Engineering Densely Packed Ion-Cluster Electrolytes for Wide-Temperature Lithium–Sulfurized Polyacrylonitrile Batteries

The electrolyte plays an essential role in the advancement of lithium-sulfur batteries (LSBs), as it not only transports the charge carriers but also extensively influences sulfur conversion mechanisms and electrode-electrolyte interphases formed on the electrode surface, thereby directly impacting battery performance. However, the majority of existing electrolytes suffer from incompatibility with either the Li anode or the sulfur cathode. Here, we develop a densely packed ion-cluster electrolyte (DPIE) through the strategic combination of a weakly solvating solvent and an inert diluent, resulting in the self-assembly of abundant compact ion-pair aggregates within its structure. This peculiar solvation structure promotes fast Li⁺ desolvation, the formation of robust electrode-electrolyte interphases, and the suppression of polysulfide dissolution. Leveraging the tailored DPIE, room-temperature Li||sulfurized polyacrylonitrile (SPAN) batteries demonstrate 300 stable cycles with a capacity retention of 97.8% and a steady Coulombic efficiency exceeding 99.9%. Even under a limited negative/positive areal capacity ratio of four, the Li||SPAN cells exhibit good stability over 250 cycles with 97.1% capacity retention. Furthermore, Li||SPAN batteries show impressive stability over a wide temperature range spanning from -20 to 60 °C and exhibit reversibility at -10 °C over 200 cycles. This electrolyte design enables LSBs with prolonged operational lifetimes, rapid charging capabilities, and expanded temperature tolerance.