We prepared a ternary composite polymer electrolyte from poly(ethylene carbonate) (PEC), lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) and non-calcined silica nanofibers (SNFs) having 3 average diameters (300, 700, and 1000nm). The SNF composite electrolytes were obtained as homogeneous, self-standing membranes. The ionic conductivity of PEC/LiTFSI 100mol% was increased by the addition of SNFs, and the thinner SNFs with average diameter 300nm were most effective in improving the conductivity. The conductivity was of the order of 10(-4)S/cm at 60 degrees C. The lithium transference number of the SNF300 composite was greater than 0.7. Stress-strain curves of the composites indicated significant increases in Young's modulus and maximum stress for the PEC electrolytes. The 5% weight-loss temperature of the composites also improved with the addition of SNF.