Synergistic Interactions of a Pyridinium Nitride Cationic Skeleton and Succinonitrile for Electrolytes with High Stability for Solid-State Batteries

Solid-state polymer electrolytes are one of the most widely researched types of solid-state electrolytes. However, they still suffer from inherent limitations, including insufficient room-temperature ionic conductivity and limited cycle stability. Recent advances demonstrate that the strategic incorporation of fillers or plasticizers can effectively modify the PEO-based electrolyte. In this work, a pyridinium-based nitride cationic porous organic polymer (iCN@TFSI) has been successfully synthesized via a multicomponent reaction (MCR) strategy integrating Knoevenagel condensation with quaternization amination. The synthesized iCN@TFSI was incorporated into the PEO/LiTFSI matrix as a functional filler. This design utilizes the pyridinium-based cationic framework’s strong attraction to TFSI– anions, which effectively weakens the Li+–TFSI– coordination through electrostatic interactions, thereby promoting Li+ dissociation and generating additional ion transport pathways. On this basis, succinonitrile synergistically couples with iCN@TFSI to further improve the electrochemical properties. As a result, the 10%iCN@TFSI–15%SN composite electrolyte exhibits the best ionic conductivity (1.89 mS cm–1, 90 °C) and lithium-ion transference number (0.51, 60 °C). Taking into account both mechanical performance and interfacial stability, the 10%iCN@TFSI–10%SN electrolyte was utilized in the lithium–sulfur (Li–S) battery, which exhibits excellent cycling stability, maintaining a high discharge specific capacity of 566.7 mAh g–1 after 500 cycles at 1 C, with a capacity fade rate of only 0.014% per cycle.