Tuning the Solvation Structure of a Weakly Solvating Cyclic Ether Electrolyte for Wide‐Temperature Cycling of Lithium‐Sulfurized Polyacrylonitrile Batteries

Abstract Sulfurized polyacrylonitrile (SPAN) cathodes in high energy‐density Li‐metal batteries have garnered widespread interest owing to their good cycling stability and moderately high capacities. However, their application is hindered by the low prevalence of advanced electrolytes that can simultaneously mitigate polysulfide generation at the cathode and stabilize the Li‐metal anode. Here, a weakly solvating electrolyte is presented, employing a single solvent tetrahydropyran (THP). The solvation structure is effectively tuned by adjusting the salt concentration to stabilize both the Li‐metal anode and SPAN cathode. This approach enables stable cycling with high SPAN loadings (≈5 mg cm −2 ) and lean electrolyte contents (≈5 µL mg SPAN −1 ) across a wide temperature range: 0 °C, room temperature, and 50 °C. A pouch cell with a high SPAN loading and a low electrolyte‐to‐SPAN (E/SPAN) ratio of 3 µL mg −1 shows a stable 79.1% capacity retention after 40 cycles. Additionally, THP can be effectively employed in localized high‐concentration electrolyte (LHCE) systems to reduce the diluent‐to‐solvent ratio for greater LHCE viability. The study demonstrates the potential of weakly solvating solvents in Li‐SPAN batteries, offering a pathway for their practical application.