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

Abstract 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/LiFePO 4 cells with the as‐prepared CPE at 0.2C rate can achieve a discharge capacity of about 150 mA h g −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.