Electrochromism via reversible electrodeposition of solid iodine

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Electrochromic materials, known since the 1960s, typically involve transition metal oxides, polymers, or small molecules.
• The electrochromic phenomenon is rarely observed in non-metallic elemental substances, presenting a research gap.
• Traditional electrochromic systems often face challenges with material stability and performance limitations.

Purpose of the Study:

• To develop novel non-metallic electrochromic dynamic windows.
• To explore the use of iodine electrodeposition within a water-in-salt electrolyte for electrochromic applications.
• To overcome limitations of existing electrochromic materials and systems.

Main Methods:

• Development of an electrochromic dynamic window based on iodine electrodeposition.
• Utilization of a water-in-salt electrolyte containing iodine ions to create a unique reaction pathway.
• Fabrication of a 400 cm² complementary dynamic window to demonstrate practical performance.

Main Results:

• Achieved a high optical contrast of 76.0% with near color neutrality.
• Demonstrated excellent cycling stability and a reversible solid-liquid transition between solid iodine and solvated iodide ions.
• The developed window exhibited fast response times, uniform modulation, and polarity-switchable functionality.

Conclusions:

• Non-metallic iodine electrodeposition in a water-in-salt electrolyte offers a promising new route for electrochromic dynamic windows.
• The unique electrolyte suppresses iodine dissolution and shuttle effects, enabling a novel solid-liquid transition mechanism.
• The fabricated dynamic windows show excellent performance, paving the way for advanced smart window technologies.