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

The advancement and commercialization of Li-O₂ and air-breathing battery technology depend heavily on understanding the electrochemical processes in Li-O₂ batteries. In this work, we investigate the electrochemistry of nickel-substituted manganite perovskites, La₀.₇Sr₀.₃Mn₁₋ₓNiₓO₃ (x = 0, 0.1, 0.3, and 0.5). These perovskites are used as catalysts in Li-O₂ batteries operating in 1 mol dm⁻³ bis(trifluoromethane)sulfonimide lithium salt in tetraethylene glycol dimethyl ether electrolyte. The reaction pathway involves the formation of superoxide (LiO₂) during discharge, which is then reduced to lithium peroxide (Li₂O₂). The corresponding two-step oxidation process occurs in the charge phase. In situ Raman spectroscopy of discharge products provides evidence for these findings and correlates with discharge-charge profiles.In contrast to earlier research and predictions for short-lived intermediate forms, the superoxide (LiO₂) proved remarkably stable for longer than two hours. When oxygen electrodes were substituted with 10% nickel, the electrochemical studies showed a notable improvement in Li-O₂ battery performance, with a specific capacity of 3554 mAh g⁻¹. The substitution of Mn with Ni in La₀.₇Sr₀.₃Mn₀.₉Ni₀.₃O₃ resulted in increased charge transfer kinetics as a result of the high surface population of the low valence state B-site ions (Mn³⁺/Mn⁴⁺ ratio), which accommodates the presence of eg1 electrons in accordance with the Jahn-Teller disordered metal-oxygen octahedra effect. The current results provide a new understanding of the construction of aprotic Li-O₂ batteries.