Ion Conductive Behavior of Oligoether/Zwitterion Diblock Copolymers Containing Magnesium Salt

Abstract

Rechargeable magnesium (Mg) batteries are envisioned as next generation batteries. The development of solid polymer electrolytes with high ionic conductivity will contribute to realize not only high performance Mg batteries but also reliable and safe devices. In this study, diblock copolymers (PPEGMA m -b-SPB n ) with oligoether (PEGMA) and zwitterionic (SPB) side-chains are synthesized in order to develop novel Mg-ion electrolytes. PPEGMA m -b-SPB n copolymers with various unit ratios are synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. PPEGMA m -b-SPB n exhibited two distinct glass transition temperatures. Phase-separated structures are observed by atomic force microscope (AFM) measurements. PPEGMA m -b-SPB n /Mg-salt composites exhibited a glass transition temperature due to the mixture formation of PEGMA and SPB blocks. When the unit numbers of m and n are 44 and 75, respectively, PPEGMA m -b-SPB n /Mg-salt ([EO]: [Mg] = 6: 1) exhibits the highest ionic conductivity of over 10 −4 S cm −1 at 60 °C among 11 composites prepared in this study.