Investigation of poly(3,6-dioxa-1,8-octane-dithiol)-based organosulfur polymer as the positive electrode material in rechargeable Li-S battery

Abstract

The lithium-sulfur batteries (LISB) possess issues, such as insulating nature of sulfur, polysulfide shuttle, volume expansion and self-discharge, which impede its widespread commercialization. To address the insulating nature of sulfur, carbon-based materials were utilised. However, increasing the amount of carbon content in the cathode matrix reduces the specific capacity and the gravimetric energy density. To address the above-mentioned issues, we believe that these can be overcome by developing or utilising sulfur confining materials, favourably macromolecules, so-called organosulfur polymers, as suitable candidates and potential solution. Hence, we developed a sulfur rich organosulfur based polymer, sulfur-poly(3,6-dioxa-1,8-octane-dithiol) (PSDODT) via an inverse vulcanization reaction, as well as by changing the feed composition, and thus the sulfur content of the polymer. Then, the synthesized PSDODTs with various weight ratios of sulfur and DODT (30:70, 40:60, and 50:50) were used as an alternative to elemental sulfur, and these were also mixed with carbon host materials, such as carbon black (CB) and reduced graphene oxide (rGO). Subsequently, the electrochemical performances of these materials were evaluated as cathode materials for Li-sulfur batteries. Among the developed cathode materials, the 40S:60DODT-rGO composite showed enhanced specific capacity with good cyclic performances in comparison to the 30S:70DODT-CB combination. In addition to that, it has been identified from the results that the organosulfur based polymer PSDODT can be utilised as an alternative to conventional elemental sulfur, and this opens up some new research and development possibilities in the field of Li-sulfur batteries.