Electrolytes comprising poly(ethylene carbonate) (PEC)/poly(trimethylene carbonate) (PTM C) with lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) are prepared by a simple solvent casting method. Although PEC and PTMC have similar chemical structures, they are immiscible and two glass transitions are present in the differential scanning calorimetry (DSC) measurements. Interestingly, these two polymers change to miscible blends with the addition of LiTFSI, and the ionic conductivity increases with increasing lithium salt concentration. The optimum composition of the blend electrolyte is achieved at PEC6 PTMC4 , with a conductivity as high as 10-6 S cm-1 at 50 °C. This value is greater than that for single PEC- and PTMC-based electrolytes. Moreover, the thermal stability of the blend-based electrolytes is improved as compared to PEC-based electrolytes. It is clear that the interaction between CO groups and Li+ gives rise to a compatible amorphous phase of PEC and PTMC.
Keywords: lithium batteries; poly(ethylene carbonate); poly(trimethylene carbonate); polymer blends; solid polymer electrolytes.
© 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.