Single Lithium-Ion Conducting Solid Polymer Electrolyte with Superior Electrochemical Stability and Interfacial Compatibility for Solid-State Lithium Metal Batteries

Lithium metal batteries are being explored in meeting ever-increasing energy density needs. Because of serious dendritic lithium issues in liquid-state electrolytes, it is generally thought that solid-state electrolytes are potential alternatives for lithium metal batteries. Herein, we design a new single lithium-ion conducting lithium poly[(cyano)(4-styrenesulfonyl)imide] (LiPCSI) to replace the conventional dual-ion conducting salt for use in solid polymer electrolytes (SPEs) that successfully suppress the growth of lithium dendrites. Owing to highly delocalized anion moiety and oxidation-resistant cyano group, the tailored PEO₈-LiPCSI SPE exhibits extremely high Li⁺ transference number (0.84) as well as oxidation potential (5.53 V vs Li⁺/Li). The symmetric Li/PEO₈-LiPCSI/Li cell runs for 1000 h at 60 °C without a short circuit. The rechargeable solid-state Li/PEO₈-LiPCSI/LiFePO₄ cell discharges a capacity of 141 mAh g⁻¹ with retention over 85% during 80 cycles. These merits enable the proposed PEO₈-LiPCSI SPE to be very promising for solid-state lithium metal battery applications.