Hydrothermal synthesis parameter engineering and mass loading of polyaniline electrodes for high-performance supercapacitors

The increasing demand for compact, portable, and cost-effective energy storage fuels advancements in supercapacitors, where achieving high capacitance at elevated mass loadings and excellent rate capability with materials like polyaniline (PANI) is key to enhancing energy density without compromising high power density. This study investigates the effect of synthesis temperature of PANI over a range of 60 °C to 140 °C and reaction time (3, 5 and 7 h), to enhance its electrochemical performance. Among the various conditions tested, PANI synthesized at 80 °C for 5 h (P-80 °C (5 h)) demonstrated optimal performance. The optimized sample was further evaluated at high mass loadings ranging from 1 to 10 mg cm –2 , exhibiting a specific capacitance of 356 F g –1 at 1 mV s –1 for a 1 mg cm –2 mass. Notably, at 7 mg cm –2 , the electrode achieved an impressive areal capacitance of 1172 mF cm –2 and a specific capacitance of 167.4 F g –1 . A symmetric supercapacitor device configured as PANI//PANI, with a total active mass of 7 mg, employing a hydrogel electrolyte (H 2 SO 4 ), delivered an areal capacitance of 812 mF cm –2 and a specific capacitance of 117 F g –1 at a scan rate of 1 mV s –1 . Furthermore, the device retained 76.2% of its initial capacitance after 5,000 charge-discharge cycles at a current density of 10 mA cm –2 . These findings highlight the promise of hydrothermally synthesized PANI and hydrogel electrolytes for advancing high-performance supercapacitors.