Coating‐Mediated Nanomechanical Behaviors of CuO Electrodes in Li‐ and Na‐Ion Batteries

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. Surface coating effects on the mechanical behaviors of C‐coated and Au‐coated CuO nanowires during electrochemical reactions are discussed. It is found that the heterostructure interface between the nanowire and coating layer plays a dominant role in determining the mechanical behaviors of electrodes during the electrochemical reactions.