Candle Soot Nanoparticles versus Multiwalled Carbon Nanotubes as a High-Performance Cathode Catalyst for Li–CO_2Mars Batteries for Mars Exploration

Increased CO2 emissions on the earth causing global warming and climate change have provided a thrust to explore Li–CO2 battery chemistry, where CO2 is used as an energy carrier. In addition, the occurrence of CO2 as a major natural abundant gas in the Martian atmosphere opens the possibility of using Li–CO2 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–CO2 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 cathode-based practicable Li–CO2 battery for utilization on Mars.