Multifunctional Applications of D−π–A-Type Poly Schiff Bases for Electrochromic, Electrofluorochromic Materials, and Organic Cathodes for Aqueous Zinc Ion Batteries

Based on triphenylamine (TPA) and aromatic diamines, two multifunctional donor–π–acceptor (D−π–A) conjugated poly-Schiff bases (PSBs) were synthesized and subsequently tested and analyzed. The aforementioned conjugated PSBs exhibit electrochromic (EC) and electrofluorochromic (EFC) features and can be utilized as cathode electrode materials for aqueous Zn-ion batteries (AZIBs). Both polymer films, PTTB-1 and PTTB-2, show good EC and EFC properties, excellent dissolution processability, thermal stability, and reversible yellow-to-violet color changes in the UV–vis region. Between them, better optical contrast (46%), a fast response time (2.8 s/8.2 s), a high coloring efficiency (CE = 310 cm 2 C –1 ), and good cycling stability (10% attenuation over 2000 s of cycling) are all displayed by the PTTB-2 polymer. PTTB-1 and PTTB-2 present excellent EFC properties and solvatochromic effects. Full batteries constructed using a zinc anode, PSB cathodes, and 2 mol L –1 Zn(CF 3 SO 3 ) 2 aqueous solution show better rate performance, quicker reaction kinetics, and high cycling stability. The specific capacities of PAZIB-1 and PAZIB-2 reach 143 and 150 mA h g –1, respectively, at a current density of 0.1 A g –1 . Furthermore, the specific capacities can still reach 93 and 102 mA h g –1 at a high current density of 6 A g –1 . Surprisingly, the full batteries exhibit outstanding cycling stability for long-term cycling (6 A g –1, >5000 cycles). These innovative PSB materials, which integrate several functionalities, present more opportunities for the development of EC displays, AZIBs, sensing materials, and energy-efficient smart windows.