Preparation of electrospun polyacrylonıtrile (PAN) nanofıber membrane gel electrolyte and its application in TiO2-based electrochromic devices

Electrochromic devices based on nanofiber membrane gel electrolytes offer several advantages over polymer gel electrolytes. Many advantages, such as high chemical stability, easy handling, less leakage, a wide working temperature range, and a long cycle life, show high compatibility of nanofiber membrane electrolytes in different electrochemical power devices. In this work, we have succeeded in replacing the liquid electrolyte with a nanofiber membrane-based gel electrolyte prepared by the electrospinning method and applied in electrochromic devices (ECD). Polyacrilonitrile (PAN)-based nanofibers were deposited on a spin-coated SnO2 layer, prepared on a fluorine-doped tin oxide (FTO) glass substrate. The thickness of the fiber mat was varied by changing the time of the electrospinning. Gel-type membrane electrolyte was prepared by soaking the nanofiber membrane electrode in the 1 M LiClO4 in propylene corbonate (PC) solution. TiO2 electrochromic electrode was prepared by the "doctor blade" method. ECDs were fabricated with the configuration of FTO glass/TiO2/PAN-based nanofiber membrane gel polymer electrolyte/SnO2/FTO glass by sandwiching the two electrodes. Electrochromic performance of ECDs fabricated with nanofiber membrane gel electrolyte was compared with ECDs fabricated with liquid electrolyte (1 M LiClO4 in PC) and PAN-based conventional gel electrolyte (PC (0.4 g) + ethylene carbonate (EC) (0.4 g) + LiClO4 (0.03 g) + PAN). ECDs with nanofiber membrane gel electrolytes demonstrate a transmittance variation of 33.40% in the visible region which is 93% of the corresponding value obtained with liquid electrolyte-based ECD, whereas identical ECDs made with conventional gel electrolytes demonstrate a lower transmittance variation of 4.22%.