A universal strategy for the refined frameworks and improved performance of distinct commercial polyacrylonitriles in sulfur cathodes

Sulfurized polyacrylonitrile (SPAN) with the exceptional stability, safety, low cost, and high capacity have been positioned as a highly promising cathode material for next-generation lithium-ion batteries. However, in the market, polyacrylonitrile (PAN) sourced from different suppliers and available at varying prices exhibits significant variations in physical and chemical properties, resulting in diverse behaviors in Li-SPAN batteries. By studying the mechanism, we found that the PAN copolymerization structure leads to the stacking of chain segments which obstructs the embedding of sulfur and lithium ions. Here, we propose a universal strategy for the refined frameworks by an exogenous additive to modify various PAN raw materials, and the battery capacity and cycling performance are obviously improved. As a result, the copolymerized SPAN with a poor original capacity is nearly doubled to over 500 mAh g⁻¹, almost comparable to high-quality yet expensively imported products; for the sample with a high initial capacity but fading in ether-based electrolytes, it can be modified to maintain stability over 400 cycles. This strategy offers an alternative approach for SPAN modification that is characterized by its simplicity and low cost, thereby facilitating the large-scale development of Li-SPAN batteries.