Synergistic contribution of activated carbon and PEDOT:PSS in hybrid electrodes for high-performance planar micro-supercapacitors

The high-performance miniaturized micro-supercapacitors exhibit great potential due to their inherent properties of high-power density, fast charge–discharge rates, long cycle life, and wide working temperature range. However, there is a need to further enhance the energy density of micro-supercapacitors. In this study, we investigate a hybrid electrode material combination comprising activated carbon (AC) and polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to fabricate symmetric micro-supercapacitors (SMSCs) and employ the advanced Microplotter technique for the effective loading of active materials onto microelectrodes. The combination of AC and PEDOT:PSS is fine-tuned to attain optimal charge storage. This involves leveraging the synergistic impact of electrical double-layer capacitance from AC and pseudocapacitance from PEDOT:PSS, resulting in enhanced charge storage performance. Additionally, PEDOT:PSS acts as a mixed ion–electron conducting adhesive, effectively binding AC particles together and facilitating the rapid transport of both ions and electrons. As a result, the AC-PEDOT:PSS SMSCs demonstrate an impressive charge storage performance compared to AC SMSCs. At 1 mA/cm2, the measured areal capacitance (device areal capacitances) is 29.5 mF/cm2 (11.8 mF/cm2) for AC-PEDOT:PSS and 15.7 mF/cm2 (6.3 mF/cm2) for AC SMSCs. Furthermore, the areal energy densities and power densities, considering active materials, are found to be 2.79 µWh/cm2 at 0.8 mW/cm2, and considering the device area of the SMSC, they are 1.12 µWh/cm2 at 0.32 mW/cm2. Notably, the AC-PEDOT:PSS SMSCs exhibit a stable long-term capacitance with 85% capacitance retention even after 5000 cycles. This work highlights the significant potential of hybrid materials in improving energy storage performance and showcases the innovative application of the Microplotter technique.