Design strategies and future directions of sparingly solvating electrolytes for lithium-sulfur batteries

Lithium–sulfur batteries (LSBs) offer high theoretical energy density and cost advantages, but their commercialisation remains hindered by several technological challenges, such as the lithium polysulfide shuttle effect. This review critically assesses recent advances in sparingly solvating electrolytes (SSEs), including highly concentrated, localized high-concentration, and weakly solvating systems, as strategies for enabling lean-electrolyte operation and long cycle life. Through solvation structure modulation, SSEs have demonstrated the ability to regulate polysulfide solubility, promote the formation of stable interphases, and maintain efficient ion transport, particularly under lean conditions. The merits and limitations of each SSE class are discussed, with a focus on key design principles, environmental sustainability, and cell-level constraints. Emphasis is placed on the need for evaluation under practical operating conditions to assess scalability and commercial viability. Finally, future directions are proposed, including hybrid electrolyte architectures and dynamic solvation control, to advance the transition of LSBs from laboratory to market-ready technology. Lithium-sulfur batteries offer high theoretical energy density and cost advantages, but typically suffer from the lithium polysulfide shuttle effect. This Review explores the use of sparingly solvating electrolytes as a way to address this, providing an assessment of the different classes of material, including the need for assessment under real operating conditions.