A series of new solid polymer electrolytes (SPE) were prepared based on polyurethane／acrylate comb cross-linked polymers．The ionic conductivity of the electrolytes could reach 3.4 × 10-5 S·cm-1 at 25℃．Raman spectroscopy

DSC

SEM and conductivity measurement were used to study interrelations among salt concentration

ion states and ionic conductivity．In solid polymer electrolytes with high salt concentrations

it was considered that the ion pairs may play an important role in ion transport．When the salt content was low

the free ion was the main form of salt in the electrolytes．The content of ion pairs increased with increasing the salt content．The ion pair became an important form of salt in the electrolyte when the salt content was high

and the ionic conductivity increased greatly in a certain range．Under these conditions

the ion pairs should act as all active entity in the ionic conduction of the electrolytes．When the SPE films were in atmosphere

the ions were unstable

and they would congregate and form crystallinites．Proper conditions could keep the ion stability of the polymer electrolyte films．