Improved lithium electrochromic (EC) performance of flexible organo-tungsten-iron-tantalum oxynitride (WFexTayOz1Cz2Nz3) films by rapidly deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide) substrates at a short exposure duration of 54 s, with O2 gases added to precursor vapors, and injected into air plasma jet, was undertaken. O2 gases addition for synthesis of WFexTayOz1Cz2Nz3 films by cold atmospheric pressure plasmas polymerization was proven to significantly enhance optical modulation at a wavelength of 850 nm from 59.7% without addition of O2 gases to 70.0% with addition of O2 gases at a flow rate of 0.5 sccm. WFexTayOz1Cz2Nz3 films synthesized with O2 gas addition at a flow rate of 0.5 sccm exhibit fast coloration and bleaching responses as the short coloration time up to 5.1 s and the short bleaching time up to 3.7 s were obtained. Surface morphology and surface compositions of WFexTayOz1Cz2Nz3 films were analyzed by FESEM and XPS to investigate how the O2 gas addition enhanced the lithium EC properties.