Abstract: Developing atomic- and molecular-level understanding of ion transport through electrolytes and ion transfer across electrochemical interfaces is critical to designing new materials for energy storage systems that can move beyond current Li-ion battery technologies. Although the framework and language used to describe ion coordination differs significantly between the liquid and solid state, similar principles drive ion transport in both systems. For example, species present at low concentration in liquids are commonly referred to as “additives” or “impurities,” whereas in the solid state they are described as “dopants” or “traps.” In both cases, however, such species perturb ion motion through the matrix under applied potential, modifying transport (i.e., diffusion) as well as the kinetics and thermodynamics of chemical reactivity and interfacial charge transfer (i.e., stability/reversibility).
This talk will detail efforts to understand and design ion coordination in order to modify the means by which ion transport takes place in the bulk of liquid and solid-state electrolytes, as well as to control the efficiency with which ion transfer takes place across liquid-solid and solid-solid interfaces. Specific examples will be given for Mg2+ and Zn2+-based electrolytes, where it has been shown that anion-cation association strength serves as a descriptor for reversibility of metal plating/stripping, and that intentional modification of anion-cation coordination chemistry in electrolytes with multiple anions can yield emergent solvation structures that would not otherwise form in single anion systems. These phenomena result in significant impacts on electrochemical response, as well as point to a new framework for enabling computationally-guided design of new electrolytes with enhanced performance. Similarly in the solid state, control over bulk and interfacial chemistry is shown to dictate the (electro)chemical stability of solid electrolyte materials, as well as to provide a means for designing enhanced processability and new functionality by surface modification of precursor materials. The phenomena elaborated in this talk are relevant to materials systems well beyond energy storage, and applications for these concepts in emerging areas such as decarbonized manufacturing, critical materials recovery and microelectronics will also be discussed.