Development and characterization of expandable graphite/hexagonal boron nitride based foam electrodes for high performance supercapacitor applications

This dissertation study aims to produce supercapacitor electrodes with increased electrochemical performance and more stable behavior in a wide temperature range. For this purpose, free-standing expandable graphite/h-BN composite foams were synthesized. The study investigates the effects of h-BN reinforcement on the physical and chemical properties of the electrodes. The supercapacitive behaviors of the electrodes were evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques at temperatures between 10-60°C. According to the findings, it was observed that the graphitic matrix was doped with pyrrolic and pyridinic nitrogen as a result of the decomposition of polyvinylpyrrolidone (PVP) used as a foaming agent. Although h-BN reinforcement improved the specific surface area, thermal conductivity, and temperature sensitivity of the electrodes, it negatively affected the specific capacitance of the electrodes. In the cyclic stability tests performed at low temperatures, it was found that h-BN reinforcement negatively affected the cyclic capacity; However, it was observed that h-BN had positive effects at high temperatures. Finally, a symmetric supercapacitor device was constructed, and how these electrodes performed in real applications was investigated.