Proximity Matters: Interfacial Solvation Dictates Solid Electrolyte Interphase Composition

Thecomposition of the solid electrolyte interphase (SEI) playsan important role in controlling Li-electrolyte reactions,but the underlying cause of SEI composition differences between electrolytesremains unclear. Many studies correlate SEI composition with the bulksolvation of Li ions in the electrolyte, but this correlation doesnot fully capture the interfacial phenomenon of SEI formation. Here,we provide a direct connection between SEI composition and Li-ionsolvation by forming SEIs using polar substrates that modify interfacialsolvation structures. We circumvent the deposition of Li metal byforming the SEI above Li+/Li redox potential. Using theory,we show that an increase in the probability density of anions neara polar substrate increases anion incorporation within the SEI, providinga direct correlation between interfacial solvation and SEI composition.Finally, we use this concept to form stable anion-rich SEIs, resultingin high performance lithium metal batteries.

Automated summary

The composition of solid electrolyte interphase (SEI) is crucial for controlling Li-electrolyte reactions, but the reason for SEI composition differences between electrolytes is still unclear. Although many studies correlate SEI composition with Li ion solvation in the electrolyte, this correlation does not fully explain the interfacial phenomenon of SEI formation. In this study, we establish a direct connection between SEI composition and Li-ion solvation by creating SEIs using polar substrates that modify interfacial solvation structures. We demonstrate that an increase in the probability density of anions near a polar substrate enhances anion incorporation within the SEI, which directly correlates with interfacial solvation and SEI composition. Finally, we apply this concept to create stable anion-rich SEIs, leading to high-performance lithium metal batteries.