Suppressing volume change and in situ electrochemical atom force microscopy observation during the lithiation/delithiation process for CuO nanorod array electrodes

Abstract

A big challenge in the high-performance transition metal oxide anode for lithium-ion batteries (LIBs) is relieving the volume changes during the lithiation/delithiation. In this work, CuO nanorod array was produced via glancing angle deposition and directly used as anode materials for thin film electrodes of LIBs. The obtained CuO nanorod array anodes show good LIB performance with a capacity of 220 μAh/cm2/μm tested at 100 μA/cm2 after 80 cycles and excellent rate performance. The obtained properties for CuO nanorod array anodes were much better than thin film anodes without nanorod array structure. In addition, the in situ electrochemical atom force microscopy (EC-AFM) characterization has been used to reveal the enhanced mechanism of CuO nanorod array anodes. On the one hand, CuO nanorods within the electrodes may serve as the hosts for Li+, and ease intercalation by shortening Li+ ion diffusion pathways, resulting in the remarkable cycling stability and rate performance. On the other hand, the “breathing” of CuO nanorod array electrode clearly observed by in situ EC-AFM with the appearance and disappearance of cracks, demonstrated that the nanorod array may act as a buffering to alleviate the giant volume variations during the cycling. As a result, the remarkable stability of the CuO nanorod array electrode allowed its use in a full lithium-ion cell with a pervasive LiCoO2 thin film cathode. Additionally, we also observed the SEI formed on the surface of electrode during cycling, which may benefit the further studies on transition metal oxide as anodes for LIBs.