A rapid and continuous method for production of LiFePO4/C nanoparticles in super heated water is described,wherein soluble starch was used as carbon precursor.The effects of pH,flow rate,temperature,and pressure on th...A rapid and continuous method for production of LiFePO4/C nanoparticles in super heated water is described,wherein soluble starch was used as carbon precursor.The effects of pH,flow rate,temperature,and pressure on the formation of LiFePO4/C particles were investigated.Results showed that the pH value was the key factor on the formation of phase pure LiFePO4,which only formed at pH=7;the LiFePO4/C occurred as particles with about 70-200 nm size and LiFePO4 was covered by a thin carbon layer;higher flow rate,higher pressure,and lower temperature led to smaller particles of LiFePO4/C.展开更多
LiFePO4/C was synthesized by high temperature solid-state method with cheap Fe2O3, LiH2PO4 and glucose as raw materials in absence of inert gas. The sample had ordered olivine-type structure other impurities character...LiFePO4/C was synthesized by high temperature solid-state method with cheap Fe2O3, LiH2PO4 and glucose as raw materials in absence of inert gas. The sample had ordered olivine-type structure other impurities characterized by the test of X-ray diffraction （XRD）. The charge-discharge test showed the sample could demonstrate 120.5 mAh/g at 0.2C rate with good cyclic capability. The powder microeleetrode cyclic voltammetry test indicated that the redox process of the sample had good reversibility.展开更多
Olivine-type LiFePO4/C composite cathode materials were synthesized by a solid-state reaction method in an inert atmosphere. The glucose was added as conductive precursors before the formation of the crystalline phase...Olivine-type LiFePO4/C composite cathode materials were synthesized by a solid-state reaction method in an inert atmosphere. The glucose was added as conductive precursors before the formation of the crystalline phase. The effects of glucose content on the properties of as-synthesized cathode materials were investigated. The crystal structure and the electrochemical performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser particle-size distribution measurement and electrochemical performance testing.The material has a single crystal oIivine structure with grain-sizes ca. 100-200 nm. SEM micrographs and the corresponding energy dispersive spectrometer (EDS) data confirm that the carbon particulates produced by glucose pyrogenation are uniformly dispersed among the LiFePO4 grains, ensuring a good electronic contact. Impedance spectroscopy was used to investigate the ohmic and kinetic contributions to the cell performance. It is found that increasing the carbon content leads to a reduction of the cell impedance due to the reduction of the charge transfer resistance. The galvanostatically charge and discharge tests show that the material obtained by adding 10% C (by mass) gives a maximum discharge capacity of 140.8 mA.h.g-1 at the same rate (C/10). The material also displays a more stable cycle-life than the others.展开更多
The influence of sintering temperature,carbon content and dispersive agent in ball-milling was investigated on the properties of Li Fe PO_4/C prepared using Fe_2O_3,NH_4H_2PO_4,Li_2CO_3 and glucose via solid state rea...The influence of sintering temperature,carbon content and dispersive agent in ball-milling was investigated on the properties of Li Fe PO_4/C prepared using Fe_2O_3,NH_4H_2PO_4,Li_2CO_3 and glucose via solid state reaction.X-ray powder diffraction,scanning electron microscopy and charge–discharge test were applied to the characterization of the Li Fe PO_4/C samples synthesized under different conditions.Sintering temperature affects the crystallite/particle size and degree of crystallinity of LiF eP O_4,formation of Fe_2 P and maintenance of carbon in LiF e PO_4/C.Carbon maintenance is favored by low sintering temperature,and 700 °C is optimum for synthesis of LiF eP O_4/C with superior electrochemical performance.A higher carbon content in the range of 4.48%–11.03% results in a better rate capability for Li Fe PO_4/C.The dispersive agent used in ball-milling impacts the existent state of carbon in the final product which subsequently determines its charge–discharge behavior.The sample prepared at700 °C by using acetone as the dispersive agent in ball-milling exhibits an excellent rate capability and capacity retention without any fade at 0.1C,1C and 2C,with corresponding average discharge capacities of 153.8,128.3and 121.0 m A·h·g^(-1),respectively,in the first 50 cycles.展开更多
基金Supported by Shanghai Special Foundation on Nanomaterials (0243nm305)
文摘A rapid and continuous method for production of LiFePO4/C nanoparticles in super heated water is described,wherein soluble starch was used as carbon precursor.The effects of pH,flow rate,temperature,and pressure on the formation of LiFePO4/C particles were investigated.Results showed that the pH value was the key factor on the formation of phase pure LiFePO4,which only formed at pH=7;the LiFePO4/C occurred as particles with about 70-200 nm size and LiFePO4 was covered by a thin carbon layer;higher flow rate,higher pressure,and lower temperature led to smaller particles of LiFePO4/C.
