A synergetic promotion of sodium-ion storage in titania nanosheets by superlattice assembly with reduced graphene oxide and Fe-doping strategy.

A synergetic promotion of sodium ion storage in the titania nanosheets has been achieved by doping the oxide nanosheets with Fe and heteroassembling them with the conductive reduced graphene oxide, showing an over 6 folds capacity enhancement compared with the original titania nanosheets. • A joint promotion improved sodium ion storage in titania nanosheets over 6 folds. • rGO stabilized structure and increased electrical conductivity of the composites. • Fe doping improved capacity of composites to 378.8 mA h g−1 at 0.1 A g−1. • Ti 0.67 Fe 0.3 O 2 /rGO showed a capacity of 287.4 mA h g−1 at 1 A g−1 after 3000 cycles. Titania has been taken as one promising anode material for sodium ion batteries because of its long cycling stability and suitable working voltage. One of the main bottlenecks for its use is the low capacity. To overcome this challenge, in this work, restacked two dimensional (2D) titania nanosheets, which has an open edge and enlarged interlayer spacing for the ion diffusion, have been doped with Fe elements and hetero-assembled with the conductive reduced graphene oxide (rGO). The conductive rGO added increased the charge transfer at the interface of anode and electrolyte, decreased the diffusion barrier of Na+ inside the composites and increased the stability of titania nanosheet during the charge and discharge process, increasing the capacity and long cycle stability of the anode. The high concentration doping of Fe in the titania nanosheets further decreased the Na+ diffusion barrier, increased the electrical conductivity of the composites and greatly increased the storage sites of Na+. The as obtained superlattice composites of Ti 0.67 Fe 0.3 O 2 /rGO showed a sodium ion capacity of 378.8 mA h g−1 at 0.1 A g−1 after 100 cycles, which is the highest values among all reported Ti and Fe oxide materials. It still delivered a stable capacity of 287.4 mA h g−1 at high current charge density (1 A g−1) after a long cycling process (3000 cycles). [ABSTRACT FROM AUTHOR]