Properties of two LiFePO4/C composites with low carbon content synthesized from precursors dried by spray drying and blast drying are investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy...Properties of two LiFePO4/C composites with low carbon content synthesized from precursors dried by spray drying and blast drying are investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and electrochemical measurements. The two samples have a different morphology and particle size, while the structure of LiFePO4 is unaffected. The LiFePO4/C composite prepared from the precursor dried by blast drying has a much lower surface resistance and a much better rate capability because the deposited carbon is more graphite-like and more conductive. The cycling performance is also much better for the LiFePO4/C composite prepared from the precursor dried by blast drying because only a slight impedance growth is involved upon cycling. These results suggest that the precursor drying process has a significant impact on the properties of LiFePO4/C composite, and its effect is highly dependent on the carbon content.展开更多
The anoxic decomposition and influence of carbon precursors on the properties of LiFePO_4/C prepared by using Fe_2O_3 were investigated.X-ray powder diffractometry,Fourier transform infrared spectroscopy(FTIR),scannin...The anoxic decomposition and influence of carbon precursors on the properties of LiFePO_4/C prepared by using Fe_2O_3 were investigated.X-ray powder diffractometry,Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM) and carbon content and charge–discharge tests were applied to the characterization of the as-synthesized cathodes.Partial carbon is lost in the anaerobic decomposition of organic precursors and a high hydrogen content leads to a high residual carbon rate.Pyromellitic anhydride and citric acid participate in reactions before and in ball-milling.All the chosen carbon precursors are capable of producing LiFePO_4 with high degree of crystallinity and purity.The carbon derived from α-D-glucose,pyromellitic anhydride,soluble starch,citric acid and polyacrylamide has a loose and porous texture in LiFePO_4/C which forms conduction on and between LiFePO_4 particles.LiFePO_4/C prepared by using α-D-glucose,pyromellitic anhydride,citric acid and sucrose exhibits appreciable electrochemical performance.Graphite alone is able to enhance the electrochemical performance of LiFePO_4 to a limited extent but incapable of preparing practical cathode.展开更多
LiNi0.5Mn1.5O4 was synthesized by two different coprecipitation methods:composite carbonate process and composite hydroxide method. The effects of calcination temperature of precursors on the physical properties and e...LiNi0.5Mn1.5O4 was synthesized by two different coprecipitation methods:composite carbonate process and composite hydroxide method. The effects of calcination temperature of precursors on the physical properties and electrochemical performance of the samples were investigated. The results of scanning electron microscopy(SEM) show that as calcination temperature increases,the crystallinity of the samples is improved,and their grain sizes are obviously increased. X-Ray diffraction(XRD) data show that the LiNi0.5Mn1.5O4 compounds obtained by two coprecipitation methods both exhibit a pure cubic spinel structure without any impurities. Furthermore,it is found that the samples prepared with relatively high temperature precursors present large initial discharge capacity(>125 mA·h/g) and excellent cycling stability with a capacity retention rate larger than 91% after 30 cycles at current density of 1 C. This probably derives from their higher crystallinity and larger grain sizes. However,the initial discharge capacity of LiNi0.5Mn1.5O4 synthesized by composite carbonate process is smaller than that prepared by composite carbonate process,but it shows better capacity retention ability.展开更多
基金supported by the National Natural Science Foundation of China(No.52004076)the Science and Technology Base and Talent Project of Guangxi,China(No.GUIKEAD20159049)the Guangxi Natural Science Foundation,China(No.2020GXNSFAA297054)。
基金supported by the National Key Basic Research and Development Plan (2011CB935904)
文摘Properties of two LiFePO4/C composites with low carbon content synthesized from precursors dried by spray drying and blast drying are investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and electrochemical measurements. The two samples have a different morphology and particle size, while the structure of LiFePO4 is unaffected. The LiFePO4/C composite prepared from the precursor dried by blast drying has a much lower surface resistance and a much better rate capability because the deposited carbon is more graphite-like and more conductive. The cycling performance is also much better for the LiFePO4/C composite prepared from the precursor dried by blast drying because only a slight impedance growth is involved upon cycling. These results suggest that the precursor drying process has a significant impact on the properties of LiFePO4/C composite, and its effect is highly dependent on the carbon content.
基金Project(2010ZC051)supported by Natural Science Foundation of Yunnan Province,ChinaProject(20140439)supported by Analysis and Testing Foundation of Kuming University of Science and Technology,ChinaProject(14118245)supported by the Starting Research Fund from Kunming University of Science and Technology,China
文摘The anoxic decomposition and influence of carbon precursors on the properties of LiFePO_4/C prepared by using Fe_2O_3 were investigated.X-ray powder diffractometry,Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM) and carbon content and charge–discharge tests were applied to the characterization of the as-synthesized cathodes.Partial carbon is lost in the anaerobic decomposition of organic precursors and a high hydrogen content leads to a high residual carbon rate.Pyromellitic anhydride and citric acid participate in reactions before and in ball-milling.All the chosen carbon precursors are capable of producing LiFePO_4 with high degree of crystallinity and purity.The carbon derived from α-D-glucose,pyromellitic anhydride,soluble starch,citric acid and polyacrylamide has a loose and porous texture in LiFePO_4/C which forms conduction on and between LiFePO_4 particles.LiFePO_4/C prepared by using α-D-glucose,pyromellitic anhydride,citric acid and sucrose exhibits appreciable electrochemical performance.Graphite alone is able to enhance the electrochemical performance of LiFePO_4 to a limited extent but incapable of preparing practical cathode.
基金Project(2007CB613607) supported by the National Basic Research Program of China
文摘LiNi0.5Mn1.5O4 was synthesized by two different coprecipitation methods:composite carbonate process and composite hydroxide method. The effects of calcination temperature of precursors on the physical properties and electrochemical performance of the samples were investigated. The results of scanning electron microscopy(SEM) show that as calcination temperature increases,the crystallinity of the samples is improved,and their grain sizes are obviously increased. X-Ray diffraction(XRD) data show that the LiNi0.5Mn1.5O4 compounds obtained by two coprecipitation methods both exhibit a pure cubic spinel structure without any impurities. Furthermore,it is found that the samples prepared with relatively high temperature precursors present large initial discharge capacity(>125 mA·h/g) and excellent cycling stability with a capacity retention rate larger than 91% after 30 cycles at current density of 1 C. This probably derives from their higher crystallinity and larger grain sizes. However,the initial discharge capacity of LiNi0.5Mn1.5O4 synthesized by composite carbonate process is smaller than that prepared by composite carbonate process,but it shows better capacity retention ability.
