Lonically Conductive Polymers
In 1834 Michael Faraday reported that when lead fluoride (PbF2) was heated red hot, it conducted an electric current and so did the metallic vessel it was heated in. This was a startling observation, since most simple salts are electronic insulators. The high conductivity that Faraday observed is now known to be due to ionic conductivity, and not electronic conductivity. At elevated temperatures (500-700°C) the fluoride anion possesses high ionic conductivity and can easily be transported through the lead fluoride lattice. This was the first report of a high ionic conductivity solid electrolyte. Until the mid-1970s all research on solid ionic conductors had centered on inorganic compounds (primarily ceramics, such as the various phases of alumina, stabilized zirconia, etc.). With the discovery of new ionic conducting polymers by Wright,21,22 Armand,2,3 and others, and the numerous advantages that ionic conducting polymers have over ceramics in device fabrication and operating temperature range, it is not surprising that fast ionic conduction in polymers is currently an area of great interest. This interest is a result of a desire both to understand the ionic conduction mechanism in polymers and to use these polymers in applications such as high-energy-density batteries, electrochronic displays, specific-ion sensors, and other electrochemical devices that capitalize on the unique electronic, ionic, and mechanical properties of ionic conducting polymers.