In-situ sulfurization of Bi2Fe4O9/Bi25FeO40 electrode for high-performance supercapacitors

Poor conductivity limited the widespread application of metal oxide electrodes in the supercapacitors. High conductive metal sulfides facilitated the rapid ionic/electronic transfer and accelerated the reaction kinetics. Herein, a series of sulfurized Bi 2 Fe 4 O 9 /Bi 25 FeO 40 composites —-Bi 2 Fe 4 O 9 /Bi 25 FeO 40 /x%Bi 2 S 3 ( x = 0, 8, 16, 30) were synthesized and optimized with Bi 2 O 3, Fe 2 O 3 and S as the raw materials by solid phase reaction. The as-prepared Bi 2 Fe 4 O 9 /Bi 25 FeO 40 /x%Bi 2 S 3 ( x = 0, 8, 16, 30) powders appeared as the irregular particles with the sizes of 0.78–4.27 μm. Desirably, when x was 16, Bi 2 Fe 4 O 9 /Bi 25 FeO 40 /16%Bi 2 S 3 electrode exhibited a specific capacitance of 597.0 F/g and 132.5 F/g at 1.0 A/g in the three-electrode and two-electrode systems respectively, much higher than those of Bi 2 Fe 4 O 9 /Bi 25 FeO 40 /x%Bi 2 S 3 ( x = 0, 8, 30). Furthermore, the corresponding energy density was 73.6 Wh/kg at the power density of 999.8 W/kg and the capacity retention was 89.7% after 2000 cycles at 2.0 A/g. The joint contributions of high conductivity and low theory capacitance of Bi 2 S 3 phase may be responsible for the desirable high capacitance of optimal Bi 2 Fe 4 O 9 /Bi 25 FeO 40 /16%Bi 2 S 3 electrode.