Lithium conducting ionic liquids based on lithium borate salts

The simple reaction of trialkoxyborates with butyllithium resulted in the obtaining of new lithium borate salts: Li{[CH3(OCH2CH2)(n)O](3)BC4H9}, containing oxyethylene substituents (EO) of n = 1, 2, 3 and 7. Salts of n >= 2 show properties of room temperature ionic liquid (RTIL) of low glass transition temperature, T-g of the order from -70 to -80 degrees C. The ionic conductivity of the salts depends on the number of EO units, the highest conductivity is shown by the salt with n = 3; in bulk its ambient temperature conductivity is 2 x 10(-5) S cm(-1) and in solution in cyclic propylene sulfite or EC/PC mixture, conductivity increases by an order of magnitude. Solid polymer electrolytes with borate salts over a wide concentration range, from 10 to 90 mol.% were obtained and characterized. Three types of polymeric matrices: poly(ethylene oxide)(PEO), poly(trimethylene carbonate) (PTMC) and two copolymers of acrylonitrile and butyl acrylate p(AN-BuA) were used in them as polymer matrices. It has been found that for systems of low salt concentration (10 mol.%) the best conducting properties were shown by solid polymer electrolytes with PEO, whereas for systems of high salt concentration, of the polymer-in-salt type, good results were achieved for PTMC as polymer matrix. (C) 2010 Elsevier B.V. All rights reserved.