Predicting the Conductivity–Selectivity Trade-Off and Upper Bound in Ion-Exchange Membranes

Ion-exchange membranes (IEMs) are integral to electrochemical technologies utilized in water purification, energy generation, and energy storage. The effectiveness of these technologies is contingent upon the selective and rapid permeation of ions through IEMs. However, like most synthetic membranes, IEMs exhibit a trade-off between selectivity and permeability. Understanding the fundamental basis for this trade-off is essential for developing membranes that overcome this limitation. In this study, we present and validate a model that predicts the conductivity–selectivity trade-off in IEMs. We use this framework to assess the membrane structural properties that yield membranes at the frontier of this trade-off and then explore the potential for advancements in IEM design. Notably, the model predicts that preparing materials with higher charge densities could enhance performance by several orders of magnitude. This analysis unfolds a blueprint for substantial advancements in membrane design, potentially catalyzing breakthroughs in technologies for clean water and energy.