Advances in selectively tuning the electrochemistry at the solid-solid interfaces of alkali metal-O2 batteries remains central toward engineering the next generation energy storage systems. Among these systems, Li-O2 batteries provide the highest energy density making them attractive for electrification of the transportation sector. These regenerative systems rely on the reversible redox chemistry of metallic Li and O2 in aprotic solvents, where oxygen is reduced (ORR) at the cathode during discharge to form of solid lithium-oxide species (xLi+ + O2 (g) + xe– ↔ LixO2 (s); x=1 or 2). During the charge cycle, the formed solid LixO2 species are oxidized, leading to the evolution of oxygen (OER). The complexity of the electrochemical transformations at the battery cathode where solid LixO2 species are formed and dissociated has been a challenge in achieving the desired theoretical capacities. Therefore, development of an understanding of the mechanism and the factors that govern solid LixO2 product formation at the solid cathode electrocatalyst surface remains crucial toward devising strategies in advancing the battery performance. In this contribution, (i) atomically controlled synthesis, (ii) detailed electrochemical and characterization studies, and (iii) periodic density functional theory (DFT) calculations are combined to demonstrate the importance of controlling the surface structure of the catalyst in tailoring discharge product formation at the Li-O2 battery cathode. We find that nanostructured nonstoichiometric mixed metal oxide cathode electrocatalysts (i.e., La2NiO4+δ) provide a platform to stabilize Li-deficient oxide (LixO2) species during discharge, leading to a lowering of the overpotential losses associated with their oxidation during charge. Atomistic modeling of the solid-solid interface between the oxide electrocatalyst and LixO2 discharge products using DFT suggests that the stabilization of Li-deficient products is due to formation of a Li-modified oxide surface with high electronic conductivity resulting in enhanced overall performance. These findings are important toward designing effective approaches for enhancing the efficiency and cyclability of Li-O2 batteries.

Tailoring the discharge product distribution through electrocatalyst design at solid-solid interfaces of Li-O2 batteries

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