Abstract
Described below are the results of our investigations of the electrical and electrochemical properties of thin films of polyethylene oxide (PEO) electrolytes [with and without 12‐Crown‐4 ether (12Cr4)] as a function of temperature and in the frequency regime 100 kHz–0.1 Hz. These measurements were made on electrolytes containing 
, or 
salts. At a given temperature, the bulk conductivity, σ (S cm−1), for a particular salt, depends on the 12Cr4 concentration, with σ reaching a maximum for a ratio of 12Cr4 to Li of 0.003. Of the three salts studied, σ is the highest for 
for the same 12Cr4 ratio. The ac and dc measurements yield a lower charge transfer resistance 
for 12Cr4‐incorporated samples than for samples without. Plating/stripping of Li occurs at a potential closer to Li+/Li for 12Cr4 samples. The conductivities of thin (100 μm) and thick (400 μm) films are similar. The observation of a >45° spur at the low‐frequency regime in the ac impedance measurements on 
and 
electrolytes conditioned at 40°C overnight has been explained in terms of a constant phase angle element.