An Anode‐Free Reflectance‐Modulated Smart Window via Reversible Zinc Electrodeposition for Enhanced Solar Heat Management

Abstract Buildings account for 40% of global energy consumption, with half expended on thermal management. While reversible zinc electrodeposition devices (Zn‐ECDs) offer promising broad‐spectrum modulation for smart windows, conventional designs require complex Zn‐anodes and exhibit heat‐absorbing black states. Here, an anode‐free, reflectance‐modulated Zn‐ECD (ZERD) employing an optimized iodide‐based electrolyte is presented. This design eliminates costly metal meshes while enabling rapid switching (7 s coloring/97 s bleaching) and broad optical modulation (ΔT = 84.9% at 650 nm). Notably, ZERD's high‐reflectance mirror state (R sol = 64.98%) and low solar heat gain coefficient (SHGC = 0.109) significantly enhances solar isolation ability, cutting interior temperature rise by 8.8 °C versus Zn‐ECD which exhibited black in its coloring state. The energy consumption simulations confirm > 40% cooling energy savings of ZERD versus normal glass, and consistent 7.5–21.2% improvements over black Zn‐ECDs in tropical cities. This work provides a novel reference for high‐performance, reflectance‐modulated electrochromic windows.