Improvement In Ionic Conductivity and Mechanical Properties Observed In Multi-Functional Block Copolymer Modified Solid Polymer Electrolytes for Li+ Ion Batteries

Solid polymer electrolyte (SPEs) with high ionic conductivity and high mechanical properties are of particular interest for increasing the performance of Li⁺ ion batteries. Our previous studies indicated that copolymers could be very good candidates for SPE materials due to the variable properties contributed by each block. A series of multi-functional copolymers applied in this research was poly (ethylene oxide)-block-polyethylene, PEO-b-PE, which contains a conductive block (PEO) and a structural block (PE). This study examines the effects of molecular weight of the copolymers and weight percent PE block on both ionic conductivity and mechanical properties of the resulting SPEs. The ternary polymer electrolyte PEO/PEO-b-PE/LiClO₄ was examined using differential scanning caloriometry (DSC), tensile testing, and dielectric spectrum analysis. It was found that decreasing the molecular weight of copolymer resulted in ~350% increase in tensile modulus, ~133% increase in ultimate tensile strength, and a slight increase in ionic conductivity and dielectric properties. It was also observed that increasing the wt% PE to 80 wt% in the copolymer resulted in ~100% increase in ionic conductivity and dielectric properties were also increased while maintaining high mechanical properties of the electrolyte film with 50 wt% PE in the copolymer.