New Insights into the N–S Bond Formation of a Sulfurized-Polyacrylonitrile Cathode Material for Lithium–Sulfur Batteries

Abstract

Sulfurized polyacrylonitrile (S-cPAN) has been recognized as a particularly promising cathode material for lithium–sulfur (Li–S) batteries due to its ultra-stable cycling performance and high degree of sulfur utilization. Though the synthetic conditions and routes for modification of S-cPAN have been extensively studied, details of the molecular structure of S-cPAN remain yet unclear. Herein, a more reasonable molecular structure consisting of pyridinic/pyrrolic nitrogen (NPD/NPL) is proposed, based on the analysis of combined X-ray photoelectron spectroscopy, 13C/15N solid-state nuclear magnetic resonance, and density functional theory data. The coexistence of vicinal NPD/NPL entities plays a vital role in attracting S2 molecules and facilitating N–S bond formation apart from the generally accepted C–S bond in S-cPAN, which could explain the extraordinary electrochemical features of S-cPAN among various nitrogen-containing sulfurized polymers. This study provides new insights and a better understanding of structural details and relevant bond formation mechanisms in S-cPAN, providing a foundation for the design of new types of sulfurized cathode materials suitable for application in next-generation high-performance Li–S batteries.

Polymer Electrode Materials for Lithium‐Ion Batteries

“…[179] In addition, sulfurized poly acrylonitrile (SPAN) is one of the most successful examples of side-chain type DSPs. [181][182][183] SPAN has a single discharge platform, high CE, and high reversible capacity (≈1651 mAh g −1 ). [182,184] The possible reasons for the excellent electrochemical performance were discussed.…”

“…[181][182][183] SPAN has a single discharge platform, high CE, and high reversible capacity (≈1651 mAh g −1 ). [182,184] The possible reasons for the excellent electrochemical performance were discussed. As shown in Figure 18a, the thiyl radicals can transform to thiolate anions by the electron delocalization along the pyridine backbone.…”

Polymers in Lithium–Sulfur Batteries

“…Recently, Huang et al. [ 89,90 ] proposed another probable molecular structure of S‐cPAN with the coexistence of pyridinic and pyrrolic nitrogen (NPD and NPL) (Figure 5c). They first unraveled the presence of a significant amount of NPL in S‐cPAN, which is different from the predominant NPD in most previous reports.…”

“…c) Structure diagrams of cPAN with different nitrogen configurations and the proposed molecular of S-cPAN. Reproduced with permission [89]. Copyright 2021, American Chemical Society.…”

Three-Dimensional Engineering of Sulfur/MnO2 Composites for High-Rate Lithium–Sulfur Batteries

“…Up to now, numerous host materials have been proposed including carbon, − polymer, − metal single atoms, − metal oxides, − metal sulfides, , metal nitrides, , metal carbide − and others. Especially, efficient conversion and proper anchoring of LPSs have been demonstrated to be effective strategies to facilitate the usage of sulfur and ensure good capacity retention of LSBs.…”