Liquid crystalline electrolytes derived from the 1,12-disubstituted [closo-CB11H12]– anion

Abstract

A new approach to anisotropic liquid electrolytes is explored. Thus, a non-ionic liquid crystalline host exhibiting SmC and N phases is doped with a lithium salt containing an anion structurally similar to the host and derived from the weakly-nucleophilic [closo-CB11H12]– cluster. The resulting unaligned 5, 10, and 15 mol% solutions of the lithium salt in the host were investigated by optical, thermal, powder XRD and impedance spectroscopy methods in a broad temperature range. The results showed that the increasing concentration of the ionic additives essentially does not affect the mesophase stability, but expands the lamellar SmA phase possessing ion conducting channels. At the same time ionic conductivity, σ, monotonically increases from 10-8 to 10-4 S cm−1 with increasing temperature (20–120 °C) and with increasing Li+ ion concentration. The Arrhenius analysis of the conductivity data revealed progressively decreasing activation energy EaIC from crystalline (∼102 kJ mol−1), to SmA (∼70 kJ mol−1) and to nematic (∼30 kJ mol−1) phases. The electrochemical stability window of the 15 mol% electrolyte was determined as 1.3–4.6 V vs Li metal anode.