High-Performance Cathode Materials for Lithium–Sulfur Batteries Based on Sulfurated Poly(norbornadiene) and Sulfurated Poly(dicyclopentadiene)

Lithium–sulfur (Li–S) batteries are among the most promising candidates for next-generation high-energy-density batteries; however, the polysulfide shuttle represents a major drawback in their application. Here, we report on sulfurized poly(norbornadiene) (S/pNBD) and its analogue, sulfurized poly(dicyclopentadiene) (S/pDCPD), two polysulfide shuttle-free and cheap cathode materials with good performance in Li–S battery technology. Both S/pNBD and S/pDCPD can be prepared in a straightforward two-step procedure. Time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy measurements, and cyclic voltammetry indicate that all sulfur in S/pNBD and S/pDCPD is covalently bound to the polymer matrix in the form of C–Sx–C units. Li–S cells based on an S/pNBD cathode exhibit a high discharge capacity up to 1050 mA h/g sulfur at 1 C with a good capacity retention of 62 % after 1900 cycles. The structurally similar analogue S/pDCPD shows comparable electrochemical performance, again with excellent capacity retention. The high reversibility and ultra-long cycle life of both, S/pNBD and S/pDCPD, are attributed to the covalent binding of sulfur to the polymer backbone.