| In this paper,Three kinds of transition metal compounds?MoS2,VS4 and Ca3Co4O9?were synthesized as anode materials for lithium-ion batteries.Based on above materials,the synthesis,crystal structure,electrochemical properties and related mechanism have been studied.What is more,the influence of different dopants on the electrochemical properties of Ca3Co4O9 anode materials and electrochemical performances of MoS2/C composites were discussed in this paper.The main valuable conclusions are listed as follows:?1?The Ca3Co4O9 was synthesized through reheological phase reaction method using Ca(C6H12O6)2,C6H8O7 and CoAc2·4H2O as raw materials and alcohol as solvent.The GeO2and Bi?NO3?3·5 H2O were added separately raw materials to get different expected compounds doped Ge,Bi or both of them.The precursors were formed at 120?for 12 hours.After milling,precursors were calcined at different temperatures to obtain Ca3Co4O9 samples.By doping Ge,Bi or both of them,some vacancy defects may be created in the crystal lattice of Ca3Co4O9,which can improve the electrochemical performances of Ca3Co4O9.The crystal structure and morphology for Ca3Co4O9 were characterized by X ray powder diffraction?XRD?and scanning electron microscopy?SEM?techniques.The electrochemical performances of Ca3Co4O9 were tested by using the constant current charge/discharge system and the electrochemical workstation.The results showed that the expected compounds with irregular porous structure are formed and its electrochemical performances were depended on calcination temperature and different doping of Ge or Bi elements.Whe calcined temperature was controlled at 750?,sample doped by both of Ge and Bi elements(that is Ca2.85Ge0.15Co3.85Bi0.15O9)has higher reversible capacity,when current density is 100 mA·g-1in of 0.01-3.0V voltage window,its reversible capacity could maintain at 550 mA·g-1 after100 cycles.At the same time,the formation mechanism and electrochemical reaction process for Ca3Co4O9 were discussed in our work.?2?The ammonium molybdate and PAN?Polyacrylonitrile?were used as raw materials,and DMF?HCON?CH3?2?as solvent,the collector is a nickel foam.The precursors were obtained by electrospinning method.The MoS2/C composites were formed by calcination of the precursor at 500?for 4 h under an argon atmosphere.The expected compounds were characterized by X-ray powder diffraction?XRD?,scanning electron microscopy?SEM?,thermal weight analysis?TG?and Raman?Raman?spectra techniques.Exprimental results showed that expected compound?MoS2/C?was formed.It takes morphology of nanofibers and diameter of the MoS2/C nanofibers were ranged from 50 to 150 nm.Electrochemical tests showed that the reversible discharge capacity of MoS2/C nanofibers is high(650 mA·g-1).And the rate performance of MoS2/C nanofibers is also excellent,when the discharge current desity is 1000 mA·g-1,discharge capacity is 293 mA·g-1.When current density is back to 100mA/g,discharge capacity returned back to 636 mA·g-1.Compared with the pure MoS2material,its charging/discharging platform is lower?It is about 1.2V which is lower than2.0V reported in other articles?.The electrochemical process of MoS2/C is presented also.So MoS2/C synthesized by electrospinning method is a promising anode material for lithium ion battery application.?3?Ammonium vanadium?NH4VO3?and Amide amide?CH3CSNH2?were used as raw materials,the compound?VS4?was synthesized by hydrothermal method at different temperatures.The expected compounds were characterized by X ray powder diffraction?XRD?and scanning electron microscopy?SEM?techniques.The electrochemical properties of VS4samples prepared at different temperatures were tested also.The electrochemical properties and diffusion coefficient of lithium ions in VS4 electrode materials are discussed.The results showed that the VS4 sample synthesized at 160?behaved the best electrochemical properties?such as high reversible capacity,better cycle stability,and larger lithium ion diffusion coefficient?among all samples synthesized at other temperatures.VS4 synthesized by hydrothermal method at 160?in all samples could be a promising anode material for lithium ion batteries. |
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