Strong covalent interaction Fe2O3/nitrogen-doped porous carbon fiber hybrids as free-standing anodes for lithium-ion batteries

A simple and novel method that combines the electrospinning technology with nonaqueous sol–gel method is developed to incorporate Fe2O3 nanoparticles into ZIF-8-derived nitrogen-doped highly porous carbon fibers (NPCFs). The size of Fe2O3 nanoparticles is about 5 nm. The interfacial interaction between Fe2O3 and NPCFs is investigated by thermogravimetric analysis, Raman spectrum and X-ray photoelectron energy spectrum. We found that Fe2O3 nanoparticles are anchored strongly in the NPCFs through the Fe–O–C covalent bond. The impact of the Fe2O3 content in the composites on electrochemical performance is also studied. When served as the flexible and free-standing anode of lithium-ion batteries (LIBs), the Fe2O3/NPCFs-66.9% exhibits superior electrochemical performance with the high discharge capacity of 1351 mA h g−1 at 50 mA g−1, remarkable rate capability (337 mA h g−1 even at 5000 mA g−1), and stable cycling performance (1106 mA h g−1 after 100 cycles at 100 mA g−1). The excellent anodic property can be ascribed to the ultra-small size of Fe2O3 nanoparticles, and the one-dimensional (1D) structure combined with the excellent electrical conductivity of NPCFs matrix. Moreover, the robust interfacial interaction Fe–O–C bond can restrain the aggregation of Fe2O3 nanoparticles and accommodate the volume change. This can effectively maintain the integrity of the whole electrode during the long-term cycles. The results show that the composite may be considered as a promising anode material for advanced LIBs.