Polymeric Ionic Liquids (PolyILs) has the advantage of being single ion conductors with high transference number for the mobile ion. However, the low conductivity at ambient temperature limits their practical applications. To improve conductivity, one of the strategies is to decrease the glass transition temperature (Tg) of the system. Here, we report a single-ion conducting polymer electrolyte with PDMS backbone, exhibiting low Tg and high lithium conductivity at room temperature. A regular polymer electrolyte, polymer of (methacryloyloxy)propylsulfonyl]-1-(trifluoromethylsulfonyl) Imide (MPA-TFSi Li), has been synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization as a reference sample. The PDMS backboned sample was synthesized via thiol-ene chemistry between the MPA-TFSi Li and thiol functionalized PDMS. The presence of flexible PDMS backbone drops the Tg significantly (from 334K to 284K) and increases conductivity (from 4.1*10-13 S/cm to 1.0*10-11 S/cm) at room temperature. Copolymerization with low-Tg PEO segments further decreased Tg. By tuning the ratio of EO:Li, the highest Li conductivity of 2.9*10-6 S/cm at ambient temperature was achieved. Tg value can be as low as 218K when EO:Li ratio is 18:1. Furthermore, study of the similar system with sodium ion proves that the same strategy also works for Na.

Improving single-ion conductivity of polymer electrolyte by softening backbone

2019 Spring National Meeting

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