In recent times, the Li‐CO2 battery has gained significant importance arising from its higher gravimetric energy density (1876 Wh kg‐1) compared to the conventional Li‐ion batteries. Also, its ability to utilize the greenhouse gas CO2 to operate an energy storage system and the prospective utilization on extraterrestrial planets such as Mars motivate to practicalize it. However, it suffers from numerous challenges such as (i) the reluctant CO2 reduction/evolution; (ii) solid/liquid/gas interface blockage arising from the deposition of Li2CO3 discharge product on the cathode; (iii) high overpotential to decompose the stable discharge product Li2CO3; and (iv) instability of the electrolytes. Numerous efforts have been undertaken to tackle these challenges by developing catalysts, improving the stability of electrolytes, protecting the anode, etc. Despite these efforts, due to the lack of a decisive confirmation of the reaction mechanisms of the discharging/charging reactions occurring in the system, the progress of the Li–CO2 battery system has been slow. In situ characterization techniques help overcome ex‐situ techniques’ limitations by monitoring the processes with the progress of a reaction. The current review focuses on bridging the gap in the understanding of the Li–CO2 batteries by exploring the various in situ/operando characterization techniques that have been employed.

Increased CO 2 emissions on the earth causing global warming and climate change have provided a thrust to explore Li−CO 2 battery chemistry, where CO 2 is used as an energy carrier. In addition, the occurrence of CO 2 as a major natural abundant gas in the Martian atmosphere opens the possibility of using Li−CO 2 batteries for interplanetary Mars missions. In this work, we aim to investigate facile and inexpensive candle soot carbon nanoparticles as a cathode catalyst against commercially available multiwalled carbon nanotubes (MWCNTs) for stable and high-performance Li−CO 2 batteries for Mars exploration. The unique interconnected morphology and higher surface area of candle soot nanoparticles facilitate better reversibility (more than 80 cycles) compared to MWCNTs even at a high current density of 200 mA g −1 with a cutoff capacity of 500 mAh g −1 . The full discharge capacity for candle soot nanoparticles was measured to be 5318 mAh g −1 with a coulombic efficiency of 42% as compared to 16% for MWCNTs. The rate capability studies were performed to establish the ability to operate the system reversibly at different current densities in a simulated Martian atmosphere. The outcome of this study paves the way toward developing a candle soot cathodebased practicable Li−CO 2 battery for utilization on Mars.