Effect on the electrochemical performance of NaTi₂(PO₄)₃ modified by CO(NH₂)₂ as anode materials for rechargeable Na-ion batteries

In order to enhance the electrical conductivity and rate capability of NaTi₂(PO₄)₃ (NTP)as anode materials for aqueous rechargeable Na-ion batteries, the C/NTP composites were prepared by the solvothermal strategy using CO(NH₂)₂ as the carbon source. The crystal structure, surface morphology and electrochemical properties of the obtained CO(NH₂)₂/NaTi₂(PO₄)₃(C/NTP)composites were investigated by the XRD, SEM, TEM, Raman and constant current charge-discharge testing. The effect of heating rate at different stage on the content of carbon, the graphitization degree of coating layer and the electrochemical performance of C/NTP composites was carefully studied. The results show that below 400℃ the lower of the heating rate, the higher content of carbon remains in C/NTP, and the lower of the heating rate between 400℃ and 650℃, the higher graphitization degree of carbon coating obtained, which also can improve the electrochemical performance of C/NTP composites. The initial discharge capacity of the C/NTP composites treated at the heating rate of 2℃/min reaches 114.9 mAh·g^-1 at the current of 5C and maintain as 91.9 mAh·g^-1 after 30 cycles, and the discharge capacity even keeps 87 mAh·g^-1 at the current of 10C and 71 mAh·g^-1 at the current of 20C, which exhibites excellent cycle performance at high current rate.