Solid Electrolyte Interphase and Interface Effect on the Nucleation of Lithium Pitting

The nucleation of pits and their evolution on the lithium (Li) metal anode greatly impact the cyclability and safety of Li-metal batteries. Overpotential has been found to be inversely related to the Li pit radius and exponentially related to the nucleation rate. However, it remains unclear how the electrode/electrolyte interphase and interface impact the nucleation of pitting. In this study, we decouple the electrolyte effect into a solid electrolyte interphase (SEI) and interface charge transfer (CT). Under galvanostatic stripping, ether electrolytes yield larger and sparser pits than the carbonate electrolyte, which is related to the lower stripping overpotential of ether electrolytes. Under potentiostatic stripping, a smaller pit size and higher nucleation density have been revealed in ether electrolytes due to the higher nucleation rate. We found that charge-transfer kinetics on the interface of the Li-metal anode will greatly influence its nucleation mode and kinetics. Slow charge-transfer kinetics in the carbonate electrolyte lead to a lower nucleation rate and larger Li pits, which are close to 3D nucleation. In ether electrolytes with fast charge transfer kinetics, the pitting process exhibits 2D nucleation. The SEI derived from various electrolytes mainly influences the stripping overpotential and the morphology of the pits. By clarifying the roles of SEI and interfacial charge transfer on the nucleation of pitting, this work will greatly benefit the design of cycling profiles and electrolyte recipes for next-generation Li-metal batteries.