TiNb2O7/graphene composites as high-rate anode materials for lithium/sodium ion batteries

Abstract

Layered TiNb₂O₇/graphene composites (TNO/G) were synthesized through simple direct dispersion and blending in an aqueous solvent followed by a freeze drying process and an annealing treatment under Ar. The graphene sheets are well separated by TiNb₂O₇ (TNO) nanoparticles, and simultaneously, the TNO particles are uniformly anchored between the graphene sheets. The combined advantages of graphene sheets and TNO, such as the weight ratio and layered structure, exhibit tremendous benefits for high rate Li ion capability reaching around 180 mA h g⁻¹ at a current density of 38.7 A g⁻¹ (100C rate). Through the synergistic effects of their combination the total specific capacity of TNO/G is higher than the sum of the specific capacity of pure TNO and graphene in their relative ratios. For the study of Na ion capability, as graphene is an active material during the de-sodiation process, a reversible capacity of 340.2 mA h g⁻¹ was obtained from this TNO/G at a current density of 25 mA g⁻¹. Even at a higher current density of 200 mA g⁻¹, a stable capacity of 200 mA h g⁻¹ can still be obtained. These findings demonstrate the great potential of TNO/G for lithium/sodium ion anodes.