High-Efficiency and High-Capacity Aqueous Electrochromic Energy Storage Devices Enabled by Decoupled Titanium Oxide/Viologen Derivative Hybrid Materials

Abstract

The integration of electrochromism and energy storage within a single platform marks a pioneering approach to multifunctional electronics. However, achieving electrochromic energy storage devices (EESDs) that exhibit both high coloration efficiency and substantial energy capacity remains a formidable challenge, primarily due to the inherent trade-off between these 2 functionalities. Herein, we propose a distinctive strategy for the fabrication of EESDs using a chemically bonded titanium oxide (TiO 2 )/viologen derivative ( TGP ) hybrid material, leveraging their decoupled electrochromic and energy storage mechanisms. The resulting EESDs demonstrate a remarkable coloration efficiency of 512.93 cm 2 /C and an impressive areal capacity of 62.2 mAh/m 2 . By employing molecular engineering, we effectively reduce the bandgap and mitigated radical dimerization of the viologen derivative, resulting in a highly saturated magenta-colored state with exceptional stability. The device retained its performance after 3,000 electrochemical cycles in environmentally benign aqueous electrolytes. Furthermore, integration with a counter Zn anode effectively enhances energy utilization efficiency through an energy retrieval process. This approach paves the way for the development of EESDs using hybrid materials, holding great potential to propel advancements in the field of visual energy storage.