Solid Polymer Electrolytes

Solid Polymer ElectrolytesMost often, the term "electrolyte" refers to liquid solutions and melts of substances, although a lot of solid substances with ionic conductivity have been known for a long time. Solid polymer electrolytes (SPE) are substances with a polymeric structure. Polymers also comprise functional groups able to dissociate with formation of cations or anions. Their directed movement within the polymer structure determines its ionic conductivity. This phenomenon was discovered by Peter Wright, a chemist from Sheffield, in 1975. He proved that ethylene polyoxies (EPO) can serve as a basis for sodium and potassium salts, which leads to formation of solid polymer electrolytes. Michel Armand suggested using intercalated graphite compounds for electrodes, because lithium-polymer complexes can be used as solid electrolytes in electrodes structure. Lithium salt can be dissolved in a solvating polymer matrix for the direct interaction of cations and electron pairs. The complex is formed (as a result of favorable competition between the solvation energy and lattice salt energy) and becomes a good conductor at temperatures of 60-80° C.Nevertheless, the notion of the formation of a salt complex and the nature of the charge transport mechanism was not the same as in other solid electrolytes. They require a new model of processes in polymers which are traditionally connected with inorganic compounds and crystal structures. The standard model of research-type ceramic electrolytes (such as beta-alumina), which connects ion conduction defects in a crystal structure, proved to be unsuitable for polymers. In 1983 experiments and studies that movement of ions in salt-polymer complexes can not cause spontaneous changes in the resistance. Rather, it is the continuous movement occurring in the field of amorphous polymeric materials. The phenomenon of liquid-like conductivity in solid materials without the movement of the solution was very interesting from a theoretical point of view and could be used in electrochemical devices in the field of alternative energy and in fighting pollution. Polymer electrolytes can be easily manufactured in a form unavailable for systems containing liquids, and at the same time can be much safer than liquid electrolytes.So the basic properties of solid polymer electrolytes are low resistivity (tens of thousands times smaller than that of a liquid electrolyte), ability to keep working properties at high temperatures and their solid aggregate state, eliminating the deficiencies of a liquid electrolyte such as the possibility of leakage or evaporation. Through this they are widely used in modern batteries, and more recently, in the new super compact electrolytic capacitors.