Enhanced electrochemical and thermal performance of nitrogen-doped expanded graphite/hexagonal boron nitride porous electrodes for supercapacitor

Abstract

This study explores the electrochemical and thermal properties of nitrogen-doped expanded graphite (EG) and hexagonal boron nitride (h-BN) porous paper electrodes, with a focus on their performance in symmetric supercapacitors. Composite electrodes containing 1 wt% and 8 wt% h-BN were fabricated and systematically characterized through electrochemical, thermal, and structural analyses. As the operating temperature increased from 10 °C to 60 °C, the areal capacitance of the 8 wt% h-BN/EG electrode decreased slightly from 187 mF/cm² to 184 mF/cm², whereas the 1 wt% h-BN/EG electrode exhibited a more pronounced reduction from 348 mF/cm² to 277 mF/cm² at a scan rate of 50 mV/s, demonstrating the superior thermal stability of the 8 wt% h-BN/EG electrode. The 8 wt% h-BN/EG electrode further exhibited enhanced thermal stability, maintaining a low charge-transfer resistance of 0.78 Ω at 60 °C and retaining 98.4 % of its initial capacitance over the temperature range of 10 °C–60 °C. Cyclic voltammetry and galvanostatic charge-discharge analyses revealed pseudocapacitive behavior and excellent cycling stability, with the 1 wt% h-BN/EG electrode retaining 92 % of its capacitance after 4000 cycles at 10 °C. Thermal imaging confirmed the improved thermal conductivity of the 8 wt% h-BN/EG electrode, attributed to its higher h-BN content, which minimized dimensional changes under heat exposure.