Effects of pressure, temperature and volume on the electrical conductivity of polymer electrolytes

Three features of the electrical conductivity of ion conducting polymers are described. First, it is shown how the ratio of the apparent isochoric activation energy to the isobaric activation enthalpy, EV*/H*, can be used to separate the contributions of volume and temperature to the electrical conductivity. Next, the effect of pressure on the conductivity is considered. Finally, the concept of scaling is discussed and is applied to poly(propylene glycol) containing LiCF3SO3. All results are interpreted in terms of the defect diffusion model (DDM). First, it is shown how EV*/H* can be calculated using the DDM. Next, the effect of pressure on the conductivity is given a physical interpretation. Finally, it is pointed out that in the DDM, scaling arises because the critical temperature can be represented approximately by a power law. Consequently, in the DDM scaling is always approximate.