The spesific features of ion transport are studied in the nanocomposite system based on a network matrix synthesized by radical polymerization of polyethylene glycol diacrylate in the presence of liquid aprotic electrolyte containing 1 M LiBF4 in γ-butyrolactone and SiO2 nanopowder. The self-diffusion coefficients measured by 7Li NMR spectroscopy with pulsed field gradient have a maximum at 2 wt % SiO2 nanoparticles. Nanocomposites of the latter composition exhibit the highest cation transport numbers (0.49) and the maximum of conductivity in the temperature interval under study (from –70 to 100°С): 4 mS/cm at 20°С and 1 mS/cm at –70°С. The second conductivity maximum at 6 wt % is characterized merely by the low effective activation energy of conduction. Possible mechanisms are invoked to explain the increase in conductivity. The first mechanism is based on the increase in the number of mobile charge carriers which may be a result of salt dissociation to ions, the second mechanism is associated with the development of a large number of favorable pathways for ion transport.