Novel terpyridine-Fe(II) coordination polymers with zigzag configuration for efficient electrochromic energy storage devices

In this work, three new terpyridine-Fe(II) coordination polymers (Fe-VTP-1, Fe-VTP-2 and Fe-VTP-3) with zigzag configuration were developed for electrochromism and energy storage. All these coordination polymers exhibited efficient electrochromic switching between purple and pale yellow, with an optical contrast of approximately 60 % at a specific wavelength of 578 nm, short response time of less than 2 s, high coloration efficiency exceeding 450 cm2 C−1, and good cycle stability. In addition, these polymers exhibited a specific capacitance of 2.8 mF cm−2 for Fe-VTP-1, 3.59 mF cm−2 for Fe-VTP-2, 2.38 mF cm−2 for Fe-VTP-3 at a current density of 0.1 mA/cm2, respectively. The area-specific capacitance of the Fe-VTP-1 and Fe-VTP-2 devices remained above 80 % of the initial value after 400 charge-discharge cycles under the voltage range among −2.0–3.0 V. Moreover, electrochromic energy storage devices base these three coordination polymers were fabricated and showed obvious color change during the charge/discharge process. Which possessed potential application in energy saving smart windows.