Inverse Vulcanization of Sulfur using Natural Dienes as Sustainable Materials for Lithium–Sulfur Batteries

Abstract

Lithium-sulfur batteries are among the most promising next-generation battery systems due to the high capacity of sulfur as cathodic material. Beyond its interesting intrinsic properties, sulfur possesses a very low conductivity and complex electrochemistry, which involves the high solubility of the lithium sulfides in the electrolyte. These two characteristics are at the core of a series of limitations of its performance as active cathode material, which leads to batteries with low cyclability. Recently, inverse vulcanized sulfur was shown to retain capacity far better than elemental sulfur, leading to batteries with excellent cyclability. Nevertheless, the diene co-monomers used so far in the inverse vulcanization process are man-made molecules. Herein, a tentative work on exploring inverse vulcanization using two naturally available monomers, diallyl sulfide and myrcene, is presented. The inverse vulcanization of sulfur was successfully completed, and the resulting polymers were characterized by FTIR, NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Afterwards these polymers were tested as cathodic materials in lithium-sulfur cells. The sulfur-natural dienes materials exhibited high capacity at different C rates and high lifetime over 200 cycles with very high capacity retention at a moderate C rate of C/5. Altogether, these materials made from inexpensive and abundant chemicals are an excellent option as sustainable materials for electrochemical energy storage.

Sustainable inverse-vulcanised sulfur polymers

“…À10 C), 22 diallyl disulde (À14 C to 4 C) 15,28 and myrcene (5-10 C). 15 When compared to these reported inversevulcanised polymers synthesised directly from renewable crosslinkers, both squalene and perillyl alcohol have comparatively high glass transition temperatures, at 21 and 20 C respectively, for 50 wt% sulfur compositions ( Fig. 4a and b).…”

“…Recently there has been a surge of further reports of other inverse vulcanised polymers using a variety of crosslinkers. 4,[14][15][16][17][18][19] Although these new materials have made progress in improving the applications of sulfur materials, there are still issues to be addressed, such as molecular weight 14,15 and cost. The cost can be attributed to either the crosslinker used 19 or requiring multistep synthesis, 17,18 when compared to simpler one-pot syntheses reported for commercially available crosslinkers.…”

“…15 Limonene is a by-product of the citrus industry, which isolates in excess of 70 000 tonnes per year from the zest of oranges, 23 making it ideal to combine with waste sulfur. However, susceptibility to re-arrangement and hydrogen loss during the synthesis limits the molecular weight, and reduces the shapepersistency of the material.…”

Sulfur Radical Transfer and Coupling Reaction to Benzoxazine Groups: A New Reaction Route for Preparation of Polymeric Materials Using Elemental Sulfur as a Feedstock

“…In 2013, Pyun and co‐workers demonstrated an innovative process named “inverse vulcanization” involving reactions between elemental sulfur and divinylic species for the preparation of processable polymeric materials possessing high sulfur contents . As inverse vulcanization usually occurs via radical addition to unsaturated CC bonds, glyceride‐based vegetable oil and plant oils, both possessing unsaturated units in the alkyl tails, are especially suitable for this process to prepare corresponding functional materials exhibiting sustainable and nonhazardous characteristics . Moreover, inverse vulcanization has also been applied to preparation of sulfur‐containing polymers possessing various functional units including polyhedral oligomeric silsesquioxane, benzoxazine, oleylamine, and triisopropenylbenzene .…”

“…In this work, we demonstrate a new reaction of sulfur for the synthesis of sulfur‐containing polymeric materials. Rather than the radical addition reaction to vinyl groups, a recent study reports that chain transfer reactions of sulfur radicals also involve in the inverse vulcanization process . The newly generated radicals with the chain transfer reactions might react with sulfur radicals through radical coupling reactions.…”