Communication Macromolecular Rapid Communications wileyonlinelibrary.com 221 © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/marc.201500562 salts. [1,5–7] For this system, the ionic conductivity of the cell is insured both by the migration of lithium cation and its counter anion which induces salt concentration polariza- tion problem. [8] To overcome this power (performance) limi- tation, the use of polyanionic block copolymers to create a single-ion conductor has been recently proposed. [9–11] For instance, by covalently linking the trifluoromethane-sul- fonylimide (TFSI) anion on polystyrene (PS)-based blocks of an ABA triblock copolymer, Armand and co-workers have produced PSLiTFSI- b-PEO- b-PSLiTFSI SCE which combines an excellent Li-ion conductivity with a markedly improved mechanical strength. [11] Although SCE materials are attractive as next-generation electrolytes, since they are designed to overcome crit- ical dendrite growth and solvent evaporation which are critical issues in conventional solvent based-electrolytes, these materials are generally less conductive than solvent electrolytes. One way to optimize the ionic conductivity within solid copolymer electrolytes requires the formation of out-of-plane domains such that conduction occurs via direct transport between the two electrodes as opposed to blocking one resulting from (defect-less) in-plane domain orientation. Nanodomain alignment perpendicular to the electrode, achieved by magnetic [12] or electric [2] driving Well-defined single-ion diblock copolymers consisting of a Li-ion conductive poly(styrenesu- lfonyllithium(trifluoromethylsulfonyl)imide) (PSLiTFSI) block associated with a glassy poly- styrene (PS) block have been synthesized via reversible addition fragmentation chain transfer polymerization. Conductivity anisotropy ratio up to 1000 has been achieved from PS- b-PSLiTFSI thin films by comparing Li-ion conductivities of out-of-plane (aligned) and in-plane (anti- aligned) cylinder morphologies at 40 °C. Blending of PS- b-PSLiTFSI thin films with poly(ethylene oxide) homopolymer (hPEO) enables a substantial improve- ment of Li-ion transport within aligned cylindrical domains, since hPEO, preferentially located in PSLiTFSI domains, is an excellent lithium-solvating material. Results are also com- pared with unblended and blended PSLiTFSI homopolymer (hPSLiTFSI) homologues, which reveals that ionic conductivity is improved when thin films are nanostructured. Anisotropic Lithium Ion Conductivity in Single- Ion Diblock Copolymer Electrolyte Thin Films Karim Aissou,* Muhammad Mumtaz, Özlem Usluer, Gilles Pécastaings, Giuseppe Portale, Guillaume Fleury, Eric Cloutet, Georges Hadziioannou* Dr. K. Aissou, Dr. M. Mumtaz, Dr. Ö. Usluer, Dr. G. Pécastaings, Dr. G. Fleury, Dr. E. Cloutet, Prof. G. Hadziioannou Laboratoire de Chimie des Polymères Organiques Université de Bordeaux – CNRS UMR 5629 – ENSCPB B8 Allée Geoffroy Saint Hilaire F-33615 Pessac Cedex, France E-mail: karim.aissou@enscbp.fr; hadzii@enscbp.fr Dr. G. Portale Netherlands Organization for Scientific Research (NWO) DUBBLE-CRG at the ESRF F-38000 Grenoble, France 1. Introduction Nanostructured block copolymer (BCP) films are particu- larly attractive materials in the design of lithium [1] and proton [2] conductive solid copolymer electrolytes (SCEs) for energy storage applications. [3] These solvent-free electrolytes consist of ionic conductive nanochannels (such as lamella or cylinders) surrounded by glassy domains which provide a good mechanical strength over critical dendrite growth occurring at the Li metal/electrolyte interface. [4] Salt-complexed PEO-based SCE is one of the most studied lithium ion conductive material due to the good ability of PEO coordination sites to dissolve lithium Macromol. Rapid Commun. 2016, 37, 221−226