Interplay between Conductivity, Matrix Relaxations and Composition of Ca-Polyoxyethylene Polymer Electrolytes

In this report, the conductivity mechanism of Ca2+-ion in polyoxyethylene (POE) solid polymer electrolytes (SPEs) for calcium secondary batteries is investigated by broadband electrical spectroscopy studies. SPEs are obtained by dissolving into the POE hosting matrix three different calcium salts: CaTf2, Ca(TFSI)(2) and CaI2. The investigation of the electric response of the synthetized SPEs reveals the presence in materials of two polarization phenomena and two dielectric relaxation events. It is demonstrated that the nature of the anion (i. e., steric hindrance, charge density and ability to act as coordination ligand) and the density of dynamic crosslinks of SPEs is fundamental in the establishment of ion-ion/ion-polymer interactions. The long-range charge migration processes occurring along the two revealed percolation pathways of the electrolytes are generally coupled with the polymer host dynamics and depend on the temperature and the anion nature. This study offers the needed tools for understanding Ca2+ conduction in POE-based electrolytes.

Automated summary

This study investigates the conductivity mechanism of Ca2+ ions in polyoxyethylene (POE) solid polymer electrolytes (SPEs) for calcium secondary batteries through broadband electrical spectroscopy studies. The research reveals the importance of the nature of the anion and the density of dynamic crosslinks of SPEs in ion-ion/ion-polymer interactions. Long-range charge migration processes in the electrolytes are coupled with polymer host dynamics and depend on temperature and anion nature.