A micro-porous polymer blend electrolyte based on polyvinylidene fluoride-co-hexa fluoropropylene (PVdF-co-HFP) and polyacrylonitrile (PAN) was prepared by phase inversion technique with different compositions. The ionic conductivity of micro-porous polymer blend electrolyte films were studied by varying the PAN content in the (PVdF-co-HFP) matrix. It was observed that the ionic conductivity of micro-porous polymer blend electrolyte increases with increase in PAN content. The effect of lithium salt concentrations was studied for the micro-porous polymer blend electrolyte by measuring the conductivity at different temperatures in the range of 301-353 K. The micro-porous polymer blend electrolyte was subjected to XRD, SEM and TG/DTA analysis to determine the antorphosity nature, surface morphology and thermal stability of the polymer electrolyte, respectively. Linear sweep voltammetry and dc-polarization studies were also performed to find the stability and lithium transference number of micro-porous polymer blend electrolyte, respectively. Finally, charge-discharge studies were carried out in an assembled cell with carbon anode and LiSr0.25Mn1.75O4 cathode and micro-porous polymer blend electrolyte in between the above electrodes. (c) 2005 Published by Elsevier B.V.