Synergistic WO₃-PBI Hybrid Electrochromic Materials with Enhanced Diffusion Coefficient and Cycling Reversibility Inspired by "Big Rocks" Theory

Abstract

The key technology underlying intelligent energy conversion and display systems hinges on high-performance electrochromic materials. To derive their electrochemical redox reactions, facilitating ion/electron transport and intercalation/deintercalation via the rational design of a high connected electrode structure is critical. However, persistent challenges include in adequate interconnection between active species - stemming from the inherent limitations of simple inorganic materials and severe performance degradation during long-term electrochemical cycles. 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 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/C) was more than twice that of the WO3 film (114 cm2/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.