Lithium metal anode surface chemistry. Lithium metal is one of the most reactive elements on the periodic table. As soon as it comes in contact with the electrolyte, the solvent and salt start to decompose. Those electrolyte decomposition products precipitate onto the lithium surface, forming the solid electrolyte interphase (SEI). For an electrode material like lithium that relies on electrodeposition and dissolution rather than intercalation (like graphite), the large volume changes demand additional mechanical requirements from the SEI, in addition to being ionically conductive and electronically insulating. We are interested in understanding how electrolyte engineering can be leveraged to tune the compositional architecture of the SEI, interfacial lithium-ion transport, lithium deposition morphology, and lithium loss pathways.
Electrolyte oxidation reactions in cobalt-free batteries. Cobalt-containing cathodes in lithium-ion batteries present major geopolitical and ethical concerns. As a result, it must be eliminated from energy storage systems. However, high energy cathodes that contain little to no cobalt exhibit severe interfacial and thermal instabilities. We have developed novel operando NMR and EPR tools to monitor cathode-driven degradation reactions that occur during battery operation to provide fresh insight into how we might prevent these processes from happening. These measurements are often coupled with synchrotron-based X-ray imaging experiments to understand how deleterious reaction byproducts impact the electrochemical properties of composite electrodes.
Interface and electrolyte design principles for beyond lithium batteries. At present, we do not know if the decades of research dedicated to improving lithium-ion battery performance through electrolyte engineering is transferable to more earth abundant chemistries. In our lab, we have shown that canonical additives used to enhance the performance of lithium-ion batteries actually have the opposite effect in potassium-ion systems. Further, the resulting SEI components were also found to be detrimental to potassium transport, but are often touted as beneficial for lithium. Insight from these results suggests that electrolyte decomposition pathways and desirable SEI compounds in beyond-lithium systems differ from traditional lithium-ion batteries, indicating that entirely new approaches to electrolyte engineering are needed.