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

Abstract

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 an EES device. Two kinds of electrochromic materials (WO₃ and Ti-V₂O₅ respectively) deposited on ITO glass work as electrochromic active layers. Al metal is used as the anodic frame of the device and helps to seal the mixed Li/Al-ion electrolyte. For electrochromic applications, the device shows rapid, self-powered color switching with multicolor display (light yellow, transparent, light red, dark green, dark blue and black). As an energy storage device, the as-assembled device provides open-circuit voltages up to 3.5 V (Al anode/Ti-V₂O₅ cathode) with an areal capacity of up to 933 mA h m⁻² (Al/Ti-V₂O₅ and Al/WO₃), which are the best among those of all reported EES devices. Meanwhile, the utilization of the mixed Li/Al-ion electrolyte and the addition of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) into the films greatly promote 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 provide new insights into the design of multifunctional devices.