/desodiation. This work serves as a guidance for building better ion batteries not only with improved electrochemical properties but enhanced mechanical stabilities.

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As an emerging candidate of anisotropic two-dimensional materials, the group IV-V family (e.g. GeP, GeP2) exhibits appealing applications in photoelectronics. However, their intrinsic point defect properties, which largely determine the...