Pregel compositions for polymer gel electrolytes, method of dehydrating pregel compositions, secondary cell, and electrical double-layer capacitor

A pregel composition is added to an organic electrolyte solution of an electrolyte salt in a nonaqueous solvent for causing the solution to gel and form a polymer gel electrolyte. The pregel composition is dehydrated by azeotropic distillation and has a moisture content of not more than 1,000 ppm as determined by Karl Fischer titration. Polymer gel electrolytes prepared with such a pregel composition have a good electrochemical stability, and are thus highly suitable for use in secondary cells and electrical double-layer capacitors.