Coupling Ionic Network Reconstruction With Interfacial Electrostatics Shielding Resolves the Interphase Stability‐Transport Trade‐Off for High‐Temperature Durable Li‐SPAN Batteries

ABSTRACT High‐performance lithium‐sulfurized polyacrylonitrile (SPAN) batteries require an electrolyte that simultaneously delivers robust lithium metal stability and efficient bulk ionic transport. However, existing electrolyte engineering strategies generally improve interfacial stability at the expense of bulk transport properties. Herein, by introducing 1‐methyl‐1‐propylpyrrolidinium bis(fluorosulfonyl)imide (PY13FSI), we achieved a reconstruction of the ionic network, coupled with the electrostatic shielding effect at the interface, breaking the traditional trade‐off between interphase stability and bulk transport kinetics. While forming inorganic‐rich LiF/Li 3 N interphases on both the cathode and anode to block lithium polysulfide shuttling and homogenize lithium deposition, the electrolyte simultaneously delivers a high ionic conductivity approaching 10 mS cm −1 and an impressive Li + transference number of 0.71. Consequently, Li||SPAN cells deliver outstanding long‐term cycling stability and rate capability, retaining 94.1% capacity retention after 1100 cycles at 1 C. Meanwhile, stable cycling performance is observed at 60°C. Commercially viable full cells (with a thin Li anode and high‐loading cathode) still demonstrate exceptional performance with a capacity retention of 90.8% after 200 cycles. This work presents an effective strategy to break the conventional trade‐off between interphase stability and bulk ionic transport, offering fresh insights into the future design of advanced electrolytes for high‐energy‐density battery systems.