Tuning Lithium Transport in TFSI-based Polyzwitterion Electrolytes

Polyzwitterions show great promise for a broad range of applications due to their unique structure of bearing covalently tethered cations and anions. We recently exploited the self-assembling propensity of their polar groups to develop polymer electrolytes with ion motions strongly decoupled from segmental rearrangements, giving rise to superionic conductivity [Mater. Today 2025, 88, 322–327]. Here, this contribution focuses on LiTFSI doped poly(imidazolium-trifluoromethanesulfonimide), a polyzwitterion with bulky cation and anion groups, and investigates how ionic transport is affected by its specially designed morphology providing relatively weak Coulombic interactions. Our calorimetric results show that the glass transition temperature decreases progressively with increasing salt concentration, indicating enhanced segmental mobility of the polymer matrix. The conductivity measurements indicate strong ion-zwitterion interactions and partial ion associations, which restrict the mobility of charge carriers despite the relatively high polymer backbone flexibility. In addition, no ion-cluster formations were observed in our systems based on Small and Wide-Angle X-Ray Scattering measurements. These results underline the complex role played by the local polymer structure mediating inter-ionic interactions, and provide new insights for the design of high-performance polyzwitterionic-based solid-state electrolytes for energy storage applications.