Synergistic WO3-PBI hybrid electrochromic materials with an enhanced diffusion coefficient and cycling reversibility inspired by the “Big Rocks” theory

Abstract

The key technology underlying intelligent energy conversion and display systems hinges on high-performance electrochromic materials. To drive their electrochemical redox reactions, facilitating ion/electron transport and intercalation/deintercalation via the rational design of a highly connected electrode structure is critical. However, persistent challenges include inadequate interconnection between active species – stemming from the inherent limitations of simple inorganic materials and severe performance degradation during long-term electrochemical cycling. To address the interconnection issue of active species, we propose a novel inorganic/organic hybrid film inspired by the “Big Rocks” theory: PBI derivatives are dip-coated onto a pure WO₃ film to form a secondary structure. The effects of optimal preparation parameters on the experimental outcomes were analyzed. The WO₃/PBI hybrid film exhibited a reversibility of approximately 98% after 1400 cycles, whereas the WO₃ film retained only 47% reversibility after 500 cycles. The coloration efficiency of the WO₃/PBI hybrid film (245 cm² per C) was more than twice that of the WO₃ film (114 cm² per C). The superior cycling durability and coloration efficiency of the hybrid film are attributed to three key factors: (1) surface modification by the organic component, (2) an enhanced ion diffusion coefficient, and (3) improved electrochemical activity enabled by the incorporation of PBI-CB derivatives. Additionally, the remarkable electrochromic performance of the WO₃/PBI material was demonstrated, showcasing its potential as an intelligent strategy for automatic optical switching using hybrid materials. These findings will pave the way for next-generation intelligent technologies geared toward building a sustainable and livable future.