An aqueous aluminum-ion electrochromic energy storage device with visual energy level

Abstract

Electrochromic energy storage devices (EESDs) integrate energy storage and electrochromism into one smart device that can realize the visualization of the energy level by the naked eyes, which has attracted extensive attention in recent years. It is critical to explore suitable electrode materials for achieving both high electrochromic and electrochemical performance. Herein, we propose an aqueous aluminum-ion electrochromic energy storage device (AIEESD) by assembling the polyaniline (PANI) electrochromic cathode, Al metal frame anode and AlCl 3 electrolyte, which yields an open-circuit voltage of ∼1.22 V and a fast self-bleaching behavior without any energy input. Additionally, the developed device exhibits outstanding electrochromic energy storage performances with discharging capacity of 68.1 mAh m −2 , excellent rate capability, large optical modulation (ΔT = 55% at 630 nm) and high coloration efficiency (93.62 cm 2 C −1 at 630 nm). Moreover, the prototype device can reversibly switch between the multicolor (transparent, light yellow, green and dark blue) when the voltage changes from 0.4 to 2.5 V, which means the energy status can be monitored by the obvious color transition. These results show that the AIEESD in this work has great application prospects for smart windows and energy storage displays. An aqueous aluminum-ion electrochromic energy storage device based on PANI cathode has been developed, and it demonstrates fast spontaneous bleaching process without any external energy input. The as-assembled device exhibits both high electrochromic and energy storage performances due to the multivalent-ions interaction with PANI materials. Importantly, the device demonstrates its energy level by displaying multi-colors from dark blue, green, light yellow to transparent and shows potential applications in graphic display. • An aqueous aluminum-ion electrochromic energy storage device is developed. • The prototype device can achieve the visualization of the energy status. • The device demonstrates energy retrieve function and multicolor graphical display.