A Strong and Highly Transparent Ionogel Electrolyte Enabled by In Situ Polymerization‐Induced Microphase Separation for High‐Performance Electrochromic Devices

Abstract Electrochromic devices built with ionogel electrolytes are seen as a pivotal step toward the future of quasi‐solid electrochromic devices, due to their striking properties like exceptional safety and high ionic conductivity. Yet, the poor mechanical strength of electrolyte of these devices remains a constraint that hampers their advancement. As a resolution, this research explores the use of a robust, transparent ionogel electrolyte, which is designed using an in situ microphase separation strategy. The ionogels are highly transparent and robust and exhibit excellent physicochemical stability, including a wide electrochemical window and high temperature tolerance. Benefitting from these properties, a high‐performance electrochromic device is fabricated through in situ polymerization with the ionogels, PPRODOT as the electrochromic layer, and PEDOT: PSS as the ion storage layer, achieving high transmittance contrast (43.1%), fast response (1/1.7 s), high coloring efficiency (1296.4 cm 2 C −1 ), and excellent cycling endurance (>99.9% retention after 2000 cycles). In addition, using ITO‐poly(ethylene terephthalate) as flexible substrates, a deformable electrochromic device displaying high stability is realized, highlighting the potential use in functional wearables.