John Kieffer


2018 HH Dow

T: (734) 763-2595








Optimizing Ion Mobility, Chemical Stability, and Mechanical Rigidity In Composite Electrolytes

Sponsor: National Science Foundation
The three principal performance characteristics of Li-ion battery electrolytes are: (i) selectively high Li+ conductivity, i.e., with a transference number close to unity, providing adequate power density for the device; (ii) high mechanical stiffness to suppress dendrite growth during charging phases; and (iii) chemical compatibility with the electrodes to prevent unwanted redox reactions and electrode passivation. In particular, the first two properties tend to vary oppositely as the structural characteristics of electrolyte materials are modified. Materials design therefore requires a composite approach and the ability to accurately predict the optimal combination of constituents, i.e., providing the best balance of performance characteristics. One goal of this project is to establish this predictive capability, which combines molecular simulation, materials synthesis, and characterization of structure, conductivity, and nano-mechanics, to identify the optimal design criteria for solid electrolytes. Our experimental design is directed towards identifying the fundamental principles that underlie materials design for effective solid-state ion transport. To clearly and unequivocally identify these design principles and resulting conduction mechanisms, we pursue highly controlled and systematic experimentation that allows us to identify the effect of molecular and meso-scale structure on the conduction mechanisms, and to quantitatively assess the efficacy of molecular functionalization. Our goal is to determine the knowledge base that allows us to estimate the theoretical limits of ion conduction, i.e., the highest conductivity that can be achieved in a best-case-scenario material. Accordingly, we implement all design features sequentially, so that we are able to clearly assess their respective influences on the aforementioned electrolyte performance characteristics.