Self-tracking, solvent-free low-dimensional polymer electrolyte blends with lithium salts

Solvent-free polymer electrolyte blends of the amphiphilic polyethoxide (I) and the polytetrahydrofuran copolymer (II) with LiClO4 or LiClO4/LiBF4 mix ture have been prepared. [GRAPHICS] In II -A- is either -CH2- (IIC1) or -CH2C(=CH2)CH2- (IID4), dc measurements using Li electrodes on the cells (Li / I/II-Li salt / Li) demonstrate a 's elf-tracking' process over ca. 24 h during which time conductivities increa se from ca. 10(-6) to 10(-3) S cm(-1) at 25 and 30 degreesC. The de results are supported by ac impedance measurements using indium tin oxide (ITO) el ectrodes in which the complexes undergo transitions at ca. 90 degreesC to g ive a conductivity after cooling of 6 x 10(-4) S cm(-1) at 20 degreesC with low temperature dependence. Structural analysis and molecular dynamics mod elling indicate that the cations occupy unimpeded helices of I and anions a re located in the interhelical spaces. Mechanisms of 'tracking' involving s hear-induced orientation of polymer I by polymer II and the redistribution of ions between I and II following imposition of the field are proposed. (C ) 2001 Elsevier Science B.V. All rights reserved.