A Fusible Orthoborate Lithium Salt with High Conductivity in Solutions

Synthesis, analysis, and electrochemical properties of a new lithium salt with an exceptionally large, weakly coordinating anion, lithium bis{1,2‐tetra(trifluoromethyl) ethylenediolato (2−)‐O,O′} borate { LiB [ OC ( CF 3 ) 2 ] 4 } , are described. This salt, whose anion contains 24 fluorine atoms, can be fused at remarkably low temperatures ( 120 ° C ) and is stable up to 280 ° C . The salt has a low conductivity in the molten state, only 7.1 × 10 − 6 S cm − 1 at the melting point of 120 ° C due to its quasi‐molecular character. However, its solutions in molecular solvents are extremely conductive. The maximum conductivity of LiB [ OC ( CF 3 ) 2 ] 4 in dimethoxyethane (DME) is 11.1 × 10 − 3 S cm − 1 at 25 ° C . The electrochemical stability for each of the DME and propylene carbonate solutions is at least 4.5 V vs. Li + / Li .