Theory-Enabled High-Throughput Screening of Ion Dissociation Explains Conductivity Enhancements in Diluted Ionic Liquid Mixtures

Abstract

The growing demand for room-temperature ionic liquids (RTILs) for energy applications necessitates the development of an efficient screening platform. In this study, we successfully developed a fully automated high-throughput RTIL screening platform specifically designed for assessing ionic conductivity. By utilizing the 96 wells of a microtiter plate as individual electrolysis cells, we measured the ionic conductivity of 22 different RTILs, encompassing various combinations of cations and anions, and benchmarked the values with existing literature. We also employed the screening platform to investigate the conductivities of RTIL mixtures with a nonaqueous solvent, ethylene glycol (EG). Specific combinations of RTILs with EG result in approximately 200% enhancement in the conductivity values compared to the pure RTILs. To understand the underlying mechanisms responsible for this enhancement, we developed a theoretical framework for ionic conductivity that considers factors such as the degree of dissociation, viscous forces, and molal volume of the RTIL-EG mixtures. The optimized electrolyte mixture was then employed in the migration-assisted moisture gradient (MAMG) CO 2 capture process to study the effects of improved ionic conductivity on the energy efficiency of the process. Notably, the enhanced conductivity of the RTIL-EG mixture led to a nearly 50% reduction in energy consumption for capturing CO 2 . These outcomes highlight the effectiveness of our strategy in screening RTILs and improving existing processes. Moreover, this fully automated high-throughput setup, combined with the developed theoretical framework, provides a comprehensive platform for screening and studying RTIL mixtures with different solvents, enabling their application in various fields.

Simplified Universal Equations for Ionic Conductivity and Transference Number

“…However, the degree of ion dissociation varies in concentrated solutions. 23 To account for this effect, we include ion dissociation constant ξ ( ) in the conductivity expression as follows…”

“…The diffusion coefficient and other physical properties of these two ionic liquids are reported elsewhere. 23…”

Effect of K+ Force Fields on Ionic Conductivity and Charge Dynamics of KOH in Ethylene Glycol

“…Ionic conductivity also plays an important role in determining the energy efficiency of electrolytic and galvanic cells used in manufacturing, energy storage, , surface treatment, and separation processes. , Owing to the wide range of applications, the electrolytes need to be tailored to specific physicochemical property requirements. − Appropriate choice of ionic and molecular constituents can meet these specifications; however, due to an extremely large chemical space of ionic and molecular species, it is impractical to evaluate all formulations experimentally. Computational techniques − facilitate in-silico property estimation and high-throughput screening to identify relevant formulations, thereby accelerating the electrolyte development process . Furthermore, computational techniques can provide unique spatial and temporal insights into microscopic structure , and molecular behavior that can complement experiments.…”

“…Computational techniques 21 − 23 facilitate in-silico property estimation and high-throughput screening 24 to identify relevant formulations, thereby accelerating the electrolyte development process. 25 Furthermore, computational techniques can provide unique spatial and temporal insights into microscopic structure 26 , 27 and molecular behavior that can complement experiments. It is important to note that the accuracy of these methods is sensitive to simulation parameters, including force fields, 28 − 30 and errors in simulation parameters often translate to substantial offsets between the predicted and experimental values.…”