Study of the electrochemical properties of Fe3O4/C–Bi composites prepared by spray drying and their use in cylindrical sealed nickel iron batteries

In this paper, Fe₃O₄/C–Bi composites with carbon coating and bismuth added were prepared by step-by-step precipitation, spray carbon coating drying and high temperature treatment. The composite materials are spherical particles, which are composed of primary nanoparticles coated with carbon, and the thickness of the carbon coating layer is 2 nm. Electrochemical test results show that the synergistic effect of Bi and C can effectively inhibit hydrogen evolution and passivation of iron electrodes. The Fe₃O₄/C–Bi composite materials have excellent electrochemical properties, among which the Fe₃O₄/C–Bi(5%) electrode has the best performance. At a current density of 300 mA g^?1, the discharge capacitance is close to 700.0 mAh g^?1, the coulombic efficiency is as high as 95.2%, and the rate performance is also excellent. At a current density of 2400 mA g^?1, the discharge capacity reaches 500.0 mAh g^?1. AA600 cylindrical iron nickel batteries prepared with an Fe₃O₄/C–Bi(5%) composite as the active material for iron negative electrodes realized sealing for the first time.