Degradable Polymer Electrolytes Encapsulated with Ionic Liquids for Enhanced Ionic Conductivity and Stable Interfaces...

In green and sustainable energy utilization, solid electrolytes are called to be environmentally friendly and degradable. Meanwhile, there has been a concerted effort to improve ion transport and interfacial stability of solid-state electrolytes to enhance solid-state battery (SSLBs) development. Herein, we have made a polymer electrolyte encapsulated with a degradable ester-based ionic liquid (IL) of 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr₁₄TFSI). This enables rapid degradation to be achieved, up to complete degradation within 12 h under alkaline conditions, owing to the robust interplay occurring between the Pyr14⁺ cations present in the IL and the ether functional groups; this interaction fosters a consistent encapsulation of the IL within the polymeric matrix structure, thereby introducing a large number of Li⁺. At 25 °C, an ionic conductivity of 7.6 × 10^-4 S cm^-1 is achieved. In addition, Pyr₁₄TFSI facilitates the in situ development of a solid electrolyte interphase (SEI) layer abundant in lithium fluoride (LiF) and lithium nitride (Li₃N), which effectively suppresses lithium dendrite growth, representing stable cycling performance even at 25 °C. Therefore, this work provides a simple and feasible approach for designing green SSLBs with degradability, fast ion conduction, and good interface stability.