P(VDF-TrFE), solid polymer electrolytes were prepared using the ionic liquid N,N,N-trimethyl-N-(2-hydroxyethyl) ammonium bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2]. The morphology, polymer phase, and thermal and electrochemical properties have been determined by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC) and impedance spectroscopy, respectively. The addition of the ILs in P(VDF-TrFE) affects the microstructure, thermal stability and ionic conductivity of the polymer membrane. It was found that the ionic conductivity increases as the ionic liquid (IL) content increases with a maximumvalue at room temperature of 1.7 × 10−5 S·cm−1 for an IL composition of 32 wt.%. The temperature behavior in the ionic conductivity is thermally activated, following the Arrhenius equation, the high ionic conductivity resulting from the large carrier numbers of the IL. The electrochemical potential windowshows 1.0 V at 4.0 V that these solid polymer electrolytes are adequate for energy storage devices.