LiFeSO4F/石墨烯复合材料的制备与电化学性能

分别以FeSO4.H2O、FeSO4.4H2O和FeSO4.7H2O为原料与LiF在四甘醇介质中反应制得LiFeSO4F,用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)表征LiFeSO4F的结构和形貌.热重分析表明LiFeSO4F在400℃开始分解.XRD结果表明,以FeSO4.4H2O和FeSO4.7H2O为原料,多个结晶水的存在可以延缓原料的脱水过程,有利于消除产物中FeSO4杂相的生成.利用循环伏安(CV)、电化学交流阻抗(EIS)和充放电实验测试材料的电化学性能,发现加入石墨烯后可以促进LiFeSO4F的电化学活性,提高材料的比容量、倍率性能和循环性能.

Synthesis and Electrochemical Properties of LiFeSO4 F/Graphene Composite as Cathode Material for Lithium-Ion Batteries

LiFeSO4F was successfully synthesized from the reaction of FeSO4·xH2O(x=1,4,7) with LiF in tetraethylene glycol media through a facile low temperature method.The structures and microscopic features of the products were characterized by XRD,SEM and TEM.TGA result shows good thermal stability of the as-prepared LiFeSO4F.No diffraction peaks of FeSO4 are observed in the as-prepared products with the starting material of either FeSO4·4H2O or FeSO4·7H2O,which should be ascribed to delaying the release of H2O from the hydrated compounds.Cyclic voltammetry curves and electrochemical impedance spectroscopy results prove that the LiFeSO4F/graphene composite exhibits less electrochemical polarization and smaller impedance than those of pure LiFeSO4F,in which the graphene serves as the electronic conductivity support to enhance the lithium storage properties.The LiFeSO4F/graphene composite shows a high specific capacity,good rate capability and cycling stability compared with the pure LiFeSO4F.