Li Fe PO4/C was prepared via solid state reaction and characterized with X-ray powder diffraction and charge–discharge test. As-prepared Li Fe PO4/C has a triphylite structure and exhibits an excellent rate capabilit...Li Fe PO4/C was prepared via solid state reaction and characterized with X-ray powder diffraction and charge–discharge test. As-prepared Li Fe PO4/C has a triphylite structure and exhibits an excellent rate capability and capacity retention. Electrochemical impedance spectroscopy(EIS) was applied to investigate LixFe PO4/C(0<x<1) electrode on temperature variation. The valid equivalent circuit for EIS fitting was determined which contains an intercalation capacitance for Li+ ion accumulation and consumption in the electrode reaction. The surface layer impedance needs to be included in the equivalent circuit when Li Fe PO4/C is deeply delithiated at a relatively high temperature. EIS examination indicates that a temperature rise leads to a better reversibility, lower charge transfer resistance, higher exchange current density J0 and greater Li+ ion diffusion coefficient for the LixFe PO4/C electrode process. The Li+ ion concentration in LixFe PO4/C is potential to impact the Li+ ion diffusion coefficient, and a decrease in the former results in an increase in the latter.展开更多
CoSn alloy and Cu-Sn samples were syn thesized by H 2 -reduction following solid-state r eaction between Co ?,Cu?,Sn?and NaOH at ambient temperature.The samples were characterized by XRD,S EM.The results showed that C...CoSn alloy and Cu-Sn samples were syn thesized by H 2 -reduction following solid-state r eaction between Co ?,Cu?,Sn?and NaOH at ambient temperature.The samples were characterized by XRD,S EM.The results showed that CoSn alloy(80～200nm)is globe-shaped,ultrafine hexagon al material,and Cu-Sn alloy powder consists of two phases,i.e.Cu 6 Sn 5 and Cu 3 Sn.Cu-Sn powder has spherical morphology and the particle size is estimated to be 60～70nm.The electro chemical performances of CoSn alloy and Cu-Sn powder were studied using lithium-ions model cell Li /LiPF 6 (EC +DMC)/CoSn(or Cu-Sn).It was demonstrated the reversible discharge capacities for 10cycles keep above 280mAh ·g -1 for nanophase Cu-Sn,and 60mAh ·g -1 for CoSn alloy.Differ-ential capacity plots showed that th e reaction mechanisms of Cu-Sn with l ithium were reversible.展开更多
基金Project(2010ZC051)supported by the Natural Science Foundation of Yunnan Province,ChinaProject(20140439)supported by Analysis and Testing Foundation from Kunming University of Science and Technology,ChinaProject(14118245)supported by Starting Research Fund from Kunming University of Science and Technology,China
文摘Li Fe PO4/C was prepared via solid state reaction and characterized with X-ray powder diffraction and charge–discharge test. As-prepared Li Fe PO4/C has a triphylite structure and exhibits an excellent rate capability and capacity retention. Electrochemical impedance spectroscopy(EIS) was applied to investigate LixFe PO4/C(0<x<1) electrode on temperature variation. The valid equivalent circuit for EIS fitting was determined which contains an intercalation capacitance for Li+ ion accumulation and consumption in the electrode reaction. The surface layer impedance needs to be included in the equivalent circuit when Li Fe PO4/C is deeply delithiated at a relatively high temperature. EIS examination indicates that a temperature rise leads to a better reversibility, lower charge transfer resistance, higher exchange current density J0 and greater Li+ ion diffusion coefficient for the LixFe PO4/C electrode process. The Li+ ion concentration in LixFe PO4/C is potential to impact the Li+ ion diffusion coefficient, and a decrease in the former results in an increase in the latter.
文摘CoSn alloy and Cu-Sn samples were syn thesized by H 2 -reduction following solid-state r eaction between Co ?,Cu?,Sn?and NaOH at ambient temperature.The samples were characterized by XRD,S EM.The results showed that CoSn alloy(80～200nm)is globe-shaped,ultrafine hexagon al material,and Cu-Sn alloy powder consists of two phases,i.e.Cu 6 Sn 5 and Cu 3 Sn.Cu-Sn powder has spherical morphology and the particle size is estimated to be 60～70nm.The electro chemical performances of CoSn alloy and Cu-Sn powder were studied using lithium-ions model cell Li /LiPF 6 (EC +DMC)/CoSn(or Cu-Sn).It was demonstrated the reversible discharge capacities for 10cycles keep above 280mAh ·g -1 for nanophase Cu-Sn,and 60mAh ·g -1 for CoSn alloy.Differ-ential capacity plots showed that th e reaction mechanisms of Cu-Sn with l ithium were reversible.
