Nano‐ <scp> SiO ₂ </scp> Composite Solid Polyelectrolyte Membranes Based on Bis‐Imidazole Cationic‐Functionalized Benzonorbornadiene Block Copolymers for Solid‐State Lithium‐Ion Batteries

ABSTRACT Solid polyelectrolytes (SPEs) have garnered considerable attention and extensive research due to their exceptional flexibility, low cost, and ease of industrial production. This study synthesized bis‐imidazole cationic functionalized benzonorbornadiene block copolymers rP(NB‐MGE‐ b ‐BenzoNBD‐BisIm + TFSI − ) via ring‐opening metathesis polymerization (ROMP). The block copolymers were blended with lithium trifluoromethanesulfonate (LiTFSI) and nano SiO 2 to prepare the composite solid polyelectrolytes membrane (CSPEMs) rP(NB‐MGE‐ b ‐BenzoNBD‐BisIm + TFSI − )/LiTFSI/SiO 2 by a solution casting method for applications in lithium‐ion batteries (LIBs). This research investigates the effect of different nano‐SiO 2 content on the ionic conductivity and electrochemical stability of the composite SPEs. The relationship between the intrinsic structure and properties of rP(NB‐MGE‐ b ‐BenzoNBD‐BisIm + TFSI − )/LiTFSI/z wt% SiO 2 ( z = 0, 2.5, 5.0, 7.5) was studied. When the SiO 2 content is 5.0 wt%, the maximum ionic conductivity reaches 9.3 × 10 −5 S cm −1 at 30°C and 1.5 × 10 −3 S cm −1 at 80°C. The NCM811/CSPEM/Li battery exhibits an initial reversible discharge capacity of 149.7 mAh g −1 at a current density of 0.2 C, with a coulombic efficiency maintained above 96%. After 50 cycles at a current density of 0.2 C, the capacity remains at 148.9 ± 8 mAh g −1 , with the coulombic efficiency continuing to exceed 96%, which demonstrating robust cycling stability.