Relationship between ion conductivity and morphology of complexes formed from poly(ethylene oxide) and potassium thiocyanate

Solid polymer electrolytes with different stoichiometries were prepared from molten poly(ethylene oxide) (PEO) containing various amounts of potassium thiocyanate (KSCN). X‐ray diffraction and conductivity measurements revealed that both morphology and conductivity were dependent on their stoichiometries, and that the highest conductivity at ambient temperature corresponded to 3.98 × 10−6 S cm−1 for the amorphous complex with the composition of X = 0.15 (X = [KSCN]/[EOunit]). The temperature dependence of the conductivity showed a WLF‐type behavior for the amorphous complex, whereas it showed an Arrhenius‐type behavior for a crystalline complex with the composition of X = 0.2. It was also found that the ionic mobility at 60°C of the amorphous complex was approximately 2.25 times greater than that of the crystalline complex. Furthermore, results of the infrared reflection spectroscopy measurements suggested that the mobility of potassium ion (K+) was correlated to the degree of the interaction between K+ and ether oxygens.