Revealing the Electrochemical Lithiation Routes of CuO Nanowires by in Situ TEM

The dynamic lithiation processes of CuO nanowires were studied by the construction of an electrochemical reaction cell inside a transmission electron microscope (TEM), where the morphology evolution and the phase transformation during lithiation have been recorded in real time by in situ TEM imaging, selected area electron diffraction (SAED) patterning and electron energy loss spectroscopy (EELS). The lithiated length (L) and the corresponding lithiation time (t) of the nanowires were measured to investigate the lithiation kinetics. Based on the relationship between L and t it is found that two lithiation reaction routes occur in the CuO nanowires. The lithiation of CuO nanowires with smaller resistance under −3.5 V potential is speculated to be a two‐step lithiation route controlled by a short‐range interface reaction, whereas upon the same applied potential the lithiation of nanowires with larger resistance presents a diffusion process with a general one‐step reaction route. The research enriches our understanding of the lithiation kinetics of CuO anodes and also the solid‐state electrochemical reaction mechanism of CuO. The long and the short of it: The lithiation processes of CuO nanowires is observed in real time by in situ TEM. Short and long nanowires lithiated under the same potential exhibit different kinetic behavior. The short nanowires with smaller resistacne has a L∝t relationship whereas thelong nanowires with larger resistance display a L∝t1/2 relationship.