基金We are grateful for the financial support from the Natural Science Foundation of Hunan Province(Grant No.04JJ0388)and from Central South University.
文摘LiFePO4/C was synthesized by high temperature solid-state method with cheap Fe2O3, LiH2PO4 and glucose as raw materials in absence of inert gas. The sample had ordered olivine-type structure other impurities characterized by the test of X-ray diffraction （XRD）. The charge-discharge test showed the sample could demonstrate 120.5 mAh/g at 0.2C rate with good cyclic capability. The powder microeleetrode cyclic voltammetry test indicated that the redox process of the sample had good reversibility.
文摘Olivine-type LiFePO4/C composite cathode materials were synthesized by a solid-state reaction method in an inert atmosphere. The glucose was added as conductive precursors before the formation of the crystalline phase. The effects of glucose content on the properties of as-synthesized cathode materials were investigated. The crystal structure and the electrochemical performance were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser particle-size distribution measurement and electrochemical performance testing.The material has a single crystal oIivine structure with grain-sizes ca. 100-200 nm. SEM micrographs and the corresponding energy dispersive spectrometer (EDS) data confirm that the carbon particulates produced by glucose pyrogenation are uniformly dispersed among the LiFePO4 grains, ensuring a good electronic contact. Impedance spectroscopy was used to investigate the ohmic and kinetic contributions to the cell performance. It is found that increasing the carbon content leads to a reduction of the cell impedance due to the reduction of the charge transfer resistance. The galvanostatically charge and discharge tests show that the material obtained by adding 10% C (by mass) gives a maximum discharge capacity of 140.8 mA.h.g-1 at the same rate (C/10). The material also displays a more stable cycle-life than the others.
基金Supported by the Natural Science Foundation of Yunnan Province(2010ZC051)the Analysis and Testing Foundation(20140439)the Starting Research Fund from Kunming University of Science and Technology(14118245)
文摘The influence of sintering temperature,carbon content and dispersive agent in ball-milling was investigated on the properties of Li Fe PO_4/C prepared using Fe_2O_3,NH_4H_2PO_4,Li_2CO_3 and glucose via solid state reaction.X-ray powder diffraction,scanning electron microscopy and charge–discharge test were applied to the characterization of the Li Fe PO_4/C samples synthesized under different conditions.Sintering temperature affects the crystallite/particle size and degree of crystallinity of LiF eP O_4,formation of Fe_2 P and maintenance of carbon in LiF e PO_4/C.Carbon maintenance is favored by low sintering temperature,and 700 °C is optimum for synthesis of LiF eP O_4/C with superior electrochemical performance.A higher carbon content in the range of 4.48%–11.03% results in a better rate capability for Li Fe PO_4/C.The dispersive agent used in ball-milling impacts the existent state of carbon in the final product which subsequently determines its charge–discharge behavior.The sample prepared at700 °C by using acetone as the dispersive agent in ball-milling exhibits an excellent rate capability and capacity retention without any fade at 0.1C,1C and 2C,with corresponding average discharge capacities of 153.8,128.3and 121.0 m A·h·g^(-1),respectively,in the first 50 cycles.
基金Foundation item： National Natural Science Foundation of China （51002051） Fundamental Research Funds for the Cenlxal Universities （WA1014016） Science and Technology Commission of Shanghai Municipality （09520500900）
