Sulfurized polyacrylonitrile (SPAN) is regarded to be one of the most promising cathode materials for lithium–sulfur (Li–S) batteries because of its unique chemical structure and high cyclic ability. However, the physicochemical properties of SPAN correlate with the synthesis and process conditions. In this work, flexible and freestanding SPAN nanofiber cathodes are prepared via the electrospinning technique followed by a sulfurization process. And the effect of synthesis temperatures on microstructure and electrochemical performance of SPAN are systematically investigated. According to the spectroscopic analysis, short –S_x– (2 ≤ x ≤ 3) chains are covalently bonded to the cyclized and dehydrogenated PAN backbones through C–S bonds during the synthesis temperature between 300 and 600 °C. Among which, the SPAN nanofiber prepared at 500 °C shows not only a low charge transfer resistance but also the best cell performance. Upon 200 cycles, it displays a high reversible capacity of 1280 mAh g^–1 with a fading rate as low as 0.02% per cycle at 400 mA g^–1. Highly stable long-term cycling at higher current densities and good rate capability are also achieved. The work provides significant guidance for the development of advanced SPAN cathode materials.

硫化聚丙烯腈（SPAN）由于其独特的化学结构和高循环能力，被认为是锂-硫（Li-S）电池最有希望的正极材料之一。但是，SPAN的物理化学性质与合成和工艺条件相关。在这项工作中，通过电纺丝技术和随后的硫化工艺制备了柔性且独立的SPAN纳米纤维阴极。并系统地研究了合成温度对SPAN的微观结构和电化学性能的影响。根据光谱分析，短–S _x–在300至600°C的合成温度下，（2≤x≤3）链通过C–S键与环化和脱氢的PAN主链共价键合。其中，在500°C下制备的SPAN纳米纤维不仅显示出低的电荷转移阻力，而且还具有最佳的电池性能。经过200次循环后，它显示出1280 mAh g ^–1的高可逆容量，而在400 mA g ^–1时的衰落率则低至每个循环0.02％。还可以在较高的电流密度下实现高度稳定的长期循环，并具有良好的倍率能力。这项工作为高级SPAN阴极材料的开发提供了重要指导。