In the future, lithium-sulfur (Li-S) rechargeable batteries could hold more energy and cost less than lithium-ion batteries if they can be made to last longer. A key challenge is preventing the polysulfide ions that must form at the sulfur electrode during discharge from being transported through the liquid electrolyte to the other electrode. Here, researchers discovered how the solubility and transport of polysulfide ions in the liquid electrolyte relates to the chain length of the polysulfide ion, the tendency of the ion to cluster, and the amount of lithium salt present in the electrolyte. It is noteworthy that polysulfides of any chain length or structure dissolved in the liquid electrolyte can contribute to poorer performance of the battery.