(410h) Charged and Ion-Containing Polyethers for Energy Storage Applications

To facilitate future energy storage devices, new polymeric materials need to be designed to facilitate ion separation and / or transport. Owing to favorable interactions between ions and their ether backbone, polyethers make excellent candidate materials for these applications. Adding charged or ionic moieties to polyethers can further enhance traits favorable to energy storage, such as ion selectivity. Here, we present our recent work on a platform for tunable polyethers that allows for control over composition, end group, and architecture and we utilize these synthetic handles to better understand structure-property relationships in energy storage contexts. We will discuss two recent projects. First, we synthesized a novel, amphoteric ion exchange membrane by grafting multi-functional polyethers to a PVDF-co-HFP membrane, to create a structure similar to Nafion at a fraction of the cost for applications as a separator in aqueous redox flow batteries (ARFBs). By controlling the incorporation of the charged polyether from 1% to 10% we saw commensurate increases in hydrophilicity, ion conductivity, and ion exchange capacity. We found that our dimensional stability and water uptake was improved over Nafion, but our ionic conductivity was a lower. However, this work demonstrates a facile way to modify off the shelf and inexpensive polymers with charged moieties to enhance ion transport. Work is on-going to optimize this membrane for specific ARFB systems. Second, we investigated polyether composite polymer electrolytes for lithium ion battery applications. Here, we grafted polyether chains from the surface of ceramic nanoparticles with controlled graft density and molecular weight. We dispersed these grafted nanoparticles in a polymer matrix and investigated the dispersion and conductivity as a function of salt content. We further modified the grafted polyether chain with anionic and cationic moieties to affect conductivity. In summary, we will discuss our platform to create charged and ionic polyethers and how we have utilized these polymers in disparate energy storage applications.