Hybrid Sulfur−Selenium Co‐polymers as Cathodic Materials for Lithium Batteries

Abstract Lithium−sulfur is being explored as a promising battery technology, owing to due to advantages compared to the actual Li ion. However, sulfur cathode materials have critical drawbacks that limit their battery performance. Recently, the atomic combination of sulfur with selenium has shown a synergetic effect in terms of capacity and rate capability; nevertheless, a high‐energy and non‐scalable method was used to prepare the sulfur−selenium cathodes. In this work, the synthesis of sulfur−selenium hybrid co‐polymers is reported by using a low‐energy and scalable inverse vulcanization method. Thus, a series of chalcogenide hybrid inorganic/organic materials were synthesized by varying the sulfur, selenium, and organic content. The chalcogenide part was characterized by using Raman spectroscopy and 77 Se NMR, showing a random distribution of selenium within the sulfur segments. The organic part and the hybrid were further characterized by using 1 H NMR, DSC, and TGA approaches, confirming the typical structure of inverse vulcanized co‐polymers. These hybrids were easily processed by conventional cathode fabrication methods and electrochemically characterized. The presence of selenium slightly affected the cyclic voltammetry of the materials, maintaining the typical features to be used as cathodes in lithium−sulfur batteries. Interestingly, the sulfur−selenium cathodes showed an enhanced C‐rate capability and high cycling stability. The optimum co‐polymer composition was 5 to 7.5 mol % of Se within S and 10 wt % of organic co‐monomer, showing initial capacity values of 860 and 880 mAh g −1 , respectively, for a moderate C‐rate of C/5. These polymers showed the lowest capacity loss per cycle, 0.14 and 0.4 %, in comparison with the 0.6 % of capacity loss of the polymer with bare sulfur. Interestingly, for a lithium−sulfur cell, the best performing material shows an excellent capacity value of 550 mAh g −1 at high C rate of 1C.