Fe3O4 nanoparticles encapsulated in electrospun porous carbon fibers with a compact shell as high-performance anode for lithium ion batteries

Fe3O4 nanoparticles encapsulated in porous carbon fibers (Fe3O4@PCFs) as anode materials in lithium ion batteries are fabricated by a facile single-nozzle electrospinning technique followed by heat treatment. A mixed solution of polyacrylonitrile (PAN) and polystyrene (PS) containing Fe3O4 nanoparticles is utilized to prepare hybrid precursor fibers of Fe3O4@PS/PAN. The resulted porous Fe3O4/carbon hybrid fibers composed of compact carbon shell and Fe3O4-embeded honeycomb-like carbon core are formed due to the thermal decomposition of PS and PAN. The Fe3O4@PCF composite demonstrates an initial reversible capacity of 1015 mAh g−1 with 84.4% capacity retention after 80 cycles at a current density of 0.2 A g−1. This electrode also exhibits superior rate capability with current density increasing from 0.1 to 2.0 A g−1, and capacity retention of 91% after 200 cycles at 2.0 A g−1. The exceptionally high performances are attributed to the high electric conductivity and structural stability of the porous carbon fibers with unique structure, which not only buffers the volume change of Fe3O4 with the internal space, but also acts as high-efficient transport pathways for ions and electrons. Furthermore, the compact carbon shell can promote the formation of stable solid electrolyte interphase on the fiber surface.