NiS_(2)/多孔碳纤维复合电极的制备及其储锂性能

Preparation and lithium storage property of NiS_(2)/porous carbon nanofiber composite electrode

制备长循环稳定、高容量的负极材料是锂离子电池实现大规模储能应用的前提之一。利用静电纺丝技术和水热硫化的方法制备了均匀分布的NiS_(2)/碳纳米纤维(NiS_(2)/C)复合材料。作为锂离子电池负极材料,NiS_(2)/C电极的首次放电比容量为864.6 mAh/g,首次库仑效率为62.7%。其中不可逆容量为322.9 mAh/g,不可逆容量主要由转换反应的部分不可逆及固态电解质(SEI)膜的形成造成的。NiS_(2)/C复合电极表现出优异的循环稳定性,200 mA/g下150次循环后容量仍然维持在519 mAh/g,容量保持率高达90.4%。此外,在2 A/g大电流密度下,NiS_(2)/C电极的容量仍高于310 mAh/g表现出出色的倍率性能。借助XRD、SEM及TEM表征,分析发现包裹着NiS_(2)纳米颗粒的碳纤维,作为良好的导电介质,既可以提高NiS_(2)的导电性,也可缓解NiS_(2)脱嵌过程中的体积膨胀,使得NiS_(2)/C电极仍能保持自身的空间结构,有助于提高电池循环性能;另一方面,碳纤维的多孔结构为锂离子提供了通道,缩短了锂离子的传输路径,提高了锂离子输运速率,有利于电池倍率性能。

The preparation of long-cycle stable anode materials with high specific capacity is a prerequisite for large-scale lithium-ion battery energy storage applications.NiS_(2)/carbon nanofiber(NiS_(2)/C) composites with uniform distribution were prepared by electrospinning and hydrothermal vulcanization.As anodes for lithium-ion batteries,the first discharge capacity of NiS_(2)/C electrode is 864.6 mAh/g and the first Coulomb efficiency is 62.7%.The irreversible capacity is 322.9 mAh/g,which is mainly caused by the partial irreversible reaction and the formation of solid electrolyte interlayer(SEI) membrane.The NiS_(2)/C electrode shows excellent cyclic stability,delivering a reversible capacity of 519 mAh/g after 150 cycles at 200 mA/g with a capacity retention rate as high as 90.4%.In addition,the capacity of NiS_(2)/C electrode is still higher than 310 mAh/g at high current density of 2 A/g,which also displays superior rate performance.By XRD,SEM and TEM,it is found that the carbon nanofiber in NiS_(2)/C,serving as the carrier and conductive medium,can greatly increase the conductivity of electrodes and efficiently accommodate the volume changes,so that NiS_(2)/C electrode can keep its spatial structure and attributes to improve cycle performance.In addition,the porous structure of carbon nanofiber can provide channels for lithium ions,reduce the Li~+ diffusion distance and enhance the ion transport rate,which is beneficial to the rate performance of batteries.