Cyclic Ammonium-Based Polyester Ionenes: Chemical Structures and Properties for Electrochemical Applications AITranslate

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DOI：https://doi.org/10.1021/acsapm.3c01486

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Cyclic ammonium-based polyester ionenes have been synthesized through condensation polymerizations of dihydroxyl ionic salts and terephthaloyl chloride monomers. The study investigates the thermal and electrochemical properties of the ionenes, including thermal stability, glass transition temperature, and ionic conductivity, based on their structure–property relationship. The ionenes were made with various combinations of cyclic ammonium (pyrrolidinium or piperidinium), C11-terephthalate-C11 or C6-terephthalate-C6, spacer, and bis(trifluoromethanesulfonyl)imide (Tf2N–) or hexafluorophosphate (PF6–) anions. The most polyester ionenes were found to be amorphous, transparent, and flexible at room temperature. The ionenes with C11-pyrrolidinium Tf2N– (11a-Tf2N) exhibit the lowest glass transition temperature (−10 °C) and the highest ionic conductivity (2.34 × 10–5 S/cm) at 70 °C. They also demonstrate good electrochemical stability up to 4.3 V (vs Li/Li+) and are very comparable to the conventional liquid electrolyte. Moreover, the composite mixture of 11a-Tf2N ionene and 50 wt % LiTf2N salt exhibits a higher ionic conductivity of 1.41 × 10–5 S/cm at room temperature than those of the composite mixtures of 10, 30, and 70 wt % of LiTf2N. These findings suggest that the synthesized polyester ionenes can be applicable in future lithium secondary batteries as an additive of liquid or quasi-solid electrolytes or as a component of flexible polymer electrolyte systems.