Effect of succinonitrile on electrical, structural, optical, and thermal properties of [poly(ethylene oxide)succinonitrile]/LiI-I-2 redox-couple solid polymer electrolyte is reported for the first time. For the poly(ethylene oxide)-succinonitrile blend-based electrolyte electrical conductivity was noted as high as similar to 3 x 10(-4) S cm(-1) at 25 degrees C. which is an order of magnitude higher than that of pure poly(ethylene oxide)-based electrolyte. It also exhibited relatively better pseudo-activation energy (similar to 0.08 eV). X-ray diffractometry, polarized optical microscopy, and differential scanning calorimetry studies revealed that succinonitrile is helpful in reducing the poly(ethylene oxide) crystallinity due to its plasticizing property. FT-IR study showed significant modification of the poly(ethylene oxide) chain conformation due to the succinonitrile. (C) 2012 Elsevier Ltd. All rights reserved.