尿素改性对钠离子电池负极材料NaTi_2(PO_4)_3电化学性能的影响

Effect on the electrochemical performance of NaTi_2(PO_4)_3 modified by CO(NH_2)_2 as anode materials for rechargeable Na-ion batteries

为提高水溶液钠离子电池负极材料NaTi_2(PO_4)_3(NTP)的导电性和倍率性能,以尿素(CO(NH_2)_2)为碳源采用溶剂热法合成了CO(NH_2)_2/NaTi_2(PO_4)_3(C/NTP)复合负极材料。采用XRD、SEM、TEM、Raman和恒流充放电等手段分析了材料的结构、C/NTP形貌和电化学性能。研究了不同阶段升温速率对C含量、包覆层石墨化程度及对电化学性能的影响。实验结果表明,低于400℃升温速率越小,C/NTP残碳量越高;400~650℃之间升温速率越小,包覆层石墨化程度越高,并提高了其电化学性能;在5C倍率下2℃/min热处理的样品首圈放电比容量为114.9mAh·g^(-1),循环30次后容量保持在91.9mAh·g^(-1);10C下放电比容量为87mAh·g^(-1),20C下放电比容量仍保持在71mAh·g^(-1),展现出高倍率下优异的循环性能。

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 o{ C/NTP composites. The initial dis- charge 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 91.9mAh·g^-1 after 30 cycles, and the discharge capacity even keeps 87 mAh·g^-1 at the current of 10C and 71mAh·g^-1 at the current of 20C, which exhibites excellent cycle performance at high current rate.