(201e) Multi-Faceted Roles of Lithium Metal in Batteries and Electrocatalysis

Electrodeposition of lithium (Li) metal is critical for high-energy batteries. 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. Here we decouple these two intertwined processes by outpacing SEI formation at ultrafast deposition current densities while also avoiding mass transport limitations. By using cryogenic electron microscopy, we discover the intrinsic deposition morphology of metallic Li to be that of a rhombic dodecahedron, which is surprisingly independent of electrolyte chemistry or current collector substrate. In a coin cell architecture, these rhombic dodecahedra exhibit near point-contact connectivity with the current collector, which can accelerate inactive Li formation. We propose a pulse-current protocol that overcomes this failure mode by leveraging Li rhombic dodecahedra as nucleation seeds, enabling the subsequent growth of dense Li that improves battery performance compared with a baseline. While Li deposition and SEI formation have always been tightly linked in past studies, our experimental approach enables new opportunities to fundamentally understand these processes decoupled from each other and bring about new insights to engineer better batteries.

Looking beyond applications of Li metal in batteries, we leveraged wealth of our 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 emphasized the influence of SEI on nitrogen reduction processes that has frequently been overlooked by electrocatalysis community. We revealed that key driver behind surface phenomena is the proton donor which can disrupt SEI passivation, facilitating the reactions between nitrogen and electrolyte with Li metal to make ammonia. The insights from this work expanded our perspective of multiple ways in which Li metal electrodeposition can decarbonize chemical synthesis and inform our future efforts in designing better Li metal batteries as well.