Self-Driven Electrochromic Window System Cu/WO_x-Al³⁺/GR with Dynamic Optical Modulation and Static Graph Display Functions

Electrochromic devices with unique advantages of electrical/optical bistability are highly desired for energy-saving and information storage applications. Here, we put forward a self-driven Al-ion electrochromic system, which utilizes WO_x films, Cu foil, and graphite rod as electrochromic optical modulation and graph display electrodes, coloration potential supplying electrodes, and bleaching potential supplying electrodes, respectively. The inactive Cu electrode can not only realize the effective Al³⁺ cation intercalation into electrochromic WO_x electrodes but also eliminate the problem of metal anode consumption. The electrochromic WO_x electrodes cycled in Al³⁺ aqueous media exhibit a wide potential window (∼1.5 V), high coloration efficiency (36.0 cm²/C), and super-long-term cycle stability (>2000 cycles). The dynamic optical modulation and static graph display function can be achieved independently only by switching the electrode connection mode, thus bringing more features to this electrochromic system. For a large-area electrochromic system (10 × 10 cm²), the absolute transmittance value in its color-neutral state can reach about 41% (27%) at 633 nm (780 nm) by connecting the Cu and WO_x electrodes for 140 s. The original transparent state can be readily recovered by replacing the Cu foil with the graphite rod. This work throws light on next-generation electrochromic applications for optical/thermal modulation, privacy protection, and information display.