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Lithium iron phosphate (LiFePO4) was synthesized from LiOH, FeSO4 and H3PO4 by a hydrothermal process at 180℃. The samples were characterized by X-ray diffraction, scanning electron microscopy and chemical analysis. Electrochemical performance of the samples was tested in terms of charge-discharge capacity and cycling behavior. The results indicated that Fe(III) impurity had obvi- ously effect on the electrochemical properties of LiFePO4, and the formation of Fe3+ was caused by the oxidation of Fe2+ in the dissolving and feeding processes accompanying the increase of pH value. It was found that the precipitation separation was effective in decreasing the content of Fe3+ in the solu- tion of FeSO4 and the sealed feeding was useful in preventing the conversion of Fe2+ to Fe3+. When the content of Fe3+ < 0.5 wt%, the hydrothermally synthesized LiFePO4 calcined at 750℃ with sucrose as carbon source exhibited an initial discharge capacity of 154.9 mAh·g-1 at the rate of 0.1 C (1 C = 150 mA·g-1) and the cycling retention rate could reach 98% after 50 cycles at room temperature.
Lithium iron phosphate (LiFePO4) was synthesized from LiOH, FeSO4 and H3PO4 by a hydrothermal process at 180 ° C. The samples were characterized by X-ray diffraction, scanning electron microscopy and chemical analysis. Electrochemical performance of the samples was tested in terms of charge -discharge capacity and cycling behavior. The results indicated that Fe (III) impurity had obvi- ously effect on the electrochemical properties of LiFePO4, and the formation of Fe3 + was caused by the oxidation of Fe2 + in the dissolving and feeding processes accompanying the increase of pH value. It was found that the precipitation separation was effective in decreasing the content of Fe3 + in the solu- tion of FeSO4 and the sealed feeding was useful in preventing the conversion of Fe2 + to Fe3 +. When the content of Fe3 + <0.5 wt% the hydrothermally synthesized LiFePO4 calcined at 750 ℃ with sucrose as carbon source exhibited an initial discharge capacity of 154.9 mAh · g-1 at the rate of 0.1 C (1 C = 15 0 mA · g-1) and the cycling retention rate could could reach 98% after 50 cycles at room temperature.