Manganese Oxide Catalysts for Lithium–Oxygen Batteries: Structures, Mechanisms, and Reaction Pathway Engineering

The growing demand for high-specific-energy storage has revived interest in lithium-oxygen batteries (LOBs), whose theoretical energy density far exceeds that of conventional lithium-ion battery systems. However, their practical use is limited by sluggish reaction kinetics, parasitic reactions, high overpotentials, and the buildup of insulating lithium peroxide, all of which hinder reversibility and cycling stability. Manganese oxides (MnO_x) have emerged as promising cathode catalysts because of their abundance, low cost, tunable oxidation states, and diverse structural features. Their tunnel, layered, and spinel architecture provide adaptable environments for O₂ reduction and evolution, Li⁺ transport, and the conversion of reaction intermediates. Recent progress demonstrates that structural engineering of MnO_x, through pore-structure tuning, surface-site modulation, defect introduction, heteroatom doping, and composite fabrication, can significantly optimize lithium peroxide formation and decomposition. These strategies regulate catalyst electronic structures and reaction pathways, thereby influencing Li₂O₂ formation/decomposition behavior, reducing side reactions, lowering polarization, and enhancing catalytic activity. This review summarizes recent advances in MnO_x-based catalysts for non-aqueous LOBs, emphasizing structure-activity relationships and mechanistic understanding. By outlining remaining challenges and key design guidelines, we aim to support the rational development of next-generation catalysts for practical LOB deployment.