Incorporation of organoboron unit to electrolytes has been a fruitful approach to prepare ion conductive madea showing high ionic conductivity and lithium transference number at the same time1,2. Furthermore, it is also effective to improve non-flammable property of the electrolytes. In recent years, we have been studying a series of organoboron ion-gel electrolytes prepared via in-situ sol-gel method3, 4 or dehydrocoupling of hydroboranes with various polymers5.When silicate matrix formation and radical polymerization of ionic liquid monomer were conducted simultaneously, transparent hybrid ion-gel electrolytes were obtained under a wide range of materials composition. Incorporation of the boron atom as borosilicate glass led to further improved ionic conductivity of resulting ion-gel electrolytes 3, 4. Morphological factor was found to be crucial for both ion conductive properties and thermal stabilities of the hybrid ion-gels.As a different strategy for efficient preparation of organic-inorganic hybrid type ion-gels, we examined a condensation of cellulose with boric acids in ionic liquid4. In these systems, condensation completed within 4 h. The obtained ion-gels exhibited ionic conductivity of 3.6 x 10-3 ~ 5.4 x 10-4 Scm-1 at 324K that are comparable to ionic liquids themselves. The ion-gels prepared using C6F5B(OH)2showed particularly high ionic conductivity. From the VFT (Vogel-Fulcher-Tamann) parameters, it was implied that high carrier number in this matrix is responsible for the observed high ionic conductivity.A series of cellulose based ion-gels including boric esters were also prepared by dehydrocoupling of cellulose with hydroboranes in ionic liquid5.In order to further increase the boron density in ion-gels, borylation of PVA was examined by dehydrocoupling of PVA with hydroboranes in ionic liquids. As a result of high boron incorporation density, maximum lithium transference number of 0.59 was observed at ambient temperature.

Organoboron ion-gel electrolytes and their lithium ion conductive properties

247th National Meeting (2014)

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