Synthesis and Electrochemical Characterization of Azulene Polymers for Use in Electric Double-Layer Supercapacitors

Although lithium-ion battery technology has been improving in recent years, there is still concern for eco-friendly production, overcharging, and end-of-life disposal. Electrochemical double-layer (EDL) supercapacitors have a much smaller energy density than traditional batteries, but when used complementary to a battery can offer up to 100 times the power density of the battery alone. EDL supercapacitors offer nanoscopic charge separation, are less expensive to manufacture, have greater cyclability, and are more power dense and eco-friendly than traditional batteries. In this study, the electrical properties of polymeric and co-polymeric azulene and trimethylazulene films prepared by electrochemical oxidation were studied for implications in EDL supercapacitors. Electrochemical quartz crystal microbalance (EQCM) was utilized to calculate the mass of polymer electrochemically deposited onto an electrode, allowing for the determination of a thin film's specific capacitance. Contrary to literature precedent, trimethylazulene was unable to be electropolymerized into a conducting film, while azulene was, with fast charge/discharge rates and good cyclability.