Preparation of a ROMP-type imidazolium-functionalized norbornene ionic liquid block copolymer and the electrochemical property for lithium-ion batteries polyelectrolyte membranes

Abstract

Imidazolium-functionalized norbornene ionic liquid block copolymers are synthesized via ring-opening metathesis polymerization (ROMP). The solid polyelectrolytes were prepared by blending the copolymers with various contents of lithium bis(trifluoromethanesulphonyl)imide. The effects of the polymerized ionic liquid (PILs) compositions on the properties, morphology, and ionic conductivity of the polyelectrolytes are investigated. The polymer with 50.7 mol% PIL displays a long-range ordered lamellar structure, and its corresponding polyelectrolyte achieves the best ionic conductivity with 7.44 × 10⁻⁶ S cm⁻¹ at 30 °C and 4.68 × 10⁻⁴ S cm⁻¹ at 100 °C, respectively. The ionic conductivity is enhanced by 1 order of magnitude compared to the polyelectrolytes with lower polymerized ionic liquid block compositions. In addition, the polyelectrolytes are electrochemically stability up to 4.2 V versus Li/Li⁺, indicating their suitable electrochemical property for lithium-ion battery application.