锂-空气电池是发展先进储能系统中的重要电池体系, 具有极高比能量. 然而, 锂-空气电池在正极侧仍面临着电极动力学缓慢、过电位高和电解液分解副反应等问题. 为克服上述问题, 研究者引入多种催化策略, 其中氧化还原媒介体分子催化剂的出现解决了“固-固”界面接触问题, 可有效地提高锂-空气电池的电化学性能. 聚焦于锂-空气电池的研究现状和关键挑战, 系统阐述了该体系中媒介体催化的作用机制及其应用, 进一步探讨了理想媒介体的设计要点与技术难点, 最后对该领域提出了展望.

Lithium-air batteries are considered promising candidates for the development of advanced energy storage systems due to their exceptionally high theoretical energy densities. Taking lithium-oxygen batteries as an example, their theoretical specific energy can reach up to 3500 Wh/kg. However, lithium-air batteries, including lithium-oxygen and lithium-carbon dioxide batteries, still face significant challenges on the cathode side, such as sluggish reaction kinetics, high overpotentials, and side reactions caused by electrolyte decomposition. During discharge, gaseous reactants such as O₂ or CO₂ are reduced at the cathode to form solid discharge products like peroxides, carbonates, or oxalates. These products typically possess poor electronic and ionic conductivity, which can passivate the electrode surface, leading to catalyst deactivation and capacity limitations. In the subsequent charging process, the poor “solid-solid” contact between the catalyst and these insulating discharge products makes them difficult to decompose efficiently, resulting in high overpotentials, low coulombic efficiency, and severe parasitic reactions. To address these issues, researchers have introduced redox mediator (RM) molecular catalysts to convert the “solid-solid” interface into a more efficient “solid-liquid-solid” interface. RMs transfer electrons between the electrode and the discharge products in solution phase, enabling their oxidation and fully decomposition, thereby improving the poor contact of “solid-solid” interface and significantly improving the electrochemical performance of lithium-air batteries. This review briefly introduces the current status and key challenges in lithium-air battery research and, using lithium-oxygen batteries as a representative system, systematically discusses the catalytic roles, mechanisms, and advantages and disadvantages of redox mediators during both discharge and charge processes. Furthermore, the design principles and technical barriers in developing ideal redox mediator catalysts are analyzed, and future perspectives for this research field are proposed.