Some features of interest for divalent polymer electrolytes are described. Attention is focussed on two contrasting roles for cations: providing chemical cross-links within the polymer matrix and offering a source of mobile charge carriers. The possible merits of using mixtures of two types of cation, one type for each role, is discussed. Alternative mixed salt systems containing two anions with a common cation are considered. Another class of mixed polymer electrolyte systems involving two divalent cations in conjunction with two monovalent anions is also examined in the context of illustrating competitive anion-cation interactions within the polymer matrix by EXAFS local structure techniques. Results for the systems PE015:ZnI2/Mg(CIO4)2, PEO15:ZnI2/Mg(CF3SO3)2, PEO15:CaI2/ZnI2 and PEO15:CaI2/CaBr2 are discussed.