| Olivine structure fayalite （Fe2SiO4） is a kind of large development potential anode material, which is abunant and low cost. Ferrous lithium silicate （Li2FeSiO4） with olivine structure is a cathode material for lithium ion battery. Li2FeSiO4 has a high theoretical specific capacity of 333 mAh/g, low cost and stable structure. Li2FeSiO4 has attracted much attentions in recent years. Fe2-xAlxSiO4@C （x=0,0.02,0.06） anode material, Fe2±SiO4@C （x=0,0.2,0.4） anode material and Li2FeSiO4@C cathode material were successfully fabricated by a solid state reaction. The structure, morphology and electrochemical properties of theses materials were mainly researched.Three kinds of carbon anode materials were prepared from three different kinds of organic carbon sources （cane sugar, citric acid and ammonium citrate） by high temperature solid-state method,respectively. The electrochemical properties of three kinds of carbon anode materials were studied. The results show that carbon anode materials prepared by ammonium citrate has excellent electrochemical performance. Therefore, we choose ammonium citrate （（NH4）3C6H5O7） as carbon coating source. Fe2-xAlxSiO4@C （x=0,0.02,0.06） anode materials were synthesized from the main raw materials of SiO2 （30±5 nm）, FeC2O42H2O, Al2O3 and （NH4）3C6HsO7 by solid-state method. Effect of amount of Al-doping on the electrochemical properties of Fe2-xAlxSiO4@C as anode materials were mainly studied. The results show that Fe2SiO4@C without Al-doping as anode materials have higher capacity retention, good rate performance, excellent cycle stability, minimum charge transfer resistance and Warburg resistance （Zw）. With the increase of Al-doping content （the value of x becomes large）, the retention capacity and specific capacity of Fe2-xAlxSiO4@C anode materials gradually reduce, and the charge transfer resistance and Warburg resistance （Zw） of Fe2-xAlxSiO4@C increase gradually.Fe2±SiO4@C （x=0,0.2,0.4） were fabricated by a high temperature solid-state method. The structural, morphology and the electrochemical properties of Fe2+xSiO4@C were studied from two aspects of low content of iron and high content of iron. The research results indicate that the content of Fe has a great influence on the electrochemical performance of Fe2±xSiO4@C anode materials. XRD analysis shows that the XRD patterns of Fe2.2SiO4@C and Fe2.4SiO4@C appear a weak Fe impurity peak, respectively. No obvious Fe impurity of Fe2-xSiO4@C （x=0,0.2,0.4） is observed in XRD patters. SEM analysis demonstrates that particles size of Fe1.6SiO4@C samples is the maximum, while particles size of Fe2SiO4@C samples with uniform distribution is the minimum. Electrochemical tests manifest that Fe2SiO4@C samples has excellent cycle performance. And the charge transfer resistance and Warburg resistance of Fe2SiO4@C are minimum at the same time.Li2FeSiO4@C cathode materias were synthesized from two differernt kinds of iron sources （FeC2O4·2H2O and C6H5O7Fe·5H2O） by a facile solid-state reaction method for lithium ion battery, repectively. Effect of the iron source on structure and performance of Li2FeSiO4@C was studied. The results show that there are obvious impacts on the structure and properties of Li2FeSiO4@C anode materials when iron source changing. XRD analysis results indicate that LFS-1 has high crystallinity. LFS-1 and LFS-2 both show some Fe3O4 impurity. LFS-2 has higher content of Fe3O4 impurity peak. SEM analysis demonstrates that nanoparticles size of LFS-2 samples is smaller than that of LFS-1. Electrochemical tests manifest that LFS-2 shows excellent electrochemical performance. |
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