本研究以水熱法合成鈉超離子導體(NASICON)-磷酸鈉鈦，藉改變合成參數，如反應體積、反應時間、前驅物濃度及界面活性劑濃度，可獲得奈米顆粒；並添加不同比重之碳源進行碳包覆，增進其導電性，以利後續電池性能量測。經X光繞射儀(XRD)分析得知: 水熱法合成可獲得結晶性良好之磷酸鈉鈦；掃描式電子顯微鏡(SEM)觀察: 磷酸鈉鈦粉末之平均粒徑範圍約為100 ~ 500 nm。經碳包覆後，由拉曼(Ramam)光譜分析偵測出碳特徵訊號、熱重分析(TGA)得知包覆後碳含量依碳源添加量不同約3 wt%、6wt%，穿透式電子顯微鏡(TEM)觀察可確認碳包覆及其形貌。先後以三極式電化學系統量測循環伏安曲線、二級式鈕扣電池量測鈉離子電池之性能。最佳合成參數及碳包覆含量之樣品其於不同充放電速率(0.2、0.5、1、2、5C)下展現出優異電容量(121、114、110、102、67mAh/g)、庫倫效率除首圈外，皆高達99%以上、放電電容量維持率亦維持在95%以上；經200次充放電循環測試後，仍保持約82%之放電電容量，且由電化學交流阻抗分析表明，阻值無明顯上升，顯示以水熱法合成之鈉超離子導體(NASICON)-磷酸鈉鈦在作為水系鈉離子電池負極材料極具潛力。;Nano particle of sodium titanium phosphate belonging to sodium super-ionic conductor (NASICON)-type were successfully prepared by hydrothermal method under different synthetic parameters. With appropriate carbon-coating can improve material conductivity thus possibly suitable for making negative electrodes of sodium-ion batteries. From X-ray diffraction (XRD), which results revealed well crystalline structure of NaTi2(PO4)3 by hydrothermal method. Examination by field-emission scanning electron microscope (FE-SEM), the powders indicated their particle size in the range from 100 nm to 500 nm depending upon the experimental conditions. After coating by carbon, Raman spectroscopy demonstrated the D-band and G-band of carbon. The result of thermal gravimetric analysis (TGA) displayed that the carbon content was about 3wt%, 6wt% depending upon content of carbon source. The presence of carbon coating could be directly observed through by transmission electron microscope. Standard three-electrode cell was employed to conduct the cyclic voltammetry; two-electrode system via a coin cell was carried out for the test of battery performance, respectively. The optimal results revealed that C-coated nanoparticle NaTi2(PO4)3/C exhibited excellent electrochemical performance with high specific capacities (121, 114, 110, 102, 67mAh/g), high coulomb efficiency (99%) except first cycle and well discharge capacity retention (95%) at different charge/discharge rate (0.2, 0.5, 1, 2, 5C). A delivery of ~82% discharge capacity retention after 200 cycles and no obvious fading for impedance indicated that sodium titanium phosphate nano powders prepared in this work provided a potential material to prepare the anode used in aqueous sodium ion battery.
