Fundamental Understanding and Material Challenges in Rechargeable Nonaqueous Li–O2 Batteries: Recent Progress and Perspective

Energy storage challenges have triggered growing interest in various battery technologies and electrocatalysis. As a particularly promising variety, the Li-O-2 battery with an extremely high energy density is of great significance, offering tremendous opportunities to improve cell performance via understanding catalytic mechanisms and the exploration of new materials. Furthermore, focus on nonaqueous electrolyte-based Li-O-2 batteries has markedly intensified since there could be a higher probability of commercialization, compared to that of solid-state or aqueous electrolytes. The recent advancements of the nonaqueous Li-O-2 battery in terms of fundamental understanding and material challenges, including electrolyte stability, water effect, and noncarbon cathode materials are summarized in this review. Further, the current status of water impact on discharge products, possible mechanisms, and parasitic reactions in nonaqueous electrolytes are reviewed for the first time. The key challenges of noncarbon oxygen electrode materials, such as noble metals and metal oxides-based cathodes, transition metals, transition metal compounds (carbides, oxides) based cathodes as well as noncarbon supported catalysts are discussed. This review concludes with a perspective on future research directions for nonaqueous Li-O-2 batteries.