Lithium salts based on perfluorinated sulfonimide anions (PSAs) are promising new electrolyte components for application in next-generation lithium batteries. Several typical symmetric ([(n-C_mF_2m+1SO₂)₂N]⁻, m = 0, 1, 2, 3, and 4) and asymmetric ([(FSO₂) (n-C_mF_2m+1SO₂)N], m = 1, 2, 4, 6, and 8) PSAs have been extensively investigated in recent years. Yet little is known about the role of asymmetry in the physicochemical and electrochemical properties at the molecular level. Here we use first-principle density functional theory calculations to thoroughly examine such fundamental structure-activity relationship. Compared to symmetric PSAs, asymmetric isomers show intrinsically better internal flexibility of the S─N bond, lower dissociation energy of Li⁺ cation, and thereby they can be promising candidates for polymer electrolytes. We also observe that more than four C atoms in the perfluorinated chain results in negligible improvements in terms of dissociation energy, thermal stability, and anodic stability. These results provide an in-depth understanding of the impact of the molecular structure on PSAs, helping design new robust anions for lithium batteries in the future.

基于全氟化磺酰亚胺阴离子（PSA）的锂盐是有前途的新型电解质成分，可用于下一代锂电池。几种典型的对称（[（n -C _m F _{2 m +1} SO ₂）₂ N] ^-，m  = 0、1、2、3和4）和非对称（[[FSO ₂）（n -C _m F _{2 m +1} SO ₂）N]，m = 1、2、4、6和8）近年来，对PSA进行了广泛的研究。关于不对称在分子水平上的物理化学和电化学性质中的作用还知之甚少。在这里，我们使用第一原理密度泛函理论计算来彻底检查这种基本的结构-活性关系。与对称PSA相比，不对称异构体在本质上显示出S-N键的内部柔性更好，Li ^+的解离能更低阳离子，因此它们可以成为高分子电解质的有希望的候选者。我们还观察到，全氟化链中的四个以上的C原子在离解能，热稳定性和阳极稳定性方面的改善可忽略不计。这些结果提供了对分子结构对PSA的影响的深入了解，有助于将来为锂电池设计新的坚固的阴离子。