Polarized optical microscopy (POM) results show that ZSM-5 has great influence on both the nucleation stage and the growth stage of PEO spherulites. Part of ZSM-5 particles can act as the nucleus of PEO spherulites and thus increase the amount of PEO spherulites. On the other hand, ZSM-5 can restrain the recrystallization tendency of PEO chains through Lewis acid–base interaction and hence decrease the growth speed of PEO spherulites. The increasing amount of PEO spherulites, decreasing size of PEO spherulites and the incomplete crystallization are all beneficial for creating more continuous amorphous phases of PEO, which is very important for the transporting of Li+ ions. An adequate amount of ZSM-5 can enhance the room temperature ionic conductivity of PEO-LiClO4 based polymer electrolyte for more than two magnitudes.