Quasi-solid-state electrolytes enabling long-life flexible electrochromic energy storage smart windows

Intelligent electrochromic systems that integrate energy storage with optical feedback are increasingly sought after to meet the demands of global energy transition and the burgeoning field of flexible electronics. Yet, the performance and reliability of flexible zinc-based electrochromic energy storage devices (EESDs) are often compromised by the limitations of conventional electrolytes, including poor interfacial stability, liquid leakage, and inadequate mechanical robustness. Herein, we report a high-performance flexible EESD based on a Prussian blue–zinc (PB–Zn) chemistry, enabled by a scalable blade-coated PB cathode and a quasi-solid-state electrolyte (QSSE) incorporating a semi-interpenetrating polymer network (semi-IPN) of poly(vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP) and ethoxylated trimethylolpropane triacrylate (EOTMPTA). The device delivers a high optical modulation of 74.49%, a coloration efficiency of 189.77 cm 2 C −1 , and outstanding cycling stability with 93.72% retention after 10,000 cycles, attributed to a stabilized electrode–electrolyte interface enabling highly reversible zinc electrochemistry. Moreover, the system demonstrates efficient self-powered operation when integrated with a solar cell (SC), highlighting its potential for energy-autonomous smart windows. Overall, this work establishes a material–interface co-design strategy that provides a promising pathway toward durable, high-performance, and self-sustaining electrochromic smart windows.