微乳液静电纺丝制备多孔Nb4N5纤维及其电化学性能

Preparation and Electrochemical Properties of Porous Nb4N5 Fibers via Microemulsion Electrospinning

以五氯化铌为原料,液体石蜡为分相剂,采用微乳液静电纺丝技术制备前驱体纤维,再经氨气还原氮化得到多孔氮化铌纤维。利用XRD、SEM、BET等进行物相及微观结构表征,结果表明合成的纤维为四方Nb4N5晶相,纤维连续,直径为260 nm,由于液体石蜡分相以及助纺剂PVP的分解作用,在纤维上形成较多孔道结构,其BET比表面积为125 m^2/g,孔径为2~5 nm范围内的孔结构比例较高,同时在5~10 nm范围也存在较多的孔道结构,平均孔径为7.3 nm。采用CV、GCD及EIS等测试其电化学性能发现,氮化铌纤维的储能主要受电极表面电荷传递过程控制的,外表面比电容贡献高,这得益于分布在纤维中的孔结构,其可为离子传输提供通道,并为电化学反应提供空间。当电流密度为5 mA/g时,比电容为151 F/g,能量密度为7.73 Wh/kg时,功率密度为3.03 W/kg,其经2000次循环后其比电容保持在95%以上。

Precursor fibers were prepared by microemulsion electrospinning method using NbCl5 as raw material and liquid paraffin as phase separation agent.The porous niobium nitride fibers were synthesized via nitrogen reduction of the Nb2O5 precursor fibers in NH3.The phase and were characterized by XRD,SEM,BET.The results show that the synthesized porous niobium nitride fibers were cubic Nb4N5 phase.The fiber had continuity morphology,and the fiber diameter was about 260 nm.Due to the phase separation of liquid paraffin and the decomposition of PVP,the porous structure was distributed in the Nb 4N 5 fibers.The BET specific surface area of the fibers was 125 m^2/g and the pore structure in the range of 2-5 nm of fibers has a high proportion,and there are also many pore structures in the range of 5-10 nm,the average pore size was 7.3 nm.The electrochemical properties were tested by CV,GCD and EIS.The results show that the energy storage of niobium nitride is mainly controlled by the charge transfer process on the electrode surface,and the pore structure distributed in the fiber could provide a channel for ion transmission and space for electrochemical reaction.The specific capacitance of porous niobium nitride fibers was 151 F/g as the current density was 5 mA/g.When the power density was 3.03 W/kg,the energy density was 7.73 Wh/kg.The specific capacity remained 95%after the charge and discharge cycle of 2000 times.