Graphene-based molecular sieving separators enhance lithium–sulfur battery stability

Researchers from Purdue University, Vanderbilt University and University of Florida recently reported a graphene-based separator design that addresses critical limitations of lithium–sulfur (Li–S) batteries. While Li–S batteries promise higher energy densities and reduced weight compared to conventional lithium-ion systems, their practical use has long been hindered by the lithium polysulfide (LiPS) shuttling effect, which leads to severe capacity fading and poor cycle life. Traditional approaches, such as slurry-coating LiPS-adsorbing materials onto polypropylene (PP) separators, help mitigate shuttling but increase both mass and volume, thereby reducing the overall energy density of the system.

The research team instead used nanoporous atomically thin membranes (NATMs) composed of graphene, fabricated via chemical vapor deposition, as a lightweight and selective barrier. These graphene layers feature subnanometer pores (~0.7–1.0 nm) that allow the transport of solvated lithium ions (0.54–1.26 nm) while effectively blocking larger LiPS species (0.81–1.69 nm). Owing to their atomic thinness and negligible mass, the membranes function as molecular sieves that suppress polysulfide migration without introducing significant ionic resistance.

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