Organoboron ion conductive materials for target cation transport

Abstract

A variety of organoboron ion conductive materials were prepared via hydroboration, dehydrocoupling reaction, imidazole-borane complex formation and so forth. By using mesitylborane, defined organoboron polymer electrolytes bearing an alkylborane or boric ester unit were conveniently prepared. The polymers obtained showed ionic conductivity of 3.39 × 10⁻⁵ ˜ 2.11 × 10⁻⁶ S/cm at 50°C. The lithium transference number of these polymers was significantly higher than that for polyethers without organoboron units. Alkylborane type polymer electrolytes showed especially improved selectivity of lithium ion conduction because of stronger Lewis acidity of the alkylborane unit. Novel imidazolium molten salts bearing an organoboron anion receptor were also prepared by hydroboration of 1-allyl-3-ethylimidazolium bromide and subsequent ion exchange reaction. From the lithium transference number observed, it was demonstrated that anion trapping of organoboron unit works much efficiently in molten salt systems than was in polyether systems.