A comprehensive review of carbon-based air cathode materials for advanced non-aqueous lithium-air batteries

Lithium-air batteries (LABs) present a promising solution for future energy storage due to their exceptional energy density and potential to address imminent energy and environmental challenges. The complicated generation and breakdown of Li2O2 at the air-cathode is the main cause of the durability and stability problems that LABs encounter. These problems are not merely related to low catalytic efficiency; instead, problems are made worse by restricted charge/discharge reversibility along with side-product generation in open-air. Furthermore, the function of solid-phase electrocatalysts is still controversial, particularly when Li2O2 generation is involved. This makes the hunt for efficient air-cathode materials more challenging. Since their inception in 1996, carbon has been crucial in advancing LAB technology, enhancing our understanding of its mechanisms and applications. This review examines advances in carbon materials and chemistry for LABs, focusing on structural characteristics, electrochemical behavior, and mechanistic insights. Air-cathode materials are categorized into carbon nanotubes (CNTs), carbon nanofibers (CNFs), graphene, bio-waste-derived carbons, and metal-organic frameworks (MOFs)-derived carbons. Additionally, the review evaluates the design, synthesis strategies, and electrochemical performance of these carbon-based air-cathode materials. It also explores oxygen-selective membranes (OSMs) as a potential solution to mitigate the adverse effects of H2O and CO2 in ambient air, which lead to the formation of Li2O2 and reactions with the electrolyte and Li anode in open-air systems. In conclusion, this review addresses the current challenges faced by LABs and highlights the potential for further research and development in this field.