UC Berkeley

Fast, selective transport is essential to the performance of a variety of developing battery chemistries directed at clean energy storage. Redox flow batteries, which store charge in active material solutions, rely on the sequestration of anolyte and catholyte materials in their respective electrode compartments while allowing ion transport between compartments to maintain charge balance. To this end, redox centers designed to realize redox potential, stability, and solubility targets are conjoined to produce charge storing redoxmers – encompassing redox-active monomers, oligomers, and polymers – with unique rheological and kinetic properties in solution. Redoxmers are paired with porous polymer membranes whose pore chemistry and architecture are intentionally designed to promote selectivity, offering advantages in both active material blocking and charge transport. Integration of these materials and design principles into new flow cell chemistries that account for their unique fluid dynamic properties is directed at accessing long-duration energy storage targets that remain inaccessible with existing battery technology. In this dissertation, I will discuss the role of active material and microporous polymer design in achieving selective transport in battery applications. I will first describe the application of an oligoethylene oxide scaffold to produce liquid redoxmers that are infinitely miscible with organic electrolytes and size-sieved by well-established microporous polymer membranes. Subsequently, I will describe my work applying diversity-oriented synthesis to develop a library of polymers of intrinsic microporosity (PIMs) offering polymers with desirable transport properties for various applications. This PIM library encompasses a wide assortment of pore chemistries and architectures and was screened to identify chemistries offering attractive Li+ transport properties. The final two sections apply the synthetic strategies used in developing the PIM library to produce polymers capable of stable, selective transport in alkaline aqueous systems, and to enhance our understanding of permeability–selectivity trade-offs for PIMs in non-aqueous flow batteries.