Flexible asymmetric supercapacitors made of 3D porous hierarchical CuCo2O4@CQDs and Fe2O3@CQDs with enhanced performance

Flexible asymmetric supercapacitors (FASCs) have attracted increasing interest in portable and wearable electronics. The practical application of FASCs in high energy density devices is limited by their low specific capacity, which can be effectively addressed by designing electrode materials hierarchically on the micro-nanoscale. Herein, well-defined 3D porous hierarchical CuCo2O4@carbon quantum dots (CQDs) and Fe2O3@CQDs architectures are rationally synthesized through a simple CQDs-induced hydrothermal self-assembly technique. Both of the as-prepared CuCo2O4@CQDs and Fe2O3@CQDs electrodes exhibit improved specific capacity, desirable rate capability and complementary potential range. A FASC (CuCo2O4@CQDs//Fe2O3@CQDs) on graphite paper delivers a high operation voltage of 1.55 V, an energy density of 39.5 Wh kg−1 at 1203.7 W kg−1, and long cycling lifespan. The excellent performance is ascribed to the good electronic conductivity with the assistance of CQDs and their unique 3D mesoporous structures with extraordinary specific surface area, which could provide fruitful active sites for electrochemical reactions. The newly developed FASC based on the Faradaic-type electrodes is inspiring, and would be promising for the applications in wearable electronic devices.