Engineering a low lattice mismatch interface layer for durable and bi-stable dynamic smart windows based on reversible metal electrodeposition

Abstract

Reversible metal electrodeposition-based electrochromic devices (RMEDs) featuring large optical contrast, broadband optical modulation, a simple device configuration and color neutrality have emerged as promising dynamic window platforms for advancing building energy efficiency. However, achieving long-term durability and bi-stability remains challenging due to the uncontrolled electrode/electrolyte interface structure. Herein, we screen and graft a low lattice mismatch (δ) NiO@C layer onto fluorine-doped tin oxide (FTO) glass, offering homogeneous interfacial electric field/ion concentration/current density distributions and higher interface Zn (002) formation energy (E_f = −0.449 eV atom⁻¹) to guide uniform Zn–Cu co-deposition. The resulting low δ NiO@C-FTO demonstrates lower metal plating/stripping activation energy (7.32 kJ mol⁻¹), large optical modulation (ΔT = 65.1%), fast switching (t_c = 10.2 s and t_b = 7.2 s), high coloration efficiency (16.77 cm² C⁻¹), color neutrality (Chroma C* = 3.585), and outstanding stability (>3100 cycles). The as-assembled NiO@C-RMED demonstrates exceptional bi-stability (T% < 10% after 22 days), excellent heat blocking capability, large solar heat gain coefficient modulation (0.38), and remarkable building energy-saving potential in either tropical (annual energy savings up to 185 MJ m⁻² vs. low-E glass) or other climatic zones. This work sheds light on electrode/electrolyte interface engineering towards developing durable and bi-stable electrochromic smart windows for advancing building energy efficiency.