Higher-order polysulfides induced thermal runaway for 1.0 Ah lithium sulfur pouch cells

Comprehensive analyses on thermal runaway mechanisms are critically vital to achieve the safe lithium -sulfur (Li-S) batteries. The reactions between dissolved higher-order polysulfides and Li metal were found to be the origins for the thermal runaway of 1.0 Ah cycled Li-S pouch cells. 16-cycle pouch cell indicates high safety, heating from 30 to 300 degrees C without thermal runaway, while 16-cycle pouch cell with additional electrolyte undergoes severe thermal runaway at 147.9 degrees C, demonstrating the key roles of the electrolyte on the thermal safety of batteries. On the contrary, thermal runaway does not occur for 45cycle pouch cell despite the addition of the electrolyte. It is found that the higher-order polysulfides (Li2Sx > 6) are discovered in 16-cycle electrolyte while the sulfur species in 45-cycle electrolyte are Li2Sx <= 4. In addition, strong exothermic reactions are discovered between cycled Li and dissolved higherorder polysulfide (Li2S6 and Li2S8) at 153.0 degrees C, driving the thermal runaway of cycled Li-S pouch cells. This work uncovers the potential safety risks of Li-S batteries and negative roles of the polysulfide shuttle for Li-S batteries from the safety view.(c) 2022 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Comprehensive analyses of thermal runaway mechanisms are crucial for the safe operation of lithium-sulfur (Li-S) batteries. The thermal runaway of 1.0 Ah cycled Li-S pouch cells is attributed to the reactions between dissolved higher-order polysulfides and Li metal. Adding electrolyte significantly affects the thermal safety, with the 16-cycle pouch cell experiencing severe thermal runaway while the 45-cycle pouch cell remains stable. The presence of high-order polysulfides (Li2Sx > 6) and exothermic reactions with cycled Li contribute to the thermal runaway of Li-S pouch cells.