(334e) Lowering the Charge Overpotentials in Li-O2 Battery By Tailoring the Oxygen Reduction and Evolution Reaction Energetics Using Non-Precious Metal Oxide Electrocatalysts

Lithium-oxygen (Li-O₂) batteries are considered as the next generation energy storage technology with vast potential to contribute to electrification of the transportation sector. Although these systems are promising, several factors have resulted in performance far below the theoretical potential, including sluggish oxygen evolution reaction (OER) kinetics leading to high overpotential losses during charging.¹ We report a decrease in these overpotential losses achieved by perturbing the energetics associated with oxygen reduction reaction (ORR) and OER in aprotic Li-O₂ cathodes containing non-stoichiometric mixed metal oxide electrocatalysts with mixed electronic and ionic conducting properties.^2-3 A combination of well controlled synthesis, electrochemical studies and detailed characterization by Raman spectroscopy, titration, and differential electrochemical mass spectrometry show that these non-stoichiometric mixed metal oxide nanostructures change the energetics associated with ORR as compared to carbon-only electrodes by stabilizing Li-deficient intermediate species (> 50% more LiO₂ is detected in the presence of the catalyst), which consequently leads to lower OER overpotentials during charge. In addition, the presence of the catalyst also reduces the charge overpotential losses by lowering the potential required to dissociate Li₂O₂ during charge. These insights are key in providing new avenues for improving the efficiency of Li-O₂ batteries via tailoring the ORR/OER energetics using well-defined nanostructured, non-precious metal oxide electrocatalysts.

References:

(1) Lu, J.; Li, L.; Park, J. B.; Sun, Y. K.; Wu, F.; Amine, K., Aprotic and Aqueous Li-O₂ Batteries. Chem. Rev. 2014, 114, 5611-5640.

(2) Gu, X.-K.; Samira, S.; Nikolla, E., Oxygen Sponges for Electrocatalysis: Oxygen Reduction/Evolution on Non-stoichiometric, Mixed Metal Oxides. Chem. Mater. 2018, DOI:10.1021/acs.chemmater.8b00694.

(3) Nacy, A.; Ma, X. F.; Nikolla, E., Nanostructured Nickelate Oxides as Efficient and Stable Cathode Electrocatalysts for Li-O-2 Batteries. Top. Catal. 2015, 58, 513-521.