title: Unparalleled Lithium and Sodium Superionic Conduction in Solid Electrolytes with Large Monovalent Cage-like Anions.
abstract: Solid electrolytes with sufficiently high conductivities and stabilities are the elusive answer to the inherent shortcomings of organic liquid electrolytes prevalent in today's rechargeable batteries. We recently revealed a novel fast-ion-conducting sodium salt, Na2B12H12, which contains large, icosahedral, divalent B12H122-anions that enable impressive superionic conductivity, albeit only above its 529 K phase transition. Its lithium congener, Li2B12H12, possesses an even more technologically prohibitive transition temperature above 600 K. Here we show that the chemically related LiCB11H12and NaCB11H12salts, which contain icosahedral, monovalent CB11H12-anions, both exhibit much lower transition temperatures near 400 K and 380 K, respectively, and truly stellar ionic conductivities (> 0.1 S cm-1) unmatched by any other known polycrystalline materials at these temperatures. With proper modifications, we are confident that room-temperature-stabilized superionic salts incorporating such large polyhedral anion building blocks are attainable, thus enhancing their future prospects as practical electrolyte materials in next-generation, all-solid-state batteries.
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6102, USA; Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742-2115, USA.
authors.forename: Wan Si
authors.initials: WS
authors.lastname: Tang
authors.affiliation: WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Unemoto
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6102, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Energy Nanomaterials, Sandia National Laboratories, Livermore, CA 94551, USA.
authors.forename: Vitalie
authors.initials: V
authors.lastname: Stavila
authors.affiliation: Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Motoaki
authors.initials: M
authors.lastname: Matsuo
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6102, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Wu
authors.affiliation: WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Sendai 980-8577, Japan; Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Orimo
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6102, USA.
authors.forename: Terrence J
authors.initials: TJ
authors.lastname: Udovic