Efficient resource utilization achieves simple synthesis of Fe3Se4@CNF for robust potassium-ion storage

Metal selenides with excellent storage capacities have attracted extensive attention in the field of potassium ion batteries (KIBs). As a typical metal selenide, Fe3Se4 has also been gradually used in KIBs. However, the synthesis process of metal selenides is usually complicated and requires a lot of selenium powder, which is time-consuming and causes the waste of resources. In this paper, an internal selenization strategy with an approximate stoichiometric ratio (1.3:1) of Se:Fe is proposed to synthesize Fe3Se4 composites, resulting in the efficient use of selenium powder to synthesize selenide. Most of Fe3Se4 particles are embedded in carbon fibers to obtain Fe3Se4@carbon nanofibers (Fe3Se4@CNFs). As anodes for KIBs, Fe3Se4@CNFs show improved electrochemical performances for K+ storage when compared with Fe@CNF-Se0.1–400 (external selenide products) with more particles on the surface. Fe3Se4@CNF show a reversible capacity of 278 mA h g−1 after 150 cycles at a current density of 0.1 A g−1 in KIBs. The enhanced capacities and stability of Fe3Se4@CNF can be attributed to the technique of internal selenization, which controls Fe3Se4 nanoparticles to better distribute in CNF. This study provides a new idea for the efficient synthesis of selenides and sulfides, and extends the application of selenides and sulfides.