| Summary: | 碩士 === 國立中央大學 === 材料科學與工程研究所 === 102 === 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.
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