Heteroatom-Enriched Carbon Particles Derived from Multifunctional Polybenzoxazine Particles for High-Performance Supercapacitors

The rational molecular engineering of a heteroatom-enriched polymer precursor to achieve inherently doped carbon material is of crucial importance for advanced applications. In the present work, the molecular-design flexibility of polybenzoxazine is utilized to fabricate a N, O-codoped carbon framework using a facile template-free extended sol–gel method using phloroglucinol, polyethylenimine, and formaldehyde as multifunctional precursors. The uniform spherical morphology of the polymeric particles was attained by the careful tuning of the reactant stoichiometric ratio, precursor concentration, and solvent ratio in the reaction medium to control the kinetics of particle formation. The corresponding heteroatom-doped carbon spheres with 28% nitrogen and 20.5% oxygen determined using CHNS analysis were attained by subjecting the polybenzoxazine particles to moderate carbonization conditions, resulting in the formation of a partial graphitic structure. The carbon structure with a moderate BET surface area of 221 m2 g–1 and high heteroatom content makes it a potential candidate for electrochemical energy storage. The electrochemical performance as a supercapacitor was evaluated using a three-electrode system where the doped carbon displayed an excellent specific capacitance of 728 F g–1 at 10 A g–1 current density in 0.1 M H2SO4 electrolyte, resulting in a high energy density of 56 W h kg–1 and power density of 14246 W kg–1. The electrochemical performance was further evaluated by using a flexible all-solid-state symmetric two-electrode system to simulate real-time analysis. The active material displayed an appreciable specific capacitance of 50.3 F g–1 at 0.2 A g–1. In addition, capacitance retention of ∼86% after 2500 cycles in the asymmetric two-electrode configuration also confirmed the reversible nature of the device, with negligible changes in the resistance values obtained before and after the cyclic tests. The as-synthesized multifunctional precursor-based polybenzoxazine particles for fabrication of N, O-codoped carbon framework presents itself as a promising active material for fabrication of supercapacitor electrodes.