镍纤维管改善锂硫电池性能

为了改善锂硫电池的比容量和循环稳定性等电化学性能,以聚丙烯腈纤维为基体,采用无钯活化化学镀法在其表面镀一层镍,制备得到复合纤维.通过热处理去除复合纤维中的聚丙烯腈,得到氧化镍中空纤维,然后在氢等离子体气氛中对氧化镍中空纤维进行还原制备中空镍纤维管,并以它作为锂硫电池正极材料活性物质的承载体,制备含镍纤维管的硫电极来改善锂硫电池的电化学性能.采用扫描电子显微镜和X射线能谱仪表征镍纤维管的表面形貌和成分,结果表明:所制备的纤维管主要是镍,但含有少量的磷,可能是镀液中次磷酸盐中的磷元素被还原,且管径为10～15μm,管壁厚度均匀,约0.7μm.采用恒流充放电和交流阻抗谱对含镍纤维管硫电极的电化学性能进行表征,结果表明:添加镍的纤维管能够增强锂硫电池的电化学性能,在充放电电流密度为每平方厘米0.2mA的条件下,镍纤维管增强硫电极的首次放电比容量为941.6mAh/g,20次循环后的放电比容量仍保持在593.3mAh/g,表现出较高的放电比容量和良好的循环稳定性.

Lithium-sulfur battery performance improved by nickel fiber tube

To improve lithium sulfur battery electrochemical properties, such as specific capacity and cycling stability, by depositing a layer nickel on the surface of polyacrylonitrile matrix, the composite fiber was prepared using palladium-free activation electroless plating method. The polyacrylonitrile matrix was removed by thermal treatment so as to gain hollow nickel oxide fiber tube. Then, the resulting nickel oxide was reduced under hydrogen plasmas atmosphere and hollow nickel fiber tube was obtained. Sulfur electrode was prepared by adding the prepared nickel fiber tube, which was used to load the active material of lithium-sulfur battery. Surface morphology and composition of nickel fiber tube were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The results show that the obtained nickel fiber tube consists of major nickel and a small amount phosphorus. The diameter and the thickness of uniform nickel fiber tube are 10-15 μm and about 0.7 μm, respectively. Electrochemical performance of sulfur electrode, containing nickel fiber tube, was tested by constant current charge-discharge and electrochemical impedance spectroscopy. The results indicate that the fiber tube adding nickel can enhance the electrochemical performance of lithium-sulfur battery. When current density is 0. 2 mA/cm2, initial discharge specific capacity of sulfur electrode which is enhanced by nickel fiber tube, is 941.6 mAh/g and the discharge capacity remains 593.3 mAh/g after 20 cycles, and the cell exhibits high discharge specific capacity and good cycle stability.