Preparation and Electrochemical Properties of Co-Doped Hypercrosslinked Polynaphthalene-Based Microporous Carbon

In response to the urgent demand for sustainable energy storage technologies and the reduction of environmental contamination from fossil fuels, supercapacitors are recognized as a viable technological advancement. They are distinguished by their superior power density and exceptional stability over numerous cycles. However, their energy density is still rather low compared to other available options, and this is a significant deterrent to their use. Some of the recent works have shown that integrating electric double-layer capacitance with pseudo-capacitance can greatly improve the energy density of such systems. To this end, the hypercrosslinked polynaphthalene-based polymer was used to synthesize the microporous carbon through the process of chemical activation, and the material was named MONC-800-2. Then, cobalt acetylacetonate was used to introduce Co into the carbon matrix using the hydrothermal method to synthesize Co-doped hypercrosslinked polynaphthalene-based microporous carbon, namely MONC-800-2@Co-1-190. This material was revealed to have high microporosity and proper pore size distribution. The integration of cobalt within the electrode material of supercapacitors successfully combines the features of electric double-layer capacitors and pseudo-capacitive mechanisms, yielding a specific capacitance of 363.8 F g⁻¹ at a charging current density of 1.0 A g⁻¹. Employed within a hybrid supercapacitor system, this setup achieved an energy density of 16.13 Wh kg⁻¹ and a power density of 750 W kg⁻¹. After enduring 5000 charge–discharge cycles under a steady current, the system preserved 82.85% of its initial capacitance while maintaining a coulombic efficiency of approximately 99.99%, thereby demonstrating its excellent cycling stability and high coulombic efficiency. The developed work is significant in advancing the metal-doped microporous carbon materials for the improvement of supercapacitors.