Solid polymer electrolytes (SPEs) are of interest as soft ion-conductive materials, and are particularly suitable for use in energy storage devices. To overcome the tradeoff relationship between the ionic conductivity and mechanical strength we propose an electrospun silica (SiO2) nanofiber (SNF) as a reinforcing additive. The SNF is synthesized by an electrospinning procedure without calcination. This SNF can be incorporated into a poly(ethylene oxide) (PEO)/lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) electrolyte plasticized by N-n-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (Pyr(14)TFSI). Tensile test confirms that the SNF greatly enhances the mechanical strength, with no sacrifice of conductivity. The ionic conductivity is improved by the IL and is over 10(-3) S cm(-1) at 80 degrees C and close to 10(-4) S cm(-1) at 30 degrees C. Linear sweep voltammetry for a stainless steel electrode reveals that the composite electrolyte has an oxidation stability suitable for lithium battery use. A prototype lithium polymer cell assembled using a LiFePO4 cathode can be efficiently cycled at 60-80 degrees C. (c) The Author(s) 2017. Published by ECS. All rights reserved.