Abstract:

Transition metal selenides have drawn extensive attention as electrode materials because of their narrower bandgap and linewidth, higher conductivity, larger interlayer spacing, lower cost, and better theoretical capacity. In this study, the FeSe₂ anode was designed to be doped with expanded graphite to form a three-dimensional conductive network structure composed of interpenetrated and stacked, expanded graphite sheets to address the issues of low-reversible capacity and poor cycle stability of FeSe₂ electrode materials. FeSe₂-C anode material was prepared using a simple and effective solvothermal technique. The crystal structure composition and microstructure morphology of the samples were evaluated using an X-ray diffractometer, scanning electron microscope, transmission electron microscope, N₂ isotherm adsorption, and other characterization methods. Meanwhile, electrochemical test techniques, including galvanostatic cycling with potential limitation, cyclic voltammetry, and alternating current impedance were used to study the impact of expanded graphite doping on the electrochemical properties of FeSe₂. The results demonstrate the hierarchical structure, outstanding lithium storage capacity, high electrochemical performance, and cycling stability of the FeSe₂-C electrode. The first coulombic efficiency is 71.1% at a current density of 0.1 A/g, while the first discharge-specific capacity can reach 720.5 mAh/g, and the charge-specific capacity can reach 512.3 mAh/g. After 1000 cycles at a current density of 5 A/g, the capacity was still 339.1 mAh/g, which is 8.5 times that of the pure FeSe₂ electrode material after the same number of cycles. Expanded graphite construction into a three-dimensional conductive network is a practical way to enhance FeSe₂'s electrochemical performance.

Key words: FeSe₂, three-dimensional conductive structure, transition metal selenides, lithium-ion batteries, electrochemical performances