Credit: Image courtesy of Lawrence Berkeley National Laboratory
Rechargeable lithium-sulfur batteries, where the electrodes are made of lithium (Li) metal and sulfur (S) separated by a liquid electrolyte, could replace lithium-ion batteries if we could understand how to stop reactions that diminish the battery performance. During battery operation, polysulfide ions are formed at the sulfur electrode, but they can dissolve into the electrolyte and eventually limit the battery performance. Calculations show extensive cluster formation (left structure (Li2S4)n) occurs for shorter polysulfides, which limits the solubility of the shorter ions in pure solvent. Less clustering occurred when a lithium salt was added to the solvent to form the liquid electrolyte (right structure (Li2S4)n-x TFSIn’), which unexpectedly increased the solubility of the shorter ions in the electrolyte. These snapshots of the structures provide insights on electrolyte design to enable better batteries.