The electrochemical, bulk and interfacial properties of the polyethylene oxide (PEG) based composite solid electrolyte (CSE) comprising LiI, PEG, and Al2O3 have been evaluated for Li battery applications. The bulk interfacial and transport propel-ties of the CSEs seem to strongly depend on the alumina particle size. For the CSE films with 0.05 micron alumina while the bulk conductivity is around 10(-4) (mho cm(-1)) at 103 degrees C, the Li ion transport number seems to be close to unity at the same temperature. Compared to the PEO electrolyte this polymer composite electrolyte seems to exhibit robust mechanical and interfacial properties. We have studied three different films with three different alumina sizes in the range 0.01-0.3 micron. Effects of Al2O3 particle size on the electrochemical performance of polymer composite electrolyte will be discussed. With TiS2 as cathode a 10 mAh small capacity cell was charged and discharged at C/40 and C/20 rates respectively.