Role of redox-active centres and charge density in covalent organic networks for energy storage applications as a high-performance asymmetric supercapacitor

Abstract

Global energy concerns are escalating daily as fossil fuel consumption rises. Therefore, the development of clean energy storage systems is crucial for mitigating environmental pollution and ensuring a secure energy future. Therefore, metal-free porous organic networks are emerging platforms, as they are utilized as electrodes for energy storage devices due to their excellent stability in harsh conditions, and the redox-active polymeric backbone promotes better charge storage capability. Although conjugated porous networks are being explored due to their excellent charge stabilization, the field of non-conjugated systems remains relatively challenging. In this work, we explore insights into non-conjugated-based systems and tuning the performance of the networks, with a focus on redox centers and charge density. Three porous covalent organic networks, CON-1, CON-2 and CON-3 were designed and synthesized. Among the three networks, the multiple redox-active centre-based polymer CON-1 has shown enhanced supercapacitive performance due to the greater number of interaction sites with electrolyte ions compared to the other networks. Triazine and anthraquinone-based CON-1 achieved a specific capacitance of 70 F/g at a current density of 0.5 A/g in a three-electrode setup. The asymmetric device of CON-1// AC achieved 72.9 mF/ cm2 at a current density of 0.1 mA/ cm2. GCD plots confirm its fast-charging ability, and its pseudocapacitive nature takes more discharging time compared with other reported state-of-the-art electrode materials. After 2000, switching CON-1 retains 91.9% of its initial specific capacitance, confirming the material's excellent stability in harsh conditions, which promotes its practical applicability. The practical applicability of the device was validated by its ability to power multiple light-emitting diodes (LEDs) for several minutes following a short charging duration, demonstrating efficient energy storage and sustained power delivery.