Atomic Structure of the Lithium–Lithium Oxide Interface from First Principles

While lithium-ion batteries (LIBs) have been largely commercialized as the rechargeable battery of choice, their liquid electrolyte limits the theoretical energy density of the battery and poses serious safety threats. Solid-state lithium batteries (SSLBs) use a solid electrolyte, which can provide much higher energy densities and better safety than LIBs. The adoption of SSLBs is held back by interactions that occur between the electrolyte and anode, such as high resistance to lithium (Li) ion flow and the growth of Li dendrites that lead to short circuits. This paper focuses on understanding the interface between oxide electrolytes and Li metal anodes with the goal of predicting the structure and properties dictated by the interface. By comparing interface energies for different orientations of Li and lithium oxide (Li₂O), a primary component of the solid electrolyte interphase, the Li₂O(110) surface was found to be the most energetically favorable. Furthermore, bonding between the metallic Li and the oxygen atoms on the Li₂O(110) plane was observed to be more impactful on stability than the lattice strain. As a consequence, the lowest energy interface was obtained by introducing FCC Li between Li₂O and BCC Li.