Enhanced sodium ion batteries performance by the phase transition from hierarchical Fe2O3 to Fe3O4 hollow nanostructures

Hierarchical Fe 3 O 4 hollow nanostructures are synthesized from the phase transition of Fe 2 O 3 hollow nanostructures, which are prepared through a dissolution-recrystallization process. The hierarchical Fe 3 O 4 hollow nanostructures, applied as an anode material for Na-ion batteries, display good rate capability and cycling stability. The reversible capacity of 150   mAh/g at 100   mA/g after 50 cycles can be maintained for Fe 3 O 4 anode. The superior Na-ion storage properties of hierarchical Fe 3 O 4 could be largely ascribed to the stable electrode structure during Na-ion insertion and extraction process. On the contrary, Fe 2 O 3 anode exhibits a high initial discharge capacity (686   mAh/g), but it suffers from poor cycling stability due to the remarkable pulverization of the electrode.