A Low‐Viscosity Electrolyte With Fluorine‐Rich Interphase Empowers Stable High‐kinetics and Cold‐Resistant SPAN Cathodes

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium‐metal batteries due to its intrinsic stability and ability to circumvent the shuttle effect. However, it is still challenging to achieve high reversible capacity and cycling stability, mainly due to the intrinsic sluggish kinetics and unstable electrode/electrolyte interphases. Herein, we design a LiFSI‐based electrolyte that leverages anion participation to regulate the solvation structure, enabling robust electrode/electrolyte interphases on both the Li anode and SPAN cathode. Such an optimized environment effectively suppresses dendritic lithium growth and preserves the structural integrity of the SPAN cathode during repeated cycling. Further empowered by its high ionic conductivity of 13.63 mS cm −1 , the Li/SPAN batteries achieve an outstanding reversible capacity of 1015 mAh g S −1 after 1350 cycles and retain a capacity of 880 mAh g S −1 after 400 cycles even at −20°C. Moreover, the assembled Li/SPAN pouch cell exhibits excellent cycling stability, maintaining a specific capacity of 1043 mAh g S −1 after 100 cycles at room temperature and exhibiting an ultralow capacity decay rate of 0.25% per cycle at −20°C. This work provides a rational electrolyte design strategy toward durable Li/SPAN batteries with enhanced low‐temperature performance.