Structure and Conductivity of Crosslinked Ca-POE Polymer Electrolytes for Secondary Batteries

Abstract Poly(oxyethylene) (POE) is frequently used as suitable component to prepare solid polymer electrolytes (SPEs), due to its: (i) ability to coordinate and dissociate doping salts; (ii) good mechanical properties; and (iii) high chemical and electrochemical stability. With the aim to obtain calcium secondary batteries, here we describe the preparation and studies of crosslinked Ca-polycondensate (NPCY) electrolytes with formula NPCY/(CaTf2)x based on fragments of POE chains and CaTf2. The molecular weight of POE precursors is Y=400 and 1000 g/mol. The effect of POE molecular weight on the thermal, structural, and electrical properties of NPCY/(CaTf2)x is investigated revealing that in mesoscale this materials show: (i) two different nanodomains with polyether chains both ?free? (not coordinating the cation) and involved in 4 coordination cages of Ca2+ metal ions; (ii) fα-fast, fα-cross and fα-slow relaxation modes of polyether chains, detected by broadband electrical spectroscopy, which are coupled with the long-range charge migration pathways of SPEs; (iii) that triflate (Tf?) anions, which act as plasticizers, modulate the inter-chain migration processes of Ca2+ between polyether coordination sites. Finally, the conductivity values of NPCY/(CaTf2)x, which is up to 10^-4 S/cm at 80°C, classify NPCY/(CaTf2)x as promising SPEs for the development of calcium secondary batteries.