The role of Ni substitution in manganite perovskite Li–O2 battery†

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, La_0.7Sr_0.3Mn_1−xNi_xO₃ (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 La_0.7Sr_0.3Mn_0.9Ni_0.1O₃ 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 e_g¹ electrons in line with Jahn–Teller disordered metal–oxygen octahedra effect. The current finding offers new insights for designing of aprotic LiO₂ batteries.