Polymeric Ionic Liquid-poly(ethylene glycol) Composite Polymer Electrolytes for High-Temperature Lithium-Ion Batteries

A new family of composite polymer electrolytes (CPEs) is developed by blending pyrrolidinium-based polymeric ionic liquid [P(DADMA)TFSI], poly(ethylene glycol) [PEG800], and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). The structure, thermal behavior, electrochemical properties of these CPEs, as well as their potential application in high-temperature lithium-ion batteries (LIBs) are studied. The FTIR result reveals the interactions among P(DADMA)TFSI, PEG800, and Li+ cations. X-ray diffraction and differential scanning calorimetry measurements show that the as-prepared CPEs have amorphous structures. Furthermore, CPEs exhibit satisfactory ionic conductivity, as well as high thermal and electrochemical stabilities. In addition, Li/LiFePO4 cells with the as-prepared CPE at 0.2C rate can achieve a discharge capacity of about 150mAhg(-1) at 80(o)C, with good capacity retention. These findings indicate that the as-obtained CPEs have great potential for applications as safe electrolytes in high-temperature LIBs.