Solid polymer electrolytes cation exchange membrane-based

N. Mayo, R. Harth, U. Mor, D. Marouani, J. Hayon and A. Bettelheim, Electrochemical response to H2, 02, C02 and NH3 of a solid-state based on a cation- and anion-exchange membrane serving as a solid polymer electrolyte, Anal. Chim, Acta, 1995,310, 139-144. 

It is well known today that perhaps the most dramatic application of the fuel cell—an electrochemical device that may be based in the future upon the oxidation of aliphatic hydrocarbons— was in the Gemini Space Mission. In this application, the cell was based upon the use of a solid polymer electrolyte —a cation-exchange membrane in its acid form—but with hydrogen and oxygen as the fuels rather than an aliphatic hydrocarbon. Considerable research and development preceded and supported these successful missions and the units demonstrated that indeed the H2/O2 fuel cell was capable of extended performance at relatively high current densities—2l capability of fundamental importance in commercial applications. 

Some vinyl fluoride-based polymers with side chains of perfluorosulfonic acid (the Nation family) are important ion-exchange membrane materials used in practice for electrolysis of NaCl and in certain fuel cells. They show a proton conductivity of 0.01 S cm- at room temperature. However, such fast ionic transport occurs only when they are swollen with water. It is therefore not appropriate to call them solid electrolytes in the tme sense of the word. It was in 1970 that anionic conductivity, though not high, was reported for crown ether complexes such as dibenzo-18-crown-6 KSCN, in which cations are trapped by the ligand. " A few years later much higher cationic (instead of anionic) conduction was found in complexes of a chain-like polyether such as PEO or PPO with alkaline salts here, PEO stands for poly(ethyleneoxide), (CHjCHj-O), and PPO for poly(propyleneoxide)."2>"3 These were the flrst examples of tme polymer solid electrolytes and were followed by a great number of studies. Polymeric electrolytes are advantageous in practice because they are easily processed and formed into flexible Aims. 

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