UCLA

Electrochemical energy conversion and storage is critical for advancing vehicle electrification and sustainability of essential commodity chemicals. In pursuit of these goals, I delved progressively deeper into the foundational research of batteries and beyond: (1) pioneering novel methodologies to fundamentally understand lithium (Li) metal deposition, (2) regulating electrolyte decomposition to enhance Li metal batteries (LMBs) performance, and (3) expanding the technology’s applicability to make impact beyond batteries.

I have revealed the intrinsic morphology of electrodeposited Li metal to be a non-dendritic rhombic dodecahedron, which defies conventional expectations yet aligns with the theoretical prediction. Li deposition is a process in which Li-ions are reduced to metallic form at the electrode, which plays a crucial role for LMBs, because the reversibility of deposition morphology directly determines the cycling performance and safety of the battery. However, the simultaneous formation of a surface corrosion film termed the solid electrolyte interphase (SEI) complicates the deposition process, which underpins our poor understanding of Li metal electrodeposition. I creatively integrated the classical electrochemical method, ultramicroelectrode geometry, and an emerging electron microscopy technique, cryogenic electron microscopy (cryo-EM), to decouple Li deposition from the SEI growth and capture the corresponding nanostructure of Li. This discovery has significant implications for LMBs, as it suggests SEI influence can be effectively mitigated to achieve desired deposition morphologies. Besides enhancing our understanding of Li deposition, this work opens new opportunities to explore how reactive metal deposition fundamentally proceeds without the influence of corrosion film, thereby regulating reversibility of metal deposition to optimize the performance of metal batteries.

In addition to deposition morphology, the properties of the SEI also influence the performance of LMBs, as the SEI governs the transportation of Li-ion during cycling. Since the SEI formation results from electrolyte decomposition influenced by electric fields, I systematically examined effects of both electrolyte decomposition and electric fields on SEI formation, progressing from the bulk electrolyte to the electrode surface. I worked with colleagues to quantify reactions driving SEI formation and to determine the decomposition rates of individual electrolyte components, which guided our efforts to design and regulate their decomposition. Furthermore, I emphasized the importance of electric field to further fine-tune the formation of favorable SEI to improve battery performance.

Looking beyond applications of Li metal in batteries, I worked with collaborators to leverage the wealth of battery knowledge and established strategies to investigate fundamental aspects of Li metal as electrocatalyst in electrifying ammonia synthesis to help decarbonize the traditional chemical industry. We revealed key driver behind surface phenomena is the rupture of the SEI, enabling nitrogen and electrolyte to penetrate and react with Li metal to make ammonia. The insights from this work expanded our perspective of how Li metal electrodeposition can decarbonize chemical synthesis and inform our future efforts in designing better LMBs as well.