In Situ Polymerized Electrolytes with Fully Cross-Linked Networks Boosting High Ionic Conductivity and Capacity Retention for Lithium Ion Batteries

In this report, quasi-solid polymer electrolytes (QPEs) based on dicationic imidazolium-based poly(ionic liquid) (PIL) cross-linker end capped with polyethylene glycol (PEG) segments have been UV cured directly onto lithium anode via an in situ solventless strategy, creating a direct, effective, and versatile method for electrolyte production. Depending on the composition, room temperature ionic conductivities are found to vary between 0.7 and 1.1 mS cm–1, while compressive elastic moduli reveal the values between 0.072 and 0.349 MPa observed at a 5% strain. These results, together with FT-IR analysis, indicate that fully cross-linked networks can be formed in the QPE-1:1.6 sample, which is conducive to generating well-connected ion channels and affords the assembled lithium ion batteries (LIBs) with a wide electrochemical window and a remarkable discharge capacity retention (153 mAh g–1 at 0.2 C and 133 mAh g–1 at 1 C) at 25 °C. Also, the adopted in situ polymerization can contribute to an enhanced electrolyte/electrode interfacial compatibility and conformal attachment, suppressing the growth of lithium dendrites and extending the cycle life of the assembled battery. Both the outstanding electrochemical properties of QPE-1:1.6 and the facile fabrication process potentially make it one of the promising electrolyte candidates for future LIBs developments.