Zwitterionic Polymer Promotion of Selective Ion Transport in Ionic Liquid Electrolytes

Recent experimental results have demonstrated that zwitterionic (ZI) gel electrolytes comprising lithium salt and ionic liquid are useful in the advancement of decoupling mechanical stiffness and ionic conductivity. However, the underlying mechanism of such decoupling between the structural and dynamic properties of the ZI gel electrolytes remains unsolved. In this work, we perform a systematic investigation to understand the impact of the ZI/ Lithium molar ratio on the structural and dynamic properties using atomistic molecular dynamics simulations. Our model system is comprised of ZI poly (2-methacryloyloxyethyl phosphorylcholine) (pMPC) loaded with 1M LiTFSI/N-butyl-N-methylpyrrolidinium (BMP) TFSI ionic liquid electrolyte. Our structural analyses show strong lithium ion interaction with the anionic portion of the polymer consistent with the physical network characteristic observed in the experimental results. We also present ion coordination statistics and ion pair lifetimes results to rationalize and identify the mechanistic origins of the dynamic properties of the ZI gel electrolytes.