FeSe_(2)-C三维导电复合材料的制备及其电化学性能

Preparation and electrochemical properties of FeSe_(2)-C three-dimensional conductive composites

过渡金属硒化物因为具有更窄的带隙和线宽、更高的导电性、更大的层间距、更低的成本以及更高的理论容量等优势,在电极材料领域受到了广泛关注。本研究为着重解决FeSe_(2)电极材料可逆容量低和循环稳定性差等问题,设计了在FeSe_(2)阳极中掺杂膨胀石墨,形成由互相穿插、堆叠的膨胀石墨片组成的三维导电网络结构,以膨胀石墨为碳源,采用简单有效的溶剂热法制备出FeSe_(2)-C负极材料。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、N2吸附法等表征手段,对样品的晶体结构组成、微观结构形貌进行了解析。同时,采用了恒流充放电(GCPL)、循环伏安(CV)以及交流阻抗(EIS)等电化学测试方法,研究了膨胀石墨的掺杂对FeSe_(2)电化学性能的影响。结果表明,FeSe_(2)-C电极呈现出层级结构且储锂能力良好,具有优异的电化学性能和循环稳定性。在0.1 A/g的电流密度下首次放电比容量高达720.5 mAh/g,充电比容量512.3 mAh/g、首次库仑效率71.1%。在5 A/g的电流密度下经过1000次循环后容量仍有339.1 mAh/g,是纯FeSe_(2)电极材料经历相同次数循环后的8.5倍。利用膨胀石墨构筑三维导电网络的技术方法,可以有效改善FeSe_(2)的电化学性能。

Transition metal selenides have drawn extensive attention as electrode materials because of their narrower bandgap and linewidth,higher conductivity,larger interlayer spacing,lower cost,and better theoretical capacity.In this study,the FeSe_(2) anode was designed to be doped with expanded graphite to form a three-dimensional conductive network structure composed of interpenetrated and stacked,expanded graphite sheets to address the issues of low-reversible capacity and poor cycle stability of FeSe_(2) electrode materials.FeSe_(2)-C anode material was prepared using a simple and effective solvothermal technique.The crystal structure composition and microstructure morphology of the samples were evaluated using an X-ray diffractometer,scanning electron microscope,transmission electron microscope,N2 isotherm adsorption,and other characterization methods.Meanwhile,electrochemical test techniques,including galvanostatic cycling with potential limitation,cyclic voltammetry,and alternating current impedance were used to study the impact of expanded graphite doping on the electrochemical properties of FeSe_(2).The results demonstrate the hierarchical structure,outstanding lithium storage capacity,high electrochemical performance,and cycling stability of the FeSe_(2)-C electrode.The first coulombic efficiency is 71.1%at a current density of 0.1 A/g,while the first discharge-specific capacity can reach 720.5 mAh/g,and the charge-specific capacity can reach 512.3 mAh/g.After 1000 cycles at a current density of 5 A/g,the capacity was still 339.1 mAh/g,which is 8.5 times that of the pure FeSe_(2) electrode material after the same number of cycles.Expanded graphite construction into a three-dimensional conductive network is a practical way to enhance FeSe_(2)'s electrochemical performance.