Rechargeable lithium-sulphur (Li-S) batteries have theoretical high performance and low costs, but they are not considered reliable enough for widespread use. Now, Researchers at Pusan National University (PNU) in Busan, South Korea, have found a solution that improves durability.
The researchers developed a coating material based on the organic methylene blue dye. By coating the battery separator with the material, durability is increased.
The use of widely abundant sulphur in Li-S batteries significantly lowers their costs, compared to lithium-ion (Li-ion) batteries. But Li-S batteries have a few key issues that need to be solved before they are commercially viable.
The most prominent problem is the “polysulphide shuttling effect.” This phenomenon causes long chains of sulphur to leak from the cathode over time, permanently degrading the capacity of the battery with each charge-discharge cycle.
The PNU team, led by Professor Seung Geol Lee, Assistant Professor Jin Hong Lee, and Associate Professor Oi Lun Li, used a common organic dye called methylene blue as a precursor for a novel coating material for the separator of Li-S batteries.
The procedure involved dissolving the dye in aniline, a carbon-containing solvent, and subjecting the mixture to plasma engineering followed by heat treatment. This created a porous carbon material doped with both nitrogen and sulphur – two elements already present in methylene blue – that could be applied to the separator between the battery cathode and anode.
Thanks to the high heteroelement (element other than carbon) content (10%) of the doped carbon material obtained through this process, the polysulphide shuttling effect could be greatly mitigated, as the scientists demonstrated in various experiments. This, in turn, allowed them to produce more durable Li-S batteries with better electrochemical performances.
Overall, this study could motivate scientists worldwide to look into other potential applications of organic dyes outside textile dyeing.
The study will be published in Volume 430 of Chemical Engineering Journal on Feb. 15, 2022, Click here to read the abstract.