Thermodynamics of the precipitation from Li-Fe（II）-P-H2O system at 298 K was investigated.The results demonstrate that LiFePO4 can be formed at room temperature under pH value of 0-11.3,and the impurities Li3PO4 and...Thermodynamics of the precipitation from Li-Fe（II）-P-H2O system at 298 K was investigated.The results demonstrate that LiFePO4 can be formed at room temperature under pH value of 0-11.3,and the impurities Li3PO4 and Fe（OH）2 will be yielded at pH value above 11.3 and 12.9,respectively.The optimum pH value for LiFePO4 precipitation is 8-10.5.Considering the low rate of phase transformation kinetics,metastable Li-Fe（II）-P-H2O system was also studied.The results indicate that equimolar ratio of co-precipitation precursor Fe3（PO4）2.8H2O and Li3PO4 cannot be obtained at the initial molar ratio 1：1：1 and 1：1：3 of Li：Fe：P.In contrast,equimolar ratio of the co-precipitation precursor can be yielded by adjusting the pH value to 7-9.2,matching the molar ratio 3：1：1 of Li：Fe：P,meaning that Li＋-excess is one of the essential conditions for LiFePO4 preparation by co-precipitation method.展开更多
The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and el...The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and electrochemical behaviors of Li[Ni1/3Mn1/3Co1/3]O2 were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FESEM） and electrochemical charge/discharge cycling tests. The results show that the difference in pretreatment process results in the difference in compound Li[Ni1/3Co1/3Mn1/3]O2 structure, morphology and the electrochemical characteristics. The Li[Ni1/3Mn1/3Co1/3]O2 prepared by solution phase route maintains the uniform spherical morphology of the [Ni1/3Co1/3Mn1/3]3O4, and it exhibits a higher capacity retention and better rate capability than that prepared by ball mill method. The initial discharge capacity of this sample reaches 178 mA-h/g and the capacity retention after 50 cycles is 98.7% at a current density of 20 mA/g. Moreover, it delivers high discharge capacity of 135 mA-h/g at a current density of 1 000 mA/g.展开更多
基金Project (2007CB613603) supported by the National Basic Research Program of China
文摘Thermodynamics of the precipitation from Li-Fe（II）-P-H2O system at 298 K was investigated.The results demonstrate that LiFePO4 can be formed at room temperature under pH value of 0-11.3,and the impurities Li3PO4 and Fe（OH）2 will be yielded at pH value above 11.3 and 12.9,respectively.The optimum pH value for LiFePO4 precipitation is 8-10.5.Considering the low rate of phase transformation kinetics,metastable Li-Fe（II）-P-H2O system was also studied.The results indicate that equimolar ratio of co-precipitation precursor Fe3（PO4）2.8H2O and Li3PO4 cannot be obtained at the initial molar ratio 1：1：1 and 1：1：3 of Li：Fe：P.In contrast,equimolar ratio of the co-precipitation precursor can be yielded by adjusting the pH value to 7-9.2,matching the molar ratio 3：1：1 of Li：Fe：P,meaning that Li＋-excess is one of the essential conditions for LiFePO4 preparation by co-precipitation method.
基金Project(20871101)supported by the National Natural Science Foundation of ChinaProject(2009WK2007)supported by Key Project of Science and Technology Department of Hunan Province,ChinaProject(CX2009B133)supported by Colleges and Universities in Hunan Province Plans to Graduate Research and Innovation,China
文摘The layered Li[Ni1/3Mn1/3Co1/3]O2 was separately synthesized by pretreatment process of ball mill method and solution phase route, using [Ni1/3Co1/3Mn1/3]3O4 and lithium hydroxide as raw materials. The physical and electrochemical behaviors of Li[Ni1/3Mn1/3Co1/3]O2 were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, field emission scanning electron microscopy （FESEM） and electrochemical charge/discharge cycling tests. The results show that the difference in pretreatment process results in the difference in compound Li[Ni1/3Co1/3Mn1/3]O2 structure, morphology and the electrochemical characteristics. The Li[Ni1/3Mn1/3Co1/3]O2 prepared by solution phase route maintains the uniform spherical morphology of the [Ni1/3Co1/3Mn1/3]3O4, and it exhibits a higher capacity retention and better rate capability than that prepared by ball mill method. The initial discharge capacity of this sample reaches 178 mA-h/g and the capacity retention after 50 cycles is 98.7% at a current density of 20 mA/g. Moreover, it delivers high discharge capacity of 135 mA-h/g at a current density of 1 000 mA/g.
