Abstract: A method is described for forming a solid electrolyte comprising a polymeric network structure containing an ionically conducting liquid for use in solid state electrochemical cells which comprises forming a mixture of a crosslinkable polysiloxane or a crosslinkable polyethylene oxide, an ionically conducting liquid, and an ionizable ammonium or alkali metal salt, and subjecting said mixture to actinic radiation to thereby crosslink said crosslinkable polysiloxane or crosslinkable polyethylene oxide to form a solid matrix through which said ionically conducting liquid interpenetrates to provide continuous paths of high conductivity in all directions throughout said matrix.