Supercapacitor Electrode Derived from Polyacrylonitrile (PAN)/Poly(Styrene-co-acrylonitril

Supercapacitors are energy storage devices that can store more energy than conventional capacitors and deliver the energy faster than batteries. Although, batteries may have a higher energy density, supercapacitors can have a cycle life up to 1000 cycles between recharge. Supercapacitors store energy electrostatically at the electrode and electrolyte interface. The amount of energy stored at the electrode and electrolyte interface can vary greatly due to the surface area of the electrode. Since, the energy density of supercapacitors is much lower than the energy densities of batteries, the purpose of this project was to increase the surface area of the electrodes; thus, achieving a higher energy density. Porous electrodes are necessary to create a high energy density supercapacitor due to the relationship between surface area and energy density. Polymer incompatibility in blends results in interesting morphologies, which are difficult to predict and control as the degree of incompatibility increases. Poly(Styrene-co-acrylonitrile) (SAN), a copolymer of styrene and acrylonitrile, makes the PAN and SAN blend more compatible than PAN and polystyrene blend. Due to the positive correlation between electrode surface area and energy density, after polymer decomposition, the PAN/SAN supercapacitor should have a higher surface area and energy density than a PAN supercapacitor. In this study, we prepared supercapacitor electrode fibers through electrospinning blend solutions of PAN (75%) with SAN (25%) followed by thermal treatments including stabilization, carbonization, and CO₂ activation. First, the fibers were electrospun and stabilized at 280 ℃ for 60 minutes. SAN decomposed at this temperature and introduced pores in the fibers. Then the fibers were carbonized and activated at 1000 ℃ using CO₂ for 60 minutes. The carbonized and electrospun fibers were characterized through Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), IR Spectroscopy, and thermogravimetric analysis. Electrochemical performance was evaluated in coin cell devices utilizing the free standing flexible carbon mats that was obtained. In conclusion, the PAN/SAN supercapacitor achieved a high energy capacity of 62 Wh/kg, which was 6 times that of a conventional capacitor and equivalent to that of a lead acid battery. Furthermore, the device showed a high cycle life and a high energy retention as the power density increased from 1000 W/kg to 10,000 W/kg. This research was supported by Dr. John P. Ferraris and University of Texas at Dallas.