A high-capacity and self-healable electrochromic system based on I0/CuI conversion reaction.

• Reversible color change between transparent and dark brown is achieved based on I0/CuI conversion. • This redox couple delivers a high charge storage capacity of 246.7 mA h g−1. • Bifunctional P10 binder is introduced to suppress polyiodide shuttle issue, besides improving structural stability. • A self-healing mechanism is further proposed by making good use of the CuI/Cu couple to rejuvenate performance. Constructing electrochromic devices (ECDs) requires high-performance electrochromic electrodes with not only high color contrasts, but also large charge storage capacities. In this paper, a I0/CuI conversion-type electrochromic system is developed, achieving reversible and profound color switching between colorless transparent and dark brown, while delivering a large charge storage capacity of 246.7 mA h g−1. To improve switching durability, a multifunctional P10 (Polyquaternium-10) binder is introduced into the electrode, which can effectively confine the polyiodide intermediates and suppress the shuttle effect. At the same time, the CuI/Cu redox couple is further activated by controlling the applied voltage. The generated Cu from this couple can spontaneously react with residual I0 species and facilitate the conversion from I0 to CuI, and therefore in-situ rejuvenate the degraded electrochromic performance. Thanks to these rational designs, this electrochromic electrode achieves rapid response speeds (t coloring : 14 s, t bleaching : 5 s), high optical modulation amplitude (73.4 % at 500 nm), decant coloration efficiency (57.0 cm2 C−1) and impressive cycle stability (without performance degradation after 150 cycles). This work provides a novel electrochromic system for the construction of high-performance electrochromic devices. [ABSTRACT FROM AUTHOR]