CAREER: Towards a Comprehensive Theoretical Framework to Predict Multiscale and Multicomponent Electrolyte Transport in Porous Media

To combat climate change and work towards a sustainable future, advancements are crucial in energy and environmental technologies. These technologies include (i) electrochemical capacitors (ECs), which are energy storage devices that only require a few seconds to charge, and (ii) capacitive deionizers (CDIs), which are desalination devices that remove salt from water by applying electricity. Both ECs and CDIs employ porous electrodes to maximize performance. These electrodes consist of a complex network of pores through which ions move when voltage is applied. While materials research on these technologies has proliferated, understanding of the factors controlling the performance of EC and CDI remains limited. By combining applied mathematics techniques with modern computing capabilities, this award will develop and experimentally validate computer simulations to understand how multiple ionic species move through pore networks. The results from this award will accelerate the design and scale-up ECs and CDIs, for instance, through optimal design of 3D-printed electrodes. The integrated education program will incorporate research outcomes to create web-based interactive simulations that are available for everyone, design an open online course, to prepare the future sustainable economy workforce, and broaden the participation of first-generation middle and high school students through scientific workshops. Fundamental challenges in multicomponent electrolyte transport are that the systems consist of multiple lengthscales and timescales, and the transport of species is coupled through an electric field. Existing modeling approaches are unable to capture experimental trends observed in porous electrodes because they focus on binary electrolytes in unconfined geometries and overlook the impact of multiple electrolytes and confined geometries. This award aims to bridge this major knowledge gap in the field of electrokinetics. By exploiting the thinness of the pores, this award will develop a new theoretical framework based on perturbation expansions, akin to lubrication theory in fluid mechanics, that will overcome the limitations of existing approaches. Specifically, the work will (i) model transport of an arbitrary number of ions inside a charged cylindrical pore for an unrestricted combination of ion valences, diffusivities, size, and relative Debye length, (ii) formulate and experimentally validate a new theoretical framework that predicts ion transport through a complex network of pores, and (ii) investigate the combined effect of redox reactions and double layers in porous media to characterize structure-property-performance relationships for EC and CDI. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.