Anatase TiO2 as an Anode Material for Rechargeable Aqueous Aluminum-Ion Batteries: Remarkable Graphene Induced Aluminum Ion Storage Phenomenon

The electrochemical intercalation and extraction of Al3+ ion in anatase TiO2 is illustrated in various aqueous electrolytes in an attempt to demonstrate the viability of TiO2 as an anode material for rechargeable aqueous aluminum-ion batteries. It is well understood that the primary barrier for diffusion of Al3+ ion in TiO2 is the poor electronic conductivity of TiO2. It is revealed that a small fraction of graphene (<2 wt %) could induce ultrafast diffusion of Al3+ ion in TiO2. Estimation shows that graphene remarkably enhances the Al3+ ion diffusion coefficient in TiO2 by 672 times. Discharge capacities in the range of 33–50 mAhg–1 are obtained at a high current rate of 6.25Ag–1for graphene incorporated TiO2. It is also seen that the nature of electrolytes critically influences the Al3+ ion insertion phenomenon. The possibility of reversible crystal phase transition of TiO2 to aluminium titanate due to Al3+ ion intercalation-extraction is also demonstrated for the first time.