Confined Solid-State Polyiodide Deposition Enables Durable Electrochromic Smart Windows

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Electrochromic smart windows offer dynamic building energy management.
• Conventional systems face challenges like structural degradation and dendrite growth.
• Existing technologies limit durability and performance in smart windows.

Purpose of the Study:

• To develop a novel Zn-coupled electrochromic device with improved durability and performance.
• To address limitations of ion-intercalation and metal electrodeposition systems.
• To establish a new design paradigm for scalable and efficient smart windows.

Main Methods:

• Utilized a coordination-governed reversible polyiodide deposition mechanism.
• Introduced tetramethylammonium cation ([N1111]+) for stabilizing polyiodide complexes.
• Engineered interfacial adsorption on the Zn electrode to promote uniform deposition.

Main Results:

• Achieved a stable solid-state [N1111]+I5- complex, suppressing polyiodide shuttle.
• Demonstrated highly reversible I-/I5- conversion and uniform Zn plating/stripping.
• Reported high optical contrast (75.5%), fast switching (3.9/6.5 s), and excellent cycling stability (84.9% after 20,000 cycles).

Conclusions:

• The developed device offers significant solar blocking (93.6%) and cooling effects (4°C-10°C).
• Achieved substantial annual energy savings of 16.4%.
• Established a promising strategy for durable and scalable electrochromic smart windows based on confined polyiodide chemistry.