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

Poly(oxyethylene) (POE) is frequently used as suitable compo-<br /> nent to prepare solid polymer electrolytes (SPEs), due to its: (i)<br /> ability to coordinate and dissociate doping salts; (ii) good<br /> mechanical properties; and (iii) high chemical and electro-<br /> chemical stability. With the aim to obtain calcium secondary<br /> batteries, here we describe the preparation and studies of<br /> crosslinked Ca-polycondensate (NPCY) electrolytes with formula<br /> NPCY/(CaTf2)x based on fragments of POE chains and CaTf2. The<br /> molecular weight of POE precursors is Y = 400 and<br /> 1000 g <middle dot> mol 1. The effect of POE molecular weight on the<br /> thermal, structural, and electrical properties of NPCY/(CaTf2)x is<br /> investigated revealing that in mesoscale this materials show: (i)<br /> two different nanodomains with polyether chains both "free"<br /> (not coordinating the cation) and involved in 4-4 coordination<br /> cages of Ca2 + metal ions; (ii) f alpha-fast, f alpha-cross and f alpha-slow relaxation<br /> modes of polyether chains, detected by broadband electrical<br /> spectroscopy, which are coupled with the long-range charge<br /> migration pathways of SPEs; (iii) that triflate (Tf ) anions, which<br /> act as plasticizers, modulate the inter-chain migration processes<br /> of Ca2 + between polyether coordination sites. Finally, the<br /> conductivity values of NPCY/(CaTf2)x, which is up to 10 4 S <middle dot> cm 1<br /> at 80 degrees C, classify NPCY/(CaTf2)x as promising SPEs for the<br /> development of calcium secondary batteries.