The nominal Li_(3-x)Fe_(2-x)Ti_x(PO_4)_(2.55)(VO_4)_(0.45)(x=0～0.3) compounds were synthesized by a sol-gel process.Different from the single V043 doping, further introduction of Ti^(4+) ion was easy to result in pre...The nominal Li_(3-x)Fe_(2-x)Ti_x(PO_4)_(2.55)(VO_4)_(0.45)(x=0～0.3) compounds were synthesized by a sol-gel process.Different from the single V043 doping, further introduction of Ti^(4+) ion was easy to result in precipitation of a little secondary phases, besides the main NASICON products. The simultaneous substitution of Ti^(4+)and VO_4~3 for Fe^(3+) and PO_4~3,respectively, in the Li_3 Fe_2(PO_4)_3 resulted in a net improvement in the rate capability and cycling performance, as compared with the single Ti^(4+) or VO_4~3-substituted compound.The sample with x=0.2 presented a high initial discharging capacity of 125.4 mAh/g at the rate of 0.5 C,about 25% higher than the Ti^(4+)-substituted Li_(2.8)Fe_(1.8)Ti_(0.2)(PO_4)_3, and 102.6 mAh/g after 60 cycles at 2 C,about 12% higher than the single VO_4~3-substituted one. The high rate performance between 0.5 C to 10 C suggested that this sample had a good stability and reversibility. These results proved that the combination of the Ti^(4+) substitution for Fe^(3+) with the V043 substitution for PO_4~3 was a promising method of improving electrochemical performance of the studied Li_3 Fe_2(PO_4)_3 cathode material.展开更多
Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5...Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.展开更多
Synthesis of complexes（η;-CH;C;H;）M（CO）;NO（M=Mo,I;M=W,II）and clusters（η;-CH;C;H;）M（μ;-NH）(μ;-NO) （μ;-CO）Fe;（CO）;（M=Mo,III:M=W,IV）,based on the reaction of （η;-C5;）M（CO）;Cl with Na[Fe（CO）;NO...Synthesis of complexes（η;-CH;C;H;）M（CO）;NO（M=Mo,I;M=W,II）and clusters（η;-CH;C;H;）M（μ;-NH）(μ;-NO) （μ;-CO）Fe;（CO）;（M=Mo,III:M=W,IV）,based on the reaction of （η;-C5;）M（CO）;Cl with Na[Fe（CO）;NO] at room tem-perature,have been demonstrated,The crystal structures of II and IV arealso presented.展开更多
基金supported by Natural Science Foundation of Hebei Province (No. E2016202358)
文摘The nominal Li_(3-x)Fe_(2-x)Ti_x(PO_4)_(2.55)(VO_4)_(0.45)(x=0～0.3) compounds were synthesized by a sol-gel process.Different from the single V043 doping, further introduction of Ti^(4+) ion was easy to result in precipitation of a little secondary phases, besides the main NASICON products. The simultaneous substitution of Ti^(4+)and VO_4~3 for Fe^(3+) and PO_4~3,respectively, in the Li_3 Fe_2(PO_4)_3 resulted in a net improvement in the rate capability and cycling performance, as compared with the single Ti^(4+) or VO_4~3-substituted compound.The sample with x=0.2 presented a high initial discharging capacity of 125.4 mAh/g at the rate of 0.5 C,about 25% higher than the Ti^(4+)-substituted Li_(2.8)Fe_(1.8)Ti_(0.2)(PO_4)_3, and 102.6 mAh/g after 60 cycles at 2 C,about 12% higher than the single VO_4~3-substituted one. The high rate performance between 0.5 C to 10 C suggested that this sample had a good stability and reversibility. These results proved that the combination of the Ti^(4+) substitution for Fe^(3+) with the V043 substitution for PO_4~3 was a promising method of improving electrochemical performance of the studied Li_3 Fe_2(PO_4)_3 cathode material.
基金Projects(13A047,10B054)supported by the Scientific Research Fund of Hunan Provincial Education Department,ChinaProjects(2011GK2002,2011FJ3160)supported by the Planned Science and Technology Project of Hunan Province,China
文摘Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.
文摘Synthesis of complexes（η;-CH;C;H;）M（CO）;NO（M=Mo,I;M=W,II）and clusters（η;-CH;C;H;）M（μ;-NH）(μ;-NO) （μ;-CO）Fe;（CO）;（M=Mo,III:M=W,IV）,based on the reaction of （η;-C5;）M（CO）;Cl with Na[Fe（CO）;NO] at room tem-perature,have been demonstrated,The crystal structures of II and IV arealso presented.
