One-pot co-precipitation synthesis of Fe₃O₄ nanoparticles embedded in 3D carbonaceous matrix as anode for lithium ion batteries

Fe₃O₄@C nanoparticles with a 3D net-like structure were synthesized via a facile and scalable one-pot co-precipitation followed by a subsequent carbonization in an Ar atmosphere. Verified by scanning and transmission electron microscopy characterization, it can be seen that Fe₃O₄ nanoparticles with the size of 10–15 nm were embedded in a uniform carbon shell with a thickness of around 2 nm. Furthermore, the corresponding XRD and EDS analysis combined with TEM images also proved that the thin carbon layer on the nano-scale Fe₃O₄ was amorphous. The charge/discharge tests showed that Fe₃O₄@C composite delivered an excellent reversible capacity of 980 mAh g⁻¹ after 100 cycles at a current density of 92.4 mA g⁻¹, which was much higher than that of the pure Fe₃O₄ (170 mAh g⁻¹) synthesized by the same method. The outstanding reversible capacity is attributed to the small size of Fe₃O₄ particles and the high conductivity and mechanical strength of the amorphous carbon layer, which accelerates the electron transfer and relieves structure collapse caused by mechanical stress, thus maintaining a superior electrochemical stability.