Sulfurized polyacrylonitrile (SPAN) is a promising material for stable lithium–sulfur (Li–S) batteries that can potentially satisfy the demand for high-density energy storage devices for electric vehicles (EVs). However, important physical and chemical properties of the SPAN cathode material are not yet well understood. For example, the SPAN mechanical behavior that depends on the structure and chemistry of the material generated during synthesis and the mechanical response evolution during battery discharge have been scarcely investigated. This work addresses the effects of electrochemical lithiation on the SPAN mechanical integrity via uniaxial tensile loading tests using molecular dynamics with the ReaxFF potential. We evaluate the volume expansion, Young’s modulus, yield strength, and ultimate tensile strength with increasing lithium contents. Our results show how the degree of graphitization of the carbonized skeleton impacts the SPAN ability to withstand the volume expansion-induced structural stresses upon lithiation. We describe the fracture mechanisms and find out a ductility loss with increasing lithium contents.

中文翻译：

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硫化聚丙烯腈 (SPAN)：电化学锂化过程中机械性能的变化

硫化聚丙烯腈 (SPAN) 是一种很有前途的稳定锂硫 (Li-S) 电池材料，可以潜在地满足电动汽车 (EV) 对高密度储能设备的需求。然而，SPAN 正极材料的重要物理和化学性质尚不清楚。例如，SPAN 机械行为取决于合成过程中产生的材料的结构和化学性质以及电池放电过程中的机械响应演变。这项工作通过使用具有 ReaxFF 电位的分子动力学的单轴拉伸载荷测试解决了电化学锂化对 SPAN 机械完整性的影响。我们评估了锂含量增加时的体积膨胀、杨氏模量、屈服强度和极限拉伸强度。我们的结果显示了碳化骨架的石墨化程度如何影响 SPAN 在锂化时承受体积膨胀​​引起的结构应力的能力。我们描述了断裂机制并发现了随着锂含量增加而导致的延展性损失。