Study on electrochemical ion behavior and electrochromic properties of NiO thin films prepared by magnetron sputtering with different oxygen levels

Electrochromic NiO thin films were prepared by the DC magnetron sputtering method under different oxygen partial pressure conditions. The phase, microstructure, ions moving behavior, and electrochromic properties of NiO films were investigated by X-ray diffraction, field emission scanning electron microscopy, Raman spectrometer, electrochemical workstation, and ultraviolet-visible-infrared spectrophotometer, respectively. The sample prepared under middle oxygen partial pressure shows better electrochromic properties after the coloring and bleaching cycles. The coloring or bleaching time is 1∼4 s, the optical modulation amplitude is 40.6% and the coloration efficiency is 37.63 cm2·C−1. The oxygen partial pressure may mainly affect the crystallinity of the samples, resulting in different charge-transfer resistance which is related to the reactions of coloring or irreversible non-coloring. Further, the Li+ can be stored in the volume space and surface space of NiO thin films, and the grain boundary and lattice gap are two existent paths for Li+transmission and storage.