A Scalable, Robust Polyvinyl‐Butyral‐Based Solid Polymer Electrolyte with Outstanding Ionic Conductivity for Laminated Large‐Area WO₃–NiO Electrochromic Devices

Abstract Polyvinyl butyral (PVB) is a well‐established polymer interlayer material that has been used in laminated safety glass panels for over 80 years. However, its intrinsically poor ionic conductivity (σ) severely restricts its widespread application as a solid polymer electrolyte (SPE) for laminated WO₃–NiO electrochromic devices (ECDs). Here, a new strategy for significantly improving the σ of PVB via a cross‐linking reaction with 3‐glycidoxypropyltrimethoxysilane (KH560) is presented. The cross‐linked PVB‐SPE with 10 wt.% KH560 exhibits the highest room‐temperature σ value among the investigated samples (1.51 × 10⁻⁴ S cm⁻¹), which is also higher than that of previously reported PVB‐based SPEs (10⁻⁵–10⁻⁷ S cm⁻¹). Additionally, the prepared SPE exhibits comprehensive optical, mechanical, and thermal performances, including a high visible transmittance (>91%), relatively high adhesive strength (2.13 MPa), and superior thermal stability (up to 150 °C). Laminated WO₃–NiO ECDs with dimensions of 5 × 5 cm² and 20 × 20 cm², fabricated by leveraging the aforementioned properties of the electrolyte, operate stably at temperatures ranging from −20 to 80 °C, underscoring the potential of the PVB‐SPE for realizing commercially viable large‐area ECDs.