Thermally Tuned Oxygenated Covalent Triazine Framework via Self-Templating for Durable 3.8 V Aqueous Supercapacitor with Record Energy and Power Density

Abstract

High-voltage (>2 V) aqueous supercapacitors (SCs) showing high energy and power density offer a sustainable, safe, eco-friendly, and cost-effective alternative to organic electrolyte based SCs, bridging the gap between batteries and capacitors. Herein, we report modular synthesis of oxygen-rich covalent triazine frameworks (Oxy-CTFs) showing large surface area (2543 m2 g-1) and pore volume (2.95 cm3 g-1) via ZnCl2-mediated ionothermal polymerization using a cost-effective 2,5-dimethoxy terephthalonitrile monomer. Strategically embedded methoxy groups, serving as both monomer and soft self-template. Apart from its catalytic role, ZnCl2 as an activating agent/porogen, simultaneously inducing partial in-situ O-demethylation, carbonization, and structural rearrangement, enriching electroactive carbonyl/quinone species and graphitic carbon domains embedded with pyrrolic and pyridinic nitrogen functionalities in the resulted Oxy-CTFs. These features combinedly enhance charge-storage capability, ion-transport kinetics, and faradaic activities. In symmetric SC, the Oxy-CTFs deliver a record 3.1 V, capacitance of 238.9 F g-1, energy/power density of 79.4 Wh kg-1/386.5 W kg-1. In hybrid configuration, the voltage extends to 3.8 V achieving highest energy (92.2 Wh kg-1) and power (933.2 W kg-1) density. Remarkable cycling stability is demonstrated, with 93.2% capacity retention after 20,000 cycles (20 A g-1) and maintaining 95.5% after repeated 60,000 cycles with 714 days shelf-stored cell. This rational soft self-templating approach set a new performance benchmark in aqueous SCs research.