It is shown that the addition of calix[6]pyrrole to polyether based electrolytes doped with LiBF4 results in an considerable increase in the cation transport number t(Li+) as confirmed by dc-ac current techniques as well as by PFG NMR studies. The value of tLi+ in composite electrolytes beyond a certain minimum value weakly depends on the concentration of added calix[6]pyrrole. The increase in lithium transference number is associated with a decrease in ionic conductivity of composite polymeric electrolytes compared to the pure PEO-LiBF4 systems. (c) 2005 Elsevier Ltd. All rights reserved.