This paper demonstrates a new modified precipitated silica (SiO2) and PAN/TMS – poly(acrylonitrile)/sulfolane – polymeric matrix as a composite gel polymer electrolyte for a lithium-ion battery. Synthetic inorganic material was obtained by the emulsion method with cyclohexane as the organic phase and sodium silicate solution as a precipitating agent. The characterisation included determination of dispersion and morphology of the systems (particle size distribution, scanning electron microscope images), as well as impedance analysis, cyclic voltammetry and charging/discharging. It was found that the silica fillers were homogeneously dispersed in the polymeric matrix, while conductivity and electrochemical stability of porous polymer electrolytes were enhanced. Applicability of the prepared gel electrolytes for the Li-ion technology was estimated on the basis of specific conductivity measurements. Basic electrochemical properties of the composite gel polymer electrolyte was also presented based on PVdF-HFP/TMS/LiPF6/SiO2. A significantly poorer capacity and conductivity were observed. The Li|GPE|LiMn2O4 cell using modified SiO2 in the composite gel polymer electrolyte PAN/TMS shows a high discharge capacity.