The role of Ni substitution in manganite perovskite Li-O2 battery

Abstract

A fundamental understanding of the electrochemical processes in Li-O2 batteries is critical for the further development and commercialization of Li-O2 and air-breathing battery technology. This study explores the electrochemistry of nickel-substituted manganite perovskites, La0.7Sr0.3Mn1−xNixO3 (x = 0, 0.1, 0.3, 0.5), which were subsequently used as catalysts in Li-O2 battery operating in 1 mol dm−3 bis trifluoromethane sulfonimide lithium salt (LiTFSi) in tetra ethylene glycol dimethyl ether (TEGDME) electrolyte. In situ Raman spectroscopy fingerprints on the discharge products correlated with charge-discharge profiles revealed that the electrochemical reaction pathway involves the formation of superoxide (LiO2) followed by reduction to lithium peroxide (Li2O2) during the battery discharge and corresponding two-step oxidation process in the charge phase. The superoxide (LiO2) was exceptionally stable for more than 2 h, which is in contrast to previous studies and expectations for short-lifetime intermediate formations. Electrochemical analysis revealed a significant improvement in the Li-O2 battery performance for oxygen electrodes substituted with 10% of nickel, reaching a specific capacity of 3554 mAh g−1. Substitution of Mn with Ni in La0.7Sr0.3Mn0.9Ni0.1O3 led to enhanced charge transfer kinetics due to a high surface population of the low valence state of B-site ions (Mn3+/Mn4+ ratio) accommodating the presence of eg1 electrons in line with Jahn-Teller disordered metal-oxygen octahedra effect. The current finding offers new insights for designing of aprotic LiO2 batteries.