氮掺杂多孔碳纤维改性锂硫电池正极材料

锂硫电池具有高比能量密度,在航空航天、无人机等电源系统应用方面受到了广泛关注。但是其本身也存在一些问题,如电池正极材料反应前后体积膨胀、导电性差和容量衰减迅速等,这些均限制了其应用推广。本文通过引入氮掺杂多孔碳纤维作为硫正极材料载体来改善其性能。一方面,碳纤维能提供大的反应比表面积和相互交织的导电网络,有效促进了活性材料之间的电化学反应;另一方面,氮原子掺杂和表面孔的存在,增强了对反应中间产物多硫化锂的吸附性,使得电极循环稳定性得到提高。研究结果表明:改性后含硫正极在167.5 mA·g~(-1)电流密度下,初始放电比容量达到1 078.3 mAh·g~(-1),经过100周充放电循环后,容量可保持在525.4 mAh·g~(-1),平均每周容量衰减率为0.5%;当电流密度增大到1 675 mA·g~(-1)时,放电比容量仍可以达到502.3 mAh·g~(-1),表现了良好的循环稳定性和倍率性能。

Modification of Li-Sulfur Battery Cathode Material by Nitrogen-Doped Porous Carbon Nanofibers

Li-sulfur batteries have high specific energy density, and have received extensive attention in power system application such as aerospace and unmanned aerial vehicle. However, there are some obstacles, e.g., Li-sulfur battery cathode materials have poor conductivity and rapid capacity decay and their volumes will expand before and after reactions. All these limit their application and promotion. In this work, nitrogen-doped porous carbon nanofibers are introduced to improve the properties of Li-sulfur battery cathode materials. Carbon nanofibers provide a large specific surface area for the reactions and an intertwined conductive network, which effectively promote the electrochemical reactions among the active materials. Besides, the presence of nitrogen atoms and surface pores enhances the absorbability of the reaction intermediates, i.e., lithium polysulfides, resulting in the improvement of the electrode cycle stability. The study results show that the initial discharge specific capacity of the modified sulfur-containing cathode electrode reaches 1 078.3 mAh.g-1 at the current density of 167.5 mA.g-1. After 100 cycles of charging and discharging, the capacity can be maintained at 525.4 mAh.g-1, and the average capacity decay rate is 0.5% per cycle. When the current density is increased to 1 675 mA.g-1, the discharge specific capacity can still reaches 502.3 mAh.g-1, indicating good cycle stability and rate performance.