Improved electrochemical performance of graphene-integrated NaTi2(PO4)3/C anode in high-concentration electrolyte for aqueous sodium-ion batteries

Rechargeable aqueous sodium-ion batteries (SIBs) are urgently pursued as a low-cost candidate for grid-scale storage of intermittent renewable energies. NASICON-type NaTi2(PO4)(3) holds great promises as anode material for aqueous SIBs owing to the high theoretical capacity and low redox potential, but being severely challenged by poor cycling performance and low reaction kinetics. Herein, graphene-integrated NaTi2(PO4)(3) composite is prepared with a facile sol-gel approach as anode material for aqueous SIBs. Electrochemical properties of the material in high-concentration aqueous electrolyte (6 M NaClO4) are systematically investigated by using cycling voltammetry, galvanostatic technique and electrochemical impedance spectroscopy. It is found that it shows an improved charge/discharge performance with a high practical capacity of 104.6 mAh g(-1) at 100 mA g(-1), excellent high-rate capability with a reversible capacity of 88.0 mAh g(-1) at 2000 mA g(-1), and good cycling stability with 92% capacity retention after 100 cycles. The improved electrochemical performance is attributed to the synergetic contribution of carbon-blending nanostructure and high-concentration electrolyte, which largely enhances structural stability and reaction kinetics of the material. In addition, the redox mechanism is discussed based on experimental results from cyclic voltammetry and X-ray diffraction technique.