Confined oriented growth of FeSe2 on a porous graphene film as a binder-free anode for high-rate lithium-ion batteries

Abstract

FeSe₂ nanorod@porous graphene films (FeSe₂@PG) were prepared by simple vacuum filtration, annealing, and subsequent selenylation. These FeSe₂ nanorods were formed via confined oriented growth of FeSe₂ nanoparticles. The morphology of FeSe₂@PG was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The interfacial interaction between FeSe₂ and graphene was investigated using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. When used as an anode in lithium-ion batteries, the FeSe₂@PG electrode exhibited an initial reversible capacity of 858 mA h g⁻¹, which was increased to 1053 mA h g⁻¹ after 50 cycles at 100 mA g⁻¹. At high rates of 1, 2, 5, and 10 A g⁻¹, the electrode maintained specific capacities of 483, 313, 265, and 178 mA h g⁻¹, respectively, even after 1000 cycles. The excellent electrochemical performance of the FeSe₂@PG electrode is attributed to the special structure of FeSe₂@PG and the strong covalent bonds between graphene and FeSe₂. Moreover, graphene can not only act as a substrate for the growth of FeSe₂ nanorods, but also improve the conductivity of FeSe₂. Furthermore, the porous structure of graphene can reduce the diffusion path of lithium ions and improve the penetration of the electrolyte into the graphene layer. In addition, a new covalent bond of C–Se–Fe was formed between graphene and FeSe₂, which was beneficial for maintaining its structural stability.