In this work, composite polymer electrolytes (CPEs), that is, 80%[(1-x)PIL-(x)SNI-20%LiTFSI, are successfully prepared by using a pyrrolidinium-based polymeric ionic liquid (P(DADMA)TFSI) as a polymer host, succinonitrile (SN) as a plastic crystal, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a lithium salt. XRD and DSC measurements confirm that the as-obtained CPEs have amorphous structures. The 80%[50%PIL-50%SN]-20%LiTFSI (50% SN) electrolyte reveals a high room temperature ionic conductivity of 5.74 x 10(-4) S cm(-1), a wide electrochemical window of 5.5 V, as well as good mechanical strength with a Young's modulus of 4.9 MPa. Li/LiFePO4 cells assembled with the 50% SN electrolyte at 0.1C rate can deliver a discharge capacity of about 150 mAh g(-1) at 25 degrees C, with excellent capacity retention. Furthermore, such cells are able to achieve stable discharge capacities of 131.8 and 121.2 mAh g(-1) at 0.5C and 1.0C rate, respectively. The impressive findings demonstrate that the electrolyte system prepared in this work has great potential for application in lithium ion batteries. (C) 2016 Elsevier B.V. All rights reserved.