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 NaTi 2 (PO 4 ) 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 NaTi 2 (PO 4 ) 3 /C 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 NaClO 4 ) 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.