A comprehensive overview of the electrochemical mechanisms in emerging alkali metal–carbon dioxide batteries

Abstract Alkali metal–carbon dioxide (Li/Na/K‐CO2) batteries are emerging electrochemical energy storage technologies in the context of the energy crisis and the urgent demand for carbon neutrality. Alkali metal–CO2 batteries offer a new strategy for CO2 fixation and utilization, and thus has been receiving considerable attention in recent years. Considerable progress has been achieved since alkali metal–CO2 batteries were invented, especially in terms of development of new electrode materials, and yet, research is lacking on the underlying mechanisms of the systems. This is the first typical review focusing on the electrochemical mechanisms of metal–CO2 batteries that summarizes the current understanding of and provides insights into the thermodynamic reaction pathways, the kinetic characteristics, and the crucial factors determining the reaction mechanisms in alkali metal–CO2 batteries. The review starts with the fundamental concepts of alkali metal–CO2 batteries, followed by a comprehensive discussion of the working mechanisms on cathodes and anodes. Moreover, the operation mechanisms of state‐of‐the‐art electrolytes, including liquid and (quasi‐)solid‐state electrolytes, are also described. Finally, we identify the unsolved problems in current alkali metal–CO2 batteries and propose potential topics for future research.