The successful synthesis of a new diblock copolymer, referred to as sulfonated polymerized ionic liquid (PIL) block copolymer, poly(SS-Li-b-AEBIm-TFSI), is reported, which contains both sulfonated blocks (sulfonated styrene: SS) and PIL blocks (1-[(2-acryloyloxy) ethyl]-3-butylimidazolium: AEBIm) with both mobile cations (lithium: Li+) and mobile anions (bis(trifluoromethylsulfonyl) imide: TFSI-). Synthesis consists of polymerization via reversible addition-fragmentation chain transfer, followed by post-functionalization reactions to covalently attach the imidazolium cations and sulfonic acid anions to their respective blocks, followed by ion exchange metathesis resulting in mobile Li+ cations and mobile TFSI- anions. Solid-state films containing 1 M Li-TFSI salt dissolved in ionic liquid result in an ion conductivity of > 1.5 mS cm(-1) at 70 degrees C, where small-angle X-ray scattering data indicate a weakly ordered microphaseseparated morphology. These results demonstrate a new ion-conducting block copolymer containing both mobile cations and mobile anions.