Preparation of polymeric nano-composites with finely controlled structure, especially, at nano-scale, is still one of the most perspective modification ways of the properties of polymeric composites. Paper actuality is based on growing need for non-combustible and safe battery electrolytes, which operate portable electronic devices. Polyethylene oxide solid composite electrolytes containing lithium triflate, multiwall carbon nanotubes and graphene by solution casting and hot-pressing method were prepared. Dielectric spectroscopy, surface resistivity measurements were performed to evaluate nanoparticles influence on the dielectric characteristics of the electrolyte material. Observed enhancement of dielectric conductivity is connected to the addition of the Li+ ions and incorporation of the electrically conductive nanoparticles to the polymer electrolyte