There is a critical need for improved energy storage technologies for electric vehicles and large-scale integration of renewable electricity grid storage to improve domestic energy security. Currently, state-of-the-art energy storage technologies such as lithium ion batteries are insufficient in providing the performance requirements needed such as cost and energy density to enable broad use. Battery chemistries using high energy density electrodes could provide an avenue towards gains in energy density and durability for these applications. This project addresses the use of lithium-sulfur batteries as a potential high energy density and lower cost option. The major constraint of lithium-sulfur batteries is their poor cycling stability, namely the energy decay upon repeated use. One cause for this decay is reaction intermediates called lithium polysulfides, which dissolve and migrate in the battery electrolyte causing loss in active material. This project addresses the issue with a combined experimental and theoretical approach to develop new materials that can not only confine lithium polysulfides, but also accelerate their conversion to store or release energy. These materials have the potential to extend the life time of lithium-sulfur batteries without compromising their energy density. The project also conducts outreach through the Yale University Pathways to Science Program involving pre-college students in middle school and high school. The investigators will enable a new outreach activity under this program for a summer workshop involving battery topics.
This is a fundamental engineering project that addresses the cycle life challenge facing lithium-sulfur batteries by rationally designing high-performance sulfur electrodes based on molecular-level understanding of the chemical interactions and enabling electrocatalysis at the electrode/polysulfide interface. The chemical binding mechanisms as well as the electrochemical redox behaviors of lithium polysulfides are studied both experimentally and computationally with distinct model material systems comprising inorganic nanoparticles and metal complexes with well-controlled and systematically-varied structures. Suitable sites that can effectively bind lithium polysulfides and catalyze their electrochemical conversion reactions will be identified. Reaction pathways, energy barriers and rate-limiting steps will be calculated and experimentally examined. Based on the new knowledge, ternary-structured materials and ultrathin protection layers will be designed and synthesized to enable high-capacity and long-cycle sulfur electrodes operating under application-relevant conditions.
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.
