Stablizing metal grid electrode by deep eutectic electrolyte for long-term electrochromic smart windows

Metal grid electrodes, as transparent conductors, are attractive for high-performance electrochromic devices (ECDs) due to their high electrical conductivity, excellent mechanical flexibility, and optical transparency, ideal for flexible electronics and energy-related devices. However, metal grids are prone to structural degradation or even fracture when involved in electrochromic reactions, significantly compromising the cycling stability of the devices. This study proposes a deep eutectic electrolyte (DEE) design strategy to significantly improve the reversible stripping/plating of metal grid electrodes, thereby achieving long-term cycling stability in ECDs. The DEE system composed of zinc chloride (ZnCl₂) and N-methylacetamide (NMA) shows high decomposition voltage (~2.9 V) and low T_g (−63.3 °C), which is proved to facilitate highly reversible metal stripping/plating, based on the formation of a unique organic-inorganic hybrid SEI film on the zinc grid electrode surface. This study provides an innovative electrolyte strategy for stabilizing metal grid electrodes, paving their ways for practical application in smart windows.