An Ion Conducted Tour Through Some Polymer Electrolytes

The development of both dry polymer electrolytes and gel or inert-support polymer electrolytes is discussed and their performances compared. Conductivities have been measured for comb-branch polymers, with cation-binding side-chains, as a function of temperature and in nearly every case the response was non-Arrhenius. This can be explained by recognizing that ion transport in dry polymer matrices is a function of the flexibility of the polymer chains at the temperature of measurement. Ways to maximize this by attempting to lower the glass transition temperature of the polymer/salt mixtures and improve the ionization of the salt, are described. The active participation of the polymer chain in ion transport can be modified by moving to externally plasticized systems, gels, or inert polymer supports. Two such examples are described, ß-cyclodextrin/ dimethylacetamide/salt gels and highly porous polyethylene support films loaded with electrolyte. These show a reduced dependence of conductivity (s) with change in temperature (T) which is a desirable feature in device manufacture, and an Arrhenius (log s-1/T) behaviour. While these systems have several attractive features and they have been designed to minimize solvent leakage, there is no guarantee that leakage will not occur over a period of time and this limitation must be recognized. © 1998 Society of Chemical Industry.