Relationship between swelling ratio and structure of three dimensional acrylic polymers in gel electrolytes

The safety of lithium ion batteries can be improved by using ion conductive gels as electrolyte. For this purpose, gel electrolytes are required to exhibit high ionic conductivity and paired with a low temperature dependence. In this study, several matrix polymers for gel electrolytes with different degrees of polymerization between crosslinks and side chains were prepared. Their swelling ratio and ionic conductivity were measured. The matrix polymer which was made from ethylene glycol dimethacrylate as multifunctional monomer and vinyl acetate as monofunctional monomer showed a high swelling ratio. Ionic conductivity of the gel electrolyte was 4.9 mS/cm at 20°C and its activation energy was 14.3 kJ/mol. Our results suggest that the use of block copolymerization type monomers that show a weak interaction between polymers and lithium ions are effective.