In-situ generation of hollow FeOx nanoparticles within electrospun N-doped carbon nanofibers for high-performance lithium storage

Iron-based oxides are deemed the most promising anode materials for lithium-ion batteries because of their low cost and high theoretical capacity; however, they still have disadvantages such as large volume variations and poor conductivity. To overcome these disadvantages, we successfully designed and fabricated a unique hollow Fe/Fe2O3 heterostructure nanospheres within N-doped CNFs hybrid structure through electrospinning and in situ oxidation. By adjusting the annealing temperature, the synergistic modulation of phase and morphology from solid Fe nanoparticles to hollow Fe/Fe2O3 and hollow Fe2O3 nanospheres was realized, which improved the electrochemical lithium storage performance. Benefiting from the unique hollow Fe/Fe2O3 heterostructural nanospheres and the hybridisation with the N-doped carbon nanofibers, the Fe/Fe2O3@NCNFs electrode exhibited higher lithium storage capacity, superior rate capability and outstanding cycle stability, achieving a reversible capacity of 938.2 mAh g- 1 at 0.2 A g- 1 . Additionally, the Fe/Fe2O3@NCNFs electrode can still maintain a high capacity of 729.1 mAh g- 1 after 900 cycles at a high current density of 0.5 A g- 1 , with a capacity retention of 97 %. Notably, this novel strategy can generally be applied to the design of different hollow nanostructured iron-based oxides, which is extremely important for developing advanced electrodes for use highperformance energy storage devices.