Regulating Polysulfide Clustering with an Anion Acceptor for Low-Temperature Sulfur Batteries

The performance of the lithium-sulfur battery at harsh conditions of lean electrolyte and low temperature is impeded by nanometric clustering of lithium polysulfides (LiPSs), which inherently hinders sulfur reaction kinetics. Here we describe a cluster-disrupting strategy wherein a fluorinated borane anion acceptor, tris(perfluorophenyl)borane, is exploited to regulate the LiPSs solvation structure and to promote their reactions under harsh conditions. The electron-deficient anion acceptor molecules bond with the electron-rich LiPSs via soft Lewis acid-base interactions, which disrupts LiPSs' clustering and promotes Li₂S solvation, facilitating a three-dimensional Li₂S growth via solution-mediated mechanism at low temperatures. With the borane anion acceptor, the cell shows a significantly improved capacity at -25 °C. Impressively, this strategy enables stable cycling of a 1.83 Ah pouch cell at 0 °C retaining 96.0% capacity over 50 cycles. Our study provides a general methodology for manipulating the fundamental electrolyte chemistry to regulate LiPSs clustering and improve sulfur batteries at harsh conditions.