固相反应条件对磷酸铁锂电化学性能的影响

以碳酸锂(Li₂CO₃)为锂源, 磷酸二氢铵(NH₄H₂PO₄)为磷源, 草酸亚铁(FeC₂O₄·2H₂O)为铁源, 柠檬酸(C₆H₈O₇·H₂O)为碳源, 采用固相反应法制备橄榄石晶型磷酸铁锂。利用X射线衍射仪, 扫描电子显微镜, 能谱仪, 比表面积分析仪和电化学测试等设备和方法对磷酸铁锂材料的物相组成、结构、形貌和电化学性能进行表征, 研究煅烧温度和保温时间对磷酸铁锂电化学性能的影响, 并通过添加碳对试样进行包覆改性。结果表明, 在煅烧温度为700℃, 保温时间为12 h条件下制备的磷酸铁锂正极材料的电化学性能良好, 碳包覆能有效改善电极材料的性能。包覆碳后的磷酸铁锂电极材料在0.2C充电电流密度下首次放电比容量可达319.2 mAh·g-1; 在1C充电电流密度下循环100次后, 放电比容量保持在168.1 mAh·g-1。

Effects of solid phase reaction conditions on electrochemical performance of lithium iron phosphate

The lithium iron phosphate in olivine crystal structure was prepared by solid phase reaction method, using lithium carbonate(Li₂CO₃) as the lithium source, ammonium dihydrogen phosphate(NH₄H₂PO₄) as the phosphorus source, ferrous oxalate(FeC₂O₄·2H₂ O) as the iron source, and citric acid(C₆H₈O₇·H₂O) the carbon source. The phase composition, structure, morphology, and electrochemical properties of the synthesized lithium iron phosphate material were characterized by X-ray diffractometer(XRD), scanning electron microscope(SEM), energy dispersive spectroscope(EDS), specific surface area analyzer(BET), and electrochemical test. The effects of calcination temperature and holding time in solid phase reaction on the electrochemical performance of lithium iron phosphate were investigated, and the synthesized samples were modified by carbon coating. The results show that the lithium iron phosphate cathode material prepared at the calcination temperature of 700 ℃ and the holding time of 12 h has the best electrochemical performance and the carbon coating can effectively improve the performance of the electrode material. The lithium iron phosphate electrode material coated with carbon has a first discharge specific capacity of 319.2 mAh·g-1 at a charging current density of 0.2 C. After circulating 100 times at a charging current density of 1 C, the discharge specific capacity is maintained at 168.1 mAh·g-1.