A totally solid polymer electrolyte composition with high ionic conductivity and enhanced mechanical properties is provided. This electrolyte composition is produced by polymerizing a monomer composition comprising a molten quaternary ammonium salt having a polymerizable functional group introduced therein and a charge transfer ion source in the presence of a polymeric reinforcing material. The polymeric reinforcing material can be formed into a composite of polymer blend morphology by dissolving the monomer composition and the reinforcing material in an appropriate organic solvent and polymerizing the solution. Alternatively, the composite can be obtained by impregnating a porous sheet or film as the reinforcing material with the monomer composition and effecting polymerization. An electrolyte for lithium ion battery can be obtained by selecting a lithium salt as the charge transfer ion source; an electrolyte for fuel cell by selecting a proton donor; and an electrolyte for dye sensitized solar cell by selecting a redox ion pair. A polymer electrolyte composition not containing the charge transfer ion source is also useful as an electrolyte for electrolytic capacitor.