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

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。

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.