A new design of electrochromic energy storage device with high capacity, long cycle lifetime and multicolor display

Electrochromic energy storage (EES) devices with high capacity, long-term stability and multicolor display are highly desired for practical applications. Here, we propose a new three-electrode design of the EES device. Two kinds of electrochromic materials (WO3 and Ti-V2O5 respectively) deposited on ITO glass work as electrochromic active layers, and Al metal is used as anodic frame of the device to seal the mixed Li/Al-ion electrolyte. For electrochromic applications, the device shows rapid, self-powered color switch with multicolor display (light yellow, transparent, light red, dark green, dark blue and black). As an energy storage device, as-assembled device provides open-circuit voltages up to 3.5 V (Al anode/Ti-V2O5 cathode) with areal capacity up to 933 mAh/m2 (Al/Ti-V2O5 and Al/WO3), which are the best among all reported EES devices. Meanwhile, the utilization of the mixed Li/Al-ion electrolyte and the adding of PEDOT:PSS into the films greatly promotes the robustness and the cycle stability of the electrochromic layers. Such a new design of the EES device with multicolor display, large charge capacity and high cycle stability can be promising for future color switching/energy storage applications, which may also bring new insights in the design of multifunctional devices.