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 LiCB11H12 and NaCB11H12 salts, 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.

Development of 4V-Class Bulk-Type All-Solid-State Lithium Rechargeable Batteries by a Combined Use of Complex Hydride and Sulfide Electrolytes for Room Temperature Operation

“…In other reports, high lithium [30][31][32][33] and sodium 30,[32][33][34][35] , have been discovered. Repeated battery operation of all-solid-state batteries by using some of the above materials has been successfully demonstrated.…”

“…Repeated battery operation of all-solid-state batteries by using some of the above materials has been successfully demonstrated. 31,32) In complex hydride solid electrolytes, the cation transport rate is closely related to the reorientational dynamics of the complex anions, containing hydrogen. 6,7,[36][37][38] On the basis of this knowledge, diversi cation of the complex hydride electrolyte has rapidly progressed with regards to crystal structure and composition.…”

Halogenated Sodium-closo-Dodecaboranes as Solid-State Ion Conductors

“…[8][9][10][11] LiBH 4 shows fast Li-ion conductivity above a polymorphic phase transition, which can be stabilized to room temperature by anion substitution of BH4 -by I -12,13 or by nanoconfinement. 14 [15][16][17][18][19] The high conductivity in these compounds is linked to the highly disordered high temperature polymorphs, where partially occupied cation sites and fast reorientational dynamics of the anion promote excellent cation mobility. Perchlorinated lithium-closo-boranes, Li 2 B 12 Cl 12 and Li 2 B 10 Cl 10 , were proposed as liquid electrolytes in Li/SOCl 2 battery cells in the early 1980s, where the extraordinary stability of [B n Cl n ] 2--anions (n = 10, 12) towards temperature and the Li anode were a significant advantage.…”

Substituent‐Stabilized Organic Dianions in the Gas Phase and Their Potential Use as Electrolytes in Lithium‐Ion Batteries

“…As the anion size increases, the distance between the metal cation and the anion center also increases, thus reducing the binding energy between the cation and the anion . As this is a desired property of a good electrolyte, and theoretical predictions have been verified by experiments, we studied the potential of the organic anions discussed here to be building blocks for new electrolytes for Li‐ion batteries. We calculated the equilibrium geometries of Li 2 X and LiX − , focusing on X=B 2 C 4 (CN) 6 and BC 4 (CN) 5 , and also the energy needed to remove the first and second Li + ion.…”