Controlled synthesis of Fe3O4 microparticles with interconnected 3D network structures for high-performance flexible solid-state asymmetric supercapacitors

The eco-friendly Fe-based oxides have attracted broad attention in supercapacitors on account of large theoretical capacities and cost-effective technologies associated with production and recycling. However, inferior conductivity and bad structural stability are still the main obstacles for its promoted application than the competition. In this work, well-designed Fe 3 O 4 microparticles with homogeneous size distribution, high crystallinity, and amorphous carbon shell have been synthesized and deposited on carbon fabric as an anode electrode via a series of feasible techniques, including anodic electrodeposition , polymerization, and annealing. The interconnected 3D network structures of electroactive materials are featured by high specific surface area and fast diffusion rate of ions. The sufacial carbon layer of Fe 3 O 4 particles, serves as the armor, which not only boosts electrical conductivity , but also maintains structural stability of the electrode during electrochemical processes. The electrochemical results show that the binder-free anode exhibits a remarkable areal capacitance of 0.95 F·cm −2 , a wide potential window of 1.2 V, and an outstanding cycling stability in 1 M KOH electrolyte (capacitance retention of 93.39 % over 8000 charge-discharge cycles). After combining with a NiCo-based cathode, 4.93 F·cm −3 volumetric capacitance, 1.8 mWh·cm −3 energy density , and 198 mW·cm −3 power density are achieved for the flexible solid-state asymmetric supercapacitor , which displays impressive cycling stability, excellent mechanical flexibility, and obvious performance advantages as compared with previously reported flexible energy storage devices. This work provides a feasible strategy to design a flexible Fe-based anode with superior conductivity and long-term stability for high-performing flexible solid-state asymmetric supercapacitor towards practical applications.