Synthesis and characterization of solid single ion conductors based on poly[lithium tetrakis(ethyleneboryl)borate]

Abstract

Main chain anionic polymers with lithium cations, which have tetrakis(ethyleneboryl)borate as repeating units, were prepared and their ionic conductivities were determined. The polyelectrolyte is characterized both as-synthesized and after annealing at 275 °C by means of impedance spectroscopy, direct current measurements, ¹¹B, ¹³C, ¹H, static ⁷Li solid state NMR and IR spectroscopies, and DT/TG/MS techniques. The important feature of this novel solid polyelectrolyte is that the anion is immobilized on the polymer chain. The single ionic conduction was confirmed by the observation of constant current under dc electric field with non-blocking electrodes. The material exhibits a high Li⁺ transference number. The annealed polymer has an ionic conductivity of 1.6 × 10⁻⁶ S cm⁻¹ at 275 °C with an activation energy of 70 kJ mol⁻¹.