Metal‐CO ₂ Battery Electrolytes: Recent Developments, Strategies for Optimization, and Perspectives

ABSTRACT The environmental issues caused by carbon dioxide (CO 2 ), a major greenhouse gas, have garnered increasing attention, driving the widespread application of electrocatalytic CO 2 reduction reactions (eCO 2 RR) in pollutant treatment. Metal‐CO 2 batteries (MCBs) have emerged as a promising alternative to conventional fuel cells, garnering significant interest due to their capacity to integrate energy storage with eCO 2 RR. The electrolyte is of pivotal significance in MCBs, given its considerable impact on battery performance, service life, and safety. However, due to the inherent limitations of conventional electrolytes, such as flammability, thermal instability, poor low‐temperature performance, side reactions, achieving simultaneous optimization of all required performance parameters remains a formidable scientific challenge. Electrolytes should simultaneously possess high ionic conductivity, substantial CO 2 solubility, broad electrochemical stability window, and thermodynamically robust interfaces with the electrode materials to ensure overall system performance and stability. It is fortunate that a range of methodologies have been established for the purpose of modifying electrolytes. In this review, we provide a concise overview of the structural characteristics of conventional MCBs, systematically classify MCBs electrolytes into liquid, solid‐state, and semi‐solid‐state categories, and highlight the unique advantages and challenges. We further explore key optimization strategies like bulk composition tuning and additive engineering to enhance performance and put forward several suggestions for the future development of MCBs electrolytes according to persistent challenges. The findings of this study can provide valuable insights for the development of MCBs.