Olivine structured LiFePO 4 /C (lithium iron phosphate) and Mn 2+ -doped LiFe 0.98 Mn 0.02 PO 4 /C powders were synthesized by the solid-state reaction. The effects of manganese partial substitution and different carb...Olivine structured LiFePO 4 /C (lithium iron phosphate) and Mn 2+ -doped LiFe 0.98 Mn 0.02 PO 4 /C powders were synthesized by the solid-state reaction. The effects of manganese partial substitution and different carbon content coating on the surface of LiFePO 4 were considered. The structures and electrochemical properties of the samples were measured by X-ray diffraction (XRD), cyclic voltammetry (CV), charge/discharge tests at different current densities, and electrochemical impedance spectroscopy (EIS). The electrochemical properties of LiFePO 4 cathodes with x wt.% carbon coating (x= 3, 7, 11, 15) at =0.2C, 2C (1C= 170 mAh·g 1 ) between 2.5 and 4.3 V were investigated. The measured results mean that the LiFePO 4 with 7 wt.% carbon coating shows the best rate performance. The discharge capacity of LiFe 0.98 Mn 0.02 PO 4 /C composite is found to be 165 mAh·g 1 at a discharge rate, = 0.2C, and 105 mAh·g 1 at =2C, respectively. After 10 cycles, the discharge capacity has rarely fallen, while that of the pristine LiFePO 4 /C cathode is 150 mAh·g 1 and 98 mAh·g 1 at =0.2 and 2C, respectively. Compared to the discharge capacities of both electrodes above, the evident improvement of the electrochemical performance is observed, which is ascribed to the enhancement of the electronic conductivity and diffusion kinetics by carbon coating and Mn 2+-substitution.展开更多
基金supported by the National Science Foundation for Young Scholars (No. 11004032)National Natural Science Foundation of China (No. 11074039)Fujian Province Science Foundation for Young Scholars (No.2008F3039)
文摘Olivine structured LiFePO 4 /C (lithium iron phosphate) and Mn 2+ -doped LiFe 0.98 Mn 0.02 PO 4 /C powders were synthesized by the solid-state reaction. The effects of manganese partial substitution and different carbon content coating on the surface of LiFePO 4 were considered. The structures and electrochemical properties of the samples were measured by X-ray diffraction (XRD), cyclic voltammetry (CV), charge/discharge tests at different current densities, and electrochemical impedance spectroscopy (EIS). The electrochemical properties of LiFePO 4 cathodes with x wt.% carbon coating (x= 3, 7, 11, 15) at =0.2C, 2C (1C= 170 mAh·g 1 ) between 2.5 and 4.3 V were investigated. The measured results mean that the LiFePO 4 with 7 wt.% carbon coating shows the best rate performance. The discharge capacity of LiFe 0.98 Mn 0.02 PO 4 /C composite is found to be 165 mAh·g 1 at a discharge rate, = 0.2C, and 105 mAh·g 1 at =2C, respectively. After 10 cycles, the discharge capacity has rarely fallen, while that of the pristine LiFePO 4 /C cathode is 150 mAh·g 1 and 98 mAh·g 1 at =0.2 and 2C, respectively. Compared to the discharge capacities of both electrodes above, the evident improvement of the electrochemical performance is observed, which is ascribed to the enhancement of the electronic conductivity and diffusion kinetics by carbon coating and Mn 2+-substitution.
