Lithium ion-poly (ethylene oxide) complexes. I. Effect of anion on conductivity

The ionic conductivities of a series of lithium salt-poly (ethylene oxide) complexes have been studied from ambient temperature to approximately 400 K. Plots of the variation of conductivity with temperature indicate a transition in behaviorr between 330–360 K. The activation energies in the high temperature regime vary from 0.16 eV (LiH₂PO₄) to 1.45 eV (LiNO₃) and in the low temperature regime from 0.86 eV (LiBF₄) to 2.47 eV (LiH₂PO₄). Conductivity values for the salts tested also exhibits wide variation. The lowest measured conductivity was 10^?9 S/cm and the highest was 10^?4 S/cm. The anion plays an important role in the total measured conductivity. Salts with oxygen-containing anions form complexes with an apparent higher conductivity when the sample is vacuum dried. This suggets hydrogen bonding with residual water in the polymer impeding anionic mobility. In one of the salt-complexes (LiBF₄) residual water and thermal history, were shown not to significantly affect conductivity.