Nonprecious Metal Catalysts for Tuning Discharge Product Distribution at Solid-Solid Interfaces of Aprotic Li-O2 Batteries

Tuning catalysis at solid-solid interfaces is critical for the development of next-generation energy storage devices such as Li-O-2 batteries, where solid lithium-oxygen species are formed and dissociated on a solid catalyst. Herein, atomically controlled synthesis is combined with theoretical calculations, electrochemical studies, and detailed characterization measurements to show that the interface between an oxide catalyst and the solid products is key to selectively control discharge product distribution, consequently affecting charge overpotentials. A surface structure-dependent electrochemical performance for nonprecious metal-containing, nanostructured lanthanum nickelate oxide (La2NiO4+delta, LNO) electrocatalysts is demonstrated. LNO nanostructures with (001) NiO-terminated surfaces exhibit lower charge overpotentials, as opposed to irregularly terminated polyhedral-shaped oxides of the same composition. It is found that these LNO nanostructures, with controlled surface structure, enhance the performance by providing a platform for stabilization of Lideficient oxide species during discharge, consequently lowering overpotential losses associated with their oxidation during charge. Periodic density functional theory modeling of the solid-solid interface between the oxide catalyst and the lithiumdischarge products suggests that stabilization of the Li-deficient products is due to the formation of a lithiated oxide surface, which is in turn facilitated by an electron transfer from the near surface Li to the surface lattice oxygen atoms. The potential-dependent stability of these lithium-oxygen species on LNO is predicted and confirmed experimentally. These results provide a framework for probing and engineering catalysis at solid-solid interfaces, and strategies for improving the efficiency of nextgeneration energy storage systems using nonprecious, nanostructured mixed metal oxide catalysts.