Rylene Diimide-Based Alternate and Random Copolymers for Flexible Supercapacitor Electrode Materials with Exceptional Stability and High Power Density

Donor-acceptor pi-conjugated polymers are emerging as interesting electrode materials for supercapacitor device applications. They offer an exciting possibility of charge storage in both positive and negative electrodes because they are both p- and n-dopable. The ambipolar charging enables higher operating voltage, which can afford higher specific energy and power densities. The donor-acceptor design can be either donor-alternate acceptor or donor-random-acceptor. This architectural variation has the potential to modify the charge storage; yet surprisingly not much literature data is available exploiting this aspect. This paper explores the alternate and random geometries of donor-acceptor pi-conjugated polymers based on naphthalene diimide or perylene diimide (PDI) as the acceptor component and benzodithiophene (BDT) as the donor component and their application as composite electrode materials in a type III supercapacitor device. Results show that the donor-acceptor alternate design involving P(PDI-alt-BDT) is an excellent supercapacitor electrode material with specific capacitance of 113 F g(-1) with excellent stability up to 4000 cycles and almost 100% retention of the initial capacitance in a single-electrode setup in a PC-LiClO4 organic electrolyte. A flexible supercapacitor device was also fabricated which shows areal capacitance of 35 mF cm(-2) at a current density of 0.5 mA cm(-2), which is promising for commercial applications.