Collaborative Research: Understanding the discharge mechanism at solid/aprotic interfaces of Na-O2 battery cathodes to enhance cell cyclability

Dr. Eranda Nikolla of the University of Michigan and Dr. Jeffrey Greeley of Purdue University will study the chemistry and deactivation mechanisms at solid-aprotic electrolyte interfaces in order to advance the development of next-generation energy storage devices, such as sodium-oxygen (Na-O2) batteries. Although Na-O2 batteries are promising, limited long-term stability, and lack of fundamental, molecular-level understanding of the mechanisms that govern durability, have impeded progress. The PIs seek to address this challenge by combining experimental and theoretical studies. The insights from the work will lead to a general framework that can guide the design of the cathode/electrolyte interfaces to enable stable cycling of discharge products for Na-O2 batteries. Also, the PIs will partner with local K-12 students in the Metro Detroit area and West Lafayette, IN to involve economically disadvantaged students in summer research internships and student research exchanges. Aprotic Na-O2 batteries have gained significant attention as viable alternatives to commercial Li-ion batteries. Owing to their high theoretical energy densities and reversible redox chemistries, Na-O2 batteries offer opportunities to achieve high discharge capacities and low charge overpotentials by controlling the nature of discharged products at the cathode. While this technology is very attractive, maintaining stability of Na-O2 batteries is a significant challenge. In the present project, PIs Nikolla and Greeley seek to alleviate this issue by developing a combined experimental/theoretical approach to advance understanding of the deactivation mechanisms of Na-O2 cells driven by changes at the cathode/electrolyte interface, with the goal of improving cell cyclability. The research plan will involve: (i) determining the factors that govern deactivation and byproduct formation, both as a function of electrochemical potential and under resting conditions (no applied current), in Na-O2 batteries, (ii) elucidating the effect of incorporating oxide electrocatalysts to tune the product formation at the cathode of Na-O2 battery cells, so as to minimize cell deactivation, and (iii) developing a general framework to guide the design of cathode/electrolyte interfaces that result in stable cycling of Na-O2 batteries. 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.