Electrolytes with Controlled Polysulfide Insolvability for Lithium-Sulfur Batteries

With the rise in manufacturing and commercialization of electric vehicles and home-scale integrated battery systems, low cost and high energy batteries are imperative for meeting the demand of the near-future energy requirements. Lithium-sulfur (Li-S) battery is widely known as a promising candidate for next-generation batteries due to its high theoretical specific energy (2600 Wh kg -1 ), abundance in material, and potentially low cost. However, there are many challenges unique to Li-S battery chemistries that impede the practical implementation of Li-S batteries. The foremost known challenge is inhibiting the shuttling effect of polysulfide (PS) species, Li 2 S n (2 < n ≤ 8) that occurs during the discharge of the elemental S and the charge of the discharged product Li 2 S on the S cathode. The formed PS species can migrate from the S cathode to the Li metal anode and react with the Li resulting in loss of active materials and insulation of Li anode, and consequently reduced battery performance and cycle life. Managing the mechanism of PS formation and dissolution is paramount to developing a sustainable Li-S battery. Electrolyte formulation is a key strategy in overcoming the hurdles of Li-S batteries and controlling the degree of PS dissolution. Ether-based electrolytes are promising candidates due to their well-known compatibility with Li metal and their varying degrees of PS solvation and dissolution. This work focuses on designing electrolytes that optimizes the degree of PS dissolution and improving electrode-electrolyte compatibility with the elemental S cathode and the Li metal anode to enhance the cell stability and enable long-term cyclability. A series of electrolytes that have a more controlled degree of PS formation and solvability are developed to improve compatibility of the Li-S battery and enable superior cyclability.