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.