Fishnet-like double active layer-loaded carbon fiber for electrical double-layer capacitors.

The rational design and controllable synthesis of high-performance energy storage materials are important measures to address the growing demand for energy storage devices. This work involves the growth of a fishnet-like FeO nanorod@oxygen-rich carbon layer structure directly onto carbon fiber cloth as a binder-free electrode for symmetric capacitors. The growth of FeO nanorods provided a large specific surface area, and the coating of an oxygen-rich carbon layer protected the FeO nanorods as an active substance. Furthermore, oxidation treatment created rich electrochemically active sites by loading oxygen-containing functional groups onto the composite surface. As a result, the optimal OC@FeO-ACC sample exhibited a high areal specific capacitance of 1687 mF cm at a current density of 1 mA cm. Meanwhile, an excellent capacity retention rate of 58.7% was achieved at 15 mA cm. Finally, the long-term cycling stability was verified with an 80% retention rate of the initial capacitance after 12 000 cycles.