Macromolecular Engineering of Polyquinone-Based Electrode Materials for High-Energy Supercapacitors

Rational engineering of electrode materials and device configurations are significantly pivotal to develop high-energy supercapacitors without sacrificing strong power capability and long lifespan. Herein, a Schiff-base condensation between phthalaldehydes and anthraquinones was readily performed to yield chain-engineered polyquinones (PQs) with tailored redox-active multi-hydroxyl groups. Further in situ incorporation of conductive graphene into PQs produced the composites. The symmetric supercapacitor (SSC) based on two identical composite electrodes delivers an energy density of 9.3 W h kg –1 at a power density of 99.9 W kg –1 and 6.2 W h kg –1 at 4000.0 W kg –1, respectively, outperforming the pure PQ-based SSC (9.2 W h kg –1 at 150.2 W kg –1 and 3.2 W h kg –1 at 1515.8 W kg –1 ). Furthermore, the graphene/PQ composite coupled with a counter electrode of activated carbon (AC) was actualized to assemble an asymmetric supercapacitor (ASSC), which enables higher power and energy outputs (20.3 W h kg –1 at 350.2 W kg –1 and 10.3 W h kg –1 at 6980.2 W kg –1 ) compared to the SSC device. Finally, a lithium-ion capacitor (LIC) was constructed using a composite anode and an AC cathode. Remarkably, such a full-cell delivers an energy density up to 113.8 W h kg –1 at 180.8 W kg –1 and retains 59.2 W h kg –1 at 9063.4 W kg –1, much higher than its counterparts of ASSC, SSC, and many supercapacitors reported previously. This LIC also exhibits a nearly 80% of initial capacitance after running at 5 A g –1 over 2000 cycles, showcasing an excellent energy–power–lifespan combination.